Modelling engine wear and WEP limitations

[Seadog]

Originally Posted by Crumpp

It means the engine was not required to be stripped apart and internal tolerances checked. That is done at overhaul.

The engine must be inspected according the document you just posted.

It clearly states the engineer must asses the reduction in life of the motor from using emergency boost.

That means done by performing an oil analysis, oil change, compression check, and overall inspection of the condition of the motor.

No, the Merlin engine service manual is pretty clear, that a simple oil filter check was all that was required. Dowding's memo states the same. The engineer officer is always assessing the life of a engine and the regular engine checks are quite sufficient for that.

[TomcatViP]

Well if my car manufacturer would hve include in normal servicing the check of my "Oil filter" as soon as I passed 4000 rpm well... I wld hve run directly to buy a full set of spare engines
What do you think they were looking for ?

[Crumpp]

oil filter check

Seadog,

You have many misguided conceptions about airplanes. Have you ever owned an airplane?

Of course not. You would know this is standard when changing the oil. Every time you change the oil, you cut the filter apart, examine the filter element inside and analyze the oil.

A new engine makes metal and once broken in, an engine makes metal when something is wrong. This metal comes from many different sources in the engine and a mechanic can tell what is going on with your engine from it.

Steel shavings for example generally represents cam wear, valve issues, or ring wear. Aluminum is generally bearing wear. Small flakes of aluminum, depending on the amount is normal or can be excessive. It all depends on the engine type being analyzed.

Chunks of metal are of course very bad.

A sample of the oil is then taken and sent to a lab for microscopic analysis.

Yes, It was a requirement to inspect the engine after each use of emergency power. It was an overload condition for the motor and the reduction in service life had to be assessed by a mechanic and the use of it logged before the aircraft was returned to service.

Combine that with compression checks and an overall inspection will tell a mechanic much about the health of an engine. That is pretty much what is done every year during annual or every 100 hours for commercial/military aircraft to gauge the airworthiness of the aircraft.

Those are the facts based on the documents you posted. Nowhere does the fantasy notion that the Merlin could run in an overloaded condition for as long as necessary exist. It was limited and it was tough on the engine when it was used. The use of Emergency Power had to be logged, the engine inspected, and upon passing that inspection returned to service.

It is that simple, bud.

[Seadog]

Originally Posted by Crumpp

Those are the facts based on the documents you posted. Nowhere does the fantasy notion that the Merlin could run in an overloaded condition for as long as necessary exist. It was limited and it was tough on the engine when it was used. The use of Emergency Power had to be logged, the engine inspected, and upon passing that inspection returned to service.

At least you've given up on this fantasy notion of a strip inspection after every use.

In the BofB the average fighter never survived past 100 hours. This is not civil aviation and trying to look at the battle, where the average pilot had a high certainty of death (probably 25 - 40% in RAFFC) as the same as a flying a light aircraft under VFR conditions is ludicrous. No pilot gave a damn about the engine on an aircraft - that aircraft existed solely to destroy the enemy and bring the pilot back safely. RAFFC had lots of spare aircraft and spare engines and pilots had no qualms about expending them at a furious pace: RAFFC lost about 2.5 SE aircraft per pilot fatality.

Pilots could and did run engines at 12lb/3000rpm for a long as they needed to, and in the final analysis, no one really cared, as long as it gave them the edge in combat, which was why the RAF changed over to 100 octane fuel.

A Merlin III will run at 12lb/3000rpm until the fuel runs out. Given a sufficiently large sample size, this will result in a modest increase in in-flight engine failures, but fuel consumption considerations will always be uppermost in the pilot's mind given the low endurance of these aircraft, and this will be the primary limiting factor.

[VO101_Tom]

Originally Posted by Seadog

...
Pilots could and did run engines at 12lb/3000rpm for a long as they needed to, and in the final analysis, no one really cared, as long as it gave them the edge in combat, which was why the RAF changed over to 100 octane fuel...

What does this mean according to you then (copy from other topic)?

*Buzzsaw* linked several links in 109 e3b against spitfire II topic, i noticed one thing:

http://www.ww2aircraft.net/forum/avi...2-a-20108.html

"The discussion was led by 'Glider' Gavin Bailey, who is a well respected historical journal whose material is subject to critical scrutiny by the best of English historians."

He wrote this:
1st August 1940 Memo from Downing re the Handling of the Merlin Engine
This note is advising the pilots that there is an increase in engine failures in the overuse of the emergency 12lb boost.
The interesting thing is that this memo was sent to ALL fighter groups. Had we been talking about the 16 squadrons or less this would not have been the case. It would have been sent to the squadrons involved.

I think, this unambiguous warning. If was used continuously the 12lbs boost, and the engine was ruined continuously, it does not interest, if COD makes the same one.

[Seadog]

Originally Posted by VO101_Tom

What does this mean according to you then (copy from other topic)?

He wrote this:
1st August 1940 Memo from Downing re the Handling of the Merlin Engine
This note is advising the pilots that there is an increase in engine failures in the overuse of the emergency 12lb boost.
The interesting thing is that this memo was sent to ALL fighter groups. Had we been talking about the 16 squadrons or less this would not have been the case. It would have been sent to the squadrons involved.

I think, this unambiguous warning. If was used continuously the 12lbs boost, and the engine was ruined continuously, it does not interest, if COD makes the same one.

If you read Dowding's memo carefully:
http://www.spitfireperformance.com/dowding.pdf
he discusses a number of scenarios that result in engine oil starvation and/or overheating. The engines were failing, not just from overuse of 12lb/3000rpm but from overheating and lack of oil pressure. Steep climbs damage the engine from overheating, not overboosting. Inverted flying damages the engine from lack of lubrication not overboosting. Dowding memo is pretty clear: keep your gauges in the black! Yes, Dowding states not to use 12lb boost for more than 5 minutes, but the real culprit is overheating and lack of oil pressure. No sane pilot, in a combat situation, say with a 109 on his tail is going to worry about using 12lb/3000rpm for more than 5 minutes, and Dowding's memo is nothing more than a reminder to not use overboost except when really needed.

[VO101_Tom]

Originally Posted by Seadog

If you read Dowding's memo carefully:
http://www.spitfireperformance.com/dowding.pdf
he discusses a number of scenarios that result in engine oil starvation and/or overheating. The engines were failing, not just from overuse of 12lb/3000rpm but from overheating and lack of oil pressure. Steep climbs damage the engine from overheating, not overboosting. Inverted flying damages the engine from lack of lubrication not overboosting. Dowding memo is pretty clear: keep your gauges in the black! Yes, Dowding states not to use 12lb boost for more than 5 minutes, but the real culprit is overheating and lack of oil pressure. No sane pilot, in a combat situation, say with a 109 on his tail is going to worry about using 12lb/3000rpm for more than 5 minutes, and Dowding's memo is nothing more than a reminder to not use overboost except when really needed.

I read it, thanks. Sry, this did not convinced me
They would write it if the injury of the bearing would depend on the temperature only. "Be watching the thermometer, and untill not in red, u can make what you want". Unnecessarily would limit their pilots (5 min limit) without reason?

"but the real culprit is overheating and lack of oil pressure." - and the strain of the drive. I believe it you recognise it you too, it takes advantage of everything if you squeeze more strength from the drive. Winch, crank, bearing, axis, gaskets, cooling, lubrication. They call it emergency power (notleistung in 109) because of this.

"No sane pilot, in a combat situation, say with a 109 on his tail is going to worry about using 12lb/3000rpm for more than 5 minutes" - totally agree I would not care about it. But the engine from this probably gets ruined yet. U reach home, or dont, it depends of luck. If u lucky enough, u can show the oil filter to maintenance team, if not... with an airplane less.

The same one is true for the Bf 109 anyway. Invert flying prohibited its oil system, and the increase manifold pressure until time only it may be used (start und notleistung). It is not linked to the temperature there actually, but this unambiguous. Temperature OR the time a limit defines it, till when it may have been used.

What is interesting yet, and I did not know about the fact that the system of the hydraulic propeller is bound to the engine, not separate system: "loss of engine oil pressure (inverted flight, slow rolls) has an effect on the Rotol aircrew in that baldes return to a fine pitch position". This means that he should lose very much from the performance at this time right?