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

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

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

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

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

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

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

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

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

Teaching low time students to make less than full spoiler deployments early on final, then leaving them alone so that they can concentrate a good landing that may not be in the exact desired spot may be a good way to start.

Most landing issues are the result of choices made much earlier in the pattern. Tighten up the instruction in the rest of the pattern.

There are too many variables for new students to adjust at the same time, so nail some of them down, airspeed, turn to base altitude, turn to final altitude. You can loosen those up later. Fine control of the spoilers near the ground shouldn't be attempted for awhile.

Tail first or main wheel landings, those are just style points, either can be done gently. Work on the decisions made earlier to result in some consistency that the students can handle without banging up the aircraft.