Bug 174 on 12lbs boost. Review please.

[Kurfürst]

Originally Posted by ATAG_Snapper

Very likely, but I'm not going to spend these fine Spring mornings searching through dusty tomes to check! LOL

A question, though. In motor vehicles it doesn't really matter if you put 89 or 91 (or even 94 like we can get locally in Ontario) octane gas in a vehicle rated for 87 octane. You're just wasting money on the higher octane gas since you'll see no performance benefit, but the higher octane won't damage your 87-rated engine. Would this apply to Merlin engines rated at 87 octane that received a fill up of 100 octane?

If there were no harm (or benefit) that would come of this, I could see at the start of the Battle of Britain some of the older Spits & Hurries receiving 100 octane out on the field.

The answer is also certainly yes, unless some extra complication occure - spark plugs may foul from deposits because the different chemical composition of different grade fuel, for example, as happened with 150 grade. But overall this seems unlikely, at least the papers I have show the Germans too were running some of their Ju 88s - which's engine was designed for 87 octane - on their own 100 octane fuel. So the practice for it was there, on both sides.

[Seadog]

March 28 1940.
Hundred Octane
THE article Fighter Station in this issue contains a
significant reference to the use of fuel of 100
octane number by our fighters. Precise figures
for the increase in performance attained are not immediately
available, but it may be said that in an
emergency the Merlin engines as used in the Spitfires
and Hurricanes can be boosted to a pressure of I2lb.
It is also permissible to state that with its two-speed
supercharger in high gear and operating on 100-octane
fuel the Merlin R.M.2S.M. engine has a maximum output
at 16,750ft. of 1,145 h.p. The effect of the forward facing
air intake will raise considerably the height for
maximum speed.
Like other nations, America has for some time past
used iso-octane fuel in limited quantities for her military
aircraft. Lately she has adopted it as a standard,
and we may refer to the performance figures for the
Republic single-seater of the type used by the U.S. Army
Air Corps. The top speed is increased by five m.p.h.
(to 315 m.p.h.) ; the maximum rate of climb is
•3,150 ft./min. instead of 2,950 ft./min., and the ceiling
•is raised from 29,500ft. to 31,500ft. These increases do
not represent such improvements as are claimed for a
Continental machine with a Bristol Mercury XV. Using
ioo-octane fuel the top speed is 260 m.p.h. at 17,300ft.
whereas with " 8 7 " it was 236 m.p.h. at 15,700ft. The
rate of climb to 19,500ft. is reduced by four minutes.
The immense improvement in the range of the Bristol
Blenheim can be attributed directly to the use of ioooctane
fuel which permits take-off at a much higher all-up
weight. Actually the Mercury now gives 1,050 h.p. for
take-off, compared with 830 h.p.
Whatever the gains which accrue from the use of the
new fuel in our Spitfires, Hurricanes and Defiants, it is
certain that they now have an even better chance of
catching and shooting down raiders.

www.flightglobal.com/pdfarchive/view/1940/1940 - 0897.html?search=octane

and from the article Fighter Station in the same issue:

Hundred-octane fuel surges along the triple arms of a Zwicky unit into the tanks of Spitfires.
http://www.flightglobal.com/pdfarchi...?search=octane

The Bristol flew across the aerodrome full out, which led one to suggest
that, like the Spitfires' Merlins, the Mercurys were
burning 100-octane fuel. But the Spitfires overhauled it
and one by one simulated a stem attack '' opening fire
at what must have been 400 yd. range. As one pilot
broke off his attack and wheeled away another Spitfire
closed in to cover him.
In the afternoon a flight of Spitfires staged some plain
and fancy " beat-ups" of the aerodrome in formation
(excellent vie and echelon) and singly after a peel-off. This
pastime is normally frowned upon, though a certain
amount of joie de vivre is countenanced if the machines
concerned are returning from a victorious interception or
if they are demonstrating for pressmen. Here, again, the
100-octane fuel (which enables the Merlin to receive no less
than 12 lb. boost in emergency) must have been an asset.
http://www.flightglobal.com/pdfarchi...0-%200933.html

[Crumpp]

The airfields did NOT have two sets of fuel bowsers

Of course they did. They had more than two sets when Jets came along too.

The Germans had even more. They used LOX and LNOX. You don't want to mix those two up.

Fortunately they had different nozzles and you would have to be pretty dense to force it past the filler plate.

That is why aircraft are required to be correctly placarded at all fill points. It is part of the airworthiness.

[Glider]

Originally Posted by Crumpp

Of course they did. They had more than two sets when Jets came along too.

The Germans had even more. They used LOX and LNOX. You don't want to mix those two up.

Fortunately they had different nozzles and you would have to be pretty dense to force it past the filler plate.

That is why aircraft are required to be correctly placarded at all fill points. It is part of the airworthiness.

Almost. Most RAF front line stations had one tanker for 87 octane for visiting non operational aircraft but to all intents and purposes they only had one set of bowsers for operational use. This is a general statement but the modern tankers that could refuel two or three aircraft at the same time were used for ops, the older single point tanker tended to be for 87 Octane.

There was an amusing side to this in the NA. Churchill was visiting a fighter station during the BOB when one of the junior pilots said that the turnaround time could be much improved if the staions had just one extra tanker. Churchill wrote to the Chief of the Air Staff about this wanting more information. The CAS had to get his people to look into it and prove beyond any doubt that the main problem with turn around time wasn't fuel it was the time taken to rearm the eight guns on the fighters. Back came Churchill asking what he was doing about it and in the end they trained other station personell such as guards in some of the rearming tasks so if there was a rush they could help out.
What was interesting were the words the CAS was using. You could almost feel his frustration at have to spend a fair amount of time on a topic caused by a junior officer. Equally it showed the care that CHurchill put into listening to his pilots.

[Al Schlageter]

When are we going to read a post stating which squadrons were using 87 fuel and which 16 squadrons were using 100 fuel by the end of Sept 1940?