Main Gear not over center

[greg]

When the gear is extended on my 1960 Comanche single the left main fully extends so it is slightly past center but the right main is stoping a few degrees short of being fully extended. In other words it not going past center like it should. It is just shy of being straight down and not someting that is noticed with a casual observation. This was just noticed yesterday by one of my partners after he put it in the hanger after flying. I believe this is a realitively new problem but it probably been this way for at least several takeoffs and landings because the outside of the right tire is starting to showi slightly more wear than the rest of the tire.

No blown circuit breakers, gear motor seems to be operating properly and the emergency extension arm appears to be full forward. I opened the inspection plate and visually checked the bungee and bungee arm and did not see any problem. Bungee cord is about 18 months old, no sign of wear and the arm appears to be in good shape.

My guess, and that's all it is, a guess, is the gear extension conduit is not pushing the gear all the way down. I have read that the conduits can get bound up with old grease and dirt. Does this sound likely cause or could it be something else? Second question is, if the conduit is the culprit, is it safe to ferry the plane to my mechanic (5 miles) if I leave everything connected and leave the gear down? My thought is that with gear conduit extended as far as it is, it should hold the gear in place as long as it is connected to the motor, but, my understanding of how the gear operates may not be correct.

[Kristin Winter]

It is hard for me to tell whether your gear is about to collapse or whether the lower drag link is just adjusted too short. The question is whether the drag links are going over center, not whether the gear is vertical. I would not fly the plane until you have someone who knows what they are doing, look at it.

[9089P]

I'd ask the mechanic to make the 5 mile drive to put eyes on it.

Don

[Ray B]

Take Kristin's advise. Do not fly it (or move it) until someone who knows Comanche gear checks out the problem. Many years ago I stopped a pilot on the taxi way at Bracket Field when I noticed the problem you describe on the left main. I could not persuade him from flying back to Chino, his home base, before having the gear looked at. It collapsed on Chino's taxi way when making it's second right hand turn after landing. Something's wrong! I know you love that old girl, so please, have it fixed before we read about another good Comanche up for parts sales. Ray B

[greg]

Thanks for the responses. I am planning to have my mechanic look at it before I even put a tow bar on it to pull it out of the hanger. I probably should have phrased my question, "if the mechanic finds the push pull conduit is the problem because it is not extending fully, should it be strong enough to hold the gear in place if I need to take it back to the mechanics shop".

I was also looking for other potential causes and I had not thought about the lower drag link being out of adjustment. Anyone else have an idea what the cause could be?

Thanks
Greg

[N3322G]

Greg, ditto all the previous posts - especially Kristin's.

A new conduit held our twin up for 36 landings before it collapsed. The newly installed micro-switches, done in Kansas, were adjusted to give a false gear down green light, safe to land, indication. We now trust-but-verify any gear work done on the Twin.

[N3322G]

Greg,

You might also consider investing in the Maurice Taylor DVDs http://www.comancheflyer.com/NS/cff_merchandise.php - scroll down to the last item and #3 would be of interest to you. I watch these every year or so as a refresher - usually about the time we do a BFR - nice reminder to keep your knowledge up to speed.

[md11flyer]

Greg:
NO the conduit will not hold it if the side brace is not over center. My guess, ( and this guess assumes that your micro switch is out of adjustment as well) and Its only my guess is that the conduit is already bent and once it has a bend in it it doesn't take much to bend further. If its not the conduit and its another part of the gear for example the infamous side gear brace stud that is cracked and ready to fail or a number of bushing that are worn out, you have to get the plane up on jacks and inspect it before moving it.
What has me scratching my head on this is how did you get a green light without the side brace going over center like you said...(bad micro switch settings?).. or did the side brace go over center and the fact that the other gear components are so loose that even with the side brace going over center the gear can go back over the vertical position because of the play in the gear.
In any case jacking the aircarft up and inspecting it before flight would be a prudent thing to do.
Good luck,
Gary

[Kristin Winter]

Greg,

>>"if the mechanic finds the push pull conduit is the problem because it is not extending fully, should it be strong enough to hold the gear in place if I need to take it back to the mechanics shop?<<

Absolutely not! If the push pull conduit is not extending fully, you have no down lock. If the gear doesn't fold up taxiing out, it probably will on landing. You may very well have something majorly wrong. I would say that you are lucky that it has not already collapsed.

Personally, as you are in Texas, I would hire Clifton Aero to come to your location and look over the gear, assuming your mechanic is not a Comanche guru.

[N3322G]

Greg,

Let me clarify - if this were my aircraft, I would put some jacks under it now. If I had to go buy jacks, I would do that and not move the aircraft. I would not so much as stand on the wing to get in the cockpit.

[bernard nowlen]

Mega Dittos Greg. Hope he has good insurance. A set of jacks and tail stand are about $800 new from the "jack house". That's a lot cheaper than 2 engines/props/total airframe/etc. I just did the 1000 hrs gear ad and my plane has 3k ttaf and no log entries of the 1000hr gear ad ever being done other than bungee cord replacements.That says alot about 45 years of incompetent annual inspections. We replaced about $1500 of bushings and other parts to get it right and rigged correctly.
live and learn. Bernie

[greg]

Thanks everyone. I appreciate the responses and concern. Like I said, I have no intention of even putting a towbar on it until it is inspected. Mechanic is coming out tomorrow afternoon with jacks and tail stand so hopefully I'll have some answered by tomorrow evening.

[Kristin Winter]

Greg,

If you would like to shoot me a picture of the drag link mechanism as it sits now, I will see what I can see. If your mechanic is scratching his head, or you think he might be, shoot me an email at kristin_winter at comcast dot net and I will give you my phone number. You can also get my number from the Pathfinder on the ICS main website. I would hate to lose another airframe and am happy to talk to you and your mechanic if you have trouble diagnosing the situation of deciding how best to solve the problem.

[greg]

Thanks Kristin.
Email sent, actually 2 emails, I forgot to attach the photos in the first one.

Greg

[greg]

After a thorough inspection of the landing gear, both on and off jacks, by my mechanic and consultation with Kristin by email and phone, (thanks again Kristin) it was detemined the drag link mechanism was locked in place, no bolts, studs, arms were broken or cracked, bungees were in good condition and the push pull conduit was extended properly. There was some wear in a rod end and a couple other things that will need to be addressed but nothining that appeared to put the gear in imminent danger of collapsing. It was decided it would be safe to ferry the Comanche to my mechanics shop where she now sits ready for not only a complete gear inspection but also we have just a few a hours left before the horn AD would be due so we will also be taking care of that at the same time.

Thanks for all the advise, tips, opinions and concern.