LightSpeed Hall Effect Oil Seal Failure

[Kevin Horton]

Today I discovered roughly one teaspoon of oil inside the Hall Effect Module for my LightSpeed Plasma II system. there is no detectable play in the shaft. The system was working normally prior to this routine inspection. The unit has about 305 flight hours on it.

I'm waiting to hear back from Klaus, so I'll try the brain trust here. Has anyone replaced a Hall Effect Module oil seal themselves, or does the unit have to go back to LightSpeed for service? I'm hoping to fly to OSH, so I don't have a lot of time in hand.

If anyone has replaced the oil seal themselves, are there any tricks or special precautions?

[Walt]

I fought that problem for a couple of years when I had the hall effect unit, after 2 seal changes (done by Klaus) and a new unit I gave up and installed the crank sensor. The good news, the oil never caused a problem with operation that I could tell. I would not consider that a reason to ground the aircraft.

[deek]

Originally Posted by Kevin Horton

Today I discovered roughly one teaspoon of oil inside the Hall Effect Module for my LightSpeed Plasma II system. there is no detectable play in the shaft. The system was working normally prior to this routine inspection. The unit has about 305 flight hours on it.

I'm waiting to hear back from Klaus, so I'll try the brain trust here. Has anyone replaced a Hall Effect Module oil seal themselves, or does the unit have to go back to LightSpeed for service? I'm hoping to fly to OSH, so I don't have a lot of time in hand.

If anyone has replaced the oil seal themselves, are there any tricks or special precautions?

I politely suggest now would be a good time to remove the Hall Effect Module and install Klaus' mini-sensor or the larger direct crank trigger.

Absent that, yes the oil seal and bearing are easily replaceable in the field.

[Kevin Horton]

Originally Posted by deek

I politely suggest now would be a good time to remove the Hall Effect Module and install Klaus' mini-sensor or the larger direct crank trigger.

Absent that, yes the oil seal and bearing are easily replaceable in the field.

Switching over to one of the crank trigger options was a bigger job than I wanted to tackle with a trip to OSH right around the corner. I sent the Hall Effect Module back to Klaus to have him replace the seal and update it to the latest configuration. The current configuration includes a shield to reduce the amount of oil that hits the seal, but I'm not convinced this is a guaranteed fix to the problem.

If it happens again, I'll either bite the bullet and switch to a crank trigger, or pull the whole thing and install a second PMag. I'm hoping to avoid adding a second PMag for a while, as I'd like to see more service history before I go all-in on PMags. The potential for heat related shutdowns affecting two PMags concerns me. At the moment, with only a single PMag, I've got the Light Speed to fall back on if the PMag has heat related shutdown.

[Low Pass]

Glad you're back on line, Kevin. But can you elaborate a little on your concern with simultaneous heat related pmag issues?

Thanks

Bryan

[Kevin Horton]

Originally Posted by Low Pass

Glad you're back on line, Kevin. But can you elaborate a little on your concern with simultaneous heat related pmag issues?

The EMag and PMag are self-contained units, with all components in one location, mounted on the back of the accessory case. This simplifies the installation, and reduces the number of critical connections that the installer must make, which should reduce the number of potential points of failure. But, electronics are sensitive to temperature, and the PMag manual does warn that sufficient cooling air must be supplied to keep the electronics below 200 deg F. The manual states "Ignitions operating at exceptionally high temperatures can experience thermal shut down".

Normally, a 200 deg F limit should not be a problem. But, engines can get pretty hot during extended taxi on hot days (e.g. a rush hour departure from OSH), or if there is another failure that leads to a high oil temperature. If one ignition system shuts down, its an inconvenience. If they both shutdown, that's an engine failure.

Ignition systems are critical systems, and it is wise to choose a configuration that has no potential single failures, or operating conditions, that can kill both ignition systems. If the conditions behind the engine get hot enough to kill one PMag, the other one will almost certainly be subjected to the same temperatures, and would likely fail as well. So far, I've avoided this potential problem by having one PMag, and one Light Speed ignition. The electronics for the Light Speed are in the cockpit, so it should keep the engine running even if the PMag gets too hot.

So far, as near as I can tell, heat related shutdowns haven't been a problem, so perhaps there is more than enough temperature margin to deal with worst case conditions.

[Low Pass]

Originally Posted by Kevin Horton

The EMag and PMag are self-contained units, with all components in one location, mounted on the back of the accessory case. This simplifies the installation, and reduces the number of critical connections that the installer must make, which should reduce the number of potential points of failure. But, electronics are sensitive to temperature, and the PMag manual does warn that sufficient cooling air must be supplied to keep the electronics below 200 deg F. The manual states "Ignitions operating at exceptionally high temperatures can experience thermal shut down".

Normally, a 200 deg F limit should not be a problem. But, engines can get pretty hot during extended taxi on hot days (e.g. a rush hour departure from OSH), or if there is another failure that leads to a high oil temperature. If one ignition system shuts down, its an inconvenience. If they both shutdown, that's an engine failure.

Ignition systems are critical systems, and it is wise to choose a configuration that has no potential single failures, or operating conditions, that can kill both ignition systems. If the conditions behind the engine get hot enough to kill one PMag, the other one will almost certainly be subjected to the same temperatures, and would likely fail as well. So far, I've avoided this potential problem by having one PMag, and one Light Speed ignition. The electronics for the Light Speed are in the cockpit, so it should keep the engine running even if the PMag gets too hot.

So far, as near as I can tell, heat related shutdowns haven't been a problem, so perhaps there is more than enough temperature margin to deal with worst case conditions.

Understand, thanks.

[mr.sun]

My Plasma II ignition has been in service for 1100 hrs since 2004. I have a slow oil leak to the inside of the sensor housing that I wipe out with a rag every annual. Works well otherwise. I read a while back about drilling a small hole in the bottom of the housing to allow the oil to escape. Has anyone done this? Results? Seems I could monitor the progress of the leaking seal better but I'm concerned about any pressure differences that might cause the seal to fail faster.

Anyone have any idea how tough it is to replace that seal myself?

[jburr1]

mine just started to leak since last annual and has maybe a 1/2 teaspoon oil sitting in the bottom of the housing.
Had no reply from Klaus so decided to have a go at fixing it at home.

I just ordered a seal from amazon SKF 5790 LDS
is a 15-24-5 mm lip seal.
will advise how it goes on when complete. appears there are 2 bearings and 1 seal which is retained by a small c clip. Not sure why these things are prone to leaking, there is no load on it, no bearing play, but may be subject to crankcase pressure differential but that should be of little effect on a small seal area....

I have had no problems to date (250 hrs) with the unit and like the simple operation and ease of access. if I have to pop a seal into it every other year or so I will keep in operation. will report on process and success or not once I get to it.


regards

J

[Full Throttle]

Be sure to remove the woodruff key from the shaft before installing the shaft back into the housing. The woodruff key will scratch the seal when re-installing the shaft in the housing.