need a good radial guy

[svcta]

I've been sort of unhappy with my regular 'guru' as of late. Can anyone steer me toward a good radial man around Ga. or Al.? R-1340 on a T-6 that finally has me convinced that it needs some attention.

In the last few times that I've flow it I've allowed some less than stellar performance off the ground because of the 3 digit temperatures, but today I noticed in the t/o climb that the RPM had come off about 75 revs. I always verify proper power settings when I push the throttle up on the roll, but as the gear hit the well it was clear that it ain't as happy as I would like it to be.

Anyone got some thoughts?

 

[bugchaser]

How many hrs on the engine? Have you had the valves adjusted at any time? There could be many possible reasons for this. How did the engine sound? Any problems with excessive mag drop at run up? I have sat behind these engines for several thousand hours and have seen most problems. Give me some more specifics and I will see if we can troubleshoot it a little more.

 

[bell47]

Was it making good MAP (36 inches) with still some power left over? I would first do as the other poster said and adjust the valves, I would also remove, clean, gap and test all the plugs, I would also time the mags(internal and to the engine). A compression check wouldn't be a bad Idea. You could also do a crayon check to make sure you don't have a dead cylinder. Just some suggestions. How much time is on the engine and who did the last OH? Do you do oil test to see if it is making metal? Is it an AN-1 1340?

 

[svcta]

Thanks for the replies so far.....the valves were adjusted probably 20 hours ago, the engine has less than 200 hours on it..an Aero Engines overhaul that sat for nearly 15 years until we bought it. It has run flawlessly until now and we've put probably 70 hours on it since October(about a year). It threw a little oil and grease for about 10 hours but it has tightened up wonderfully.

Man. Press. is good, all 36 inches with no problem, I tried to get a good static run up before I put it in the hangar yesterday, but the grass wouldn't keep me in one spot and I didn't have the time left in my day to get to a good paved run up area. As I said, I got 2250 RPM on the take off roll but I noticed a small drop and what felt like a very lack luster climb after I got in the air. I flew around the airport for about 15 minutes and ran some different power settings. It seemed as if I could get full RPM at 36" if I pushed against the forward stop of the Propeller knob. One of the others involved in the airplane has felt for a while now like the carb needed to be overhauled and that's our next step.

We had the mags timed about 20 hours ago....RPM loss on mag checks is about 89-90 RPM left mag, and maybe a shade over 100 on the right, which I know is marginal(tell me if I'm wrong). All of this is on the heels of about a 2 week sit, which is never good for old airplanes, but I think it's a little more than an exercise issue. Compression check next is a great idea, I'm gonna get on that for sure...now, is a crayon check what I think it is?

The guy who did the work on the mags and the valves has a historically good rep with round motors, but I'm beginning to lose faith in his technique a little; his work doesn't seem to be as good as it used to. Therefore, I'd like to find someone else to look at it this time.

Thanks for the insights so far...keep 'em coming!

 

[avbug]

If your engine is pulling boost without issues, your mag checks are in line and no roughness, I don't see an engine issue. I see a propeller issue...especially as you're well into the governing range and seeing engine RPM issues. This speaks to the propeller.

 

[svcta]

I've sort of been waiting to hear from you, bug! I like where you are going with this, well, not in terms of dollars but i digress. Can you elaborate at all? Thanks!

 

[avbug]

Some more information is in order. How about the idle RPM checks, and your high and low RPM checks during the runup? When you do your runup on the ground, you should be cycling the propeller to see where the low RPM limit lies...should be about 1200, and you should be seeing at barometric pressure the same standard RPM you always see. Usually the high and low checks are done at barometric pressure, just shy of governing, rather than at a typical runup RPM of 1700 or so...in other word, the power setting for that check is set by manifold pressure, and hasn't pushed into a governing range.

The reason for doing it this way is because at a typical runup power setting, you're not exploring the full operating static RPM range for the propeller. By continuing to apply power to barometric (about thirty inches at sea level, about 25 inches at five thousand feet, etc), you're seeing the max RPM you're going to get static...taking he propeller as fast as it will go before the governor takes over and starts increasing blade angle or interfering with the propeller.

If the RPM is low at this point, you may have an engine that's producing inadequate power. Accompanying this you may or may not have roughness, depending on why the power loss is occuring. Generally a problem isolated to one or two cylinders will produce roughness and vibration.

If you're pulling manifold pressure in the order of 36", then clearly your engine is producing power, and it's being boosted properly. This isn't to say that it doesn't have problems, but if you're pushing the power above barometric, the problem with low RPM must be governng...something is holding the RPM down, and that can only be the propeller. The propeller is restricted by the governor, and the first thing to determine there is if the governor limits have been changed.

A low RPM could be a linkage issue, restricting the governor limit (working the same as the propeller control being retarded). It could be debris in the pilot valve, sludge in the propeller shaft, a physical restriction to the propeller limits, a counterbalance issue (check for loose or shifted counterbalances), a broken speeder spring, a leaking governor assembly, or possibly other problems. But the first step is to see where it's failng to govern properly. If you're seeing a low RPM during the barometric check, and the engine is at barometric pressure, you have a propeller which isn't reaching it's high RPM pitch stops for some reason or other.

I'd also be for checking the individual blades very carefully as part of the preflight, looking for leakage around the hub and blade shank/hub interface, and any play in the blades themselves. Look for one that's different, rather than both blades having play.

I had a five blade hartzel on a turbine installation this summer that turned out to have a problem...it had a very occasional vibration that came and went so infrequently, and lasted for so short a duration, I thought it was my imagination or perhaps an unusual turbulence. It was found during a preflight inspection, and as manifest as a very slight play in one blade. It was immediately grounded, removed and overhauled.

Let us know what you find.

 

[erj-145mech]

The prop doesn't have a pilot valve, its a Ham Std 12D40, counterweight type.
In this case I would check the counterweight bearings. They are somewhat exposed and if the counterweights are binding up at all, you won't make full blade travel to low pitch (high RPM).
Avbug is right, it sounds like a prop issue vs basic powerplant.

 

[svcta]

Bug,
that's some great info. I'll make this check in the next few days as soon as I can get to the plane. I've noticed no excessive grease on the blades and I always pull a few blades by hand before I crank...I haven't noticed any play, but I'll pay more attention next time.

I will certainly let you all know what I find.

Now, for a very simple question: What kind of mag drop do you look for on a 1340? We typically see 75-100, and I've always accepted that as well within what I would consider to be normal, but what makes me curious is the military maintenance manual.....it calls for 50 RPM.

 

[svcta]

erj-145,
I just posted after you hit the button, it's funny but I was just discussing greasing those bearings with one of the other guys...back to the original Mx manual, it was called for after every flight. So that will be the first thing I do before the next running.

 

[avbug]

Be careful what grease you use; don't mix greases, and don't overgrease.

Prop governor without a pilot valve? I haven't opened the propeller in question, but all the woodward (and other) governors I've dealt with that controlled ham standard props used a shaft and pilot valve.

The propeller uses counterweights, which is why I said check them...but the counterweights are there to balance against aerodynamic twisting force, the make it easier for oil to do it's job on the prop. That oil is routed by the govrnor, which uses flyweights moving a pilot valve against a speeder spring, which is in turn compressed by the pilot using the propeller control.

 

[svcta]

So for the update....

Here's where I am: I've got a low RPM limit (at barometric pressure as you described) of 1125. I was able to adjust the high RPM stop on the governor to achieve the 2250 with minor adjustments both there and at the throttle quadrant to assure proper clearance of hardware there. So that problem is fixed and I flew the airplane for about an hour today and it ran flawlessly again. What are your thoughts on the low RPM limit? Is that number acceptable in your opinion? The low RPM limit can only be manipulated by changing the geometry of the pushrods and control arms involved(there's not an adjustable stop on the governor), which will turn in to one of those day-long-in-and-out-of-the airplane-cranking-and-shutting-down over and over kind of jobs. What are your thoughts on the 1125 RPM that I've got?

Question for ERJ-145(or anyone else, of course): The covers over the counterweight bearings
or how to get to the covers off, really. There is a clevis pin with a cotter pin acting as a safety on the cover. When the cotter pin is removed the clevis pin just slides right out and then what? I grappled with that thing for a half an hour before deciding that it must not thread off the way I had assumed. They're knurled around the circumference so I assumed that they thread on/off. Both were impossible to move with what I consider to be 'reasonable' force. What's the trick to getting those covers off?


Thanks so much for all the advice so far, the steers have been dead on thus far.

Still looking for a good radial guy to keep in the rolodex in the southeast. Anyone have some names?

 

[avbug]

If I undersand correctly there are no power issues and there's no vibration, and your RPM has been recovered by the methods you described. Sounds like there's no more problem.

Low RPM limits sound find. I wouldn't mess with them. Sounds like it's riding on the high pitch stops, and that's all you can ask. Ballpark number at barometric ought to be about twelve hundred; your number is good. remember that the RPM gauge is generally wrong anyway...not much in the cockpit ever gives you more than aproximate information anyway. (Much as we'd all like to believe, anyway).

I'd leave the counterbalances alone. Lube and grease as required, but if you had a single balance weight issue, you'd have RPM fluctuations and vibration.

Are you seeing the performance you normally expect in flight, now?

 

[svcta]

Thanks for the opinion on that....leaving it alone at this point seemed like the best course of action to me, too. The numbers are back where they need to be and it's running great. In flight and off the ground it seems to be right where it should be, so I think we're done here.

Re: the counterweight bearings, the military Mx manual calls for grease after every flight. Therefore those covers I asked about must(one would think) be easy to remove(and they are supposed to be for proper distribution of the grease), but I can't seem to get them to budge. I'm just curious if there's something that I don't know about them. I was able to get grease in through the slots in the back side of the assembly, but it says to do it from the other side.

 

[bell47]

another prop trick..... we used to turn the prop verticle and pour STP oil treatment around base of the blade where it goes into the hub. leave overnight and it will run all the way through. You need to wipe off the excess( a rag with av gas works well) , then grease your hub and weights. As the STP goes through the hub it really seems to flush out dirt and other stuff in there. Be sure to place a drip pan under the bottom blade! Seems to make it really smooth.

 

[avbug]

What this generally does is lube the outside of the doughnut seals...doesn't go right through the hub. Some operators use motor oil too, and the main function is to slightly swell the seals to help prevent leakage. We used to do it on an Ag Cat, too. However, I'm not convinced it actually does anything.

If it's going through your hub, you have serious problems.

Were you meaning to say it flowed through a spinner, instead?

 

[bell47]

Avbug, No I meant hub. When you pour the STP down the top blade it will run through the hub and leake through to the bottom blade. Now I'm not sure what it does or where it goes in the hub but it seems to lube it nicely and tends to flush out dust particles. I assume we're talking the same prop, I'm talking about the counterweighted props that you have to grease the counter weights and hub. I've done this on probably 5-7 different props over the years and they all dribble through. Also helps during run up to cycle prop a bunch after doing this and the clean the windshield before you fly it, as the STP really slings everywhere.

 

[bugchaser]

I have also seen the STP trick done in the past. I too am not sure about the results. One thing for sure is that is will make a mess all over the airplane. We also had a wooden prop "wrench" that fit over the blade so that one could twist the prop back and forth. We would do this after greasing on particularly sticky props. You mentioned something about getting the covers off to apply grease. Do you not have any grease fittings? There is also a product that clamps over the prop blades and supposedly forces grease into the hub. I think that is was called a King greaser or something like that. Again, the only result I ever saw from that was a big mess all over the airplane. On a side note, do you guys run the engine up prior to shutdown and pull the prop back. This protects the prop cylinder as well as having the prop control in the proper position for starting a counterweight prop. Of course all of this could be avoided with the installation of a hydromatic propeller.

 

[Frozen Ronin]

Wow, be careful loading up a hub with STP or MM oil. It acts as a great cleaner and lubricant, but will continue to clean even after you re-grease the hub if it doesn't all get out. That leaves you with rapidly spinning parts without proper lubrication.

We use the 1340 on the single Otter, not sure if the prop set up is the same. Doubtful. But I haven't seen sticking issues in service up here.

So much to learn!

As far as a great Radial guy in GA, have you checked with any of the Yak or CJ guys? There are several in Atlanta (Delta guys), and they might have a lead on a round motor mechanic.

Love to help you, but the run to AK might be a little expensive!

Ronin