Bad Alternator. Marooned in Bahamas.

[GJ Humphrey]

Hi Fellow 337 Fans,

I'm marooned at Marsh Harbor in the Bahamas with an inoperative front alternator. I had a replacement flown in by FedEx but it turned out to be a 60 amp model, where I need a 38 amp model.

Does anyone know where I can quickly get a new or rebuilt 38 amp alternator for my 73 Cessna T337G, Serial Number P3370076?

GJ Humphrey

[skymaster]

fly on one. is it spinning . did coupler shear? JCH

[GJ Humphrey]

Yes, the coupling sheared.

I don't want to fly on the rear alternator and take the chance that the front alternator gear, which is somewhat less well supported when no longer connected to the alternator, might start clashing with the engine gear. By an ironic coincidence, there is a local 337 here whose owner today told me that happened to his engine and it cost him $18,000.

In an emergency, I might fly with one, but this isn't an emergency.

[Jerry De Santis]

Gordon, I flew many times with only one alternator, no problem. Are you sure it is the alternator and not either the rubber coupling or the woodruff key. I had my front alternator stop working and it turned out to be only the key.

With engine off, (Can you tell I'm an engineer), remove the cowl and Reach in with your fingers and see if you can rotate the alternator. If you can, it is not the alternator, it is either the key or the coupling.

BTW, I had my exhaust that feeds into the turbo welded. Now I hold MP on the way up. Have you solved your MP problem yet?

Good Luck
Jerry

[kevin]

Gordon,

I do not claim expertise here, but I think you might be right to be concerned about flying it. I had my rear alternator fail this way while on the road (shaft sheared) and the mechanic who fixed it scared the crap out of me by telling me that if he could not find all the pieces of the (something, gear, shaft, not sure), we would have to tear down the engine. (This was in my '65 337).

Luckily, he found all the pieces in the oil pan, and there was no other damage.

It seems to me that flying it might entail the risk you described.

The failure happened to me while in flight 100 miles north of Wichita, so I took the airplane back to its birthplace to be repaired by the FBO there, the name escapes me at the moment. They got an alternator from Cessna in a couple of hours. It was not cheap by any means, but it was fast.

Kevin

[GJ Humphrey]

Thanks, all, for replying.

In reply to Jerry, the alternator was in fact seized and the Lord coupler gave way, sparing the shaft from shearing and the potential of metal fragments navigating around inside the engine. Believe it or not, that alternator just came back from repair under warranty and was re-installed just before my son and I left NH for the Bahamas. What kind of repair they did, I can't imagine. Obviously, the bearing was getting ready to go when it left the shop. The alternator light came on steady while we we out over the ocean (where else?)between Fort Pierce and Freeport.

Re my separate problem with fluctuating manifold pressure when RPM is pulled back below 2500, no the problem has not been solved. My mechanic has searched high and low for leaks and swears there are none. I believe him. And he has examined the waste gate controller and waste gate for proper operation.

I think I gained some insights into the problem on this trip to the Bahamas, however. As we flew south and air temperature and humidity rose the oil cooler became less efficient and oil temperature rose, while oil pressure fell. The rear engine oil temparture climbed to around 210 and pressure fell to 47. I had to open cowl flaps partly and run richer than normal to control the situation.

How do I know the oil pressure was 47psi? Obviously, I wasn't getting that info from the crummy Cessna instrument. No, I just had two Electronics International UBG16 engine analyzers installed, that show, in addition to EGT and CHT, oil temp, oil pressure, volts and amps. Wow, it's great to know what's really going on in the engine compartments. I love these analyzers.

I recall my mechanic said the maintenace manual states that a minimum oil pressure of 51 psi is required for proper operation of the waste gate controller. So it may be my problem is one of oil temp and pressure. I've been running 15w50 oil, but I'm having that changed down here to 50w non-synthetic. If the test flight shows oil pressure still low, the mechanic is going to adjust the oil pumps to increase pressure. I hope one or both of these measures wil solve my problem with MP. It would be great to fly home to NH from Ft. Pierce at FL 200 and catch some tailwinds for a change, with a stop in VA or MD, depending on the winds.

Another altnernator is on the way, arriving probably in three days. This time it's 38 amps.

Meantime, I'm still marooned in the Bahamas, missing all that snow and ice at home. Sigh.

Best,

Gordon

[skymaster]

at alts above approx 12k . My 73 p requires mucho rpm to eliminate the described bootstapping . it would be interesting if the oil pump can be tweeked to mimic the rpm and allow lower rpm setting at alt. it would save fuel too. JCH

[GJ Humphrey]

I'll let everyone know the result of my oil eperiment.

I've spent an awful lot of time and money on this manifold pressure problem. I'm hoping higher oil pressue is the answer, at last. Having the manifold pressue surge by a couple of inches whenever I try to reduce RPM below 2500 is simply unacceptable. There is something wrong somewhere,and it isn't induction leaks, in my case.

It might seem picky to want to cruise at 2350 instead of 2500. But 2350 reduces the noise level a lot. And the power setting chart in the POH indicates that the T337G should be able to cruise at 20,000 feet at 2300 RPM. I'd settle for 2350 at 180.

[Ernie Martin]

The local 337 in Marsh, did it belong to Bob Cook? Haven't heard from him in a while. Hope he's well and re-joins our banter.

Ernie

[GJ Humphrey]

I met the gentleman only briefly in the hallway of the FBO. He was about to get into his 337 for the first ime in awhile, because of cataract surgey. I'm embarassed to say, I don't remember the man's name.

I looked up Bob Cook in the Skymaster Forum. He lists his airplane as a P337, but the 337 in Marsh Harbor is not a P. I'll have a look at the registration number on that airplane when I go to the airport tomorrow.

My alternator is supposed to arrive in the AM.

Gordon