INSTRUCTORS AND SPINS

[Shiny Side Up]

"See how much better the
airplane is flying, now that you aren't doing anything?"

Most students need this demonstration I find. They often have the misconception that the airplane needs to be muscled around the sky and horribly overcontrol the thing - at least most of the guys do, girls its always the opposite problem. Two different worlds. The thing is most of them forget that small airplanes are designed often to accomodate the smallest user which happens to be a fourteen year old kid. A two hundred pound gorilla if he doesn't keep this in mind can have hands (and feet) of stone, its easy to see how they can get the airplane into trouble if they panic a bit and start hauling hard on stuff. A lot of pilot induced turbulence is often solved by this.

[trey kule]

http://www.tc.gc.ca/eng/civilaviation/p ... n-2377.htm

quick and good read for instructors.

[Oxi]

Not sure anyone really cares, but ...

Most people don't even know that they are
entering a spin. All they know is that the aircraft
is not doing what they want - often with a high
rate of yaw at slow speed - which they try to
correct with aileron, which is horrible because
of the adverse yaw it creates. At slow speed,
use the rudder, not the aileron. I spend an awful
lot of time trying to convince people of this.

Pilots often don't know if they are spinning upright
or inverted. The spin might be accelerated due to
bad flight control inputs, but they don't know that,
either. They might be doing inside or outside snaps
instead of a spin, but they don't know that, either.

Another thing I spend a lot of time on, is trying to
convince people that power at slow speed is really
bad news. When you get slow and screwed up,
the prop is going to screw you up even more with
the pronounced effects of slipstream, gyroscopics,
etc which you cannot always easily oppose with
flight controls because so little mass of air is passing
over them at slow speed.

When you get screwed up, power off to try to reduce
the problems that the prop is creating.

And full rudder opposite the yaw that you see across
the nose cowl.

Neutral ailerons to get rid of problems created by
them, and be careful with jamming the stick full
forward. People love to do that, but if you do it
too early, in a fully-developed spin, it can wildly
accelerate the spin, which you won't like. POH
is of course golden in this regard. Spins are highly
type-specific, and are not only modified by the
C of G, also the PMI. I won't define PMI here
because the last time I did, I was attacked by
someone who felt insulted that I dare define PMI
in a public forum. Fair enough. I therefore presume
that everyone reading this is familiar with it.

Spin recovery is all about teaching pilots to stop
doing bad things to the airplane. Yesterday I was
flying with a student who was hauling the nose
around in a flat turn. No bank. I told him to take
his feet off the rudder pedals. The ball instantly
centered. I told him, "See how much better the
airplane is flying, now that you aren't doing anything?"

CS you have great posts throughout this forum.

I understand that a spin is because of adverse yaw and we get this from sloppy rudder controls when at a stall usually. I want to learn the "why", and I think I can understand that adding power to a spin will aggravate the stall further with the slipstream and yaw from the prop.

From my understanding the angle of attack of the up and down going wings the lift form a sort of equilibrium. Where I don't understand is how the yawing works when in the spin? As well adding ailerons will will aggregate the spin but how will it accelerate the spin?

oxi

[Colonel Sanders]

spin is because of adverse yaw

Well, not always. Technically a spin occurs when you
have different - and increasing - angles of attack on
the wings. This can happen for many reasons.

One of the big reasons is certainly that the pilot sees
a wing drop - it's the one at the higher AOA - and tries
to "pick it up" with aileron. At slow speeds this is generally
a bad idea because of the adverse yaw produced - it's
the same as stomping the into-spin rudder, because it
will increase the AOA of the dropping wing, further stalling
it. Lift will be reduced, drag will be increased (see the Cl
and Cd curves) and around you go.

If there's one thing I could teach you about spins, is that
stick/yoke inputs (aileron and elevator) take a gentle,
vanilla spin and can turn it into a wild ride.

Click on:

http://beasafepilot.com/videos.htm

My friend Spencer made some spin videos in his Pitts.

Click on "Pitts - Accelerated Spin" to see what I mean.

[AEROBAT]

Clearly you should avoid spins and if you do get in one you should follow the POH procedure.

This topic has got me thinking about spin practice. I used to be in the crowd that believed spins were a rare event, unless you were doing acro regularly, and the average GA pilot was better practicing slow flight and stall recovery.

About 4 years ago a friend of mine was cut off turning final by an ultralight and he spun his homebuilt in. Amazingly he lived but was in a coma for a few days and was smashed up pretty good. The last thing he remembered about that day was filling his plane up in the morning to go to the fly-in.

Another high time pilot, his regular ride is a Pawnee, spun an ultralight in from around 100'. He totaly destroyed the fuselage but walked away with a sore ankle.

It could be argued, in both cases, that they were too low to recover anyway but practicing spin recvovery once in a while would at least knock the rust off as far as recognizing an impending stall and cross controlling.

[cgzro]

From my understanding the angle of attack of the up and down going wings the lift form a sort of equilibrium. Where I don't understand is how the yawing works when in the spin? As well adding ailerons will will aggregate the spin but how will it accelerate the spin?

Ailerons control angle of attack which affects drag and lift. drag out on the wing of course creates yaw.
So its easy to see how reducing drag/yaw out at a wing tip will let things spin up faster.
Apart from power however the biggest influnce is elevator.
You can literally speed up and slow down with elevator. Its like having a rotation rate control and its great fun when u get used to it. Basically pushing lowers AOA which reduces drag hence you speed up.
Oh and the nose rises as you push to speed up.....because your engines weight is flung outward more and lufts up the way a bucket swung aroud your head lifts as you spin it faster.

Fun stuff.

[Colonel Sanders]

practicing spin recvovery once in a while would at least knock the rust off as far as recognizing an impending stall and cross controlling

There are three flight exercises which I hold near and dear to my heart.

All of them teach the pilot to use the rudder.

First exercise "dutch roll" - a misnomer, actually. Slow the aircraft
down to the bottom of the power curve, put takeoff flap on, trim it
up and add power to maintain altitude. Roll back and forth, with
increasing amounts of bank. Because of the slower speed, rudder
will be required to co-ordinate with aileron. A gentle introduction
to adverse yaw. Try to keep the ball centered.

Next, the falling leaf. Lots of altitude. Stall the aircraft, and keep
full aft elevator. Pilots will try to "pick up" the downgoing wing
with aileron. Very bad. Learn to use the rudder to control the
aircraft, and walk to down, full stalled. Takes some practice, but
is great for building skill and confidence.

Graduation exercise. Land on the upwind main only. A little
crosswind helps here, but is not essential. Sideslip before landing
and touch down on only the upwind main. Put full aileron over
and add power to roll down the runway only on the upwind main,
never letting the other main, or nosewheel/tailwheel touch the
ground. Add full power and overshoot.

I can teach a pilot these three exercises in one lesson, and it
does wonders for their ability to control the aircraft at slow
speed.

Like forced approaches, most pilots are no good at slow
speed flight because they don't do it enough. They are
scared of stalls and spins, and do their best to avoid them,
but when they unintentionally encounter one, they are toast.


One last thought on spin recovery ... I think it was Bill Kershner
who proposed a spin recovery mechanism, which would be
a boxing glove with a powerful spring behind the dashboard, with
two AOA sensors on the wings. When the aircraft entered a
spin, AOA sensors would release the catch, and the boxing
glove would explode out of the dashboard, striking the pilot
and making him let go of the controls, allowing the aircraft
to recover from the spin.

I think he was kidding.

http://www.asa2fly.com/William-Kershner ... egory.aspx

[AEROBAT]

Colonel,

The falling leaf and rolling on the upwind main pack a lot of learning into a short time. Great practice! When I did my commercial my instructor was a great fan of the one wheel touch and go. We would repeat it until I could track the center line without deviation.