Mustang & Spitfire drag doc

[tomo pauk]

Few hours ago, D Deleted member 68059 posted an interesting doc in the twitter: link
The doc notes that Mustang (I ?) have had lower drag than Spitfire V, but some details can raise the eyebrows. 1st - engine type on the Mustang - the F32 is noted, and that one was the 2-stage intercooled version that XP-51J was supposed to get in 1945; obvious question is 'what engine was actually on the Mustang?'.
Then, Mustang did just 1 (one) mph more than Spitfire V, despite, at least according to the doc, it had 1150 HP at 19000 ft, vs. Spitfire V with 1130 Hp at 19500 (both values are with ram effect). Something seems amis here - the F3R engine even with full ram seems incapable of making more than 1100 HP already by 15000 ft, and if the better V-1710 is installed, like the -81, Mustang will make 390-400 mph between 17000 and 20000 ft. Mustang tests.

Any takers?

 

[Deleted member 68059]

I would guess a simple typo, as the letters intent is to agree that the Mustang has much lower drag, so the last two type-written lines saying it has the same speed as a MkV SPitfire at the same height with the same power makes no sense at all.

Probably its F3R V-1710, not F32.

The power quoted for the MkV spitfire is about right for Merlin 46 at 19,000 feet.

The F3R at 19,000 feet is about 880 bhp, they seem to have accidentally typed in the F3R power
as it is at peak rated altitude (which is at about 12,500 feet)

 

[SaparotRob]

I'm surprised I missed that.

 

[drgondog]

Few hours ago, D Deleted member 68059 posted an interesting doc in the twitter: link
The doc notes that Mustang (I ?) have had lower drag than Spitfire V, but some details can raise the eyebrows. 1st - engine type on the Mustang - the F32 is noted, and that one was the 2-stage intercooled version that XP-51J was supposed to get in 1945; obvious question is 'what engine was actually on the Mustang?'.
Then, Mustang did just 1 (one) mph more than Spitfire V, despite, at least according to the doc, it had 1150 HP at 19000 ft, vs. Spitfire V with 1130 Hp at 19500 (both values are with ram effect). Something seems amis here - the F3R engine even with full ram seems incapable of making more than 1100 HP already by 15000 ft, and if the better V-1710 is installed, like the -81, Mustang will make 390-400 mph between 17000 and 20000 ft. Mustang tests.

Any takers?

The most likely reason is that the aouthor (of the letter) forgot that Allison 1150 Hp was at a far lower FTH than Merlin 45