Piggyback Airplanes
Ten of aviation's most famous hitch-hikers.
- By Lynn Keillor
- Air & Space magazine, July 2012
Courtesy Brian Lockett/Goleta Air and Space Museum
Hitchhiker: Republic F-84 Thunderjet
Mothership: Boeing B-29 Superfortress United States, 1950
World War II “triple ace” fighter pilot Clarence E. “Bud” Anderson was no stranger to dangerous missions, and he wasn’t going to let the end of the war put a stop to his risk-taking. Anderson became a test pilot and took part in a highly unusual project to connect airplanes in flight.
Mothership-parasite attachments had taken many forms since the Bristol Scout was propped on crutches 35 years earlier, and now the U.S. military was testing a new, aerodynamic concept: a wingtip-to-wingtip configuration with the code name Tip Tow.
The idea came from German aircraft designer Richard Vogt, who came to the United States after World War II with a vision to gain something for nothing. He surmised that by attaching temporary fuel panels to the wingtips, an aircraft could achieve increased range for “free,” since the panels providing extra fuel would create their own lift, and the extended spar would reduce the induced drag and create a more efficient wing.
The U.S. Air Force was intrigued, but modified the idea to carry bomber-escort fighters for “free.” They designated the F-84 and the B-29 as the two airplanes for the job, with the ordinarily short-range fighter hitching a ride into faraway enemy territory alongside the bomber.
These craft were not the first to couple via wingtips: The Germans were experimenting in secret with the concept at the end of the war, but left little documentation. When the Americans considered the idea in 1947, they sent Anderson to test the concept with the Culver Q-14 target drone and a piloted Douglas C-47. Maneuvering the simple ring-and-hook coupling system “was like trying to thread a needle in the middle of a fire hose,” wrote Anderson in a 1979 article for the Society of Experimental Test Pilots. After some adjustments, the aircraft pair proved that wingtip coupling could be done, and beginning in 1950, tests proceeded with the F-84 and B-29.
Because the F-84 could take off and land on its own, the hookups were made in-air by a torpedo-shaped lance mounted to one of the fighter’s wings. Making the connection, says Anderson, required precision similar to inflight refueling using the probe-and-drogue system. The F-84 pilot had to insert the lance into an opening approximately one foot in diameter on the B-29’s coupler, which was on a retractable boom 19 inches off the end of its wingtip. Once inserted, the boom pulled the wingtips together into a rubber seal.
Throughout testing, the Tip Tow pilots completed 43 couplings and 15 hours of linked flight, with the longest dual-coupled flight lasting just over two hours. Tests showed that the induced drag reduction of the coupled airplanes, at higher gross weights and lower airspeeds, made them more efficient than a single B-29.
The connection wasn’t always graceful, and the pilot needed to control the F-84’s movement around the connection axis—the “rotation around the wing-tips like a hinge,” Anderson describes in an e-mail. “If it was not controlled properly, it could be dangerous for certain since [the connection] was locked and there was some structural bending going on in the bomber wing structure.”
The coupling mechanism was continually tweaked. At one point it included an automatic flight control system to find the proper damping frequencies that would hold the F-84 at the correct angle, but experiments proved deadly: One coupled F-84 and B-29 crashed when the system was activated and pitched the fighter onto the bomber’s wing. There were no survivors, and Tip Tow was cancelled.
| Tweet | Digg |
Comments (8)
In 1957 I was the co-pilot on a SA-16A (Grumman Albatross)
Air Rescue Service amphib for a trans-Atlantic crossing, with a stop half-way across in the Azores. We were ferrying the aircraft from Wheelus AFB, Tripoli,back to the Grumman factory where the A/C would be overhauled and upgraded to a B model. If my memory is correct, the leg from the Azores to Argentia, NewFoundland took about 14 hours. That airplane could carry a lot of gas! That was the longest flight I can recall, with the possible exception of a LHR-LAX or a JFK-TelAviv nonstop when I was a TWA 747 Captain.
Posted by William Polk on May 23,2012 | 04:21 PM
I've read in some sources about an alleged fifth operational D-21 flight? Is there any truth to this? If so, what happened to it?
Posted by Gray Stanback on May 23,2012 | 06:41 PM
In the late 1950's I was in SAC 92nd bomb wing. On our base we had a reconnaissance squadron flying B-36R's. The B-36 was towed over a pit in the pit was an F-84R. The F-84 was attached to the bomber and raised up partially into the special bomb-bay. The F-84 was launched and retrieved in flight on the trapeze. The F-84 could be refueled and the film canisters changed in flight. There was even a film processing lab in the rear of the B-36.
We later had U-2's and the need for the tandem B-36 and F-84 was no longer needed.
Posted by JIm Fling on May 24,2012 | 05:14 PM
A specialized aircraft was designed and built to be uniquely carried by the B-36 internally, supposedly for defensive purposes. My recollection was it was built by McDonnell and designated XF-85.
Posted by Kendall Russell Maj Gen USAF (ret) on May 25,2012 | 04:44 PM
In the summer of 1953 following my Midshipman Cruise to Rio, I worked as Assistant PR Director of the first Dayton Air Show. When the Show began, I squired around Howard Sochurek and Marshal Lumsden of Life Magazine. I was able to get the three of us on board a modified B-36 that had its own fighter escort (F-84) join up at 10,000 feet, hook it to its boom and pull the fighter into the bomb bay. Howard and I took many pictures of the event from both the bomb bay and the blisters in the aft fuselage. The Air Force insisted on processing the film and the pictures never appeared in Life as the Air Force claimed that they showed too much secret equipment.
Posted by John B. Neff on May 26,2012 | 11:50 PM
There was also the German Mistel piggyback project that saw limited operatons late in WWII.
In a sense, the X-1, X-2, X-15 and some other experimental aircraft followed the piggyback concept. Only the X-1 was capable of taking off from the ground (and it did it only once) so they needed to be carried to altitude by a bomber.
Posted by Larry J on May 31,2012 | 01:20 PM
I was born in Dundee, and remember my Dad telling me how he had seen Mercury and Maia on the Tay. He could only have been 11 at the time, but was still excited at the memory. I was delighted to find a compilation of Newsreels on You Tube showing the aircraft, including them taking off from Dundee for the flight to South Africa - wonder where Dad was watching them from, and if he's in the background somewhere.
Link to the newsreels:
http://youtu.be/bYtazEBQ1K8
Posted by Mike Brand on June 17,2012 | 07:49 PM
Well, I'm not sure if this could be a piggyback "airplane", but the shuttle Enterprise was piggybacked to a 747 and a least one time separated in flight to test the feasibility of the landing procedure of the space shuttle.
Posted by Fernando on January 23,2013 | 04:35 AM