Why do we hand-prop the way we do?

Hippike

Hippike

Pre-takeoff checklist
Joined
May 22, 2017
Messages
212
Location
KSMO
Display Name
Display name:
Hippike
Silly question (still a student) but if hand propping is so dangerous, why don't we hand prop from behind? Standing beside the cowling (facing forward and not facing the plane) and propping that way, when the engine starts, the thrust would push you backward and you would avoid getting sucked into the spinning prop, no? Am I missing something? Again, student, so don't scold me if the Q is silly.
 
I am not a hand propper....thought about it once with a dead battery. Called the fbo instead.

For a taildragger propping from the front gives the propper a motion away from the prop as they follow through. For a nose dragger the motion will tend to move the upper body towards the prop as they follow through. Propping a tail dragger from the rear would tend to move the upper body towards the prop. That said I’ve seen a picture of a guy propping a cub from behind the prop.
 
Hand propping is not "so dangerous" as long as you know a few basics. Some airplanes are typically propped from behind - mainly J-3 Cubs because little Continentals are so easy to pull through with one hand and the front strut is behind the entry door, which means you have easy access to the throttle after the engine starts. Other airplanes more conventionally configured with the front strut in front of the door makes propping from behind less practical. Other engine types in other airplanes are not so easy to pull through with one hand, and you really need both hands on the prop, and more effort to pull through. Doing this from behind would be awkward and dangerous because of lack of room behind the prop. The ergonomics are bad once you need to put significant effort into it. There is no getting "sucked" into the prop disc. Hand propping accidents mostly happen to folks who don't typically hand prop, are inexperienced with it, have a dead battery and want to get going.
 
Last edited:
If you start a plane from behind, where the strut is in front of the door, you are between the prop and the strut. If for some reason, the throttle was wide-open, you could be pushed into the prop. The throttle shouldn't be wide open, but there a series of things that make things safe even if you make a mistake.
 
A tandem plane like a Cub is simple to prop from behind. The door is on the right and all controls are in easy reach from outside the plane. A side by side plane is more problematic because the controls will be across from you when you're propping from behind. Swinging doors are also a problem, unlike swing-up doors on a Cub. For a Cub I prime the engine, set throttle, and pull the mixture to cutoff. I prop from behind and once it fires I have a few seconds to enrich mixture or it'll quit. that's my safety plan. My Cessna is more difficult with the wide cockpit and control placement but in 20 years with my 180 I've never needed to prop it.
 
Another reason to do it from the front is the angle of the blades. From the front, your hand is resting on the face of the blade pushing against the angled face. From the back, you have to hook your fingers around the blade's trailing edge and do all the pushing against the trailing edge... much more painful if it kicks back.

Both of the planes I've owned that required hand propping (T-Craft and Fisher 404) I propped from the front. OTOH, most Cub pilots seem to do it from behind.
 
I don't have a starter on my airplane. I hand-prop every time. Granted, its a 65hp VW engine with a 52" wooden prop. Its so easy to start, once you get the hang of it, it hardly seems like a big deal.

I hand prop from from behind, the port side of the prop (VWs spin backwards) Left hand for the prop, right hand on the canopy rail. When I swing the prop, momentum pulls me back away from the prop. If the aircraft moves, I lay back on the wing with the throttle in easy reach.

It''ll idle at about 700rpm. And, parked in the grass, its not going anywhere until I give it a big blast of throttle. So, I just pull the chock, untie the tail and hop in. No muss, no fuss!
 
I've been propping my Champ since 1985, like anything else, it's as dangerous or as safe as you make it.
 
The propeller's pitch makes it harder to prop from behind if all else is equal. From the front, your hands are on the cambered side of the prop and the prop can be driven mostly by skin friction on that face with the ends of the fingers a little bit over the trailing edge. That edge has been known to rip fingers off if the engine fires a hair too soon and the prop goes backwards; some non-impulse mags are hot enough to do that if the prop-flip is quick enough, which is why many ignition switches ground the non-impulse mag in the start position.

From behind, you have to use lots of hand over the trailing edge. It's uncomfortable and riskier and I'd only do it if the airplane was a big taildragger, where reaching up and over to get at the blade from the front would be too awkward. I'm a bit short for that.

Nobody should teach themselves to hand-prop just because the battery's dead and the day is so nice. That nice day can turn into a really bad day.
 
In the time that I’ve been involved in Aviation, I’ve never seen airplanes other than your small bore taildraggers be hand-propped from behind, which can be done with a single hand. Just about anything else requires two hands to get the leverage needed to turn the prop over and that calls for the individual to be in the front.

Getting ‘sucked into the spinning prop’ isn’t going to happen. Never attempt to hand-prop an airplane without receiving proper instruction on how to do so. If you are interested, ask an instructor to teach you and practice on an airplane with the mags and master grounded.
 
Hard because of the pitch? BS. It's all about access to the controls and interference of the door. Propping from the front is also about access and door interference. Hand propping is simple. Most guys who discuss it on the internet have never done it.
 
Hand prop'd a Aeronca Chief for almost 10 years. I don't think I could have swung it hard enough from behind. And as others have said, from the front you don't have to hook fingers, more like pushing a bit forward while a lot down and stepping away at the same time. No impulse mags in that Chief either. At 50yrs old, I decided I was done.

And you need someone you can absolutely trust in the plane (if someone is in the plane) with feet planted on the brakes, equally ready to keep it running or kill the engine if anything is wrong. I would only hand prop my wife's Chief and only if she was sitting inside.

On a cool note, my daughter's first recollection of planes and flying is me hand propping so they could go off flying :) She still talks about now.
 
Stewartb said:
Hard because of the pitch? BS. It's all about access to the controls and interference of the door. Propping from the front is also about access and door interference. Hand propping is simple. Most guys who discuss it on the internet have never done it.
Click to expand...

At least 400 hours in hand-propped airplanes, from both in front of and behind the prop.
 
If you're propping from the back you're on the right side of the plane so you pull the blade down. Ideally the prop is indexed to be in the proper place, like a Lycoming powered Cub is. If you look at a prop of a plane at rest the blade edge is easier to pull from the back than the front since the top of the blade is pitched further aft when propped from behind. With the Cub door it's easy to hold onto the door frame as you pull the prop so "falling" into the prop is very easy to prevent. Another comment that's often repeated is how you need leverage to pull the blade down. In reality it takes very little effort to swing the blade to start the engine. I can do it with one finger. It doesn't require strength or leverage.
 
OK, it all makes sense now. Thank you all!
 
I always thought student pilots should be required to learn how to hand prop. Once they did that you'd never have to warn guys about the dangers of turning the prop when not intending to start the engine. They'd understand how easy the prop turns and how it'll fire off if the mags are hot.
 
Stewartb said:
A tandem plane plane with a door like a Cub is simple to prop from behind.
Click to expand...

FIFY. Champ/Citabria means you have to run around the strut/door either way.

The Mooney Mite is another plane that lends itself to starting from behind the prop.
 
You must log in or register to reply here.
Back
Top