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Stall/spin and ground reference maneuvers



 
 
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  #1  
Old March 4th 14, 04:54 AM posted to rec.aviation.soaring
Bill D
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Default Stall/spin and ground reference maneuvers

Those with airplane training will be familiar with Ground Reference Maneuvers which teach students very accurate maneuvering with solid airspeed and coordination control at low altitudes despite the peculiar visual cues found there. Those with glider-only training will not be familiar with GRM's since they are not practical in glider trainers.

GRM's are flown at "pivotal altitude" (Search web) which at 55 knots ground speed will be a little under 300'AGL. I recall hours of GRM practice in a J-3 Cub preparing for the Commercial Airplane check-ride. Perhaps that's one reason I'm still alive after more than 50 years of flying.

The argument which says one should avoid low turns ignores the fact that every glider flight ends with at least one turn at or below 300' AGL. Unless a pilot is well trained for low turns this is a recipe for a stall/spin accident. I respectively suggest a better alternative is to find a CFI willing to provide GRM training in a touring motorglider or slow LSA and get really good at it.
  #2  
Old March 4th 14, 05:41 AM posted to rec.aviation.soaring
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Default Stall/spin and ground reference maneuvers

On Monday, March 3, 2014 7:54:39 PM UTC-8, Bill D wrote:
Unless a pilot is well trained for low turns this is a recipe for a stall/spin accident. I respectively suggest a better alternative is to find a CFI willing to provide GRM training in a touring motorglider or slow LSA and get really good at it.


Yup - I agree. People don't get enough experience in these critical visual cues.

9B
  #3  
Old March 4th 14, 01:18 PM posted to rec.aviation.soaring
John Carlyle
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Default Stall/spin and ground reference maneuvers

Who looks down the wing at the ground when they turn? In pattern turns I'm looking straight over the glare shield, focused on airspeed (pitch), yaw string, and bank angle.

-John, Q3


On Monday, March 3, 2014 10:54:39 PM UTC-5, Bill D wrote:
The argument which says one should avoid low turns ignores the fact that every glider flight ends with at least one turn at or below 300' AGL. Unless a pilot is well trained for low turns this is a recipe for a stall/spin accident. I respectively suggest a better alternative is to find a CFI willing to provide GRM training in a touring motorglider or slow LSA and get really good at it.


  #4  
Old March 4th 14, 01:54 PM posted to rec.aviation.soaring
John Godfrey (QT)[_2_]
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Default Stall/spin and ground reference maneuvers

On Tuesday, March 4, 2014 7:18:47 AM UTC-5, John Carlyle wrote:
Who looks down the wing at the ground when they turn? In pattern turns I'm looking straight over the glare shield, focused on airspeed (pitch), yaw string, and bank angle.



-John, Q3





On Monday, March 3, 2014 10:54:39 PM UTC-5, Bill D wrote:

The argument which says one should avoid low turns ignores the fact that every glider flight ends with at least one turn at or below 300' AGL. Unless a pilot is well trained for low turns this is a recipe for a stall/spin accident. I respectively suggest a better alternative is to find a CFI willing to provide GRM training in a touring motorglider or slow LSA and get really good at it.


The insidious part is what you perceive in your peripheral vision unconsciously. During a committed "this is all I am doing" landing this may not be such a huge factor, but when trying to decide whether to try an thermal away after being effectively on downwind or base it is a much bigger effect.
  #5  
Old March 4th 14, 02:09 PM posted to rec.aviation.soaring
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Default Stall/spin and ground reference maneuvers

On Tuesday, March 4, 2014 4:54:30 AM UTC-8, John Godfrey (QT) wrote:
On Tuesday, March 4, 2014 7:18:47 AM UTC-5, John Carlyle wrote:

The insidious part is what you perceive in your peripheral vision unconsciously.


True. Peripheral vision is terrible at detail but very good at picking up angular motion.

Plus, last time I checked I was looking pretty close to down the wing as I initiated the turn from base to final. Aren't you supposed to look at the runway, not straight ahead into the countryside, on base leg? Once you're established on final there's not much turning anyway.

9B
  #6  
Old March 4th 14, 02:34 PM posted to rec.aviation.soaring
John Carlyle
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Default Stall/spin and ground reference maneuvers

Just because you perceive something doesn't mean that you have to pay attention to it. The most important things in a pattern turn (or low altitude thermalling) are perfectly coordinated turns and proper airspeed. Scans for traffic and feeling for lift are fine, but who cares what the ground does?

One does look at the airport when initiating the turn from base to final, but once the turn starts all you need to do for the next 5 seconds is look over the nose for pitch, yaw and bank. The airport will appear when you need it without having to search for it.

-John, Q3


On Tuesday, March 4, 2014 8:09:16 AM UTC-5, wrote:
On Tuesday, March 4, 2014 4:54:30 AM UTC-8, John Godfrey (QT) wrote:
The insidious part is what you perceive in your peripheral vision unconsciously.


True. Peripheral vision is terrible at detail but very good at picking up angular motion.

Plus, last time I checked I was looking pretty close to down the wing as I initiated the turn from base to final. Aren't you supposed to look at the runway, not straight ahead into the countryside, on base leg? Once you're established on final there's not much turning anyway.

9B


  #7  
Old March 4th 14, 03:43 PM posted to rec.aviation.soaring
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Default Stall/spin and ground reference maneuvers

On Tuesday, March 4, 2014 8:09:16 AM UTC-5, wrote:
On Tuesday, March 4, 2014 4:54:30 AM UTC-8, John Godfrey (QT) wrote: On Tuesday, March 4, 2014 7:18:47 AM UTC-5, John Carlyle wrote: The insidious part is what you perceive in your peripheral vision unconsciously. True. Peripheral vision is terrible at detail but very good at picking up angular motion. Plus, last time I checked I was looking pretty close to down the wing as I initiated the turn from base to final. Aren't you supposed to look at the runway, not straight ahead into the countryside, on base leg? Once you're established on final there's not much turning anyway. 9B


If you wait till you are wing is almost aligned with the runway, it is likely to be a bit late, commonly leading to a rushed, and possibly skidded turn.
I teach my pilots to check their position on base,clear opposite side for missed traffic on final, decide when they will turn- early is almost always better than late, then watch the nose during the turn so as to keep the pitch attitude correct and avoid skidding the turn. A glance toward the runway will be enough to determine when to start rolling out.
Plenty of folks have spun in looking at the runway or wing tip. few have done so looking over the nose.
Bill's point about making pilots aware of the changing view is a good one and one I think I will add to my lesson points.
FWIW
UH
  #8  
Old March 4th 14, 03:54 PM posted to rec.aviation.soaring
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Default Stall/spin and ground reference maneuvers

On Tuesday, March 4, 2014 5:34:09 AM UTC-8, John Carlyle wrote:
Just because you perceive something doesn't mean that you have to pay attention to it. The most important things in a pattern turn (or low altitude thermalling) are perfectly coordinated turns and proper airspeed. Scans for traffic and feeling for lift are fine, but who cares what the ground does?

One does look at the airport when initiating the turn from base to final, but once the turn starts all you need to do for the next 5 seconds is look over the nose for pitch, yaw and bank. The airport will appear when you need it without having to search for it.


Well, it's a human in the loop feedback control system with multiple inputs - visual, inertial and some auditory. If you are making a low turn from base to final you may initiate the turn while looking away from the yaw string and airspeed because the runway is off to the side and you are trying to set a turn rate to put you in-line with the runway on final. At the same time your peripheral vision at this altitude is now subtly telling you that you are over-banked/under-ruddered because you are below the pivotal height where the turning cues of the wing against the background reverse. You aren't used to this peripheral cue and may not be aware of how it affects your overall perception of attitude and coordination and how that feeds back into the control system.

You may be better at it than I am, but I can't just take a snapshot to the side before initiating the turn to final and then look ahead to the yaw string and airspeed without ever looking out to the runway again and expect to end up both pointed at and in-line with the runway heading. I tend to scan back and forth. It only takes a moment of being over-ruddered to generate a spin, particularly if you are at low speed (and an approach into an airport in a mountain valley can make you fly too nose-high if you are not paying proper attention).

Is any of this good and proper airmanship - well no. But that is a little beside the point. The fact is that over the past 20 years 39% of fatal glider accidents and 36% of all glider fatalities have been due to stall/spin. That's 43 dead glider pilots and passengers, or slightly more than two per year. It is the leading cause of death while flying gliders. We must be doing something (or some things) wrong. My thought is if we are all aware that our perception from peripheral vision changes (and which way those changes work) we all may be in a slightly better position to resist the subconscious urge to do the wrong thing at just the wrong time.

9B
  #9  
Old March 4th 14, 04:09 PM posted to rec.aviation.soaring
Mike the Strike
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Default Stall/spin and ground reference maneuvers

On a recent landing at my home field, a potential conflict with another glider on final caused me to lengthen my base leg while I monitored the other plane. While checking the traffic, my airspeed dropped below my usual approach speed - I was watching the traffic and the field and not my panel or yaw string. I had to forcefully speed up before initiating my final turn.

I caught the problem early enough because I have a lot of time in the Discus 2 and it's a plane that behaves very well at low speed. However, I could easily see how a scenario like the one I experienced could result in a loss of control when the pilot is distracted from a normal pattern and landing..

Mike
  #10  
Old March 4th 14, 04:57 PM posted to rec.aviation.soaring
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Default Stall/spin and ground reference maneuvers

On Tuesday, March 4, 2014 6:43:31 AM UTC-8, wrote:
On Tuesday, March 4, 2014 8:09:16 AM UTC-5, wrote:

On Tuesday, March 4, 2014 4:54:30 AM UTC-8, John Godfrey (QT) wrote: On Tuesday, March 4, 2014 7:18:47 AM UTC-5, John Carlyle wrote: The insidious part is what you perceive in your peripheral vision unconsciously. True. Peripheral vision is terrible at detail but very good at picking up angular motion. Plus, last time I checked I was looking pretty close to down the wing as I initiated the turn from base to final. Aren't you supposed to look at the runway, not straight ahead into the countryside, on base leg? Once you're established on final there's not much turning anyway. 9B




If you wait till you are wing is almost aligned with the runway, it is likely to be a bit late, commonly leading to a rushed, and possibly skidded turn.



Yup - I used "pretty close" as a qualifier. Your gaze is somewhere between down the wing and over the nose depending on the pattern. In any case it's likely the motion of the wing against the background will end up in your peripheral view.

Airspeed and coordination - it's only two items, yet so many people lose track of one or the other or both.

9B
 




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