RAF 150 octane

[Squire]

Yes, I know its been debated already, but a Q. came up in another thread I would like answered, so my apologies, I dont want to hijack the other thread.

Guppy, Karnak, Kev (and who ever else wants in):

http://www.spitfireperformance.com/2taf150_112044.gif

What is the above doc refferring to if the XIV only ran on 100/130? and "never used +25lbs" as was stated?

Im confused since the 610 Sqn doc clearly states 21 lbs being used on 100/130 fuel, so if the XIV got 150 octane one would logically assume it wasnt to run at the same boost, yes?

Its also my understanding that Tempests, P-51s (USAAF and RAF), Spit IXs and Spit XIVs all received the stuff in the anti V-1 missions to begin with.

[Karnak]

150 octane fuel allowed the Spit XIV to be boosted to +21lbs boost from +18lbs boost on 100 octane.  The Merlin 66 and Packard Merlin 266 were able to be boosted to +25lbs boost.

From what Kurfurst says it was not a problem with detonation in the Griffon engine, but rather the bearings were too likely to fail at +25lbs boost in the Griffon 65.

That is how I understand it.  The only chart I have seen about a Spit XIV at +25lbs was a calculated chart, not actual flight test data.

[Squire]

Ok, but if what your saying is accurate then this doc also needs explaining to me.

http://www.spitfireperformance.com/no610orb.jpg

So, what fuel are they reffering to with 610 Sqn?

It indicates 130 octane fuel, with 21 lbs boost. Read the whole doc.

This doc here indicates trials on 25 lbs, and does not appear to me to be "guesswork"?

http://www.spitfireperformance.com/spit14speedns.jpg

...and further I have my own book (quoted in the other thread) that indicates its use. So far from the nay sayers I have not alot, Im not saying im absolutely sure but so far the preponderence of the evidence is with me. If you guys are saying it never used it I would like to see more than just opinion.

[MiloMorai]

Typing error.

[Squire]

Ah ok, so it was 150 octane then for 21 lbs boost. Ok, well Im satisfied with that.

Nothing like a typo to get a guy confused.

I have also seen some references as "130 octane" which doesnt help in research either.

[Squire]

Something else that I find curious is the total silence amongst the P-51 fans. Since the VIIIth AF Fighter Command did use the 150 fuel as well, I would have thought there would have been some posts on it. I have seen very little discussed on the subject however.

[MiloMorai]

Originally posted by Squire
Ah ok, so it was 150 octane then for 21 lbs boost. Ok, well Im satisfied with that.

Nothing like a typo to get a guy confused.

I have also seen some references as "130 octane" which doesnt help in research either.

The 130 might be used to differentiate between 100 fuel and 100/130 fuel.

[Kurfürst]

To help clear up a bit :






So the wanted to increase it to +25 later on, but appearantly did not succeed until the war`s end. See this trial done between March-July 1945, where limitations are still given as +21 :

"The relevant limatations at the time of the test were :-


Condition.................... .............  Boost lb/sq.in. R.P.M.  
Maximum for climbing (normal rating) +9 2600  
Maximum for combat (5 mins. limit *) +21 2750 "


http://www.spitfireperformance.com/la187.html

[Squire]

An interesting reference to the Merlin 63 at +21 lbs, there were a number of Spitfire F.IXs (Merlin 63) still operating in 1944, although most were varients with the Merlin 66 and 70 series in various types.

Also the US built Packard V1650 (P-51).

[Kurfürst]

IIRC ~1000 F IXs, (61 or 63), 4000ish LF IX and 400 IX HF were built, so indeed the LF would be the most common variant, but I`d not underestimate the number of F IXs with Merlin 63. As for the Merlin 70 ones, I recall that there were only two squadrons with them (given the low numbers produced + reserves/replacements etc., and it had kindof a special task, like GM1ers in the LW) Unfortunately there`s very little info even RAF OOBs, even fewer that tell the exact type of aircraft.

[Squire]

Yes, there was not a big need by 1943 for a high alt fighter in the RAF, so the high alt VII and the HF IX saw only limited use in comparison. Most being employed as "regular" fighters 44-45.

[Kev367th]

Originally posted by Kurfürst
IIRC ~1000 F IXs, (61 or 63), 4000ish LF IX and 400 IX HF were built, so indeed the LF would be the most common variant, but I`d not underestimate the number of F IXs with Merlin 63. As for the Merlin 70 ones, I recall that there were only two squadrons with them (given the low numbers produced + reserves/replacements etc., and it had kindof a special task, like GM1ers in the LW) Unfortunately there`s very little info even RAF OOBs, even fewer that tell the exact type of aircraft.

Yeah, the original F IX (Mk V airframe with Merlin 61) was originally made as a response to the 190's. Didn't last long though, and as Kurfurst says the F IX with the Merlin 70 was never produced in significant numbers.
The fights had got lower and they started using the low alt Merlin 66.

[Angus]

Here is a riddle.
The Merlin 61  model 1942 Spitfire IX could cruise at 43000 feet - battle formation. Over France BTW.
So what could an extended wing merlin 70 Spitfire touch a year or two later?

[Kurfürst]

If true, it must have awfully tiresome for the pilot at such altitude, at the edge of stall, without pressurized cabin... whats the data btw?

[Squire]

43,800 ft is the highest reference I can find. The only thing up there would be Ju-86 recon birds.  

Im sure the extended tips would give a bit more control over 30k than you would otherwise get. Damn high.

As for the Merlin 70, I dont think it gave much of an increase in absolute ceiling?, but rather its supercharger kicked in at a higher alt.