AVweb AVFlash - FRIDAY FEATURES
It used to be self-fueling just referred to the aircraft owner who brought mogas to her airplane in five-gallon cans and upset the airport manager or FBO because of lost fuel sales. While that’s still the case, over the last decade, it’s also come to mean putting avgas into your airplane from a self-service pump.
Watching both sorts of self-fueling has caused us concern on two levels. First, even now, a lot of aircraft owners and airport operators don’t know that it’s perfectly legal for an aircraft owner to bring fuel onto an airport to fuel his or her own airplane (subject to reasonable safety rules) and, second, that the process of fueling an airplane, no matter what the method, has safety concerns that need to be considered. No matter what type of self-fueling you’re doing, it isn’t just filling up your car at the convenience store.
For decades, some aircraft owners have opted to seek their own supply of fuel. On some airports, it’s a necessity, because there is no fuel concession. In other cases STCs for automotive fuel (mogas) meant an owner could cut a nice chuck out of the operating costs of his or her airplane by buying ethanol-free mogas and transporting it to the airport in five-gallon containers or the classic tank in the bed of a pickup truck. In other cases, corporate owners of airplanes decided they wanted their own tank or fuel farm near their hangar—so they could buy in bulk and keep costs down.
Naturally, aircraft owners who supply their own fuel are not going to be popular with the fuel concession on the airport. It’s not unusual for an airport sponsor—the entity that owns the airport—to pass rules to prohibit this type of self-fueling or put onerous restrictions on it.
The good news is that federal law clearly allows self-fueling by aircraft owners—subject to reasonable safety rules. If the airport sponsor has accepted federal funds under the Airport Improvement Plan established under 49 USC §47101 (most have), it signed a contract, known as grant assurances. It is obligated to take certain actions in running the airport—one of which is allow an aircraft owner to provide fuel for his or her own (but not any one else’s) airplane. The airport sponsor can impose reasonable safety rules, but they cannot be so onerous as to effectively deny self-fueling.
Given the danger of hangar fires, reasonable rules on the type of container required for storing fuel in a hangar are sensible (there are five-gallon gas cans safely stored in hundreds of thousands of American garages). A ban on storing flammable fluids in hangars is probably unreasonable because no one could keep cans of oil or cleaning materials in a hangar—something done routinely and safely.
If you want to read a detailed discussion of self-fueling, there is an FAA Director’s Determination in the case of Brown Transport Co. v. City of Holland, Michigan (FAA Docket 16-05-09). The airport sponsor required a $1 million cash bond on top of liability insurance for an airplane owner to self-fuel. The FAA made it clear that the bond requirement was unreasonable.
We’ve been self-fueling our cars for a lot of years. We generally do pretty well—unless we are smoking or leave the engine running, the two most common causes of fires at self-serve service stations. Yes, those signs by the pumps are there for a reason. Cars do get crispy-crittered when incredibly basic cautions are ignored.
Airplane self-fueling presents a slightly different risk. We did not find evidence that pilots had managed to set airplanes on fire via cigarette or leaving the engine running while self-fueling.
The risk in any refueling exercise is a spark that ignites fuel vapor—and it’s the vapor part of fuel that explodes in the cylinder to provide the power we need to fly. We’ll not go into the sheer energy locked up in avgas and jet fuel, but will point out that avgas has a flash point—temperature above which the liquid produces ignitable vapor—of -40 degrees F. Therefore, you’re dealing with vapors that will blow up just about any time you’re dealing with avgas. For jet fuel the temperature is 100 degrees F.
If there is liquid fuel on the ground—say after a spill—and the vapors ignite, the flame front for jet fuel moves at a paltry 100 feet per minute. Avgas is much faster, just over eight MPH. What kind of shape are you in?
Jet fuel will autoignite at something between 410 and 475 degrees F. That means if it spills on something that hot, it will start burning. Avgas autognites at 842 degrees F—the temperature of an exhaust pipe or turbocharger after it has cooled down a bit. (Do you really want to hot fuel?)
With all of that background, the big risk for sparking off a fire while fueling is static electricity. Airplanes build up a static charge flying through the air. A liquid, such as fuel, builds up a static charge when flowing through a hose or tube. Let’s keep that in mind as we think about what we do when we taxi up to the self-service fuel facility on our airport.
Rather than anxiously hustle up to the credit card machine, wondering if you can make the thing work or if it will take your card, take a few moments to eyeball the ramp and facilities. Which way is the wind blowing? That’s your exit route if something goes wrong. Is it there a way to get away upwind, or is there a fence or something else blocking the route. Is there a comfortable place, upwind, for your passengers to wait while you fuel the airplane?
Where is the emergency fuel shutoff? The deadman that is supposed to shut off the fuel at the nozzle has been known to fail. Where is the fire extinguisher? It may not be big enough to put out a fire, but it can be a good emergency exit maker if you need to smash out a window.
Is the airplane level? If not, you may not be able to fill all the tanks completely. That may be a big deal in determining how much fuel you really have on board on airplanes with long, slender fuel tanks in wings with little dihedral, such a Cessna 210. In some airplanes you’ll need to position the fuel selector to the left or right tank to avoid draining fuel from one tank to another and then onto the ramp during fueling.
The next step is to hook up the grounding or bonding wire (it’s the same thing, the name varies by whether you are electrically grounding the airplane or bonding it to the fuel delivery unit). Remember where it is, as it could trip you if you are trying to boogey out of there in the event of a fire.
Then go wrestle with the credit card machine and get the pump activated.
With the fuel hose and nozzle in hand, touch some portion of the airplane before you touch the fuel cap. The bonding wire should have taken care of things, but this is just extra protection against a static discharge and spark—and there may be fuel vapor in the vicinity of the fuel cap.
When fueling, keep the nozzle in contact with the airplane. This helps keep the fuel delivery system and airplane electrically bonded.
Because aircraft fuel systems deliver fuel at a much higher rate than the system for your car at the convenience store, static buildup is a concern as the fuel scoots through the hose and nozzle. The condition is made worse in conditions of low humidity.
Back in the 1970s when nobody seemed to either understand or care about fueling safety, a close friend was working as a lineman at an FBO. Of course he didn’t hook up the grounding wire from the truck before starting to fill up a Cessna 42l. After putting about 80 gallons into the airplane, the static electricity buildup between the airplane and truck discharged, blowing him off the ramp. He landed about 10 feet away, with injuries. Fortunately, the wind was blowing the vapors that were escaping from the filler opening away from the spot where the discharge occurred and there was no ignition.
You can aggravate the risk of static discharge by wearing nylon or polyester clothing due to its propensity for static buildup. We have heard anecdotal evidence of fires caused by pilots using plastic fuel tank dip sticks, wiping them on their nylon flight jackets, then starting to insert them into the tank and having the static discharge, spark and ignite the fumes coming out of the filler opening.
As an aside—because nylon melts and sticks to the skin, exacerbating burns during a fire—don’t wear nylon when flying. If you have a nylon flight jacket, we suggest you give it to someone who doesn’t fly or simply don’t wear it during flight. There is a reason leather flight jackets have remained popular beyond their good looks.
When fueling directly from fuel containers, plastic or metal, it’s a good idea to keep the spout in contact with the fuel filler opening. Airplanes have safely been fueled from portable fuel containers for over 100 years, so it puzzles us when airport operators get worked up about them. The relatively small, five-gallon container doesn’t hold enough fuel to create a high risk of static buildup while it’s flowing, but it doesn’t hurt to be careful.
If something goes wrong and you have a spill resulting in a puddle of fuel, don’t start the airplane. It’s an invitation to a Darwin Award. Follow the contact instructions that should be on the sign giving instructions for fueling and get help to clean up your mess.
Otherwise, once you’ve got the fuel level desired in the tanks, confirm you’ve secured the caps, stow the fuel hose and nozzle (so water won’t get in it) and grounding wire, gasp at the charge on the credit card receipt and press on.
Oh, and please, don’t blow gravel all over the airplane behind you when you start up.
I last wrote about this subject about 18 months ago (Savvy Aviator #37), but it seems as if jugs are still coming off needlessly, so perhaps it's time to revisit the subject. Each week, I receive dozens of emails from aircraft owners seeking advice on maintenance. I really enjoy helping fellow aircraft owners, but I often get frustrated by some of the poor advice they get from their mechanics. Take this one, for example:
"Mike, I really enjoy reading your column. I'm having a problem and need some advice. My airplane is in for annual and for the second year in a row my TCM IO-520 engine has some low compressions. The compression test was done hot (or at least that's what I'm told). The IA is going to do another compression check today, cold, but I don't think that is going to change anything. "He said the leaks seem to be from the exhaust valves. I looked at the exhaust valve of the lowest-compression cylinder through a borescope, and the valve was red in color. The IA said that is because it's run too hot, and suggested that the culprit was my use of lean-of-peak mixture settings in cruise. "I fly about 100 hours a year. Most of my trips are about four hours long. I usually cruise between 8000 and 9000 feet. My power settings, at 8,000 feet, are about 22 inches at about 2400 RPM. I lean to peak on my JPI 700, then go about 15 degrees F lean of peak. My hottest CHT is never above 380 degrees F. What am I doing wrong when flying this airplane?"
I told this owner that he's getting flawed advice from his IA. For one thing, the owner isn't doing anything wrong. Fifteen degrees F lean of peak and CHTs below 380 degrees F are exactly where this normally-aspirated engine should be operated at 8000 to 9000 feet. He's doing a great job of powerplant management. For another, an exhaust valve is supposed to be red! The red color is from exhaust deposits on the face of the valve, and such deposits are perfectly normal. In fact, the cooler the valve is operating, the thicker the deposits and the more intensely red the valve appears. It's actually the absence of red deposits that tells us the valve is heat-damaged and leaking.
The key to whether or not the valve is burned is the appearance of those red deposits. On a normal valve, when viewed with the borescope (see photo at right), the red deposits have a relatively symmetrical appearance, with the redness most pronounced in the center of the valve face and less pronounced toward the edges of the valve face. That's because the valve face runs coolest at the center (where it's thickest and its heat is well-sinked by the valve stem), and hottest at the edges (where it's thinnest and not so well heat-sinked). The hotter the valve, the less red deposits there are; the cooler the valve, the more red deposits there are. In other words, red means cool and the absence of red means hot! (I know this sounds counterintuitive, because we're used to thinking of red and hot as being associated, but in this case it's non-red and hot that are associated!)
If the valve is leaking, there will be one (or sometimes two) hot-spots around the circumference of the valve face where almost all the red deposits are gone and you see gray metal. The red exhaust deposits will have an asymmetrical appearance (see photo at right), with the hot-spots identified as being where the valve is least red.
If the borescope inspection shows a valve with a normal-looking, symmetrical pattern of red deposits and no obvious hot spots, I would not authorize the mechanic to remove the cylinder. I would go fly it for a few hours and then repeat the compression test. (Preferably have another mechanic do the test.) To be on the safe side, I would continue to inspect the valve with a borescope every 50 hours (at each oil change). Since the aircraft has a digital engine monitor, I would also suggest keeping a close eye on the EGTs. Always place your engine monitor in its "normalize mode" when in cruise flight. This will level all the EGT bars at mid-scale and increase the sensitivity, so that small EGT variations become very obvious. If the exhaust valve is leaking in flight, you will see it on the engine monitor (provided it is in normalize mode). The classic signature of a leaking exhaust valve is a slow EGT oscillation of 30 degrees F to 60 degrees F that occurs about once or twice a minute (see graphic at right). Any time you see something like this, immediately borescope the cylinder and check the valve. In my experience, a burned valve becomes detectable under the borescope (via asymmetrical exhaust-deposits revealing a well-defined hot-spot or two) at least 100 hours before the valve actually reaches the point of failure. The engine monitor will also detect the problem, but with somewhat less lead time -- perhaps 10 to 25 hours before failure. Consequently, I believe that regular borescope inspections should be the first line of defense in detecting incipient exhaust-valve problems, with the engine monitor used as a backup. The use of regular boroscopy in piston-aircraft engine maintenance is relatively new, and many mechanics don't really understand what to look for. They almost certainly received no training on this in A&P school. Consequently, before authorizing a mechanic to pull a cylinder off your engine, you would be wise to do what this owner did: Seek a second opinion.
The same owner emailed me a follow-up question:
"Is there any regulation as to the minimum compression on a cylinder in order to pass an annual? My IA tells me the engine should not have passed the last annual because of low compressions."
Excellent question! Yes, there sure is. The applicable regulation -- 14 CFR Part 43 Appendix D (Scope and Detail of Annual and 100-Hour Inspections) -- states that an IA is required to perform a compression check at each annual and 100-hour inspection. It goes on to say that if "weak compression" is found, the IA must perform an internal cylinder inspection to ascertain the reason for the weak compression. The FARs do not define the term "weak compression." FAA Advisory Circular AC43.13-1B (Acceptable Methods, Techniques and Practices -- Aircraft Inspection and Repair) suggests that compression readings below 60/80 are considered "weak," but this default FAA guidance is superseded by any specific guidance offered by the engine manufacturer. Because both Lycoming and Continental (previously TCM) do offer specific guidance, AC43.13-1B is moot. Lycoming's guidance is that the inspecting mechanic should "consider" removing the cylinder if its compression is below 60/80, or if there is more than a 10-point spread between the highest and lowest cylinder. Lycoming also encourages (but does not require) mechanics to use borescope inspections to help assess cylinder condition. Lycoming's use of the word "consider" appears to give the IA some wiggle room, but most IAs will take the position that a Lycoming cylinder with compression below 60/80 has to come off. Continental's guidance is very different from Lycoming's. Continental's guidance appears in Service Bulletin SB03-3, which in my opinion is the best guidance ever written on the subject of determining cylinder condition. Every Continental owner should download a copy (by clicking on that link) and read it carefully. If you do that, you'll find that Continental says that the minimum acceptable compression reading is to be established using a "master-orifice tool" hooked up to the mechanic's compression test gauges. For most compression test gauges we've checked, the master-orifice tool sets the no-go limit between 41/80 and 43/80. However, each gauge is supposed to be calibrated with the tool prior to each compression test. (Nowadays, many compression test gauges come with the master-orifice tool built right in, so calibration is done simply by flipping a valve.) SB03-3 goes on to say that even if a cylinder indicates a compression reading lower than the no-go limit, the IA is supposed to inspect the cylinder with a borescope to determine the cause of the problem. If the borescope inspection fails to reveal a problem, then the cylinder should not be removed. Instead, the engine should be flown for at least 45 minutes (preferably a lot longer) and then the compression test repeated.
Armed with my advice and a copy of Continental service bulletin SB03-3, the owner had a heart-to-heart conversation with his IA, and then reported back to me with the following:
"The IA just called and said that he has completed the annual, and agreed not to pull the cylinder. He said to fly the airplane for 25 hours and he will then recheck the compressions. I feel half afraid to fly the thing."
I advised the owner not to be scared to fly the airplane. Low compression never made anyone fall out of the sky. In fact, before issuing SB03-3, Continental actually ran some dynamometer tests in its test cell that showed an engine with all cylinders having 40/80 compression will make full-rated power. An engine with such low compression will also blow lots of oil out the breather and onto the belly of the aircraft, and will make what's left of the oil in the crankcase filthy in short order, but there will be little or no perceptible difference in performance, and certainly no safety-of-flight issues. An in-flight failure of an exhaust valve is no laughing matter. But as long as the exhaust valve looks normal under the borescope, you can be confident that it's not in imminent danger of failing. Regular borescope inspections, backed up by a digital engine monitor, will reliably detect exhaust-valve problems before they pose a safety hazard. I'm not suggesting that compression readings in the 40s are fine, nor that they should be ignored. Such low compressions are often associated with excessive blow-by that contaminates the oil with combustion byproducts and turns it acidic and corrosive -- not exactly the ideal environment for your expensive crankshaft and camshaft to live in. But such compressions will not cause any perceptible change in engine power or performance, and certainly won't make you fall out of the sky. So it's something to be concerned about, not something to be scared of. With such low compressions, it would certainly be prudent to re-check the compression and re-borescope the cylinder in 25 hours. If the compression continues to deteriorate or the borescope reveals the obvious visual signature of a burned valve or worn barrel, then the jug probably does need to come off for repair or replacement. In the meantime, however, the owner should have no qualms about continuing to fly the aircraft.
The photo on this page has been kicking around my inbox for more than a year, having been sent to me by someone asking if it depicted a real event. Given that we live in a world where Photoshop is a verb, it’s a perfectly logical question.
As you’ll see from today’s video, the photo is quite real and depicts Clay Lacy’s fanciful flight of The Human Fly on the roof of a DC-8 in 1976. I vaguely recall the actual event, but if it got much publicity at the time, the memory of it seems to have been lost to the years, so I decided to phone Lacy for the background. As with everything in Lacy’s career, the backstory is interesting, the result of just the right alignment of having an airplane available, an airshow to promote, an ever-willing stuntman and a sponsor to pay for it all.
Although the video doesn’t explain it, the Human Fly’s benefactor was a pair a brothers in Montreal who owned a prosperous Pepperoni factory but were a tad bored with the sausage business. So they raised $200,000 and formed a promotional company of which the Human Fly was only the opening act. The DC-8 version of the Fly was Rick Rojatt, but the brothers apparently envisioned garbing others in the Fly’s disco-style red suit, it being 1976 after all, for all sorts of stunts. They planned a rocket flight across the English Channel and a swan dive from the CN tower in Toronto.
Lacy got the easy part. He happened to have a DC-8 available, thanks to an Alan Paulson deal to remarket a handful of retired JAL aircraft. Lacy knew enough people in the Washington side of the FAA to grease the approval wheels and in a few weeks time, he had the world’s only DC-8 with an external seat. Actually a perch, I suppose.
Would today’s FAA go for such a thing? Hard to imagine. In 1976, all the feds could think of to slow down the Human Fly project was to require a maintenance program, which Lacy was able to pull together relatively easily. But at least in those days, someone in the FAA would actually at least tell you what was required. Today, good luck.
The Human Fly act was but a page in a chapter of Lacy’s stunning and long career in aviation. He’s very much the last of a breed whose experience bridges the world of piston and jet aircraft. His book, Lucky Me, has him photographed with everyone who’s anyone in aviation, from World War II aces to moon walkers. Lacy did stints as a military pilot, a test pilot, air racer and airline pilot and he’s yet active today in the industry from his headquarters at Van Nuys Airport.
Although most of us probably can’t list Lacy’s considerable achievements, we probably see them every day. When the Learjet first appeared in the mid-1960s, Lacy saw not just a fast, appealing business jet, but a camera platform that could shoot anything that flew. Thus was born Astrovision, the sophisticated camera system used to shoot movies and high-end commercials of airliners sailing into the sunrise. You can see early Astrovision at work in the Human Fly video.
Computer-generated imagery has put a dent in that business, but real footage is sometimes still cheaper than CGI. “That’s especially true if you want the ground in the shot,” Lacy told me. “It costs hundreds of thousands to do that with CGI, but for an airline commercial, they can rent the 747 and me for less than $100,000.”
Which brings us full circle. Today, the Human Fly could be a CGI project, but what a thrill to know it wasn’t.
In 1976, famed aviation businessman and movie pilot Clay Lacy was asked to fly one of the strangest stunt acts in aviation: The Human Fly. In this exclusive AVweb video, he explains how the project came into being.
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