Jump to content

Rotax trouble shooting tip of the day


Roger Lee

Recommended Posts

Hi All,

 

I'll give this scenario and see if someone can tell me what the problem is and where to look to solve it. I'll give it a day or two for answers then I'll give the answer to this problem. I was called with this problem the other day and it was solved in about 3 minutes.

 

You start your engine and go fly and everything seems normal. When you land and turn off the key the engine keeps running at a very slow rpm and it looks and sounds like it is running on one mag. What's wrong and where might you look to find the problem?

 

p.s.

Don't over think it and start at the most obvious potential solution.

Link to comment
Share on other sites

Here is the answer tothis particular problem. Itwas a broken white ground wire going into one of the ignition module pin connectors. There is onewhite ground wire that goes into each plastic pin block and it is in a cornerhole on the pin block. I always say something is finger tight, but wrench looseand the same goes for wiring. So unless you grab each wire and look at it fromstart to finish it may be broken or pinched or chafed against some metal orhanging by a thread causing a poor connection, ect...

 

Here is the clue thatmade me tell him where to look first. The plane ran fine at all rpms. Only whenhe turned the key off it did not want toshut down completely. He said it sounded like it was running on only oneignition module (mag) and of course at a reduced rpm. So it sounded as if onemag was shutting down, but the other was not. So the very first thought shouldbe if one is shutting down why isn’t the other. When you turn the key off itshould ground out. So for me the first thing to check before bouncing all overlooking with no logical direction was to look at both ground wires since theyare easily accessible and usually easy to visualize. While I was talking tothis gentleman on the phone telling him which wires to look at he was grabbingone of the white wires and it came out of the plastic pin block at the ignitionmodel broken. He said he just barely tugged it and it was out. This is theignition ground wire. It was broken up inside the pin block where it wascrimped. By replacing the crimp on the end of the wire he was ready in shortorder. Yes there could have been another problem somewhere else, but theidea here is to start in the most logical and easiest area to inspect first.

 

I guess the moral of thestory is to develop good diagnostic skills and then teach yourself to start atpoint “A” then to “B” and so on. You need to know where the starting point isand where the most logical problem area is and start from there. Eliminate allthe easy most logical points first then you can tear into more hard to reach orcostly areas. This approach will save you time, money and aspirin for theheadaches.

 

 

 

 

I hope this story helpssomeone that may have the same type of engine shut down issue with a startingpoint for your resolution.

 

 

Link to comment
Share on other sites

So it's not the flux capacitor??? :D

 

Great post Roger. It is always a rule of thumb to always give a wire a slight tug during an inspection or troubleshooting. Sometimes a wire will make just enough contact and appear to be intact. As soon a you touch the wire it is actually broken.

 

I just fixed a 182 that wasnt charging all the time. I started at A and went to B and fixed the itty bitty wire in 10 miutes. Customer was very pleased. Then he told me he had his mechanic up north change everything on the aircraft. It worked for the flight here and was dead on the ramp. Waisted a lot of $$$$$

Link to comment
Share on other sites

Hey Roger, you forgot to tell the guys who guessed a bad ground and/or P lead they get an "A". The white wire might not be called a P lead on the Rotax but it seems to function similar by grounding the ignition.

Link to comment
Share on other sites

Hey Roger, you forgot to tell the guys who guessed a bad ground and/or P lead they get an "A". The white wire might not be called a P lead on the Rotax but it seems to function similar by grounding the ignition.

 

Question: If electrictical wiring principal similiar, then is it possible for a ROTAX engine to fire if the switch is off when moving the prop to pump oil into the tank during preflight. I think no, since there is no impulse coupling, but just had to ask those that know.

 

Doug in IL

Link to comment
Share on other sites

  • 1 year later...

Just wondering about sustainable sources of fuel out in their environments. I guess diesel makes sense. Is ROTAX a player in UAV power plants...?

 

 

 

Thanks Eric

 

The Rotax has been a major player in many UAS around the world both the 912 and 914. Several I have flown were Rotax powered and were rock solid for hours and hours. We would easily climb to 30k feet and loiter for 20-30hrs refuel and do it again.

 

We now run our engine (not rotax) on readily available JP8, or Diesel 2 or anything close to that.

Link to comment
Share on other sites

Hurray for ROTAX.....would we be able to relate a UAS ROTAX to one of ours, or are they built differently.....Manl thats got to be good for ROTAX business....do they fix them or just replace when something breaks or times out? Enough of the 64 $ questions.....cool....nice to know maybe ours benefits from all those hours of usage experience.

Link to comment
Share on other sites

Hi Doug,

 

Those were mainly turbo 914's and they have been moving away some in the last few years. They were to be rebuilt I believe once then tossed in the trash, but some of these made them to the civilian population which wasn't supposed to happen. They are tired engines.

 

Eric,

If I'm off a little here jump in and correct it.

Link to comment
Share on other sites

The couple programs I worked, we would run the 914 for 300 hours doing normal maint, remove it after 300 hrs, inspect it via a tear down, then run again for 300hrs and repeat up to 1200hrs I think. After that I think they went to full overhaul. That was a few years back though and since i am mainly on he flying side of the house not the maintenance side I may be off a little.

 

Rotax has been able to gain a lot of experience with all the UAS flight hours which I think has gone to product improvement and increasing TBOs. The basic engine is the same used in many civilian applications, the accessories is what sets them apart.

Link to comment
Share on other sites

Thanks Roger.....in all your years has the basic 912 been completely made over....and now a differenct engine? I guess so with the 2000 TBO.....problably answered my own question...happy to know anything that makes our engines more bullet prof like an old 0200 or 235.......

 

I guess being stuck out in middle with no convienent maint support I'm always seeking a vote of confidence that the engine is more robust because the day i have some not readily identifiable problem, well then I'm going to be in a world of hurt trying to diagnose the issue.....especially if its like the recent blog......I guess if I have a complecated issue....I'd be better off rather than trying to tear in to it, without training and special tools, knowing how to dismount and pack up for shippment to a repair station....man if and when that happens away from home....what a heartache

 

 

 

 

Thanks Eric---I love my little engine and it isn't tottaly unforgiving its just too special when it comes to maint support......and I dont see it growing in my geo area all that much. Really lack local medium and heavy maint support.....No news there....just as time wears on.....it crosses my mind....what if?????

Link to comment
Share on other sites

Hi Doug,

 

The 912 is still the same basic engine it was, with a some changes;

the 100 HP over the 80 HP, the slipper clutch introduction for the gearbox, a new crankcase in 2006, a few changes to the valve spring keepers, the oil dip stick change for more oil tank volume, ignition coil changes, ect..... there are several more and you can find these things in older manuals and look at the Rotax SB's and they have many of the changes in them over the years. There are a few significant changes. Just the titles will help you.

Link to comment
Share on other sites

Thanks for the particulars Roger and Eric..for when that time comes; I can change a tire, plugs, oil, ad cherry juice to the brake system, and jerk the dynons and avionics, but that is really it and 100 miles...is kind of a comfort limit I put on my travels to be able to recover my machine via truck..... just concerned if I have a materiel kind of breakdown...then what.......evac the radios and personal items because the airplane is stuck.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...