Maintenance and Pilots on the ball.

[Jabawocky]

THIS IS NOT A LAME BASH THREAD - DO NOT EVEN THINK ABOUT IT :=

HOW MANY AIRCRAFT OWNERS TAKE AN ACTIVE INTEREST IN THE TECHNICAL RESULTS OF MAINTENANCE ON THEIR PLANE?

I thought I would start this thread to raise awareness of what you the pilot can do to better look after your aircraft and ensure it is configured in an optimal state.

Topics should be typically engine related although airframe and avionics can be discussed, so I will suggest things like plugs, magneto's fuel flow etc.

To kick off, lets look at a very smart guy, who randomly visits this forum and has a large pressurised twin. Turbocharged engines. This aircraft is maintained by a very good shop and has recently come out of annual. The plane does typically 12-13 hours a month or more. The aircraft is fitted with a good EMS setup and the pilot has been educated very well on understanding exactly what the EMS is telling him. No dog watching TV here!

Engine A is showing signs of lower TIT and higher CHT's and can not flow the typical LOP fuel flows without busting 380-385dF and has to be run around 20-30dF further LOP.

Engine B is not showing these symptoms, rather it seems not to be as smooth when LOP. The GAMI spread is still perfect however. The TIT is a bit higher and during an inflight mag check there is a bit more variation in the EGT bars.

What was found? Engine A had both mags timed with 1 degree too much advance, plugs were all fine. Engine B had several plugs with a gap beyond 0.018" and the mags were 2-2.4 degrees retarded. It should be noted this engine was also easier to start, and that makes sense too, the pilot noted this.

How many pilots out there would be this sharp? My guess is 1% at best.

This was not long out of an annual so the obvious question is how on earth is this possible? the answer is simple. Most LAME's do the best they can with the little they have. Many are still using the old timing gear marks under the brass plug or the hole/flywheel method. We used a Rite System kit.

Why is this important? Well on a TC engine 1 degree of timing really does make a big difference. With the digital Rite System you can pick and adjust in 0.1 degree increments, and a full degree is hard to pick using the old factory markings. So if the LAME is a bit slack or in a hurry or whatever, he can say "it's within tolerance" and think it is fine. But add another degree or two and it is not fine and may be very bad.

If you or your LAME do not have one, buy one and gift it to him/her. :ok:

Plugs.....If they are fine wires and tempest, not much to do, if Champion check their resistance. If they are massive electrode buy your self some gapping tools and every 50 hours clean and gap them. 0.016" to 0.018" is the range, set them at the lower end and recap at 50 hours. When they get to 20-22 thou they are not performing right.

I am sure there are plenty of stories that can be shared, so feel free to share or ask questions if you wish. I will do my best to answer them, or others here will for sure. There are some LAME's here that might have to help me out too.

Remember this is not a LAME slag fest. I will ask Taily to keep an eye on that. I want this thread to be all about learning and positive things.

I am out bush for the weekend so I may not be back to this till Monday, so play nice y'all. :ok:

[PLovett]

Given that the aircraft owner is now the authorising person for the maintenance perhaps it is time that aircraft owners took a very keen interest in their aircraft and not just their wallet.

[Jabawocky]

You have stolen my post for post #27 :-)

Cocky frog to you!

[Band a Lot]

Rather than gap massive every 50 hrs, I would recommend replace with Champion fine wire plugs. Massive only last 3-400 hrs before they would fail wear limits and they seem to have about doubled in price in a few years.(more than exchange rate change anyway)

That indicator behind the brass plug is not allowed to be used for timing any more due mandatory bulletin.

Been a few contact points funny wear in recent years on both Bendix and Slick recently, this normally a few hours after 500 hr inspection or O/H.

Cleaning inside where HT lead goes is often missed and can make a big difference in resistance.

[QFF]

Digital Rite system - a digital protractor taped to a prop would achieve the same result. Although would still need a TDC locator plug.

[nomorecatering]

Why are we even using conventional mags in 2016 when there are electronic mags with STC's available.

[Ultralights]

was thinking the same thing.... Magnetos, why arnt they in a museum yet..

[Band a Lot]

I prefer the saying why are we still flying piston engines.

Mostly cost, the STC mags are about 10% extra of a overhaul cost around 5K (at end of day).
Also about zero support in maintenance and parts.

The new Connies with extended TBO don't come with STC mags as option and the extra hours are better bang for buck than STC mags.

In Oz as soon as one of these companies goes broke product support is gone - so then is your use of them in OZ. But other reasons also, like mags actually do work fine very often.

[Horatio Leafblower]

Cocky frog to you!

....if that's your thing...

[PLovett]

I knew what he meant. :)

[Jabawocky]

Pharqueing MAC auto spelling. CHOCKY Frog that is. :-)

[The name is Porter]

At first I thought this was a LAME bashing thread, but it's not, so I've got nothing to say........

[gerry111]

Where's yr right? :oh:

[advo-cate]

Maybe his intolerance for "" is keeping him out of this.

[Lumps]

Would the commonly available apps available for iPhone do for digital protractor? Seriously

wouldve thought technology is the same or better than the time rite stuff

I feel this thread should provide fertile ground for observations of the Waddington Effect

[Sunfish]

CASA does not understand the Waddington effect, hence overhauls of perfectly good propellers at an arbitrary interval without any supporting evidence and of course replacement of control cables, etc.

I ran head on into the Waddington effect about 1978 - F27 AP gyros.

[Jabawocky]

Lumps, I would expect they would but you still need the in plug hole tool and a buzz box, and the cone/holder that fits the spinner......might as well buy one :-)

[PLovett]

Thanks for the reference to Waddington effect Lumps. I hadn't heard of it but it makes interesting reading. It sort of reflects my own experience that the time one had to be most careful of an aircraft failing you was when it was just out of maintenance.

[Squawk7700]

CASA overhauls of perfectly good propellers at an arbitrary interval without any supporting evidence

If it was perfectly good, there would be no need for an overhaul. Presumably someone in this world, somewhere, has had a failure of this model of propellor and therefore they have taken action so as to protect users of that product.

[Band a Lot]

Squawk I think this a more accurate statement as CASA have used a blanket approach.

Presumably someone in this world, somewhere, has had a failure of a propeller!

[Progressive]

Actually the CASA SDR data shows that there have been many propeller failures - mostly caused by maintenance faults after overhaul!
Luckily a few canny people were able to show CASA the error of thier ways and the proposed ammendment to AD/Prop/1 died where it started.

[Lead Balloon]

Like CVD, CASA will resurrect the prop AD at an opportune moment.

[Sunfish]

Squawk, the error comes from assuming that the propeller failure is due to time in service and not number of revolutions / hours flown / duty cycle / environment / engine management practices / number of starts / etc.

If there was a graph that demonstrated that failure rate per 100hours was directly proportional to age then you might have something, otherwise you don't have anything and may actually be increasing the failure rate by fiddling with something that is working perfectly well.

I spent hours and hours painstakingly collecting data and graphing all this stuff pre personal computer. Hard time maintenance intervals is a blunt instrument for preventing failure in service in most cases. Best thing to do is design stuff that fails gracefully, slowly and visibly, admittedly perhaps not easy to do with a propeller hub.

[Jabawocky]

Actually the CASA SDR data shows that there have been many propeller failures - mostly caused by maintenance faults after overhaul!
Luckily a few canny people were able to show CASA the error of thier ways and the proposed ammendment to AD/Prop/1 died where it started.

That was an interesting project Mr Progressive :ok: I must thank you for your help on that, it was outstanding :D

Pb, if they try it again you can be sure at least three of us will kill it off just as quick....actually quicker, we have all their data to use against them at will. ;)

[Lead Balloon]

Given that CASA produced the thought bubble without an objective analysis of its own data in the first place, I hope your optimism is justified. (And more power to Mr P's arm and everyone else who called BS on the first attempt. Unfortunately, no amount of data deterred CASA from reinstating the BS periodic instrument calibration check requirements.)

[Jabawocky]

For the engine nerds among you.

Pilot had the bugs fixed properly and sent in this video. If Carl Goblet was able to get youtube in the after life he would be a very happy man :ok:

35" 2450 and 60+dF LOP. And running smooth.

Enjoy ;)

5xHljV175jg&feature=youtu.be

[Lead Balloon]

I can smell the cookd clys and burnt valvs from hear! (Where's yr right when we need him?)

[Eddie Dean]

Yr Right probably lost interest in puerile arguments.
It appears that posters here believe props shouldn't be overhauled until they fail???

[Lead Balloon]

Arguments based on an objective assessment of valid data and risk are not "puerile", except for those who can't stand their superstition-based beliefs being challenged.

"Puerile" is suggesting that those of us whose lives depend on propellors are advocating that we just fly them until they fail.

Pointing out what an objective assessment of the data shows will increase the risk of propellor problems actually contributes to safety. That assessment results in a strategy for reducing the risk of problems and failures by not having arbitrary time-based mandatory meddling.

You're not from CASA by any chance? Or make money out of propellor overhauls?

[Eddie Dean]

Lighten up leady
Drive your prop till its destroyed. Doesn't concern me.
Probably both CASA and prop overhaul shop owner for all you know.
BTW your post #27 epitomises puerile

[Lead Balloon]

I'll take that as a 'yes'. :ok:

[olm8tyrone]

Eddie & Yr Right sitting in a tree... :ok:

[Eddie Dean]

That's right Tyrone. Bugs you does it or did you just come on to show how puerile you are

[Eddie Dean]

So back to Dave's original question,
Do we trust the mechanics or not?

Also sorry Dave, probably can't attend the course.

[Jabawocky]

Eddie and Yr right are not one and the same, trust me.

But for Eddie's benefit, the prop issue relates to an AD requiring props to be overhauled at a defined time which on a charter plane would not be a problem, because it would do the hours inside that time. But for a private plane doing 200 hours a year or less it was madness.

The data showed there were no such serious issues, and the notion of propellors typically on a dusty old C172 that had not seen a LAME in 20-30 years suddenly becoming compliant with a new AD was childishly naive at best. Those few rogues that were never in the system would not ever become part of the system anyway.

What would happen is plenty of props that were of a certain date would be removed when the manufacturer did not warrant it and the data showed the vast majority of the defects were as a result of being removed and refitted after work was done.

This had nothing to do with routine maintenance at all.

Feel free to give me a ring Eddie :ok: and there will be a class in Adelaide in November (date tbc) if you are up for it mate.

[Eddie Dean]

Thanks Jaba that makes sense now

[youngmic]

A mate was quoted 8k for an overhaul of 2 bladed hartzell with ~500 hours on it but just expired on calendar, second quote for the same thing different shop 4k

Another mate with similar prop new still in box but just out on calendar time 4k to overhaul.

Only time a turbine has failed me in 17 odd years of flying them was due to seized prop bearings creating a Np overspeed resulting in the overspeed governor cutting the fuel flow back so only able to get 30% Tq.

Just months out of overhaul, unfortunately not greased by overhauler or LAME when fitting, not pointing the bone, mistakes happen, just highlighting that human intervention exposes extra risk.

[jas24zzk]

Forgive my ignorance as a dumb panel beater. Aluminium CHUNKS shaped into propellers seems to be below my metalurgical training which includes simple UHS, UHSS, UHSLA, Alloy Composite, Graphite Composite and Boron. Occasionally i get to play with something as complex as mild steel or aluminium sheet.

I am seriously struggling with the concept of overhauling an aluminium fixed pitch propeller.
What is there to overhaul?

Some will say, oh its had stone chips which have been filed etc, we need to correct those. Hang a sec....that nick was filed by a LAME that knows what he is doing! I paid him to do that, and now you say i need to pay to fix his work.....................
All you will get back is a prop that has had even more filed away.

Somewhat cheeky to call it an overhaul when it should only be a NDT...which can be done without removing the prop and introducing another maintenance induced fault.....for which the owner pays..

Damm wish i had that same cash cow in my industry

[Ultralights]

legit question, is the aluminium blade of your average fixed pitch prop on an average GA aircraft solid or hollow?

[Eddie Dean]

Solid aluminium

[Perspective]

Hey Jaba, I think you touched on something worth noting when you say,
Quote: " typically on a dusty old C172 "
I have worked on aircraft that live central Aus, and the dry climate does play a part in the longevity of such, think Arizona. I picked up a 182 from central Aus, not internally primed (typical and maybe a little unique for Australia more so than other places due to saving a couple grand when ordering from the factory in the 70's-80's, but that's another story) and it was like a coke can inside, absolutely pristine, now it lives on the coast any surface not inhibited was quickly corroding.
Jas24, Typically when you file a blade, personally I come from a minimalist point of view, it is difficult to know how much material has been removed, and considering most of the damage is toward the tip where the centrifugal forces are at most play, has the most effect on balance, and will very quickly go out of balance, yes we do dynamically balance props, but sending a fixed pitch to the shop allows them to measure at incremental stages the remaining chord and statically balance also, along with check blade angles etc.
You would think blade angles wouldn't change much but it is not uncommon to find when trouble shooting an imbalance a blade out by more than half a degree at the tip which is significant.
Whilst a blanket change to AD/Prop/1 to Service/Overhaul in accordance with the manufacturers Data (i.e. 6Yr) may seem counter productive at times, I think the incorporation of a geographically guiding covenant would be appropriate.
Ultra, Solid.

[youngmic]

On props and pilot maintenance....

Do whatever it takes to not put chips in the prop in the first place, whilst there is bad luck it is still possible to operate over gravel large and small with a high horsepower engine and low prop clearance and not get significant dings.

Run ups can be brief and on the run into wind, this high power static run up stuff is a little last century.

Wash your prop.

Bug guts can contain acids aside from a range of chemicals likely still unknown to science, dirt contains salts none of which rammed into a porous sand blasted LE at near sonic speeds is going to help prevent internal corrosion. Detergents used for washing it need to be chosen wisely with regard to PH and corrosive qualities. At the risk of making a recommendation CT18 from Chemtec seems pretty good and the fact millions of truck owners swear by might be worth something.

After washing and when dry, really dry, wipe some 50w oil along the LE, it will help seal it and slow the progression of contaminants into the grain structure of the blade.

This tip is not legal, but past to me from an older wiser seaplane driver, use a hard smooth surface instrument, side of leatherman, shaft of a large screw driver etc to rub the rough porous sand (or water) blasted LE this will put a smooth worked finish to the LE. Seems to me this blending of the surface grain leaves the LE a little more tolerant to ingression of contaminants.

Little of the above is relevant to employed pilots as the general rule is turn key and go, maintenance cost are someone else's concern. But aircraft owners who pay there own bills might garner something.

[rutan around]

All excellent advice Youngmic. Here is another prop saving tip that was passed on to me by the operator of a fleet of GA aircraft that operates into many unpaved strips.

Before starting the engine select full coarse on the prop and be careful not to let the engine rev much on start up. With practice you can start without exceeding 1,000 revs. When you want to move off slowly increase the revs till the aircraft is rolling. You will notice that with full coarse selected the aircraft will move off 200 to 300 RPM less than with full fine selected. This achieves 2 things. First it is less inclined to suck rocks into the prop arc and secondly when the odd one does come through the slower moving prop incurs considerably less damage.

The rest is common sense. Many bush strips have a concrete pad for the flying doctor . Use it for your run ups. If one is not available do the mag checks at a fast taxi. On take off start the roll full coarse and once past the speed of a fast jog go to full fine (not TOO fast) and bring up full power. If you forget to go full fine the aircraft will tell you. It wont go any faster than 15 to 20 knots.

If the strip is a real bad one(Light bauxite stones or just graded strips are bad. Ones not touched since the last rain are better as the dry mud glues the stones down to some degree) consider not doing the mag check. What's more dangerous? The unlikely possibility of having to fly on one mag or the high chance of picking up a stone and inflicting unknown damage on the prop. I know this sounds a little complicated when you read it but in practice it is quite simple to do. Once we adopted this method prop damage was greatly reduced and I can't remember when we last had a bad rock chunk taken out of our prop.

[Perspective]

I'd be careful suggesting people skip the mag step altogether rutan, you can check for both ignition systems at any rpm, check it @ 1200 if you must, but at least check it!.

[rutan around]

In practice that's what we do but I make the point that the aircraft will fly quite safely on one mag but shed 6" off one prop blade and:{. I've seen young inexperienced pilots do things that would horrify their boss/LAME. eg parked in loose gravel and sand meticulously doing mag and prop checks sending dust,sand ,stones and tumbleweeds from Blackstone Range or similar place almost to Alice Springs.:=

[Eddie Dean]

Explain further Rootan, I would have thought that at 1000 the RPM would be too low for the CSU to govern

[Lead Balloon]

And tell us what is the risk of taking off, having not tested a CSU's operation at 1,700 RPM.

Pregnancy of all local maidens? Chooks not laying?

What are the problems that the test identifies, and what are the probabilities and consequences of those outcomes, if a CSU fails to reduce in RPM during a 'standard' check?

[rutan around]

Eddie the whole point of the exercise is to keep the prop revs as low as possible to prevent stone damage. You'll quickly discover if the governor is working or not as you add power. Try it one day.

[Eddie Dean]

Wasn't talking to you leaddull.
Sorry Rutan misunderstood your thoughts.

[youngmic]

Before starting the engine select full coarse on the prop and be careful not to let the engine rev much on start up

Interesting...could this be one for Mythbusters? I have never tried it so obviously zero real world experience, maybe it works....

But given an aircraft needs exactly the same amount of thrust to move, it would likely follow that the same aerodynamic flow forces are in play. As such tip vortices and the surrounding frontal low pressure area might be much the same. In fact with a higher AoA what might occur is a greater amount of thrust at the tip and with it perhaps a stronger likelihood for a ground vortex to be created closer to the tip. As opposed to the finer pitch setting which may well have negligible AoA at the tip. If you watch those ground vortexes, once established they seem to like to settle about a 1/4 way up from the tip.

The difference only being a higher blade AoA and slower RPM, of course the slower RPM will have a significant mitigating effect on the size/depth of the dent. Assuming you can reach governing speed off idle, I seem to recall some types being shut down in course pitch to try and achieve this.

To my thinking the key to it is never let a stone sucking vortex even form from ground to prop as once it forms it will start picking up stones.

I liken the whole exercise to a bit like standing on a meat ants nest in thongs, it's no problem as long as you keep moving.

Interesting thought anyway.

[A Squared]

I am seriously struggling with the concept of overhauling an aluminium fixed pitch propeller.

Did the AD under discussion include fixed pitch props? I had assumed it was about constant speed props, although a 172 was mentioned and obviously they normally have fixed pitch props. Can someone explain the AD to a non-ozzie?

[rutan around]

To my thinking the key to it is never let a stone sucking vortex even form from ground to prop as once it forms it will start picking up stones.Mic you are correct and I don't know whether the reduction in prop damage was due to less rocks being sucked up or that they still were sucked up but hit with less force. Controlling revs on start up apart from being good for a cold engine is so you don't have that momentary rev excursion up to say 1,800 revs. It only takes one rock to ruin the owners day. Also you will find when the prop is set on full coarse the revs are governed to not much over 1,800 no matter how much throttle is applied.

An interesting test for people with time on their hands would be to spread flour or similar in front of the prop and observe where vortices form at the revs needed to start the aircraft rolling both at full fine and full coarse. Any takers?

[youngmic]

An interesting test for people with time on their hands would be to spread flour or similar in front of the prop and observe where vortices form at the revs needed to start the aircraft rolling both at full fine and full coarse. Any takers?

That'd work, but sounds like a lot of rutan around.

[A Squared]

Controlling revs on start up apart from being good for a cold engine is so you don't have that momentary rev excursion up to say 1,800 revs.

OK, I gotta ask, is it common for your engine to spool up to 1800 RPM when you start it?

[rutan around]

OK, I gotta ask, is it common for your engine to spool up to 1800 RPM when you start it? Not when 'I' start it.http://cdn.pprune.org/images/smilies/evil.gif However in 45 years in and around aviation I have seen some, shall we say, 'interesting' start ups.:rolleyes:

[Jabawocky]

Just read about another story today.

This is Why I keep telling people to invest in a good engine monitor and an Advanced Pilot Seminars engine class. This guy should too. :ooh:

So, I get the plane home from annual and the EGT gauges (single point) no longer line up at idle or even take off where they used too. The right one reads off the chart low, whatever that means, and the left one reads higher. On top of that the right engine CHT(single point) is reading higher than normal quickly showing 400 degrees on climb and that is unusual. Also the right oil temp is noticeably higher than normal usually a tad over 150; now 190-200. LOP at 12k I still cannot get the CHT below 400 when it's usually 350 easy. Then I noticed on the mag checks there was hardly any drop when switching mags; this is unusual; I usually get at least a 50-75 rpm drop off. So finally I ask another mechanic and suggested maybe the mag timing was off. Comments?

Maybe the mag timing is off? :eek: Ya kidding me! No doubt and it is advanced what's worse!

[Jabawocky]

Thought I would share another one.

With a class coming up in November this is timely. This fellow is a lovely B737 pilot with a gorgeous RV8 (LAME Maintained). And a real student of the science. Well done sir! :ok:

Gday David,

I've now installed the Dynon EMS D10 into my RV8 and it is fantastic. The engine has been running roughly, but still (just) passing the 1800 RPM mag check*. With the engine monitor and the knowledge from the course to really use it, I could fly without being terrified by the rough running because I could easily see the cause, and after landing I was able to ask my LAME to replace the lower plug on the number 3 cylinder to fix the problem.

Last month I flew with my LAME mate from America in his RV7 who is a true believer of the 50 ROP technique. After hearing me out, he let me run the engine as lean of peak. One of the CHTs was higher than he liked and he was about to shove the mixture in to fix it. I persuaded him to let me lean it out a fraction more, and when the CHTs all dropped 10 degrees you should have seen his jaw drop. He promised me he'll be going to do the course at Ada.

Love the knowledge to use the D10 - it's like having little windows in all the cylinders.

Keep up the good work. I'm trying my best to spread the word about you guys.

Cheers,

Rob

* I also get that a mag check isn't as good as a higher power in-flight check

[aldee]

Where you holding the November course Jaba ?

[UnderneathTheRadar]

Adelaide - money very well spent.

Someone asked me if I was the very smart guy, who randomly visits this forum and has a large pressurised twin that started this thread off - but I failed at the first test....

[youngmic]

The knowledge gained from understanding the chemistry and physics of piston engines is not only for the balanced injector multi probe fraternity it is a huge benefit to any pilot regardless if you never fly a machine equipped to operate LOP.

Here is the why.

A few years back I was in a position (briefly) to oversee a mixed bag of pilots flying piston SEA. One of these pilots was good enough to point out to me that he was unable successfully lean the IO-520 C210 as he had in the past (the company was a 50 ROP operation).

I jumped in and went for a ride, the single EGT and CHT was all it had, after take off and leveled it quickly became apparent that full rich equaled 75 ROP.

Somewhat concerning and leading to the next question where the hell was it during full power, fuel flow looked fine and it leaned smooth enough for a standard set up in cruise, so likely no blocked injector. With the engine as cool as I could get it a brief full power setup and very quick lean to have a look.

Just as I hoped I wouldn't see but did, at full power it was running 75 ROP too.

Back at the engineer facility I pointed out FF seems right but this EGT indication is worrying (note Fuel Flow is a pressure indication not fuel flow).

They changed out the probe, still no joy, they checked the FCU and all in speck and checked all the injectors too. At this point they were happy to shrug their shoulders happy to see it fly away. After I showed some persistence they did set FF's at the max permissible and this resulted in a positive change, now it was 85 ROP at full power and full rich.

I was still not happy, clearly this engine was talking its just that we weren't listening properly.

The engineering company brought in the big guns, a major aircraft and engine rebuild shop, they were keen to play down the significance of an EGT reading if everything else checked out.

Feeling very unsupported I decided to give TCM tech support in the US a call. I now felt supported they backed me up stating at the absolute minimum 150 ROP should be achievable and if we aint see'n it then keep looking and don't worry about setting a FF above red line.

The company in turn brought in a very wise local CAR 35 fellow hoping he would douse the fire and cure me of my troublesome thoughts, then I could release the aircraft back to service. Fortunately he was a well read and wise fellow and stood by what TCM and I had been saying, there is a problem.

In the end they set a smidge over red line fuel flow, they could not get past the fact the red line was a legal limit that could get them in the poo for willfully ignoring.

In the end I think I saw 125 ROP at take off power, far from ideal, but the best I could push for.

Without the knowledge gained through JD and et al that poor old engine would have been climbed out under power, often in stinking hot OAT's running just a tad outside of the optimum detonation mixture setting. And given the natural spread of inter-cylinder mixture maldistribution no doubt some cylinders were smack bang at best detonation.

Sadly not many seemed to care.

[Jabawocky]

MIC......that is eye watering :eek:

TCM were understating it. More like 200dF+ would be better.

The funny thing is if you are intellectually honest with yourself and the science you simply compare the BSFC at takeoff on a typical and properly set up Lycoming, and ask....what is actually different here? The answer is nothing.

You did well under pressure :ok:

And just a warning for Lycoming owners with engines or FCU's that are new in the last 3 years, do not assume they are set right. I have seen at least half a dozen now, and that represents a high number in percentage terms of new ones I have seen that need to come off and onto the flow bench. The Avstar and Precision folk I think are letting them out the door even if they meet min spec, and probably some old timers that worked their knew they all needed to be a max spec.

MIC
You might be pleased to know there is a propulsion engineer at CASA that is intrigued by this situation, I have offered to simulate in flight and record data on the effects of minimum or less flow, and then I will show him pressure traces. Only a long shot but maybe he will take the issue further. Not holding my breath but it is the first sign of hope!