SAS F50 gear collapse

[M609]

F50 with broken legs, happened at night when aircraft was parked at the gate at Oslo Gardermoen.

Pic: VG.no
Nasty bend in the fuselage abeam the props, and one aft of the rear door.
Gear pins anyone?
http://www.vg.no/pub/vgart.hbs?artid=160595

[ooizcalling]

Very Interesting ! Theoreticaly the over-centre action of the gear linkage should make this impossible regardless of the lack of gear pins or hydraulic pressure. You would have to ignore the warning decal and push them back through center before the retract motion could commence. Likewise if the gear lever is in the 'down' position (as it should be at this stage) then the hydraulic lines should be closed off to the 'retract' flow thus creating a hydraulic lock. hmmm. better look at the books again.

[Techman]

This has happened before. Same airline, same type. Seem to remember the cause being an internal leak in the gear selector valve.

[erikv]

With the overcentering action, this should not be able to happen with an internal leak either. With the props stationary, there is no hydraulic power and the overcentering mehanism is the only thing keeping the gear down.
I have heard of two other a/c where this happened as a result of a bet. The person who claimed that the overcentering mechanism can be manually overriden by pushing it up, won the bet obviously.
Erik.
PS Can't judge very well from the pics, but did both main gears go at the same time?

[espenjoh]

affirm, both at the same time.

more pics:

[rigpiggy]

The original F27 prototype "fairchild not fokker I think" with pneumatics had a misconnected line. during a engineering turnaround a mechanic heard a hiss from a vent, like a mechanic is wont to do he put his finger to the vent pressure built up and the main gear folded up just like that, it too broke it's back and was cut up for parts. I was told by the USAir guys that was how they got the front end for the sim there.

[banana head]

Oh dear!
I seem to recall an Aer Lingus F50 suffering a similar fate some years back in DUB.
Anyone else recall it - or was it all just a bad dream

[WHBM]

16 years old, fuselage frames broken right round, presume that's the last flight for that one then.

[erikv]

Originally Posted by espenjoh

affirm, both at the same time.

So much for my theory. Like to learn more as the investigation moves forward.