Why was the BF109 so slow compared with the P51?
- Thread starter johnbr
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swampyankee
Chief Master Sergeant
- 4,022
- Jun 25, 2013
Because North American had better aerodynamicists than did the Messerschmidt company, and those NA engineers also had access to better resources. After all, look at how many Luftwaffe aircraft used NACA airfoils.
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If that was the case then the P-51 would have been available at the same time as the Bf109, in service in 1939/40.
Crimea_River
Marshal
Getting my popcorn....
fubar57
General
Have some of mine...
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Bf109 V13 set the world airspeed record in November 1937 (379mph) and the P-51 was...wait...it didn't exist at the time.
swampyankee
Chief Master Sergeant
- 4,022
- Jun 25, 2013
Why does that follow? The USAAF's leadership didn't see need the P-51 in 1935 or 1936
swampyankee
Chief Master Sergeant
- 4,022
- Jun 25, 2013
The absolute record, in 1937, was still held by a floatplane, the MC.72, which was about 100 km/hr faster than the Bf.109V13. I would hardly consider a floatplane to be a exemplar of good aerodynamics.
Well, then, my friend, you need to have another look.
As for the P-51/109 question ... cooling drag. Like the Spitfire, the 109 never actually got Meredith to work despite trying very hard to get it to, therefore binned Meredith and assumed it must've been the wing which, frankly, it wasn't (according to Lee Atwood).
Funnily enough, I've watched the video a week ago, as well as the 'spin-off' titled, roughly, 'Why Bf 109K was faster than Mustang'.
I'd toss in some details the author got wrong or iffy at least. Eg. his suggestion that engine's cubic capacity has a lot to do with aircraft speed, or that variable S/C drive is a contributing factor. He says that P-51 had 'some aerodynamic advantages' - nope, IMO that's downplaying it. (advantages). Then - manifold pressure is also a function of compression ratio, the tidbit does not get mentioned. Video says that 109s used 95 oct fuel - not true. 'No technology can overcome advantage in fuel grade' - nope, technology was there, called ADI, used by Germans as MW 50. 'P-51's primary advantage was fuel' - ?? 'Bf 109 does not have enough of roomfor duel S/C' - ?? 'Mustang's designers could simply gear the S/C...' - ??
All of this in 1st 7 minutes.
I'd toss in some details the author got wrong or iffy at least. Eg. his suggestion that engine's cubic capacity has a lot to do with aircraft speed, or that variable S/C drive is a contributing factor. He says that P-51 had 'some aerodynamic advantages' - nope, IMO that's downplaying it. (advantages). Then - manifold pressure is also a function of compression ratio, the tidbit does not get mentioned. Video says that 109s used 95 oct fuel - not true. 'No technology can overcome advantage in fuel grade' - nope, technology was there, called ADI, used by Germans as MW 50. 'P-51's primary advantage was fuel' - ?? 'Bf 109 does not have enough of roomfor duel S/C' - ?? 'Mustang's designers could simply gear the S/C...' - ??
All of this in 1st 7 minutes.
Zippythehog
Staff Sergeant
- 761
- Jan 7, 2017
I believe the main answer is that the U.S. and Britain had far better fuel. The powerplants of the two A/C in question had different compression ratios. The Merlin engine specified higher octane than the DB because they could.
DarrenW
Staff Sergeant
Wow I really need to watch that video again, and this time while paying far better attention to what's said! I actually didn't notice all those "glitches" Tomo, but knowing how you're VERY well-schooled in various aircraft technology, I don't doubt any of it one bit.....
DarrenW
Staff Sergeant
Not trying to challenge you here, but do you or anyone else have any charts that show this to be true? I don't, but that doesn't mean they don't exist somewhere.
cherry blossom
Senior Airman
- 513
- Apr 23, 2007
Floatplanes were able to use very long runways and could therefore have relatively small wings. I suspect that a land version of the MC.72 could have been built with a retracting undercarriage and flown from Edwards Air Force Base (then Muroc), which would have been even faster.
DarrenW
Staff Sergeant
Wasn't the Allied equivalent lean octane rating of C3 fuel around that number?
IIRC the Allies called the C3 as '96 oct fuel', while Germans called it '100 oct fuel'. Both values being lean rating, while rich rating going steadily up towards 140+ as war progressed. Used mostly by DB 601N and BMW 801D.
The fuel used by most Bf 109s was B4 - 87 oct.
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