Sunday, March 31, 2013

Emergency Gear Extensions

My most recent flight in the Arrow was described as "quite efficient" by my CFI. 0.5 hours on the hobbs. We went up to practice emergency gear extension and troubleshooting and we got a bit more than we bargained for. 

We talked about the various ways the gear can fail, how to troubleshoot and how to resolve the different gear failures. We then went up to put the theory into practice. Instead of heading out to the usual practice area we turned towards Mt. Lick as soon as we gained altitude to a different practice area. It is a long shallow valley just on the other side of the hills from Reid-Hillview.

Once there he took the controls and demonstrated the maneuvers you can do to "help" the gear get down and locked when it doesn't lock. Then I got to do it. It was fun. Then I slowed the plane to 100MPH and he had me put the gear down. I knew what was coming, I knew the gear would fail to come down for some reason. I suspected a circuit breaker was pulled en-route to the practice area perhaps. No matter. I knew what to expect and it was as expected. The gear did not come down at all. No sound of the wind changing, no "Gear Transit Light", no kick and clunk as the gear locked down and no three greens. So I cycled the gear and tried again. Nope. OK, time to use the emergency gear extension lever. When held down is allows the gear to free fall and lock into place. You slow to 100MPH to do this so there is less wind resistance on the nose gear fighting gravity on the free fall.

I pushed the gear extension lever down and heard the air flow around the plane change. I felt the two main gears lock into place but didn't feel the third, harder kick of the nose gear locking down. The gear down lights for the left and right mains came on but not the nose. Hmm. That was strange. Fly the airplane. Two greens, no nose gear. We tried switching the bulbs between the gear lights. It was possible the nose gear light was bad (not the gear). I doubted that. I didn't feel the gear kick down. Sure enough, it wasn't the light bulb. Here we were practicing gear failures and all of the sudden we had potential for a real one.

My CFI undid whatever he did to the gear to cause it to "fail" in extending and the nose gear kicked into place. Three greens. So, the gear extended with the help of hydraulics but not in the free fall mode. That's not good. If we had actually lost hydraulics or electric we wouldn't be able to get the nose gear down in this situation.

We were both intrigued, was this a one time thing or a real issue? We tried it again. He failed the gear extension system (I'm pretty sure its the circuit breaker.) And I slowed the plane down and pushed down on the lever again. The two mains locked down. The nose gear did not. Turn on the hydraulics and the nose gear locked into place.  Third time's the charm. We did it again, this time he held down the lever. Two greens.

We talked briefly as I retracted the gear again. Do we go on with the rest of the flight as planned? Or abort and get the gear checked out sooner than later? As far as I could guess, this could be a sign that the front landing gear system was weak and about to fail even with hydraulic assistance. I suggested we head back and get this checked out. We had no problem with the gear operating on the approach. Of course this time we had the hydraulics on!

We landed the plane and told the A&P about the issue. He immediately took it to the hangar and jacked it up to swing the gear. The mechanics repeated the same sequence we did and the first time the nose gear locked into place, slowly. That was with no wind. He retracted the gear and this time put just a little bit of pressure against nose gear as it came down in "free fall". All it took was a fingertip of pressure and the nose gear wouldn't lock into place. The mechanic pulled on the spring attached to the nose gear that is supposed to assist with locking the gear in and the spring was very flexible. Too flexible. He decided to replace the spring.

We will find out in our next flight if the spring really did the trick or not.

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