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#1
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You might check that the nose strut is properly serviced. Since the strut retracts forward the aero load on the strut will collapse the strut a small amount if not serviced properly and cause a problem with the uplock switch.
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#2
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Gear problem
Start thinking about the engine driven pump.
Had very similar problems. All symptoms same as yours. Only think different was that I am not so brave to keep bringing the gear up and down like that. Like you, we started with the actuators, which were leaking and in desperate need of rebuild. After spending lots of money on that, and everything testing fine with the hand pump, we still had the same problem in the air. With no other alternative, my mechanic took off the engine driven pump. It was scrap metal, amazing it worked at all. It built enough pressure to drop the gear, but not enough to reliably bring it back up and close the gear doors. Got a rebuilt, changed the screen (screen was clogged with molten bits of the pump) and now it is fine. Of course, there is always more to the story than what I can post here. In fact, my problem featured prominently in Don Nieser's presentation about O-2 maintenance at Oshkosh this year. |
#3
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Long term under carriage problem
Hi all I would like to explain a problem and after sometime how I over come this
Problem. My undercarriage would retract up light would come on for moment then off. Rear doors would be partially open. Would check fluid level and might be bit low, top up and bleed system. All would be well for a while then same thing this went on and off for couple of years. But each time we jacked plane and tested all worked fine. The problem turned out to be the left rear up switch not adjusted correctly but close enough that if you tested it it would mega as a closed switch. Only in flight would the switch not close and only occasionally. Hope this helps anyone with similar problem in the future. |
#4
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Quote:
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Herb R Harney 1968 337C Flying the same Skymaster for 47 years |
#5
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Possible explanation - squirt your uplocks
It has been decades, but....
The doors will not close until all the uplock micro switches are all closed (wired in series), which also turns the UPLOCK light ON. This makes sure everything cycles in sequence correctly and prevents doors from closing while gear still in transit (or not all the way up). As I recall, that uplock light circuit also allows the system to pressurize to 1200-1500 PSI. When it hits that pressure limit it pops the gear handle down. The handle goes down, the system at rest, and all is well in the land.... In your case the the gear comes up, the uplocks close UNDER PRESSURE (but not solidly!!!), the microswitches are closed (under UP CYCLE pressure) the uplock light comes on (briefly), your doors close, then the light goes off but the down handle never occurs. I would bet a nice doughnut against a dollar your uplocks not solidly going 'CLICK' So under UP-CYCLE pressure they the uplocks in position CAN AND DO close the microswitches, but wont keep the switches closed without the UP CYCLE pressure. So the final pressurization needed to pop the handle never occurs. ------- ANSWER #1: Check /squirt get to know your uplocks. ANSWER #2: If the system cannot hit the 1200-1500 PSI to shut off, it wont lock the system UP correctly. Yes, a leak or air will do this. ON THE GROUND, try cycling the gear DOWN CYCLE position. If system can hold pressure it will pop the gear handle 'up' from DOWN-CYCLE to the DOWN LOCKED position. No leaks. The system is 'self-burping' so a bunch of cycles will burp out the air. I will accept any decent chocolate-covered doughnut as reward. EXTRA CREDIT I have replaced those little beasts with tiny screw in 24 volts LEDs Nice, cool, will never burn out (again). D
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David Wartofsky Potomac Airfield 10300 Glen Way Fort Washington, MD 20744 |
#6
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So, having flown only the "G," what model did the gear handle stop reacting to system sequencing? The "G" is easy, up/down, nothing moving or in-between.
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#7
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Quote:
When Cessna built the G (1973) model it was changed to an electric motor to operate the hydraulic pump, therefore now the gear handle is just a mouse click
__________________
Herb R Harney 1968 337C Flying the same Skymaster for 47 years |