ALERT: Gear-up light comes on with doors open!

[Ernie Martin]

Yep, you read that right. Happened Sunday in what could have been a tragic accident.

Took off in my 1973 337G out of Miami, headed over open waters to the Bahamas. All looked well, but after a while it seemed as if the climb was more sluggish than usual. I had a full load and wondered if I had miscalculated it and was overloaded. I looked around, engines looked good (manifold pressure, RPM, fuel flow, EGT), yellow gear-up light was on. Nothing seemed amiss. Could the props be losing "bite"? Am I indeed overloaded?

We reached cruise altitude, configured aircraft (cowl flaps, RPM) and when airspeed settled I noticed I was about 25 MPH slower than usual, doing 125 instead of 150. Looked again at everything, found nothing, and was now considering turning back -- remember I'm over open waters, nowhere to land in an emergency.

That's when I looked out to the small convex mirror I have under the left wing, pointed slightly backwards so I can see the rear engine (born of my concern about a possible engine fire back there). The smaller, longish main gear door under the cabin was partially open and -- worse -- the larger, parachute-like door behind the cabin were mostly or completely open.

In my aircraft it's not an engine driven hydraulic pump that operates the gear but an electric power-pack, and the circuit breaker had popped after the gear had stowed but before the doors had closed. The troublesome point is that the design turns the gear-up light on when the gear -- not the doors -- are locked.

Had I lost an engine, it's doubtful I would have been able to maintain altitude with the doors open. Please be alert to this. In my case I simply reset the circuit breaker and the doors closed without a hitch. Gear function was normal on landing and yesterday on both take-off and landing.

Ernie

[hharney]

Ernie
Check the circuit breaker, could be weak. Power pack motor may be compromising the symptom too. Circuit breaker is cheaper to try first.

We found on one system that the accumulater pressure was weak. Would cause electrical load and trip out systems. Find it under the floor in the center.

[Ernie Martin]

Thanks, Herb. I know what the problem is: low battery. I hadn't flown in almost a month, engine barely started. It has happened before, and I normally wait 5 or 10 minutes into the climb before retraction when I know the battery is low, to give it a chance to charge. This time I plain forgot.

But the key point in my message is NOT why doors didn't close. It's that the gear-up light can come on -- giving you a false sense that all is well -- and leave you flying with the doors wide open.

Ernie

[edasmus]

Thanks for the info Erinie. I'm glad everything turned out well for you. Chalk it up to a learning experience. I am certainly filing this one into my memory bank as I fly my own plane (which as I am sure you know, is identical to yours).

Ed )

[hharney]

I don't know if the battery would be the cause of that or not. I sounds to me like there could be other areas of the system that warrant inspection. Battery's are something we all take for granted. If it starts it must be good but what happens if the alternator system goes blink? How long is your battery going to last to get you back to the ground? Something that I have thought a lot more about and especially after reading the article from the link below. A simple battery minder will help to extend the life of a battery especially if it gets low use. It has caused me to reconsider my complacency about batteries.

http://www.avweb.com/news/features/K...g221073-1.html

[Ernie Martin]

I "recondition" the battery every 6 - 9 months by adding distilled water and trickle charging at a constant 28.4 Volts. For the first 2 - 3 months after that, the gear breaker never pops. It also never pops if the aircraft is used regularly, even if reconditioning hasn't been done for a while. And it never pops at the end of a flight. In short, it pops only on retraction on the first flight after the aircraft has been unused for weeks and if the battery has not had reconditioning for a while. So, yes, I think it's the battery.

Ernie

[edasmus]

For Christmas I just received two "smart" aviation battery minders designed specifically for the the Gill batteries I use (12 volt in a PA24 Comanche that I also fly and 24 volt for my C337). I purchased them from batteryminders.com, MODEL: BatteryMINDer 24041-AA-S2 for our C337's using Gill batteries. They have other models specifically for the battery you use so read the fine print if using Concord or other sealed batteries. One should be able to find what they need for whatever battery they prefer to use. These units are designed to charge and then maintain the battery and should be left on continuously when not flying the aircraft. They contain a microprocessor and provide the battery with exactly what it needs to stay properly charged (this is the claim anyway). The units were $200 and if they double the life of the battery (which sounds likely), they would pay for themselves easily. More importantly however is flying with the confidence that the battery is as it should be and starting performance would be top notch.

I hope they work as advertised. Mike Busch speaks high of these units as well if any of you folks agree with what he preaches.

Good Luck,

Ed

[Ernie Martin]

Thanks, Ed, but I tie down on the ramp, far from any outlet.

Ernie

[edasmus]

The batteryMINDer folks do not permit these units being exposed to the elements however it's probably less than 10 minutes to remove battery and take it home and then reinstall on preflight. An inconvenience for sure but not completely out of the question especially if you know the airplane is likely to sit idle for a month.

Just a thought.

Ed

[louis@52f]

Ernie
I had a similar problem on my '69 T337 some years back. I have these comments relating to this;
1. On my a/c, the gear up light indicates only that the up position switches, which are in series, are all closed. The position of the doors is not part of that circuit, so with certain failures, the doors could be open in either the up and locked or down and locked condition. The gear position light SHOULD reflect the door are closed, but not with a failure of various types.
2. I'm no electrical engineer, but I can't imagine a weak battery is the source of your problem. If the charging system can not charge the battery and supply full aircraft electric load, thus allowing the system voltage to drop too low, this might lead to your gear door problem. However, then you have in my opinion a bigger problem, weak charging system and weak battery, not a good combination.
3. I found my problem was a high resistance in a wire terminal on one of the up position switches. The up light would come on, but the current was not enough to keep the door solenoid closed. (Engine driven hydraulic pumps, but I think the door control on yours is similar.) The gear would come up and lock, doors would close, then open, maybe close again, but then open and stay open. I replaced all the wire terminals in the gear position indicator circuits, never had another similar problem.

Lou

[Jim Smith]

I've had gear door problems occur on both my D and F models. Because of the somewhat unreliable operation of this type of system (similar to the 210), I've made it a habit (part of my unofficial checklist) to confirm in my convex mirrors the gear has fully retracted and doors closed after raising the gear handle. Also (only applicable on pre-73 models), I keep my hand on the gear handle until it drops into the neutral detent and I know it's completed its cycle. There's been a few times the gear handle stayed up and the pump kept running and didn't realize it until I could smell the pump starting to overheat.