# "WORN OUT ENGINES"



## FLYBOYJ (Dec 7, 2021)

Hoping to get some input from some of our resident engine experts (ShortRound6, GregP, Tomo, MiTasol, Bill M and Calum, to name a few, I know there's more). I've seen many publications (and some posts on here usually referencing another source) making references to "worn out engines," or "tired engines." I've even seen this in "Bloody Shambles." In my years in aviation I've identified a "worn out engine" as one that is not meeting manufacture's performance specifications, being operated beyond overhaul limits, having accessories (Magnetos, carburetors, generators, FIUs) operating beyond overhaul limits or having items like motor mounts, engine control cables or control cable rod end bushings worn. I even think we might throw oil leakage in there in many cases. IMO I think this term has been thrown around in many cases without merit or substance, and it seems that over the years it was taken at face value. I think in some cases even pilots may have abused this term.

As many of you know, engines can be overhauled and brought back to original performance specifications. I've seen many general aviation engines (which are a lot less robust than engines from WW2) with thousands of hours on the core overhauled to the point where little difference will be noticed when compared with a new engine.

When I see this term in a post or a publication with no specifics I take it with a grain salt unless specifics are given. What's your take on this? Do you think this term is over-used without merit?

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## MiTasol (Dec 8, 2021)

Worn out engines can have run as little as 10% of their programmed overhaul life for a number of reasons.

The Merlins in the RAAF were often totally stuffed at that stage of life in some areas as they ingested coronus (coral dust) during ground operations including take off and coronus is effectively a very fine grinding compound when inside an engine so the whole inside of the induction system and cylinders were damaged.

In the induction system there was erosion, especially at all bends where the outside of the bends were rapidly sandblasted from polished smooth to very rough. In the supercharger the impeller and vanes are ground away destroying the efficiency and again in the rest of the system right through to the cylinders the polished insides of the system are abraded causing turbulence which results in reduced airflow.

Once inside the cylinders the dust grinds away the cylinder sidewalls and piston rings reducing compression and when the piston moved down the rings crape some of the coronus into the crankcase and oil system which results in all the clearances in the oil system opening up and some finer passages being clogged.

The Allisons in the P-39/40 were far less affected as they are downdraft engines taking air into the aircraft significantly higher off the ground and in the case of the P-40 the intake was immediately behind the prop where the propwash is still clean. NAA did the same on the Mustang but Supermarine never learned.

All these reductions in internal airflow and compression rapidly result in a significant reduction of power and therefore the engine is below its minimum output and "worn out"

Running past the recommended overhaul period does not automatically mean an engine is worn out. I remember one well known P-40 owner in the 1970's had well over 2,000 hours on his engine and it easily made full power because he was religious about his engine maintenance and did oil changes far more often than the TO required. He also serviced changed or overhauled all his critical parts like filters, mags, (coolant, oil and fuel) pumps, radiators and oil coolers at or before the recommended overhaul periods because there is no functional test to determine if they are operating correctly and can be expected to continue so. Overhauling coolers, especially oil coolers, ensures that accumulated crud in the system does not reduce the coolers efficiency. Clogged and contaminated oil coolers have killed many engines and that clogging can be in both the air and fluid side of the cooler.

There are many other things that can wear out an engine. Running overheated or over boosted are obvious. One idiot I knew killed his 0-470s in under 300 hours (cracked cylinders and cracked crank cases) until I went on a flight with him. At the end of the runway prior to releasing the brakes he wound the mixture back until he got peak EGT because that meant peak power. I slammed the mixture full rich, chopped power and ordered him back to the hangar where I told him to go study his engine basics - the engine uses fuel for cooling at all high power settings.

Many a light aircraft owner has come to grief, and often died, through failing to carry out required maintenance on both Bendix and Slick mags and these components usually have an overhaul life far lower than the engine the are keeping running. The _ it flew in so it will fly out_ attitude is the utmost stupidity yet many believe it.

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## EwenS (Dec 8, 2021)

MiTasol said:


> ...........but Supermarine never learned.



I give you the Supermarine Seafire FR.47 (introduced during the production run)












And the Supermarine Spiteful / Seafang (introduced during development)





Vickers Supermarine Spiteful


The final development of the Spitfire




www.baesystems.com










Supermarine Seafang


Page details technical specifications, development, and operational history of the Supermarine Seafang including pictures.



www.militaryfactory.com





Then it was onto jets.

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## tomo pauk (Dec 8, 2021)

MiTasol said:


> The Allisons in the P-39/40 were far less affected as they are downdraft engines taking air into the aircraft significantly higher off the ground and in the case of the P-40 the intake was immediately behind the prop where the propwash is still clean. NAA did the same on the Mustang but Supermarine never learned.



Had nothing to do with Supermarine or with NAA. Engines, or their carbs, dictated the intake placement. 
NAA went with underside intake for P-51B/C/D/F/G/K/H because carb was updraft.


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## tomo pauk (Dec 8, 2021)

FLYBOYJ said:


> As many of you know, engines can be overhauled and brought back to original performance specifications. I've seen many general aviation engines (which are a lot less robust than engines from WW2) with thousands of hours on the core overhauled to the point where little difference will be noticed when compared with a new engine.


(not that I'm a real expert, more likely just an individual that is a bit more informed than the average Joe)

It depended a lot on the purpose of the engine (is it for fighters, bombers, transports, trainers) - the more instances of engine running at aggresive setting, the less hours was it able to run between the overhauls. Eg. the V-1710 was making 362 'flying hours' until overhaul on average in 1st quarter of 1945, vs. R-1820 on a B-17 doing 591 'flying hour' - all for aircraft on the CONUS (source Vee's for victory, pg. 332).

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## Tony Kambic (Dec 8, 2021)

I was told this is from an PW1830 at about 400 hours. Ate the valve.

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## FLYBOYJ (Dec 8, 2021)

MiTasol said:


> Worn out engines can have run as little as 10% of their programmed overhaul life for a number of reasons.
> 
> The Merlins in the RAAF were often totally stuffed at that stage of life in some areas as they ingested coronus (coral dust) during ground operations including take off and coronus is effectively a very fine grinding compound when inside an engine so the whole inside of the induction system and cylinders were damaged.


Great point - I could see how a freshly overhauled engine can be exposed to this over the course of a few days and begin o run like crap.


MiTasol said:


> In the induction system there was erosion, especially at all bends where the outside of the bends were rapidly sandblasted from polished smooth to very rough. In the supercharger the impeller and vanes are ground away destroying the efficiency and again in the rest of the system right through to the cylinders the polished insides of the system are abraded causing turbulence which results in reduced airflow.
> 
> Once inside the cylinders the dust grinds away the cylinder sidewalls and piston rings reducing compression and when the piston moved down the rings crape some of the coronus into the crankcase and oil system which results in all the clearances in the oil system opening up and some finer passages being clogged.


Again, a victim of environment even though the engine many have low time on it 


MiTasol said:


> The Allisons in the P-39/40 were far less affected as they are downdraft engines taking air into the aircraft significantly higher off the ground and in the case of the P-40 the intake was immediately behind the prop where the propwash is still clean. NAA did the same on the Mustang but Supermarine never learned.
> 
> *All these reductions in internal airflow and compression rapidly result in a significant reduction of power and therefore the engine is below its minimum output and "worn out"*


Again, great points that I think was ignored during wartime correspondence and by post war authors


MiTasol said:


> Running past the recommended overhaul period does not automatically mean an engine is worn out. I remember one well known P-40 owner in the 1970's had well over 2,000 hours on his engine and it easily made full power because he was religious about his engine maintenance and did oil changes far more often than the TO required. *He also serviced changed or overhauled all his critical parts like filters, mags, (coolant, oil and fuel) pumps, radiators and oil coolers at or before the recommended overhaul periods because there is no functional test to determine if they are operating correctly and can be expected to continue so. Overhauling coolers, especially oil coolers, ensures that accumulated crud in the system does not reduce the coolers efficiency.* *Clogged and contaminated oil coolers have killed many engines and that clogging can be in both the air and fluid side of the cooler.*


I was flying an old C150, ran the engine to 3000 hours. On a flight I had the engine partially fail, I was able to return to my home airport to find one jug had the rings coming apart, the other jug had valves in pieces. Pre-emptive maintenance always helps!


MiTasol said:


> There are many other things that can wear out an engine. *Running overheated or over boosted are obvious.* One idiot I knew killed his 0-470s in under 300 hours (cracked cylinders and cracked crank cases) until I went on a flight with him. At the end of the runway prior to releasing the brakes he wound the mixture back until he got peak EGT because that meant peak power. I slammed the mixture full rich, chopped power and ordered him back to the hangar where I told him to go study his engine basics - the engine uses fuel for cooling at all high power settings.
> 
> *Many a light aircraft owner has come to grief, and often died, through failing to carry out required maintenance on both Bendix and Slick mags and these components usually have an overhaul life far lower than the engine the are keeping running. The  it flew in so it will fly out attitude is the utmost stupidity yet many believe it.*


I've run into this as well especially on Bendix mags.

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## FLYBOYJ (Dec 8, 2021)

tomo pauk said:


> (not that I'm a real expert, more likely just an individual that is a bit more informed than the average Joe)


 I think way more than the average Joe!


tomo pauk said:


> It depended a lot on the purpose of the engine (is it for fighters, bombers, transports, trainers) - the more instances of engine* running at aggresive setting,* the less hours was it able to run between the overhauls. Eg. the V-1710 was making 362 'flying hours' until overhaul on average in 1st quarter of 1945, vs. R-1820 on a B-17 doing 591 'flying hour' - all for aircraft on the CONUS (source Vee's for victory, pg. 332).


Good points as well - again, ignored or not mentioned by many authors!


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## FLYBOYJ (Dec 8, 2021)

Tony Kambic said:


> I was told this is from an PW1830 at about 400 hours. Ate the valve.


Was this from a crash site?


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## pbehn (Dec 8, 2021)

Further to Timos point about use. If you frequently go to the limits of what is allowed with over boosting like war emergency power for 15 minutes, the engine may still run, but does it run as well as it did a month ago. In a fighter say in the BoB the engines were used to climb as fast as possible then fight, what effect has frequent high positive and negative G and sometimes no G at all on the engine and its oil? I suspect the wear was much more than just normal max continuous. The Motorcycle I raced was a modified road bike, it was worn out doing the mileage that was normally required to run in a new one on the road, not just the engine, but the steering head races, swing arm bushes and break disc, tired was a good word to describe it. These engines were run for hours on proving tests, did they produce the same power at the end as at the beginning, I wonder?

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## Tony Kambic (Dec 8, 2021)

FLYBOYJ said:


> Was this from a crash site?


It was not. I am not sure if the aircraft ( 4 engine ) was in flight or taxing but they sensed a problem with this engine.

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## MiTasol (Dec 8, 2021)

EwenS said:


> I give you the Supermarine Seafire FR.47 (introduced during the production run)
> 
> 
> 
> ...



I stand corrected but do note that the FR 47 was very very late in the types development. Was it post war on Germany?
If so my comment could accurately read_ but Supermarine never learned until the European war was almost over_ because the Spiteful was a 1945 aircraft


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## gumbyk (Dec 8, 2021)

MiTasol said:


> Running past the recommended overhaul period does not automatically mean an engine is worn out.


I had a client (a flight training organisation)who ran their C-172 engines to 4000 hours on an approved extension. To get this, they had an engine that went to over 4,500 hours as an exhibit. everything was still within service tolerances. on the other side of the equation, I've seen engines that are well worn with less than 1,000 hours on them. It's not only the number of hours, but how regularly the aircraft fly, the length of each flight, and how stressed the engine is, as well as build quality at overhaul (balancing conrods, clearances, etc). The engines noted above were IO-360 engines which are designed for around 200 hp, but were only making 160hp - so 75% at full throttle.

The other thing is that a 'worn out' engine may still run perfectly well. Our Tiger had only about 600 hours on it, and ran really sweetly. We had an incident with it that required a tear-down on the engine, and discovered that it was well-worn.

However, I've also seen instances where particular pilots have refused to fly a certain machine because they believed that the engine was worn out, while others were happy to fly it, it ran smoothly, and made rated power, so there is certainly an amount of subjectivity involved.

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## MiTasol (Dec 8, 2021)

tomo pauk said:


> Had nothing to do with Supermarine or with NAA. Engines, or their carbs, dictated the intake placement.
> NAA went with underside intake for P-51B/C/D/F/G/K/H because carb was updraft.


Yes but the NAA intake is immediately behind the prop instead of as close to the carb as possible.
This means the air is taken in front of all the dust stirred up by the prop air flow and as high above ground as possible instead of in the middle of all the dust thrown up and as low to the ground as possible. The Supermarine location maximizes dust collection while the NAA location minimizes it.


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## tomo pauk (Dec 8, 2021)

MiTasol said:


> Yes but the NAA intake is immediately behind the prop instead of as close to the carb as possible.
> This means the air is taken in front of all the dust stirred up by the prop air flow and as high above ground as possible instead of in the middle of all the dust thrown up and as low to the ground as possible. The Supermarine location maximizes dust collection while the NAA location minimizes it.


Okay, roger that. Truth to be told, the low-set intake (or two of them) was a feature of Merlin-powered aircraft like the Battle, the Merlin-powered multi-engined A/C and Hurricane.
Supermarine eventually learned it.


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## MiTasol (Dec 8, 2021)

gumbyk said:


> The other thing is that a 'worn out' engine may still run perfectly well. Our Tiger had only about 600 hours on it, and ran really sweetly. We had an incident with it that required a tear-down on the engine, and discovered that it was well-worn.



I am a strong believer in spectrographic oil analysis on certain engines - especially ones that have had low utilization or been in storage like that Gypsy *may *have been. A certain T-28 I was partially involved with had an engine that had not run for years and I strongly recommended oil analysis to the owner and several hours of ground running before flight even though cylinder removals and internal visuals suggested the engine was okay. The engine failed after a few flights and the aircraft ended on its belly costing far more than a couple of samples would have.

Another factor is the honesty of the previous operator of an engine. I know some private pilots fly five and log one on there aircraft and at one stage I fitted a very low hour engine to an aircraft and it ran like a bag of shit. A quick check showed that the crankshaft was bent so we investigated the history and found the aircraft the logbook showed it came from went in vertically doing a low level loop a week before the date the engine was removed and sold by the insurer.

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## gumbyk (Dec 8, 2021)

MiTasol said:


> I am a strong believer in spectrographic oil analysis. A certain T-28 I was partially involved with had an engine that had not run for years and I strongly recommended oil analysis to the owner and several hours of ground running before flight even though cylinder removals and internal visuals suggested the engine was okay. The engine failed aft er a few flights and the aircraft ended on its belly costing far more than a couple of samples would have.


In the right situation, Oil analysis is good. However, no piston engine manufacturer provides limits that I know of. Lycoming couldn't even tell me where metal might have been coming from when I gave them unusual results. You need to know what to expect. A freshly overhauled engine will have huge amounts of metal in the oil as everything beds in. For monitoring, I found things like acidity, and silicon levels gave a better indication of how the engine was being operated.


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## nuuumannn (Dec 8, 2021)

MiTasol said:


> I remember one well known P-40 owner in the 1970's had well over 2,000 hours on his engine and it easily made full power because he was religious about his engine maintenance and did oil changes far more often than the TO required.



The differences between GA and airline maintenance demonstrated here... With airlines this would be construed as unnecessary and would ultimately cost the operator, therefore maintenance is strictly in accordance with the Maintenance Manual. Nothing is done as a pre-emptive measure unless it is in accordance with some bit of official paperwork somewhere, regardless of how time or effort saving it might be. If the airline or manufacturer get something wrong, it's on them! Although engineering can make recommendations to manufacturers and operators for changes to the MMs.



tomo pauk said:


> (not that I'm a real expert, more likely just an individual that is a bit more informed than the average Joe)



You know much more than most of us about this stuff, Tomo, and frequently demonstrate it, too.



tomo pauk said:


> Supermarine eventually learned it.



Yup, they put a big filter in the intake. A PR.XI versus a Mk.I.




Spitfire static-7 




RAFM 114


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## EwenS (Dec 8, 2021)

MiTasol said:


> I stand corrected but do note that the FR 47 was very very late in the types development. Was it post war on Germany?
> If so my comment could accurately read_ but Supermarine never learned until the European war was almost over_ because the Spiteful was a 1945 aircraft


Yes the FR.47 was the very final version of the Spitfire, being in simple terms the final fully navalised version of the Spitfire F.21/22/24 / Seafire 45/46/47 series which had finally begun to enter service after a prolonged development in early 1945. The FR.47 itself came off the production line between April 1946 and Jan 1949 for a total of 87, some of which saw service in the early months of the Korean War.

Delving back into “Spitfire the history” reveals that comparative tests between aircraft with the two intake types revealed that the earlier intake “was superior in all performance respects”. It was thought that one reason related to the width of the blade roots of the contraprops fitted as standard interfering with the airflow to the intake.

The first production Spiteful was came out of the factory in March 1945 with only 19 built through to early 1947. Seafangs were even rarer. Both types were only used for test purposes.

By the time these aircraft appeared the day of the piston engined fighter was over and jets were already in service.


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## MiTasol (Dec 8, 2021)

nuuumannn said:


> The differences between GA and airline maintenance demonstrated here... With airlines this would be construed as unnecessary and would ultimately cost the operator, therefore maintenance is strictly in accordance with the Maintenance Manual. Nothing is done as a pre-emptive measure unless it is in accordance with some bit of official paperwork somewhere, regardless of how time or effort saving it might be. If the airline or manufacturer get something wrong, it's on them! Although engineering can make recommendations to manufacturers and operators for changes to the MMs.


Than some airlines would be more accurate but this is getting much rarer. In modern airlines this tends to be limited to doing ETOPS maintenance on aircraft that only do non ETOPS flights.

Way back I worked for a Canadian company called Gateway Aviation HQd in Edmonton who were allowed to operate all their Pratt 985 and 1340 engines at 1200hr TBOs when everyone else did 800hrs. They also got more life on the 1830s and Continentals. The owner was an accountant who religiously obeyed his Chief Engineer on maintenance so all engines were oil changed twice as often as Pratt called for and were oil diluted before every oil change. On oil change all oil coolers were drained and all oil tanks were part filled with fuel and then drained after a half hour. The shit this removed from the coolers and tanks had to be seen to be believed. Over the life of the engines the extra labour and consumables was more than repaid in long reliable life and low overhaul costs.

Now too many accountants with no engineering input make all the decisions and demand life extensions wherever possible

One airline that claims it has never had an accident (its had plenty) has had one accident and multiple incidents because they do not even do risk analysis on things like refusing to let pilots use thrust reverse. That put a 747 in the grass a long way past the runway and cost more to repair than replace and they call it an incident.


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## GrauGeist (Dec 8, 2021)

In regards to the Allison's carb intake - yes it's getting "clean Air" - as long as it's the lead ship to get down the strip.
The subsequent planes will be eating dust as they fall in line.

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## nuuumannn (Dec 8, 2021)

MiTasol said:


> In modern airlines this tends to be limited to doing ETOPS maintenance on aircraft that only do non ETOPS flights.



I suspect that the one who determined this should be the definition of airline maintenance has never worked on a turboprop fleet whose aircraft actually work for a living. I can't imagine them having to remove corroded seat tracks from the rear fuselage of an ATR then grinding the corrosion out of them for days on end... Or travelling to a godforsaken paddock of an airport in the middle of nowhere at 3am to change a starter gennie in the rain to get the thing out the next morning...



MiTasol said:


> One airline that claims it has never had an accident (its had plenty) has had one accident and multiple incidents because they do not even do risk analysis on things like refusing to let pilots use thrust reverse. That put a 747 in the grass a long way past the runway and cost more to repair than replace and they call it an incident.



Yes, but this is how airlines run their business. Brand is ultra important. Image is everything and brand perception can and does harm to an airline, look at the slaying United received over the Dr Dao and "United Breaks Guitars" incidents; United had millions wiped off its share prices within a week of these two incidents and customers firmly stayed away, cancelling frequent flyer programmes and avoiding travelling with United. The backlash was severe... It's a very different commercial reality to even big city commerce.


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## BobB (Dec 8, 2021)

A former Tennessee ANG mechanic said that they ran their F-51's Merlins 1000 hrs between overhauls. I've more commonly heard people say Merlins are good for 500-600 hrs. Assuming that his memory was not defective, I wish that I knew the difference in how his ANG unit ran those engines. ANG units have a reputation for taking better care of their aircraft than active duty.


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## Snowygrouch (Dec 8, 2021)

FLYBOYJ said:


> Hoping to get some input from some of our resident engine experts (ShortRound6, GregP, Tomo, MiTasol, Bill M and Calum, to name a few, I know there's more). I've seen many publications (and some posts on here usually referencing another source) making references to "worn out engines," or "tired engines." I've even seen this in "Bloody Shambles." In my years in aviation I've identified a "worn out engine" as one that is not meeting manufacture's performance specifications, being operated beyond overhaul limits, having accessories (Magnetos, carburetors, generators, FIUs) operating beyond overhaul limits or having items like motor mounts, engine control cables or control cable rod end bushings worn. I even think we might throw oil leakage in there in many cases. IMO I think this term has been thrown around in many cases without merit or substance, and it seems that over the years it was taken at face value. I think in some cases even pilots may have abused this term.
> 
> As many of you know, engines can be overhauled and brought back to original performance specifications. I've seen many general aviation engines (which are a lot less robust than engines from WW2) with thousands of hours on the core overhauled to the point where little difference will be noticed when compared with a new engine.
> 
> When I see this term in a post or a publication with no specifics I take it with a grain salt unless specifics are given. What's your take on this? Do you think this term is over-used without merit?



Personally I dont think its a "useful" term to use. In that I cant see any practical use for it, other than saying a particular engine needs a rebuild.

The main reason its pretty meaningless is that (if we`re talking WW2) a worn out DB605 in 1942, might be as little as 4hours at the peak of the exhaust
valve debacle, at exactly the same point in time a "worn out" Merlin might have flown 250hours (although few combat aircraft lasted that long anyway).

If I hear "bearings gone" or "burning oil" at least you know something about whats wrong, worn-out could mean anything. Its far to generic to be useful as a
description.

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## gumbyk (Dec 8, 2021)

Snowygrouch said:


> Personally I dont think its a "useful" term to use. In that I cant see any practical use for it, other than saying a particular engine needs a rebuild.
> 
> The main reason its pretty meaningless is that (if we`re talking WW2) a worn out DB605 in 1942, might be as little as 4hours at the peak of the exhaust
> valve debacle, at exactly the same point in time a "worn out" Merlin might have flown 250hours (although few combat aircraft lasted that long anyway).
> ...


But, a pilot won't know exactly what's wrong - just that the aircraft is a pig to fly...


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## Snowygrouch (Dec 8, 2021)

gumbyk said:


> But, a pilot won't know exactly what's wrong - just that the aircraft is a pig to fly...


Depressingly I`m not a pilot, so I wouldnt know. Although I keep promising myself to save up for a PPL...

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## gumbyk (Dec 8, 2021)

Snowygrouch said:


> Depressingly I`m not a pilot, so I wouldnt know. Although I keep promising myself to save up for a PPL...


I've worked as a Maintenance Controller - trying to translate 'pilot-ese' into 'mechanic-ese'. And I've got a foot in both camps...

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## FLYBOYJ (Dec 8, 2021)

I like Calum's quote, _Personally I dont think its a "useful" term to use._

I think we've put a good perspective on this. Unless you have specifics using the statement "worn engine" is useless. And as mentioned, you may have a pilot who sees performance degradation and without knowing what's really going on it just going to say "this engine is worn."

And as mentioned, you may have a high time engine and it is still making power and performing as advertised - NOT WORN.



> trying to translate 'pilot-ese' into 'mechanic-ese'. And I've got a foot in both camps



Yep! I've overheard many discussions (and I'm sure you have as well) where pilots and mechanics are trying to haggle out a discrepancy, it's like having a groundhog trying to communicate with a parrot!  (Had to throw that in)

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## pbehn (Dec 8, 2021)

FLYBOYJ said:


> I think we've put a good perspective on this. Unless you have specifics using the statement "worn engine" is useless. And as mentioned, you may have a pilot who sees performance degradation and without knowing what's really going on it just going to say "this engine is worn."


I think in a WW2 situation the most likely thing to happen is a new plane or planes being delivered to a squadron and everyone else in the squadron not being able to stay with it. On this side of the pond worn out doesnt mean broken, it means it still works but very poorly.


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## gumbyk (Dec 8, 2021)

FLYBOYJ said:


> I like Calum's quote, _Personally I dont think its a "useful" term to use._
> 
> I think we've put a good perspective on this. Unless you have specifics using the statement "worn engine" is useless. And as mentioned, you may have a pilot who sees performance degradation and without knowing what's really going on it just going to say "this engine is worn."
> 
> ...


My favourite was when a pilot who was also a car mechanic started trying to diagnose engine issues (talking spark advance..)


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## FLYBOYJ (Dec 8, 2021)

pbehn said:


> I think in a WW2 situation the most likely thing to happen is a new plane or planes being delivered to a squadron and everyone else in the squadron not being able to stay with it. On this side of the pond worn out doesnt mean broken, it means it still works but very poorly.


Copy - but without specifics as shown it could mean a multitude of things. When I was in the reserves if a pilot came up to me and said "this plane is worn out" I would have answered "so is your wife"!

Now, many times you may have an engine functioning perfectly but the aircraft is not seeing top speeds, now it may roll into an airframe issue


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## FLYBOYJ (Dec 8, 2021)

gumbyk said:


> My favourite was when a pilot who was also a car mechanic started trying to diagnose engine issues (talking spark advance..)


LOL!

Pilot - car mechanic

That can also be an interesting combination!


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## MIflyer (Dec 8, 2021)

Take a look at the P-51A intake duct with its built in filtering capability.

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## MiTasol (Dec 9, 2021)

FLYBOYJ said:


> Yep! I've overheard many discussions (and I'm sure you have as well) where pilots and mechanics are trying to haggle out a discrepancy, it's like having a groundhog trying to communicate with a parrot!  (Had to throw that in)



Yep. Had an L-188 Electra pilot come in one night and write in logbook _#3 prop loose_. If even the most basic information during his engineering course on the type had sunk in he would have known how stupid that snag was. I signed it off as _retorqued _and did nothing. The next night he raved about how much better the aircraft operated. The next crew was in the room and included the type Fleet Captain who immediately came over to find out what was going on. He reamed the stupid idiot and reminded him it was his job to provide a full and detailed list of symptoms and answer questions from the maintenance staff and nothing more. His previous nights entry would go in the engineering _joke book _and all future reports from him would be treated with the contempt they deserved until he grew a brain. That particular Fleet Captain started in Engineering some 15 years earlier so knew both sides of operations.

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## MiTasol (Dec 9, 2021)

FLYBOYJ said:


> Now, many times you may have an engine functioning perfectly but the aircraft is not seeing top speeds, now it may roll into an airframe issue



Actually it can be far more complex than that. I started my training as an engine maintenance technician but soon after was changed to engine/airframe as the incoming jets (these were early DC-8/707 with JT3D days) used bleed air to run cabin pressurization instead of Rootes blowers or engine driven cabin superchargers like the previous generation. As such it was impossible to completely diagnose if an engine problem was in the engine or bleed air system unless you knew both and to accurately diagnose a pressurization problem unless you knew what the engine was doing. As you say, that is before you get into squirrelly things like cabin door seal leakage, lift dumpers and gear doors that are not fully closed, flaps a fraction of a degree out, aileron seals,etc, etc, etc, which can play games with aerodynamics.

These days with BITE systems many such diagnoses are easy but back then it was all done by knowing the systems and how they operated and were interlinked.

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## MiTasol (Dec 9, 2021)

GrauGeist said:


> In regards to the Allison's carb intake - yes it's getting "clean Air" - as long as it's the lead ship to get down the strip.
> The subsequent planes will be eating dust as they fall in line.


True but the worst of the dust is nearest the ground so the slightly higher in the case of the Mustang scoop still has a benefit and I suspect, and only Calum could confirm, that the prop blades passing just inches in front of the scoop remove a fair percentage of what the aircraft passed through. Low down and far back like the Spitfire is always going to collect far more debris as it is also picking up the aircrafts own dust.
The NA-103 and 104 series Mustangs (Bs and Cs?? or early/late Cs?? from memory Bs were NA-102) also had air filters totally enclosed inside the streamlined cowling, unlike the Spitfire which had filters in that great big ugly boil or carbuncle fitted in place of the lower cowling.


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## MIflyer (Dec 9, 2021)

How dusty does it get in merry old wet England? Not very. When Typhoons began operating from dirt airfields in France they very quickly had to devise filters for them.


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## GrauGeist (Dec 9, 2021)

MIflyer said:


> How dusty does it get in merry old wet England? Not very. When Typhoons began operating from dirt airfields in France they very quickly had to devise filters for them.


I was thinking the dirt fields in North Africa and CBI theaters as well as the earlier mentioned coral fields in the Pacific.

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## FLYBOYJ (Dec 9, 2021)

MiTasol said:


> Yep. Had an L-188 Electra pilot come in one night and write in logbook _#3 prop loose_. If even the most basic information during his engineering course on the type had sunk in he would have known how stupid that snag was. I signed it off as _retorqued _and did nothing. The next night he raved about how much better the aircraft operated. The next crew was in the room and included the type Fleet Captain who immediately came over to find out what was going on. He reamed the stupid idiot and reminded him it was his job to provide a full and detailed list of symptoms and answer questions from the maintenance staff and nothing more. His previous nights entry would go in the engineering _joke book _and all future reports from him would be treated with the contempt they deserved until he grew a brain. That particular Fleet Captain started in Engineering some 15 years earlier so knew both sides of operations.


Amazing how some pilots come up with things at face value. At the academy we had some IPs complaining about our T-41s "running hot." As you know early Cessna temp gauges had a long green ban, a small yellow (caution) stripe and then red. This aircraft was running in the upper portion of the green so a few pilots didn't want to fly the aircraft. Spent many hours trying to convince this guy (and his boss) that this was not an issue.

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## FLYBOYJ (Dec 9, 2021)

MIflyer said:


> How dusty does it get in merry old wet England? Not very. When Typhoons began operating from dirt airfields in France they very quickly had to devise filters for them.


It may not get as dusty like the desert but you will pick up dust and dirt to some degree. Look at the diagram you posted - every one of those moving linkages and hinges will pick up dirt and wear out causing issues so keeping components like this lubricated and clean is a big part of keeping the aircraft and engine healthy.

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## GrauGeist (Dec 9, 2021)

FLYBOYJ said:


> It may not get as dusty like the desert but you will pick up dust and dirt to some degree. Look at the diagram you posted - every one of those moving linkages and hinges will pick up dirt and wear out causing issues so keeping components like this lubricated and clean is a big part of keeping the aircraft and engine healthy.


In a foreward combat area, where the fighters were running several sorties per day, for days on end, I suspect the maintenance to these (and other) components were a bit neglected.

Especially if the unit was under-strength and their fighters were in constant demand.

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## pbehn (Dec 9, 2021)

MIflyer said:


> How dusty does it get in merry old wet England? Not very. When Typhoons began operating from dirt airfields in France they very quickly had to devise filters for them.


You may be surprised, when I was in Scotland the job site was a 7.5 Km track made of ballast with the pipeline next to it, in summer it had to be watered by local farmers to keep the dust down. I cant think of a better way to make a cloud of dust than a metal mesh runway and a squadron of Typhoons on a hot day in France.


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## MIflyer (Dec 9, 2021)

pbehn said:


> I cant think of a better way to make a cloud of dust than a metal mesh runway and a squadron of Typhoons on a hot day in France.


Yes and in some cases it might not even have been metal mesh. This picture from France looks like a pretty dusty area.


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## pbehn (Dec 9, 2021)

MIflyer said:


> Yes and in some cases it might not even have been metal mesh. This picture from France looks like a pretty dusty area.
> 
> View attachment 651020


I think Typhoons had to have metal mesh, or at least thats what the operational weights were based on. Even without rockets or bombs, with the armour fitted they were a heavy beast. Even so, looking at that picture it would leave a great cloud of abrasive paste in its wake on a dry day


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## FLYBOYJ (Dec 10, 2021)

Something with regards to engine monitoring in today's world;

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## RichardSuhkoi (Jan 12, 2022)

Does anyone know the typical warbird operator’s practices regarding component documentation for airworthiness?
For example I think a general aviation mechanic working on a Cessna 172 would want to see an “FAA YELLOW TAG” or a Canadian Form 1, but for a warbird there might be parts with only old military or no documentation. Instead of a valid CMM there might be only very old Technical Orders. The background here is what would a P-40 operator need to fly some nice prop brush boxes I have?


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## FLYBOYJ (Jan 12, 2022)

RichardSuhkoi said:


> Does anyone know the typical warbird operator’s practices regarding component documentation for airworthiness?
> For example I think a general aviation mechanic working on a Cessna 172 would want to see an “FAA YELLOW TAG” or a Canadian Form 1, but for a warbird there might be parts with only old military or no documentation. Instead of a valid CMM there might be only very old Technical Orders. The background here is what would a P-40 operator need to fly some nice prop brush boxes I have?


Hi Richard;

I think it would be a matter of traceability or showing component conformity. If original documentation exists, that should serve the traceability question. If you have the component without paperwork, it would be a matter of a certified individual inspecting and certifying that the component is safe for flight. Some warbird operators have this written into their maintenance programs. You also have to consider life limited components such as O rings and rubber products as well. Hope this helps.


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## RichardSuhkoi (Jan 12, 2022)

That makes a lot of sense. 
I am thinking that if I can find the Technical Orders and show assembly and rest in accordance with them, I can ask an A&P Licensed Mechanic to fill out a tag. In the example of my brush boxes for P-40 it’s I think milliOhms pin to each brush, Insulation Resistance, screw torque, close visual inspection for cracks or corrosion, and that’s it. Above this might be a visit to an FAA Reoair Staion with Prop endorsement or Canadian AMO but I’m hoping not as that would be expensive and I worry they would balk more at lack of origin documentation. These parts were never flown and it shows. The original inspection stamps are clear. Now I need to find the Technical Orders. I’ve written to a few P-40 owners, no luck yet.


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## FLYBOYJ (Jan 12, 2022)

RichardSuhkoi said:


> That makes a lot of sense.
> I am thinking that if I can find the Technical Orders and show assembly and rest in accordance with them, I can ask an A&P Licensed Mechanic to fill out a tag. In the example of my brush boxes for P-40 it’s I think milliOhms pin to each brush, Insulation Resistance, screw torque, close visual inspection for cracks or corrosion, and that’s it. Above this might be a visit to an FAA Reoair Staion with Prop endorsement or Canadian AMO but I’m hoping not as that would be expensive and I worry they would balk more at lack of origin documentation. These parts were never flown and it shows. The original inspection stamps are clear. Now I need to find the Technical Orders. I’ve written to a few P-40 owners, no luck yet.


Exactly! The other road would be a Repair Station or AMO. With the manufacturer's data you might get an A&P to do the tag or an 8130-3


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## MIflyer (Jan 26, 2022)

Operators of older aircraft are allowed to manufacture replacement parts if none are available. Admittedly, engine parts present a significant challenge in that respect. A friend of mine had an OX-5 engine in his Waco and it suffered from low oil pressure. He finally resorted to having the crank ground and plated to oversize to make up for the wear in the crankcase and that worked very well.

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