Inaccurate performance data for BOB fighters in COD comparing to RL data

[TheGrunch]

Sounds like that's an extreme case to me Kurf. I've looked at a few of them, but so far:

• 32 Squadron flew 60 and-a-half non-operational hours in the first week of August 1940, all of which were transfers to and from their forward base.
• 43 Squadron flew approximately 10 non-operational hours in the first week of August 1940, namely one transfer of six aircraft and their return and another transfer of seven aircraft, and three night practise flights.
• 54 Squadron flew approximately 106 non-operational hours of a huge variety of kinds (beware that one page of the ORB appears twice in a search for some reason).

There's no data for 56 Squadron in 1940 so I'm not sure which one you looked at. Anyway, won't be posting for a while, I hear the human body needs sleep.

[DC338]

Why would they use 100 octane fuel to run in a engine? If it was as scarce as you would have us believe surely they would have used 87oct for non operational purposes.

[madrebel]

because there was a conversion process that wasn't exactly trivial. further engine testing would be done at the levels the engine was expected to run at. you wouldn't test an engien you planned to run on 100 octance with 87 octance.

etc.

[TheGrunch]

It's definitely sensible to run-in engines at their 5-minute limit boost levels.

[madrebel]

because that was the only difference right?

[TheGrunch]

Originally Posted by madrebel

because that was the only difference right?

These were the alterations made (dated March 20th 1940). After the alteration the only difference in actual operation was the modified boost cut-out control allowing the ability of the engine to be run on 100 octane fuel up to +12lbs. sq. in. The engine was still perfectly capable of being run on 87 octane fuel and indeed this would avoid the problem of lead fouling of the spark plugs if they had not been changed to the new ones.
You will note the last paragraph. Mechanics were not likely to run the engine up to +12lbs on the ground. Its use significantly reduced engine life.

[Viper2000]

Since the FTH for +12 was 10,000 feet or so, it would be pretty reckless not to ground test at +12 to ensure that Mod. No. Merlin/154 was embodied correctly given that it was a local mod; otherwise there would be no guarantee that +12 might not be exceeded, leading to rapid failure in flight.

Reverting to 87 octane would require that the 87 octane limits be observed; since operation of the cutout would now give +12 it would probably be wired shut; clearly in this condition the aeroplane would not be exactly combat ready.

Having filled the tanks with 87 octane again, they would probably require cleaning when reverting to 100 octane to ensure that the fuel reaching the engine met the performance standard.

Changing fuel is not quite so small an undertaking as many would imagine; aeroplanes are less forgiving than cars, and the consequences of engine failure are inevitably more severe.

[Kurfürst]

Originally Posted by TheGrunch

Sounds like that's an extreme case to me Kurf. I've looked at a few of them, but so far:

• 32 Squadron flew 60 and-a-half non-operational hours in the first week of August 1940, all of which were transfers to and from their forward base.
• 43 Squadron flew approximately 10 non-operational hours in the first week of August 1940, namely one transfer of six aircraft and their return and another transfer of seven aircraft, and three night practise flights.
• 54 Squadron flew approximately 106 non-operational hours of a huge variety of kinds (beware that one page of the ORB appears twice in a search for some reason).

There's no data for 56 Squadron in 1940 so I'm not sure which one you looked at. Anyway, won't be posting for a while, I hear the human body needs sleep.

My bad, 54 Squadron. But I agree this could be an extreme case. My point was rather to illustrate that there would be considerable fuel requirement for non-combat sorties as well, which is usually not being taken into account.

[TheGrunch]

Originally Posted by Kurfürst

My point was rather to illustrate that there would be considerable fuel requirement for non-combat sorties as well, which is usually not being taken into account.

Definitely agreed there. As it was stated earlier in the thread there was a lot of movement to and from forward bases which seems to have been the bulk of the non-operational flying for operational squadrons, particularly for squadrons flying into and out of Manston due to its exposed nature on the coast I suppose.

[fruitbat]

Hi, Kurfurst the page you linked showing 54 squadron on training flights was during one of the times they were posted north to Catterick on a rest period.

54 squadron had 3 rest periods north, once after Dunkirk, once in june and once end of july/start of aug if memory serves me right.

Catterick was not an operational base during BoB, being well up north, one can only speculate at what fuel was being used there.

It would seem logical that 100 octane was not really needed there....