Engine Analyzer Question/Lean vs Rich of Peak/Engine Longevity

[Walter Atkinson]

Kyle:

For the most part I agree with your post. A couple of very minor nits in the interest of accuracy:

1) The mixture where the highest CHT's and highest ICPs are noted is between 25 and 75dF ROP.

2) We have tried to induce detonation at any LOP setting without success as long as the timing is set correctly and the fuel is correct.

3) The most detonation-prone mixture setting is 40-50dF ROP. That is a fact of the physics.

Walter Atkinson
Advanced Pilot Seminars

[Rickskymaster]

I just got off the phone with TCM. They told me that anything that is traceable to the GAMI's that causes a problem will void their warranty. When I pressed, and asked what "anything" meant, the lady told me I would need to call back in the morning and speak directly with the tech department.
I also asked if TCM had ever voided a claim because of GAMI's, call back and ask the Tech guy.
I should say, that I called at 500pm Mobile time and the department closes at 430.

[gwbraly]

>> do what the manufacturer tells you: stick with ROP.

Ernie<<

Ernie, cut me a bit of slack, please, because my response is going to be a little bit "hard". It is not directed at you, but it is designed to illustrate the problem.

So your statement is "true" - - but only if one excludes each of the following manufactures from the scope of the statement:

Teledyne Continental Motors;
Piper;
Mooney;
Cirrus;
Lancair;
Lycoming;
Cessna;
Beech;

Each one of which specifically approves or endorses operation lean of peak for their most difficult high powered engines.

Regards, George

[gwbraly]

>> They told me that anything that is traceable to the GAMI's that causes a problem will void their warranty. <<

Rick, that is and always has been their warranty position with respect to any STC'd anything that one puts on one of their engines.

You don't have to call, we have a letter that says the same thing.

We have about 10,000 sets of GAMIjectors flying around on TCM engines. We have about 350 Bonanzas and Cessnas, with not only GAMIjector(r) fuel injectors, but also with turbo systems added on to their engines. Naturally, we keep pretty close tabs on these issues. So far, to the best of our knoweldge, after nearly 10 years, TCM has never declined a warranty claim because of either the fuel injectors or the turbo normalizing systems.

Regards, George

[KyleTownsend]

It would be great if somebody did a scientific survey of engine longevity in the "control group" (manufacturer recommended settings) versus the "experimental group" (gami's / LOP).

Unfortunately, this kind of thing is pretty hard to do in GA because of the small sample size, fairly long engine life, and number of extraneous variables.

It sure would make it a lot easier to let go of $8,000 or so if I was reasonably certain that I would get it back in extended engine life.

Of course, the fuel savings alone are compelling, but $8K is a lot of gas at my burn rate.

If anybody is aware of any studies like this, I would be very interested.

[KyleTownsend]

>In the real world, no one can deny the robustness of these engines when they are operated per Continental's recommendations.

I'm afraid I am going to have to take issue with this statement. I think the robustness of the engines is questionable. I was looking at some back issues of Aviation Consumer a while back, and they listed the TSIO360 engines in their "worst engines" category. Their basis was an informal survey of overhaul shops. Apparently, these engines are quite a bit less likely to make TBO than the average engine (especially not without some top-end work).

It would be easy to blame the pilots and just say that there are too many "ham handed" pilots flying around in Skymasters. However, I doubt, as a group, that we are any worse than Barron owners, for example.

Looking back at our log books, neither of the engines even came close to making TBO. While I suppose that the previous owner may have been "ham handed," he sure didn't strike me as that kind of guy. Quite the contrary, he seemed to be a very precice and conservative "engineer type" who really took care of the plane (he was the only owner since new, and was trading up to a King Air).


PS: I am not trying to make the argument that running LOP would solve this problem. I think the jury is still out on that. It's just an observation.

[Kevin McDonnell]

Kyle,

That's a great point about a controlled study of engine longevity. It's strange that the manufacturers haven't done this, but I suspect it would only further illustrate their poor QC.

What would you expect to see if you tested two identical engines in exactly the same conditions, power settings, fuel flows, leaning techniques, temps, etc.?

This is exactly the environment in which twins operate. You might argue that a Skymaster front vs. rear engine is not an identical installation, so let's leave that out of this example. A conventional twin with a right and left engine are operated this way.

Just look at Trade-a-Plane and see how many twins have very different times on their left & right engines. Continental & Lycoming can blame pilot operation all they want, but this example clearly shows that the problem with these engines is in the manufacturing.

[gwbraly]

Kevin,

The twin argument might well be correct, but it might not.

For example, how many of those twins had the fuel flow set up "differently" for the left and right engine, so that they experienced very different internal cylinder pressures on each takeoff and climb?

Clearly TCM is having problems with valve fit and geometry.
We saw one 78 hour TTAFE Bonanza that had a prop strike. On engine tear down, the #6 exhaust valve was wobbly in the valve guide - - at 78 hours of run time.

Regards, George

[KyleTownsend]

I strongly suspect (but can't prove) that the #1 factor in engine longevity for the piston fleet has more to do with usage patterns. Or, more accurately, lack of usage. I doubt that there are many airplanes out there that don't experience an occasional period every few years where they sit for 30 days or more without being flown.

I read an article some time ago that supports this theory on an anecdotal basis. I was about one of the commercial piston operators (cape air or island air, I think). Their operating policy only allowed their pilots to use 4 distinct power settings for simplicity. They didn't have engine monitoring or anything fancy. And yet, they routinely made extended TBO's in their 400 series Cessnas (I believe the extended TBO was in the 3,000 hr range).

I am guessing that quality control at the factory would be the #2 factor, and that engine mismanagement would be #3.

I think that it is telling that we don't have anything like "Power by the Hour" in the piston fleet (to my knowledge). The turbine boys have had these kind of programs available for years. I can't believe that entrepenuers (or even the factories) haven't looked at offering this for piston engines, and have run scared because of the variability in piston engine life.

[Walter Atkinson]

Kyle:

I'm going to combine a few comments into one post. Some of these things are not in answer to you, but to others.

The scientific study you would like to have done has already been done... long ago. The results were very compelling and support the statements George, Tom and I have made in this thread and in others. The study was over a sample size of 400 MILLION flight hours of data. No one I know (who has read it) thinks there is any reason to duplicate it. It would be very expensive to do so, and to what end? TCM and Lycoming DATA agrees with that study.

More recently, the FAA conducted a study which proved beyond any doubt that lead is not a lubricant for valves, but that OWT won't go away either.

The concern over the cost of an engine monitor to save gas is misplaced in my opinion. Engine monitors tend to pay for themselves all at once and in spades. The cost savings is not over fuel, it is over a serious engine problem which threatens your wallet and/or your life. My best calculations figure that my engine monitors pay for themselves at least once every two years in maintenance savings alone. I have a growing list of pilots who have saved their engines and their LIVES becasue they had an engine monitor. That's not at all an exaggeration. Do not buy an engine monitor to help you lean the engine. It will do that, but buy and engine monitor to save you maintenance costs, save your engine, and maybe yourself. I don't know a single pilot who understands how to interpret an engine monitor who is now comfortable flying without one. It was an unexpected effect of having the information so radily available.

[KyleTownsend]

I would be interested in seeing the study you are talking about. Where do you get it?

On the subject of engine monitors, I tend to agree with you. Or at least, I agree that fuel savings are not enough for me to justify the cost of one (might be if I was flying around in a twin beech!).

The kind of data you are talking about is what I am interested in. Intuitively, it is obvious that having an engine monitor "could" save you a lot of money (or your butt), but it seems like it's pretty hard to put a pencil to because of the "all at once" factor. How often does "all at once" happen on average. Once every 100 hours, or once every 10,000 hours (I think the average for accidents resulting from in-flight engine failures is once every 30,000 hours, but don't quote me because that's just my vague recollection).

You say that you figure your monitor pays for itself every couple of years in maintenance savings, and that you have actually put a pencil to this. I would be interested in hearing more about that.

[gwbraly]

The 400 million hour study is the product of the fleet experience y done on the CW 3350 engines - - about 400 million engine hours, and all of that LOP in cruise at high BMEP values, compared to engines you and I fly. Towards the end of the piston airline era, they were going to 3600 hour TBO's on those engines.

As for the engine monitors, consider this, you taxi out on a time critical trip to grandma's house for Thanksgiving.

You have a rough mag.

You taxi back and tell you mechanic one of the two following statements:

1) The Left mag is rough on the front engine; or,

2) Please change the #2 lower spark plug on the front engine, it is bad.

What is going to be the delay in getting to grandma's house?

What is going to be the difference in the amount of time your mechanic spends on fixing your "rough mag" ???

Is your mechanic going to respond to 1), and say, "Hey, I have two other planes in the shop I am finishing up for guys for Thanksgiving trips, I can't get to your troubleshooting problem until tomorrow..." or is he going to say, "Sure, I can get the plug changed in about 30 minutes."

The spark plug example is just the very beginning of a long list of similar easy diagnostic "catches" that result from owning an engine monitor and then learning to understand what it is telling you.

Again, as has been pointed out, if you make a serious effort to evaluate the failure modes and effects, one quickly realizes that the person who operates ROP really needs an engine monitor more critically than does the person who operates LOP.

Regards, George

[TGresham]

Kyle:

I can offer only my experiences, but I have come to think of the modern engine monitor as an extremely important item in the panel.

It does a lot more than most pilots know, including those who already have one.

An example of how it saves money, and time. (Time is the more scarce resource.)

I was flying back to Louisiana and was making a fuel stop in Louisville, KY. When I started the descent, I felt a very slight rumble in the seat of my pants. The passenger did not notice it.

Without the engine monitor, and the knowledge of how to use it, I might have shrugged it off and pressed on, or I would have to tell the mechanic "it's a funny rumble that I can kind of feel, but I don't know where it's coming from."

Instead, when I landed, I told the mechanic that the spark plug in the number three cylinder -- the plug running off the right mag -- was going bad. I had him replace it while we had lunch, and then we headed out.

The plug was not dead -- yet -- but it was intermittent.

How many hours could have been spent troubleshooting that? I dunno, but I paid for a spark plug and an hour of shop time and suffered zero delay.

On another plane, wiithout an engine monitor, I had an "event" which trashed three cylinders. (For the sake of clarity, I was running ROP at the time.) All I felt was a rumble, but I couldn't diagnose it. Not a big deal, just a vibration. If I had been able to glance at a monitor, I would have known it was serious and could have shut that one down, or landed.

Cost? Three weeks grounded, and about $4,000. I was actually lucky. It could have resulted in the loss of the engine.

As always, it depends on the needs, the use, and the disposition of the pilot/owner. I use my planes for transporation, over mountains, at night, in solid IFR. (Not all three at the same time, though!) Downtime is a really big deal. For me, the engine monitor, and the knowledge of how to get the most out of it, gives me additional comfort, and it saves me money and time.

For others, that equation might not be the same.

[Walter Atkinson]

Kyle:

The study was done by American Airlines and the result was a TBO extension from 800 hours to 3600 hours, by doing nothing more than stopping running the engines ROP and making sure they were all run LOP. The data was so compelling that Wright Aircraft requested the use of the data to compile, publish, and distribute a booklet on engine management entitled, "Basic Theory of Operation of the Turbo-compound Engine." It was given to every flight engineer and the methods were followed to the letter. It became known as the WAD Manual (Wright Aeronautical Division) and can be purchased from Fly Bye Knight Press.

It is an eye-openning, informative read.

[WebMaster]

WHICH INSTRUMENT
I have been following this thread, and the LOP discussion, and I see a lot of reference to JPI engine monitors. This raises a question with me. Is there a clear advantage to the JPI analyzer over the GEM analyzer, or even the Vision Micro VM1000. In fact, couldn't you completely replace the steam gages with the VM1000 panel? Would it do the job that the JPI instrument does?

Thanks.