914 Stuck Waste Gate Lessons Learned

[grantopperman]

Sept 6, 2019 20:37:23 GMT buzz said:

So I am confused a little Dave. How does this jive with Ed's situation with his dead stick landing. Up to this point I have only used 100LL and Decalin. Sounds like that since I am 100% 100LL and Decalin that I should be using Sport 4. But then how do I keep Ed's situation from happening to me?

I'm in the same situation since I have no easy access to mogas.

I change oil at 25 hours as the Rotax manual says (learned to do it myself because it would be a pain to have a mechanic do it that often). Like you, I also add Decalin.

Also, a few months ago I attended Rainbow Aviation's course for Light Sport Repairman - Inspection. The super knowledgeable guy who taught the course (Jim Scott, Aircore Aviation) said he advises Rotax owners at shutdown to turn the fuel selector to OFF and run the engine until all the fuel is exhausted and the motor stops. The idea is that this completely removes residual fuel from lines and carbs. So, there's nothing left in there to crud up. He only recommended this if the plane was going to sit unused for more than several days. I have adopted this practice.

Keep in mind that Ed's dead stick, while real and frightening, has to be a pretty unusual circumstance. If Rotax pilots were falling out the sky with regularity, the manufacturer wouldn't survive long!

[buzz]

Sept 6, 2019 20:50:21 GMT grantopperman said:

Sept 6, 2019 20:37:23 GMT buzz said:

So I am confused a little Dave. How does this jive with Ed's situation with his dead stick landing. Up to this point I have only used 100LL and Decalin. Sounds like that since I am 100% 100LL and Decalin that I should be using Sport 4. But then how do I keep Ed's situation from happening to me?

I'm in the same situation since I have no easy access to mogas.

I change oil at 25 hours as the Rotax manual says (learned to do it myself because it would be a pain to have a mechanic do it that often). Like you, I also add Decalin.

Also, a few months ago I attended Rainbow Aviation's course for Light Sport Repairman - Inspection. The super knowledgeable guy who taught the course (Jim Scott, Aircore Aviation) said he advises Rotax owners at shutdown to turn the fuel selector to OFF and run the engine until all the fuel is exhausted and the motor stops. The idea is that this completely removes residual fuel from lines and carbs. So, there's nothing left in there to crud up. He only recommended this if the plane was going to sit unused for more than several days. I have adopted this practice.

Keep in mind that Ed's dead stick, while real and frightening, has to be a pretty unusual circumstance. If Rotax pilots were falling out the sky with regularity, the manufacturer wouldn't survive long!

Thanks that makes sense.

[DavidOber]

Sept 6, 2019 20:37:23 GMT buzz said:

So I am confused a little Dave. How does this jive with Ed's situation with his dead stick landing. Up to this point I have only used 100LL and Decalin. Sounds like that since I am 100% 100LL and Decalin that I should be using Sport 4. But then how do I keep Ed's situation from happening to me?

I wouldn't worry about it too much.  A majority of Rotax users have been using Sport 4 without issues.  I was just trying to pass on some information for discussion as I am dealing with a specific gunked up turbo.  I betcha 98% of Rotax guys use Sport 4....and I would have no issue continuing to use it.  I just might try Mobil to see if it makes a difference with my waste gate issues.  As for Ed's experience,  I let him speak on the specifics of that.

[Ed Midgley]

That’s the catch.
My Rotax instructor said Rotax and Shell won’t admit it but Sport 4 has problems with turbocharged engines.
With 100% avgas change the oil every 25hrs and clean dry sump tank.
It’s making the best of a bad situation.
Ed

[buzz]

Sept 9, 2019 22:52:55 GMT Ed Midgley said:

That’s the catch.
My Rotax instructor said Rotax and Shell won’t admit it but Sport 4 has problems with turbocharged engines.
With 100% avgas change the oil every 25hrs and clean dry sump tank.
It’s making the best of a bad situation.
Ed

So Ed are you saying that if I used 100LL and Sport 4 that changing the oil at 25 hours eliminates your problem?

[Ed Midgley]

No, with Mobil 1 change it every 25hrs with Avgas.
I will admit we don’t here of planes falling out of the sky every week.
When it happened I thought I blew the turbo and called Lockwood to order a turbo. They didn’t have one and suggested I call Rotec (sic) in Canada who are the certified Rotax importer for North America. They also didn’t have a turbo but the fellow was very knowledgeable and asked me what happened. He immediately told me I coked up the scavenge line and how to clean it out. In other words this wasn’t the first time they heard of the problem.
Ed

[buzz]

Sept 10, 2019 3:04:04 GMT Ed Midgley said:

No, with Mobil 1 change it every 25hrs with Avgas.
I will admit we don’t here of planes falling out of the sky every week.
When it happened I thought I blew the turbo and called Lockwood to order a turbo. They didn’t have one and suggested I call Rotec (sic) in Canada who are the certified Rotax importer for North America. They also didn’t have a turbo but the fellow was very knowledgeable and asked me what happened. He immediately told me I coked up the scavenge line and how to clean it out. In other words this wasn’t the first time they heard of the problem.
Ed

Ok thanks Ed. You provided some clarity in saying "it wasn't the first time". This is what was concerning me. I was having a hard time believing that I should ignore your experience. I think I will be changing to Mobile 1.

[montanapilot]

There are definitely mixed opinions re oil.
I spoke with a very knowledgeable person who's with one of the 3 large Rotax distributors. He said that there's a difference between what Rotax recommends and what people in the field recommend. His opinion is that Rotax is recommending Sport 4 is because it suspends lead better, but also because they didn't want to be recommending 2 types of oils - one for use with 100LL and the other with autogas.
This person clearly prefers synthetic oil for the 914 even if you're running 100LL, and definitely if you're running autogas. However, he prefers Amsoil Synthetic Metric Motorcycle oil over the Mobil product, although he likes the Mobil product as well. He noted that the Mobil product is better known and that's probably why some people are using that instead of the Amsoil product.
He commented that "the Rotax engine is much more like a motorcycle engine than it is a traditional airplane engine." He said that synthetic oil is designed for high rpm engines.
He said that the coking issue has to do with "volatility", and that the Amsoil product has the best volatility specs.
I asked hime "what are the side effects or disadvantages of the synthetic oil?" and he said that he didn't know of any.
He cautioned re what we've all heard, but it doesn't hurt to repeat; (1) keep your oil temp up. He's recommending 225 degrees. However, the sensor is not installed where oil is at its highest temp, so he'd like to see 215 on the gauge.The main issue here is that when moisture accumulates in the oil, it ends up at the lowest point which is, in our case, the turbocharger, and according to him, that can cause the bearing to stick,(2) as we all know, if running 100LL, change oil every 25 hours, (3) fly for at least an hour, and (4) he talked about the cool-down period prior to shutdown. He suggested 5 minutes, but that would include time taxiing in to parking. His main point was to note the oil temp prior to reducing power for approach, and then just make sure that you see a visible temp drop before shutdown.
I also spoke with this person's counterpart at another distributor. He was mainly in favor of using the Mobil product over Sport 4, but he felt that it doesn't really matter to a great extent, especially if you do the things I noted above (1 through 4). He said that the advantage of Sport 4 is that it suspends lead, but it also cokes more.
In the spirit of "everybody has their opinion", I asked somebody at the Rotax tent at OSH about the oil temp. I told him that I'm never reading more than 190 degrees. He felt that was fine, again citing the fact that the probe is not at the hottest part. I'm going to go with the more conservative approach and tape my radiator enough to keep the oil temp around 105-110.
To add to the confusion, I mentioned this to one of the shops with whom I work - somebody very experienced and knowledgeable - and he recommends staying with the Sport 4 and making sure re numbers 1 through 4 above.
I wish this was more clear cut, but the fact is that different people definitely have different opinions.
I also need to say that I have great respect for Ed's opinion, so I'm keeping my decision re which type of oil to use open, although at this point I'm leaning toward the synthetics, as he seems to be, and I'm running 100LL.

[DavidOber]

I'm not sure there is a correct answer for all....but all this discussion is very valuable in formulating a strategy going forward and hearing what other people have experienced and heard on the street is good stuff.

[Ed Midgley]

This is how I control oil temps. The door is controlled by a vernier cable in the cockpit. It helps that I’m experimental.
Ed

Attachments:

[montanapilot]

As lovely as my taping jobs are, this is very cool and would make things so much easier.

[ATP Time Builders]

I am not yet an owner - no manuals. Could someone tell me what Chapter 5 says about oil and frequency of changes for P2008 non-turbo running AVGAS?

[MarkGregor]

Eds engine has a few changes from our regular 914s. Lets just say he has ALOT more power.

I'm confident the average 914 will be fine with the Sport 4.

Mark G

[MarkGregor]

Just wanted to respond to the stuck wastegate/stuck turbo shaft issue. It is most likely to happen on new or newer aircraft when the turbo shaft tolerances are still very tight. After they break in seems like the problem goes away.

I just spoke with Bruce at Wells Aviation and both he and I agree with Davids suggestions. All engines should idle a bit before shut down not just turbos. Another big one is using the engine hard enough to burn the carbon out of the wastegate so it doesn't get carboned up. Several have heard me say it but if you don't get the engine warmed up good once in a while its going to carbon up and possibly stick the turbo or wastegate.

 My suggestions are to use the full 5 minutes at 40 inch manifold power regularly and if your going somewhere run the engine at the 35 inch manifold setting at least some of the time. He felt the sticking is more of an operating temp issue and not caused by 100LL. 

Bruce said water condensation in the oil is the other likely cause. Our Tecnams have oversized radiators and oil coolers which are great for operating in hot weather but can allow them to run on the cool side in colder weather. He said the planes need to be above 212F for an hour to be sure all the water is out of the oil.

Lastly he agreed with Eds choice Mobil 1 oil for our turbos and to change it every 25 hours although he felt the Sport 4 was ok also. He is a big believer of regular oil changes no matter what fuel you are using.

Main thing is to at least occasionally use the engine hard and long enough to keep the carbon burned out and the water out of the oil and you should be good!

Mark G

[DavidOber]

Thanks Mark...no problems since we started using all the recommendations. We get some funny looks from line guys with our 5 minute sign language and have kept the waste gate lathered in mouse milk, and stuck to mogas. Hollie and I just changed the oil to Mobil1...So I watched the rotax video bought a torque wrench and safety wire and we get all ready and I notice we have a quick release installed that makes draining a breeze..my wife just laughs at me. I will keep the group updated.

David