Carpe Propum! (Seize The Prop!)

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Show of hands: How many know how to start an airplane’s piston engine without using an electric starter? Follow up: How many believe that starting an engine by pulling the razor-sharp propeller blade through by hand is the stupidest thing anyone can do short of wearing a Top Gun flight suit in a Mooney?

Although most modern airplanes (post-1948) have electrical systems and starters, you’d think that hand propping would be passé. Except many pilots still do it, proudly and with impunity. They’d thumb their noses at those who don’t, but not all still have thumbs. Reported hand-starting accidents don’t claim a large swath of GA accident/incident stats with even fewer in the airline world. Usual culprits include not having the tail tied or wheels improperly chocked or a terrified passenger at the controls. They panic so easily.

Hand-propping misconceptions abound. First, propeller blades are not “razor sharp.” They’re more like lawn mower blades. Next, it’s not illegal, immoral or fattening to hand prop airplanes. Helicopters maybe. As for fattening, you’ll burn more calories trying to hand start a recalcitrant Franklin engine than you will pushing a starter button. As for the legality, I’ll avoid litigious toes here, but there’s no FAR that says thou shalt not start an engine by hand … or foot for that matter.

The Airplane Flying Handbook—touchstone of FAA intention—does warn that “(hand-propping) must be carried out only by competent persons who have been trained to accomplish the procedure.” Good luck finding a CFI who knows how to hand prop, which only leaves YouTube self-study. Failure is an option, and should you bung things up, the FAA may invoke broad authority under 91.13 (Careless, Reckless or Stupid) to clap you in irons. But fear of authority has no place in your flight kit so formulate a plan to prop safely … “safely” being a relative adverb.

There is no single correct way to hand-prop an engine. Likewise, there are countless chances to screw up. Propping a small engine is different from swinging the prop on a big radial, so we’ll stick with the four-cylinder Continentals commonly found on 1940s classics such as Cubs, Champs and Taylorcrafts. Many have been upgraded with electrical systems, but chances are if you’re considering a 65-HP engine, you’re fixin’ to start by hand the way Grandma did.

When hand-propping, it’s best to have a qualified someone inside the airplane with heels on the brakes, hand on the throttle and access to the magneto switch. Safety tip: Never trust the person at the controls. They’re psychopaths, longing to kill you as you touch the prop, so even if they claim, “switch is OFF,” don’t trust ‘em. Always treat the prop as though the mags are ON, and the 75-year-old switch is defective.

Starting my 65-HP Continental is easy. Prime it as you would most engines. Then, with the mag switch OFF, pull the prop through, assuming it might start. Never twist the prop using both hands. Six blades usually sucks enough gas and air into the cylinders. Seven floods it. Once primed, set the mag switch on, which might not be BOTH. If one mag has an impulse coupler to retard the spark for easier starting, select that magneto.

I prefer to swing the prop from behind with my right hand on the descending Guillotine™ blade, and my left holding the door frame. When propping from the front, don’t lean into the prop nor stand too far back; either compromises balance, inviting a Robespierre crewcut. And don’t get carried away (literally) swinging your leg up Hollywood-style. When propping from behind the propeller, my legs straddle the landing gear leg. With a primed engine it’s a quick snap, pulling the prop blade down and—real important—withdrawing your hand as the sparkplugs fire, and the prop blast blows your cap off. When that happens, let it go and ….

Do nothing. Don’t hurry to adjust the throttle, remove chocks or wave to bystanders, because any rash movement could lead into the spinning blades, and you’ll be unable to count on the fingers of one hand how many ways that was stupid. Back away from the fuselage by guiding yourself along the leading edge of the wing strut. Then, slip behind the strut and into the cockpit, where the pilot at the controls is once again a friend and not out to kill you.

Propping by yourself is not perfectly safe, but nothing fun is. Tying the tail down and chocking the wheels mitigates enough risk to make it acceptable. I have a set of wooden chocks, each with ropes attached. Once the tail is untied, I stand at the open door with engine at idle, fuel OFF and reach down from behind the wing strut—never from in front—and pull the rope to remove the right-side chocks. After tossing them aside, I pull a longer rope that hauls in the left chocks, like weighing anchor on a bass boat … not that I’ve ever done that. Leaving the fuel OFF for the half-minute it takes to unchock assures that should you suddenly drop dead of natural causes, the airplane will only taxi a short distance before the engine quits; possibly saving your estate unpleasant expenses.

If you get aggressive with the primer and flood the engine, turn the mag switch OFF, fully open the throttle and pull the prop through backwards 12 blades. Backwards, so the mags won’t fire; throttle wide open to theoretically suck the overly rich mixture from the cylinders. Return the throttle to idle or cracked and attempt a restart. Works almost every time.

Skills such as hand propping airplanes or operating a matchlock arquebus are invaluable in defiance of modern timidity. So, seek out the old CFI with the even older Cub and learn to prop wisely or you won’t qualify for the next show-of-hands survey.

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31 COMMENTS

  1. The biggest engine I have hand propped was a O470 on a C182. Lycomings are a little more difficult if the starter is still engaged from a failed starter or drained battery. I worked for a person who when he went into the navy in the early 1960’s, his navy aircraft maintenance instructor told him that a moving prop is the sharpest blade ever honed! I have always treated a prop that I was trying to start as such.

  2. I hand-prop when I have to, but I really don’t recommend it to anybody if it can be avoided. It’s one of the most dangerous things that you can ever do, and the consequences are permanent.

    – take your time securing the plane from rolling, preferably tied down and with chocks
    – set your controls correctly, especially the throttle friction lock
    – lean away from the prop
    – have your fingers slide away from the prop arc immediately.

    Don’t underestimate how badly this can turn it.

  3. My experience is that having another person around who is not well versed in the procedure is more dangerous than propping alone. At least they will be a distraction and at worst may do exactly the opposite of what you have just asked them to do.
    On the other hand, an experienced helper, either in the passenger seat or standing at the controls, or even better, if experienced enough, spinning the prop, is a huge benefit.
    This means that if I have an inexperienced passenger, I will FIND an experienced helper.

  4. Hi Paul,
    Great subject to cover. As a geezer Flight Instructor I’m aware of too many hand propping deals gone bad and have actually witnessed one.
    Couple’a years ago, came across a guy who’d just gotten a tailwheel signoff in a Champ. They’d never taught him how to hand prop.
    So I developed a syllabus on Hand propping and spent an afternoon with him. When you start thinking about it, there is a rather long list of details to cover. Perhaps I’ll go more active with this in the future.

  5. I worked ramp in my younger days, and have propped a lot, R1350, R985 (both easy), and high horsepower I/O’s (not so easy), but I ran into one that I thought about, but declined to even try, it was a 200hp Mooney M21, too low, too much compression, a killer. No one else would try it either, so we got it a jump start and lived another day.

  6. Good article. The priming for start and unwinding if flooded match my A65 exactly. Can’t emphasize enough, CLOSE THE THROTTLE after doing the one dozen unflooding backwards blades before trying to start again. In my Aeronca Chief, because getting in and out of the plane is pretty difficult for most of today’s sized persons, I don’t want anyone in the cockpit when I start the engine unless that person is going to be a passenger on this flight. Otherwise, if no tie down available, I set the brakes, lock the throttle cracked barely, and have a person stand at the cockpit door. I then in the simplest terms possible tell them, “Here is the ignition switch. I want you to put your hand on it. After I start the engine, if the plane begins to move AT ALL, just go click, click, click with the switch to turn the motor off. Now, let’s do the switch like I showed you once.” With that, I feel comfortable hand propping it even with a non pilot doing switch guard…if I’ve judged them as a capable individual otherwise. With a parking brake and locking throttle, I prefer to not use the chocks because of proximity of the spinning blade when removing them. On an A65, don’t forget to check the oil pressure before you go about doing other things.

  7. When I restored my Champ, I installed a parking brake for just this reason. Very simple install with hydraulic brakes. Electrical systems with starters and batteries and then radios and now ADS-B (OMG) in a Champ just adds weight. I too hand prop from the rear.

  8. When I moved from Kansas City to Houston, I had to leave the plane behind for a few months. (Hawk XP Cessna 172 with the high compression IO-360-KB engine.) When I went back to get it, the battery was flat. I asked the old man at the airport if external power was available. He said external power starts cost twenty bucks, but if I claimed to be good at starting the engine he would hand prop it for free. Crazy old man. If it was my airport, external power would be free and a hand prop would cost a hundred bucks. But it was his airport, so he threw the prop around, and I got the engine started on the first try, and I was off to Houston.

  9. You cannot trust the airplane either. I propped a C-210 several years ago. Being paranoid, I had the pilot place the keys on the panel where I could see them while I pulled the prop through several times. Then as I moved the prop forward to position it for a good pull, the engine fired. Surprised the hell out of me, fortunately my practice was always to move away from the prop and never allow any body parts to get in its arc. The keys were still right there on the panel….bad P-lead.

  10. Pilot/ Owner: Have you ever done this before?
    Helper: Not really, but I’ve watched a Youtube video on how to do it.

    I remember my grandfather handpropping our 172 in the winter to solve for a flat battery when I was still taking lessons. He had done it thousands of times…

    He was extremely adamant about procedure and never propped anything with three blades or composite props. Always a pro and it being cold, a small nick in the prop got stuck on his whool gloves, which fortunately pulled straight off his hands.

    You should have seen my face when that black glove flew straight up towards the sky as this engine attempted a few revolutions of having fired. On the way home we talked about this incident and I got a lesson about humility and complacency from a old bird…

    • I once had a reason to turn a prop slowly through with the mags hot (I can’t remember why). The fuel was off and the mixture was in cut-off and the engine was cold. Expecting that it MIGHT catch, I was fully ready to yank my hand back. It DID catch but I couldn’t get my hand back fast enough … it wound up hitting me. No damage … I still have all my parts but I did get a bruise. The moral of the story … if you’re gonna turn a prop over by hand, know what you’re doing and be careful. You can’t get your hand away fast enough if it starts.

      This points to another safety action. Mechanics are supposed to check mag grounding but … I wonder how many actually do it. Once in a while, it’d be wise to check that you can shut an engine down with the mag switch … just don’t do it at high RPM unless you want to buy a new exhaust system when it back fires.

      • Shouldn’t wise pilots check for mag grounding on every flight or at least once a day? I do it every time as I am taxiing back or before shutdown. All it takes is to quickly turn the switch from L-R-OFF-Both at idle. If a mag isn’t grounded the engine still runs at the OFF position . . . that’s a hot mag.

        Let’s not put this burden on a mechanic when the pilot can check it too.

        • I don’t disagree but I doubt seriously that you’ll find such an action in many shut down lists. Further — and as I said — that’s a good way to blow an exhaust system if you don’t do it right and fast. I’ve had to retrieve C152’s for fouled plugs because student pilots couldn’t figure out how to lean the mixture so why would we think they’d successfully check for mag grounding ??

  11. You’re telling people to turn the engine backwards 12 blades if you flood an engine. That’s fine for your Cub but there are people here who have more serious engines that have vacuum pumps. DON’T turn an engine backward if you have a vacuum pump … unless you like buying vacuum pumps more often than is already necessary. Just let it sit for a while and try again. I sometimes use a SMALL shot of starting fluid on persnickety engines … just don’t get carried away. And even in Florida, rigging something up to pre-warm the engine would help, as well.

    • Turning engines backwards is can be a good idea and doesn’t ruin vacuum pumps. “DON’T turn and engine backwards” falls in the category of an old wives tale.

      Where I work we teach our pilots to turn the prop backwards through each cylinder during the preflight. We want them to feel the compression of each cylinder and listen for any leaking (cracked) cylinders. We fly mostly big bore Continentals in C-185, 206, 207 and 210s. In my 30 years and tens of thousands of hours where I work I am not aware of this ruining a vacuum pump in our fleet.

      On my personal plane with a Continental IO-240 I turn the prop backwards 4 blades every preflight. It doesn’t have a vacuum pump, but even if it did I would do this.

      • I say potaytoh …and you say potahtoe … if it makes you happy … knock yourself out.

        And what exactly are you doing by turning your IO-240 backwards four blades … inquiring Master Mechanics want to know …

        • Already stated in my first post . . . I am checking that there is cylinder compression, no dead cylinder/leaking valves/possible cracked cylinder head. I have also seen compression increase as the cylinders get oiled.

          Where I work we have found several cracked cylinders on the big bore engines during pre-flights. This would not have been found till the next inspection.

          It sure seems like a good idea to me. It’s safe if you turn the prop backwards. BTW, I have also confirmed no hot mags by doing a mag grounding check at the previous shutdown. I also observe the idle mixture RPM rise at shutdown.

          Some of these things may be beyond the level for student pilots, but what about aircraft owners, professional pilots, CFIs, etc.

          • I missed your comment about “feeling for compression” in your first comment. As soon as I read you were turning the engine backwards … I saw red. Turning an engine over to feel for compression — in and as of itself — IS something that can be done but usually isn’t necessary. Small Continentals with sticking valves can be unstuck by shoving rope into the cylinder and slowly and carefully turning the piston into the valve, too … but I don’t recommend people doing it. As I said … if your employer or you feel better … knock yourself out.

            From time immemorial over millions and millions of flight hours, however, a power check prior to takeoff has served to verify proper engine operation. I feel it’s bad business to be teaching students or non-mechanically inclined pilots to do stuff like that. An engine receiving 25 hr look sees, 100 hr and annual inspections should be checked for head to barrel leaks, compression checked and — these days — bore scoped. In between, I don’t feel it’s necessary. Many pilots don’t even understand how to run the fuel system of those larger engines much less be turning ’em over looking for leaks.

            AND … I have news for you … the Univ of N. Dakota A&P school PURPOSELY built up an engine without rings to see what would happen. Guess what … it ran and produced almost full power … albeit spewing a lot of oil. I forget how long they ran it … maybe someone here knows ? And as soon as you try to tell me you’re seeing cylinder compression increase by turning the engine backward because you’ve pre oiled it … I don’t even know what to say other than … BRAVO SIERRA !

            There is NO WAY you will convince me you can find a leaking valve or even a cylinder to barrel leak from a cowled engine by turning it backwards. Feeling for compression generally … maybe. But HOW will you tell the difference between — say — a cylinder producing 78/80 and one producing 60/80. I’ve got a six pack of beer that says you can’t do that. Anything worse than that and it’ll show up in a power check at the runway.

            As to vacuum pumps, as they age carbon material wearing off the vanes starts building up and causing sticking vanes. Turning a sticking pump in the reverse direction could break a vane. If you think it’s OK and then go flying IFR … without a backup vacuum system or some other way to figure out which way is up … just make sure your life insurance policy is paid up. You’re playing Russian roulette.

  12. Many years ago I learned to hand prop a J-3. It belonged to a CFI who used it for a comedy act at airshows.I was the only pilot in the area that he thought competent enough with conventional gear to be allowed to fly it. He would rent it to me for $9 an hour wet.

  13. If the battery is dead take it out and get it properly charged with a good charger. You will dramatically reduce the life of the battery if you hand prop an airplane with a dead battery as the voltage regulator will slam it with a massive amount of amps as soon as the engine starts

    All my commercial students who were going to bush or float jobs got a lesson on hand propping so they had an option if they got stuck with a dead battery in a bad place. But I emphasized this was an emergency get home deal, not something you want to make a habit of

    I never move a prop without thinking the engine may start and I cringe when I see so many pilots level the prop by wrapping their hand right around the blade

    The last time I hand propped a plane it was a Nanchang. There was no air pressure for the starter so we chocked and tied down the plane and I primed the cylinders and then felt for a clylinder to go TDC. I then told the pilot to hit the boost coil and it banged right away with the owner chatching it with a shot of prime. A hand start without touching the prop, it doesn’t get better than that !

    • You are exactly correct about the batteries, David.

      NOW we’re on a subject that is near and dear to my heart (and wallet). This blog started talking about hand propping a non-electrical airplane but MOST hand propping situations occur because the starting battery went dead. And that happens because they weren’t cared for … one way or another.

      The second you stop charging a battery — especially a flooded lead-acid battery — it starts to sulfate. Don’t believe me … ask Chris Holder of Concorde Battery and tell him Larry sent you. Newer AGM batteries are less prone but still sulfate, as well … just slower. There is only one way to keep a battery from doing that … keep a trickle charger on it. If you keep a battery above it’s natural fully charged when new voltage (e.g., 12.9V), it won’t sulfate. Aircraft batteries are purposely built differently than auto batteries because of weight and size limitations so don’t go putting a 100A ‘quick’ charger on an aircraft battery that sits for months on end. In effect, that’s what you’re doing when you hand prop an airplane with a dead battery, as you said. And even a tiny trickle charger can fry and ruin an aircraft battery over time IF the output voltage is too high. The “magic” number is 0.5 volts above a battery’s fully charged voltage. Lower is better than higher. You don’t need to spend $200 for one of those fancy chargers that sense temperature IF you carefully pick the charger you use. I have a bunch of cheap chargers from a certain Freight store; I just make sure I hand pick ’em. If you have a 24V airplane, you’re limited so you have to spend more money on a charger.

      As batteries sulfate, the portion of individual plates that become inactive increases. Charging will reverse some of that but — over time — that’s one of the things that kills a battery. Parasitic loads (an old Cessna mechanical clock) can pull a battery down fairly quickly and add to the problem. Leaving a battery sit in a discharged state also is a no no. People with panels full of TV sets who like to play with them should ALWAYS find a way to run the airplane from an external power source and not run off the battery for anything shorter than a few minutes. When done, make sure the battery is fully re-charged.

      I tell people that the magic number for a 12v battery (aircraft OR auto) is not to trickle charge the battery above 0.5V above 12.9V = 13.4V. IF you can find a trickle charger that’ll do that, find a way to modify the airplane to directly charge the battery (NOT through the master solenoid). I recently had to repair a C150 that had a master solenoid short out internally and try to melt the battery, box and even airplane. Anything higher than 0.5V above a battery’s natural fully charged state harms it in other ways over time.

      So here’s the proof of the pudding. I have a 1997 F250 truck that only has 16K miles on it and is rarely driven. It’s only on its second battery which is now — are ya ready — 14 years old. It’s now a game to see how long I can keep it usable. I keep its battery on a trickle charge hand picked to provide 13.4V and it sits that way 24/7/365 unless I’m going to start it up. The first battery lasted 10 years because during its first few years I didn’t do that. Darn! One more thing. Batteries made with pure virgin lead vs old ground up WalMart batteries should be sought out even at higher cost.

      I’m a snowbird these days. When I head south I bring my maroon colored AGM airplane battery back with me by car. It’s sitting in the back bedroom on a hand picked charger providing 13.1V. That way, I’m keeping it above it’s fully charged natural voltage and am not frying it as it sits waiting to head back north.

      For those without the ability to plug a charger in, I’d offer that you should rig up a solar charger. And if you live in a cold environment, try to heat the battery up along with the engine (easy on many Cessnas) … a warm battery will put out far more “juice” than a cold one.

  14. Several years ago I gave a hand-propping demo at the Cessna 150-152 Fly-In (in Clinton, IA every July – sign up today!) Before giving the demo I studied the NTSB reports on hand-propping incidents and accidents. I found very few injuries, but I found lots of airplanes that ran away from their pilot. One plane took off and flew away over the horizon. It wasn’t found for a week.

    But my favorite story is a husband-and-wife team that built their own experimental. He would be sitting at the controls while she spun the prop. As one witness put it, it was clear she knew what she was doing. They were a practiced team. This time, the plane didn’t start right away so she started to turn the prop backwards. At that point a local man walked over, told the wife “I’ll take it from here” and despite the husband’s protestations, swung the blade. It kicked back and knocked the guy down. The full narrative includes a lot more detail and funny witness statements. You can read it by Googling NYC97LA106.

  15. I can’t believe the number of people here who claim not to do a live mag check. In our neck of the woods that little interruption in the sound of an idling engine is a standard thing you hear during shutdown. It’s certainly part of our shutdown checklist, and I’ve detected a broken P-lead that way.

    As for hand-propping, my favourite story is from the time I was flying skydivers in a Cessna 170. One day the battery was dead and I hand-propped it all day. No big deal, and there was always someone nearby who was qualified to hold the brakes and throttle. But then I had to go over to the local airport for fuel. The only people around were an impeccably-dressed couple about to launch in their Aero Commander for parts unknown. This fellow is probably still telling his friends about the time he climbed into a ratty old 170 to hold brakes and throttle while some freak wearing a parachute was pulling on the prop…

  16. I, too, have hand propping stories. Skipping those – dead battery 7ECA, and broke P-lead on an 0-470, and a Kinner that bit a friend — I will run to my pet peeve. Allowing anyone to touch a prop and taking a photo of same. AVWeb, as a publishing outlet, PLEASE don’t print photos of folks hangin on props. My ‘no prop-touching’ briefing occurs almost weekly on GA airfields. The countless ways that an engine can cough over and guillotine body parts is amazing. If we were all taught to not touch props (unless knowlegably hand propping) and didn’t have the Sports Illustrated or GenAv Calendar girls background of prop-hugging, perhaps there would be a couple more fingers we could wave in automobile traffic. Hand rotating props. Bad ju-ju. Thanks for the minute’s indulgence…….

  17. It would never get past the inspectors now, but in Rhodesia, in the 1960s, there were at least two Cessnas on farms with modifications which allowed a rope start, similar to a lawnmower.
    One end of the rope, with a knot in a notch in a pulley, I think half a wind, and the other end on a tractor or landrover.
    The story goes it was developed after a much loved farmer managed to get himself chopped in half by trying to do it by hand…

  18. At the drop zone where I did most of my hand-propping, it was SOP to not only switch the mags off, but to leave the keys on the dashboard where the guy pulling the prop could see them. Still, that wouldn’t protect you against a broken P-lead.

    The best advice anyone gave me was to treat a propeller the same as you would a loaded gun.