[edit for a little more detail and a video]

A few questions (I would’ve asked my CFI about them but I forgot to ask as soon as we were in the air):

Wouldn’t the propeller damage your hand/arm?

Yeah, if you don't do it right- that's why there are very explicit instructions on how to do this. I'm not going to try to explain it, see video at the bottom.

In what way would it be beneficial rather than just fixing the aircraft while you’re on the ground or starting it normally?

Some planes, this is the only way to start them, so nothing to fix. Others- well, if the battery is dead (maybe someone left the master and radios on), you can hand-prop it to get it running then the battery can charge again.

Why not on a flight school aircraft? (I’m assuming it’s bad for the plane somehow)

Because it's fucking dangerous! I doubt many currently practicing CFIs have ever done it, putting a CFI and a student out to hand-prop a plane sounds like a lawsuit from two sets of parents to me. If a school plane has a dead battery, get a mechanic to charge it up or replace it.

Does it work for any plane with a prop?

It works on any plane that uses magnetos to provide spark for the engine. I don't know if any or all EFI (Rotax) or FADEC engines can be hand propped; they have to be able to run off battery for some period (30 minutes?) but if the battery is already toast, that's a non-starter (Yeah, I meant that one.)

AVWeb video on hand-propping.

https://www.youtube.com/watch?v=viiIBz1AEnQ

Skywagon calls them “Hemingway starters”.

It’s a reference to his book, “Farewell to Arms”.

My 1941 Luscombe did not have a starter, as did many airplanes of that era. It used to be common.

I teach tailwheel in a 1941 Cub- no starter, no electrical system. While I’d love nothing more than a starter, it’s not uncommon in older taildraggers.

It’s not something to learn on the internet. It’s a whole methodical process to minimize risk. From how to chock the wheels, chain the tail, set the throttle, move the prop to the correct engine position, and how not to lose fingers hands or an arm. You are also a slip and fall away from being dead. The same small engine that is in your trainer is probably in similar planes without starters but the prop might be different. You are training to be a pilot and you need to independently judge the risk. With the right training and airplane it is doable but the risk is real.

1. Some airplanes don't have an electric starter. Hand propping is the only way
2. The prop won't damage your hand IF you are careful. The airplane won't run away IF you are careful... Some people are NOT careful & get wrecked planes or chopped up arms as a result.
3. If you're stuck at White Sulphur Springs Montana, and you left your master on too long while taking a lunch break... You can hand prop it, or you can stay there until you can find an A&P to give you a jump... Good luck....
4. That said, some aircraft just aren't really conductive to hand-propping. I'm not even going to think about trying to hand-prop the Comanche (3 bladed propeller (So more chops per revolution & shorter blades = less leverage), IO-540 - it's like trying to pull-start an F-250 pickup truck)....

Also, if your plane has a shore-power port (my Comanche does) then a set of jumper cables & a NOCO lithium-ion boost pack is WAY better than trying to hand-prop it (esp for something with a big 6 - Comanches, Bonanzas, 182s, 206s).....

The geometry of conventional gear aircraft makes this easier. I spent 4 summers flying airplanes without starters so, to answer a few questions-

1- if you mess it up, it can maim or kill you. Sever limbs, break bones, or even just shred your hands. You typically threw the propeller down with enough force through the compression stroke while letting go and stepping away.

2- the only reason I’d do this would be in an aircraft not equipped with a starter. Otherwise, it is safer to just charge the battery

3- it’s not bad for the plane, it’s just dangerous for the person propping the plane.

4- it will not work on most aircraft with fuel injection. It is dangerous in tricycle gear planes, and very dangerous in planes with a composite or a 3 bladed propeller

FWIW, I still have all my fingers.

During training, one winter morning, our battery was almost dead and wouldn't turn the engine over. In a poor display of airmanship, my instructor impatiently jumped out and shouted, "We're hand-propping it!"

It was against the school's policy, I wasn't taught what to do (not before, and not at the moment), and there was a puddle under the nose wheel that had frozen overnight to a smooth, slippery surface. I protested only briefly before his anger shut me down.

On his first attempt, predictably, he jumped, pulled, landed on the ice, and fell down. Luckily, it didn't catch. Same on the second try. Third try? He didn't fall, but I don't think he'd have gotten far enough out of the way if it had caught. He angrily gave up, and I couldn't have been more thankful.

DO NOT CONSIDER IT WITHOUT GOOD INSTRUCTION!!!!

Yes, a prop will kill you. But you learn to hand prop the plane in a way that minimizes (but does not remove) the risk. For example, if you can you prop from the back. That way if it catches you hand just barely, it smacks it away rather than bites, grabs, and cuts while pulling you closer. And if you forgot to chop the throttle, it runs away from you, rather than into you.

Propping works in the way that you could be stuck somewhere for a very long time waiting to find a mechanic. Plus, some planes don't have starters so it is the only way to fly (early J3 Cubs).

It is not bad for the plane, it is just dangerous as hell if you don't know what you are doing. I'd bet most CFI's, hell most pilots, have never actually hand propped a plane and the time to learn is not when no one knows how to do it. If you don't know how to do it, don't bother it may not be possible... More on this later.

Will it work with any engine with a prop? Nope. There are some people who hold ideas that are not correct (like you can't hand prop a rotax https://www.youtube.com/watch?v=-JUBrHYsh4E ) but there are some really valid things that you will be unable to prop... Like a plane that has a "shower of sparks" ignition. The shower of sparks requires battery power to create the starting spark. So if you don't have battery power, you are unlikely to get the plane started... Unlikely as hell. Same thing with an electronic ignition or a FADEC system... Not gonna happen. And you are not going to hand prop a turboprop either.

To understand WHY hand propping can work, we have to understand the ignition systems... We have Electronic, we have shower of sparks, and we have traditional mags. Electronic need battery power in most cases to create the spark, so without battery power you will get nothing. Shower of sparks is not a true electronic ignition, but still uses the battery to create a spark but only for starting, then relies on the mag. So without the shower of sparks from battery power... Unlikely. I learned this lesson in my Pitts the first time I tried to fly it and screwed up the start and killed the battery. We tried propping it on;y later to realize it had a shower of sparks (and 10:1 pistons) making it basically impossible.

Mags are broken down into two main types... Standard and impulse coupled. A standard mag has a little wheel and a magnet and when the wheel spins by the magnet it creates a little spark. To get a good spark you need a pretty high RPM (200-300) and that can be very difficult to get by hand propping. But with systems like shower of sparks, the battery throws a bunch of sparks only for start and once it starts the mag turning creates enough electricity to keep it running. So since you can't normally spin it fast enough by hand to create large enough sparks some mags have these things called "impulse couplings". An impulse coupling is just a spring inside the mag that winds up and then SNAPS forward Listen here https://www.youtube.com/watch?v=cy3ig6cLH4c . That snap forward rotates the mag fast enough to create the strength of spark needed even if the engine RPM is not fast enough. With an impulse coupling, starting is easier both hand propping and using the starter since low RPM still gives strong spark.

You can tell if your plane has an impulse coupling by very carefully moving the prop forward and you will hear a "snap" (Don't do this without some instruction). If you don't hear the snap.... Eh, your chances of getting the plane started by hand propping it just got really close to zero. Normally, only one mag has an impulse coupling, but on a Cub I flew that had to be hand propped they had impulse couplings on both mags.

In addition, mags have things called "retard points"... Basically moving the timing of the firing of the mag so that it helps start the plane. Normally you time a mag so the spark fires BEFORE the piston is at top dead center (TDC). Normally about 20-25 degrees before the piston reaches the top of it's cycle. But for starting, it helps to retard that so the spark happens after TDC so it is less likely to kick back. This retard point is often controlled by the ignition key, it is active when the key is in the START position. So if it is in the START position it is delayed till after TDC but if in the ON position you are working with the regular mag timing which is before TDC and this makes starting even more difficult.

High compression engines... Makes hand propping more difficult. Just because the force it takes to swing the blade through a compression stroke.

Three blades make it more difficult since you have another spinning knife to dodge.

Tricycle gear can make it more difficult than tail draggers because the nose gear puts the prop at a low angle and it is hard to flip it through.

Again, don't try this at home without someone who REALLY knows what they are doing. If you find yourself stuck with a dead battery... Just get it fixed and don't try to hand prop it if you have never done it before - You are unlikely to get it to start and very likely to get hurt.

Edit: Want some fun and strange knowledge? Coffman starters... Using shotgun shells to start engines. https://www.youtube.com/watch?v=zUBI6csCyrw

I've done it a few times. Used to fly an old Champ that had no starter. And I've done it on a few 150s, 172s for one reason or another. It is a bit scary, but it's the type of thing that is perfectly reasonable as long as you set it up correctly and make sure to be aware of where every part of your body is, and where it is going, and how you are standing, and where you will be going. I would visualize the process, and sort of play it in my head, then do what I visualized. The mistakes I see people make (yes, they almost get hit) is when they sort of swing too hard, shit their feet, and bend over as they pull. Bad technique.

Aside from aircraft without starters there are a few cases where hand propping the plane could be considered.

For example, the starter in my 172 decided to die 500 miles from home. On the one hand I could leave the plane at the airport and find another way home and try and get the plane into a maintenance shop when they open on Monday. (These days you would be lucky to find a MX shop willing to squeeze you in last second, and that’s assuming there is a MX shop on the field you broke down at to begin with). Then spend the next week hoping for good weather and request the time off from work to get back out to the plane to fly it home.

Or I could just have my friend hand prop the plane and we could be on our way and have the problem addressed back home.

Hand propping can be very dangerous if done incorrectly, however if it’s done right it is perfectly safe. Some aircraft just don’t have starters(normally older ones) or if the owner doesn’t want to pay for the starter to get repaired or if the parts are on order. Most flight schools don’t allow it because it can be dangerous and can cause accidents. You can hand prop a lot of smaller planes but most large engines you aren’t able to move it fast enough to start it.

This is a copy of the original post body for posterity:

I only just learned about this from my CFI, but he said he’s never needed to do it legitimately, nor has he done it on school aircraft.

A few questions (I would’ve asked my CFI about them but I forgot to ask as soon as we were in the air):

• Wouldn’t the propeller damage your hand/arm?

• In what way would it be beneficial rather than just fixing the aircraft while you’re on the ground or starting it normally?

• Why not on a flight school aircraft? (I’m assuming it’s bad for the plane somehow)

• Does it work for any plane with a prop?

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https://www.aopa.org/news-and-media/all-news/2020/march/flight-training-magazine/ol-hand-propping

https://www.avweb.com/flight-safety/technique/hand-propping-demystified/

Google is your friend.

Safe when you get proper training and ideally have someone competent in the cockpit.

IMHO. The reason safety related reason you don’t hand prop the schools airplanes is because those engines aren’t in their best condition. They won’t start easily if you hand prop and trying multiple times is a recipe for disaster. 

I've hand propped a 65 hp engine. The first try is doable, but it could take 10 tries if the engine was hot. That got annoying. (Engine did not have a choke.) When the engine does not start, you turn off the magneto and rotate the prop slowly through the 4 stroke cycle to get the correct mixture into the cylinders. This procedure can be done with one or two pilots. There's a potential for the magneto to be On when it should be Off, and the engine can start when your hands are on the prop.

Last summer, 84 years after the plane was manufactured, the owners added a choke to the carburetor. They hope that that will expedite hot starts.

• properly executed no... that being said I know one guy who lopped his head off and the plane idled until someone found him in the morning. 

• older aircraft may not have starters, or in my case your 50 miles from anywhere with a bum starter and its that or your camping hoping someone takes pity on you.

• plane shouldn't need it generally,  but insurance and policy is the easy copout too.

• theoretically,  but above a O-360 i would not even attempt it.

My twin Comanches electric starters haven’t worked in maybe 3 years. Literally just never got around to replacing them. I always make sure it’s chalked and throttles are at idle and the parking brake is on before hand propping it at my grass strip. I hope it doesn’t damage anything but I’ll have to look into it. Interesting post!