Notes:

INITIAL IMPRESSIONS

Both the Thunderbolt and Mustang differed greatly in terms of design, but despite their differences, when it came to combat, both would emerge as near-equal matches in many regards.

These two aircraft had very different power plants. The Mustang most famously used the Rolls Royce Merlin – a 27 litre V-12 engine – whilst the P-47 used the radial Pratt and Whitney R-2800 – the same engine used on the Corsair and Hellcat in the pacific.

For the sake of argument, let’s ignore the earlier versions of the Mustang, as these versions were powered by an early model of the Allison V-1710. This V-12 engine had poor high altitude performance and simply could not compete with Luftwaffe aircraft. The P-51B and C variants, overcame this with the Merlin engine. This engine was modified and license built by the US as the Packard V-1650, which was fitted into the P-51D, which arrived in 1944. The final version worth considering was the P-51H, which outperformed the D model in many areas, however these aircraft – 2000 of which were ordered in anticipation for a land invasion of Japan – never saw combat in world war 2.

So our comparison here will focus primarily on the performance of both the P-51D and the P-47D variants.

COMBAT RECORD

Let’s start our comparison with the combat records of both aircraft. Both entered service in 1942, serving with the RAF in various capacities. Generally, both aircraft were used to escort bombers on long range missions into enemy territory. This was initially the primary role of the Thunderbolt, but would later be handed off to the Mustang.

As far as kill count is concerned, the Mustang reigns supreme, with somewhere between 4200 and 4950 claimed victories, unmatched by any other US aircraft in the European theatre. The Thunderbolt, on the other hand, held between 2600 and 3700 claimed victories, significantly lower, but nevertheless an impressive record.

The kill ratios of both aircraft fall behind that of the nearly 20:1 win/loss ratio of the F6F Hellcat in the Pacific, (and it must be said that the kill ratios of the Thunderbolt and Mustang are heavily disputed). Most claims pin the Mustangs kill ratio at 10:1, and the Thunderbolts ratio at 4.6:1. Much of this uncertainty comes down to disputes over air victory claims. The lower ratios of both aircraft, compared to the 11:1 kill ratio of the Corsair and near 20:1 ratio of the Hellcat in the Pacific, could be attributed to the higher number of experienced Luftwaffe pilots, although this is pure conjecture.

As mentioned in the previous Corsair verses Hellcat comparison, a “kill count” must be considered within the operational context. In the Pacific theatre, for example, the number of experienced Japanese pilots decreased as the war dragged on. The same was the case for the Germans, who – despite possessing an overwhelming majority of World War 2 Aces – were short on experienced pilots after six long years of warfare. While both aircraft initially served as long range support for bombers based in England in 1942, over time, the Mustang would become the primary long range support fighter for such missions, while the Thunderbolt would focus on other roles. And it is within this rather complex context that we compare the Thunderbolt and Mustang.

PERFORMANCE

Most test results place the P-51Ds climb rate from sea level at around 3400 ft/min, whilst evaluation of the late war P-51H model saw that number increase to 5120 ft/min, perhaps the best climb rate of any American prop aircraft during the war. Surprisingly, evaluations demonstrated that the earlier P-51B model actually outperformed the D model, with a climb rate of 4400 ft/min.
Early P-47D variants had a climb rate of 2300 ft/min, whilst some later D variants achieved climb rates of up to 3300 ft/min. These late war P-47D’s demonstrated an increase in climb rate performance with an increase in altitude, peaking at around 10,000 feet. The P-51D, in contrast, held maximum climb rate potential at sea level, which immediately began to drop off above 4000 feet.

In terms of speed, both aircraft were exceptionally fast within their class, capable of surpassing 400mph. This was achieved at higher altitudes, and in most cases higher speeds were necessary for the aircraft to perform optimally.  The P-51B was known to be capable of reaching 450mph, achievable at around 28,000 feet. The P-51D model performed similarly, with a maximum speed of 440mph, which it could achieve slightly lower, at 24,000 feet.  The Thunderbolt was almost equally matched. Late-war P-47Ds were clocked at achieving 445mph, albeit at an even lower altitude of 23,000 feet. The one exception was the later N model of the Thunderbolt, which was claimed to have been capable of reaching 470 mph under the right conditions.  At sea level the Mustang held the advantage, but not by much. P-51s were clocked at reaching almost 380mph, whilst P-47Ds maxed out at around 345mph. If anything, this latter comparison is more important when comparing P-51 variants, since – despite losing out to the B model at higher altitudes – the later P-51D held the speed authority closer to sea level, where dogfights were more likely to descend to as they went on.  At high altitudes exceeding 35,000 feet, both aircraft were basically equal, capable of 400mph, although there has been debate over the an apparent advantage the P-47 N model had if it was running proper 150 octane fuel.  Thus, in terms of speed, it could be said that both aircraft were equally matched if we smooth out slight variations in altitude performances.

Both aircraft in this respect also retained similar service ceilings. The P-47D could operate up to 42,000 feet, whilst the P-51D could operate at just over 41,000 feet. Again, both aircraft on an equal footing.

However, the range of the two aircraft differed significantly. Although both served as long-range escorts during bombing missions over Europe, the Mustang’s capability was practically unmatched. The Thunderbolt could reach near 900 miles at optimal altitude, and could be outfitted with large external drop tanks increasing its range to somewhere around 1400 miles, and later with tanks extending the range to 1900 miles. In contrast, the P-51D could fly up to 1200 miles just on internal fuel, however it was often fitted with external tanks, and could fly just over 1600 miles when fully fuelled. However, later war P-47N variants were improved to match the P-51, in some cases capable of flying 2000 miles.

Maneuverability is where the aircraft differ perhaps the greatest. Whilst the Thunderbolt certainly wasn’t slack in a dogfight, the Mustang would outperform it by a large margin when it came to roll and turn rates. The P-47 was simple too heavy to compete in this regard, weighing more than any other single seat piston aircraft produced by the US at the time.

This was backed up by pilot testimony. Many pilots who flew the P47 were later retrained to fly the P51. And, many of these pilots consistently listed the Mustang as their preferred aircraft. The primary factor for this was the Mustangs improved manoeuvrability and speed, which allowed it to compete with later war German aircraft such as the BF-109 K4. On the other hand, the smaller number of pilots who preferred the P-47 pinned this down to the Thunderbolts safety.

When it came to the safety factor, the Thunderbolt was more robust than the Mustang. The Thunderbolt was known to be capable of taking multiple hits without compromising the aircraft, while the Mustang was far more vulnerable. Many say this was due to the Thunderbolts use of an air-cooled radial engine. The Mustang relied on liquid cooling, thus any hits to the coolant lines would result in leaks, and soon after, the overheated engine would seize. The Thunderbolt’s airframe was a stronger overall build, and pilots recall the aircraft was better suited for emergency landings. The lighter Mustang, however, had a higher chance of breaking apart on ground impact, and also flipping over the nose when the air intake under the fuselage hit ground or water. The Thunderbolt had wider and stronger landing gear with extreme heavy duty tires, making it easier to land and safer on makeshift airstrips.

Some final considerations include armament. Both aircraft were armed with 50 caliber machine guns. This was the standard for the US air force, and would remain as such until the Korean War. The P-51D had six such 50 caliber machine guns, whilst the P-47D had eight. The Thunderbolt also carried twice the amount of ammo – 3400 rounds – whilst the Mustang carried 1800. It is hard to gauge how much of a difference the increased armament of the Thunderbolt made, although it likely helped. By the end of the war, many German aircraft were using combinations of machine guns and cannons. The latter could knock out aircraft with a single hit. Machine guns were limited, and could sometimes take multiple bursts to take out an enemy. Thus, more guns firing simultaneously increased the potential damage done by a single on-target burst of rounds.

The Thunderbolt was also far more capable when it came to bombing. Its larger airframe allowed it to carry two 1000 pound bombs – one on each wing – and a 500 pound bomb in the centre, thus allowing for 2500 pounds of explosive. Although this required water injection and a long runway for takeoff, this did give the Thunderbolt several advantages over the Thunderbolt when it came to bombing; that being, it kept pilots safer from ground fire, could deliver more firepower per sortie, Albeit at a shorter range than the P-51.

CONCLUSION

In the final analysis we find both aircraft were very different, demonstrating strengths in differing roles. In the years following World War 2, the P-51 (later called the F-51) performed well as a fighter, escort, and light strike aircraft in the early days of the Korean War, but was eventually tasked for close air support missions. In the close air support role the Mustang struggled, being prone to ground fire damage. At the time, pilots believed that the P-47 Thunderbolt would serve this role perfectly, given its heavy armour and larger armament capacity. However, their requests to fly the aircraft would be denied, and Thunderbolts would not see the Korean War. One cannot help to think that the Thunderbolt would have thrived such a role, leaving the Mustangs for fighter escort missions.

Nevertheless the Douglas A-1 Skyraider, a heavy prop aircraft built at the end of World War 2, was engaged in the close air support role, both in Korea and later in Vietnam, fulfilling the role well.

If we were to draw a final conclusion, it would not be unreasonable to suggest that during World War 2 the P-51 Mustang was the better aircraft over all. Whilst the Thunderbolt was safer and could go further with more, the Mustang was the more agile aircraft that could get in a fight and kill the enemy at twice the rate of a Thunderbolt. Killing before being killed was a supremely motivating priority, and given the Luftwaffe’s aerial arsenal the Mustang offered exceptional performance for the task at hand.

This is not to dismiss the importance of the Thunderbolt. It was a remarkable aircraft, serving its role well in world war 2, having achieved thousands of victories, and helping secure allied victories throughout Southern Europe and the Mediterranean.