So, part of the PPL in Canada is spin and spiral dive recovery. I've now done five of each and have enjoyed the training. If it ever happens in daylight I'll have some idea how to recover.

However, since the spiral dive training I've had a nagging question that none of my instructors have been able to answer satisfactorily.

Why is there no sense of acceleration as you enter a spiral dive? One of the reasons it is such a killer is it happens without a huge motion signature. All of a sudden you are going really fast in a steep downward bank, losing altitude. You go from 35 knots to 140 knots in a few seconds but you don't feel any G force until you start to pull up and level out.

Accelerate from 35-140 in a straight line and you feel it. Enter a steep dive and you feel it. But accelerate and lose alititude rapidly in a spiral dive and it is almost imperceptible. I don't get it.

Any insight appreciated.

Great Question. I have noticed that myself.

Great question. Here's a wild-ass guess:

Think of a pendulum hanging down from the center of your cabin ceiling. In a normal, non-accelerating, perfectly coordinated turn, it would alway point to the center of the cabin floor. If you accelerated in straight and level flight, the pendulum would point to the rear of the cabin floor during acceleration. If you nosed over, the pendulum would point to the front of the cabin floor.
So, if that holds, a spiral dive is presumably a coordinated turn where forces of acceleration and nose-down are also in balance. Hence, the pendulum would still point to the center of the cabin floor in a spiral dive, and your inner ear would therefor not detect any acceleration.

-DP

Albravo,

You may be practicing the spiral down descent which is used to maintain a key position while spiraling down to pattern altitude. If we hold or trim back pressure to maintain a low power or no power glide speed, we don't accelerate. We also do not accelerate in the spin because we are in a stall.

The dangerous problem is the recovery from the spin. Because the nose is well down, we accelerate quickly when we release back pressure to end the stall.

The dangerous problem in the spiral down is attempting to pull back on the stick to level off before leveling the wings. This we call the graveyard spiral.

If we try to spiral down in a dive (no back pressure on the stick,) gravity thrust of altitude will cause us to accelerate very quickly the same as if the wings were level and the nose well down. If you are required to do this on the Canadian PPL, it is even more important to level the wings prior to pulling back on the stick to level the nose. We also have to start the pull up to level the nose early enough to be able to slowly level the nose before Vne or impact with the ground. Target fixation, in a gun run, puts us in a situation where our ability to engage the target gets better and better. We have to have an altitude in mind where we will begin the pull up with enough room that we are not in danger of either stalling or hitting the ground in a dive.

All curved flight causes load factor. That can be a turn or a pull up or both. We can increase engine thrust in a level turn to overcome load factor until we no longer have excess engine thrust. Or we can allow the nose to go down as the airplane is designed to do and use free gravity thrust of altitude to prevent load factor in the turn. A spiral dive or wings level dive, however, does not trade the speed gained in the dive for altitude. By continuing down in a nose low attitude, we continue to gain airspeed through gravity thrust. The greater the airspeed gained, the harder it will be to level the nose without stalling in the time available before ground impact.

Contact

Contact, these are definitely graveyard spirals. Power back, level the wings, ease up gently because Vne is rapidly approaching. Easy to tell from spins because the spins have an obvious helix feeling to them and the ground seems pretty much straight out the front window.

I found the spin recovery a bit more difficult. Power off, neutralize ailerons, opposite rudder, gentle down elevator then level the wings and pull up gently when the rotation stops. Its a lot to remember when your butt is puckered.

Denali, yours is the explanation that makes the most sense to me. It is a perfectly coordinated turn. Ball dead center. I get that might fool the ears, but where is that roller-coaster feeling in the gut?

Albravo,

So you are diving in a spiral turn.See if he will let you pitch up, wings level, first and then let the nose fall through naturally in the energy management turn. I see no utality in a spiral dive.

When spraying, we want to get up and make the turn quickly and without load factor. We want to be able to get up to clear the wing and also to be able to get the wing level again before returning to ground effect. When shooting rockets, we want as much time on target as possible.

Contact

In terms of vertical - you are accellerating in the same axis as gravity, by gravity. You are almost just falling... So no g-force, because it's the force of g(ravity) accellerating you.
Just like jumping off a diving board, basically no sensation of "g's"

Simple. a spiral dive is induced by gravity. We all experience an acceleration of 1 g in everyday life. Jump off a building or out of an aircraft and the 1 g diminished considerably. you will actually feel lighter, or negative acceleration. If it was possible to free fall in a vacuum, you would be weightless, 0 g.

As Battson says,the angle of bank makes no difference. There is no load factor until we pull back on the stick.

Oh! Don't pull back while still turning. That would give you gs from pull up on top of gs from trying to make a level turn. Also pulling back would increase the angle of bank.