"WORN OUT ENGINES"

[GrauGeist]

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.

 

[nuuumannn]

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...

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.

 

[BobB]

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.

 

[Deleted member 68059]

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.

 

[gumbyk]

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.

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

 

[Deleted member 68059]

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...

 

[gumbyk]

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...

 

[FLYBOYJ]

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)

 

[pbehn]

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.

 

[gumbyk]

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.



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)

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

 

[FLYBOYJ]

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

 

[FLYBOYJ]

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!

 

[MIflyer]

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

 

[MiTasol]

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.

 

[MiTasol]

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.

 

[MiTasol]

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.

 

[MIflyer]

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.

 

[GrauGeist]

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.

 

[FLYBOYJ]

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.

 

[FLYBOYJ]

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.