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Landing with reduced airbrake



 
 
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  #1  
Old May 15th 18, 03:33 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 22
Default Landing with reduced airbrake

Hi guys,

Our club is having a discussion about the merits of reducing airbrake on
short final (well before the flare) in order to reduce the rate of descent
on
the last part of finals - in particular after using full airbrake to
correct an
overshoot i.e. you are still overshooting but reduce the airbrake to the
normal 1/2 to 2/3 range & just accept the overshoot.

This relates in particular to gliders which have a 2 point attitude which
is
quite low e.g. DG-1001 (nosewheel with retractable main) & LS8 .. a fully-
held off low energy landing in these types results in touching tail first,
and
in concert with a high rate of descent with full airbrake makes a hard tail

strike more likely.

Any thoughts or similar experience?

Cheers,

Richard McLean
Beverley Soaring Society
Western Australia

  #2  
Old May 15th 18, 03:56 AM posted to rec.aviation.soaring
son_of_flubber
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Posts: 1,550
Default Landing with reduced airbrake

Your question was recently kicked around in this forum

https://groups.google.com/forum/#!searchin/rec.aviation.soaring/Round$20out$20and$20flare$20with$20fully$20open$20 spoilers$20in$20a$20PW-6|sort:date/rec.aviation.soaring/m7AnPvT2knQ/5AXqN0EyCQAJ
  #3  
Old May 15th 18, 04:06 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 22
Default Landing with reduced airbrake

Ah ok, must have missed that one - thanks!

At 02:56 15 May 2018, son_of_flubber wrote:
Your question was recently kicked around in this forum

https://groups.google.com/forum/#!searchin/rec.aviation.soaring/Round$

20out$20and$20flare$20with$20fully$20open$20spoile rs$20in$20a$20PW-
6|sort:date/rec.aviation.soaring/m7AnPvT2knQ/5AXqN0EyCQAJ



  #4  
Old May 15th 18, 04:19 AM posted to rec.aviation.soaring
Richard McLean[_2_]
external usenet poster
 
Posts: 22
Default Landing with reduced airbrake


Hi again flubber,

I just re-read (most of!) that thread .. an I do remember it now.

It doesn't really address my question which is (to paraphrase):

In gliders with a low angle of attack 2 point attitude (e.g. DG-1001 & LS8)

does anyone else find that trying to land with lots of airbrake inevitable

results in a tail-strike, and therefore reducing the airbrake to (let's
say) 1/2
at around 100 ft or so is advsed?

Cheers,

Richard

At 02:56 15 May 2018, son_of_flubber wrote:
Your question was recently kicked around in this forum

https://groups.google.com/forum/#!searchin/rec.aviation.soaring/Round$

20out$20and$20flare$20with$20fully$20open$20spoile rs$20in$20a$20PW-
6|sort:date/rec.aviation.soaring/m7AnPvT2knQ/5AXqN0EyCQAJ



  #5  
Old May 15th 18, 05:13 AM posted to rec.aviation.soaring
kirk.stant
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Posts: 1,260
Default Landing with reduced airbrake

On Monday, May 14, 2018 at 10:30:05 PM UTC-5, Richard McLean wrote:
Hi again flubber,

I just re-read (most of!) that thread .. an I do remember it now.

It doesn't really address my question which is (to paraphrase):

In gliders with a low angle of attack 2 point attitude (e.g. DG-1001 & LS8)

does anyone else find that trying to land with lots of airbrake inevitable

results in a tail-strike, and therefore reducing the airbrake to (let's
say) 1/2
at around 100 ft or so is advsed?


I'm not sure why the concern for a tail-first touchdown. Unless you snatch the stick back at the last moment, or are really slow and stalled and basically falling, a tailwheel first touchdown (when fully held off with low descent rate) is not going to hurt the plane - and guarantees the lowest touchdown speed and no bounce, if that is the goal, by rotating the wing to a lower AOA when the tail touches.

I try for the tail to touch first when I land my LS6, and at most it touches just before the main. Really hard to get that tail down further!

That being said, if going into a really short field, I want a good sink rate and the tail touching first for a really short landing run. You can burn off a bit of energy by a firm touchdown (just don't get carried away!)

If you have the luxury of easing off the brakes on final, then you are going for style points instead of landing distance, and it's more a matter of how much brake you like out when you flare and land. But not a good idea to be sawing on the airbrakes on short final!

Cheers

Kirk
66
  #6  
Old May 15th 18, 05:42 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 22
Default Landing with reduced airbrake

On Tuesday, 15 May 2018 12:13:46 UTC+8, kirk.stant wrote:
On Monday, May 14, 2018 at 10:30:05 PM UTC-5, Richard McLean wrote:
Hi again flubber,

I just re-read (most of!) that thread .. an I do remember it now.

It doesn't really address my question which is (to paraphrase):

In gliders with a low angle of attack 2 point attitude (e.g. DG-1001 & LS8)

does anyone else find that trying to land with lots of airbrake inevitable

results in a tail-strike, and therefore reducing the airbrake to (let's
say) 1/2
at around 100 ft or so is advsed?


I'm not sure why the concern for a tail-first touchdown. Unless you snatch the stick back at the last moment, or are really slow and stalled and basically falling, a tailwheel first touchdown (when fully held off with low descent rate) is not going to hurt the plane - and guarantees the lowest touchdown speed and no bounce, if that is the goal, by rotating the wing to a lower AOA when the tail touches.

I try for the tail to touch first when I land my LS6, and at most it touches just before the main. Really hard to get that tail down further!

That being said, if going into a really short field, I want a good sink rate and the tail touching first for a really short landing run. You can burn off a bit of energy by a firm touchdown (just don't get carried away!)

If you have the luxury of easing off the brakes on final, then you are going for style points instead of landing distance, and it's more a matter of how much brake you like out when you flare and land. But not a good idea to be sawing on the airbrakes on short final!

Cheers

Kirk
66


Gday Kirk,

The concern is that students are breaking tailwheels in our DG-1001. The latest one probably form a loss of energy after a higher than optimal flare.

We have an old DG-1000 with a much higher 2 point nose attitude and it hasn't been an issue in 10 years or so .. but our brand-new DG-1001 (with nosewheel & much lower main wheel) has a much lower 2 point attitude which means that with a high rate of descent e.g. full brake and/or too slow the glider can touch down heavily on the tailwheel & it bursts.

One suggestion was that we limit the rate of descent for students by getting them to reduce airbrakes prior to the landing - even if they are still overshooting. A very experienced pilot suggested reducing the airbrake (if it's full for an overshoot) at around 100 ft to moderate the rate of descent and help prevent the tail-strike described. His theory is that some gliders with a small 2 point attitude are more prone to this.

Cheers,

Richard
  #7  
Old May 15th 18, 05:20 AM posted to rec.aviation.soaring
Scott Williams
external usenet poster
 
Posts: 198
Default Landing with reduced airbrake

On Monday, May 14, 2018 at 9:45:05 PM UTC-5, Richard McLean wrote:
Hi guys,

Our club is having a discussion about the merits of reducing airbrake on
short final (well before the flare) in order to reduce the rate of descent
on
the last part of finals - in particular after using full airbrake to
correct an
overshoot i.e. you are still overshooting but reduce the airbrake to the
normal 1/2 to 2/3 range & just accept the overshoot.

This relates in particular to gliders which have a 2 point attitude which
is
quite low e.g. DG-1001 (nosewheel with retractable main) & LS8 .. a fully-
held off low energy landing in these types results in touching tail first,
and
in concert with a high rate of descent with full airbrake makes a hard tail

strike more likely.

Any thoughts or similar experience?

Cheers,

Richard McLean
Beverley Soaring Society
Western Australia


Hey Richard,
In my very limited experience and humble opinion, any medium to large spoiler changes made after overflying the aim point and just above the ground (say 5 feet or less)only complicate the landing and promote P.I.O.s (for me anyway)
I have been transitioning from an SHK to a std Cirrus, with an increased wing loading by about 45%. I have found the emphasis on low energy landing and 'delaying the touchdown' very helpful. In short, just before touchdown is a little late to shed excess energy.
So, if safe to do so, accept the overshoot in favor of a desirable soft touchdown. Of course, if limited in 'runout room' adjust accordingly.
Best of luck,
Scott
only induce
  #8  
Old May 15th 18, 05:44 AM posted to rec.aviation.soaring
Richard McLean[_2_]
external usenet poster
 
Posts: 22
Default Landing with reduced airbrake

On Tuesday, 15 May 2018 12:20:38 UTC+8, Scott Williams wrote:
On Monday, May 14, 2018 at 9:45:05 PM UTC-5, Richard McLean wrote:
Hi guys,

Our club is having a discussion about the merits of reducing airbrake on
short final (well before the flare) in order to reduce the rate of descent
on
the last part of finals - in particular after using full airbrake to
correct an
overshoot i.e. you are still overshooting but reduce the airbrake to the
normal 1/2 to 2/3 range & just accept the overshoot.

This relates in particular to gliders which have a 2 point attitude which
is
quite low e.g. DG-1001 (nosewheel with retractable main) & LS8 .. a fully-
held off low energy landing in these types results in touching tail first,
and
in concert with a high rate of descent with full airbrake makes a hard tail

strike more likely.

Any thoughts or similar experience?

Cheers,

Richard McLean
Beverley Soaring Society
Western Australia


Hey Richard,
In my very limited experience and humble opinion, any medium to large spoiler changes made after overflying the aim point and just above the ground (say 5 feet or less)only complicate the landing and promote P.I.O.s (for me anyway)
I have been transitioning from an SHK to a std Cirrus, with an increased wing loading by about 45%. I have found the emphasis on low energy landing and 'delaying the touchdown' very helpful. In short, just before touchdown is a little late to shed excess energy.
So, if safe to do so, accept the overshoot in favor of a desirable soft touchdown. Of course, if limited in 'runout room' adjust accordingly.
Best of luck,
Scott
only induce


Thanks Scott,

Not suggesting any airbrake/spoiler changes near the aiming point - much earlier at about 100ft only.

Cheers,

Richard
  #9  
Old May 15th 18, 12:25 PM posted to rec.aviation.soaring
Peter F[_2_]
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Posts: 56
Default Landing with reduced airbrake

If your pupills are regularly approaching with full brake then they need to
improve their circuit planning rather than changing airbrake setting at
lowish level.

The last thing they should be doing is getting into the habit of
approaching too high / too fast then reducing brake. This will eventually
lead to them running into the hedge of a short field when outlanding

Regards

PF



  #10  
Old May 16th 18, 02:36 AM posted to rec.aviation.soaring
Richard McLean[_2_]
external usenet poster
 
Posts: 22
Default Landing with reduced airbrake

On Tuesday, 15 May 2018 19:30:07 UTC+8, Peter F wrote:
If your pupills are regularly approaching with full brake then they need to
improve their circuit planning rather than changing airbrake setting at
lowish level.

The last thing they should be doing is getting into the habit of
approaching too high / too fast then reducing brake. This will eventually
lead to them running into the hedge of a short field when outlanding

Regards

PF


OK, I think I need to re-phrase my question .. I understand everything you're saying (I'm an experienced instructor) but my question is not about how to teach circuits/approaches/landings it's whether anyone else flying performance "training" gliders like the DG-1000 has had lot's of student tail-strikes, and whether there is any merit in reducing the airbrake to avoid the need for a tail-first high rate of descent landing?

We have 2 DG-1000's - an older tail-dragger with a high undercarriage which lands only slightly tail-first in a fully held-off low energy landing, and a newer nose-wheel version with a lower height main wheel which seems to land much harder on the tail - hence a possible problem with bursting tail wheels when a student lands heavy from correcting an overshoot with nearly full air-brake - we just had our first one.

I suspect that the new nose wheel configuration DG-1000 has a lower wing incidence wing than most traditional trainers (for performance) & with the deletion of the original high main wheel configuration this has now resulted in an aircraft more susceptible to hard tail-strikes .. and as we have purchased it as a primary trainer I'm trying to determine if we need to restrict the amount of air-brake used by students when correcting overshoots in order to avoid tail-strikes/burst tail-wheels. We have a long runway, so it would just mean a long push-back with lots of time to debrief what went wrong with the overshoot!
 




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