Landing gear doors

OSCARDEUCE · #1 08-16-04, 08:23 AM

My landing gear doors are not closing after lowering the landinig gear. The gear seems to cycle normally retracting. The gear goes up doors seem to close ( based on flying characteristics) and the handle returns to neutral. When the gear is lowered the gear goes down I get a green light, but the doors do not close. I gear handle does not return to neutral. I cannot move the doors using the hand pump, it is quite stiff with booth the master on and off. Any ideas which switch/solenoid is malfunctioning?
Thnks
Tom

skymstr02 · #2 08-16-04, 12:50 PM

Get your dash 2, Maintenance Manual and locate the hydraulic solenoids on the back of the hydraulic power pack. Get new "O" rings handy. Remove the solenoids, along with the associated wiring (mark the wires before removing). Clean the solenoids and pistons with stoddard solvent (Varsol), re assemble with new seals, jack the aircraft and swing the gear.

If you're not comfortable doing this, visit your local friendly A&P. By the way, this is not preventative maintenace per FAR 43, my lawyer made me say that!

OSCARDEUCE · #3 08-16-04, 02:11 PM

Sounds like a plan, I'll do it with the upcoming annual with my A/P.Thanks for the help.

kevin · #4 08-16-04, 02:32 PM

Oscardeuce,

I guess it is obvious, but in case not, you should not fly it like that. If the handle does not return to neutral, the pump is probably continuing to operate, and you could burn it up, costing a lot more than O-rings.

Wasn't sure how far out your "upcoming annual" is.

Kevin

OSCARDEUCE · #5 08-16-04, 02:36 PM

the handle not returning to neutral was my first indication of trouble. i have a pretty good feel for how long it takes to cycle and it was awry. Thanks

stackj · #6 08-16-04, 11:37 PM

O2,

I am speaking from a 337B, but this may well apply to the O2 as well.

When hydraulic pressure is applied to the system, the landing gear doors are either forced open or closed.

Let's put the gear handle up. First, hydraulic pressure is applied to the landing gear door actuators. The pressure is applied in the OPEN direction as the Landing gear door solenoid is not actuated.

When all three gear are up, power is applied from the bus, through the nose gear up switch, then the right main gear up switch and finally the left gear up switch to a switch on the power pack. With the gear handle in the UP position, this switch then applies power to the Landing gear door solenoid, causing hydraulic pressure to be applied to the doors in the CLOSE direction. Looks like this function is working OK for you.

Now let's put the gear handle down. First, hudraulic pressure is applied to the landing gear door actuators. The pressure is again applied in the OPEN direction as the Landing gear door solenoid is not actuated.

When all three gear are down, power is applied from the bus, through the nose gear down switch, then the right main gear down switch and finally the left gear down switch to the same switch on the power pack. With the gear handle in the DOWN position, this switch then applies power to the Landing gear door solenoid, causing hydraulic pressure to be applied to the doors in the CLOSE direction.

This is apparently not happening for you. The most likely cause is that one of these four switches is not functioning correctly or a wire is broken somewhere in this circuit.

Be very careful. Position of all these switches is critical! If you find a broken wire, you can usually repair it without moving a switch. If a switch has failed, MAKE SURE YOUR MECHANIC IS FAMILIAR WITH YOUR GEAR SYSTEM BEFORE ALLOWING HIM/HER TO MOVE OR REPLACE A SWITCH.

travis · #7 08-17-04, 12:05 AM

Hi,

I just had a version of this problem! The gear doors would not close after the gear retracted.

I found that the answer is not in the sequencing valve but in the door solenoid switch. I think that the part was $6 (cheep anyway)

If the doors close one way and not the other, but you get a positive lock light (up and down) then the problem is either the wire or the switch. It is located on the left side of the power pack and can be herd when the handle is moved through the neutral position (do not move the handle through the neutral position with either of the engines running or with electrically operated gear).

_travis

hew · #8 08-10-14, 01:17 AM

OMG, this problem has followed this airplane round the world and it seems over 10 years. It appears it had two intermittent in-flight faulty up-lock switches. (That's the ones on the up-lock hooks). I replaced both these switches and no more problem. Unfortunately I replaced only one at a time which cured the problem for a little while, all the time the second switch was failing more often as the doors would not close until the handle was recycled (sometimes twice).
It seems to me that vibration in flight was causing the switches to fault, they wouldn't on the ground or even on the test bench. It's a cheap fix, probably worth doing before anything else. On the positive side, it did mean I had the power pack overhauled, emptied of 50 years of sediment and the 72 O rings replaced which is probably going to save me some grief in the future.
If you want to see what this airplane is up to now go to www.outbackovernight.com