Ronald,
I have not been able to stop my prop with the engine shut down (IV-P with Continental 550-E/MT 4-blade prop), although I have tried to do so. I have slowed to 100 KIAS with the throttle at idle, the mixture at idle cutoff and the magnetos off. The engine continues to windmill at about 400-500 RPM with my prop set up…you can see the prop blades going by, but it wouldn’t stop, and I was unwilling to slow down any more. So, my conclusion is that with anything but a catastrophic engine failure that causes it to seize, you’ll have the prop wind milling, and therefore oil pressure to vary the pitch. Of course there are no sure things in such situations, but it’s helpful to consider the alternatives, and to PLAN and PRACTICE for these things…
If you have a full-feathering prop and stop it, you’ll need an un-feathering accumulator, or perhaps turning the engine with the starter would get it out of full feather??? In any case, I considered the alternatives, and elected to go with the counterweighted MT. Not full feathering, but close enough, and an 18-20:1 glide ratio will have you within gliding range of an airport from almost any place in the country. This is a good exercise to check out if you’ve not done so…give it a try when you are flying around…
I did have a catastrophic engine failure in a Cherokee 235 many years ago, and raised the nose/slowed the airplane to stop the prop. This actually increased my glide range considerably, allowing me to land on the runway at Winslow, AZ. Although I had practiced “engine out” landings before, I’d never stopped the prop during practice. I did it this time because the engine was literally tearing itself to bits with the prop turning, and the crunching/grinding noises were very upsetting to my passengers…and to me! Having seen the results first hand, I practiced engine out landings with the prop stopped… and with it wind milling…from that time forward. A stopped prop actually has less drag than a rotating one, so if you do have it stopped, you can glide farther.
Bob
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Thanks for the explanation, and sure as hell I am going to try to see the glide ratio as it has been debated many times by NON lancair owners I know.
Now for your explanation, I am thinking you are doing your test with a running engine, but that is not when we are needing a full feather prop, right? We need it when the mill dies on us, so no oil pressure so therefore no way to feather in any kind of form, right?
(now I have been told by a Aerostar owner that they then just crank the engine to get some low oil pressure and this way they feather, I am not sure if this would work as I do not have this experience at all)
But I do know that when the engine quiets, we try to restart it first by switching the fuel selector, crank until we figured out that it won't start and then……well then it would be handy to have the full feather prop, right? (or do I see this wrong and if so please tell me, I am here to learn :)
A glide ratio of 18:1 is fantastic, this is actually the same as the Evolution, and if I am not mistaken, with the same glide speed :)
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For what I have gathered so far the lancair 4p has a glide ratio similar like a piano LOL In other words if the engine quits then open the door, throw out your keys because there is where you land LOL
Well, this might not be true, or is it?
So how about the full feathering prop ? Does anyone have experience with the before and after installation? How much they cost and data?
And I needed to respond to this…
My IV-P has a glide ratio (at 120 KIAS) of between 5:1 and 20:1, depending on configuration. The difference is truly amazing/impressive/sobering… depending on your situation and mind set. With the gear and flaps down and the RPM at max (prop all the way in), the glide ratio approximates that of a brick…not really, but you’re coming down so fast relative to forward progress that it’s difficult to plan and execute a planned touchdown (at least for me). With the gear and flaps up, AND THE PROP CONTROL ALL THE WAY OUT, my glide ratio at gross weight is approximately 18:1, increasing to a bit better than 20:1 at 800# under gross. At this glide ratio, the performance and “sight picture” approximates that of some gliders. It’s easy to plan and execute an approach and landing to a pre-planned spot…ideally a runway. I have practiced this many times from various altitudes/distances from the airport to a full stop on the runway, using the gear to increase my descent rate, and then the flaps and/or the prop control to adjust the touchdown point. Using the prop control is ideal because the drag effect/descent rate increase almost immediately reversible by pushing it back in. Not so with the flaps. One feature of my Chelton EFIS is a wind-adjusted glide range predictor. I have tested this many times starting at altitudes up to 17,500’ and (set at 18:1) gives me a very accurate and immediate sight picture of airfields within glide range. If it’s within the green circle, I can turn toward an airfield and execute a safe landing there. My MT 4-blade is not full feathering, but allows the engine to run at approximately 700 RPM when at idle and the RPM set to min. I believe this is pretty close to 0 thrust, as the engine idles at approximately 600 RPM on the ground.
So, in summary, the throw out the keys and follow them down scenario can be executed if you really want to go down, but a planned glide at 120 KIAS (very close to best glide for my airplane) in clean configuration yields approximately the performance of a 2-place sail plane—and you have the ability to transition easily between these limits as needed. Try it; you’ll be impressed.
Bob
PS: I considered and rejected a full feathering prop for what I have. Wouldn’t trade for any amount of money…