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