DG-1000 undercarriage collapses and inadvertent extensions ?

At 01:18 24 April 2007, Jack wrote:
Derek Copeland wrote:

Getting a big group of people together to lift a stranded
DG1000 off the ground after an U/C collapse, so that
the wheel can be lowered, has almost become a routine
occurrence at our club!

How do you go about this, in detail?

You ask them very politely! You get some of them to
squat under the mainspar and stand up at the appropriate
moment while others lift on the leading edges of the
wings. One person is required to operate the U/C lever.
The turbo version is significantly heavier to lift.


Sometimes the U/C locks down quite easily, but on
other
occasions it’s like pushing against a brick wall!
I
thought that it might be related to airspeed, as you
have to push the wheel forward into the slipstream,
but on the last occasion I had difficulties slowing
down to the stall made no difference.


Have you tried under various g-load conditions?

Yes!

Derek C

At 01:18 24 April 2007, Jack wrote:

Derek Copeland wrote:


Getting a big group of people together to lift a stranded
DG1000 off the ground after an U/C collapse, so that
the wheel can be lowered, has almost become a routine
occurrence at our club!

How do you go about this, in detail?


You ask them very politely! You get some of them to
squat under the mainspar and stand up at the appropriate
moment while others lift on the leading edges of the
wings. One person is required to operate the U/C lever.
The turbo version is significantly heavier to lift.

An Archimedean approach requiring fewer, weaker people might be to
simply 'walk up' the fuselage from below, levering about the ship's
changing nose pivot point, until the gear can be lowered. Works with 15
meter ships. Protect the nose, of course. Not an original idea. YMMV.

Regards,
Bob Whelan

We have been told by our CFI not to do it the way Bob
suggests, although we have used this technique on other
gliders. I guess the reason is that the two wheeler
type main wheel sticks out an awfully long way, so
you may not be able to lift the tail high enough. Alternatively
it may risk damaging the nose or the tailboom.

If the undercarriage had been properly designed from
an engineering and ergonomic point of view, this procedure
wouldn't be necessary anyway! BTW the glider comes
with a gear up warning as standard, but quite a few
people (including me) have failed to lock the undercarriage
down properly, even with the warning going off. I thought
that a microswitch must have failed because the U/C
sounded as if it had locked down and the lever appeared
to be fully forward.

Derek Copeland

At 04:24 28 April 2007, Bob Whelan wrote:
At 01:18 24 April 2007, Jack wrote:

Derek Copeland wrote:


Getting a big group of people together to lift a stranded
DG1000 off the ground after an U/C collapse, so that
the wheel can be lowered, has almost become a routine
occurrence at our club!

How do you go about this, in detail?


You ask them very politely! You get some of them to
squat under the mainspar and stand up at the appropriate
moment while others lift on the leading edges of the
wings. One person is required to operate the U/C lever.
The turbo version is significantly heavier to lift.

An Archimedean approach requiring fewer, weaker people
might be to
simply 'walk up' the fuselage from below, levering
about the ship's
changing nose pivot point, until the gear can be lowered.
Works with 15
meter ships. Protect the nose, of course. Not an
original idea. YMMV.

Regards,
Bob Whelan

I have carried out a few more investigations on the
problem of locking the undercarriage down from the
front cockpit.

Basically if you can't get the palm of your left hand
at least level with the back of the undercarriage lever
when strapped in on the ground with the wheel down,
you probably won't be able to lock the U/C down in
flight. Pad yourself forward with firm cushions until
you can. The cushions have to be firm as you need something
to push against.

To put the wheel down twist the lever out and down,
and take a long hard run at it. If you keep the lever
too close to the cockpit wall, you risk jamming your
fingers against a bulkhead, just like I managed to
do the other week. The bruising has just about subsided!

If you think that the U/C has locked down properly,
then push the lever against the side wall, check that
it fits into the detent if fitted, or that the lever
is fully forward, and then briefly open the airbrakes
to see if the warning goes off. If it doesn't you should
be OK.

BTW people with long arms find it difficult to lock
the wheel up, as their elbows hit the seat back first.
I still think that the ergonomics of this system are
appalling.

Derek Copeland


At 09:12 28 April 2007, Derek Copeland wrote:
We have been told by our CFI not to do it the way Bob
suggests, although we have used this technique on other
gliders. I guess the reason is that the two wheeler
type main wheel sticks out an awfully long way, so
you may not be able to lift the tail high enough. Alternatively
it may risk damaging the nose or the tailboom.

If the undercarriage had been properly designed from
an engineering and ergonomic point of view, this procedure
wouldn't be necessary anyway! BTW the glider comes
with a gear up warning as standard, but quite a few
people (including me) have failed to lock the undercarriage
down properly, even with the warning going off. I thought
that a microswitch must have failed because the U/C
sounded as if it had locked down and the lever appeared
to be fully forward.

Derek Copeland

On Apr 15, 12:55 am, "Bernie" wrote:
Our DG-1000 at Southern Cross Gliding Club (Camden, NSW, Australia)
has experienced multiple occurences of both inadvertent retraction and
extension of the undercarriage. Typically the undercarrriage has
dropped down whilst in flight, in various modes including straight and
level in smooth air.
We have also had a collapse on outlanding in a moderately field, and
very recently the gear collpased seconds after the glider had been
wheeled into the hangar; luckily no-one was injured but the wings hit
adjacent gliders.
The local DG agent has stated that he has not heard of any other
reports of DG-1000 U/C problems; however recently we heard another
Australian DG-1000 at Beverley in W.A. experienced a collapse (and
it's only a few months old).
It appears the overcentre mechanism requires very careful adjustment
to prevent the extension problem, however no apparent cause for the
retraction problem has been found. We have continually cautioned
pilots to make sure the U/C handle is pushed flush with the fuselage
wall after putting the gear down.
We are wondering if any other clubs or owners have experienced this
problem?

I also had an uncommanded gear collapse of my DG-400 (did over $3,000
in damage). The repair shop could not find any problem with the gear
mechanism; the gas strut was ok and the detent mechanism, such as it
is, was properly adjusted. I solved the problem by installing a gate
deadbolt procured from a local hardware store. Cost: $3. A friend of
my had a similar mishap with his DG-400.

I posted a similar question on RAS over 9 years ago. The responses
fell into two categories:
1. It has never happened to me and it won't happen to you if the
glider is properly maintained.
2. It has happened to me X times.

I have not seen the mechanism on the DG-1000, but it sounds similar.
DG has made various design modifications to eliminate the problem, but
it sounds like they are still searching for the right receipe.

I recommend installing some sort of positive mechanical lock (with the
usual inspection sign-offs, paperwork, etc.) that can't possibly fail.

Tom