The McDonnell XF-85 Goblin was one of the most unusual fighter aircraft ever built. Developed by McDonnell Aircraft Corporation in the late 1940s for the United States Air Force, the XF-85 was designed as a “parasite fighter” — a tiny jet aircraft that could be carried inside a bomber and deployed mid-air to defend it from enemy fighters.
Although the project was ultimately cancelled, the XF-85 Goblin remains a fascinating chapter in aviation history and Cold War innovation.
McDonnell Douglas XF-85 Goblin
What Was the McDonnell XF-85 Goblin?
The McDonnell XF-85 Goblin was conceived during the early Cold War era when long-range bombers such as the Convair B-36 Peacemaker needed protection deep inside enemy territory. Escort fighters at the time lacked sufficient range to accompany bombers on intercontinental missions.
To solve this problem, engineers proposed a compact jet fighter that could:
Be stored inside a bomber’s bomb bay
Launch in mid-air
Engage enemy interceptors
Return and dock with the bomber before landing
This revolutionary concept gave birth to the XF-85.
Design and Engineering Innovation
The XF-85 was extremely compact, measuring just under 15 feet (4.5 meters) long. Its small size allowed it to fit inside the B-36’s bomb bay.
Key Design Features:
Egg-shaped fuselage for compact storage
Foldable wings for internal carriage
Retractable nose hook for trapeze docking system
Single turbojet engine (Westinghouse J34)
Four .50 caliber machine guns (planned armament)
Instead of traditional landing gear, the aircraft used a steel skid beneath the fuselage for emergency landings.
How the Parasite Fighter System Worked
The XF-85 would be lowered from the bomber using a trapeze mechanism. After completing its mission, the pilot would carefully maneuver back under the bomber and hook onto the trapeze mid-air.
While innovative in theory, the docking process proved extremely difficult in practice. Turbulence behind the bomber created unstable air currents, making reattachment challenging.
XF-85 Specifications
Specification
Details
Role
Parasite fighter prototype
First Flight
August 23, 1948
Engine
1 × Westinghouse J34 turbojet
Crew
1
Maximum Speed
~648 mph (1,043 km/h)
Range
Limited (dependent on host bomber)
Armament (planned)
4 × .50 cal machine guns
Only two prototypes were built for testing.
Flight Testing and Challenges
Flight tests revealed several issues:
Severe turbulence when attempting mid-air docking
Limited fuel capacity and endurance
Rapid advances in long-range escort fighters
Development of aerial refueling technology
Although test pilots successfully flew the Goblin, the docking process remained hazardous and inconsistent.
Ultimately, the program was cancelled in 1949.
Why the XF-85 Was Cancelled
Several factors led to the cancellation of the XF-85 project:
Aerial Refueling Advances – Air-to-air refueling made long-range escort fighters feasible.
Improved Jet Fighters – Aircraft like the North American F-86 Sabre offered superior performance and flexibility.
Operational Complexity – The parasite fighter concept proved too risky and impractical.
As a result, the U.S. Air Force shifted its focus toward conventional jet fighters and refueling strategies.
Historical Significance
Despite its short lifespan, the XF-85 Goblin represents a bold engineering experiment during the dawn of the jet age.
Its Importance Includes:
Demonstrating early Cold War innovation
Exploring unconventional air defense concepts
Influencing later aircraft carrier and drone deployment ideas
Marking an early milestone in McDonnell’s jet development history
The Goblin showcased the willingness of engineers to challenge traditional aircraft design in pursuit of strategic advantage.
Where Is the XF-85 Today?
One surviving XF-85 prototype is displayed at the National Museum of the United States Air Force in Dayton, Ohio, where visitors can see this unique aircraft up close.
Conclusion
The McDonnell XF-85 Goblin stands as one of the most unusual and daring fighter aircraft concepts ever tested. Designed to defend strategic bombers during the early Cold War, it ultimately became obsolete due to rapid advancements in aerial refueling and long-range jet technology.
Even though it never entered service, the XF-85 remains a remarkable symbol of post-World War II aerospace innovation and bold experimentation.
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Frequently Asked Questions (FAQs) - McDonnell Douglas XF-85 Goblin
How many McDonnell XF-85 Goblins were built?
Two prototypes were constructed for testing.
Did the XF-85 ever enter combat?
No. The aircraft remained experimental and was never operationally deployed.
Why was it called a parasite fighter?
Because it was designed to be carried by and depend on a larger “host” bomber aircraft.
Was the concept completely abandoned?
While the parasite fighter concept ended, similar ideas resurfaced in drone deployment and airborne launch systems.