Comparing the P-51B with the P-47D-10 and the P-38J-5

In his book Mustang, The Operational Record, Robert Jackson quotes a report produced by the Army Air Forces Board which describes some results of comparative trials between the P-51B and several other USAAF aircraft:

The P-51B, from sea level to 11,000 ft, is some seven to ten miles per hour slower than the P-51A which is the fastest fighter at this altitude. Between 14,000 and 22,000 ft, the P-51B is about fifteen to twenty mph faster. From 22,000 ft the P-51B, in high blower, widens this speed advantage up to seventy-five mph at 30,000 ft.

From sea level, the P-51B gradually gains on the P-38J and the P-47D until, at 16,000 ft, it has a speed of about 420 mph which is about ten mph faster than the P-38J and about 20 mph faster than the P-47D. Above 27,000 ft, the P-51B can no longer get war emergency power, but its speed of about 430 mph at 30,000 ft is equal to that of the P-47D and about twenty mph faster than the P-38J, both using war emergency power. The P-51B is capable of 400 mph at 40,000 ft.

The P-51B is by far the best climbing aircraft of all current American fighters. It takes about 4.5 minutes to get to 15,000 ft as against five minutes for the P-38J and about seven minutes for the P-47J¹. The P-51B maintains a lead of about .5 minute over the P-38J to 30,000 ft and reaches that altitude in about eleven minutes which is about 6.5 minutes faster than the P-47D.

In zooming the P-51B with the P-47D from level flight at cruising and high speeds, and from high speeds out of dives, the P-51B gains speed rapidly and leaves the P-47D far behind. In zooming the P-51B with the P-38J, from level flight at cruising speed, the fighters climb evenly at the start. However, the P-51B falls off while the P-38B² keeps climbing. In zooms from high speeds (425 indicated air speed) the P-51B pulls away from the P-38J and it soon ends considerably higher.

The diving characteristics of the P-51B are superior to those of any other fighter plane. It is exceptionally easy to handle and requires very little trimming. The P-51B dives away from all other fighters except the P-47D, against which the P-51B looses several hundred feet in the initial pushover and then holds that position, apparently neither gaining nor losing distance.

The new seal-balanced ailerons of the P-51B give the fighter a faster roll at all speeds than any other fighter except the P-47D with which it is equal at cruising speeds.

The search view of the P-51B is better than in the P-51A but is still obstructed above, to both sides, and to the rear, by the canopy construction. The view forward over the nose is considerably improved over the P-51A by the relocation of the carburetor intake scoop, the elimination of the clear view panel on the left side of the windshield, and lowering of the nose of the engine one and one-half degrees.

The fighting qualities of the P-51B were compared with those of the P-47D-10 and the P-38J-5 and, briefly, with the P-39N-0 and the P-40N. The only maneuver the P-39 and P-40 have that is superior to the P-51B is a slight advantage in a turning circle. In all other maneuvers, as well as performance, they are both far inferior. The P-51B has good performance at all altitudes, but above 20,000 ft the performance improves rapidly, and its best fighting altitude is between 25 and 35,000 ft. The rate of climb is outstanding, with an average of about 3,000 ft per minute from sea level to 25,000 ft. Above 20,000 ft, the overall fighting qualities of this aircraft are superior to those of all other types used in the trials.

In the final paragraph we discover the Thunderbolt against which the P-51B was flown. The Block 10 Thunderbolts were generally equipped with the Pratt & Whitney R-2800-63 water injected engine and used the General Electric C-23 turbosupercharger. The -63 engine/C-23 turbo combination had the following ratings:

Takeoff:  2000 HP @2700 RPM
Normal:   1625 HP @2500 RPM @25000 ft
Military: 2000 HP @2700 RPM at all altitudes through 25000 ft
WEP:      2300 HP @2700 RPM

It's worthy of note that the "paddle blade" propeller was not introduced on the P-47D until Block 22. By all accounts, this propeller significantly improved the climb performance of the Thunderbolt. It is also worth noting that the roll rate of the P-47 improved as the aircraft design evolved; the P-47N, with it's longer wing and squared-off wing tips, actually had a better roll rate than the D models.

¹This might be a typo. It's probably P-47D.
²This might be a typo. It's probably P-38J.