Spit IIa is now so much more inferior to the 109

[Crumpp]

There is no documented use of the original boost cutout as a combat boost system I am aware of, but it would be possible. The pilot would need to be very careful not to exceed a boost level that caused predetonation or engine damage, and the boost would continuously change with rpm, height and throttle position.

That document giving 10.55 psi boost is very interesting. As Banks suggested, it appears to be the boost attained with full throttle and (unmodified) boost cutout pulled at height. The height is about right. Interesting in that such a high boost was usable at all in a Merlin III on 87 octane.

However it is very unlikely that pilots were ever authorized to use the unmodified boost cutout as emergency power because the risk of instant degradation of engine performance was high (especially at low altitudes)

I agree that specific authorization was probably not given and the risk was high.

The RAF pilots were given license to use it in the General Operating Notes. The Air Ministry openend the door and I am sure pilots died as a result.

They were instructed to balance the risk. Given the fact these guys were not the technically savvy pilots we see today, it makes sense you would have a high incidence of those who thought they knew better with such instructions.

Defining that point of balance was obviously an issue for the RAF as several memo's appear at various times during the war warning of the dangers of over boosted conditions.

[41Sqn_Banks]

Originally Posted by camber

However it is very unlikely that pilots were ever authorised to use the unmodified boost cutout as emergency power because the risk of instant degradation of engine performance was high (especially at low altitudes)

Absolutely correct. In fact the were not authorized.

[Crumpp]

Absolutely correct. In fact the were not authorized.

So the argument that the airworthiness limitations were free to be violated because the RAF says to balance risk only works when it fits an agenda?

[41Sqn_Banks]

Originally Posted by Crumpp

So the argument that the airworthiness limitations were free to be violated because the RAF says to balance risk only works when it fits an agenda?

Where does RAF authorities allow to ignore/violate engine limitations? My agenda is to follow primary sources, this makes life pretty easy.

[Seadog]

Originally Posted by Crumpp

So the argument that the airworthiness limitations were free to be violated because the RAF says to balance risk only works when it fits an agenda?

We know your agenda.

The RAF's agenda was to provide the pilot with the best possible performance in high risk combat situations. The RAF didn't want to provide the pilot with an engine self destruct switch, which is what would happen if the boost override was used with 87 octane fuel.

[fruitbat]

Originally Posted by Seadog

We know your agenda.

The RAF's agenda was to provide the pilot with the best possible performance in high risk combat situations. The RAF didn't want to provide the pilot with an engine self destruct switch, which is what would happen if the boost override was used with 87 octane fuel.

+1

Its just Crumpp trying to ignore all the pilot accounts regarding using the boost ie pulling the plug etc,being linked to 100 octane fuel because it doesn't fit with the agenda he's pushing.

[Crumpp]

Where does RAF authorities allow to ignore/violate engine limitations?

In the General Pilots Notes it states the pilot can balance risk and exceed the published limitations. That was the clause used to advance the idea in the 100 Octane thread that the RAF pilots routinely violated the Notes on a Merlin Engine in the Operating Notes.

My agenda is to follow primary sources, this makes life pretty easy.

Mine too. That is why I bring the point up you cannot look at a combat report as proof of 100 Octane use with specific references to +12lbs or 100 Octane.

The RAF didn't want to provide the pilot with an engine self destruct switch

Obviously the RAF was comfortable enough to test it at 12,500 feet on 9-6-39 Merlin III serial number 7491 mounted on Spitfire N3171 up +10.55lbs using 87 Octane fuel.

[41Sqn_Banks]

Originally Posted by Crumpp

In the General Pilots Notes it states the pilot can balance risk and exceed the published limitations. That was the clause used to advance the idea in the 100 Octane thread that the RAF pilots routinely violated the Notes on a Merlin Engine in the Operating Notes.

Paragraph number please. I don't like to read the whole manual to find one sentence.

[Crumpp]

Paragraph number please.

Part I Introductory of the General Flying Notes.

[41Sqn_Banks]

AP 2095, 2nd Edition 1943

In combat and in emergencies pilots must take risks with their aircraft, balancing one risk against another; limitations must be strictly observed only in so far as there is no sufficient reason to exceed them.

I checked the June 1941 edition. It doesn't contain any general statement that aircraft or engine limitations are allowed to be exceeded. It does however explicitly state that the over-ride for the boost control of "an engine normally rated for [...] 87 otane fuel" "may be used only if 100 octane fuel is in the tanks."