Height velocity avoid curve for fixed wing?
It occurs to me, with the recurring discussions about speeds, that there is an important speed (Vy) which is regularly ignored - at great peril. For those who are familiar with helicopter flying, Helicopters are provided with the Height Velocity Curve (AKA "avoid curve" or "deadman's curve"). For convenience for those not familiar, here's one:
You can notice the reference to the recommended takeoff profile. It occurs to me that where this to also be presented for fixed wing aircraft, and pilots to take it seriously, accidents could be prevented.
In essence, that curve tells the pilot the flight conditions from which a safe autorotation landing is not possible. An important thing to know! So no, you can't sit up hovering at 500 feet, and expect to land safely if the engine quits. Similarly, you can't blast along at 60 knots, and ten feet up, and expect to land safely after an engine failure.
So why does PilotDAR think this applies to airplanes too? Though I have never seen a height velocity avoid curve for a fixed wing aircraft, I think that they might be equally applicable, and important. The airplane Flight Manual will state a Vy, and a Vx, and a recommended glide speed. Think about your plane, which is the slower speed - Vx, or glide speed? Ah, Vx you say - there in lies the problem.
Pilots find that the plane will climb away at Vx, and it's cool to look like you're flying a super STOL departure, 'cause the nose is way up, and the increase in altitude verses ground covered is very good. But, hanging up there, on power, but with lesser forward speed, you're in the middle of the curve avoid zone for your aircraft. The engine goes blat, and you're gliding at that slower speed, you're going to have to trade altitude for speed - just to get going a fast a glide speed! Then you glide! Depending on your beginning altitude, you may have reached the ground before you reached glide speed. If you descend at a speed slower than glide speed, you've reduced the reserve you have with which to flare, pull to flare, you just continue down, with even less control.
People ask me what's the most scary thing about test flying modified aircraft. Well, the testing I did, which I most thought would lead me to wreck a plane was required engine failures from 50 feet, and glide back to the remaining runway in a modified Cessna Grand Caravan. 'Thing was that as I had reduced Vy from 87 knots to 80, Transport Canada required a demonstration of a land back from that slower speed - I did it, but it was scary! Now I know why Cessna errs to the faster speed for climb out. Not so much for good climb performance, but simply so you can glide and land reasonably after an engine failure at that altitude.
So, the climb speed in the flight manual might be established more based upon safe return to earth, following a low altitude engine failure, rather than the optimum performance. I would be pleased to see a height velocity curve published for planes too, so a pilot understands why that Vy speed is a little faster, and actually embraces that speed for normal operations, to improve safety.
There are many recommended operational practices, with hidden underlying rationale. I wish that pilots were given the "full story" so they could make more informed decisions about how they fly. An HV curve in the emergency procedures section of a flight manual would be one way of presenting this information to the pilot.....