Modelling engine wear and WEP limitations

[Seadog]

Originally Posted by Crumpp

.

In accidents resulting from engine failure in flight, if the pilot deviated from published operating standards for the engine, it is a factor in the engine failure in EIGHTY FIVE PERCENT of the engine failures recorded by the FAA.

.

Most people reading this thread would have assume that you were referring to the Fleet Air Arm, which was a operator of Merlin engines.

Of course it turns out that you are referring to the USA's Federal Aviation Agency... and trying to roll out civil aviation accident stats to support some kind of argument regarding the Battle of Britain and the use of supercharged engines in combat...!!!!

Simply unbelievable...

Maybe you have this confused with a MFS forum?

[TomcatViP]

At least I had a good laugh Thx !

Perhaps you can understand now why a isolated pilot (not so) in the middle of the channel will only reluctantly use his emergency boost and why he wld be pleased to read in the plane log if the guy right before him has alrdy burnt the engine.

By the way the IL2's 109 had a good eng damage model. Some adaptation wld seem necessary (like a random time length and an initial cte tracing the past use of boost by the player). Just my 2 cents...

[Crumpp]

Most people reading this thread would have assume that you were referring to the Fleet Air Arm

You do understand that physics dictates the margins of safety for flight? A 1.5 Margin is the industry standard for anything that flies....

It does not matter whether you are Military or Civilian, you get off the ground under the same physical laws and restraints.

It does not require grounding of the aircraft pending an engine inspection merely an assessment as whether or not an inspection is needed

The language is clear. A logbook entry in the maintenance logs followed by an inspection is required.

To translate that to non-pilots and A&P's....that means the aircraft is automatically grounded until a mechanic inspects the engine and returns it service.

[Crumpp]

Perhaps you can understand now why a isolated pilot (not so) in the middle of the channel will only reluctantly use his emergency boost and why he wld be pleased to read in the plane log if the guy right before him has alrdy burnt the engine.

LOL, because he enjoys living!!

Here is my return trip this past weekend. ATC vectored me around that development off my right wing in the picture.

Very Heavy precip with 1/2 inch hail....

[Seadog]

Originally Posted by Crumpp

LOL, because he enjoys living!!

Right, so if you are being chased a swarm of Me109s, you'll let yourself be shot down rather than exceed 12lb/3000rpm for more than 5mins?

What you don't seem to be considering is that a Spitfire for example has 85 gals of fuel. TO, climb and cruise to say mid channel will consume say on average about 25 gals, and return will also require 20 gals so the max fuel allowance for combat will be about 40 gals and thus about 25mins, max, at 12lb/3000rpm. No one is going to be using 12lb/3000rpm for more than a few minutes unless there is simply no other way to stay alive, because the fuel capacity of these aircraft is severely limited.

[ICDP]

Originally Posted by Seadog

Right, so if you are being chased a swarm of Me109s, you'll let yourself be shot down rather than exceed 12lb/3000rpm for more than 5mins?

What you don't seem to be considering is that a Spitfire for example has 85 gals of fuel. TO, climb and cruise to say mid channel will consume say on average about 25 gals, and return will also require 20 gals so the max fuel allowance for combat will be about 40 gals and thus about 25mins, max, at 12lb/3000rpm. No one is going to be using 12lb/3000rpm for more than a few minutes unless there is simply no other way to stay alive, because the fuel capacity of these aircraft is severely limited.

EXACTLY

Most pilots would engage overboost during an emergency only. Once the danger was gone you would imediatley ease of on the power, because the next thing on your mind would be, lets not blow the engine... it's the only one I've got. Frankly, constantly saying +12lbs boost could be used without fear until the fuel ran out is ludicrous. The pilot manual and RAF memos explicity state that +12lbs boost was to be used in emergencies only and only for 5 minutes at a time. Do you think they set these limits for fun.

[Crumpp]

The "language" does not state that and the pilot's notes for the Merlin III state:

Sure it does! States right there he must make a log book entry and have the aircraft inspected.



What do you think is going to happen when he makes that log book entry and reports it to maintenance? They must comply with their orders and conduct an inspection, too.

You think the pilot overrides the mechanic on whether or not the airplane is ready to fly?

No, the airplane is grounded until the mechanic conducts the inspection.

[Seadog]

Originally Posted by ICDP

EXACTLY

Most pilots would engage overboost during an emergency only. Once the danger was gone you would imediatley ease of on the power, because the next thing on your mind would be, lets not blow the engine... it's the only one I've got. Frankly, constantly saying +12lbs boost could be used without fear until the fuel ran out is ludicrous. The pilot manual and RAF memos explicity state that +12lbs boost was to be used in emergencies only and only for 5 minutes at a time. Do you think they set these limits for fun.

When you have an aircraft with 85 or gallons of fuel, fuel consumption is never far from your mind, and this will provide the disincentive to not use 12lb boost without justification. However, in fighting over Britain it will be the Luftwaffe pilot who will most fear "to pull the plug" and the tactical advantage to an RAFFC pilot is obvious.

Yet, the trials of, and the operational experience of Merlin engine was that it would run continuously at 12lb/3000rpm with little fear of failure as long as it was running with adequate cooling and lubrication.

[Seadog]

Originally Posted by Crumpp

The language is clear. A logbook entry in the maintenance logs followed by an inspection is required.

To translate that to non-pilots and A&P's....that means the aircraft is automatically grounded until a mechanic inspects the engine and returns it service.

The "language" does not state that and the pilot's notes for the Merlin III state:


and this requires a pilot to log and report the use of combat power.

Dowding's memo states:

"
5. The consequences of exceeding the engine limitations are liable to manifest themselves on some subsequent occasion, perhaps during night flying or over the sea out or gliding distance from land. Pilots therefore, are to be instructed not to exceed;
(i) Maximum specified temperatures for oil and engine coolant.

(ii) Limit of 5 mins. for maximum of 3000 r.p.m. at 6.25 lbs/sq.in. or more.

6. It is in the interests of pilots themselves, when operations With the enemy may have resulted in engine limitations being exceeded, to acquaint the maintenance personnel with the facts, so that oil filters may be inspected at the first convenient opportunity to investigate whether damage to the bearings has resulted."

"...first convenient opportunity..." during wartime is hardly grounded until inspected.

and:
http://www.wwiiaircraftperformance.org/ap1590b.jpg
states

"11. The use, in an emergency, of this high boost pressure is a definite overload condition on Merlin engine and therefore all occasions on which it is essential to make use of the + 12 lb must be reported by the pilot and recorded in the engine log book so that the engineer officer may be able to assess the reduction in life between overhauls and the need for special inspections. "

"...recorded in the engine log book so that the engineer officer may be able to assess the reduction..." leaves it to the discretion of the engineer officer to decide whether an inspection is needed. In no way does this call for mandatory inspections.

and none of these calls for grounding the aircraft until an inspection is made. Rather these call for assessments and inspections as needed depending on the entries in the log books and thus presumably the duration and circumstances under which 12lb/3000rpm was used. Dowding's memo specifically states that operation at 12lb/3000rpm for 5 minutes or less does not need to be reported to maintenance personnel.

Again, the average life of a BofB RAFFC fighter was less than 2 months, so no one was unduly concerned about the use of 12lb/3000rpm in combat situations since the average fighter never survived long enough for engine life to be a major issue. Since about 1000 fighters were lost and something like 60,000 sorties were flown during the battle, the average RAFFC fighter probably had less than 100 hours on the clock when lost. Dowding's memo, for example, does not mention admin penalties for exceeding 5mins at 12lb/3000 rpm but merely states that they not do so, and to report the time when they do.