100/150 usage in the USAAF

[KraziKanuK]

Anyone have info on this fuel grade usage, especially when used in the P-38?

[FLYBOYJ]

I believe you mean 100/130?

In the past, there were many different grades of aviation gasoline in general use e.g. 80/87, 91/96, 100/130,108/135 and 115/145. However, with decreasing demand these have been rationalised down to one principle grade, Avgas 100/130. (To avoid confusion and to attempt to eliminate errors in handling aviation gasoline, it is common practice to designate the grade by just the lean mixture performance, i.e. Avgas 100/130 becomes Avgas 100). More recently, an additional grade was introduced to allow one fuel to be used in engines originally designed for grades with lower lead contents: this grade is called Avgas 100LL, the LL standing for 'low lead'.

80/87 was(is) red, 100LL is blue, 100/130 is green and 100/130 is purple

[FLYBOYJ]

Just found this on another fourm....

"You are correct that 150 octane fuel was approved for use in July 1944. However for some reason it was not put into widespread use until the last few months of the war. What we see is a big influx of 100/150 Grade in July and then a sharp reduction of it's use until the March '45 timeframe."

[wmaxt]

Originally Posted by KraziKanuK

Anyone have info on this fuel grade usage, especially when used in the P-38?

In the Alutions and the Pacific durring the war the US supplied fuel was 100/130 or better and the P-38s did well. In the ETO 87 was common and the practice of adjusting the octain was normal through the winter of '43/'44. Sometimes this adjustment was done in 55 gal drums so it was not very accurate or mixed properly. The result of this method of octain adjustment contibuted to the engine problems in the early P-38s, which as a turbo charged engine was particularly sensitive. When the fuel got better the problems ceased, though Allison also modified the intake plenum to help this situation too.

Improper cruise technics (low manifold pressure and higher rpm) contributed by lowering the air/fuel charge to the point the lead would come out of suspension.

wmaxt

[Jabberwocky]

Originally Posted by FLYBOYJ

Just found this on another fourm....

"You are correct that 150 octane fuel was approved for use in July 1944. However for some reason it was not put into widespread use until the last few months of the war. What we see is a big influx of 100/150 Grade in July and then a sharp reduction of it's use until the March '45 timeframe."

This actually refers to total European use, not just USAAF use. As far as I know, 150 Grade Aviation spirit wasn't used iby the USAAF anywhere outside NW Europe.

Furthermore, here actually wasn't any 'sharp reduction' in 150 used. This issue has been chewed over before.

I remember this discussion from the IL2 boards too. I also remember the posts made to refute this statement;

The 'sharp reduction' you speak of is the dip from 20-30 thousand tons usage in the June to October down to around 23,000 tons in the November to January period, something that would be considered quite normal if you look at the yearly fuel usage patterns of the RAF and USAAF in the winter period. Besides, it is a reduction of less than 20%, not really that massive, particularly when you consider that the V1 intercept operations over England ended in very early September, with a sharp decrease in operational tempo for 150/100 approved units (Spitfire IX, Mustang III, Sspitfire XIV, Tempest II, Mosquito) in the mid August peroid as more and more launch sites were over-run.

N/W Europe had a serise of bad winters durng the 1940 -1945 period, with a commesurate deterioration in weather and number of flying hours. Just look at the massive reduction in flying hours for the 'trailing the coattails' offensives that the RAF ran from 1940/'41 through to '43/'44. Winter was generally a refit and slowdown period.

VII Fighter Command converted ALL of its fighter squadrons to 150 grade aviation spirit between July and September of 1944. There were at least 15 RAF squadrons on 150 Octane by the end of July 1944. Ninth Fighter Command didn't switch to 150 Grade until much later. It is a similar story with 2 TAF, with the exception of some units who sitched back and forh between the two grades.

ADGB and VII FC account for the vast majority of operational use of 150 octane in the May 1944 to May 1945 period . Bomber, liason, training, transport and ancillary aircraft all stayed on 130/100 Grade fuel, while the fighter and fighter bomber units made the tranisition. So while it may appear that 150 Grade is a relatively minor proportion (arount 15-20% of the total), its actual front line use is a very high percentage of sorties undertaken.

[Jabberwocky]

Originally Posted by wmaxt

***SNIP
In the ETO 87 was common and the practice of adjusting the octain was normal through the winter of '43/'44. Sometimes this adjustment was done in 55 gal drums so it was not very accurate or mixed properly

SNIP ****


wmaxt

Was this for USAAF units or for British units?.

As far as I can remember, the RAF transitioned their fighter units onto 100 Grade aviation spirit around June-September 1940. Something that was carried out during the height of the Battle of France and completed during the Battle of Britain!

There are several reports of pilots flying sorties over the Dunkirk evacuation pushing their aircraft into the 12lbs emergency overboost for limited periods of time.

So if the RAF had made the transition to 100 Octane by the end of 1940, what were USAAF P-38 units doing on 87 Octane in the Winter of 43/44?. The RAF initially had to import the majority of its supplies of 100 octane from the US because the UK wasn't set up to produce it in 1940.

[wmaxt]

Originally Posted by "Jabberwocky

Was this for USAAF units or for British units?.

So if the RAF had made the transition to 100 Octane by the end of 1940, what were USAAF P-38 units doing on 87 Octane in the Winter of 43/44?. The RAF initially had to import the majority of its supplies of 100 octane from the US because the UK wasn't set up to produce it in 1940.

I've read of the 87 octain as base fuel in this instance as British standard but was adjusted for the turbo supercharged engines in the P-38. It's possible I/they were out of context on the octain number. In the spring of '44 more fuel of the higher grades was available and the hand mixing was not required. These issues in the Pacific where the fuel was already mixed never occured.

wmaxt