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Landing with reduced airbrake



 
 
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  #11  
Old May 16th 18, 02:36 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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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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  #12  
Old May 16th 18, 03:27 AM posted to rec.aviation.soaring
[email protected]
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Default Landing with reduced airbrake

I was taught to land the glidr in the same attitude as it sits on the ground. I have always followed this practice, and have 300 landings
with no problems. One particular DG 1000 owning club does not like me not holding off the glider until it stalls on, resulting in a tail wheel first landing.
I find this attitude plain stupid.
  #13  
Old May 16th 18, 03:37 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 18
Default Landing with reduced airbrake

On Wednesday, 16 May 2018 10:27:08 UTC+8, wrote:
I was taught to land the glidr in the same attitude as it sits on the ground. I have always followed this practice, and have 300 landings
with no problems. One particular DG 1000 owning club does not like me not holding off the glider until it stalls on, resulting in a tail wheel first landing.
I find this attitude plain stupid.


Thanks Mike. Do you ever find that if using more than 1/2 air-brake you need to reduce it before the flare? The theory is that slightly tail first is best, so that you're definitely low-energy & the nose pitches down rather than the reverse .. but I land my Astir 2 point if I can!

Cheers,

Richard
  #14  
Old May 16th 18, 04:35 AM posted to rec.aviation.soaring
George Haeh
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Default Landing with reduced airbrake

Newer gliders with powerful air brakes will lose airspeed rapidly in the flare. Flaring too high or from an inadequate airspeed, especially with powerful air brakes full on, can end in a hard landing.

Perhaps the tailplane in the taller gear variants of the DG-1000/1 produces more lift as it rotates around the main gear to cushion the tailwheel contact.

A less tall gear does increase the possibility of a tailwheel first landing.

Another consideration is the amount of tail ballast carried.

Have you noticed if there's a difference with heavier or lighter pilots in the front seat?

It might be useful to have two experienced pilots, one to video and take notes, to do landings at various airspeeds and CGs to determine optimal landing parameters - and determine what to avoid.
  #15  
Old May 16th 18, 04:47 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Default Landing with reduced airbrake

Thanks for that George - yes, a bit of experimentation might be a good idea.

One of our most experienced pilots says the LS8 requires an airbrake reduction to avoid excessive tail-first landings, so perhaps it's the same with this configuration DG-1000.

Cheers,

Richard

On Wednesday, 16 May 2018 11:35:57 UTC+8, George Haeh wrote:
Newer gliders with powerful air brakes will lose airspeed rapidly in the flare. Flaring too high or from an inadequate airspeed, especially with powerful air brakes full on, can end in a hard landing.

Perhaps the tailplane in the taller gear variants of the DG-1000/1 produces more lift as it rotates around the main gear to cushion the tailwheel contact.

A less tall gear does increase the possibility of a tailwheel first landing.

Another consideration is the amount of tail ballast carried.

Have you noticed if there's a difference with heavier or lighter pilots in the front seat?

It might be useful to have two experienced pilots, one to video and take notes, to do landings at various airspeeds and CGs to determine optimal landing parameters - and determine what to avoid.


  #16  
Old May 16th 18, 04:49 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 18
Default Landing with reduced airbrake

And no, we've only just started flying the glider, so no observations about differing pilot weights/CG position as yet.

On Wednesday, 16 May 2018 11:47:10 UTC+8, Richard McLean wrote:
Thanks for that George - yes, a bit of experimentation might be a good idea.

One of our most experienced pilots says the LS8 requires an airbrake reduction to avoid excessive tail-first landings, so perhaps it's the same with this configuration DG-1000.

Cheers,

Richard

On Wednesday, 16 May 2018 11:35:57 UTC+8, George Haeh wrote:
Newer gliders with powerful air brakes will lose airspeed rapidly in the flare. Flaring too high or from an inadequate airspeed, especially with powerful air brakes full on, can end in a hard landing.

Perhaps the tailplane in the taller gear variants of the DG-1000/1 produces more lift as it rotates around the main gear to cushion the tailwheel contact.

A less tall gear does increase the possibility of a tailwheel first landing.

Another consideration is the amount of tail ballast carried.

Have you noticed if there's a difference with heavier or lighter pilots in the front seat?

It might be useful to have two experienced pilots, one to video and take notes, to do landings at various airspeeds and CGs to determine optimal landing parameters - and determine what to avoid.


  #17  
Old May 16th 18, 06:03 AM posted to rec.aviation.soaring
[email protected]
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Posts: 22
Default Landing with reduced airbrake

I try to get the bulk of braking done during final, and to flare at about half brake. i havent however, had any problems with full brake landings.
I dont stress about not flying the glider on a bit either, and neverr have trouble with bounces.
I had a partciularly nasty experience in an old twin Astir, when a gust just after a fully held off landing lifted the nose and caused a very heavy landing, despite closing the brakes very quickly.
  #18  
Old May 16th 18, 06:11 AM posted to rec.aviation.soaring
Bruce Hoult
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Default Landing with reduced airbrake

On Wednesday, May 16, 2018 at 1:36:56 PM UTC+12, Richard McLean wrote:
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!


My club has had two of the DG1000 Club training gliders for a decade. We are also familiar with the full-spec DG1000 as a nearby club we often fly with has (had?) one.

I'm sure there's no difference in wing incidence between them. We were told as late as one week before our gliders went to the port that it was "not too late" to upgrade to retractable undercarriage, 20m tips (as well as the 18m we got), water etc.

It's simply that with the lower undercarriage the wing is at lower angle of attack *on the ground*. Not in flight.

It's very obvious when we've been flying both together on the same day that both the liftoff and touchdown speeds (and corresponding distances) for our training gliders are noticeably higher than for the glider with higher and retractable undercarriage.

I'm pretty sure we've had no more problem with burst tail wheel tyres than with any other glider .. the Grobs we had before the DGs, for example.

The important thing is that with the shorter undercarriage you are (or should be) nowhere near actual stall speed at touchdown. A "fully held off" landing is one in which you allow the nose pitch angle to increase in the hold off until it is the same as it is when sitting on the ground AND NOT MORE. If the main and tail wheels touch down together (or very slightly tail first) then there no no possibility of a bounce.

It is a slightly unfortunate aspect of these gliders that you shouldn't fully stall them on landing, and thus land a bit faster. But with correct technique of flying to the same attitude as they sit on the ground they are no problem.
  #19  
Old May 16th 18, 06:32 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 18
Default Landing with reduced airbrake

On Wednesday, 16 May 2018 13:11:12 UTC+8, Bruce Hoult wrote:
On Wednesday, May 16, 2018 at 1:36:56 PM UTC+12, Richard McLean wrote:
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!


My club has had two of the DG1000 Club training gliders for a decade. We are also familiar with the full-spec DG1000 as a nearby club we often fly with has (had?) one.

I'm sure there's no difference in wing incidence between them. We were told as late as one week before our gliders went to the port that it was "not too late" to upgrade to retractable undercarriage, 20m tips (as well as the 18m we got), water etc.

It's simply that with the lower undercarriage the wing is at lower angle of attack *on the ground*. Not in flight.

It's very obvious when we've been flying both together on the same day that both the liftoff and touchdown speeds (and corresponding distances) for our training gliders are noticeably higher than for the glider with higher and retractable undercarriage.

I'm pretty sure we've had no more problem with burst tail wheel tyres than with any other glider .. the Grobs we had before the DGs, for example.

The important thing is that with the shorter undercarriage you are (or should be) nowhere near actual stall speed at touchdown. A "fully held off" landing is one in which you allow the nose pitch angle to increase in the hold off until it is the same as it is when sitting on the ground AND NOT MORE. If the main and tail wheels touch down together (or very slightly tail first) then there no no possibility of a bounce.

It is a slightly unfortunate aspect of these gliders that you shouldn't fully stall them on landing, and thus land a bit faster. But with correct technique of flying to the same attitude as they sit on the ground they are no problem.


Thanks for that Bruce - by referring to the wing incidence I didn't mean that the 2 models were any different, just that the AoA in the 2 point attitude is different - exactly what you said. I was inplyingg that high-performance gliders like the DG-1000 probably have less wing/fuselage incidence that previous training aircraft .. less drag etc. etc.

Cheers,

Richard
  #20  
Old May 16th 18, 03:21 PM posted to rec.aviation.soaring
Matt Herron Jr.
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Default Landing with reduced airbrake

from my perspective, reducing airbrakes at 100' changes your glide slope and therefor aim point half way through final. So do you give up your initial aim point at 100', or do you have two aim points? Either option seems like a bad idea for students.

Airbrake deployment should be a driven variable to maintain a correct approach, not the other way around.

Additionally, a shallower approach for the last 100' means you are way more susceptible to wind shear, as you don't have much "extra" glide to recover by closing the airbrakes.

To me, it sounds like the tail strike problem is in the flair, not the use of airbrakes.
 




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