LAME & borescoping

[QFF]

Does anyone know of a LAME in WA who even owns a borescope, let alone uses it regularly enough to know what they're looking at?

While we're at it, would it be possible that person is able to interpret engine monitor data? Broadening the net to the include the Eastern states?

I guess it would be nearly impossible to find one who fits all the above AND endorses LOP ops...

Thanks for any leads...

[Jabawocky]

Dont have a boroscope, but after 190 hrs and LOP ops our leakdowns and general health are excellent. The plug and piston cleanliness are both excellent.:)

[ForkTailedDrKiller]

I have yet to find a LAME who endorses LOP ops!

Dr :8

[Jabawocky]

Ya not looking hard enough Dr:cool:

[Hasherucf]

Well I own a Borescope , several infact, which I use weekly but dont endorse LOP. Quoting an old tech school lecturer 'LOP is the domain of old men and aeroclubs' ;-)

[ForkTailedDrKiller]

If you look at the various TCM engine operating manuals, you'll find that TCM specifically authorizes 50F LOP operation for their IO-550 engines.

But what would they know?

Dr :8

[Jabawocky]

Quoting an old tech school lecturer 'LOP is the domain of old men and aeroclubs' ;-)probably a good reason for that, those old men KNEW how to operate an engine. The SOP's for many airlines running big piston engines was precisely LOP and those things ran many thousands of hours between overhaul.

Too many old wives tales. There is such a thing as too lean, and its exactly the same place as too rich as well.

J:ok:

[ForkTailedDrKiller]

tool lean?

How does that compare with "tool fat"?

Dr :8

[Peter Fanelli]

How about a crazy FTDK with an endoscope and if you refuse to cooperate and electroejaculator!

[Led Zep]

All bolding my own. Word for word from the POH issued September 14 1979.

Section 4 "Normal Procedures"
4.37 Leaning Procedures

When leaning below best power is permitted (refer to Maximum Manifold Pressure Vs. Altitude graph in Section 5 - Performance), the engines may be operated at peak EGT or on the lean side of peak EGT as long as stable engine operation results without exceeding any engine limitations during steady state or transient conditions.

BEST POWER
To lean the mixture to best power, proceed as follows:
(a) Lean the mixture slowly until EGT has stabilized at peak.
NOTE Do not exceed 1650F EGT.
(b) Enrich the mixture 125F.
(c) At high power setting if 1650F is reached before peak EGT, refer to Lycoming Operator's manual for correct procedure.

BEST ECONOMY
To lean the mixture to best economy, proceed as follows:
(a) Lean the mixture slowly until EGT has stabilized at peak.
NOTE do not exceed 1650F.

LEAN SIDE OF PEAK
To lean the mixture on the lean side of peak, proceed as follows:
(a) At the desired power setting, lean the mixture slowly until EGT has stabilized at peak.
NOTE do not exceed 1650F EGT.
(b) If peak EGT is 1650F of less, continue to lean until a maximum of 50F reduction in EGT is obtained. Readjust manifold pressure as necessary to maintain desired power setting.
(c) If 1650F is reached before peak EGT is obtained, lean according to the following procedure:

(1) With mixture leaned to 1650F, reduce manifold pressure until EGT is reduced approximately 75F.
(2) Lean the mixture slowly until 1650F is obtained.
(3) Lean the mixture additionally until 50F-100F on the lean side of peak is obtained. Do not lean into engine roughness.
(4) Slowly increase manifold pressure to the desired power setting without permitting EGT to exceed 1650F.
(5) Carefully adjust the mixture until EGT is 1625F to 1650F.
NOTE Enriching the mixture will increase the EGT when operating on the lean side of peak EGT.
(6) Before enriching the mixture, reduce the manifold pressure as in step (1) to prevent exceeding 1650F EGT.

[QFF]

It's a serious question, guys. I am convinced that LOP ops are the way to go - the caveat is you need a multi-cylinder engine monitor. I've been using one for a few years now and have done the APS course and am thoroughly convinced of the benefits.

It'd be nice, though, to be able to run through some of the engine log file data with a LAME who would be able to help diagnose, for example, ignition issues from an inflight high power LOP mag check. Is there someone at Jandakot that might who's lurking under the radar?

And progressive enough to consider borescopy as actually yielding useful information rather than relying on compressions alone to judge cylinder health? In the good old days they relied on doing serial ECGs to dianose heart disease - these days they stick a catheter & look directly at the source of the problem.

We need to keep up with the times and not just continue doing what we were taught to do just because "it's worked fine for us - why change?"

[ForkTailedDrKiller]

It'd be nice, though, to be able to run through some of the engine log file data with a LAME who would be able to help diagnose, for example, ignition issues from an inflight high power LOP mag check

My LAME was not a fan of all-cylinder engine monitors (which I think should be mandatory) until I walked in one afternoon and asked him to look at the "bottom plug on #4 cylinder" - sure enough there was a bit of crud on it.

He does, however, have a borescope - and uses it!

Dr :8

[Old Akro]

I'm not a LAME, but I own a borescope (fibrescope actually) which I have used with my LAME who doesn't own one. The thing about borescope's is that they are a bit like looking for something in a room through a keyhole. It requires a fair bit of experience to interpret the results. It will also only show some of the potential malady's. It will show chronic piston problems. It will show scored bores, but it requires skill to tell a streak of oil from a score. Depending on the borescope, you might be able to look back at the valves where it will show a burnt valve, but not valve seat problems.

The best diagnosis of an engine is still probably comps & flying the aeroplane enough to become attuned to its vibrations & character.

Cylinder head temps are nearly more important than EGT's, yet don't receive much attention. Its CHT issues that will cause cylinder issues & valve seat problems through overheating or shock cooling.

The master guideline on mixture settings is the engine operator's handbook. You need to own one for your engine and be familiar with it before entering into the LOP debate. The engine operators manuals frequently say quite different things than you'll find trotted out as "rules"around the aero club bar. The engine manufacturers test run more engines with more instrumentation than anyone else. Many of them endorse LOP below 65% power. But it varies with engine, engine installation & power condition. Read the engine operators manual for your engine. You might be surprised.

[QFF]

The best diagnosis of an engine is still probably comps & flying the aeroplane enough to become attuned to its vibrations & character.

My TCM engine is covered by this SB (http://www.tcmlink.com/pdf2/SB03-3.pdf) that says you need a master orifice tool to calibrate your compression tester, and if your compressions fall below the limit set by the master orifice (40/80) then you have to do a borescope to internally inspect for the cause of leakage. The SB is a must-read, even gives pretty pictures to show what to look for!

I would want to do a regular inspection anyway, just to see - as you say - if any chronic problems are evident. Wouldn't anyone, if the technology was available?

My problem is still to find someone with the equipment to be able to fullly carry out TCM SB03-3 which says "The purpose of the cylinder borescope inspection is to provide a visual method of examining the internal cylinder components and must be used in conjunction with the differential pressure test." By inference, does that means that perhaps we aren't maintaining our aircraft according to the manufacturer's recommendations etc.?

We are encouraged to operate by the advice given in engine manufacturer's manual, yet conveniently pick & choose which bits of maintenance advice from the same manufacturer we adhere to (check compressions) & ignore (borescopy)?

Cylinder head temps are nearly more important than EGT's, yet don't receive much attention. Its CHT issues that will cause cylinder issues & valve seat problems through overheating or shock cooling.

Agreed - hence the proposition (probably even fact) that CHTs are lower when running LOP than running at 25-50deg ROP as recommended by Some Engine & Aircraft Manufacturers! May I add also that apart from overheating issues (esp if CHTs > 425degF), the main issue is that CHTs are a surrogate marker for ICP - internal cylinder pressure, which is what causes cylinders to fail & self-destruct. It is interesting to note that the ICP curve follows the CHT curve i.e. tends to lessen the leaner you go. So LOP actually reduces CHTs and ICPs - all good things for cylinder longevity.

[PA39]

Gee the old lop OR rop argument (debate)...... read the FM,POH or Lyc or Cont, recommendations. pretty simple. They both have operating instructions on the net. Personally.....and it is only just that, i have run all of my aircraft ROP.......never a crack or burnt valve and always went to TBO. Fuel is cheaper than cylinders etc

[QFF]

Gee the old lop OR rop argument (debate)...... read the FM,POH or Lyc or Cont, recommendations. pretty simple.

Not really interested in rehashing the old debate.

Just wanting to find a LAME with a borescope! (Read TCM SB03-3 - pretty simple, too!) Preferably in WA!

Ideally with an ability to interpret engine monitor data!

(An open mind to LOP operations a bonus :ok:)

[Jabawocky]

OWEN

We can talk about this later at some point

PA39.......mate maybe you can sneek over the bay to YCAB on day and come for a ride...I'll happily show you how a fuel saving = a full overhaul:eek:

And QFF.......all cylinder monitors and using LOp helps you find problems.....plugs the LAME would have said were fine recently, but LOP were not, and easily found with all cylinder monitoring.

And Forkie's story above is not unique.:ok:

[avcraft]

GAMI Injectors + monitor + LOP = :ok: a set of finewire plugs will help as well :)

Read TCM SB03-3, www.tcmlink.com/pdf2/SB03-3.pdf

If your LAME doesn't have a borescope suggest he buy one and actually use it or go elsewhere...

[Old Akro]

QFF. This may not be helping a lot, but if you're below 40/80 the pot is most likely coming off regardless of what the borescope says. I've replaced a few TCM pots recently and predominantly the problem has been with the valve face. I have not seen anything on discussion boards, but the valve's I've seen look like a valve manufacturing problem.

There are only 2 causes of low comps. 1. leaking through the valves and 2. leaking through the rings (unless there is a hole in the side of the cylinder). A wet comp test will give an indication of whether its rings or valves.

If its the valves it could be a) valve seat insert problem, b) valve face problem, c) valve spring problem or d) burnt valve e) valve guide issue. The borescope will pick the burnt valve only. Many borescopes will not look back enough to see the valves anyway.

If its the rings it could be broken rings, worn / lost tension rings, scored cylinder, burnt piston, or possibly the cylinder going out of round. I've looked at a number of cylinders with my fibrescope and I think it takes talent to pick oil lines & smears from scores and the pistons are so uneven in colour that I think you'd need a big lump of piston missing to really pick it.

You can hire borescopes from places like Tech rentals, but I suspect that whatever the result, the pot will end up coming off. At 40/80 or below, that cylinder is not doing much work and needs some sort of remedial action. Whatever is causing the low compression is only going to deteriorate at an accelerating rate.

Probably your only ray of hope is if the ring gaps all happen to be lined up. Piston rings rotate in service (there is controversy about how fast, but it is universally accepted that they do rotate). It might be worth giving the engine a good ground run & repeating the compression test with the engine warm & the bores nicely lubricated.

If you are really determined to do the borescope thing and can't find a LAME with one, I'd find a local race engine builder & pay him to go to the airport & look in the cylinder. The advantage of the race guys is that they tend to get the same engines back for regular rebuilds, so tend to pay more attention to the feedback of how they wear, whereas the general mechanics / re builders are reconditioning an engine to fix a problem and usually never see it again.

Something for the LOP skeptics. Most aircraft engines run 7.5:1 to 8.5:1 compressions with conservative valve timing, conservative park timing with no spark advance mechanism and at low RPM. Most engines were designed for 80 octane fuel but are running 100 Octane. A car engine will happily run (say) 12:1 compression, with twice the spark advance on lower octane rated fuel often with higher charge temperatures without detonation. Why are we so paranoid about detonation? Especially when the major reason for an engine not reaching TBO is heat / cooling related cylinder issues, valve issues, camshaft & valvetrain wear, crankcase cracks, etc.