never had this happen before

[94973]

yesterday, I was propping the tcraft, and I got an unexpected ignition.
It was about 27 degrees out, and I had pre heated for about 45 min with a "red devil" lp heater. with the plane tied down and the wheels chocked, I was pulling the prop through with switches OFF, when I got 6-8 blades of rotation and all the sounds of combustion. the mags are grouded, because i was able to shut the engine down after a subsequent flight by switching them off.

Can the C 65 diesel because of pre-heating? Is there some way the mags could have been temporarily shorted?

I'm glad my old instructor at 40I taught me to treat every prop as if it's hot, every time. I had actually considered (and rejected) the idea of pulling through still in the hanger, to avoid standing in the wind another 2-3 min.

[flyguy]

Re: never had this happen before

Open connection at the mag switch due to the cold (metal shrinks)? It is pretty hard to get a low compression engine to diesel even when really hot. At least I have never seen it. I would check the lead attach screws on the switch carefully; I've had some weird stuff happen there. Also the lead contacts in the mags. You mentioned shorts. I assume that was just a mis-thought as what you are looking for is an open. Don't be insulted if I point out that mag leads are shorted to disable the mags and open to fire.
Darryl

[Frank DeBartolo]

Re: never had this happen before

Great reason for tieing down the tail before propping if propping alone.

FD
N43684

[AndyDuke]

Re: never had this happen before

Happened to me once as well. I checked the mags and found one of the earthing leads had come adrift. I always prop from behind now.

[jrzangger]

Re: never had this happen before

During my last annual, the IA checked the mag switch and found it would open if moved very slightly out of the detent. (This is the original old style Bendix switch) After disassembly of the switch and cleaning the contacts, it worked well again. Fortunately, I did not get a "hot" engine with this, but it was about to happen! I had always shut the engine down successfully with the mag switch so was lulled into the belief that the switch was good.

[Frank DeBartolo]

Re: never had this happen before

Isn't there an AD on the Bendix switch that has to be complied with every 100 hours? As I understand it the way to comply with the AD is at engine shut down to hold the switch in the off position (in my switch to the left) and hold it all the way left to the stop til the engine shuts down. Anyone want to comment?

FD
N43684

[Two Ten Aero]

Re: never had this happen before

The AD exists, and is probably one of the most overlooked AD's ever printed.
This whole experience is why we teach from the first walk around to treat the prop like a loaded shotgun.

I was pulling a 985 through early one morning, and it fired. I was laying under a DC-4 I had just landed at FBK, waiting for a ride, number three turned over about two revolutions.

The AD is as explained. You can comply with it quite often without being an A+P or signing it off. When we are flying something that needs proped, it is a very good idea to know the mag switch is working properly.

[mhorowit]

Re: never had this happen before

Isn't there an AD on the Bendix switch that has to be complied with every 100 hours? As I understand it the way to comply with the AD is at engine shut down to hold the switch in the off position (in my switch to the left) and hold it all the way left to the stop til the engine shuts down. Anyone want to comment?

FD
N43684

Frank - isn't that what we do everytime we shut down the engine? - Mike

[Frank DeBartolo]

Re: never had this happen before

Frank
N43684

[alwaysoar]

Re: never had this happen before

Slick has a good deal on new mags, dual impulse, STC'd to replace Bendix, Eisemans, and obsolete Slicks. They'll take the olds ones and send a $150.00 rebate. Net cost about $1050.00--I think Jason put me on to it. Why mess with old junk--we're already dealing with 60-year-old airplanes.

Ed@BTV VT
TF 527

[Frank DeBartolo]

Re: never had this happen before

Frank
N43684

[Robert Lees]

Re: never had this happen before

Eisemans

Lovely mags...I'll give $150 for a pair.

[alwaysoar]

Re: never had this happen before

Until you bust a cover and have to find another one--I tried, and many said they'd look through their boxes of stuff when they had a chance, but no one produced what I needed. Plus I had the AM's, wanted LA's, but could'nt find any--My slicks are the best thing since chopped liver.

[WLT]

Re: never had this happen before

AD re Bendix switch applies to spring loaded "Start" switch only, I believe.
Have a cover for an Eisemann mag as E-mailed, decision was to go w/ Slicks.

[Robert Lees]

Re: never had this happen before

Until you bust a cover and have to find another one

I have a private stock, and no, they are not for sale.