South Burlington, VT
- Aircraft Year
- 1978 580
- Aircraft Type
- Super Commander
- Reg Number
- N555LP
- Serial Number
- 14405
Hi All,
Happy new year!
I have encountered yet another 112 (pre s/n 381) with a nose gear indicator falsely reporting down and locked. This stems from the fact that the actuator-mounted switch and locking pin style actuator are complicated, old, and difficult to service, to the point that an ordinary maintenance shop is unlikely to even figure out how the system is supposed to function, let alone get it adjusted correctly.
On the 112 at hand, the nose light reported down-and-locked with the gear only about half way down. This occurs as the brace limit switch loses contact and hands off cycle completion to the actuator-mounted switch (which in this case was ALWAYS reporting complete).
There is a simple test I would strongly recommend that all of you do on your 112 (and "112A") airplanes s/n 1 thru 380:
Jack the plane securely. Raise the gear. Have an assistant select gear down while you lay on your creeper in front of the airplane with your foot ready to press against the nose tire as the gear comes down. Make sure your creeper is free to roll away from the airplane. The hydraulics should push your foot, and you, ALL THE WAY DOWN. If you stop getting pushed before the gear is all the way down, you have trouble in system. It is also informative to have your assistant call out when he first sees the nose indicator go green so you can tell how big a liar the indicator is.
Some of you will be horrified by what you find out!
This test can also be used for the mains altho more difficult to arrange yourself, and creeper... be careful.
The actuator locking pins have long since become ineffective on most 112's. Even if they still do "lock", they can likely be overcome and knocked out of the lock by even the most minor of shock loads on the gear during taxi or landing. For this reason, it is imperative that your system be adjusted properly to start the pump IMMEDIATELY if the gear comes out of lock, before the drag brace has a chance to go under-center, and the gear collapse. Down pressure is not maintained in the s/n 1 thru 380 system, and falls off to nil within a minute after the pump shuts off. The gear springs do help keep the gear down, but should not be your only line of defense.
I am working on a system upgrade that adds a down pressure switch and down-check valve to airplanes in this serial range. 2nd installation happening now, will keep you all informed.
Jim
Happy new year!
I have encountered yet another 112 (pre s/n 381) with a nose gear indicator falsely reporting down and locked. This stems from the fact that the actuator-mounted switch and locking pin style actuator are complicated, old, and difficult to service, to the point that an ordinary maintenance shop is unlikely to even figure out how the system is supposed to function, let alone get it adjusted correctly.
On the 112 at hand, the nose light reported down-and-locked with the gear only about half way down. This occurs as the brace limit switch loses contact and hands off cycle completion to the actuator-mounted switch (which in this case was ALWAYS reporting complete).
There is a simple test I would strongly recommend that all of you do on your 112 (and "112A") airplanes s/n 1 thru 380:
Jack the plane securely. Raise the gear. Have an assistant select gear down while you lay on your creeper in front of the airplane with your foot ready to press against the nose tire as the gear comes down. Make sure your creeper is free to roll away from the airplane. The hydraulics should push your foot, and you, ALL THE WAY DOWN. If you stop getting pushed before the gear is all the way down, you have trouble in system. It is also informative to have your assistant call out when he first sees the nose indicator go green so you can tell how big a liar the indicator is.
Some of you will be horrified by what you find out!
This test can also be used for the mains altho more difficult to arrange yourself, and creeper... be careful.
The actuator locking pins have long since become ineffective on most 112's. Even if they still do "lock", they can likely be overcome and knocked out of the lock by even the most minor of shock loads on the gear during taxi or landing. For this reason, it is imperative that your system be adjusted properly to start the pump IMMEDIATELY if the gear comes out of lock, before the drag brace has a chance to go under-center, and the gear collapse. Down pressure is not maintained in the s/n 1 thru 380 system, and falls off to nil within a minute after the pump shuts off. The gear springs do help keep the gear down, but should not be your only line of defense.
I am working on a system upgrade that adds a down pressure switch and down-check valve to airplanes in this serial range. 2nd installation happening now, will keep you all informed.
Jim
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