Originally Posted by
chevvron
I was on a 'late' duty on the day of '947s accident. It behove me to go out and carry out a runway inspection for the afternoon duty crew so I was able to examine the damage. Cameras were forbidden so I was unable to take a photo, but I noted that as well as the wrinkled upper wing skin, the prop appeared to have broken off at the reduction gear allowing it to bounce up and leave an impact mark squarely in the middle of the pilot's escape hatch.
On my earlier flight, I was sitting near the cockpit door and was able to observe the several handles and levers used by the navigator at various times so I'm not surprised it was possible to move one of them mistakenly when the undercarriage was retracted.
It takes a determined effort to retract the undercarriage on a Dak by mistake! A latch lever on the floor has first to be released from its clip and pulled up. This raises (by cables) spring-loaded latches which are sitting in both a fixed bracket on each bulkhead and slots in the end of the retraction jack rams. Then the gear retraction lever in the cockpit can be raised and the wheels come up hydraulically. It's impossible to select up without the latch lever being raised because of an inter-connect mechanism.
That's
three steps to get the gear up. I guess we all have bad days.
All I can think might have happened was the latch lever inadvertently pulled all the way up after being released from its clip (which raises the latches clear of the actuator slots instead of leaving them in spring lock). When that happens on the ground, a manual dog and catch mechanisn on the selector can return the latches to the safe spring-loaded engaged position
if the operator knows where it is. With the gear still selected down, 750-875 psi hydraulic pressure in the down lines
should keep the gear extended. In neutral, the fluid is trapped unless the lever is mis-timed on its shaft or the shear seals are leaking, both unlikely. If UP is selected, the gear will be unsafe and the red lights will illuminate, plus, if I remember correctly, a warning horn will sound if the throttles are below a certain position.
All this is conjecture, of course, it would be interesting to hear the first hand circumstances.