BALL MOVEMENT (NOT WHAT YOU THINK)

[John Swallow]

[color=#009000][font=helvetica][size=1em]This from another website:  [/size][/font][/color]
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[left][color=rgb(29, 33, 41)][font=helvetica][size=13px]I often ask instructors where the ball should be in a sixty degree bank turn, and it should never be in the centre in a low powered light aircraft.  At ninety degrees of bank the aeroplane in knife edge flight will have the ball displaced to the bottom[/size][/font][/color][/left]
[left][color=rgb(29, 33, 41)][font=helvetica][size=13px]At forty five degrees the yaw and pitch movements are equal and the ball is in the middle. As you go beyond forty five degrees of bank the thrust vector has to be higher, and the ball is progressively displaced into the turn.[/size][/font][/color][/left]
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[left][color=rgb(29, 33, 41)][font=helvetica][size=13px]Thoughts...?[/size][/font][/color][/left]

[Slick Goodlin]

[quote author=John Swallow link=topic=8735.msg24003#msg24003 date=1531696918]
[color=rgb(29, 33, 41)][font=Helvetica][size=13px]Thoughts...?[/size][/font][/color]
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I don’t buy it.  Knife edge is not a coordinated turn, so the skid ball plays no part.  A properly executed turn with 90* of bank would still have the ball centred, but be exceedingly difficult to do thanks to the infinite number of G’s liquifying the pilot.

[Fendermandan]

Makes sense with the low powered plane. The ball will be slightly right with left wing down as the nose comes down. I never tried it but can't imagine holding the nose level with the top rudder much with no energy.

[Colonel]

This is an odd approach to what an airplane does.

Instead of asking what the bank is doing, I would ask,
[i]what do you want the aircraft to do[/i]?

If you want the aircraft to change heading, you do it
with the ball in the center, and as much bank as required
to give you the rate of turn desired.  This is generally an
issue with speedy airplanes, that need more bank.

Note that theoretically you can speed up the rate of
heading change with inside rudder, but that slides the
ball to the outside and what we call a skid and can be
dangerous because the inside wing can stall, and most
people think an un-coordinated turn is unpleasant.

If you want the aircraft to descend at the same airspeed
(reduce it's energy, you don't want to simply convert
altitude to airspeed) you do it by

- reducing power,
- adding drag with flaps and
- adding drag with a slip or slipping turn during which the
ball will fall to the inside as you use "too much" bank for a
co-ordinated turn. 

I do this on pretty well every landing - I have the power
off, excess energy and I bleed it off with a slip, because
I have no flaps. 

I did exactly that, three times yesterday, and during
every approach, landing on the runway was assured
[i]even if the engine failed[/i]. 

Actually, if the engine seized up solid, I would have
[i]less drag[/i] because the windmilling constant speed
3-blade prop, which creates enormous drag with the
throttle at idle, would no longer create significant
drag if it stopped turning.