Can engine adjustments be made as an owner/operator?

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DMartin

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DMartin
The aircraft in question is a turbocharged light piston twin which after a propeller governor replacement is 200 RPM short of what is expected at full takeoff power. Obviously the A&P who installed the governor did not properly adjust it or check his work, but for reasons beyond my control the airplane is no longer nearby this original mechanic. The airplane is now somewhat stuck at a different airport, where the on field mechanic says they are booked into September and won't even open the cowling until then. I would prefer not to fly it to another mechanic because, being turbocharged, this reduction in RPM has also reduced manifold pressure and I am worried about the engine being deceptively low on power.

So the question is simple: can I make an adjustment to the propeller governor stop under 43.3? Appendix A seems to indicate that I cannot, however the Coleal letter interpretation explicitly states that the list in Appendix A is not exhaustive. In an effort to make this question relatable to others I thought I would broaden the scope to include other engine adjustments (like carburetor idle mixture, idle speed, etc). In my opinion, those adjustments should fall into the same category. I.e. if I can make a governor adjustment, I can also make an idle speed adjustment, or both would be prohibited together. After reviewing the regulations, it seems to me that the answer to this question depends on whether or not the adjustment is considered to "involve complex assembly operations". Thoughts?

For what it's worth my gut tells me this is not something the FAA intended to be included as preventive maintenance but another pilot friend suggested the idea and I didn't have a regulation to point him to that said no
 
AS far as US law, someone else will comment, but in Canada that isn't an owner-maintenance item.

And there are reasons it's not owner-maintenance. For one thing, not all installations will reach redline at full throttle while the airplane is sitting still. The low-pitch stops in the prop are preventing it, not the governor. If you adjust the governor to get redline, you might find you can't get it. Or you end up well over redline in the climb. That ain't good.

Another reason? Tachometers age, and they under-read as the magnet in them gets weaker. If you are relying on the airplane's tach, beware. Again, in Canada, the typical magnetic-drag tach has to be checked for accuracy every year, and if it's within 4% at cruise RPM it can be placarded as to the error. Over 4% and it has to be replaced. The US has no such law, and under-reading tachs will be everywhere. In the twin, it's less likely but still possible.

Mechanics, at least most of them, know about static RPM limits and old tachometers. Owners typically don't. You can't rightly say "obviously the A&P didn't properly adjust it or check his work." One must know the details to make judgements. It is possible he was careless, but there is so much that owners just don't know.
 
Are you saying that at take off power, one engine is at, say, 2700rpm and the other is at 2500? Does the plane turn towards the low rpm engine? Is the fuel flow to the low rpm engine lower? If so, it is likely a governor adjustment. (Although checking the rpm with a handheld tach is a good idea. Thery're pretty inexpensive.) As you probably know, the high rpm setting is just an adjusting screw and locknut. I doubt the FAA would say it's something a non-A&P could do. On the other hand....
 
Mobile A&P an option?
 
This is not an owner adjustment. Further, the mention of low manifold pressure would concern me, and it may require investigation as well. Get someone who knows the systems to take a look at it.
 
Lance F said:
Are you saying that at take off power, one engine is at, say, 2700rpm and the other is at 2500? Does the plane turn towards the low rpm engine? Is the fuel flow to the low rpm engine lower? If so, it is likely a governor adjustment. (Although checking the rpm with a handheld tach is a good idea. Thery're pretty inexpensive.) As you probably know, the high rpm setting is just an adjusting screw and locknut. I doubt the FAA would say it's something a non-A&P could do. On the other hand....
Click to expand...

Exactly right. Yes the other is 2700, yes the airplane turns that direction (though the previous pilot set the rudder trim to accommodate), yes the fuel flow is lower on that side. I'm fully aware of old airplane tachometers and the limits for setting propeller RPM's. On top of this the engine was making full RPM/Power before the governor change. I work on many of our airplanes under supervision of our A&P/IA when they are able to be brought to his location for maintenance. Though I understand where these comments are coming from, the work itself is not the issue. We will find a solution one way or another, but this was just a question I didn't have an answer to so I am using it as a learning experience. Quite honestly I'm sure I could make the adjustment, not log it, and the FAA would never know the difference. But i'm not really interested in breaking the rules just for convenience and this is technically above and beyond my job description anyways...but it would be nice to keep things moving if I find that it is allowable.
 
Will the on-field A&P let you do the work and he just review the final RPM and sign-off on the work?
 
mondtster said:
This is not an owner adjustment. Further, the mention of low manifold pressure would concern me, and it may require investigation as well. Get someone who knows the systems to take a look at it.
Click to expand...

I am certainly not ignorant to there potentially being more issues than just a governor adjustment, but it seems a likely place to start given the recent work to the airplane. Whether that be myself or an A&P the result will at least initially end up the same. Thank you for your input

thito01 said:
Will the on-field A&P let you do the work and he just review the final RPM and sign-off on the work?
Click to expand...

Nope. I offered this suggestion to them but they quickly declined. Really not the most friendly folks I've ever dealt with, but I didn't create this post to bash a shop who I only have limited experience with. I will say that in addition to the airplane in question we operate a relatively small, but growing number of Cessna 300/400 series aircraft all over the contiguous U.S. and the GA mechanic shortage we have been experiencing is concerning. Just last year this airport had 3 GA shops, and now it's down to one. Not for lack of work but due to lack of mechanics.
 
Find an A&P that will. I made the adjustment on my prop governor. It was the onerous task of turning a screw 1/4 turn. I also replaced the vernatherm yesterday. Showed my A&P the safety wire job by snapping a picture. He asked for me to text him a tach time so he can put it in the logbook.
 
Sounds like everyone is in agreement that this is NOT something that would be allowed under 43.3 as Preventive Maintenance. That confirms my initial suspicion. It's probably smart to assume that other similar adjustments like idle speed, idle mixture, fuel flow, etc. would also be disallowed. I'll continue the search for an A&P to come work on this where it's at but I do appreciate the responses.
 
Please tell us you’re not using the tach to set the redline……o_O
 
DMartin said:
The aircraft in question is a turbocharged light piston twin which after a propeller governor replacement is 200 RPM short of what is expected at full takeoff power. Obviously the A&P who installed the governor did not properly adjust it or check his work, but for reasons beyond my control the airplane is no longer nearby this original mechanic. The airplane is now somewhat stuck at a different airport, where the on field mechanic says they are booked into September and won't even open the cowling until then. I would prefer not to fly it to another mechanic because, being turbocharged, this reduction in RPM has also reduced manifold pressure and I am worried about the engine being deceptively low on power.

So the question is simple: can I make an adjustment to the propeller governor stop under 43.3? Appendix A seems to indicate that I cannot, however the Coleal letter interpretation explicitly states that the list in Appendix A is not exhaustive. In an effort to make this question relatable to others I thought I would broaden the scope to include other engine adjustments (like carburetor idle mixture, idle speed, etc). In my opinion, those adjustments should fall into the same category. I.e. if I can make a governor adjustment, I can also make an idle speed adjustment, or both would be prohibited together. After reviewing the regulations, it seems to me that the answer to this question depends on whether or not the adjustment is considered to "involve complex assembly operations". Thoughts?

For what it's worth my gut tells me this is not something the FAA intended to be included as preventive maintenance but another pilot friend suggested the idea and I didn't have a regulation to point him to that said no
Click to expand...

...
 
You can have surgery and the surgeon can be in another room or another country.

Some airlines have used remote monitoring to determine engine condition.

Perhaps we should apply some of this technology to GA.

We can easily get video and audio.

Do we really need taste and smell?

Currently the CFR/FAR do not seem to support this.

Maybe change the reg?
 
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