Target: Soviet weapons plant. Mission: Low-altitude bombing. Payload: Nuclear. Problem: Getting back.
- By Marshall Michel
- Air & Space magazine, May 2003
(Page 3 of 5)
The B-47s proceeded to subject the LABS system to weapons delivery testing, flying the toss maneuver first at minimum weight, then increasing the weight until the last run was at the airplane’s maximum gross weight, 130,000 pounds. In June 1955, a B-47 tossed a 6,000-pound dummy nuclear weapon from a 2.6-G pull-up into a half Cuban Eight, and later tossed an 8,850-pound dummy bomb using the same maneuver. The maneuvers proved easy to perform, and the LABS functioned well. By December 1955, SAC was sufficiently satisfied with the tests to assign three B-47 wings to initiate a low-level-flying and LABS training program called Hairclipper.
The maneuver was “either a bomber pilot’s dream or nightmare,” recalls Sigmund “Alex” Alexander, former president of the B-47 Association, and the crews initially viewed the new tactic with some apprehension. Stewart Frasier, a B-47 bombardier/navigator stationed at Schilling Air Force Base in Kansas, remembers first hearing about it when he and his squadron returned from temporary duty in England. “They announced we had a new bombing plan,” he recalls. “Then they showed us a short film of the B-47 LABS maneuver. We were surprised, to say the least, and there was a lot of concern among the crews. The wing commander heard about this concern, and a couple of days later he ordered all the air crews to assemble near the runway at high noon. He flew down the runway low and fast and then pulled up, over and down into a [half] Cuban Eight to demonstrate it could be done and the wings wouldn’t break.”
B-47 pilot Fred Lange flew a number of LABS training missions from MacDill Air Force Base in Florida. He recalls that the first LABS maneuver he flew with an instructor scared him “because the airspeed going over the top was very slow just before starting the half-roll. In the maneuver, the main thing I tried to do was to lock my knees and not work the rudder pedals to keep the aircraft lined up on a straight line and make a perfect maneuver. I was afraid that the rudder might fail—it was the weakest control surface on the B-47. [But] it just didn’t matter whether we flew a perfect maneuver. I got used to it, and the real fun part of the missions was doing aileron rolls on the way to the bombing range.”
In an actual operation, the B-47 approached the target at very low level while the navigator/bombardier located the target on his radar, computed the pull-up range, and put the solution into the pilot’s LABS timer. At the point where the maneuver was computed to begin, a light on the pilot’s LABS instrument came on and the pilot followed the needles into a 2.5-G pull-up. When the bomb released automatically, the pilot reduced back pressure on the control yoke to keep the B-47 right on the edge of a stall buffet as the bomber went over the top upside down at 85 knots, pulling a third of a G or less and flying on thrust alone. Once the aircraft had come out of the top of the maneuver and was diving, the pilot rolled upright as the copilot called off airspeed to make sure the aircraft did not exceed 400 knots in the dive—any faster and the B-47 suffered aileron reversal, a condition in which a deflection of the aileron tended to flex the wing in the opposite direction and roll the airplane the wrong way.
Overstressing the aircraft as it pulled out from the dive was a major concern—the B-47 had a structural limit of 3 Gs, and exceeding it risked catastrophic structural failure. B-47 pilot Robert Winn recalls, “There was nothing like flying along beside another B-47 and watching it start its LABS pull-up. The fuselage actually started to bend in a U-shape as the aircraft reluctantly entered the maneuver.”
In practice, the missions presented new challenges. The navigator sat in the nose of the aircraft with virtually no outside view. Stewart Fraser notes: “Navigation for toss bombing in the B-47 was very difficult, especially at night. The aircraft bounced a lot at low level, and sometimes it was too rough for celestial navigation, too low to use the radar, and we were flying too fast for visual navigation. Often we just flew course, time, and distance.
“One night we got completely lost over Texas and did our pull-up over Dallas instead of the nearby range,” he recalls. “Fortunately, we didn’t hit anybody over Love Field, but at that point I decided my mother loved me more than the Air Force did, so I got out.”
In the first year, accidents began to plague the Hairclipper program. One B-47 crashed on a bombing range in Florida, another failed to roll out of a LABS maneuver in time, and a third, with three instructors on board, crashed at night off the coast of California during a practice mission. Then, in early 1958, things began to come apart, literally, for the B-47 fleet. Six aircraft flying low-level missions were lost when wings came off. All B-47 low-level training, especially LABS, was suspended. Examinations revealed fatigue cracks in the “milk bottle” bolts (so named because of their shape) that joined the wing to the fuselage. The cracks were found on virtually all the B-47s that flew low level, and the culprit was suspected to be LABS. It was finally determined that LABS units had no more problems than any other, and the B-47 that Boeing regularly used for LABS tests had no fatigue cracks at all. At the time, however, structural analysis was very unsophisticated, and to this day unfounded rumors persist that the LABS maneuver was responsible for many of the crashes.