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

[Seadog]

Originally Posted by Kurfürst

Because it wouldn't pose any technical problem, the plane would operate on +6.25 boost, and the boost cutout would not be used. In fact the Spitfire II manual from June 1940 notes exactly that, +6.25 boost limit on 87 octane, and +12 "When using 100 octane" or something along these lines.

Otherwise, you are like a broken record.

So they land at another base and fuel up on 87 octane and then they return to their home base with a tankful of 87 octane...forcing the ground crews to drain it before commencing combat operations with other aircraft of the same squadron flying 100 octane? This would have been a logistical nightmare that would have drawn lots of comments, mostly to the effect that it would be much simpler for everyone to simply use 100 octane fuel. Which is fact was done.

[lane]

Originally Posted by Glider

This paper clearly and without any limitation says that the ACAS has requested that squadrons armed with fighters and Blenheims should begin to use 100 Octane

The second paper May 1940 which is for the Summary of actions for the 6th Meeting of the Oil Committee is the one that contains the magic Certain word. This paper specifically refers to item 9 of the Summary of the Conclusions of the 5th Meeting so it is clear that it is refering to the previous paper.

As I have said before I don't know why he said certain, but I do know that the first paper was clear and that the request was without limitation.
---
Concerned I take to mean that some will not need all the fuel removed. I would expect the large sector stations to keep some 87 Octane in a similar manner to Bomber Command and the Blenheims of No 2 group. The smaller stations would need to have the fuel removed as done for four stations in No 2 Group. Its worth remembering that some units started using 100 Octane in Feb 1940, before these decisions for a complete roll out were made so to some degree it was already out there and in use.
… So back to the first question I ever asked you, what is certain? Which units, which bases.

Originally Posted by Seadog

Why are there no reports, memoirs, articles about RAFFC pilots complaining about the lack of 100 octane fuel for their squadron, station, etc? If some stations have 100 octane and others not, it would have created real problems for pilots landing at alternate bases to refuel, since they would be forced to put 87 octane in aircraft modded for 12lb boost, yet no mention of such problems has ever been recorded.

The idea that RAFFC fought the battle with mixed 87/100 octane Merlin engined squadrons is wrong, and is not supported by the historical record. The battle was fought with 100 octane only.

Check out Post 88 from The use of 100 Octane Fuel in the RAF pt 2. Sometime prior to 7 December, 1939 100 octane fuel was authorized for Hurricane and Spitfire aircraft in Fighter Command. It is quite clear that it was HQ, Fighter Command’s intention to supply all those stations in the UK that held operational Hurricanes & Spitfires with 100 octane fuel.

The operational stations at which the fuel will be required in the first instance are: Acklington, Biggin Hill, Catterick, Debden, Digby, Drem, Duxford, Hornchuch, Leconfield, Manston, Martlesham Heath, Northhold, North Weald, Tangmere, Turnhouse, Croydon, St. Athan and Wittering. Church Fenton, Grangemouth and Filton also “will have Merlin engine aircraft that will require 100 octane fuel.





Taken from: Post 88

The Squadrons equipped with Hurricanes during December 1939 are as follows: 3, 17, 32, 43, 46, 56, 79, 111, 151, 213, 501, 504, 605.

During December 1939 these Hurricane Squadrons were stationed as follows.
3 – Croydon,
17 – Debden
32 – Biggin Hill
43 – Acklington
46 – Digby
56 – Martlesham Heath
79 – Manston
111 – Drem
151 – North Weald
213 – Wittering
501 – Tangmere
504 – Debden
605 – Tangmere

All these Stations were listed as requiring 100 octane fuel.

The Squadrons equipped with Spitfires in December 1939 are as follows: 19, 41, 54, 65, 66, 72, 74, 152, 602, 603, 609, 610, 611, 616.

During December 1939 these Spitfire Squadrons were stationed as follows:
19 - Duxford
41 - Catterick
54 - Hornchurch
65 - Northholt
66 - Duxford
72 - Drem
74 - Rochford
152 - Acklington
602 - Grangemouth
603 - Turnhouse
609 - Drem
610 - Wittering
611 - Digby
616 – Leconfield

Rochford is the only base not listed, however, 74 Operations Record Book indicates that they had 100 octane while at Rochford in March 1940.

Units converting to Hurricane or Spitfire after December 1939 and the station where they converted are as follows:

64 – Church Fenton
92 – Croyden
145 – Croyden
222 – Duxford
229 – Digby
232 – Sumburgh
234 – Leconfield
242 – Church Fenton
245 – Leconfield
253 – Manston
257 – Hendon
263 – Drem
266 – Sutton Bridge
302 – Leconfield
310 – Duxford
312 – Duxford
601 – Tangmere

Sumburgh is the only base not listed to receive 100 octane fuel. 232 formed there in July 1940.

With the one exception of Sumburgh, there is a perfect match between those stations that Fighter Command deemed required 100 octane fuel and those stations where all UK Spitfire & Hurricane operational squadrons were based. I looked through Rawling’s Fighter Squadrons of the RAF and the baseing info checks out.

[Blackdog_kt]

Originally Posted by Seadog

If some stations have 100 octane and others not, it would have created real problems for pilots landing at alternate bases to refuel, since they would be forced to put 87 octane in aircraft modded for 12lb boost, yet no mention of such problems has ever been recorded.

Because it's possible to change octane ratings as long as you keep to the relevant limits?

Again, cue the Blenheim Mk.IV pilot's notes where it's clearly stated that it was standard operating procedure to switch between 87 and 100 octane mid-flight: the only limitation was keeping boost within the appropriate limits for each fuel type, the engine won't suddenly explode if you just throttle back and switch to the 87 octane tanks, even though the engines were modified for 100 octane use.

[Kurfürst]

Originally Posted by lane

The operational stations at which the fuel will be required in the first instance are: Acklington, Biggin Hill, Catterick, Debden, Digby, Drem, Duxford, Hornchuch, Leconfield, Manston, Martlesham Heath, Northhold, North Weald, Tangmere, Turnhouse, Croydon, St. Athan and Wittering. Church Fenton, Grangemouth and Filton also “will have Merlin engine aircraft that will require 100 octane fuel.

So these are the Stations Fighter Command would seen advantagous of having 100 octane fuel?

These are about 1/3 of the stations used by fighters in the Battle of Britain - ca 20 Stations out of ca 60.

[Seadog]

Originally Posted by Blackdog_kt

Because it's possible to change octane ratings as long as you keep to the relevant limits?

Again, cue the Blenheim Mk.IV pilot's notes where it's clearly stated that it was standard operating procedure to switch between 87 and 100 octane mid-flight: the only limitation was keeping boost within the appropriate limits for each fuel type, the engine won't suddenly explode if you just throttle back and switch to the 87 octane tanks, even though the engines were modified for 100 octane use.

P/O Art Donahue's account of using +12 boost during his first combat of 5 August 1940, whilst flying Spitfires with No. 64 Squadron out of Kenley, is typical:

“There are bandits approaching from the north” In quick response to this information, our leader sang out a command: “All Tiger aircraft, full throttle! Full Throttle!” That meant to use the emergency throttle that gave extra power to our engines. I was flying in our leader’s section, on his left. As he gave the command “Full throttle”, his plane started to draw ahead, away from me. I pushed in my emergency throttle in response to the command, the first time I had ever used it, and my engine fairly screamed with new power. I felt my plane speeding up like a high spirited horse that has been spurred. http://www.spitfireperformance.com/spit1vrs109e.html

Kinda hard to keep formation if some aircraft are using 87 octane and some 100 octane...

In a Blenheim flying a long range recon or ferry mission (which is the only time they could use the auxiliary tanks) it is quite reasonable that there will be long periods where the expectation of enemy encounters are low, and thus mixing octane types is a reasonable risk. The problem is that it will take many seconds before the change back to 100octane can be made, and during that time overboost will not be available and damage to the engine may result if overboost is applied too soon.

[Kurfürst]

Originally Posted by Seadog

Kinda hard to keep formation if some aircraft are using 87 octane and some 100 octane...

I guess not so hard as if half of them are Hurricanes and the other half are Spitfires, even if they would use the same fuel type as long as they would be both stationed at the same fighter station...

[Seadog]

Originally Posted by Kurfürst

I guess not so hard as if half of them are Hurricanes and the other half are Spitfires, even if they would use the same fuel type as long as they would be both stationed at the same fighter station...

Which is why squadrons are generally equipped with one aircraft type.

[Crumpp]

Kinda hard to keep formation if some aircraft are using 87 octane and some 100 octane...

No, at any manifold pressure and rpm setting below the knock limited performance of the fuel, the power will be the same.

Basically at any manifold pressure below +9lbs (limit for 87 Octane) in the Merlin, the power is the same for 87 Octane or 100 Octane fuels.

[CaptainDoggles]

The problem is that people think the higher octane fuels magically give more horsepower when in reality they merely allow the engine to develop higher power at higher manifold pressures without engine knock.

[VO101_Tom]

Originally Posted by CaptainDoggles

The problem is that people think the higher octane fuels magically give more horsepower when in reality they merely allow the engine to develop higher power at higher manifold pressures without engine knock.

This is totally true. To see every day on the street when the people buy it their car the expensive 100 octane "V-Power" fuel, though into the car 95 octane would be needed