The McDonnell XP-67, nicknamed the “Moonbat,” was an ambitious World War II experimental fighter developed by McDonnell Aircraft Corporation. Designed in the early 1940s for the United States Army Air Forces, the XP-67 featured an advanced blended aerodynamic design intended to reduce drag and dramatically increase speed.
Although only one prototype was built and the project was ultimately cancelled, the XP-67 remains one of the most unique and futuristic aircraft concepts of the WWII era.
McDonnell Douglas XP-67 Moonbat
Overview of the McDonnell Douglas XP-67
The XP-67 was conceived as a high-speed, twin-engine interceptor fighter capable of competing with and surpassing contemporary aircraft in climb rate, speed, and heavy armament. Its smooth, flowing fuselage and blended engine nacelles gave it a striking, almost sci-fi appearance — earning the nickname “Moonbat.”
Key Goals of the XP-67 Program:
Achieve exceptional aerodynamic efficiency
Reach top speeds above 470 mph (756 km/h)
Deliver heavy firepower for bomber interception
Compete with other advanced WWII fighter projects
Design and Aerodynamics
One of the most distinctive features of the XP-67 was its blended wing-fuselage layout. Unlike traditional aircraft with clearly separated engine nacelles and wings, the XP-67 integrated these elements into a seamless shape to minimize drag.
Unique Design Features:
Smooth, curving fuselage contours
Engine nacelles blended into wing roots
Laminar flow airfoil sections
Pressurized cockpit (planned in later versions)
Heavy nose-mounted armament configuration
The aircraft was powered by two Continental XIV-1430 inverted V-12 engines. However, engine reliability issues would become a major problem during testing.
XP-67 Specifications (Prototype)
Specification
Details
Role
Experimental fighter/interceptor
Manufacturer
McDonnell Aircraft
First Flight
January 6, 1944
Engines
2 × Continental XIV-1430 V-12
Crew
1
Armament (planned)
6 × 37 mm cannons (proposed)
Maximum Speed (projected)
~472 mph (759 km/h)
Note: Many performance figures were projected, as the prototype never achieved full expected performance.
Flight Testing and Challenges
The XP-67 made its maiden flight in early 1944. However, it quickly became clear that the aircraft would not meet its ambitious performance targets.
Major Issues Encountered:
Engine overheating and reliability problems
Structural and vibration concerns
Lower-than-expected speed performance
Weight increases beyond original estimates
In September 1944, an engine fire during testing severely damaged the prototype. Shortly afterward, the program was officially cancelled by the U.S. Army Air Forces.
Why the XP-67 Was Cancelled
Several factors led to the cancellation of the XP-67 project:
Engine Limitations – The Continental XIV-1430 engines failed to produce reliable high power.
Performance Shortfall – The aircraft did not reach its projected top speed.
Rapid Advancement of Jet Technology – By 1944, jet aircraft such as the Bell P-59 Airacomet and the German Messerschmitt Me 262 signaled the future of air combat.
Shifting War Priorities – Resources were redirected toward more promising designs.
As a result, the XP-67 never entered production.
Historical Significance
Despite its failure, the XP-67 played an important role in aviation history:
Demonstrated early experimentation with advanced aerodynamic blending
Reflected the growing desire for higher speeds and heavier armament
Marked McDonnell’s early entry into military aircraft development
Contributed to the company’s later success in jet fighters
The XP-67’s futuristic appearance continues to capture the imagination of aviation historians and enthusiasts.
Legacy of McDonnell Aircraft
After World War II, McDonnell Aircraft transitioned into jet development, eventually producing legendary aircraft such as:
F-4 Phantom II
F-15 Eagle
In 1967, McDonnell Aircraft merged with Douglas Aircraft to form McDonnell Douglas, which later merged with Boeing in 1997.
The XP-67 stands as an early experimental milestone in that corporate lineage.
Conclusion
The McDonnell XP-67 Moonbat remains one of the most visually distinctive and ambitious fighter prototypes of World War II. Although plagued by engine problems and ultimately overtaken by jet technology, its advanced aerodynamic concepts showcased McDonnell’s forward-thinking engineering approach.
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Frequently Asked Questions (FAQs)
What was the nickname of the XP-67?
It was called the “Moonbat” because of its unusual, bat-like blended wing shape.
How many XP-67 aircraft were built?
Only one prototype was constructed.
Did the XP-67 see combat?
No. The aircraft remained experimental and was cancelled before operational deployment.
Why is the XP-67 important?
It represents an innovative aerodynamic experiment during WWII and highlights the technological transition from piston fighters to jet aircraft.