Another stall spin

On Tuesday, September 4, 2012 8:02:52 PM UTC-4, noel.wade wrote:
On Sep 4, 10:34*am, bumper wrote: It's easy enough to practice low (within a few wing spans), slow, high bank angle turns in a power plane like a Super Cub or Husky. Not so many opportunities in a glider. To the uninitiated, there's a tendency to skid a turn when low, as some pilots try to minimize bank angle - too much bottom rudder, not enough aileron. Not a good situation to be. Yes, one thing to point out is that a lot of training spins emphasize a lot of back-stick *plus* a punch on the rudder to initiate the spin. But IMHO this isn't how spins develop in the real world. I believe that many spins develop as the aircraft's situation degrades over a couple of seconds (airspeed bleeds off, or back-stick/rudder is slowly added in by the pilot without realizing they're "creeping" on the controls). Another item for thought: Using trim on an aircraft is great (I am constantly re-trimming my aircraft). BUT if you trim the aircraft for flight at a slow speed (say an approach-speed that's a little too slow), the trim-spring is what is "pulling back" on the stick. YOU will not feel yourself pulling on the stick. Yet the aircraft may be dangerously close to a stall/spin. And once it starts to develop you'll have to PUSH *against* the trim spring in order to un-stall the wing! Simply "relaxing the back-pressure" will not break the stall or stop the spin. This goes against a lot of the muscle-memory we learn when we train in gliders and perform training stalls & spins, so pilots are not likely (IMHO) to take the full corrective action. Lastly, think about wind gradient and headwind/tailwind components... Let's say we're making a landing pattern (and this could be particularly bad in an off-field situation). There's a tailwind on downwind so the ground rushes past and we try to slow down (perhaps subconsciously). Then we turn base/final and while we get a bit of the headwind, we also have to remember low level wind gradients mean that as we descent down close to the ground that headwind goes away. So we have pulled the stick back (from trying to "slow down" on downwind) AND we lose lift as the headwind decreases. Stall, anyone? And possibly a spin, if the wind gradient kicks in during the base-to- final turn. Think about the typical base-to-final spin accident - they tend to happen when people are low and not yet on final, right? So isn't it possible that its not just them "skidding" the turn, but also possibly aggravated by the wind gradient? How many instructors discuss the wind gradient with their students? How many discuss it in terms of a low base-to-final turn? --Noel (CFIG-in-training)

I teach the sneaky slow low banked turn with student looking into the turn(where are the "pilots" looking when they spin on base to final?) while I have them try to force "just a little more turn" while very subtly sneaking in some more inside rudder. When it goes, they are surprised. That is the point- it comes as a surprise, especially when the pilot isn't watching the attitude and yaw.
Add a bit of a gust or shear, and it is even more sudden.
Question- "how would you like to do that low?" gets the predictable answer.
UH

I prefer to move the trim full forward before entering the pattern. The
back pressure required has not been a problem with the various gliders I've
flown. If I get distracted for some reason I hopefully will be flying
faster than required, rather than slower. I too find it easier to control
air speed by varying the back pressure. If the glider is trimmed for
approach speed and there is a loss of headwind due to ground friction, the
forward pressure required to maintain airspeed feels unnatural to me.

At 00:02 05 September 2012, noel.wade wrote:
On Sep 4, 10:34=A0am, bumper wrote:
It's easy enough to practice low (within a few wing spans), slow, high
ba=
nk angle turns in a power plane like a Super Cub or Husky. Not so many
oppo=
rtunities in a glider. To the uninitiated, there's a tendency to skid a
tur=
n when low, as some pilots try to minimize bank angle - too much bottom
rud=
der, not enough aileron. Not a good situation to be.

Yes, one thing to point out is that a lot of training spins emphasize
a lot of back-stick *plus* a punch on the rudder to initiate the
spin. But IMHO this isn't how spins develop in the real world. I
believe that many spins develop as the aircraft's situation degrades
over a couple of seconds (airspeed bleeds off, or back-stick/rudder is
slowly added in by the pilot without realizing they're "creeping" on
the controls).

Another item for thought: Using trim on an aircraft is great (I am
constantly re-trimming my aircraft). BUT if you trim the aircraft for
flight at a slow speed (say an approach-speed that's a little too
slow), the trim-spring is what is "pulling back" on the stick. YOU
will not feel yourself pulling on the stick. Yet the aircraft may be
dangerously close to a stall/spin. And once it starts to develop
you'll have to PUSH *against* the trim spring in order to un-stall the
wing! Simply "relaxing the back-pressure" will not break the stall or
stop the spin. This goes against a lot of the muscle-memory we learn
when we train in gliders and perform training stalls & spins, so
pilots are not likely (IMHO) to take the full corrective action.

Lastly, think about wind gradient and headwind/tailwind components...
Let's say we're making a landing pattern (and this could be
particularly bad in an off-field situation). There's a tailwind on
downwind so the ground rushes past and we try to slow down (perhaps
subconsciously). Then we turn base/final and while we get a bit of
the headwind, we also have to remember low level wind gradients mean
that as we descent down close to the ground that headwind goes away.
So we have pulled the stick back (from trying to "slow down" on
downwind) AND we lose lift as the headwind decreases. Stall, anyone?
And possibly a spin, if the wind gradient kicks in during the base-to-
final turn. Think about the typical base-to-final spin accident -
they tend to happen when people are low and not yet on final, right?
So isn't it possible that its not just them "skidding" the turn, but
also possibly aggravated by the wind gradient? How many instructors
discuss the wind gradient with their students? How many discuss it in
terms of a low base-to-final turn?

--Noel
(CFIG-in-training)

On 9/4/2012 5:58 PM, wrote:

I teach the sneaky slow low banked turn with student looking into the turn

(where are the "pilots" looking when they spin on base to final?) while I

have them try to force "just a little more turn" while very subtly
sneaking

in some more inside rudder. When it goes, they are surprised. That is
the point-

it comes as a surprise, especially when the pilot isn't watching the
attitude and yaw.

Add a bit of a gust or shear, and it is even more sudden.

Question- "how would you like to do that low?" gets the predictable answer.

UH


What glider were you flying?: We tried that with an Blanik L13, and
couldn't get it to spin without using the normal highly exaggerated
control inputs - stick all the way back and full rudder.

On 9/4/2012 7:49 PM, Greg Arnold wrote:
On 9/4/2012 5:58 PM, wrote:

I teach the sneaky slow low banked turn with student looking into the turn
(where are the "pilots" looking when they spin on base to final?) while I
have them try to force "just a little more turn" while very subtly sneaking
in some more inside rudder. When it goes, they are surprised. That is the point-
it comes as a surprise, especially when the pilot isn't watching the attitude
and yaw.

Add a bit of a gust or shear, and it is even more sudden.

Question- "how would you like to do that low?" gets the predictable answer.

UH


What glider were you flying?: We tried that with an Blanik L13, and couldn't
get it to spin without using the normal highly exaggerated control inputs -
stick all the way back and full rudder.

Remember, it's not the fully developed spin that's the *goal* of UH's
exercise. It's the sudden/unexpected *departure* that surprises people...and
if occurring low enough often leads to death. How many of this year's North
American below-pattern-height fatalities involved a fully developed spin, I
wonder...

In a related vein, there may somewhere be a 2-33 - everyone's poster child of
a "will spin in a heartbeat" glider, right? (Not!) - that can be forced into a
fully developed spin while within its certified CG limits...but I've never
encountered it. OTOH, every 2-33 I've flown WILL do a "nice departure" if
snuck up on as UH described. I also know of (have a photo of, sent by my
instructor) a 1-26 that was spun in from ~700' agl. The 1-26 is another known
"spinning killer" of a sailplane, right? (The pilot survived.) Point being,
metal airplanes in particular are likely to have a larger "deviation from the
norm" in terms of "departure behavior and beyond..." than ships pulled from molds.

Low altitude departures tend to be killer events.

Regards,
Bob W.

On 9/4/2012 7:25 PM, BobW wrote:
On 9/4/2012 7:49 PM, Greg Arnold wrote:
On 9/4/2012 5:58 PM, wrote:

I teach the sneaky slow low banked turn with student looking into the
turn
(where are the "pilots" looking when they spin on base to final?) while I
have them try to force "just a little more turn" while very subtly
sneaking
in some more inside rudder. When it goes, they are surprised. That is
the point-
it comes as a surprise, especially when the pilot isn't watching the
attitude
and yaw.

Add a bit of a gust or shear, and it is even more sudden.

Question- "how would you like to do that low?" gets the predictable
answer.

UH


What glider were you flying?: We tried that with an Blanik L13, and
couldn't
get it to spin without using the normal highly exaggerated control
inputs -
stick all the way back and full rudder.

Remember, it's not the fully developed spin that's the *goal* of UH's
exercise. It's the sudden/unexpected *departure* that surprises
people...and if occurring low enough often leads to death. How many of
this year's North American below-pattern-height fatalities involved a
fully developed spin, I wonder...

In a related vein, there may somewhere be a 2-33 - everyone's poster
child of a "will spin in a heartbeat" glider, right? (Not!) - that can
be forced into a fully developed spin while within its certified CG
limits...but I've never encountered it. OTOH, every 2-33 I've flown WILL
do a "nice departure" if snuck up on as UH described.


Couldn't get the L13 to do that.

The 2-32 will do a wonderful approach departure, with very little exaggeration of the controls. Just get it a bit slow, in a shallow bank, a bit of bottom rudder and top aileron and whoops! you are pointing at the ground.

One demonstration and you will never fly a slow pattern in a 2-32!

Kirk
66

On Tuesday, September 4, 2012 8:49:53 PM UTC-5, Greg Arnold wrote:
On 9/4/2012 5:58 PM, wrote:



I teach the sneaky slow low banked turn with student looking into the turn



(where are the "pilots" looking when they spin on base to final?) while I



have them try to force "just a little more turn" while very subtly

sneaking



in some more inside rudder. When it goes, they are surprised. That is

the point-



it comes as a surprise, especially when the pilot isn't watching the

attitude and yaw.



Add a bit of a gust or shear, and it is even more sudden.



Question- "how would you like to do that low?" gets the predictable answer.



UH





What glider were you flying?: We tried that with an Blanik L13, and

couldn't get it to spin without using the normal highly exaggerated

control inputs - stick all the way back and full rudder.

I went out and played with trying to spin my ASW20b in thermals this weekend. In many thermals in my part of the world there is turbulent air encircling them. In several, as I thermalled through it, the airframe vibrated and it felt just like the burble before a stall/spin. I never put these two phenomena together before, but I think it would be hard to tell the difference if you were in that part of a thermal when the spin was starting. I certainly couldn't tell the difference. The rough air completely masked the burble. The nose falling through the horizon is hard to miss though. As an aside: I was quite surprised at how much I could mistreat it in a 40 degree bank without it diverging. The slightest release of back pressure and it was flying again.

I have an angle of attack string on the canopy. (see DG web site for more info on AOA strings) The airspeed and angle of attack would get out of phase as I approached the stall such that at times the airspeed showed 45 knots, yet the angle of attack string was at the stall mark. At other times, the airspeed was at 40 knots and the AOA string was below the stall mark. This was an eye opener!

On 8/28/2012 10:54 AM, Brian wrote:
On Tuesday, August 28, 2012 11:08:01 AM UTC-6, John Cochrane wrote:
snip

So, just because you've never unintentionally spun at altitude
does

not mean your chances at 300 feet are the same.

John Cochrane

Excellent point John, and for the same reasons I think the spinning
intentionally at altitude and being confident you can recover may
provide a false sense of security when thermalling low. It just
isn't the same when done done at 300 feet.

I call 300 feet "short final".

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Another reason I trim full forward while in the pattern is that I feel the
back pressure during the entire approach. If I slow from approach speed to
say 10 knots slower, I feel the additional back pressure. A kind of
pressure warning system. If it takes more back pressure the aircraft will
slow up. If on the other hand I trim for approach speed, the back pressure
to fly 10 knots slower is barely perceptible. Without the pressure
feedback it is easier to unintentionally slow up. Some gliders tend to
loose airspeed rapidly with extended air brakes which if not caught in
time can be fatal. I think we all agree that there is no substitute for
adequate airspeed and that more of it is required when manuevering in air
that is affected by terrain. At 05:29 05 September 2012, Eric Greenwell
wrote:
On 8/28/2012 10:54 AM, Brian wrote:
On Tuesday, August 28, 2012 11:08:01 AM UTC-6, John Cochrane wrote:


So, just because you've never unintentionally spun at altitude
does

not mean your chances at 300 feet are the same.

John Cochrane

Excellent point John, and for the same reasons I think the spinning
intentionally at altitude and being confident you can recover may
provide a false sense of security when thermalling low. It just
isn't the same when done done at 300 feet.

I call 300 feet "short final".

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

Below 1000 ft I am looking at the string and the needle every 3 sec.