LASAR Mags

[Bob Axsom]

Last year a fellow said he had his second LASAR Mag failure at appoximately 300 hours of service. I said that short MTBF caused me some concern. Today my LASAR Mag failed the mag check - time 306 hrs.

Bob Axsom

[osxuser]

I know of a LASER mag that timing went nuts on a ruined a 300hr old IO-360. I'll pass on those babies.

[Bob Axsom]

There was a fellow last yeat that had two of the mags fail after 300 hours on each one. As I recall he was at S'n'F last lear when the last one occurred and he was trying to get his hands on a LASAR timing tool. I believe he was going to install a different electronic egnition system. I would like to have the details on his failure mode(s). I have been working honey do's and disaster late freeze yard work all day so haven't gotten into the mag check failure fix yet. I have had good luck with the LASAR system and will stick with it for this cycle but I would like to know how the change worked out also.

Bob Axsom

[AlexPeterson]

Bob, that fellow would be me. I'm not near my logbook, so I'm going on memory here and basing the hours more on when I recalled that they happened calendar-wise. I'm running an O360.

Failure #1 was around 350 hours, and was a partial failure of the left mag. During a ground mag check, the engine would slowly and a bit roughly die down when running on the left mag. I did not hear what the failure mode was, except that when I described it to Unison's engineer, he seemed to recognize it.

Failure #2 was around 650 hours, and was in flight. The engine was running normally, there was a fractional second power loss, and then power was restored albeit a little rough. I then noticed no tach indication (left mag sends out electronic tach signal), and higher egt's. I did a 180 and flew 10 minutes back to the airport. None of Unison's diagnostics could find this failure when applied to the plane. Unison thought the problem was in the box, so I sent that in and they said it checked out ok. I sent the left mag in, and they told me that the shaft inside it had broken. The difficult diagnosis was because the guts of the mag weren't even turning, a failure mode they hadn't contemplated I presume.

Failure #3 was at 740 hours, and was identical to #2, except that I was 1200 n.m. from home.

It would appear that they had some sort of torsional resonance in the shaft in the mag that wasn't contemplated during their testing, leading to fatigue failure. I believe they are redesigning or have redesigned the shaft. I typically run at 2300 to 2350 rpm in cruise, which shouldn't be outside of normal rpms to examine.

Unison was very good about covering the costs, all three replacement mags were at no charge (they are about $800 a pop).

[Bob Axsom]

Thank you so munch for the good information Alex. My failure is associated with the right non-sensor mag. the symptoms are very similar to your first mag failure.

Bob Axsom

[Mike S]

This thread is very interesting to me, as the project -10 I recently bought already has the Laser system on it.

I had/have no knowledge about this system prior to ending up as an owner of it.

As I understand the Laser setup, it is basically a traditional magneto setup, but the timing is controlled by a black box that monitors the rpm, cht, and who knows what else, and then sets the timing automatically.

The short time before failures concerns me a lot. Alex mentioned that he thought there was a re-design of the shaft going on---------any idea of when this may have happened, and how do I determine if I have the old style units, or if I have the newer ones?? And, if the problem has been solved with this change.

Lastly, any input as to if I should just take the Laser off, and go with something else?? It would be a simple thing to do at this time, as there is no wiring done yet, nothing to re-do.

Mike

[Bob Axsom]

My black box is not hooked ut to the CHT because I don't want the box to limit power to automatically protect the engine - I'll do that. There is a sensor magneto and a non-sensor magneto and the sensor magneto provides an input to the black box (controller). The other input is manifold pressure. The system requires a special timing box which was available from Van's for something in the $300-$400 range as I recall. You can buy a complete manual set from Unison and an interface test cable for running diagnostics using a lap top computer. The manual used to cost $75 with free updates for a year and the interface cable costs something like $250. They claim that the system can increase horsepower by someting like 8% - not verified by me but it has worked fine up until the failure of the right mag a couple of days ago.

I think Unison is commited to the system and improvements will no doubt evolve. To find out about your hardware configuration I would call the an talk to the customer support engineer.

Bob Axsom

[OldAndBold]

Would someone be so kind as to direct me to a thread or explain how to choose / understand engine ignition systems? What I want for my plane is reliable safe operation. From this thread, it sort of sounds like buying the most expensive system is not necessarily the best approach.

Any adfvice on how to choose ignition systems would be greatly appreciated. I am planning on getting a Superior XP-360 of some sort - the more conventional the better...

Thanks in advance,

[Bob Axsom]

If you are not trying to optimize performance the tried and true magnetos will never let you down. From your description that is exactly what you want. You cannot hand prop a LASAR ignition system for example. If you are flying along and kill the engine by running a tank dry and you have a dead battery you can restart it with the 1500 rpm windmilling prop but a dead battery is a no-start condition on the ground. If you get a dead battery on the ground and try to jump start it, the prop will spin it will not start for me. I used to fly a factory built plane to work every day in Los Angeles and in the 15 years it was good to be able to connect the car battery with jumper cables and keep the commute going. The culture is now sacrificing independent system types and accepting redundancy but reading between the lines I don't think you have bought into that. I think you would be most satisfied with standard magnetos.

Bob Axsom

[OldAndBold]

Thanks Bob.

--JCB