I could tell you weren't an Engineer though.
Fair enough!
Anyway, it may defy logic but I think I have correctly described the gear handle operation in the alternate gear extension checklist. Do you have another version of this checklist, perhaps?
Rem; Simulators and Lawyers understand checklists.....aeroplanes don't.
Well, we pretty much have to go by the book and the checklist from the operator side of things. And I agree with you that some of this stuff is fit for an attorney. The FAA and Boeing have been trying to go to 'integrated checklists' for systems malfunctions, e.g. if you lose C HYD, you will have to do alternate gear and flap extension so the procedures are rolled into one big checklist rather than having you hop around the QRH.
Earlier, even though you knew normal operation would not work, you would position the gear or flap controls, get a 'Disagree' light and it would lead you to a separate checklist with double negatives and other challenges for each inoperative item on the lost hydraulic system.
The new integrated checklists have a laundry list of other checklists that you
don't do, e.g. the 'Tailskid' checklist with loss of C HYD since it is an expected indication with the gear handle down and no center pressure.
The main landing gear door supports the weight of the retracted main gear when the landing gear system is depressurised.
More precisely, there is a gear support attached to each main gear door. When the door closes the gear support folds under and locks the main gear. The door is held closed by the door uplock hook. When the landing gear system is depressurised the weight of the gear rests upon the gear support.
During alternate extension, the uplock hook is released mechanically and the weight of the gear pushes the door open.
It is a little more sophisticated than the tyres resting on doors
Thanks for this explaination, I appreciate it.
Incorrect, Unlike the gear, it IS pressurised in flight. The retract pressure is maintained by the centre system with the tail skid retracted as the control valve is in the same position with the landing gear lever UP or OFF.
I was actually referring to the gear being unpressurized during flight but I didn't realize that the tailskid stayed pressurized, it sure increases the possibility that the leak was there it seems.
Years ago I did a crossing with the tailskid MEL'd. Seems like we took a couple of thousand pound performance hit on the runway limit weight and maybe a couple of percent on the fuel burn. The tailskid was locked down, maybe it was pinned somehow, it's been quite a while since we did this.