Hi Robert
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 :)
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… |