P-51D vs. Spitfire IX

[ThomasP]

Some numbers you might find interesting.

_____________P-51B____________________P-51D______________________NOTE
15,000 ft_______________________________90°/sec at 210 knots IAS_____ no wing guns, ballast in fuselage for CG limit
10,000 ft_____98°/sec at 260 knots IAS____71°/sec at 200 knots IAS_____ both AC with normal fuel and military load, post-war tests

re P-51D Stick Forces

from a post-war test done by flight test pilots:

__In the course of conducting an analytical comparison of the Mustang, Hellcat, Thunderbolt and Corsair ". . . test pilots measured the [P-51D] Mustang stick force at 70 pounds for a 4G turn and about 90 for a 5G turn at maximum level-flight speed, about 240 kias for their test. Those are estimates, since their force gauge went to only 60 pounds."

__The unanimous view of the test pilots was ". . . the [P-51D] Mustang was a two-handed airplane in which prolonged hard maneuvering was extremely tiring"

from Jeff Ethell, air show pilot with thousands of hours flight in different aircraft and a lot of them in the P-51:

__When flying the P-51A "I could move the stick at high speed without using two hands as I normally would in the D."

 

[drgondog]

Some numbers you might find interesting.

_____________P-51B____________________P-51D______________________NOTE
15,000 ft_______________________________90°/sec at 210 knots IAS_____ no wing guns, ballast in fuselage for CG limit
10,000 ft_____98°/sec at 260 knots IAS____71°/sec at 200 knots IAS_____ both AC with normal fuel and military load, post-war tests

re P-51D Stick Forces

from a post-war test done by flight test pilots:

__In the course of conducting an analytical comparison of the Mustang, Hellcat, Thunderbolt and Corsair ". . . test pilots measured the [P-51D] Mustang stick force at 70 pounds for a 4G turn and about 90 for a 5G turn at maximum level-flight speed, about 240 kias for their test. Those are estimates, since their force gauge went to only 60 pounds."

__The unanimous view of the test pilots was ". . . the [P-51D] Mustang was a two-handed airplane in which prolonged hard maneuvering was extremely tiring"

from Jeff Ethell, air show pilot with thousands of hours flight in different aircraft and a lot of them in the P-51:

__When flying the P-51A "I could move the stick at high speed without using two hands as I normally would in the D."

As in every conversation about Mustang Roll performance - 'it depends'. The P-51A had no DFF and no Reverse Rudder boost, but did have only 10 degrees +/- aileron travel. The P-51B had 15 +/-, often rigged for 12+/-, had DFF and Reverse Rudder Boost installed in the field after D-Day. The early D configuration was same as P-51B/C.

For no DFF and no Reverse Rudder Boost configuration, both the B and D (and A) were incredibly responsive in Roll. After installation of both features high speed rolls required more force.

John Muszala II, Pacific Fighters, is the Only pilot I know of that has flown the NA-73, NA-99 (P-51A), NA-104 (P-51B) and NA-109 (P-51D) (and Spit and Tempest and Bf 109). He states unequivocally that the B w/o Reverse Rudder Boost and 15 degrees ailerons is the most responsive in roll of all the warbirds he has flown except the Yak 3.

The XP-51 41-038 (NA-7) was extensively tested in roll and in act NACA used several ailerons (Wedge, Cusped) and several aileron throws (up to 20 degrees) and extracted optimum results with 12-16 degrees. NAA was also testing roll mods in NA-83 which confirmed NACA results. Those results were first installed in NA-102 P-51B-1-NA, and improved upon in NA-103/104 and also NA-109.

The P-51H discarded the Reverse Rudder Boost, retained a smaller DFF, and went back to 10 degrees with a larger aileron area to improve slightly over the P-51B/D w/o Reverse Rudder Boost and 12 degrees aileron throw.

 

[ThomasP]

Hey drgondog,

The roll rate chart in the NACA TR No.868 report from 1947 is a gathering of actual measurements of the various aircraft's roll rates. It says that in the report text, plus I found the following RAE(?) chart from late-1943 (you can just barely make out the year in the upper left corner) from which the Spitfire, Fw190, Mustang, and Typhoon roll rates were taken. The Mustang was the Mustang Mk I NA-73 model (aka XP-51/P-51).

The NACA report also shows the P-51B-1-NA roll rate. The curve indicates that the aileron deflection has been increased (presumably to the 15° you mentioned, hence the hump in the curve and the significantly higher roll rate at slower speeds).

Do you know which of the mods you mention above would give that curve?

 

[drgondog]

Hey drangondog,

The roll rate chart in the NACA TR No.868 report from 1947 is a gathering of actual measurements of the various aircraft's roll rates. It says that in the report text, plus I found the following RAE(?) chart from late-1943 (you can just barely make out the year in the upper left corner) from which the Spitfire, Fw190, Mustang, and Typhoon roll rates were taken. The Mustang was the Mustang Mk I NA-73 model (aka XP-51/P-51).

The NACA report also shows the P-51B-1-NA roll rate. The curve indicates that the aileron deflection has been increased (presumably to the 15° you mentioned, hence the hump in the curve and the significantly higher roll rate at slower speeds).

Do you know which of the mods you mention above would give that curve?

View attachment 595966

Several comments, Thomas - but first an answer. 'Deflection for B-51B-1 as tested - unknown'. ALL P-51B-1 left the factory rigged for 12 degrees.

Comments, The wind tunnel examinations discussed also highlighted several variables hard to properly quantify, including torsional stiffness of the wing.

That said a.) P-51B-1 was the first +/- 15degree deflection rigging. The P-51B-1 wing and aileron/wing attach were improved from two hinged sealed/balanced aileron to stiffer wing (from earlier P-51A which was stiffer than A-36 and all preceding Mustangs). When both the aileron changed to improved seal/3 position attach hinges (P-51B-5/C and the load carrying ability was upgraded to 1000 per rack (P-51D) the wing was at peak until P-51H.

I'm unclear regarding the XP-51 Roll Rate figures presented - think they were from cusped ailerons. From March 1942 through May 1942, the XP-51 was extensively dive tested and roll tested including examination of wedge vs cusped and roll rates developed for 10, 15, 17 and 20 degrees. NAA was conducting similar tests and concluded the optimal rigging required at least 12 degrees for optimal combination of low speed roll authority combing with improved high speed rates.

I've read the report in the past - but for first time did not notice that the NAA/NACA 45-100 airfoil was Not shown in the tables. I could have overlooked it, but..

 

[BiffF15]

Several comments, Thomas - but first an answer. 'Deflection for B-51B-1 as tested - unknown'. ALL P-51B-1 left the factory rigged for 12 degrees.

Comments, The wind tunnel examinations discussed also highlighted several variables hard to properly quantify, including torsional stiffness of the wing.

That said a.) P-51B-1 was the first +/- 15degree deflection rigging. The P-51B-1 wing and aileron/wing attach were improved from two hinged sealed/balanced aileron to stiffer wing (from earlier P-51A which was stiffer than A-36 and all preceding Mustangs). When both the aileron changed to improved seal/3 position attach hinges (P-51B-5/C and the load carrying ability was upgraded to 1000 per rack (P-51D) the wing was at peak until P-51H.

I'm unclear regarding the XP-51 Roll Rate figures presented - think they were from cusped ailerons. From March 1942 through May 1942, the XP-51 was extensively dive tested and roll tested including examination of wedge vs cusped and roll rates developed for 10, 15, 17 and 20 degrees. NAA was conducting similar tests and concluded the optimal rigging required at least 12 degrees for optimal combination of low speed roll authority combing with improved high speed rates.

I've read the report in the past - but for first time did not notice that the NAA/NACA 45-100 airfoil was Not shown in the tables. I could have overlooked it, but..

Bill,

Do you have any pictures of the "cusped / wedged" ailerons, or the improved seal/3 position attachment hinges?

Cheers,
Biff

 

[Mike Williams]

Do you have any pictures of the "cusped / wedged" ailerons, or the improved seal/3 position attachment hinges?

Cheers,
Biff

http://www.wwiiaircraftperformance.org/mustang/naca-l-550.pdf

 

[BiffF15]

http://www.wwiiaircraftperformance.org/mustang/naca-l-550.pdf

Excellent and thanks Mike! Very detailed report!

Cheers,
Biff

 

[drgondog]

Bill,

Do you have any pictures of the "cusped / wedged" ailerons, or the improved seal/3 position attachment hinges?

Cheers,
Biff

Biff - download the report, it has examples of both the wedge and the cusped ailerons in the front 1/3 of the report. Ditto on balanced/sealed (last 1/3?) but I didn't see reference to 3 hinge P-51B-5 (&Subs) modification.

 

[BiffF15]

Biff - download the report, it has examples of both the wedge and the cusped ailerons in the front 1/3 of the report. Ditto on balanced/sealed (last 1/3?) but I didn't see reference to 3 hinge P-51B-5 (&Subs) modification.

Thanks and I do have it open, currently about half way through the text. Do you know where the combat units netted out (which setting they used) and was there deviation from that?

Cheers,
Biff

 

[ThomasP]

Hey drgondog,

Thank you for the info.

Hey Mike,

Thank you for the link.

 

[drgondog]

Biff - rigging from Factory was +/- 12 degrees

 

[drgondog]

Hey drgondog,

The roll rate chart in the NACA TR No.868 report from 1947 is a gathering of actual measurements of the various aircraft's roll rates. It says that in the report text, plus I found the following RAE(?) chart from late-1943 (you can just barely make out the year in the upper left corner) from which the Spitfire, Fw190, Mustang, and Typhoon roll rates were taken. The Mustang was the Mustang Mk I NA-73 model (aka XP-51/P-51).

The NACA report also shows the P-51B-1-NA roll rate. The curve indicates that the aileron deflection has been increased (presumably to the 15° you mentioned, hence the hump in the curve and the significantly higher roll rate at slower speeds).

Do you know which of the mods you mention above would give that curve?

View attachment 595966

I'm not sure how to answer your question. The NACA report (By memory) is based on calculations - not flight tests, but I will pull it.

I devote a couple of pages (124/125) in my book on this specific subject (evolution of NAA and NACA testing in summer 1942 to perform design improvements for roll rate).

First note - the XP-51 Roll rate was for +/- 10 degrees. The P-51B-1 would be for the two hinge design and (I suspect 12 degrees) prior to stiffening the aft spar and having the same hanger/seal as the P-51A. The P-51A and B-1 aft spar/hinge/seal was improved on the B-5/C-1 and D/K with better aileron seal and three aileron hinges. John Muszala II (Pacific Fighters (who has flown all the different Mustangs except the G/J) states that the P-51B-5 with 15 degrees and without Reverse Rudder Boost and DF is the most responsive of all the Merlin Mustangs.

If you have the report handy, perhaps you can validate 'data vs actual test' recollection I posed.

FYI I do know that ALL Mustang warbird operators that I discussed this with, current and past (except Muszala) rigged their B/C/D/K with 10 degrees. Many that I discussed this topic with did not even know of the 10/12/15 rigging. My father had his rigged at both 12 and 15 (12 for P-51C-10 and 15 for P-51D's -all because the installation of the DF and Reverse Rudder Boost reduced roll rates.

 

[ThomasP]

Thanks for the answer drgondog,

I will check the report.

 

[IdahoRenegade]

There are a couple of things to add to Rochie and Bobbysocks post. The Spitfire and especially the Hurricane were game changers in 1940, without them it is possible there would be no place for any P-51s to fly from. The real game changer was US industry producing 4 engine bombers, without the bombers what threat is a P-51 to German industry and infrastructure? In the action described by Bobbysocks of his father, the Spitfire was doing what it did throughout the war, protecting the UK with all its bases which included USAAF bases. In these discussions "time is of the essence". In 1940 the P-51 didn't exist, but even if it did it would not be a better interceptor than a Hurricane or Spitfire with a 1940 Merlin engine. It may have been faster than both when it got off the ground and up to altitude, but it weighed a ton more and with only 1000BHP that is a massive extra weight to haul up to 25,000ft you cannot zoom climb until you have first climbed.

All true, but, had there been a P-51 equipped with an equivalent Merlin to the Spit-the Battle of Britain could have ended much sooner with much less damage to England-if any at all. The Mustang had the range to hit any airfield the BF-109s could fly from, with a long loiter time as necessary over occupied France or Belgium. The losses on the ground may well have forced Germany to pull their fighters back too far to have the range to even reach England. Coulda-woulda, since there was no such animal.

In the point defense roll, the Spit is likely the better aircraft, especially with it's rate of climb. But-the Mustang could do the job. Perhaps not as well with it's limitations, or perhaps better since the range and endurance meant it could hit attacking aircraft further away, and stay in the fight a lot longer (though ammo load would likely be the limiting factor). But it could do the job of a point defense fighter. The Spit could not do the job of a long-range escort fighter.

 

[nuuumannn]

Let's not forget that what was available to the RAF in 1940 was very different to what was available two years later when the Mustang I and Spitfire IX entered service. Much has to happen between the two time periods.

Let's also not forget that the Mustang wasn't designed as an escort fighter. When it first entered service in January 1942 it was powered by the Allison V-1710, equipping RAF squadrons as a tactical reconnaissance aircraft.

 

[Shortround6]

All true, but, had there been a P-51 equipped with an equivalent Merlin to the Spit-the Battle of Britain could have ended much sooner with much less damage to England-if any at all.

Not really, A BoB Spit used a Merlin that was allowed 880hp for take-off. It was allowed 2600rpm and 6 1/4lbs boost for climb.
The Merlin XII in the Spit MK II was somewhat better.
The Allison in the first British Mustangs was allowed 1150hp for take-off. It was also good for around 1040hp at just over 14,000ft?
Merlin III was good for 1030hp at 16,250ft (both are without RAM)

Sorry, A Merlin III in an 8,000lb aircraft is not going to give sparkling performance.

 

[wuzak]

All true, but, had there been a P-51 equipped with an equivalent Merlin to the Spit-the Battle of Britain could have ended much sooner with much less damage to England-if any at all.

May as well say that had the Spitfire XIV been available for the BoB it would have ended much sooner.

 

[GrauGeist]

Why not really spin the wheel of fantasy and suggest that if the Atomic armed B-29s were available in 1940, WWII would have lasted a year at best and Japan would have strongly reconsidered their position with the US...

 

[fubar57]

.....and throw in some P-39s as B-29 escorts; should only need a handful to cover the bomber stream

 

[33k in the air]

The best is the USN Nimitz being transported back in time to just hours before Pearl Harbor.