November 21, 2009 Landing Gear Emergency in the Twin Comanche

This flight ended with a nice landing, but only after Patuxent approach declared an emergency. More on that in a moment.

I have been flying my Twin Comanche - N833DF - since I brought it home from Tulsa in mid September. I have seen a bit of down time working with my mechanic to replace fuel bladders, repair fuel bowls, inspect the landing gear, and generally have a look around. The avionics six pack was dated and the performance suspect, so it made sense to do that next.

I contacted several avionics shops, and Penn Avionics had the most creative idea for what to do with the panel. I took it up there and had them install the Aspen EFD1000 PFD; overhaul the AI and use it to replace the Turn and Bank; put the 396 in the panel, and generally make everything talk to everything else.

After more than two weeks of down time for this project, I was a bit rusty just flying the twin, but ready to try out the new tools. I took friday off and Mike B did too. Mike met me at 33N in a C172 to gave me a ride up to OQN where the work was done. Paperwork was a bit delayed, so my idea to test in the area didn't pan out. I ended up flying the airplane to Georgetown on my own, with Mike following behind.

The Flight:

I taxiied to runway 9 for departure, only to find the push to talk on the pilot side was defective. Not a good start. Taxi back to the shop for a few minutes, and I'm back for the second runup. This time I depart for MXE to stay under Philly's class bravo. Clouds are forcing me higher, as I'm VFR, so I climb and decide to try out the autopilot.

Life gets interesting at this point. The airplane begins the most aggressive wing rocking I've seen. The heading mode is tracking the CDI like a mouse on crack. I disconnect and try again in GPSS mode. Same deal. I'm getting a headache by this point, but decide to press on. The clouds are pushing me up. Mike and I are talking on 123.45. I recommend climbing to 4.5, and Mike reminds me we are still under the Class Bravo shelf. This is why I wanted him along in case things got 'interesting' and my distractions mounted. I delayed my climb until out from under Bravo, and then went higher above the scatter layer.

I need to get the airplane back home and will schedule a separate day for testing later. At least today I can do manual approaches and ensure the Aspen is working as advertised and fully functional.

Mike and I meet in GED for lunch. The plan is now to grab something to eat, and then go do a number of approaches. We depart for SBY to do a localizer 32. The Aspen is working great, and the airplane is only slightly ahead of me. Cleared for the localizer, the GPSS roll steering isn't functional so I manually enter the hold. Inbound to the localizer I have the airplane properly slowed and I drop the gear. Checking the mirror to watch the nose gear come down, all looks normal. My hand remains on the gear switch until I see the nose gear down and locked. That done, I bring my eyes to my right hand to check the down and locked light, but I see only darkness.

This is a first for me. The Twin Comanches are known for gear problems, but I know my gear is in good shape and I also know the gear sounded and felt normal coming down. Still - no light. I am still IFR, and at this point have been talking to Salisbury tower. I discontinue my descent, and at the missed approach point start on the published missed. I notify the tower that I have a gear problem and intend to enter the hold to diagnose.  In retrospect, I probably turned too early for the missed approach, and should have coordinated more with the tower and ATC.

In the hold, ATC asks me if I'd like to cancel. I decline and ask for lower. They tell me sure, but you'll need to be VFR to do that. Did I want to cancel?  There are scattered clouds about in somewhat of a layer, and I don't have time to remain clear and troubleshoot. I start Mike on reading the manual gear extension process in case we need it. 

Approach calls and asks my intentions again, indicating I should cancel IFR. I remember telling them definitively that I would remain in the hold until we diagnose the issue further, that I had four hours of fuel, and that I'd let them know my intentions when I knew.

Three trips around the hold gave Mike and I plenty of time to understand the manual gear extension problem, swap light fixtures, reviewing checklists, and cycle the gear. On the last circuit, I slowed the airplane intentionally to 100 mph or so with the gear up. At that point a big red light came on (I would swear in court that it was 5" wide, but its only 1/2"). That light is a gear not down warning, which occurs when the power gets low enough that the gear should be down, but isn't. Since that came on with the gear up, I put the gear down and it went out. I suspect it works through the same switch, so that is proof of sorts that the circuit is indicating down and locked.

I make a decision and tell Patuxent that I would like to fly the localizer 32 to a fly-by low approach. I would like someone on the field to visually check gear down, but I will absolutely not land at SBY. Approach declared an emergency for me at this point, and I inform then I'll be heading to GED next.

Light is still out on the low approach, but a crew at the runway verifies gear appears down. I select gear up, and get myself queried several times from the tower. They were incredulous that I brought it back up, but they didn't have all the information I had. The jury is still out though, someone might read this and tell me what an idiot I was, though my decisions still look ok to me, in retrospect.

Back with PXT, we are cleared to GED direct. There were some scattered clouds about, but nothing material. I told approach I was convinced the gear was good, and this was an electrical issue with the lights. They kept the emergency in play though, and notified Georgetown that they had an emergency in progress. I appreciated what they were doing, and they were professional.

Back at Georgetown I asked Bump to come out to the runway for another fly-by. He does; I do; no light; I think we are good. Mike agrees. This time we keep the gear down and fly the pattern to a rather nice landing. I used only 10 degrees of flaps this time, and kissed it on. Off the runway, we shut down to inspect the gear locks, and they visually checked out.  Still no gear lights.

Bump called Dover and cancelled the emergency. Mike and I taxiied to the hangar and put it away....

Results of continued investigation:
  1. International Comanche Society (ICS) website is awesome. Several responses from members pointed me right to the person who built the lights. All this on very little information, and a picture of the lights I posted.
  2. Several other ICS members followed up personally to tell me what they know, and to offer assistance.
  3. The manufacturer of the lights sent me schematics, documentation, and exchanged emails multiple times answering my specific questions.
  4. The gear lights are MilSpec lights that actually have little metal shutters inside them. They completed and absolutely block out all light when twisted clockwise. How the hell would I have guessed that? I must have twisted the dimmer on during the flight to ensure they were all the way in. After I learned this, I went to the airplane and can now see the shutters. The gear light was fine, but the amber gear up light had burned out when I moved it. 
  5. When you screw in a replacement light - you do so clockwise. The shutters are closed by default, so you won't see any light when you do that.
  6. These lights could certainly have been part of an accident chain, until I learned what I know now.
All is well now. I flew it home yesterday, 11-21-2009, and all is well.
Frank E. Dorrin Jr
11-21-2009