The Wrong Kind of Ditching

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Those of us who fly or who are deeply involved in aviation probably don't think of airplanes as being dangerous of themselves. And they really aren't. But an incident over the weekend reveals a constant truth: Get careless around aircraft and they can bite badly, if not fatally.

Over the weekend, we had our annual airport open house at Venice. It's a public relations exercise to promote both the airport itself and aviation in general. As part of that event, we park a dozen or so airplanes in a small static display. I had the Cub tied down and I hung around for a while to answer questions and just generally be amiable. (Being basically anti-social, this I do with great difficulty, but I feel compelled to try.)

click for full-size image

About mid-morning, a Canada-registered transient Malibu showed up and shut down on the ramp. Sometime later—I'm not sure how much later, because I'd left the airport to run errands—the Malibu was observed to start up, throttle immediately to high power and dart across the ramp, a taxiway and into a ditch. A person was seen clinging to the wing in an apparent attempt to stop the aircraft. When the airplane hit the ditch—a drainage swale, actually—the nosegear was sheared off and the right main either collapsed or was also sheared off, causing the prop to dig into the turf and stop the engine. And that's the best thing that could have happened all day.

If the ditch hadn't been there, the airplane would have had a long expanse of open center field, taxiways and runways—more than enough to take off. Or, worse, across the field and in full swing was the annual Italian festival, with rides and food vendors and hundreds of people milling around on a closed taxiway. (You can see it in the distance in the photo.) There's a short fence between the airport and the taxiway that may or may not have stopped the airplane.

If the Malibu had been facing the opposite direction, which transients sometimes do, it would have plowed right into our static display, making yellow confetti of our little J-3. Worse, it could have also mowed down a lot of people not expecting to be chased by a Malibu run amok. Wouldn't have been too auspicious for our airport day, either.

What can we conclude here? The obvious takeaway is so obvious that need I even explain it? Speaking of explaining, I can, in a leap of generosity and self-delusion, allow as how when the pilot pulled the prop through, maybe the switches were off and the problem was really an open p-lead. Just as a refresher, you know that a magneto needs no external voltage and will generate spark if it's turned. The p-lead simply grounds the primary coil and keeps that from happening. When you switch off the mags, you close the p-lead to ground. If the lead has failed open, the mags are hot even with the switch off. It's always a good idea to do an occasional p-lead check by killing the engine with the mag switch, not the mixture. As I said, I'm being generous because I can't make the point without beating up someone who probably made a big mistake.

My generosity comes up short in explaining why the Malibu's throttle was in or near the full-open position. A couple of my colleagues tell me they know what full throttle sounds like and they heard full throttle. Moral: Don't turn a prop manually unless you expect and are prepared for the engine to start. And as far as the throttle…well, you know.

In sweeping accident reports, I read a couple of incidents every year in which an airplane being propped gets away from the propper. These usually bash into hangars, other airplanes or cars, but occasionally one gets airborne for a little non-autonomous random drone flying. I think of these every time I prop the Cub on my own, which is basically every time I fly it. Saturday's incident reminded me that I've been meaning to make a tail tiedown safety rope for the Cub and I've got that done. Given the way I prop, it's belt and suspenders. But better that than having my figurative pants around my ankles chasing a taildragger down the ramp and wondering what the hell went wrong.

Comments (106)

Paul now that I have graduated to an airplane with a battery and electric start (this new marvel could catch on we should invest)your j3 and others aside people really need to examine why they are hand propping. If you are in the bush sure but at an airport if the battery is dead you need to find out why. If the master was left on a proper charge is in order if the battery or alternator are bad repair or replace. To think that the alternator will adequately charge a dead battery under full load could lead to an even bigger failure while airborne.

Posted by: James Greig | February 28, 2013 5:20 AM    Report this comment

Wow! Must have been a big guy to hand prop a whole AIRLINE! :)

Posted by: John Peck | February 28, 2013 6:02 AM    Report this comment

"If the lead has failed open, the mags are hot even with the switch off." Never, never assume a prop is anything but hot! I have had the experience of an engine start when I was positioning the prop; the keys were in plain sight on top of the panel. The P-lead was broken. Always handle a prop expecting it will try to bite you.

Posted by: Richard Montague | February 28, 2013 7:41 AM    Report this comment

I've seen a cold weather starting technique that has a student at the controls feeding primer while the CFI pulls the prop through a full engine turn. Every time I see this I cringe. In addition, this particular flight school has banned the "turn the key off" P-lead check before shutdown because it was causing muffler failures, and it's a disaster waiting to happen.

Posted by: Jerry Plante | February 28, 2013 7:45 AM    Report this comment

When I first learned to fly it was in a J-3 Cub. Learning to handprop was a must. My old time instructor said "Treat it like a rattlesnake". Good advice and in years of hand propping I never experienced an accident. Wasn't bitten either.

Posted by: John Hruban | February 28, 2013 8:03 AM    Report this comment

Having read about, and seen colleagues having mishaps in respect to
hand propping airplanes to start, there could be three rules to keep us all safe!
1, only hand prop a tail dragger ( then if done correctly, swinging a leg
away from the propeller, you will actually step away from the very dangerous
2, never hand prop an airplane with more than 100HP! You could loose
a hand or limbs quickly in front of that kind of power!
3, the airplane should be chocked or tied down with a knowledgable
pilot inside at the controls!
The above rules then apply to all aircraft without electrical systems that
will have to be hand propped to get them started! As already mentioned
in previous comments, aircraft with electrical systems/starters should be
started using fresh or charged batteries and/or a ground power unit!
Bertil Aagesen

Posted by: Bertil Aagesen | February 28, 2013 8:30 AM    Report this comment

With new and even repeating passengers, I always brief them that no matter what, the prop is dangerous, whether it's running or stopped. Nobody gets in or out while it's turning; nobody gets near it except me to take the tow bar off or put it on; and for the obligatory pictures for their scrapbooks, everyone stands behind the wing and uses the side of the airplane as the backdrop.

I always cringe at the photos showing everyone around the prop, usually with someone leaning on it. In 40+ years of flying, I have not personally experienced an unexpected start, but I've hand-propped enough different airplanes (always with a qualified person at the controls) to know that it doesn't take a whole lot of prop movement most of the time to get a start.

For those who fear backfires and muffler damage by shutting off the mags to check the P-leads, just reduce the rpm to slowest idle, and there will be no backfire if the key is turned all the way off. But to further protect from backfiring, only shut off one mag at a time, just like during the run-up. Even at slow rpm, there will be enough of a mag drop to detect a faulty ground--and if there is no mag drop, the mag remains hot, and the prop is still dangerous.

Posted by: Cary Alburn | February 28, 2013 8:38 AM    Report this comment

Don't worry about "blowing out the mufflers." As Paul mentioned "Kill the engine with the mags" occasionally--don't turn them off and turn them back on. Most older airplanes (like Paul's Cub or my Cessna 120) don't have mixture controls--EVERY shutdown is accomplished by simply turning off the mags from a low idle--and leaving them off. Muffler damage? Doesn't happen.

Posted by: jim hanson | February 28, 2013 9:01 AM    Report this comment

I understand the danger of a broken P-lead, but engines won't start unless they're primed. If the last shutdown has the throttle closed and the mixture in cutoff, wouldn't it take an act of God for the engine to fire? Still, being cognizant of prop safety should be instilled (beaten?) into new pilots, and even some older ones.

Posted by: Will Alibrandi | February 28, 2013 9:45 AM    Report this comment

Here’s a peripherally-related comment: About 30 years ago, I added an item to the engine-run-up checklist. After the usual high-power mag and prop checks, retard the throttle to idle for the classic idle RMP and smoothness check. Then (quickly) select “mags off,” just to ensure that the engine(s) will die. Then re-select “both” (or turn both discrete switches back “on”). Done right, the procedure doesn’t require a re-start, and doesn’t produce any damage to the exhaust or induction apparatus. What it does do, is verify that – for this one moment, at least – the P-leads of all of your magnetos are working. Of course, students’ first question is “why should I care?” What follows is an explanation of various failure modes of magnetos – including ones in which you really wish that you could shut down an offending magneto, so that the other one could do its job without interference from the malfunctioning one. Yes – I have experienced that situation in flight. I’ve also experienced two unrelated magneto failures within just over one flight hour, in the same engine (One of the mags was nearly new; the other was a veteran. But neither exhibited any symptoms before giving up the ghost.) The lesson? When one mag fails in flight, find a place to land, as soon as you can do so safely. ‘Cause you just never know…

Posted by: Tom Yarsley | February 28, 2013 10:09 AM    Report this comment

Will, an engine shut down with the mixture and with the mix still in idle cutoff can very well start; it just won't continue running. We've all done this, I'm sure. Try a start with the mixture inadvertently in idle cutoff, have the engine fire and then die.

If you're on the business end of the prop, that brief firing is enough to kill or injure you. In some ways, the little Cub is safer because it won't shutoff if a p-lead is broken, so you know the mags are grounded. Or at leas they were the last time you ran the thing.

Posted by: Paul Bertorelli | February 28, 2013 10:22 AM    Report this comment

Note to all. Some insurance policies will not cover damage caused by an engine start when there is no licensed pilot at the controls. I say don't count on chocks, tie it down.

Posted by: GENNARO AVOLIO | February 28, 2013 11:02 AM    Report this comment

I had a C-152 that broke a p-lead in flight. I was a low time pilot and when the engine wouldn't shut down I was seriously flustered. I finally got enough presence of mind (and it felt like a long time before that happened) to shut it down with the mixture. I went back to my instructor and discussed his teaching techniques and then found a new instructor. What does that have to do with propping an engine? Not much, but that same aircraft had a habit of draining its' battery. No one could find why and I learned to prop it when a battery box wasn't available. I watched an "old-timer" (must have been all of fifty or so) propping a J-3 and he propped it from BEHIND the prop. He told me that if it started at least it wouldn't jump forward and get him, and it should bat his hand away rather than chopping it off. As he still had both hands it must have worked. I took that lesson to heart, along with both chocking AND tying down. (After my first trip to Oshkosh I had a collection of tie-down stakes and used them often. Seems like a lot of people just left them in the ground when they left the fly-in.) I never had another p-lead failure, but I always did the "belt and suspenders" procedure when I had to prop-start the C-152.

Posted by: Jerald Graham | February 28, 2013 1:55 PM    Report this comment

" would imagine a worn mag switch it is possible to remove the key while in both (apparently it happened)."

That same C-152's switch was so worn out that the key could be removed in any position, and many of the keys I carried every day (not aircraft related) would unlock the doors and start the aircraft. When I found out how much it would cost to replace the old locks and switch I gave up and got a proplock. Cheaper, and a visual deterrant to the thieves who steal entire aircraft. Didn't save the radios, though.

Posted by: Jerald Graham | February 28, 2013 3:24 PM    Report this comment

I read the posts, went flying an on the taxiback turned the mags off for a sec. Engine quit, so I switched mags on and 'kapow' barked the Cardinal. No problem, I've done it before, but not in the alley between facing rows of hangars. The airport security manager happened to be at the far end of the alleyway and apparently the echo made more noise than he thought a Cardinal should. Oopsie!

Posted by: Thomas Connor | February 28, 2013 3:33 PM    Report this comment

Why not just turn the mags off at the end of the flight to check for broken p-leads? Turn them off, and don't turn them back on. No problem.

Turning them off and back on again creates a problem, where one likely did not exist before.

Posted by: jim hanson | February 28, 2013 3:56 PM    Report this comment

Two incidents to relate:
1) In the mid-80s, a derelict Bonanza was being brought back to life in a maintenance and storage hangar here in Louisville. It hadn't run in at least five years. One mechanic was standing by the prop talking with another who was under the airplane. As a parting gesture, the mechanic by the prop flicked the tip of the prop as he was walking away. The engine roared to life for a couple seconds and then quit. The offending mechanic went on to be an FAA maintenance inspector.
2) In the summer of 1980, a pilot propped a Cessna 210 at Pirate's Cove airport on Kentucky Lake with no one at the controls. The airplane started, went down the runway and got airborne. It rolled left and hit trees and crashed.

Posted by: William Kight | February 28, 2013 8:03 PM    Report this comment

I was instructed to shut down with the mixture to make sure fuel was cleared from the spider to the injectors and cylinders. That's the way most do it, but that doesn't make it the best.

What I'm getting from this discussion is that its better to shut down with the mag switch because it tests the ground portion of the mag switch, P-leads and in some minds saves the exhaust system.

A cropduster pilot spoke to our aeroclub years ago. He broke a hand when the engine fired while pushing the plane back. Lots of little bones in the hand - lots of surgeries to make it right. He said he was in the habit of shutting off with the mixture and leave the key in the mag switch. He thought he set it to off but actually selected the right mag position.

The right mag is usually the one with the impulse coupling. If you don't know what that is, read this: sacskyranch dot com/eng16.htm . The conclusion at the time was to continue to shut down with mixture because club namagement was a slave to mfr checklists and that's how they all said we were to shut down. But never put the key in the mag switch unless ready to start the engine and remove it before shutting off the master switch. Also, always pull the key and set it on the glareshield, then check for it before messing with the prop. That has worked for me, but does nothing to defend against the switch that allows key removal in any position. If that's the case, shutdown with the mag switch makes more sense.

Posted by: Thomas Connor | February 28, 2013 9:41 PM    Report this comment

If you lean the engine at idle to the point where it almost quits and then briefly turn the mags off, there will be no backfire or muffler damage. The problem happens when it's done at full rich. You basically fill the exhaust will lots of fuel and then ignite it.

Posted by: Scott Dickey | February 28, 2013 11:35 PM    Report this comment

Thomas--I don't see anyone here advocating shutting down with the mags to save the exhaust system--rather, if you are going to check mag grounding, bring the throttle to idle before shutdown-turn off one mag, then the second one to observe that the engine quits. Do NOT turn the mags on again in order to shut down with the mixture--there is no reason for that, and you do risk a backfire.

You need not do this every time--but as mentioned, pilots should do this occasionally to check for hot mags.

ALL of the small engines without mixture controls shut down with the mags--with no detrimental results.

Posted by: jim hanson | March 1, 2013 12:06 AM    Report this comment

"I was instructed to shut down with the mixture to make sure fuel was cleared from the spider to the injectors and cylinders."

It's curious how these kinds of accepted wisdom get passed down from instructor to student. If we unwrapped that onion by asking why, we would probably find no particular reason.

If the engine is a difficult hot starter--some are--the lines and cylinders can be easily purged in a few seconds for the next start. The fuel isn't going to somehow go bad in the spider lines and induction.

I suspect most such wisdom is just steadying the horses. We do it that way because we've always done it that way.

Posted by: Paul Bertorelli | March 1, 2013 4:17 AM    Report this comment


Checking your P-lead functionality after a flight (during shutdown) has value, to the extent that it can support increased confidence that the grounding will be sound for the next flight. Checking your P-lead functionality before a flight (during run-up) has value, to the extent that it can support increased confidence that you will be able to ground out a malfunctioning magneto while in flight. Too many pilots presume that the failure mode of a magneto will be benign. "It already failed, so why would I need to shut it off?" Here's one example: the magneto becomes loose enough to allow it to rotate slightly on its accessory drive mounting pad. The result is a change in spark plug firing angle that renders the engine incapable of producing useful thrust. That redundant second magneto isn't much use to you if you can’t shut off the now-mistimed magneto. Thus, the value of checking the P-lead functionality before committing flight. It's also a good example of why "redundancy" and "reliability" are not synonyms. Failure mode analysis is an underappreciated craft. Ask a Boeing battery systems engineer, these days.

Posted by: Tom Yarsley | March 1, 2013 6:17 AM    Report this comment

Maybe I've just been lucky, but in 50 years and 30,000 hours of flying (16,000 of which are in piston airplanes), and 312 unique types--I've never had a cause to switch to single mag in flight--though I suppose it COULD happen.

It is akin to the brief FAA prohibition on taking off with flaps in Navajos, King Airs, Barons, Dukes, and Aerostars--someone at the FAA opined that it put those aircraft at risk if an engine failed right after takeoff and before a chance to clean up the aircraft--an exposure of mere seconds. The FAA pulled the reference to takeoff with flaps from the flight manuals. The predictable result? No change in loss of engine accidents on takeoff, but a MARKED increase in the number of these airplanes running into obstacles off the end of the runway with both engines running.

The point--sometimes we CREATE problems where none existed before in an attempt to cover every contingency. Grounding out a mag before takeoff is an example: Switching it back on again while the engine is running gives a real possibility of a backfire--which can loosen the exhaust baffles and create an engine power problem in itself. You accomplish the same check by occasionally shutting down with the mags at the end of a flight--no chance of backfire. Maybe that's the reason I've never seen a manufacturer advocate the "check for mag grounding" on a pre-takeoff checklist.

Posted by: jim hanson | March 1, 2013 8:38 AM    Report this comment

I'm in the habit of doing an in-flight mag check while in cruise LOP. According to GAMI, the ignition is at max stress while LOP, so that's the time to test it and capture the results on the EDM. If I happen to select 'off' the plan is to set mixture to ICO and reset the mags to both, then add mixture back. But I've never had to.

I have comrades who are afraid to do an in flight mag checks because "there be dragons." Eliminating that fear would have saved one a cold night along a mountain road waiting for rescue.

He made a January trip from From Missoula MT - MSO) headed for Lincoln MT - S69 - in his C-182. Both airports are in some rather tall country. He made a pass over a partner's house about the time the engine went very seriously rough. It would hold altitude but would not climb. He says he fiddled with mixture, carb heat etc. Lincoln was close and he was over a road but the final route segment was over a narrow canyon he didn't want to land in if the engine quit, so he landed on a straight segment of road in minus 20F temps.

Posted by: Thomas Connor | March 1, 2013 1:12 PM    Report this comment

A mag check showed one mag was the culprit, and the engine ran fine on the other mag. (Autopsy later revealed teeth broke off the nylon distributor gear). There was discussion of taking off on one mag to get to a warmer place, but after shutdown it would not restart. The failed mag was also the impulse coupled mag, so the decision was made for him.
He was afraid of in-flight mag checks and resolved he would never do one. If he had been comfortable with it, he might have resolved the problem in flight and avoided the front page.

Posted by: Thomas Connor | March 1, 2013 1:12 PM    Report this comment

A mag check showed one mag was the culprit, and the engine ran fine on the other mag. (Autopsy later revealed teeth broke off the nylon distributor gear). There was discussion of taking off on one mag to get to a warmer place, but after shutdown it would not restart. The failed mag was also the impulse coupled mag, so the decision was made for him.

He was afraid of in-flight mag checks and resolved he would never do one. If he had been comfortable with it, he might have resolved the problem in flight and avoided the front page.

Posted by: Thomas Connor | March 1, 2013 1:14 PM    Report this comment

The battery on a B24 failed and I tried to hand prop it. Well this particular aircraft had a prop ratchet. After a few tries someone of the crowd who was watching thought I was useless and told me to get in and do the controls while he will show me how to hand prop. There we were me inside feet hard on the brakes prime the engine, full rich, power three quarters, key in and OFF. "Mags on" came the call I returned "Mags on" and then watched the face of the guy when he gave the prop one major flick only to watch it spin rattling around.

I have seen earth connection corroded through but still in position although not able to pass current. Don't trust the mag switch just because it worked the last time, it could have corroded through by the next time it is used.

Posted by: Bruce Savage | March 1, 2013 4:07 PM    Report this comment

And if he had done the mag check, and 10 minutes later it failed--would he not be in the same boat? Would checking the mags in flight every half hour be safer? How about every 15 minutes? How many mag checks is enough--or too much?

Sometimes, we can study a problem (or perceived problem) to death.

I'm not a believer in "The more things I put on a checklist, the safer I must be" doctrine.

Posted by: jim hanson | March 1, 2013 4:45 PM    Report this comment

Wow... that was some drama. Only thing hurt was his ego fortunately. Hope the insurance man comes through for him. He would be eligible at our EAA chapter's "Broken Prop Award" which went unclaimed this year. Evidence that the regulators at the FAA are making us all 'safer'?

I don't buy the exhaust damage theory. Only problem I ever had was when I did a sloppy mag check during run-up backfired. That was embarrassing.

Also, I don't see any reason to touch the mag switches in flight. I pretend to exercise the mags when practicing emergency procedures, but I never actually click them around for grins and giggles. I don't see any reason to turn a mock emergency into a real emergency.

I also wonder where the habit of turning the engine off with the mixture came from. This is not how I was taught. Then again, my airplane doesn't even have a mixture control. What did people do before they invented mixture control?

We had problems with the P-leads last summer after we rebuilt the mags. When I switched off the mags, and the prop kept running, I was not surprised. I had been exercising the mags during the taxi back and did not notice a drop. I already knew what was going to happen before I turned the key to the off position. No sweat, just turn the fuel valve off and wait.

Posted by: Andre Abreu | March 1, 2013 10:21 PM    Report this comment

Another thing, when working on your airplane, make sure you remove the ignition harness... especially when timing the mags and compression checks. That prop will cut you into bite sized pcs. Like the old guy I know. First responders were sent back to retrieve his severed hand. Airport dog beat them to it. Talk about biting the hand. True story.

Posted by: Andre Abreu | March 1, 2013 10:22 PM    Report this comment

Part 1


"How many mag checks is enough--or too much?" We check things – usually once – before undertaking a phase of operations that requires the functionality of the items/systems being tested. We do engine run-ups prior to takeoff, because if testing reveals a potential flaw, declining a takeoff is a viable option. It’s not a question of "how many items are on the list." It’s a matter of understanding the failure modes of the items being tested, and the capabilities and the limitations of the test procedures.

Properly done, a pre-takeoff P-lead check is harmless, and in this space we've already heard two commenters relate stories about circumstances in which the deliberate shutdown of one magneto was the appropriate solution to an in-flight engine performance problem.

(Continued in Part 2)

Posted by: Tom Yarsley | March 2, 2013 8:29 AM    Report this comment

Part 2


We do pre-flight checks because they represent a prudent and not inconvenient opportunity to forestall disaster. Manufacturers' checklists are well-intentioned, but frankly often stupid. Here's one example of such stupidity: Just about every Piper checklist out there includes this item in the immediately-before-takeoff drill: "Fuel selector - fullest tank." Think about that... You've started the engine(s), taxied around for a while, done a run-up – all without a fuel-related incident. Your present fuel-delivery situation looks promisingly reliable. Why on earth would you now switch over to a different tank, and then – without letting a couple of minutes pass by – attempt a takeoff? It's nuts! I've trained all of my students to start the engine on one tank, make their initial radio call-ups, then - before beginning to taxi to the runway - to select the tank that they intend to use for takeoff. This allows them to log a few minutes using each tank AND it assures that a deliberate decision is made about what tank will be used for takeoff.

If it can save your ass, and it doesn't pose unacceptable inconvenience , then a rational test item belongs on a checklist.


Posted by: Tom Yarsley | March 2, 2013 8:30 AM    Report this comment

Andre: All Cessna POHs I'm familiar with from 1962 to 2005 say to shutdown with the mixture control. The Piper Comanche and Beach Sierra say the same thing. So that's where I got it from. If your ride doesn't have a mixture control then it's moot eh?

As far as inflight mag checks - The guys at recommend it. (APS is an on line engine management course put on by the guys who brought us GAMI injectors and Tornado Alley Turbos. The course is supported by data from their test cell and historical data from airlines when they were powered by big round engines. According to the FAA, the GAMI test cell 'is the best instrumented engine test cell in the world).'

APS says: "The runup mag check is not a demanding test. About all it does is verify that the mags didn't fall off." "An LOP mag check can reveal condition of the mags, wires and plugs, and an engine monitor can reveal which mag, wire and plug."
The guys at APS also think all engines operated without engine monitors and fuel flow is 'engine abuse.' Those are the guys who teach 'brake mean effective pressure' and how to control it, Lean of peak ops and why it's better than ROP for the engine and pocketbook, and run a TSIO-540 into heavy detonation in their test cell just to show what it looks like. Those guys are data junkies. Data is better than opinion it says here.

Posted by: Thomas Connor | March 2, 2013 9:35 AM    Report this comment

Here's a link from Sacramento Sky Ranch about how to check mag grounding: sacskyranch dot com/faqslickmagneto dot htm used to have a gem of a book called the 'magneto manual' that gave theory and diagnostic info. The book appears to be out of print and sacsky is going out of business. A real shame. I bet a pdf of the mag manual is available on the web.

Posted by: Thomas Connor | March 2, 2013 10:12 AM    Report this comment

I found the sacskyranch magneto manual on amazon: amazon dot com/Magneto-Ignition-System-John-Schwaner/dp/B0006P6ZLW

Posted by: Thomas Connor | March 2, 2013 10:18 AM    Report this comment

A number of years ago I learned from JAARS missionary pilots to do a post flight mag check as well as a preflight mag check. Odds are if something is going to go wrong, it will be during flight, why wait til you're all ready to take off to find a problem?

Posted by: Richard Montague | March 2, 2013 11:03 AM    Report this comment

This may be a distinction without a difference to some, but there is a difference between a grounding failure in the mag switch and a p-lead that breaks or fell off a mag. If the wire falls off the mag that mag will fail both the mag check and the mag switch grounding check. If the mag switch failed internally, it could pass the mag check but fail the grounding check, because the two tests use different contacts within the switch.

Apparently that was a problem with certain Bendix ignition switches because faa ad 76-07-12r1 required a test of the switch for such a failure mode. Does your ride have that switch?

The AD is available here: swaircraftappraisals dot com/MeyersForum/Maintenance/ADs/Continental/76-07-12 dot PDF . I cannot find a supercedure, amoc or termination, so I assume it is still in force.

From that may have sprung the procedure suggested by most: Test the mag off switch and let the engine quit, because that is what the AD suggests.

Mike Busch has a discussion about what is mandatory for part 91 operators in his EAA webinar on the topic, and concludes that only the FAA can say when stuff is mandatory, not the manufacturer. Such mandatory instructions are in the limitations section in the POH or maintenance manual or an AD. Since this is an AD and mandatory - at least for Bendix ignition switches - it appears the grounding test is also mandatory and supersedes the POH.

Posted by: Thomas Connor | March 2, 2013 12:23 PM    Report this comment

Andre--I don't buy the exhaust damage theory. Only problem I ever had was when I did a sloppy mag check during run-up backfired. That was embarrassing. "

Switching both ignitions off while under power (whether in flight or on the ground) produces a backfire. It doesn't do the engine any good--and it CERTAINLY doesn't do the exhaust any good. Most exhausts become unawirworthy when the baffles or cones internally become loose. When they become loose, the exhaust is restricted, resulting in a loss of power--either a rough runner or a simple loss of power. A backfire certainly doesn't do those internal baffles any good.

If doing mag checks in flight was a good idea, don't you think that the
A. engine manufacturer would recommend it?
B. Aircraft manufaturer would recommend it?
C. Magneto manufacturer would recommend it?
D. The FAA would recommend it?
E. The Kings would recommend it in ANY of their courses?
F. It would appear in print in any of the flight training manuals--Kershner, Airplane Flying Handbook, Modern Airmanship, Stick & Rudder?
G. I have a 58 year collection of Flying and AOPA magazines--I've never heard an advocate of doing random mag checks in flight--EXCEPT IN AN EMERGENCY.

Often, people think they are being pro-active (the "if a little bit is good, more must be better" theory.) Some things are better left alone.

Posted by: jim hanson | March 2, 2013 3:22 PM    Report this comment

Jim - Kerschner and King taught engine management?

I like both, especially Mr. William, but your collection is dated. Put in-flight mag checks in the same basket as flying lean of peak, because it is encouraged by the same people who have the test cell data to back up their claims and recommendations, and probably post-dates most of your references (except the marvelous Wright Whirlwind engine operator manuals, which also recommend both LOP and IFMCs and is where the ideas came from. do you have a copy?).

Cirrus wholeheartedly embrace both. Recent sources include: Gami dot com, advancedpilot dot com, Mike Busch in his eaa webinars at eaavideo dot org/video dot aspx?v=1878459789001, cessna dot org articles and savvyowner dot com articles. John Deakin in his Pelican perch articles avweb dot com/news/pelican/182146-1dot html .

I know I'm giving you library addresses and not specific references because I need to go fly. I can provide more specific references later. Oh wait, here's one: avweb dot com/news/savvyaviator/191197-1 dot html

Here's a test question: Which is more reliable: A factory new engine, or an engine 500 hrs past TBO?

Here's another: Lyc has a CHT redline of 500F on the parallel valve O-360 engine. That's an FAA and engine manufacturer approved limit in the limitations section of my Cardinal POH. If it say it's Ok, do you think it's really Ok, especially with a single probe CHT gauge?

I'll be back!

Posted by: Thomas Connor | March 2, 2013 4:41 PM    Report this comment

The point is--NONE of the references--the manufacturers, the FAA, the Kings, the classic textbooks--NONE of them advocate your procedure. Do you suppose there may be a reason for that?

You attempt to obfuscate by relating your procedure with "flying lean of peak," LOP CAN work--under the right conditions--but not ALL of the time (high power settings, carbureted engines for example--not even GAMI advocates those. Flying LOP is hardly the same as advocating a procedure that has dubious value, and MAY cause harm to the engine.

You then throw out a "test question"--an obvious attempt to create "straw man". Stick to the subject. (BTW--the answer is "past TBO"--of the 9 engine failures I've had in 30,000 hours, the HIGHEST time failure came on an engine with 660 hours.)

Your procedure creates the possibility of a problem where none existed before. That's OK for you if you want to do it--but none of the people that built the engines, built the mags, built the airplanes, or teach flying seem to agree with you.

Posted by: jim hanson | March 2, 2013 5:00 PM    Report this comment


To answer your first question, yes: Ignorance. I don't know which FAA or King document your refer to but I cannot prove a negative anyway, so you may be right. I have no way of knowing how dated your library is or how well you've kept up to date with engine management. As I stated previously, Lycoming had it dead wrong in the early 90s. But they want to sell engines. If that is ok with you, fine with me.

Mr Kershner's advanced pilot manual (94) recommends selecting the smoothest mag if one misbehaves in flight. How that differs from an IFMC as MY references suggest, is not clear. Kerschner also recommends leaning to peak CHT (but below redline) for a give altitude. Yeah - I didn't stutter. Peak CHT. That's a felony in my schoolhouse, based on metallurgy. But I pardon him for the other good things he taught.

As far as the LOP procedure, as I said before it is recommended by the same people who recommend IFMCs. Just putting credit where credit is due. They tend to be data driven.

So Jim, can you explain how an IFMC will damage the engine, mags, airplanes or instructors? What are the risks that I have not already addressed? Where are the dragons?

Posted by: Thomas Connor | March 3, 2013 12:18 AM    Report this comment


"Switching both ignitions off while under power (whether in flight or on the ground) produces a backfire." Doing this at idle power does NOT produce a backfire. I and my students have done this many thousands of times - without experiencing even ONE backfire.

Posted by: Tom Yarsley | March 3, 2013 8:23 AM    Report this comment

Andre Abreau said: "Also, I don't see any reason to touch the mag switches in flight. I pretend to exercise the mags when practicing emergency procedures, but I never actually click them around for grins and giggles. I don't see any reason to turn a mock emergency into a real emergency."

Andre: Can you explain how an in flight mag check would create an emergency? You already said you don't buy into the exhaust damage theory so I'll rule that out. Can you make your thinking more clear?

Posted by: Thomas Connor | March 3, 2013 2:46 PM    Report this comment


Flying is dangerous.
Do you ever play with the ignitions switch driving your car? I have and it is no big deal. It gets really hard to steer. Also, when my children were young, I would kick my car into neutral and play "can we make it". Harmless fun. I don't play "can we make it" with my daughter in the front seat of the Pietenpol Aircamper.

The Piet has oil pressure and engine temp gages, tach, ASI/ALT and carb heat. As it sits in the EAA 582 hangar, it has one of those awful twist-type ignition switches with a key dangling from it(as if). I am not going to touch the ignition switch unless I am trying to kill the engine. If I were to inadvertently kill the engine in flight, my airplane doesn't have one of those fancy electric starters. If the prop stops in flight, I'm not going to be able to get out and swing my hand carved prop. My only chance to restart the engine is to hope it windmills. Why tempt fate? Those switches are notoriously unreliable.

Posted by: Andre Abreu | March 3, 2013 4:45 PM    Report this comment

Of course the only truly safe procedure is to assume it is like the gun...always loaded.

I will admit I never made a distinction between the mag check groundings and the "off" position (both grounded) and have generally depended on the mag check to verify P-lead function. A good hint from Thomas.

Just the other day when walking by the prop (in tight quarters) I literally only lightly brushed one blade and was rewarded with a loud "click" as the impulse coupler triggered. Scary stuff, for sure.

Posted by: John Wilson | March 3, 2013 5:28 PM    Report this comment

Thomas Connor--I assure you that I'm VERY up to date on current practices of engine management, LOP operation, and engine monitors. In addition to the turbine equipment, I own 12 airplanes with piston engines, including turbocharged twins. I'm a 30 year + subscriber to Aviation Consumer, and nearly that long for Light Plane Maintenance. I keep my old copies, and not once have I seen anyone advocate an check of the mags in-flight just to see if both are working normally. I keep my 50 year old collection of Flying and AOPA magazines--not once can I recall anyone advocating checking the mags if the engine is running normally.

Kershner--the key phrase here is "turning one off IF ONE MISBEHAVES IN FLIGHT." That doesn't mean turn of a normally operating mag.

You ask where the risks are with in-flight mag checks. What happens if you select a mag and it IS dead? What will happen when you turn it back on? Do you suppose it MIGHT backfire? Is this good for the engine? The exhaust? You just created a problem where none existed before.

I met Bill Kershner several times. He did a piece on "The over-eager instructor"--a guy that would do actual engine shutdowns in flight to "teach" forced landings--and would pull a mixture on a twin on takeoff to "teach" single-engine procedure. That guy created an emergency where none existed before. Are we safer for the experience? I think not.

Posted by: jim hanson | March 3, 2013 5:57 PM    Report this comment

Thomas Yarsley--Jim says "Switching both ignitions off while under power (whether in flight or on the ground) produces a backfire." Doing this at idle power does NOT produce a backfire."

Read it again--and this time, look for the "under power" part of the quote. It was put in for a purpose.

Have you never had a student inadvertently turn both mags off during a mag check (typically only 1700 rpm)? And you have never had a backfire?

Have you ever read "Fate is the hunter"? Ernie Gann was a copilot on a DC-3 that had accumulated induction system ice and was losing power. In desperation, the captain turned off the ignition and back on inducing a backfire to clear the ice. BTW--the book is NOT fiction.

Posted by: jim hanson | March 3, 2013 6:09 PM    Report this comment


I've witnessed and experienced backfires. But never while doing an idle-power P-lead check, a practice that herein has drawn your naked distain.

One practical way of familiarizing new students with multi-position magneto/key switches is to have them practice actuating the switch while the engine isn't running - in the low-pressure environment of the parking ramp. They find it easier to literally "get the feel" of that task when they know that: 1. there's no consequence for getting it wrong, and 2. the Hobbs meter and/or tachometer isn't running - so it's a very low-cost lesson. And it's a great teaching oportunity, because it allows the student to learn that the spring-loaded "start" does nothing that will cause the engine to turn - if the electrical system isn't configured to allow current to flow to the starter assembly. That seems helpful in separating the electrical and ignition systems in the minds of students whose only exposure to motor vehicles has been with modern automobiles.

While we're on the subject of checklists (sort of), another favorite peeve of mine is the commonplace under-emphasis on turning OFF electrical fuel pumps after a successful engine start. I've actually heard instructors say "What's the big deal? You have to turn on the pump for takeof, anyway. What's he harm in just leaving it turned on until after takeoff." The lemonade in this is that it's another teachable moment.

Posted by: Tom Yarsley | March 4, 2013 7:31 AM    Report this comment


WRT in-flight mag checks - IFMCs - I think you are advocating the 'do no harm' philosophy. Nothing wrong with that. And there is nothing wrong with sticking with what has worked, and healthy skepticism of ideas that pose risk. That said, some claimed benefits are overblown, as are some claimed risks. The lean of peak advocates were originally treated similarly by manufacturers, mechanics and others. But by explaining that an engine monitor is a necessity, developing simple procedures like avoiding the Red Box and how to interpret the results, there are engine and airframe converts. A few curmudgeonly mechanics even acknowledge the benefits.

Regarding IFMCs, I searched the Flying and AOPA web sites for the topic and you are right, there is isn't much there.

A web search was more fruitful, and it appears there are tribes of cautious converts among Bonanza, Cirrus and Cessna groups running the big injected engines. They discussed the pros an cons and asked for help when they ran into specific concerns. Gee - almost scientific

The concerns included various scenarios where they might end up detuning crankshaft counterweights, cause afterfire damage to the exhaust and induction/air filter damage from backfire. More on that later.

Posted by: Thomas Connor | March 4, 2013 12:26 PM    Report this comment

George Braley, Walter Atkinson and John Deakin developed the Advanced Pilot seminars in the early 2000s, and John wrote a slew of articles on engine management for Avweb in that time frame. He mentioned IMFC in this column avweb dot com/news/pelican/182179-1 dot html but doesn't go into detail.
If readers are not familiar with his work, all of his columns are listed here: avweb dot com/news/pelican/182146-1 dot html?type=pf As always, replace the word 'dot' with a period.

John, Walter and George made up for the oversight by going into excruciating detail in their seminars. The online version is available here: advancedpilot dot com/

Mike Busch at savvyaviator dot com recommends the IFMC in his avweb articles: avweb dot com/news/savvyaviator/193986-1 dot html . His recent eaa webinars also discuss IFMCs in detail:

Posted by: Thomas Connor | March 4, 2013 12:28 PM    Report this comment

Caveats: The IFMC is a diagnostic tool, just like the preflight mag check. If you are happy with the runup mag checks then fine: It certainly will identify gross problems. John thinks they are a waste of time unless at high power and leaned to the nuts. Then there is the psychology of a marginal mag, say 175 rpm drop when the POH says 150 rpm: Since you are all loaded up and about to go flying, many find it easy to rationalize 'burning out' any problems by flying and indeed, it often does the job (trend analysis probably tells more about what's going to happen than a one-off mag check: If it has been progressively getting worse, get it fixed). OTOH, a mag check in flight or after landing really makes more sense from a 'now we'll fix what we find' attitude. And there is the grounding check.

By the way, this discussion convinces me that a shutdown with the mag switch instead of mixture is the better way: I think it verifies what we need to know and avoids accidentally leaving the switch on.

Posted by: Thomas Connor | March 4, 2013 12:29 PM    Report this comment

One of the Bo drivers asked John about damage from an IFMC if a mag has failed or just one spark plug has failed. Here's his detailed answer:

"Let's differentiate between the classic backfire, where the "fire" gets into the INTAKE manifold. If the mixture there is within combustible limits (it often isn't), the fuel/air vapor will ignite "vigorously," often seen as a gout of flame out the carburetor intake and a big bang. Since the intake manifolds are not designed to take this overpressure, the backfire may well be harmful. In the big radials this is ALWAYS due to a "too lean" mixture (not enough fuel, or too much air).

Posted by: Thomas Connor | March 4, 2013 12:31 PM    Report this comment

The "afterfire" occurs in the exhaust manifold, and is always the product of unburned fuel lighting off. If there's a lot of raw fuel in the exhaust manifold, a truly spectacular burst of orange fire (20 feet long, or more) can come out the exhaust stacks until the fuel is all burned. This is generally harmless, unless there is a continuing supply of raw fuel. Eventually, it may light something else off, such as the oil on a very oily engine (common on the old radials). On the other hand, if the fuel in the exhaust is well vaporized, it can also ignite "vigorously," causing a huge bang, often a series of them during the start. These may very well cause cracked exhaust stacks, which are deadly on a turbo'd engine, and not good anywhere. I saw this most recently on our old C-46 where a trainee got a series of about six bangs. Sure enough, the left outboard exhaust "trumpet" was found cracked almost all the way around.

Most of the above discussion is applicable to the starting. Once the engine is running, things tend to settle down and remain stable. The modern "flat" engines have fewer problems with all this, although all the above ARE possible. A stack fire on a Bonanza trying to get a start will sure singe the paint on the fuselage and cowling above, AND it may well be the ignition point for that puddle of fuel on the ground from the awful "flooded start" so many people use!

Posted by: Thomas Connor | March 4, 2013 12:33 PM    Report this comment

Now, at any cruise power, inflight, if you kill the combustion in a cylinder by turning both plugs off, the unburned fuel will just get blown on through, and ejected into the exhaust stack, where there is "fire" (from other cylinders) to light it off more or less harmlessly. If you turn both mags off, ALL the fuel blows on through, and there's no "fire" to burn it. It's probably a highly combustible mix, so when you turn the mags back on, and combustion begins again, the first shot of hot exhaust will probably light off everything still in the exhaust manifold, and you may get a momentary "overpressure." I don't know how much, and I'm now speculating, but I don't want to do that to my engine. I have done it, and it's a VERY ABRUPT resumption of power, at the very least. The "bang" (if
any) may be masked by the rest of the engine noise.

Note that IF you ALREADY have a dead mag, then doing a mag check will be the same as if you turned 'em both off. If you know what the engine monitor shows with a normal engine, you won't ever do that, because your EGTs will all be MUCH higher than normal if one mag fails. That's the time to ease well back on the power before you do the check.

If only one cylinder goes dead, the engine will seem like it's jumping off its mount, but that should be harmless, if corrected quickly.


John Deakin

Posted by: Thomas Connor | March 4, 2013 12:34 PM    Report this comment


Another Bo driver wrote: "A really nice post. In run up and start in the Beech I do sometimes get a exhaust fire for when it is hot fuel vapors get into the Exhaust and yes there is a loud pop. I do shut down and check the stacks to look for cracks for havng flown some radials in the past you do not want to fly with cracks in the exhaust system. With the intake backfire there is a real "Balloon of flame" that comes out of the intake and it is a usually a result of over priming on a cold day. It can be quite damaging if one does not correct and "Swallow the flames" as we called it. Keep the starter running and open the throttle all the way. The radials sometimes would get this condition. Interesting in the old radial airline days there was always a "fireman" with an extinguisher standing near by during the engine start. As a copilot it was my job to get the fireman to come on station when we fired up the Beech 18 for intake fires were more common with long throated intake manifolds."

Posted by: Thomas Connor | March 4, 2013 12:35 PM    Report this comment

Thomas, how is engine shutdown using the mags better than killing the mixture? (did I miss something here?) Why would you want to leave the induction system charged with fuel? That would be an accident waiting to happen in the case of a broken P-lead. Or, are you saying kill the engine with the mags to make sure it'll quit, then go back to "both" and cut the mixture?

Posted by: Will Alibrandi | March 4, 2013 12:52 PM    Report this comment

So it seems some precautions are in order for messing with the mags on the ground and in the air. Grounding check of the P-leads and switch 'off' position are good, which is what this blog was originally about. A ground mag check is too, however cursory, to make sure they are still attached. If it passes a ground mag check then an IFMC should produce no damage, but an IFMC might reveal weak or cracked sparkplugs, high tension leads and any carbon tracking in the mag that a ground mag check might miss. Is the knowledge worth potential risk to crank counterweights, induction and exhaust plumbing? Here are two examples where I think it is.

A cracked ceramic sparkplug nose insulator is the primary cause of pre-ignition that leads to a melted piston. Mike Busch has an EDM data dump of just that. Advance to the one hour point on this webinar for the story: eaavideo dot org/video dot aspx?v=1204537102001 .

Carbon tracking causes high-altitude misfire between the mag distrubutor towers. If you fly high it might be important.

Slick recently had a spate of soft carbon brushes that disintegrated, filling the mag with carbon dust that caused arcing that melted the distributor bearing support, shutting down the mag. Is that worth knowing about BEFORE the mag fails? Your call.

Posted by: Thomas Connor | March 4, 2013 1:04 PM    Report this comment

I haven't seen mention of impulse coupled or electrically boosted mags in this discussion, so perhaps a primer on mags is in order. Bottom line is that most aero piston engines have one or the other. Here's a pretty thorough discussion by Mike Busch: avweb dot com/news/maint/182843-1 dot html He discusses impulse couplings and what they do, how many there are or might be. He also addresses the Bendix 'Shower of Sparks' and Slickstart boosters.

The accident Malibu's Continental TSIO-520-BE engine had two impulsed mags to improve startability. It apparently worked quite well.

Some suggest that smaller aero-engines are like smaller lawnmower engines, which do not have boosted mags, and give the J3 as an example. There are many J3 engine variants so some might, some might not.

Posted by: Thomas Connor | March 4, 2013 2:49 PM    Report this comment


mechanics work around engines and props a lot. So I asked a few how they deal with the risk of an engine firing as they work. The responses were as expected, like pull the key and if given a chance, do a grounding check. Some suggested we rotate aero engines backward to prevent an ignition event. I'm not sure that is an effective strategy, at least as far as surreptitiously ungrounded mags are concerned. Another said to pull the cowls and at least one spark plug per cylinder because they usually come in for a compression test anyway. Ironically, he was installing Prop-Guard on the blades of a twin C-310A. the cowls were still installed, so I had to ask. He pointed to the bank of mag toggle switches on the panel and said "they are all down, which is off. The door key has nothing to do with mags. And besides, I'm the only one who wrenches on this plane." Apparently he has a high degree of confidence in toggle switches and his wrenching.

Posted by: Thomas Connor | March 4, 2013 2:51 PM    Report this comment

Backing up to 'turning the engine backwards is safe', I thought I'd break it down to the ridiculous and ask: 'What will the mags do, and if the mags spark, what will the engine do?'

First, the mags: More accurately stated: "Turning an engine 'backward' will not wind and 'snap out' the magneto impulse coupling, if so equipped." That I know is true. Yet, we still have two mags at advanced timing trying to create excitement. Can they still make a spark? Probably, however feeble it may be.

This is not the same as saying the mag cannot fire if turned backward: There are many magneto fired 2-stroke chainsaws, motorcycles, snowmobiles and golf carts that will happily run forward and backward to say a slick or bendix won't make spark going backward.

But will a 4 stroke aero engine run backward? Probably not as happily as a 2 stroke, but how much does it take to whack someone? The exhaust valve is open most of the time after the firing stroke, so approaching the firing stroke from the wrong direction should accomplish little. Yet, There's this thing called 'kickback" that can smash up starters pretty good. One wonders what it can do to a noggin'.

Posted by: Thomas Connor | March 4, 2013 2:52 PM    Report this comment

The only way to guarantee safety around the prop is to remove at least one spark plug per cylinder. The next best is to ensure the mags ground properly thru the switches and the mag switches are off.

I bet there is a way to configure a press to test indicator light using the circuitry in a mag tester that would 'prove' the P-leads are connected to the mags and another to prove they are both grounded at the ignition switch. But that's probably overkill when a grounded shutdown proves the same thing.

Finally, electronic systems like the E-mag or the computerized Slick Lasar both boost starting spark and control ignition timing during start and at cruise RPM. I know nothing about the E-mag so I'll let others address it, but I had the Slick 4700 Lasar mags on a Lyc O-360 until the Lasar computer died an expensive death. It had a computer controlled capacitive ignition that fires both mags for both start and run. It also has three ground handling safeguards: The Lasar computer requires 12V from the master switch plus the mag switch has to be set to start or 'both' to fire them below 500 rpm plus it has to see three turns of the engine within a few seconds before enabling the CDI. Pretty ingenious idiot-proofing.

Said another way, it would not fire if the master was off, the ignition switch was in any position other than start, and it had to be spinning faster than most pilots can move a prop by hand.

Posted by: Thomas Connor | March 4, 2013 2:53 PM    Report this comment

Slickstart appears to offer some of that by installing it with a retard breaker magneto. Like the impulse coupling it boosts mag output, but it gets power from the starter solenoid, so it only fires when the key is in the start position and of course the master switch is on. Does that mean the mags could not cause trouble if they were not grounded? I don't know.

Installation procedures are here: championaerospacepubs dot com/docs/F-1100-SL2-96G dot pdf .

Lycoming makes it easy to replace an impulse with a retard breaker mag on their four bangers with SI1506: lycoming dot com/support/publications/service-instructions/pdfs/SI1506 dot pdf .

By requiring both battery power and a mag switch set to 'start' before it will boost, Slickstart seems to add a second layer of ground handling safety to grounding the P-leads. Some might find that useful.

Getting rid of impulse couplings seems like a good idea all on it's own. They snap and bang enough to self destruct over time, and if parts fall into the engine it can be bad news on several fronts. Both Slick and Bendix mags have SBs recommending impulse-coupling inspections and Bendix has ADs mandating them, so they represent a perceived if not real risk.

Posted by: Thomas Connor | March 4, 2013 2:54 PM    Report this comment

Will Alibrandi asked: "how is engine shutdown using the mags better than killing the mixture? (did I miss something here?)

Yeah, I think you did. Read the whole blog. But your response was the same as mine when the blog started.

Shutdown with the mag switch and you have confirmed that the mag switches ground the mags and that they are really off. Failing to do that is the common thread in prop surprises. There are just too many ways for fuel vapor to get into a cylinder after shutdown for it to be as positive as grounded mags.

Do both, and you've covered the waterfront.

Posted by: Thomas Connor | March 6, 2013 12:09 AM    Report this comment

Thomas you are hoping that the earth wire does not fail after shut down as they usually do. Just because it worked the last time does not guarantee that it is still connected when you leave the aircraft. The best is still the mixture. Get rid of fuel vapor and the chances of the engine firing up is very slim hence the need to prime after the fuel pump is switched on.

Posted by: Bruce Savage | March 6, 2013 10:33 AM    Report this comment

Well, I suppose there IS a chance that the ground wire fails while the airplane is immobile in the hangar--but it COULD be hit by an EMP, too.

Cutting the mixture is no sure cure, either--witness, starting a big Continental with fuel injection after a brief shutdown=Mags on, no prime, fuel mixture IDLE CUTOFF, throttle wide open--the engine fires right away, then throttle back and mixture rich.

Do it any way you want to--but the mixture control in idle cutoff is even LESS likely to prevent a start than turning off the mags.

I suppose you COULD turn the fuel selector off, as well (sarcasm).

Posted by: jim hanson | March 6, 2013 12:50 PM    Report this comment

Bruce Savage Said: "Thomas you are hoping that the earth wire does not fail after shut down as they usually do"

Hope? Fail as they usually do? Aside from corrosion I cannot imagine a functioning wire failing without provocation from vibration, maintenance or some ham-fisted dipshit tugging on them.

The issue isn't how you shut down, it's verifying that the mags ground and are grounded when you leave the plane.

There is no guarantee that after shutting down with the red knob that fuel doesn't boil in the carb or vaporize out of the injector lines and prime a cylinder.

There are also Paul and Jim with their J3 and C-120 that don't have mixture knobs. What then?

So the more I think about it the more I agree with Paul and Jim: Shut down with the mag switches and you have not only verified they work but also verified they are really off. No sparks, no putts.

Posted by: Thomas Connor | March 6, 2013 2:00 PM    Report this comment

Hmmm had a situation where after testing the mag switch the engine did not die or even try to. After several hours (14hrs to be exact) the fault was found. Where the p-lead enters the mag was corroded. The insulation was still intact and was holding the wire in place and there was no indication that it was at fault. As the mag unit was being removed the wire fell out showing the culprit. The copper was green nearly black, badly corroded and most definitely not connecting. Time was the real problem not some ham-fisted action, vibration or other provocation. The aircraft was well maintained and had just completed its 50 hours maintenance.

Sorry Thomas I do not hold too much for the mag p-lead. I do have a healthy respect for the chopper out in front. Saw the results of someone hand propping and didn't get out of the way in time. Nasty head wound.

Posted by: Bruce Savage | March 6, 2013 2:53 PM    Report this comment

"... after testing the mag switch the engine did not die or even try to." That's hardly the same as suddenly coming to life in they hangar. That's also the purpose of shutting off with the mag switch--in this case, you knew right away that there was a problem. Had you shut down wiht the mixture, you WOULD NOT have known.

As for only "50 hours maintenance"--that begs the question of what kind of maintenance, and by whome? Normally, a 50-hour inspection is little more than an oil change. If you meant 50 hours since the last annual--the airplane could have been sitting outside in a corrosive atmosphere. My Cessna 120 has always been hangared--the last 25 years in a heated hangar. There is not one bit of corrosion on it. Crusty and rotted wiring is not the norm--and certainly not something that normally occurs within 50 hours. Sounds like someone pencil-whipped the inspection. Hard to call that "well-maintained."

In any case, shutting off with the mags DID detect the problem, did it not? Why would you advocate anything different? Shutting off with the mixture did NOT detect the problem.

Posted by: jim hanson | March 6, 2013 3:29 PM    Report this comment

Side note: Someone up the line mentioned a twin cessna and 4 mag toggle switches. On the Cessna 120, the toggle switches were installed by the factory to be DOWN when on--instead of up like a light switch. One more reason to shut down with the mags--AND to look TWICE to verify that they are on the right position. Several times, well-intentioned people in the hangar have moved them to the "down" position in the interest of "safety."

Posted by: jim hanson | March 6, 2013 3:31 PM    Report this comment

Bruce Savage said:. . . after testing the mag switch the engine did not die or even try to. After several hours (14hrs to be exact) the fault was found. Where the p-lead enters the mag was corroded. The insulation was still intact and was holding the wire in place and there was no indication that it was at fault. As the mag unit was being removed the wire fell out showing the culprit. "

Sounds like an argument favoring the mag switch shutdown/test eh? If not I don't see how you would have known about the condition. As I said, do both and you'll know what you knew in this case, which is the important part.

What bothers me more is claiming fourteen hours to troubleshoot an engine that won't shut down with the mag switch. Here's a free diagnostic I googled for everyone to share: sacskyranch dot com/eng101 dot htm

Intermittent problems are more challenging, but you didn't report it as intermittent.

Diagnosis is best done by isolating the inductive mag from what should be a dead-short thru the switches and wires. that's done by removing the P-lead from the P-lead stud on the mag, which in your story revealed the problem. The hardest part is removing the cowl and P-leads.

If the ISOLATED wires and switches test as they should with an ohmmeter, it's the mag, which is tested with a mag buzz box.

So, what so we do to kill the other 13 hours?

Posted by: Thomas Connor | March 6, 2013 11:25 PM    Report this comment

For Thomas and Jim who cares? We will all do the shutdown our way no matter what anyone says.

If health and safety were at the height it is today, back when these aircraft were first designed do you think the propeller would be allowed to stay out in front ready to hurt anyone in its way?

We have complicated the whole flying experience - from starting to shutdown and then we have a fit because the young don't want what we have. They want instant start-up (get in and press a button, the aircraft must do a self diagnosis). Why all the fuss about something so simple as shutdown (turn off the key) get out and go home. The technology is there to ensure total safety why is it not being used? Because us old f**ts resist change that's why. I love my aircraft just the way it is I know when something is wrong and I usually know what it is. I've had many long years of experience in understand how it works.

As for the incident I mentioned, that happened fifty five years ago. What has changed to ensure it doesn't happen again? Nothing.

Posted by: Bruce Savage | March 7, 2013 7:31 AM    Report this comment

Bruce: If you go back to the original article you'll note that there was an incident and Paul speculated at the cause. There can be only two. Maybe we'll learn from it, maybe not.

It appears you are either conflicted or playing devils advocate: On 6 march you said 'shutdown with mixture is best.' On 7 march you say 'turn off the key and go home.' As I've said three times now, test the mags and shut down with mixture and you've covered the waterfront. The rest is details.

As an aside, there is an interesting discussion on stupid pilot trick #1 here : airfactsjournal dot com/2013/02/why-do-we-still-run-out-of-gas/#comment-67326

I'm a huge fan of idiotproofing. We run out of gas for a number of reasons. One is because GA gas gauges are not reliable and certified only to be accurate at zero usable. If a $20k Chevy can give accurate quantities and an idiot light at the last few gallons, why not a $500k plane? You and I have adapted with notched sticks, but it is rather primitive, but not as primitive as just eyeballing the fuel level.

When was the last time you dipped a car tank? We add totalizers, but there are some really user-hostile ones out there (the old Shadins were not user friendly). If there's no leak they are an expensive but effective alternative.

Posted by: Thomas Connor | March 7, 2013 4:22 PM    Report this comment

When was the last time you heard of a car engine starting with little provocation and taking an unpiloted tour of the puckerbrush? Yet here we are arguing over the best way to prevent it in planes when technology could easily reduce the threat.

I assume that the experts of the day wrung their hands as nav systems advanced from the A-N range to ADF to VOR/DME to GPS. Each is easier to use than the previous, provide better situational awareness. Yet there's always fretting from those who learned the previous system that there's something unholy and unreliable about the new. Granted, early adopters pay the highest price for the least-reliable version, but someone has to plow the first furrow. I suspect it won't be us.

Posted by: Thomas Connor | March 7, 2013 4:23 PM    Report this comment

Bruce--"For Thomas and Jim who cares? We will all do the shutdown our way no matter what anyone says."

Perhaps you missed this earlier--"Do it any way you want to--but the mixture control in idle cutoff is even LESS likely to prevent a start than turning off the mags."

Nobody is telling you how you HAVE to do it--just pointing out that there may be a better way than what you've done all along.

Posted by: jim hanson | March 7, 2013 6:14 PM    Report this comment

Thomas--good point on the fuel gauges. I've owned a Cessna 206--purchased as a factory demonstrator in 1974. Last week, I was returning from a trip, and the right fuel tank read zero after only 1.5 hours of flight--it should have read slightly less than half full. I switched to the other tank and continued home.

Cessna 200-series airplanes are notorious for inaccurate fuel gauges--the tanks are long and thin, and if you aren't level left/right and fore/aft, you don't get a full load of fuel--there are a number of accidents where people THOUGHT they had a full load, and didn't. Fuel totalizers are no help unless you get a full load.

In this case, the studs holding the bladder had come loose--I didn't get a full top-off, and the bladder curled up (the vent tube was unobstructed. If you can't trust the fuel gauges, fuel counter, or simply time the tanks, it causes lack of trust in the aircraft. Compare this system with the VERY accurate capacitance gauges in the tip-tanked Cessna 414 I fly--it accurately shows when there is only 1 gallon in the similar-sized aux tanks.

Posted by: jim hanson | March 7, 2013 6:24 PM    Report this comment

Does anyone know what ever happened to the ratchet-type starter for small Continentals? There was a lever under the panel that the pilot could pull that would pull the prop through. It only pulled it through one compression stroke--but if the airplane was a good starter, that's enough.

The negative of the use of older airframes and engines as legacy LSAs is the need to hand prop. With fewer pilots and linemen willing to prop an airplane, safety would be enhanced (and an objection removed) if something like that would be made available again.

Posted by: jim hanson | March 8, 2013 8:07 AM    Report this comment

So true that nobody can help you prop anymore.
I get treated like a leper when I ask for help. We just carry a rope to tie down the tail when we have to hand prop solo. The rope is tied around the struts. I get allot of wise cracks about the rope holding it together.

Posted by: Andre Abreu | March 8, 2013 9:15 AM    Report this comment


We had a bladder tanked C-182. It seems like a good idea but they sure find ways to fail creatively and insidiously.

I helped replace one on a Comanche's aux tank. Stuffing a 10 lb rubber bag thru a 5 lb hole was the major challenge. Finding someone with long skinny arms and strong hands was required to find and lock the snaps. Then we found it would not hold rated capacity. Grrrr!

Posted by: Thomas Connor | March 8, 2013 1:13 PM    Report this comment


What engine does your 120 have? What mags and do they have impulse couplings?

Posted by: Thomas Connor | March 8, 2013 1:20 PM    Report this comment


Was the ratchet lever some sort of foot lever, or?

I had a 1948 single speed Cushman scooter with a ratcheting lever on the floorboard: youtube dot com/watch?v=lzMxoSF_hC8 Lift with the hand, press with the foot. I've seen them on the Maytag washer engines too. youtube dot com/watch?v=gA78oWX2mO0 We had a two-horse hit n miss engine that had that lever too, but we preferred to pull the flywheels thru by hand. youtube dot com/watch?v=UP8laDwgtcc As an aside, they had buzz box ignition and the governor worked by holding the exhaust valve open. Things got pretty exciting if the governor failed. We didn't think the flywheels were good for more than a few hundred RPM.

Posted by: Thomas Connor | March 8, 2013 3:08 PM    Report this comment

Darn filter--how about simply adding www and a dot before

Posted by: jim hanson | March 8, 2013 3:32 PM    Report this comment

What is so safe about starting an airplane from the cockpit? I've never heard anyone or anything getting injured hand propping an airplane. It is definitely easier to start the airplane from the cockpit, but I would never claim it is safer. I love when I watch most goofy pilots start their airplanes. Right before pushing the starter button, they open the window and bark out "Clear Prop!" That phrase was never intended to be a command... it was intended to be a question asked to someone nearby to make sure that there are no small animals, objects, or super-models admiring the propeller. Next time you hear someone say that phrase, ask them this, "Hey Captain, was that a statement?" Be prepared for a very confused look.

Posted by: Andre Abreu | March 9, 2013 7:29 AM    Report this comment

Andre: Have you read the story about the Malibu that took a pilotless tour of a ditch, or the FAA video of ramp follies with pilotless airplanes doing silly stuff?

One wonders . . .

Posted by: Thomas Connor | March 9, 2013 12:15 PM    Report this comment

Ohh...lots of injuries and a few deaths propping airplanes, Andre. I wouldn't say they are common, exactly, but these things happen a few times a year in various situations.

Propping is quite risky. You have to be very careful about it.

Posted by: Paul Bertorelli | March 9, 2013 12:42 PM    Report this comment

As far as the 'prop clear' business, I want a command and response with my ground crew and don't hit the starter until either I get a response, or there is clearly nobody around, in which case it was a question. A 5 second interval between saying it and hitting the start button seems only fair, otherwise it's pointless.

I was IC on a CAP SAREX one time and needed to talk to a crew. As I walked up to the plane four people were hanging on the prop as a lineman poured a quart of oil in the engine. The door was open and the key was in the ignition switch. Rather than get all nasty about it I yelled 'clear prop' and pointed at the key. It had the desired effect and is probably one of the few times the phrase actually had any meaning.

Remember the priest in the movie 'Air America?" He stood in front of each plane and blessed it before the crew got in. I do the same, checking for dogs licking blood off the prop or sleeping under the plane, gas caps, leaks, tires, baggage, proper number of parts, and tell nearby people to find a hiding place safe from the shrapnel, especially if there are kids or people working in the prop blast zone. The routine gives me a moment to collect my thoughts and personally warn others. It also makes the expletives I yell at the ramp gods superfluous.

I also occasionally get a 'Prop clear' from someone actually trained in command and response.

Posted by: Thomas Connor | March 9, 2013 12:55 PM    Report this comment

Almost related to the prop clearing stuff was a King Air that crashed after takeoff at my home drome. The pilot - Mr. safety and chief pilot at the FBO - was in a rush, arrived late and departed with two pax who had flown with him many times and loaded themselves. A witness saw him taxi out with a hangup bag lying on the tail and tower reported the bag fell off the airplane's tail onto the runway. The nose bay door also came open, scattering charts. The plane crashed as it circled back to land. If the pilot had just taken two deep breaths and five seconds to eyeball the plane he might have caught the problem.

Posted by: Thomas Connor | March 9, 2013 1:05 PM    Report this comment

Ground crew? At the remote airport I fly from there is generally nobody within a half a mile when I crank up. We do have free range bears, coyotes, deer, beavers, Canadian geese, rabbits, groundhogs dogs and whatever else is in season. The main reason I yell "Clear Prop!" is in case something or someone has snuck up and laid down in front of the plane, it will make a better story to tell from the witness stand and on the insurance report. Actually I guess it is not so much a command or a question but a prayer.

Posted by: Richard Montague | March 9, 2013 9:09 PM    Report this comment

Richard: good one!

After reading my safety briefing to the pax ("This is your final opportunity to re-consider . . .") they do all the praying my airline requires.

Posted by: Thomas Connor | March 9, 2013 10:56 PM    Report this comment

Nose bay doors--on a King Air? There is no nose baggage on a King Air.

And why would charts be in the nose? Why carry charts you can't get to?

Garment bag on the tail? Even an old King Air horizontal stabilizer is 7 feet off the ground--I'm 6' 4", and I can't see the top of the horizontal. I doubt that anyone would throw a garment bag on the horizontal, over their head.

The bag fell off on the runway before the aircraft became airborne? Then why would the airplane crash?

Too many issues with this one.

Posted by: jim hanson | March 12, 2013 12:00 PM    Report this comment

Probably wasn't a King Air, but some other twin?

Posted by: Will Alibrandi | March 12, 2013 1:24 PM    Report this comment

Still lots of unanswered questions.

If the garment bag fell off on takeoff, why the crash?

Why were charts left in the nose? I can't think of any pilot that would do that.

The pilot remained in the cockpit while passengers unlatched the nose and loaded baggage? There is a key lock on the nose baggage compartment on a Baron--the pilot would have to shut down, remove the key, hand it out the door to the passenger, and re-start. Once shut down, I've never seen a pilot do that in running FBOs for 42 years--but then, people DO do some unbelievably stupid things--always inventing another way to kill themselves.

Every Model 55 Baron I've owned has had a safety latch that only allows the nose baggage to open a small amount--kind of like the safety latch on a car hood. Most model 58s have a door ajar light.

Posted by: jim hanson | March 12, 2013 1:52 PM    Report this comment

Darn filter took out my link. jim, re-read my most on the crash, which answers your doubts, then this: aviation-safety dot net/wikibase/wiki dot php?id=35222

Posted by: Thomas Connor | March 12, 2013 5:53 PM    Report this comment

Jim: Found the NTSB report: ntsb dot gov/aviationquery/brief dot aspx?ev_id=20001206X02655&ntsbno=SEA95FA017&akey=1

There were a lot of witnesses who were surprised at Harry's actions and inactions that day, but his week had not gone well with a car wreck, hospitalized family, other problems. He was late for the flight, apparently the pax loaded themselves and cargo in the nose bay and did I mention they were late? Tower reported 'a puff of smoke' but after cleaning up the runway agreed that it could have been a cloud of 'charts.'

Posted by: Thomas Connor | March 12, 2013 6:23 PM    Report this comment

Found the first link--their link to the NTSB is broken. The ASF report itself is still suspect--the garment bag was found at the end of the runway--so that would have no bearing on the inability to maintain flight. An open nose baggage door would also not cause the aircraft to become uncontrollable. There was no mention in the ASF link of charts. The ASF report says that the latches can be locked without the door being completely closed--I'd like to see someone do that--they are simple over-center latches, backed up by a key, backed up by a hook mechanism. The listed probable cause was "failure to maintain airspeed"--the inadequate preflight was only a contributing factor--not causal. Full text follows:

Posted by: jim hanson | March 13, 2013 5:59 PM    Report this comment


I completely agree with the stupidity of pilots yelling "clear"-then immediately hitting the switch. They do it without thinking.

Every day, I watch people doing stupid things--just yesterday, a pilot fueled his aircraft--came inside to get warm--then ran over the fueling ladder he forgot to remove. Towbars left on, and the engine started--attempting to taxi with chocks still in place (or worse yet, with tiedown ropes on). As the old saying goes--"there's a difference between genius and stupidity--genius has limits!" (laugh)

Posted by: jim hanson | March 13, 2013 6:07 PM    Report this comment


I completely agree with the stupidity of pilots yelling "clear"-then immediately hitting the switch. They do it without thinking.

Every day, I watch people doing stupid things--just yesterday, a pilot fueled his aircraft--came inside to get warm--then ran over the fueling ladder he forgot to remove. Towbars left on, and the engine started--attempting to taxi with chocks still in place (or worse yet, with tiedown ropes on). As the old saying goes--"there's a difference between genius and stupidity--genius has limits!" (laugh)

Posted by: jim hanson | March 13, 2013 6:09 PM    Report this comment

50 years ago--the operator at our airport had a fine for aeronautical transgressions. Minor items like failure to install control locks or secure the airplane were "six-pack offenses"--the guilty party was "fined" a six-pack--and after hours, everyone in attendance consumed the fine. Someone starting an airplane and blowing things around the hangar was fined TWO six-packs--and handed a broom to clean up. More serious offenses (leaving the mags on--leaving the master switch on) were "case offenses".

It was a gentle way of chiding the offender--"I saw you do something dangerous--I hope it won't happen again"--administered by the pilot peers. Pilots accepted it in good fun--but peer pressure IS effective--much more so than today's "I'm going to call the FAA on you" pilot to pilot.

Posted by: jim hanson | March 13, 2013 6:21 PM    Report this comment

I recently finished Robin Olds' biography 'Fighter Pilot.' He was a WWII and Viet Nam pilot and commander who found his way to the USAFA as commandant. He was appalled by the honor code and the way the cadets imposed it on one another as a means of control and getting ahead, not leadership and the mission.

As an example: Bob Pardo gained fame for 'pardo's push' airforce-magazine dot com/MagazineArchive/Pages/1996/October%201996/1096valor dot aspx

Olds was Bob Pardo's commander. Staff pukes at PACAF wanted to punish Pardo for 'making unauthorized contact with another aircraft,' forbidden by reg. Just to keep idle minds busy at PACAF, Olds put Pardo in for the Silver star. It took 20 years for good to prevail over evil, but Pardo finally got the medal.

I flew with a number of academy grads and it was easy to classify them by how they spoke of 'compliance' with whatever they thought important. Some tend to drive good people away by writing letters of reprimand for their file. Others turned punishment into a social event and learning experience by mandating a round of drinks at non-happy hour prices. Few remember the jerks. Everyone remembers the beer calls, and probably learned more.

Posted by: Thomas Connor | March 13, 2013 10:05 PM    Report this comment

Most pilots approve of peer pressure rather than "enforcement" for changing safety procedures. As always, there are a few that are negative--"Beer at an airport? I'm SHOCKED--SHHOCKED, I SAY!" (laugh)

I'm going to do a magazine article on the "six-pack" practice--I'll use the Olds/Pardo example you gave in the article--THANKS!

Posted by: jim hanson | March 14, 2013 9:37 AM    Report this comment

Your peer pressure comment reminded me of the B-52 crash at Fairchild AFB in '94. The ensuing USAF investigation determined that LTC Bud Holland (PIC) was responsible (hot-dogging) and this led to a thorough shakeup of safety and disciplinary procedures.

Posted by: Will Alibrandi | March 14, 2013 9:55 AM    Report this comment

Will: What did those safety changes entail?

Posted by: Thomas Connor | March 14, 2013 2:37 PM    Report this comment

More regulations.......

More discipline.................

Not nearly as effective as fellow pilots saying "I saw you do something stupid--I think you owe us a case of beer--and you can help drink it".

Most people that get the gentle disapproval--do penance--and after doing so, are absolved of their aeronautical transgressions by their fellow pilots don't make that mistake again.

Posted by: jim hanson | March 14, 2013 2:59 PM    Report this comment

In that particular case, LTC Holland was a serial abuser, and had been verbally admonished by superiors on several occasions for performing "stupid B-52 tricks" including over-stressing the airframe in a hammerhead leading to 500 popped rivets. I don't know if more regs or discipline was the result, but probably a change in leadership culture that wouldn't tolerate flat-hatters like Holland. I doubt the beer approach would have "fixed" a guy like Holland - probably just empowered him to continue his airborne recklessness. Sadly, he took three good men with him.

Posted by: Will Alibrandi | March 14, 2013 3:05 PM    Report this comment

There are some people that simply CAN'T be helped--and in those cases, it's a failure of his superiors to not only discipline--but to ground him.

On the other hand--many cultures throughout the world take care of people that do stupid things by "shunning" them--and it IS effective.

Being ostracized by fellow pilots for stupid behavior is one of the harshest and most effective methods of changing behavior--and disciplinary actions (as proven in this case) are NOT effective--short of removal.

Contrary to popular belief, people in the military rarely fight "for God and Country"--they do the perilous things they do so as to not let down their fellow soldiers--and when faced with someone that doesn't hold up their end of the bargain, that person has lost the respect of the rest of the unit.

Posted by: jim hanson | March 14, 2013 4:36 PM    Report this comment

There is some hand wringing at airfactsjournal about a perceived excessive GA accident rate and demand that we do something. I just posed the beer fine method of behavior modification and suggest we introduce it at OSH. It will be interesting how that blog reacts. You might want to chime in:
airfactsjournal dot com/2013/03/malibu-down/#comment-75515

Posted by: Thomas Connor | March 14, 2013 4:44 PM    Report this comment

Thanks, Tom--I took your advice and checked it out--I had forgotten what a good site it can be. I posted on it--and mentioned your observation on the military.

Posted by: jim hanson | March 14, 2013 6:04 PM    Report this comment

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