On April 11, 1941, the Army Air Corps issued a specification calling for industry to produce a bomber capable of carrying 10,000 pounds of bombs to targets 5,000 miles away and return without refueling. The Army Air Corps initially sent invitations to submit preliminary designs to Consolidated Aircraft Corporation and Boeing Aircraft Company with Northrop and Douglas Aircraft following a short time later. The Air Corps chose Consolidated on Oct. 3, 1941 and a cost-plus-fixed-fee contract for two experimental models awarded on Nov. 15, 1941.
Events of World War II showed a need for fighter escort of bombers near the target area. The 10,000 -mile round trip flown at 330 mph, the mission required 30 hours to complete. The standard practice would have escort fighters along for protection and with aerial refueling still many years away, the range and duration were beyond the capability of fighter aircraft design and pilot performance and the concept of the B-36 internally carrying along a small parasite fighter began.
The concept of a parasite fighter that could be carried aloft for added protection against enemy aircraft has been around since the early 1930’s. Large dirigibles like the U.S. Navy’s Akron and Macon carried F9C-2 Sparrowhawk biplanes for protection and surveillance. The Air Services also tested wing-coupling techniques by carrying smaller aircraft attached to the outer wing of the host aircraft.
The parasite fighter project became project MX-472 and McDonnell Aircraft Company of St. Louis, Missouri, answered the request for proposal with four versions of its Model 27. No other aircraft companies had interest, and McDonnell was awarded the contract on Oct. 9, 1945. McDonnell’s Model 27E, a small single engine, low-wing monoplane with X-shaped vertical stabilizers and folding, swept-back wings, given the Air Force designation of XP-85, quickly earned the nickname Goblin.
The stubby parasite linked to the bomber via a skyhook located in the nose that caught a trapeze in the number one bomb bay in the B-36. The McDonnell-designed trapeze would raise and lower the aircraft. Since the vehicle operated exclusively from the host aircraft, there was no provision for conventional landing gear. With delays in the B-36 program, the flight testing of the new fighter would use a modified B-29 in place of the Peacemaker.
Wind tunnel testing of the first airframe, 46-523, now designated XF-85, began at NASA Ames Research Center’s 40 x 80-foot wind tunnel in January 1948 but the airframe was damaged during a lifting operation and sent back to St. Louis for repairs and the second XF-85, 46-524, sent in its place. Once completed, the Goblin spent the next few months at McDonnell prior the beginning of flight testing at Muroc Air Force Base, California in June.
A shortage of materials and engineers during WWII delayed development of the first truly intercontinental bomber. The XB-36 made its first flight nearly a year after the end of WWII on Aug. 8, 1946. As originally conceived, the parasite fighter support components for the B-36 would be delivered in kit form as to not interrupt aircraft production. With Consolidated building the bomber and McDonnell building the fighter, the question of responsibility for the trapeze assembly arose in a letter on Sept. 13, 1946, as well as the number of parasites carried on board. Air Materiel Command at Wright Field, Ohio responded:
“It is intended at this time to carry only one XP-85 in any one B-36. The B-36 is to carry a bomb load and a single fighter as protection. However, tactical requirements may dictate that the bomber carry the maximum number of fighters possible, which would be three. The B-36 has four bomb bays of which three are large enough to carry fighters.
“The fighter is to be stocked entirely within the parent airplane complete with all launching gear, the door closed so as not to change the external configuration of the B-36. Numerous bomb, fuel and fighter arrangements are possible depending upon opposition expected and the range required.
“The XP-85 is armed with four .50 caliber M-3 machine guns. Total of 1200 rounds of ammunition is carried. Ammunition and fuel can be reloaded into the fighter when taken aboard the B-36. No provisions are made for rockets, bombs or external tanks in the fighter.”
As engineering and assembly of both aircraft proceeded, the determination was that the required modifications could not be effectively completed in kit form and provisions would need to be built into the bombers on the assembly line. Air Materiel Command assigned specific components into Group “A” and Group “B” items with the trapeze assembly being separate.
Group “A” parts:
- Entrance door in bulkhead no.4- frame, door, valve, soundproofing, etc.
- Depressurization chamber attachment fittings and carry-through.
- Alteration to diagonal strap of bulkhead no.5.
- Rework of bomb rack fitting attachment carry-through on longeron to provide bolt pattern interchangeability.
- Structural carry-through for fighter nose bumper.
- Fuel system cross-over- fuselage fuel lines including 3 valves and valve control wiring up through fuselage bulkhead no. 4 and fuel system controls to forward cabin.
- Oxygen supply line tees for crew supply take-offs.
- Ejected case and link container modification.
- Radio operator’s table and panel modification.
- Electric wiring for AC and DC power with receptacles.
Group “B” parts:
- Bomb bay heating provisions consisting of insertion of diverter valve in tail anti-icing duct.
- Ammunition stowage provisions for fighter.
- Complete trapeze supporting structure.
- Hydraulic system items consisting of electric motor and pump with supporting structure, reservoir and supports, control panel for hydraulic system, and emergency retraction provisions.
- Depressurization chamber and installation details.
- Electric System and wiring for depressurization tank, hydraulic system, etc.
- Fighter oil provisions.
- Fighter installation control panels, etc.
- Walkways, service platforms, etc.
- Oxygen provisions for depressurization chamber and maintenance crew.
- Nose bumper for fighter.
- Flexible hoses for fuel and bomb bay heating air.
Only the last 78 airframes on the original order of 100 Peacemakers would receive the provisions for carrying the fighter, based on the fact that beginning with the 23rd airplane, the bomb bay section was being designed to carry very large bombs, making it easier to accommodate the parasite. The basic parts of Group “A” (items 1 through 5) required installation on the assembly line, while the rest of Group “A”, and all Group ”B” parts could be installed after the completion of XP-85 flight testing. Trapeze design and construction went to McDonnell in November 1946, while Group “A” and “B” parts went to Consolidated. Costs for Group “A” and “B” parts were estimated at $32,260.50 per airplane, plus $176,095.25 in engineering bringing the total cost for 78 airplanes to $2,692,414.25. The estimated cost for the trapeze assembly was noted at $151,145.00 each plus $72,919.00 for engineering. In order for the basic Group “A” parts be installed beginning with the 23rd production airframe, a directive would be required by April 1, 1947. Delays in B-36 production extended this decision date by one year.
On April 2, 1948, Maj. Gen. Edward Powers, assistant to the deputy chief of staff for Materiel, Air Force Headquarters, approved the basic Group “A” modifications of the 78 aircraft. The Air Force deferred purchase of Group “A” and Group ”B” components until Fiscal Year (FY) 1949. Meanwhile, with no B-36 aircraft available, flight testing of the XF-85 would be conducted using a B-29 in place of the Peacemaker.
The modified carrier aircraft, EB-29B, 44-84111, nicknamed Monstro, awaited the new aircraft at Muroc. Since the EB-29B lacked sufficient clearance between the fuselage and the ground to permit loading the XF-85, a special loading pit was constructed at Muroc, 24 ½ feet wide, 92 feet long, and 17 ½ feet deep at one end with an inclined ramp permitting the XF-85 to be lowered on its ground handling dolly. McDonnell assigned test pilot, Edwin Schoch, as the Goblin pilot for all flight testing at Muroc.
Prior to any free flights, the second XF-85, 46-524, performed a series of 5 captive flights beginning on July 22, 1948, where the Goblin was lowered into the airstream, engine started and ‘flown’ while on the trapeze. The first free flight took place on 23 Aug 1948 and lasted a total of 25 minutes with Schoch making two hook-up attempts, the second of which resulted in a broken canopy and Schoch’s helmet being knocked off. With minimal damage, Schoch recovered and made a successful skid landing on the dry lakebed at Muroc.
The first successful hook-up came during flight two on Oct. 14, during Schoch’s second attempt during that flight. Flights 3 and 4, flown the following day resulted in successful hook-ups. The brief flights lasting only 6 minutes and 4 minutes, respectively, would be the last successful hook-ups of the program. By this time, officials questioned the requirement for carrying the fighter escort as advancements on in-flight refueling technology allowed fighter escorts to cover longer distances. The flight characteristics and short range of the Goblin also made it impractical as a bomber escort.
The Goblin returned to St. Louis for modifications after the fifth free flight. With modifications completed to both XF-85’s, they returned to Muroc for further testing, though each flew just one more time each before cancellation of the program on Oct. 24, 1949. Total flight time for the two vehicles totaled 2 hours and 19 minutes.
After a long and controversial development, the Strategic Air Command (SAC) accepted first B-36A on June 26, 1948, while improved B model followed a short time later. Over time, the B-36 won over its critics and became the backbone of strategic deterrence as originally envisioned. By the time SAC took delivery of the final airplane on Aug. 14, 1954, a total of 381 Peacemakers had rolled off the assembly line. This number does not include the two prototypes, one static test airframe, the sole XC-99 or the two YB-60 jet prototypes.
The parasite concept did not die with the XF-85 program. Under the fighter conveyor (FICON) program, 10 RB-36D’s and 25 Republic RF-84F aircraft were modified for use as extended range reconnaissance aircraft. After modifications, their designations became GRB-36D-III and RF-84K’s respectively. Little is known about actual FICON missions, but rumors persist about overflights of north-eastern Russia before the Lockheed U-2 became available. While not an actual parasite, Convair did use a B-36 to ferry the B-58 static test article to Wright-Patterson AFB for loads testing.
With its heavy lift capacity, it is not surprising the Air Force and other airframe manufacturers chose the Peacemaker as a mothership for their various parasite proposals. Other fighter aircraft proposed for use with the B-36 included the Douglas F4D Skyray, unmanned F-86 missile, Convair F-102 Delta Dagger and Republic F-105 Thunderchief. All of the competing companies for the hypersonic X-15 test vehicle initially chose the B-36 as their mothership. Convair proposed using the Peacemaker to carry their GEBO II (Generalized Bomber) concept as well as early variations of MX-1626, which evolved into the B-58 Hustler and their triplesonic, manned, reconnaissance aircraft concept, named Fish.
North American Aviation proposed air-launch variants of their Navaho missile launching from the B-36 as did their competitor Northrop Aircraft with their MX-775B Boojum missile as well as an air-launch variant of Snark. Though none of these parasite concepts for the B-36 became a reality, the role of carrier aircraft for many future experimental test programs went to Boeings B-52 Stratofortress prior to the last flight of a Peacemaker on April 30, 1959.
Full document:
https://media.defense.gov/2023/Jul/31/2003271433/-1/-1/1/LOOKBACK_PEACEMAKER%20PARASITES.PDF/LOOKBACK_PEACEMAKER%20PARASITES.PDF