The checklist thread got me wondering.
All the engine failure checklists (that I have seen) say “mixture full rich”.
But if you do this at say FL170, will the engine ever restart?
I think there is a case for initially leaving the three engine controls exactly at their previous positions. The most likely cause is going to be fuel system icing or some other blockage, or running out of fuel. Nothing to do with the engine itself. So the correct actions should be
The first three take a few seconds. The last one will take longer especially if you were not expecting to have all this fun so suddenly 
All of the above should be memory items anyway. If you are on autopilot (prob99 the case at altitude) then the speed will decay from cruise to stall in the time it takes to dig out the checklist and open it up.
Obviously if there was a big bang and you see a piston with a piece of conrod sticking up through the cowling, you will go straight to the last one
But other than that, engines don’t just fail suddenly, without any warning. Well, there is the engine driven fuel pump, which is why you put the electric fuel pump on right away. Fuel servos also don’t just fail in cruise, except for
Clearly even a memory checklist needs aircraft systems knowledge of your aircraft.
I’ve had an engine stop whilst aerobating and the thing I noticed is how steep the dive has to be to get the prop rotating before the engine would restart. I know I could have used the starter but it was an interesting experience.
Apart from the aerobatic situation, I don’t think there is anything like a “restart” of a typical Lyco/Conti. The propeller will keep windmilling (you have to stall the aircraft to stop that) and that means the magnetos will continue to produce sparks so the only thing that can make a difference is fuel on or fuel off.
Yes. When I had an engine failure I was puzzled by that for a second. How do I restart? There is no restarting, the engine is turning. Tried all combination of mags, mixture, carb heat. In the Onex with a VW engine, the engine will stop. That has to be restarted with the starter. This is also a bit puzzling. Some purists likes to have no electric except a hand held radio. The VW can be hand propped, but if it stops in the air, there is no way of restarting it, unlike a Cub with a Continental that windmills.
A Lycoming/Conti with a wooden prop, will that windmill (at gliding speed)? The VW will not because there is too little inertia to pull it over the compression strokes.
From John Deakin on BeechTalk:
I used to do a modest amount of investigating of these reports and found that in every case, the “restart” was grossly mismanaged. In many cases by the book method of restarting. POHs often say, “Fuel on fullest tank, mixture full rich, boost pump on.”
Of course it will not restart! That’s a surefire way to FLOOD the engine!
I suggest simply (and calmly!) turning the fuel selector to any tank with fuel, and waiting. DO NOT change anything else! The engine will burp, and come back to life, and run precisely as before. IF you are the impatient type, and cannot stand the 3 seconds, or 5 seconds it takes to get fuel back in the lines, hit the boost for a couple of seconds, and then off again.
With a turbo, it MAY be necessary to “sweep” the mixture at high altitude.
I have a Conti with a wooden prop. Its a geared engine with a 9.2:1 compression. Pulling it through 6 compressions on the pre-flight takes a lot of muscle – and yet its almost impossible to stop it windmilling in flight, even at stalling speed. It will stop windmilling at about 50kts on the runway rollout. I’d guess it takes aerobatics to stop props windmilling.
Under standard operations (I.e. No aerobatics at all) is there a circumstance where the engine would fail without something more serious/neglect at hand?
I was thinking about Peter’s comment about restarting at FL170… Ok you could have carb icing, but a selection of carb heat on and a pull to idle cut-off followed by a slow push forward to the mixture would restart the engine while it is windmilling. Although carb heat on alone should suffice as long as not much altitude has been lost.
The only other circumstance I can think of is a decent without richening the mixture, would lean to the point of cutoff, but the engine would run like a shaggy dog before cutting out.
In the Onex with a VW engine, the engine will stop. That has to be restarted with the starter. This is also a bit puzzling. Some purists likes to have no electric except a hand held radio. The VW can be hand propped, but if it stops in the air, there is no way of restarting it, unlike a Cub with a Continental that windmills.
I’ve been in a VW powered aircraft when the engine quit. The cause was vapor lock, and the prop stopped turning about as fast as it would on the ground – almost instantaneously. This was with a wood prop. We flattened the battery attempting restart and rode it to the ground.
The little A-Series Continentals were designed for no electrical system, you can’t install a starter if you wanted. With low compression and high inertia prop (even a wood prop) I agree there’s no stopping them turning even if you turn off the mags. They are gentle and forgiving devices. If you run a tank dry, you have all the time in the world to get it running. You don’t even need a primer to start a A65 (on the ground). Just pull it through a few blades, the Stromberg carb was designed to self prime with throttle fully closed. Then it usually starts on the next gentle pull with the mags on. By comparison, running a tank dry then restarting with a windmilling prop is even easier. Turn on another tank and touch nothing else, leave the engine controls exactly as they are.
Notes on engines not windmilling – Rotax 912 is not usuall windmilling – unless you are somwhere about 250-270kph ;-) close or above vne for most of aircraft equipped.
