single magneto start

[flyguy]

Anyone feel like a comment on the ease or difficulty of starting an engine with a single coupled magneto vs with couplers on both.
Previously I had two coupled mags and it was always a one blade starter, but just now it would be convenient to put on one without a coupler. (Don't ask, chuckle.)
Big difference? or no matter?
Darryl

[Ragwing nut]

Re: single magneto start

If running only one impulse, it will be, "should be", easier to start on one mag only, otherwise you have each mag firing a two different points. However each engine is its own monster so what works for one does not always work for another.

[jpowell]

Re: single magneto start

The reason for the impulse coupling is so that the mag fires at top dead center. If you only have 1 impulse coupling you start it on that mag. The non impulse coupled mag will fire at normal advanced timing. If that happens it will kick backwards because it fires the mag before TDC.

[mike lutz]

Re: single magneto start

start on mag with the impulse,then after it starts switch mag switch to both.

[flyguy]

Re: single magneto start

Thanks guys, but I understand how magneto's and impulse couplings work, (better than you can even imagine, LOL), I just was hoping that someone could confirm what I suspect, that two couplers make for more consistant single blade starting, but that it isn't that big of a deal. My take is that getting two sparks in the cylinder that comes up gives a better chance of firing, but using just one is satisfactory also.

Let us say, without details, that at this point it would require a lot more effort but no expense for me to have two rebuilt units with couplers whereas I presently have one coupled and one uncoupled, ready to go, and can have my plane back in the air in a day or so.

The one advantage that I see with the uncoupled unit is that it is MUCH simplier mechanically and therefore more reliable as a last ditch unit that will always get you home. Plus in my case, I have one that is ready to go.

Hoping someone would either say: "Been using one for years, no problem starting," or "Use 2 if you can because starting with one is a real pain."

Understand that these are Eisemanns that will require pulling the engine if I want to put in a coupled unit at a later time.
Darryl

[Robert Lees]

Re: single magneto start

Our Eismann's come right off without pulling the engine, Darryl.

One disadvantage of two impulses is that you have twice the chance of an impulse spring breaking (and I've had three over the years). The engine will not run with a broken impulse spring, so I always carry a spare on board.

[Ragwing nut]

Re: single magneto start

No requirement to pull the engine to install impulse Eismann's unless you are running the wrong mag gear with a Lycoming impulse spacer. They are no longer than the non-impulse mags. Yes 2 is better than one, but check the TC data sheet first for the engine and make sure it is legal. I don't ever remember running dual impulse mags on any A series Continental.

[Pearson]

Re: single magneto start

I have been flying my airplane for about 8 years with only one impulse coupler. "Been using one for years, no problem starting". It took awhile to figure out the process of getting it started, but now that I have, it almost always starts on the first blade. But as Mike said above, "However each engine is its own monster so what works for one does not always work for another".

[VictorBravo]

Re: single magneto start

Our Eismann's come right off without pulling the engine, Darryl.

Now you have my most sincere attention... do tell!

[Robert Lees]

Re: single magneto start

Bill: I don't have photographic details...but I remove the leads, undo the two hold-down nuts (1/2 inch as I recall) and withdraw the AM4 mags. One has an impulse, the other doesn't, but they're both easy to remove. A-65, short mount. It seems a simple as that.

I only have to pull the engine to remove the exhaust, and I fixed that by putting a joint in the "long straight"...but see another thread for that.

[rotaxflyer]

Re: single magneto start

My T is equipped with one impulse and one non-impulse magneto (both eisemanns). It starts very well. It is actually better than the other small continentals in the hangar. I always start on the impulse mag only and then switch to both.

Andy

Anyone feel like a comment on the ease or difficulty of starting an engine with a single coupled magneto vs with couplers on both.
Previously I had two coupled mags and it was always a one blade starter, but just now it would be convenient to put on one without a coupler. (Don't ask, chuckle.)
Big difference? or no matter?
Darryl

[flyguy]

Re: single magneto start

I have, and I believe Bill has, the LA-4 units which are longer than AM's and have minimum (like a RCH if you know the term) clearance with the firewall on a short mount. Appreciate the input anyway Robert.

I must have flown something with a single coupled mag at sometime, as I remember the procedure. Likely the tandem "B" models I flew for my first few hours of training.

Never had a coupler spring break, but I did notice that the ones I had wound lately seem to be tighter than before. Hope that isn't going to be a problem.

Engine is a C-85 so A model specs. don't apply.

Ok, it is one with a coupler and one without and I'll carry an extra coupler with the spring installed as suggested. Good Idea.
Thanks for the information everyone.
Darryl

[Ragwing nut]

Re: single magneto start

I have, and I believe Bill has, the LA-4 units which are longer than AM's and have minimum (like a RCH if you know the term) clearance with the firewall on a short mount. Appreciate the input anyway Robert.

I must have flown something with a single coupled mag at sometime, as I remember the procedure. Likely the tandem "B" models I flew for my first few hours of training.

Never had a coupler spring break, but I did notice that the ones I had wound lately seem to be tighter than before. Hope that isn't going to be a problem.

Engine is a C-85 so A model specs. don't apply.

Ok, it is one with a coupler and one without and I'll carry an extra coupler with the spring installed as suggested. Good Idea.
Thanks for the information everyone.
Darryl

If you have a C-85-8, firewall clearance is the same as an A-65. However if you are running a -12 with block off plates on starter and generator, then I can see you firewall clearance problems since the rear case is deeper.

Not really any depth difference between the LA and AM mag, AM may be SLIGHTLY shorter but I am not sure it is approved on the C85. Also if you are running a -12 engine, I think they are suppose to have 2 impulses, but double check the TC data sheet.

If you are carrying spare parts for eismanns, carry extra set of drive gears since they are still phenolic. Bendix was smart enough to replace with steel. i have had a drive gear fail and is not fun.

[taylorcraft078]

Re: single magneto start

Mine has one impulse and one normal. I found that it was a lot easier to hot start on the impluse mag. Cold starting is done on both.

Dave
N36078

[flyguy]

Re: single magneto start

It's a -12, blocked off, and the drive gears are steel.
DC