Emergency Gear Extension

[Richard Lanning]

Recently my gear did not come up. Switch up and nothing. Green light stayed on. Far as I could tell the motor wasn't running.

After leveling off, reattempted to retract the gear and it came right up. Now I had 90 minutes to wonder if it would actually come down. Fortunately, it did with no issue. The plane is in annual now so the gear system will get a good lookover. I suspect one of the pressure switches still thought the plane was on the ground. Hope that is all it is.

Anyway, I was talking to my mechanic about it and he said one of his prior Comanche owners indicated that on an emergency gear down landing you have to hold the lever forward on landing to make sure the gear doesn't collapse due to vibration.

I don't ever recall seeing or hearing anyone discuss that as part of the emergency gear extension procedure. I have the Comanche DVD now and it made no mentionn of this. Once the gear goes into the overlock position I would think you would be fine. I don't like the idea of having to have one hand tied up holding the gear lever forward.

Any thoughts on this?

[Zach Grant L1011jock]

If the gear is rigged properly, there is no need to hold the handle forward. If the gear is not rigged correctly, you may be able to hold it over center with the handle, but if it does come under center, you will be crawling abay from the gear up scene with a broken foot/leg/arm. The gear does lose an additional bracing element when the transmission is disengaged, however there shouldnt be significant stress on the transmission if everything is set up correctly in the first place. The strength of the gear is in the overcenter position of all of the drag links. The main gear has down lock assist springs but they are secondary to the preload of the push pull cables. The gear is fully interconnected between all three gear legs, and the nose gear should snap overcenter last, giving the main gear the preload it needs. If you can lay on your back and push up on the main gear drag links, with the gear down, and they move, your gear needs to be rerigged as there is insufficient preload there to keep the gear drag link overcenter, and then you are at the mercy of the spring (and that spring is probably very overdue for changing in most airplanes). If any gear leg bounces under center, game over, they are all going to come up as they others will be actuated the same as if the motor was pulling them up. Bungees dont have anything to do with keeping the gear down and overcenter, the springs do. The bungees simply counterballance the loads of the gear and assist the transmission and motor when putting the gear up, and assist in countering the force of the slipstream when the gear is almost fully extended to make sure it goes overcenter either electrically or manually.

Zach