Black 6 Thu 19th Apr update re Spit II
 

http://www.spitfireperformance.com/spitfire-II.html

I pressume the new Spit II speeds that that Black 6 mentioned in the Apr 19th update will be in accordance with the speed tests contained in the attached link.

If I read the data correctly, the Spit II should make 294 mph ASI at 1,000 ft and approx 319 mph (+25 mph) when emergency power boost cut-out is operated; or have I got it all wrong?

As I understand it, the emergency power boost cut-out gave approx 25 to 30 mph extra if operated below the full throttle height of 12,800 ft.

Thoughts?

Talisman

I'm not sure if the emergency boost was cleared for the Merlin XII at that time, e.g. for the Merlin XX it was cleared in November 1940, see http://www.wwiiaircraftperformance.o...xx-15nov40.jpg.

It was cleared.

I got original manual for SPitfire MK II from July 1940 where it is emergency boost +12 boost allowed for take off or for 3 minutes.

There is a link at the bottom of the trial data web page to the pilot manual (1940) which shows 12lbs boost available. It is in very small print.

Talisman

"Take-off" boost is not the same as "emergency" boost. See Pilot's Note General (1st Edition, June 1941):

http://forum.1cpublishing.eu/attachm...2&d=1326733398

The description exactly applies to the Spitfire II. There was a "gate" for "take-off" boost and a "cut-out" for emergency power.

From July 1940


http://i42.tinypic.com/34j38t4.jpg


and another manual (probably later)

http://www.spitfireperformance.com/spit2pnfs3.jpg

I'm sure you are referring to this page.
Note the header where it reads "Amended in Vol. I by A.L. 31 and P.N. by A.L./L". This means the content of the page was changed at a later date.
Judging from the date of the previous A.L. 30, which was issued December 1943, I would guess it is from early 1944 if not later.

The page without amendments looks like this: http://forum.1cpublishing.eu/attachm...9&d=1332086948

Note the "List of Contents" page from June 1940. Para 1 of Section 2 didn't contain "Engine data" but "Introductory notes".

http://forum.1cpublishing.eu/attachm...7&d=1332086792
http://forum.1cpublishing.eu/attachm...8&d=1332086871

See this post for more details: http://forum.1cpublishing.eu/showpos...&postcount=677

Of course this doesn't mean that +12 "Emergency boost" was cleared not before early 1944. I would guess it was cleared in November 1940 at the same time as the Merlin XX.

Talisman, pm me your email addy.

Pstyle

Thanks for posting. Wikipedia says:
Merlin XII (RM 3S)
1,150 hp (860 kW); fitted with Coffman engine starter; first version to use 70/30% water/glycol coolant rather than 100% glycol. Reinforced construction, able to use constant boost pressure of up to +12 psi using 100 octane fuel; Used in Spitfire Mk.II.[76] First production Merlin XII, 2 September 1939.[18]

First production Merlin XII Sep 1939 and trial data from the link is dated May 1940, so I would hope RAF pilots were provided with an emergency boost capability, and other improvements, by the time the first Spit Mk II sqn was fully operational later in the year, or they would have had less capability than the Spit MkI. Amendments to RAF Air Pubs show a vertical line in the margin to mark the place the amended information has been inserted on the pages that are effected; I do not see any vertical lines on the page for the latest amendment. Still perhaps someone will be able to clarify the point you raise. Perhaps some combat reports from Spit MkII sqns will help if any of them mention operating the boost cut-out.

Talisman

Not true see my post above with engine settings from Spit Mk II manual from July 1940 not November or later time.