Question about spoilers and pitch stability

In Europe standard practice is to teach fully held off landings, touching down just a fraction over stall speed in a 2 point attitude. Do the incidents referred to result from teaching a 'flown on' landing?

The fully held off approach results in far less energy to do damage if you hit a bump in an off field landing, or to generate a bounce. My flight manuals recommend it. I think there is debate about which technique involves greater risk of a PIO.

On Sunday, February 3, 2013 10:50:16 AM UTC-7, waremark wrote:
In Europe standard practice is to teach fully held off landings, touching down just a fraction over stall speed in a 2 point attitude. Do the incidents referred to result from teaching a 'flown on' landing?



The fully held off approach results in far less energy to do damage if you hit a bump in an off field landing, or to generate a bounce. My flight manuals recommend it. I think there is debate about which technique involves greater risk of a PIO.

You are absolutely correct. A 'held off' landing with a two point contact is the way to do it. Even contact with the tail wheel a few cm lower than the main wheel won't hurt anything.

Where I've seen the too-fast landings become a habit is where a well intentioned instructor rants on endlessly about keeping a high airspeed in the pattern without defining "pattern" and without ever explaining the meaning of the yellow triangle on the ASI. Students and others may take this to mean the ideal airspeed on final approach is in Mach numbers. This has resulted in many overshoot accidents in addition to the Grob "PIO/PIB".

Final approach is where a pilot transitions from the pattern and sets up the touchdown. Short-final "over-the-fence" airspeed should be just above the yellow triangle which guarantees the correct touchdown attitude.

For those who haven't read their manuals, the yellow triangle marks the manufactures recommended minimum approach airspeed at maximum flying weight but without water ballast. That means you'll have just enough energy for a flare and hold-off.

On Sunday, February 3, 2013 12:50:16 PM UTC-5, waremark wrote:
In Europe standard practice is to teach fully held off landings, touching down just a fraction over stall speed in a 2 point attitude.

I have a question. Assume strong turbulence such that a 70 knot speed in the pattern is needed to obtain control authority. Once the flair is correctly executed and the glider is flying level in ground effect 6-12" off the ground, does the glider become less vulnerable to turbulence because it is in ground effect, and therefore would control authority be maintained as the glider slows to stall speed?

I understand that once the pilot is flying level 6-12" above the runway at 70 knots (at that point the plane has zero vertical velocity) that he can very gradually lower the center wheel to the runway without 'bouncing". The advantage of lowering the wheel to the runway is two-fold. 1)The turbulence can no longer slam the wheel down onto the runway (it is already there). 2)The pilot can use the wheel brake and full spoilers to stop the glider as quickly as possible, thus minimizing runout and minimizing the time exposed to turbulence near the ground.

If the pilot chooses to reduce speed from 70 knots to stall speed with the wheel off the ground, he has a longer runout, the possibility of being slammed to the pavement by a downdraft, and a longer period of time vulnerable to unpredictable turbulence.

In short, I understand that there are advantages to "landing hot". I also understand that if a pilot touches down with too much vertical velocity, that he will 'bounce'. If the vertical velocity is low enough, you will not 'bounce' not matter how high the horizontal velocity.

(I understand that the 'bounce' is caused by an increase in AOA, caused by rotation around the center wheel, caused by a CG behind the center wheel, too much vertical velocity, and therefore too much momentum pressing the rear wheel down and increasing the AOA. And of course enough horizontal speed such that the increased AOA causes the wheel to leave the ground.)

I want to reinterate that I'm asking a question and just stating my very possilbly fractured understanding. This topic is of great interest to me because I'm in the process of transitioning to a glass ship and I have a lot of training time in SGS (There seems to be some vague correlation between transitioning from SGS to glass and landing related PIOs.)

On Sunday, February 3, 2013 12:00:41 PM UTC-7, son_of_flubber wrote:
On Sunday, February 3, 2013 12:50:16 PM UTC-5, waremark wrote:

In Europe standard practice is to teach fully held off landings, touching down just a fraction over stall speed in a 2 point attitude.



I have a question. Assume strong turbulence such that a 70 knot speed in the pattern is needed to obtain control authority. Once the flair is correctly executed and the glider is flying level in ground effect 6-12" off the ground, does the glider become less vulnerable to turbulence because it is in ground effect, and therefore would control authority be maintained as the glider slows to stall speed?



I understand that once the pilot is flying level 6-12" above the runway at 70 knots (at that point the plane has zero vertical velocity) that he can very gradually lower the center wheel to the runway without 'bouncing". The advantage of lowering the wheel to the runway is two-fold. 1)The turbulence can no longer slam the wheel down onto the runway (it is already there). 2)The pilot can use the wheel brake and full spoilers to stop the glider as quickly as possible, thus minimizing runout and minimizing the time exposed to turbulence near the ground.



If the pilot chooses to reduce speed from 70 knots to stall speed with the wheel off the ground, he has a longer runout, the possibility of being slammed to the pavement by a downdraft, and a longer period of time vulnerable to unpredictable turbulence.



In short, I understand that there are advantages to "landing hot". I also understand that if a pilot touches down with too much vertical velocity, that he will 'bounce'. If the vertical velocity is low enough, you will not 'bounce' not matter how high the horizontal velocity.



(I understand that the 'bounce' is caused by an increase in AOA, caused by rotation around the center wheel, caused by a CG behind the center wheel, too much vertical velocity, and therefore too much momentum pressing the rear wheel down and increasing the AOA. And of course enough horizontal speed such that the increased AOA causes the wheel to leave the ground.)



I want to reinterate that I'm asking a question and just stating my very possilbly fractured understanding. This topic is of great interest to me because I'm in the process of transitioning to a glass ship and I have a lot of training time in SGS (There seems to be some vague correlation between transitioning from SGS to glass and landing related PIOs.)

I hope our European friends jump in too. The following is based on years of experience at Boulder in wildly turbulent west wind rotors.

I don't think a "hot" landing has any value. It just means you'll float down the runway in ground effect while you are vulnerable to those gusts and with enough energy to seriously damage the glider. Better to get it down and stopped and that can't happen until the glider slows.

With a little practice, you'll find a glider can be slowed sharply with a few seconds of full airbrake while raising the nose to maintain the glide path just before entering ground effect. This can be done on short final to hit the recommended approach speed allowing the pattern itself to be flown at any speed the pilot deems safe for the gustiness.

This discussion is about nose wheel gliders where "hot" landings put the glider on the nose wheel first.

As far as I know the ASK-21 has such geometry that it will not take off with the two front wheels on the ground. This would imply that it produces no lift upwards, and that only making the
nosewheel touch the ground is very hard.

I question the existence of downdrafts during flaring... Where would the air in the downdraft go when you are already so low?

On Sun, 3 Feb 2013 11:54:33 -0800 (PST), Bill D
wrote:

I hope our European friends jump in too. The following is based on years of experience at Boulder in wildly turbulent west wind rotors.

I don't think a "hot" landing has any value. It just means you'll float down the runway in ground effect while you are vulnerable to those gusts and with enough energy to seriously damage the glider. Better to get it down and stopped and that can't happen until the glider slows.

With a little practice, you'll find a glider can be slowed sharply with a few seconds of full airbrake while raising the nose to maintain the glide path just before entering ground effect. This can be done on short final to hit the recommended approach speed allowing the pattern itself to be flown at any speed the pilot deems safe for the gustiness.

This discussion is about nose wheel gliders where "hot" landings put the glider on the nose wheel first.


From a European (German) point of view, I can only agree.

Even when it's pretty turbulent it is not necessary to fly faster than
60 kts with a G103. Even if one is faster, bleeding off excessive
speed with full airbrakes during the flare is very simple without any
danger of a PIO.

I am absolutely sure that these PIOs on the G103 (which is one of the
most forgiving basic trainers available) are a result of lacking
training.
This kind of accident is completely unheard of in Germany where nearly
*any* student pilot is trained from the beginning that any landing
where the tail wheel does not touch down first is a bad landing.



Andreas

Andreas, this is the US where I've had highly experienced instructors tell me that a landing where the tailwheel touches first is dangerous and likely to damage the glider.

Being a dick I just told them they were wrong and continue to land gliders that way.

Of course, when you are teaching no-spoiler, slipped patterns to a landing in a Grob 103, minimum energy landings are the least of your problems! Have to get that main wheel down before running off the 9000' runway!

Cheers

Kirk
66

On Thursday, February 14, 2013 3:18:05 PM UTC-7, kirk.stant wrote:
Andreas, this is the US where I've had highly experienced instructors tell me that a landing where the tailwheel touches first is dangerous and likely to damage the glider.



Being a dick I just told them they were wrong and continue to land gliders that way.



Of course, when you are teaching no-spoiler, slipped patterns to a landing in a Grob 103, minimum energy landings are the least of your problems! Have to get that main wheel down before running off the 9000' runway!



Cheers



Kirk

66

I've more than once heard "highly experienced instructors" tell their students "only crazy people go cross country".

As long as it's so easy to meet the FAA requirements for glider instructor certificates, we'll keep hearing these things from them.

Hi Kirk,

On Thu, 14 Feb 2013 14:18:05 -0800 (PST), "kirk.stant"
wrote:

Andreas, this is the US where I've had highly experienced instructors tell me that a landing where the tailwheel touches first is
dangerous and likely to damage the glider.

Being a dick I just told them they were wrong and continue to land gliders that way.


How dare you....!
As we would say in German: Pfui...!


Of course, when you are teaching no-spoiler, slipped patterns to a landing in a Grob 103, minimum energy landings are the least of your problems!
Have to get that main wheel down before running off the 9000' runway!

These things are really being taught to student pilots?
Faszinating.
Do they also teach them no-elevator landings?


No-spoiler landings are my hobby, I'm doing them in the ASK-21 and the
Ka-8 at my club's annual precision landing competition all the time.
Cannot remember when I missed the mark (main-wheel touchdown) for more
than 70 ft.

But the safety margin is very, very thin and does not allow any
mistake. Not suited at all for a student pilot.
But they are fun and guarantee the admiration of the comrades if you
and your glider happen to survive. Which, unfortunately, is not always
the case...


Cheers
Andreas

On Thursday, February 14, 2013 7:41:44 PM UTC-8, Andreas Maurer wrote:
Hi Kirk, On Thu, 14 Feb 2013 14:18:05 -0800 (PST), "kirk.stant" wrote: Andreas, this is the US where I've had highly experienced instructors tell me that a landing where the tailwheel touches first is dangerous and likely to damage the glider. Being a dick I just told them they were wrong and continue to land gliders that way. How dare you.....! As we would say in German: Pfui...! Of course, when you are teaching no-spoiler, slipped patterns to a landing in a Grob 103, minimum energy landings are the least of your problems! Have to get that main wheel down before running off the 9000' runway! These things are really being taught to student pilots? Faszinating. Do they also teach them no-elevator landings? No-spoiler landings are my hobby, I'm doing them in the ASK-21 and the Ka-8 at my club's annual precision landing competition all the time. Cannot remember when I missed the mark (main-wheel touchdown) for more than 70 ft. But the safety margin is very, very thin and does not allow any mistake. Not suited at all for a student pilot. But they are fun and guarantee the admiration of the comrades if you and your glider happen to survive. Which, unfortunately, is not always the case... Cheers Andreas

Slips to landing are part of the Practical Test Standard in the USA, so yes, they teach students to do it.