Escorts could only stay with bombers for 20-40 minutes?

[drgondog]

You're claiming the Mustang had long range because of its wing.   That's simply not the case.  Fuel fraction and a slick slick fuselage with an efficient cooling system did it.

Certainly a combination of low drag and fuel fraction. That said the first P-51B had less fuel fraction than a.) P-47C/D, F4U-1, P-38F thru H but had more range than all Before the addition of the 85 gal tank, and b.) a wing which drag was less than 70% of the other candidates. 

It was also more advanced in design and tech than any of those you mention.   

The F6F and F4F were very very slow relatively speaking.  The 38 actually had more range than the Mustang, to boot.   The Mustang "laminar flow" wing is an overrated legend.   A wive's tale.

Laminar Flow - No. Low Drag - Yes.

As to P-38 having more range - only by performing un-natural acts such as shutting down one engine and transferring fuel - which was suicide in a high threat environment. The important fact is that AAF mission planners considering the cruise speeds for the mission to achieve a long range escort or a medium range bomb/CAS mission went by the book for Combat Radius as determined by AAF Flight test performance.

[drgondog]

More than one race plane has had around 100 pounds of bondo removed from the plane when they decide it's cracking and could come off.

They are changing the profile of the wings.

That is 100% true, including adding boundary layer 'disruption' trip 'bumps' to trigger an early separation in the .75M range 

[Vraciu]

Laminar Flow - No. Low Drag - Yes.

As to P-38 having more range - only by performing un-natural acts such as shutting down one engine and transferring fuel - which was suicide in a high threat environment. The important fact is that AAF mission planners considering the cruise speeds for the mission to achieve a long range escort or a medium range bomb/CAS mission went by the book for Combat Radius as determined by AAF Flight test performance.

Uhhhh, no.   

The 38 always had more range than a Mustang, particularly with payload.   The techniques used in the Pacific stretched this even further.

And no, they (mission planners) did not use max combat radius on every mission.  We've already shown that. 

[GScholz]

At 400mph at 25,000 feet, the P-51's prop produced 1000 pounds of thrust.  Meanwhile, it's radiator produced 375 pounds of thrust. Meredith Effect.  While most aircraft had to dedicate approximately 10% of engine power to cooling, the P-51 only needed to dedicate 1-2%.

Junkers effect! 

All liquid cooled fighters used Junkers' "jet cooler" effect to reduce cooling drag, including the P-51. It is a myth that the Pony was unique in this regard. It was a well known effect long before WWII. Junkers patented it in 1915.

[drgondog]

Uhhhh, no.   

The 38 always had more range than a Mustang, particularly with payload.   The techniques used in the Pacific stretched this even further.

And no, they (mission planners) did not use max combat radius on every mission.  We've already shown that.

I agree that 'mission planners' did not always use Combat Radius to plan the mission, particularly for PTO common mission profiles. Kenney, via Gunn, directed a lot of programs and techniques to stretch range including dissimilar capacity tanks (much larger than ETO/MTO) that were made in Australia.


What you may be missing in the context is that range planning was at far lower altitudes for bomber escort as well as Fighter Sweeps.

That said, the planners in the ETO/MTO did have a specific Mission profile for bomber escort. It was plan for climb, cruise, RV and escort B-17s and B-24s in the 20-28K altitude envelope.

The P-38J with LE tanks was relegated to mid long range (max Berlin and very few that long after early March) target escort because the P-51B could (and did) go to Stettin/Posnan Poland or Brux/Prague CZ. During Big Week the 15th AF P-38s couldn't make Munich, but with P-51B/D they went to Berlin.

As an aside, the fourth ranking MTO Mustang Group - the 332nd - outscored every one of the P-38 FGs (1st, 14th and 82nd) from July 1 forward. This record despite having so many good fighter pilots and experience, compared to 332nd experience, because they didn't have the range to do deep target escort.

You might ask - "Where were all the great P-38 FG's when the missions to escort B-29s to Japan from CBI and PTO where the Mission Profile was the same as ETO - with one exception, the B-29 at altitude could cruise as fast as P-51D optimal cruise speed at that altitude."

[drgondog]

Uhhhh, no.   

The 38 always had more range than a Mustang, particularly with payload.   The techniques used in the Pacific stretched this even further.

I would draw your attention to the Combat Radius Profiles, as well as ferry ranges reproduced in one set of reference - in Dean's "America's One Hundred Thousand". Page 600

For Ferry Range plots look to Graph 41 and 42 for P-51, 51A, 51B/D, and Graph 17 for P-38G, P-38H and 38J/L.



And no, they (mission planners) did not use max combat radius on every mission.  We've already shown that.

If you look at them you should see that a.) the P-51 (20mm cannon drag) had 180 gallons of internal fuel - no external and its competition for range was P-38E/F/G with 300 gallons of internal fuel.

The Ferry ranges for 1941-mid 1943 were
850 mi for P-38 with 300 at combat load out at 15,800 pounds (full ammo/full internal fuel)
1100 mi for P-51 with 180 gallons at load out at 8700 pounds (full ammo/full internal load)

The Combat radius with external tanks (1550 w/2x75 P-51A, 1400 w/2x150 for P-38H)

The Combat Radius for internal fuel only for P-38J/L with 2x55 gal LE tanks versus P51D with 85 gallon fuse tank

275 mi for P-38J/L at 17,500# at 25K Graph 17, pg 143
375 mi for P-51D at 10,100# at 25K Graph 42, pg 327

Pappy Gun was extremely resourceful, as well as Lindbergh, in figuring out ways of extending range but his methods would Not have worked in the ETO/MTO

As to Meridith Effect to P-51B/D/F. for drag calcs in NAA Performance Analysis the effect of cooling drag was assumed to Net=0 but the calculated drag for cooling system/cowl was far less that 100 pounds at RN>9x10^^6 (say >270 mph). In climb the full cooling drag parameters were applied in the drag build up to determine Power Required.

[DaveBB]

Junkers effect! 

All liquid cooled fighters used Junkers' "jet cooler" effect to reduce cooling drag, including the P-51. It is a myth that the Pony was unique in this regard. It was a well known effect long before WWII. Junkers patented it in 1915.

The P-51 was only mass produced piston aircraft to use the Meredith Effect to a useful potential.  Even the rear doors of the radiator scoop open and close to the optimal level, like that of an afterburning jet engine.

While other aircraft like the 109 series were using engine power to get rid of heat, the P-51 was turning it into 40% additional thrust.

[GScholz]

Myth. Here's the P-51's radiator: Fixed inlet (but with a variable air bleed vent), expansion chamber, radiator, compression chamber and variable outlet. A very typical jet cooler design.

[GScholz]

Here's the 109's jet cooler: Variable inlet, expansion chamber, radiator, compression chamber and variable outlet. The P-51's radiator is narrow and tall, the 109's is wide and short (and divided into two units). Other than that they are practically identical.

[drgondog]

The P-51 was only mass produced piston aircraft to use the Meredith Effect to a useful potential.  Even the rear doors of the radiator scoop open and close to the optimal level, like that of an afterburning jet engine.

While other aircraft like the 109 series were using engine power to get rid of heat, the P-51 was turning it into 40% additional thrust.

Dave -as much as I love the NAA design team and the performance of the Mustang, the major contributors to Thrust was a.) Engine Prop combo (say 1200 pounds at WEP at 20,000 feet), b.) Exhaust Gas (say 140 pounds), c.) Merideth Jet effect - perhaps 20-60 pounds to overcome the cooling drag and spot a few pounds of delta thrust.

That is in full rage, heat generating, ram air effect in level flight. When climbing at 160mpg with cooling drag at peak, the ram effect is much, much less.

Grab a copy of NAA Report 8449, dated 12-1-44 for the Performance Calculations for Model P-51D-5-NA Airplane (N.A.A. Model NA-109) and amble to the Drag Discussion starting on Page 19. On page 21 begins the discussion of parasite drag changes due to angle of attack changes and dives into the cooling drag assumptions for high speed level flight vs climb.

Don't take my word for it, but check out NAA Ed Horkey's analysis as Chief Aerodynamicist. The Co-signatory authority is Louis Waite Chief of Tech Section (i.e. Wind Tunnel and flight measurements among other responsibilities).

[DaveBB]

Here's the 109's jet cooler: Variable inlet, expansion chamber, radiator, compression chamber and variable outlet. The P-51's radiator is narrow and tall, the 109's is wide and short (and divided into two units). Other than that they are practically identical.

(Image removed from quote.)

The P-51 specifically kept it's radiator scoop out of the boundary layer.  That's why it is offset from the fuselage so much.

[GScholz]

Pony has an external boundary layer splitter. The 109 has an internal boundary layer channel that avoids the radiator. Different approaches to achieve the same thing.

[icepac]

Faster without the doghouse.

[Zimme83]

Probably not at 25k+ feet.

[icepac]

I'm not sure you guys are getting it on the mustang scoop/doghouse.

Sure, it makes thrust but it does not make enough thrust to overcome the drag it creates by being there.

This has nothing to do with the topic, though.