XF-85 Goblin
Encyclopedia
The McDonnell XF-85 Goblin was an American prototype fighter aircraft
conceived during World War II
by McDonnell Aircraft
. It was intended to be carried in and deployed from the bomb bay
of the giant Convair B-36
bomber as a parasite fighter. The XF-85's intended role was to defend bombers from hostile interceptor
s, a need demonstrated during World War II. Two prototypes were constructed before the program was terminated.
The XF-85 was a response to a United States Army Air Forces
(USAAF) requirement for a fighter to be carried within the Northrop XB-35
and B-36, then under development. It was a diminutive jet aircraft featuring a distinctive egg-shaped fuselage
and a forked-tail stabilizer
design. The prototypes were built and underwent testing and evaluation in 1948. Flight tests showed promise in the design, but the aircraft's performance was inferior to the jet fighters it would have been facing in combat, and there were difficulties in docking. The XF-85 was swiftly canceled, and the prototypes were thereafter relegated to museum exhibits. The 1947 successor to the USAAF, the US Air Force (USAF), continued to examine the concept of parasite aircraft under Project MX-106 "Tip Tow"
, Project FICON
and Project "Tom-tom"
following the cancellation.
was still considered risky and technologically difficult. Pilot fatigue had also been a problem during long fighter escort missions in Europe and the Pacific, giving further impetus to innovative approaches.
The USAAF considered a number of different options including the use of remotely piloted vehicles before choosing parasite fighters as the most viable B-36 defense. The concept of a parasite fighter had its origins in 1918, when the Royal Air Force
examined the viability of Sopwith Camel
parasite fighters operating from R23 airships. In the 1930s, the U.S. Navy had a short-lived operational parasite fighter, the Curtiss F9C Sparrowhawk, aboard airships Akron
and Macon
. Starting in 1931, aircraft designer Vladimir Vakhmistrov conducted experiments in the Soviet Union
as part of the Zveno project
where up to five fighters of various types were carried by Polikarpov TB-2
and Tupolev TB-3
bombers. In August 1941, these combinations flew the only combat missions ever undertaken by parasite fighters – TB-3s carrying Polikarpov I-16SPB
dive bomber
s attacked the Cernavodă bridge
and Constantsa docks, in Romania
. After that attack, the squadron, based in the Crimea, carried out a tactical attack on a bridge over the river Dnieper at Zaporozhe, which had been captured by advancing German troops. Later in World War II, the Luftwaffe
experimented with the Messerschmitt Me 328
as a parasite fighter, but problems with its pulsejet engines could not be overcome. Other late-war rocket
-powered parasite fighter projects such as the Arado E.381 and Sombold So 344 were unrealized "paper projects".
On 3 December 1942, the USAAF sent out a Request for Proposals (RfP) for a diminutive piston-engined fighter. By January 1944, the Air Technical Service Command
refined the RfP and in January 1945, the specifications were further revised in MX-472 to specify a jet-powered aircraft. Although a number of aerospace companies studied the feasibility of such aircraft, McDonnell was the only company to submit a proposal to the original 1942 request and later revised requirements. The company's Model 27 proposal was completely reworked to meet the new specifications.
The initial concept for the Model 27 was for the fighter to be carried half-exposed under the B-29, B-35 or B-36. The USAAF rejected this proposal, citing increased drag, and hence reduced range for the composite bomber-fighter configuration. On 19 March 1945, McDonnell's design team led by Herman D. Barkey, submitted a revised proposal, the extensively redesigned Model 27D. The smaller aircraft had an egg-shaped fuselage, three fork-shaped vertical stabilizers, horizontal stabilizers with a significant dihedral, and 37° swept-back folding wings to allow it to fit in the confines of a bomb bay. The diminutive aircraft measured 14 in 10 in (4.52 m) long; the folding wings spanned 21 ft (6.4 m). Only a limited fuel supply of 112 US gal (93.3 imp gal; 424 l) was deemed necessary for the specified 30-minute combat endurance. A hook was installed along the aircraft's center of gravity; in flight, it retracted to lie flat in the upper part of the nose. The aircraft had an empty weight just short of 4000 pounds (1.8 t). To save weight, the fighter had no landing gear. During the testing program, a fixed steel skid under the fuselage and spring-steel "runners" at the underside of the wingtips were installed in case of an emergency landing. Despite the cramped quarters, a pilot was provided with a cordite ejection seat, bail-out oxygen bottle and high-speed ribbon parachute. Four 0.5 in (12.7 mm) machine guns in the nose made up the aircraft's armament.
In service, the parasite fighter would be launched and retrieved by a trapeze
. With the trapeze fully extended, the engine would be airstarted and the release from the mother ship
was accomplished by the pilot pulling the nose back to disengage from the hook. In recovery, the aircraft would approach the mother ship from underneath and link up with the trapeze using the retractable hook in the aircraft's nose. The anticipated production shift would see a mixed B-36 fleet with both "fighter carriers" and bombers employed on missions. There were plans that, from the 24th B-36 onward, provisions would be made to accommodate one XF-85, with a maximum of four per bomber envisioned. Up to 10 percent of the B-36s on order were to be converted to fighter carriers with three or four F-85s instead of a bomb load.
On 9 October 1945, the USAAF signed a letter of intent covering the engineering development for two prototypes (US serial numbers
46-523/4), although the contract was not finalized until February 1947. After the successful conclusion of two reviews of a wooden mock-up in 1946 and 1947 by USAAF engineering staff, McDonnell constructed two prototypes in late 1947. The Model 27D was re-designated XP-85, but by June 1948, it was changed to XF-85 and given the name "Goblin". There were plans to acquire 30 production P-85s, but the USAAF took the cautious approach – if test results from the two prototypes were positive, production orders for more than 100 Goblins would be finalized later.
testing at Moffett Field, California, the first prototype XF-85 was accidentally dropped from a crane at a height of 40 ft (12.2 m), causing substantial damage to the forward fuselage, air intake and lower fuselage. The second prototype had to be substituted for the remainder of the wind tunnel tests and the initial flight tests.
As a production series B-36 was unavailable, all XF-85 flight tests were carried out using a converted EB-29B Superfortress mother ship that had a modified, "cutaway" bomb bay complete with trapeze, front airflow deflector and an array of camera equipment and instrumentation. Since the EB-29B, named Monstro, was smaller than the B-36, the XF-85 would be flight tested, half-exposed. In order to carry the XF-85, a special "loading pit" was dug into the tarmac at South Base, Muroc Field
, where all the flight tests originated. On 23 July 1948, the XF-85 flew the first of five captive flights, designed to test whether the EB-29B and its parasite fighter could fly "mated". The XF-85 was carried in a stowed position, but was sometimes tethered and extended into the airstream with the engine off, for the pilot to gain some feel for the aircraft in flight.
McDonnell test pilot Edwin Schoch was assigned to the project, riding in the XF-85 while it was stowed aboard the EB-29B, before attempting a "free" flight on 23 August 1948. After Schoch was released from the bomber at a height of 20,000 ft (6,096 m), he completed a 10-minute proving flight at speeds between 180 and 250 mph (200–300 km/h), testing controls and maneuverability. When he attempted a hook-up, it became obvious the Goblin was extremely sensitive to the bomber's turbulence
, as well as being affected by the air cushion created by the two aircraft operating in close proximity.Constant but gentle adjustments of throttle and trim were necessary to overcome the cushioning effect. After three attempts to hook onto the trapeze, Schoch miscalculated his approach and struck the trapeze so violently that the canopy was smashed and ripped free and his helmet and mask were torn off. He saved the prototype by making a belly landing
on the reinforced skid at the dry lake bed at Muroc
. All flight testing was suspended for seven weeks while the XF-85 was repaired and modified. Schoch used the down period to undertake a series of problem-free dummy dockings with a Lockheed P-80 Shooting Star fighter.
After boosting the trim power by 50 percent, adjusting the aerodynamics, and other modifications, two further mated test flights were carried out before Schoch was able to make a successful release and hookup on 14 October 1948. During the fifth free flight on 22 October 1948, Schoch again found it difficult to hook the Goblin to the bomber's trapeze, aborting four attempts before hitting the trapeze bar, breaking the hook on the XF-85's nose. Again, a forced landing was successfully carried out at Muroc.
With the first prototype's repairs completed, it also joined the flight test program, completing captive flights. While in flight, the Goblin was stable, easy to fly, and recoverable from spins, although initial estimates of a 648 mph (1,043 km/h) top speed proved optimistic. The first test flights revealed that turbulence during approach to the B-29 was significant, leading to the addition of upper and lower fins at the extreme rear fuselage, as well as two wingtip fins to compensate for the increased directional instability in docking. All the initial flights had the hook secured in a fixed position, but when the hook was stowed and later raised, the resulting buffeting added to the difficulty in attempting a hookup. To address the problem, small aerodynamic fairings were added to the hook well that reduced the buffeting when the hook was extended and retracted. When testing resumed, on the 18 March 1948 test flight, Schoch continued to have difficulty in hooking up, striking and damaging the trapeze's nose-stabilizing section, before resorting to another emergency belly landing. After repairs to the trapeze, Schoch flew the first prototype on 8 April 1949, completing a 30-minute free flight test, but after three attempts, abandoned his efforts and resorted to another belly landing at Muroc.
Aware of the problems revealed in flight tests, McDonnell reviewed the program and proposed a new development based on a more conventional design promising a .9 Mach capability, using alternatively a 35° swept wing and delta wing. McDonnell also considered adding a telescoping extension to the docking trapeze that would extend the device below the turbulent air under the mother ship.Before any further work on the trapeze, other modifications to the XF-85, or continued design studies on its follow-up could be carried out, the USAF
canceled the XF-85 program on 24 October 1949.
Two main reasons contributed to the cancellation. The XF-85's deficiencies revealed in flight testing included a lackluster performance in relation to contemporary jet fighters, and the high demands on pilot skill experienced during docking revealed a critical shortcoming that was never fully corrected. The development of practical aerial refueling for conventional fighters used as bomber escort was also a factor in the cancellation. The two Goblins flew seven times, with a total flight time of 2 hours and 19 minutes with only three of the free flights ending in a successful hookup. Schoch was the only pilot who ever flew the aircraft.
, Project FICON
and Project "Tom-Tom"
which involved fighter aircraft attached to bomber aircraft by their wingtips. Project FICON ("fighter conveyor") emerged as an effective Convair GRB-36D
/Republic RF-84K Thunderflash bomber and reconnaissance fighter combination, although the role was changed to that of strategic reconnaissance. Project FICON drew heavily on data from the abortive XF-85 project and closely followed McDonnell's recommendations in designing a more refined trapeze. A total of 10 converted B-36s and 25 reconnaissance fighters saw limited service with the Strategic Air Command
in 1955–1956, before being supplemented by more effective aircraft and satellite systems.
Fighter aircraft
A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...
conceived during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
by McDonnell Aircraft
McDonnell Aircraft
The McDonnell Aircraft Corporation was an American aerospace manufacturer based in St. Louis, Missouri. The company was founded on July 16, 1939 by James Smith McDonnell, and was best known for its military fighters, including the F-4 Phantom II, and manned spacecraft including the Mercury capsule...
. It was intended to be carried in and deployed from the bomb bay
Bomb bay
The bomb bay or weapons bay on some military aircraft is a compartment to carry bombs, usually in the aircraft's fuselage, with "bomb bay doors" which open at the bottom. The bomb bay doors are opened and the bombs are dropped when over the target or at a specified launching point.Large-sized...
of the giant Convair B-36
Convair B-36
The Convair B-36 "Peacemaker" was a strategic bomber built by Convair and operated solely by the United States Air Force from 1949 to 1959. The B-36 was the largest mass-produced piston engine aircraft ever made. It had the longest wingspan of any combat aircraft ever built , although there have...
bomber as a parasite fighter. The XF-85's intended role was to defend bombers from hostile interceptor
Interceptor aircraft
An interceptor aircraft is a type of fighter aircraft designed specifically to prevent missions of enemy aircraft, particularly bombers and reconnaissance aircraft. Interceptors generally rely on high speed and powerful armament in order to complete their mission as quickly as possible and set up...
s, a need demonstrated during World War II. Two prototypes were constructed before the program was terminated.
The XF-85 was a response to a United States Army Air Forces
United States Army Air Forces
The United States Army Air Forces was the military aviation arm of the United States of America during and immediately after World War II, and the direct predecessor of the United States Air Force....
(USAAF) requirement for a fighter to be carried within the Northrop XB-35
Northrop YB-35
The Northrop XB-35 and YB-35 were experimental heavy bomber aircraft developed for the United States Army Air Forces during and shortly after World War II by the Northrop Corporation. It used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are...
and B-36, then under development. It was a diminutive jet aircraft featuring a distinctive egg-shaped fuselage
Fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...
and a forked-tail stabilizer
Stabilizer (aircraft)
In aviation, a stabilizer provides stability when the aircraft is flying straight, and the airfoil of the horizontal stabilizer balances the forces acting on the aircraft....
design. The prototypes were built and underwent testing and evaluation in 1948. Flight tests showed promise in the design, but the aircraft's performance was inferior to the jet fighters it would have been facing in combat, and there were difficulties in docking. The XF-85 was swiftly canceled, and the prototypes were thereafter relegated to museum exhibits. The 1947 successor to the USAAF, the US Air Force (USAF), continued to examine the concept of parasite aircraft under Project MX-106 "Tip Tow"
FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
, Project FICON
FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
and Project "Tom-tom"
FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
following the cancellation.
Design and development
During World War II, American bombers such as the Boeing B-17 Flying Fortress, Consolidated B-24 Liberator and Boeing B-29 Superfortress were protected by long-range escort fighters such as the Republic P-47 Thunderbolt and North American P-51 Mustang. These fighters could not match the range of the Northrop B-35 or Convair B-36, the next generation of bombers developed by the United States Army Air Forces (USAAF). The development cost for longer-ranged fighters was high, while aerial refuelingAerial refueling
Aerial refueling, also called air refueling, in-flight refueling , air-to-air refueling or tanking, is the process of transferring fuel from one aircraft to another during flight....
was still considered risky and technologically difficult. Pilot fatigue had also been a problem during long fighter escort missions in Europe and the Pacific, giving further impetus to innovative approaches.
The USAAF considered a number of different options including the use of remotely piloted vehicles before choosing parasite fighters as the most viable B-36 defense. The concept of a parasite fighter had its origins in 1918, when the Royal Air Force
Royal Air Force
The Royal Air Force is the aerial warfare service branch of the British Armed Forces. Formed on 1 April 1918, it is the oldest independent air force in the world...
examined the viability of Sopwith Camel
Sopwith Camel
The Sopwith Camel was a British First World War single-seat biplane fighter introduced on the Western Front in 1917. Manufactured by Sopwith Aviation Company, it had a short-coupled fuselage, heavy, powerful rotary engine, and concentrated fire from twin synchronized machine guns. Though difficult...
parasite fighters operating from R23 airships. In the 1930s, the U.S. Navy had a short-lived operational parasite fighter, the Curtiss F9C Sparrowhawk, aboard airships Akron
USS Akron (ZRS-4)
USS Akron was a helium-filled rigid airship of the United States Navy that was lost in a weather-related accident off the New Jersey coast early on April 4, 1933, killing 73 of the 76 crew and passengers on board...
and Macon
USS Macon (ZRS-5)
USS Macon was a rigid airship built and operated by the United States Navy for scouting. She served as a "flying aircraft carrier", launching Curtiss F9C Sparrowhawk biplane fighters. In service for less than two years, in 1935 Macon was damaged in a storm and lost off California's Big Sur coast,...
. Starting in 1931, aircraft designer Vladimir Vakhmistrov conducted experiments in the Soviet Union
Soviet Union
The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....
as part of the Zveno project
Zveno project
Zveno was a parasite aircraft concept developed in the Soviet Union during the 1930s. It consisted of a Tupolev TB-1 or a Tupolev TB-3 heavy bomber acting as a mothership for between two and five fighters...
where up to five fighters of various types were carried by Polikarpov TB-2
Polikarpov TB-2
|-References:...
and Tupolev TB-3
Tupolev TB-3
The Tupolev TB-3 was a heavy bomber aircraft which was deployed by the Soviet Air Force in the 1930s and during World War II. It was the world's first cantilever wing four-engine heavy bomber. Despite obsolescence and being officially withdrawn from service in 1939, TB-3 performed bomber and...
bombers. In August 1941, these combinations flew the only combat missions ever undertaken by parasite fighters – TB-3s carrying Polikarpov I-16SPB
Polikarpov I-16
The Polikarpov I-16 was a Soviet fighter aircraft of revolutionary design; it was the world's first cantilever-winged monoplane fighter with retractable landing gear. The I-16 was introduced in the mid-1930s and formed the backbone of the Soviet Air Force at the beginning of World War II...
dive bomber
Dive bomber
A dive bomber is a bomber aircraft that dives directly at its targets in order to provide greater accuracy for the bomb it drops. Diving towards the target reduces the distance the bomb has to fall, which is the primary factor in determining the accuracy of the drop...
s attacked the Cernavodă bridge
King Carol I Bridge
The Anghel Saligny Bridge was built between 1890 and 1895 in Romania over the Danube and Borcea branch of the Danube, and when it was completed it then became the longest bridge in Europe and the third longest in the world...
and Constantsa docks, in Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...
. After that attack, the squadron, based in the Crimea, carried out a tactical attack on a bridge over the river Dnieper at Zaporozhe, which had been captured by advancing German troops. Later in World War II, the Luftwaffe
Luftwaffe
Luftwaffe is a generic German term for an air force. It is also the official name for two of the four historic German air forces, the Wehrmacht air arm founded in 1935 and disbanded in 1946; and the current Bundeswehr air arm founded in 1956....
experimented with the Messerschmitt Me 328
Messerschmitt Me 328
The Messerschmitt Me 328 was originally designed as a parasite aircraft to protect Luftwaffe bomber formations during World War II. During its protracted development, a wide variety of other roles were suggested for it...
as a parasite fighter, but problems with its pulsejet engines could not be overcome. Other late-war rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
-powered parasite fighter projects such as the Arado E.381 and Sombold So 344 were unrealized "paper projects".
On 3 December 1942, the USAAF sent out a Request for Proposals (RfP) for a diminutive piston-engined fighter. By January 1944, the Air Technical Service Command
Air Force Logistics Command
Air Force Logistics Command was a United States Air Force command. Its headquarters was located at Wright-Patterson Air Force Base, Ohio...
refined the RfP and in January 1945, the specifications were further revised in MX-472 to specify a jet-powered aircraft. Although a number of aerospace companies studied the feasibility of such aircraft, McDonnell was the only company to submit a proposal to the original 1942 request and later revised requirements. The company's Model 27 proposal was completely reworked to meet the new specifications.
The initial concept for the Model 27 was for the fighter to be carried half-exposed under the B-29, B-35 or B-36. The USAAF rejected this proposal, citing increased drag, and hence reduced range for the composite bomber-fighter configuration. On 19 March 1945, McDonnell's design team led by Herman D. Barkey, submitted a revised proposal, the extensively redesigned Model 27D. The smaller aircraft had an egg-shaped fuselage, three fork-shaped vertical stabilizers, horizontal stabilizers with a significant dihedral, and 37° swept-back folding wings to allow it to fit in the confines of a bomb bay. The diminutive aircraft measured 14 in 10 in (4.52 m) long; the folding wings spanned 21 ft (6.4 m). Only a limited fuel supply of 112 US gal (93.3 imp gal; 424 l) was deemed necessary for the specified 30-minute combat endurance. A hook was installed along the aircraft's center of gravity; in flight, it retracted to lie flat in the upper part of the nose. The aircraft had an empty weight just short of 4000 pounds (1.8 t). To save weight, the fighter had no landing gear. During the testing program, a fixed steel skid under the fuselage and spring-steel "runners" at the underside of the wingtips were installed in case of an emergency landing. Despite the cramped quarters, a pilot was provided with a cordite ejection seat, bail-out oxygen bottle and high-speed ribbon parachute. Four 0.5 in (12.7 mm) machine guns in the nose made up the aircraft's armament.
In service, the parasite fighter would be launched and retrieved by a trapeze
Trapeze
A trapeze is a short horizontal bar hung by ropes or metal straps from a support. It is an aerial apparatus commonly found in circus performances...
. With the trapeze fully extended, the engine would be airstarted and the release from the mother ship
Mother ship
A mother ship is a vessel or aircraft that carries a smaller vessel or aircraft that operates independently from it. Examples include bombers converted to carry experimental aircraft to altitudes where they can conduct their research , or ships that carry small submarines to an area of ocean to be...
was accomplished by the pilot pulling the nose back to disengage from the hook. In recovery, the aircraft would approach the mother ship from underneath and link up with the trapeze using the retractable hook in the aircraft's nose. The anticipated production shift would see a mixed B-36 fleet with both "fighter carriers" and bombers employed on missions. There were plans that, from the 24th B-36 onward, provisions would be made to accommodate one XF-85, with a maximum of four per bomber envisioned. Up to 10 percent of the B-36s on order were to be converted to fighter carriers with three or four F-85s instead of a bomb load.
On 9 October 1945, the USAAF signed a letter of intent covering the engineering development for two prototypes (US serial numbers
United States military aircraft serials
In the United States, all military aircraft display a serial number to identify individual aircraft. Because these numbers are located on the aircraft tail, they are sometimes referred to unofficially as "tail numbers"...
46-523/4), although the contract was not finalized until February 1947. After the successful conclusion of two reviews of a wooden mock-up in 1946 and 1947 by USAAF engineering staff, McDonnell constructed two prototypes in late 1947. The Model 27D was re-designated XP-85, but by June 1948, it was changed to XF-85 and given the name "Goblin". There were plans to acquire 30 production P-85s, but the USAAF took the cautious approach – if test results from the two prototypes were positive, production orders for more than 100 Goblins would be finalized later.
Operational history
During wind tunnelWind tunnel
A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...
testing at Moffett Field, California, the first prototype XF-85 was accidentally dropped from a crane at a height of 40 ft (12.2 m), causing substantial damage to the forward fuselage, air intake and lower fuselage. The second prototype had to be substituted for the remainder of the wind tunnel tests and the initial flight tests.
As a production series B-36 was unavailable, all XF-85 flight tests were carried out using a converted EB-29B Superfortress mother ship that had a modified, "cutaway" bomb bay complete with trapeze, front airflow deflector and an array of camera equipment and instrumentation. Since the EB-29B, named Monstro, was smaller than the B-36, the XF-85 would be flight tested, half-exposed. In order to carry the XF-85, a special "loading pit" was dug into the tarmac at South Base, Muroc Field
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
, where all the flight tests originated. On 23 July 1948, the XF-85 flew the first of five captive flights, designed to test whether the EB-29B and its parasite fighter could fly "mated". The XF-85 was carried in a stowed position, but was sometimes tethered and extended into the airstream with the engine off, for the pilot to gain some feel for the aircraft in flight.
McDonnell test pilot Edwin Schoch was assigned to the project, riding in the XF-85 while it was stowed aboard the EB-29B, before attempting a "free" flight on 23 August 1948. After Schoch was released from the bomber at a height of 20,000 ft (6,096 m), he completed a 10-minute proving flight at speeds between 180 and 250 mph (200–300 km/h), testing controls and maneuverability. When he attempted a hook-up, it became obvious the Goblin was extremely sensitive to the bomber's turbulence
Wake turbulence
Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wing vorticies and jetwash. Jetwash refers simply to the rapidly moving gases expelled from a jet engine; it is extremely turbulent,...
, as well as being affected by the air cushion created by the two aircraft operating in close proximity.Constant but gentle adjustments of throttle and trim were necessary to overcome the cushioning effect. After three attempts to hook onto the trapeze, Schoch miscalculated his approach and struck the trapeze so violently that the canopy was smashed and ripped free and his helmet and mask were torn off. He saved the prototype by making a belly landing
Belly landing
A belly landing or gear-up landing occurs when an aircraft lands without its landing gear fully extended and uses its underside, or belly, as its primary landing device...
on the reinforced skid at the dry lake bed at Muroc
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
. All flight testing was suspended for seven weeks while the XF-85 was repaired and modified. Schoch used the down period to undertake a series of problem-free dummy dockings with a Lockheed P-80 Shooting Star fighter.
After boosting the trim power by 50 percent, adjusting the aerodynamics, and other modifications, two further mated test flights were carried out before Schoch was able to make a successful release and hookup on 14 October 1948. During the fifth free flight on 22 October 1948, Schoch again found it difficult to hook the Goblin to the bomber's trapeze, aborting four attempts before hitting the trapeze bar, breaking the hook on the XF-85's nose. Again, a forced landing was successfully carried out at Muroc.
With the first prototype's repairs completed, it also joined the flight test program, completing captive flights. While in flight, the Goblin was stable, easy to fly, and recoverable from spins, although initial estimates of a 648 mph (1,043 km/h) top speed proved optimistic. The first test flights revealed that turbulence during approach to the B-29 was significant, leading to the addition of upper and lower fins at the extreme rear fuselage, as well as two wingtip fins to compensate for the increased directional instability in docking. All the initial flights had the hook secured in a fixed position, but when the hook was stowed and later raised, the resulting buffeting added to the difficulty in attempting a hookup. To address the problem, small aerodynamic fairings were added to the hook well that reduced the buffeting when the hook was extended and retracted. When testing resumed, on the 18 March 1948 test flight, Schoch continued to have difficulty in hooking up, striking and damaging the trapeze's nose-stabilizing section, before resorting to another emergency belly landing. After repairs to the trapeze, Schoch flew the first prototype on 8 April 1949, completing a 30-minute free flight test, but after three attempts, abandoned his efforts and resorted to another belly landing at Muroc.
Aware of the problems revealed in flight tests, McDonnell reviewed the program and proposed a new development based on a more conventional design promising a .9 Mach capability, using alternatively a 35° swept wing and delta wing. McDonnell also considered adding a telescoping extension to the docking trapeze that would extend the device below the turbulent air under the mother ship.Before any further work on the trapeze, other modifications to the XF-85, or continued design studies on its follow-up could be carried out, the USAF
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
canceled the XF-85 program on 24 October 1949.
Two main reasons contributed to the cancellation. The XF-85's deficiencies revealed in flight testing included a lackluster performance in relation to contemporary jet fighters, and the high demands on pilot skill experienced during docking revealed a critical shortcoming that was never fully corrected. The development of practical aerial refueling for conventional fighters used as bomber escort was also a factor in the cancellation. The two Goblins flew seven times, with a total flight time of 2 hours and 19 minutes with only three of the free flights ending in a successful hookup. Schoch was the only pilot who ever flew the aircraft.
Further developments
Despite the cancellation of the XF-85, the USAF continued to examine the concept of parasite aircraft as defensive fighters through a series of projects including Project MX-106 "Tip Tow"FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
, Project FICON
FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
and Project "Tom-Tom"
FICON project
The FICON program was conducted by the United States Air Force in the 1950s to test the feasibility of a Convair B-36 Peacemaker bomber carrying an Republic RF-84K Thunderflash parasite fighter in its bomb bay. Earlier wingtip coupling experiments including Tip Tow which were attempts at carrying...
which involved fighter aircraft attached to bomber aircraft by their wingtips. Project FICON ("fighter conveyor") emerged as an effective Convair GRB-36D
Convair B-36
The Convair B-36 "Peacemaker" was a strategic bomber built by Convair and operated solely by the United States Air Force from 1949 to 1959. The B-36 was the largest mass-produced piston engine aircraft ever made. It had the longest wingspan of any combat aircraft ever built , although there have...
/Republic RF-84K Thunderflash bomber and reconnaissance fighter combination, although the role was changed to that of strategic reconnaissance. Project FICON drew heavily on data from the abortive XF-85 project and closely followed McDonnell's recommendations in designing a more refined trapeze. A total of 10 converted B-36s and 25 reconnaissance fighters saw limited service with the Strategic Air Command
Strategic Air Command
The Strategic Air Command was both a Major Command of the United States Air Force and a "specified command" of the United States Department of Defense. SAC was the operational establishment in charge of America's land-based strategic bomber aircraft and land-based intercontinental ballistic...
in 1955–1956, before being supplemented by more effective aircraft and satellite systems.
Aircraft on display
After the program's termination, the two XF-85 prototypes were stored, before being surplused and relegated to museum display in 1950.- XF-85 Goblin, s/n 46-523, is on display at the National Museum of the United States Air ForceNational Museum of the United States Air ForceThe National Museum of the United States Air Force is the official museum of the United States Air Force located at Wright-Patterson Air Force Base northeast of Dayton, Ohio. The NMUSAF is the world's largest and oldest military aviation museum with more than 360 aircraft and missiles on display...
at Wright-Patterson Air Force BaseWright-Patterson Air Force BaseWright-Patterson Air Force Base is a United States Air Force base in Greene and Montgomery counties in the state of Ohio. It includes both Wright and Patterson Fields, which were originally Wilbur Wright Field and Fairfield Aviation General Supply Depot. Patterson Field is located approximately...
near Dayton, OhioDayton, OhioDayton is the 6th largest city in the U.S. state of Ohio and the county seat of Montgomery County, the fifth most populous county in the state. The population was 141,527 at the 2010 census. The Dayton Metropolitan Statistical Area had a population of 841,502 in the 2010 census...
. Following the cancellation of the program, the aircraft was transferred to the museum on 23 August 1950 and was one of the first experimental aircraft to be displayed at the new Air Force Museum. - XF-85 Goblin, s/n 46-524, was transferred to the Norton Air Force BaseNorton Air Force BaseNorton Air Force Base is a former front-line United States Air Force facility located east of downtown San Bernardino, California in San Bernardino County.-Overview:...
(near San Bernardino, CaliforniaSan Bernardino, CaliforniaSan Bernardino is a city located in the Riverside-San Bernardino metropolitan area , and serves as the county seat of San Bernardino County, California, United States...
) in 1950, still in a damaged state after its last emergency landing. When the base museum was closed and its collection dispersed, the second XF-85 prototype languished in an unrestored condition as part of the TallmantzFrank TallmanFrank Gifford Tallman was a stunt pilot who worked in Hollywood during the 1960s and 1970s.-Early life:...
private collection in California, until being acquired by Offutt AFBOffutt Air Force BaseOffutt Air Force Base is a U.S. Air Force installation near Omaha, and lies adjacent to Bellevue in Sarpy County, Nebraska. It is the headquarters of the U.S...
. It is now refurbished and displayed on its ground-handling trestle, nestled under the wing of a B-36J bomber (serial number 52-2217), at the Strategic Air and Space MuseumStrategic Air and Space MuseumThe Strategic Air and Space Museum is a museum focusing on United States Air Force military aircraft and nuclear missiles located near Ashland, Nebraska, along Interstate 80 southwest of Omaha, Nebraska. The objective of the museum is to preserve and display historic aircraft, missile, and space...
in Ashland, NebraskaAshland, NebraskaAshland is a city in Saunders County, Nebraska, United States. The population was 2,262 at the 2000 census.- History :Ashland is located at the site of a low-water limestone ledge along the bottom of Salt Creek, an otherwise mud-bottomed stream that was a formidable obstacle for wagon trains on the...
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Specifications