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Landing with reduced airbrake



 
 
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  #21  
Old May 16th 18, 11:58 PM posted to rec.aviation.soaring
George Haeh
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Posts: 3
Default Landing with reduced airbrake

The DG-1000 Club seems a good illustration of the law of unintended consequences. Having the fixed gear as far down as the retractable version would impose a significant drag penalty, but having it higher up imposes a higher takeoff and touchdown speed.

The electric gear version can fail to come down. The flight manual recommends practicing the emergency gear down mechanism periodically. I know of one gear up landing where the Instructor had not practiced the emergency gear down.
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  #22  
Old May 17th 18, 02:39 AM posted to rec.aviation.soaring
Richard McLean[_2_]
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Posts: 18
Default Landing with reduced airbrake

On Thursday, 17 May 2018 06:58:54 UTC+8, George Haeh wrote:
The DG-1000 Club seems a good illustration of the law of unintended consequences. Having the fixed gear as far down as the retractable version would impose a significant drag penalty, but having it higher up imposes a higher takeoff and touchdown speed.

The electric gear version can fail to come down. The flight manual recommends practicing the emergency gear down mechanism periodically. I know of one gear up landing where the Instructor had not practiced the emergency gear down.


This is what I think too - the original design had the high main-wheel but people wanted easier cockpit access so they gave it the lower main/nose wheel combination .. which has compromised the landing attitude. All well & good, but it does now expose the tail-wheel to some serious abuse by students! I guess any "do everything" performance glider is going to be compromised to some extent - in this case as a club ab-initio trainer. I still think the best mitigation (as an instructor) is to actively limit the rate of descent if required.
  #23  
Old May 17th 18, 02:43 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 22:21:48 UTC+8, Matt Herron Jr. wrote:
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.


Hi Matt, yes you give up the original aim point. This isn't ideal but better than damaging the aircraft? The debrief can cover off the reasons. Lots of bad landings are the result of not accepting that you stuffed up your original aiming point & concentrating on the actual landing.
  #24  
Old May 17th 18, 07:36 AM posted to rec.aviation.soaring
Bruce Hoult
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Posts: 868
Default Landing with reduced airbrake

On Thursday, May 17, 2018 at 1:43:09 PM UTC+12, Richard McLean wrote:
On Wednesday, 16 May 2018 22:21:48 UTC+8, Matt Herron Jr. wrote:
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.


Hi Matt, yes you give up the original aim point. This isn't ideal but better than damaging the aircraft? The debrief can cover off the reasons. Lots of bad landings are the result of not accepting that you stuffed up your original aiming point & concentrating on the actual landing.


I'd think if you were so high turning final that you can't get back on to a standard half brake approach by, say, 100m before crossing the fence then you've well and truly stuffed up the circuit. Especially in something with airbrakes as powerful as a DG1000 or Grob. You definitely should never be planning to carry full brake all the way down the approach ... that leave nothing in reserve for the unexpected.
  #25  
Old May 17th 18, 09:48 AM posted to rec.aviation.soaring
Jonathon May
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Posts: 19
Default Landing with reduced airbrake

At 06:36 17 May 2018, Bruce Hoult wrote:
On Thursday, May 17, 2018 at 1:43:09 PM UTC+12, Richard McLean wrote:
On Wednesday, 16 May 2018 22:21:48 UTC+8, Matt Herron Jr. wrote:
from my perspective, reducing airbrakes at 100' changes your glide

slop=
e and therefor aim point half way through final. So do you give up your
in=
itial aim point at 100', or do you have two aim points? Either option
seem=
s like a bad idea for students.
=20
Airbrake deployment should be a driven variable to maintain a correct

a=
pproach, not the other way around.
=20
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
rec=
over by closing the airbrakes.
=20
To me, it sounds like the tail strike problem is in the flair, not

the
=
use of airbrakes.
=20
Hi Matt, yes you give up the original aim point. This isn't ideal but

bet=
ter than damaging the aircraft? The debrief can cover off the reasons.
Lots=
of bad landings are the result of not accepting that you stuffed up your
o=
riginal aiming point & concentrating on the actual landing.

I'd think if you were so high turning final that you can't get back on to
a=
standard half brake approach by, say, 100m before crossing the fence

then
=
you've well and truly stuffed up the circuit. Especially in something

with
=
airbrakes as powerful as a DG1000 or Grob. You definitely should never be
p=
lanning to carry full brake all the way down the approach ... that leave
no=
thing in reserve for the unexpected.


Trick one
I have not flown the DG1001 neo yet but I have quite a lot of time in the
original DG1000,you need a step to get people in,if that is the angle for
2point landing them the newer versions going to land tail wheel first .

I have done hundreds of trial flights in an early DG500 that everyone said
was "over braked" ,in fact it could be .But as all I wanted was to get the
punters down safe without a hard landing I tend to add 5kns and gently fly
it on, on the main wheel.
The trouble with that is its not the correct method to teach landing to
pupils.

As I said tricky
My advice would be to buy a K21 or Duo xl ,they fly as you would expect.




  #26  
Old May 17th 18, 04:14 PM posted to rec.aviation.soaring
Papa3[_2_]
external usenet poster
 
Posts: 640
Default Landing with reduced airbrake

On Tuesday, May 15, 2018 at 11:47:10 PM UTC-4, 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.


I owned an LS8 for about 13 years, so figure about 450-500 takeoffs and landings. I don't remember anything special about the flare and touchdown. The POH is very clear that with airbrakes fully extended one needs to carry additional airspeed and that a slip with full airbrakes is not recommended.. That said, I never had any trouble stuffing the glider into some fairly short spaces.

I can see a scenario where the pilot is coming in right at the minimum approach speed and full divebrakes, mis-judging the roundout, and hauling back on the stick resulting in a very firm arrival. But the same applies to other gliders. I once borrowed a friends ASW-20 (original version) and demonstrated a max-performance approach with full flaps. Roundout, touchdown, and "oh sh***" all in one smooth motion :-)

P3
  #27  
Old May 18th 18, 02:40 AM posted to rec.aviation.soaring
Bruce Hoult
external usenet poster
 
Posts: 868
Default Landing with reduced airbrake

On Thursday, May 17, 2018 at 9:00:15 PM UTC+12, Jonathon May wrote:
At 06:36 17 May 2018, Bruce Hoult wrote:
On Thursday, May 17, 2018 at 1:43:09 PM UTC+12, Richard McLean wrote:
On Wednesday, 16 May 2018 22:21:48 UTC+8, Matt Herron Jr. wrote:
from my perspective, reducing airbrakes at 100' changes your glide

slop=
e and therefor aim point half way through final. So do you give up your
in=
itial aim point at 100', or do you have two aim points? Either option
seem=
s like a bad idea for students.
=20
Airbrake deployment should be a driven variable to maintain a correct

a=
pproach, not the other way around.
=20
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
rec=
over by closing the airbrakes.
=20
To me, it sounds like the tail strike problem is in the flair, not

the
=
use of airbrakes.
=20
Hi Matt, yes you give up the original aim point. This isn't ideal but

bet=
ter than damaging the aircraft? The debrief can cover off the reasons.
Lots=
of bad landings are the result of not accepting that you stuffed up your
o=
riginal aiming point & concentrating on the actual landing.

I'd think if you were so high turning final that you can't get back on to
a=
standard half brake approach by, say, 100m before crossing the fence

then
=
you've well and truly stuffed up the circuit. Especially in something

with
=
airbrakes as powerful as a DG1000 or Grob. You definitely should never be
p=
lanning to carry full brake all the way down the approach ... that leave
no=
thing in reserve for the unexpected.


Trick one
I have not flown the DG1001 neo yet but I have quite a lot of time in the
original DG1000,you need a step to get people in,if that is the angle for
2point landing them the newer versions going to land tail wheel first .

I have done hundreds of trial flights in an early DG500 that everyone said
was "over braked" ,in fact it could be .But as all I wanted was to get the
punters down safe without a hard landing I tend to add 5kns and gently fly
it on, on the main wheel.
The trouble with that is its not the correct method to teach landing to
pupils.

As I said tricky
My advice would be to buy a K21 or Duo xl ,they fly as you would expect.


Not necessary. All you need to do is fly close to the ground and gradually slow and increase the pitch until you are in the same attitude as you would be on the ground.

Assuming you have levelled out at the correct height for your undercarriage length it all works out just the same as any other glider. Main wheel is skimming just a few inches above the ground, once the AOA gets to the point that the tail wheel touches gently you physically can't increase the pitch more, and do the main will gently drop on.

Whether the glider is actually "stalled" at that point or not is irrelevant..

If you level out a DG1000 Club at the same height as you would a standard DG1000, and then slow until it stalls, then you're going to be dropping on hard from a foot up no matter what you do. Know how it looks out the window of your glider when it's on the ground!
  #28  
Old May 18th 18, 03:09 AM posted to rec.aviation.soaring
Richard McLean[_2_]
external usenet poster
 
Posts: 18
Default Landing with reduced airbrake

At 01:40 18 May 2018, Bruce Hoult wrote:
On Thursday, May 17, 2018 at 9:00:15 PM UTC+12, Jonathon May

wrote:
At 06:36 17 May 2018, Bruce Hoult wrote:
On Thursday, May 17, 2018 at 1:43:09 PM UTC+12, Richard

McLean wrote:
On Wednesday, 16 May 2018 22:21:48 UTC+8, Matt Herron Jr.

wrote:
from my perspective, reducing airbrakes at 100' changes your

glide
slop=3D
e and therefor aim point half way through final. So do you give up

your
in=3D
itial aim point at 100', or do you have two aim points? Either

option
seem=3D
s like a bad idea for students.
=3D20
Airbrake deployment should be a driven variable to maintain a

correc=
t
a=3D
pproach, not the other way around.
=3D20
Additionally, a shallower approach for the last 100' means you

are
way
=3D
more susceptible to wind shear, as you don't have much "extra"

glide to
rec=3D
over by closing the airbrakes.
=3D20
To me, it sounds like the tail strike problem is in the flair, not

the
=3D
use of airbrakes.
=3D20
Hi Matt, yes you give up the original aim point. This isn't ideal

but
bet=3D
ter than damaging the aircraft? The debrief can cover off the

reasons.
Lots=3D
of bad landings are the result of not accepting that you stuffed up

you=
r
o=3D
riginal aiming point & concentrating on the actual landing.

I'd think if you were so high turning final that you can't get back

on
t=
o
a=3D
standard half brake approach by, say, 100m before crossing the

fence
then
=3D
you've well and truly stuffed up the circuit. Especially in something

with
=3D
airbrakes as powerful as a DG1000 or Grob. You definitely should

never
b=
e
p=3D
lanning to carry full brake all the way down the approach ... that

leave
no=3D
thing in reserve for the unexpected.

=20
Trick one
I have not flown the DG1001 neo yet but I have quite a lot of time in

the
original DG1000,you need a step to get people in,if that is the

angle
f=
or
2point landing them the newer versions going to land tail wheel first

  #29  
Old May 18th 18, 07:00 AM posted to rec.aviation.soaring
Phil Plane
external usenet poster
 
Posts: 3
Default Landing with reduced airbrake

I guess the difference between the DG1000 with the tall gear and the DG 1000 with the short gear is similar to the difference between the Duo Discus with the short gear and the newer Duo X or XL with the tall gear. The minimum approach speed is a few knots faster with the short gear.

I regularly fly the original Duo, the Duo with the X wing and the short gear, a Duo X, and occasionaly the XL. The tall gear is the easiest.

Flying the short gear gliders after you're used to the tall gear you have to be careful not to land slow with the main still half a meter in the air.

Landing any of them like you're meant to (min speed all the way to the holdoff) and they're fine. Let the speed decay on short finals and the short gear will punish you worse than the tall gear.

I've flown the tall gear DG1000 a lot and like it. I haven't flown the short gear DG1000, but I have flown the DG500 and 505 with the short gear. I think the difference is comparable.

Tall is more forgiving and just generally better. Short lets old people get in the glider easier.
  #30  
Old May 18th 18, 08:24 AM posted to rec.aviation.soaring
Richard McLean[_2_]
external usenet poster
 
Posts: 18
Default Landing with reduced airbrake

On Friday, 18 May 2018 14:00:42 UTC+8, Phil Plane wrote:
I guess the difference between the DG1000 with the tall gear and the DG 1000 with the short gear is similar to the difference between the Duo Discus with the short gear and the newer Duo X or XL with the tall gear. The minimum approach speed is a few knots faster with the short gear.

I regularly fly the original Duo, the Duo with the X wing and the short gear, a Duo X, and occasionaly the XL. The tall gear is the easiest.

Flying the short gear gliders after you're used to the tall gear you have to be careful not to land slow with the main still half a meter in the air..

Landing any of them like you're meant to (min speed all the way to the holdoff) and they're fine. Let the speed decay on short finals and the short gear will punish you worse than the tall gear.

I've flown the tall gear DG1000 a lot and like it. I haven't flown the short gear DG1000, but I have flown the DG500 and 505 with the short gear. I think the difference is comparable.

Tall is more forgiving and just generally better. Short lets old people get in the glider easier.


Thanks for that Phil
 




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