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.
In the end, it became a moot point. While LABS training was suspended, new nuclear weapons were coming into the inventory that did not need to be tossed. And the new B-52s were better suited to low-level flying than the B-47s. These developments, combined with the accidents, led to LABS being dropped from the B-47 repertoire.
In mid-1957, while the B-47s were still fully involved with LABS, SAC turned all of its fighter-bombers and their nuclear mission over to the Tactical Air Command. TAC crews sat nuclear “Victor alert” around the world and continued training to use the over-the-shoulder maneuver, which the pilots dubbed “the idiot loop.” The nuclear-capable F-84s were replaced by more advanced fighters, mainly the North American F-100s, which became the mainstays of the Air Force tactical nuclear attack fleet. By this time, the term “LABS” began to be applied loosely to virtually all low-level nuclear loft deliveries, not just those that used the mechanical LABS instruments.
While the F-100 performed considerably better than the F-84, the LABS on the aircraft was somewhat quirky. F-100 pilot Les Turner recalls how difficult it was to adjust: “The LABS gyro was in a place were it was impossible to see, so the pilot had to use a small mirror to set in the proper numbers for his mission,” he says. “The best was a common dental mirror…and when a dentist or technician left the room with a pilot in the chair they had to take their mirrors with them or the mirrors would disappear. I still have my dental mirror and no, you cannot borrow it,” he adds with a grin.
The system’s location was not the only quirk. The F-100 introduced a link between the LABS and the fighter’s autopilot to give an automatic pull-up, called “auto LABS,” a feature that was not particularly popular. F-100 pilot Andy Stallings remembers, “I was having trouble performing the LABS maneuver well. Little things had a large effect on where the bomb would hit—you could pull too slow, or too fast, or, if you could, overshoot or undershoot 4 Gs and so on. Our weapons officer suggested I try ‘auto LABS’ to see what the maneuver looked like when it was properly performed. In ‘auto LABS,’ the autopilot had to be turned on at low level, and the F-100 autopilot was notoriously unreliable. The possibility of getting a nose-down command from a malfunctioning autopilot at 100 feet doing 500 knots made most pilots avoid engaging it, but I was young and indestructible. I tried it; it worked and worked well. But once I got the picture of what the delivery should look like, I didn’t use the autopilot.”
The 1950s also marked a period of competition between the U.S. Air Force and the Navy over the nuclear mission. The large Navy bombers—the Lockheed P2V Neptune, the North American AJ-1 Savage, and the Douglas A3D Skywarrior—were too big to do the LABS maneuver, but smaller Navy jet attack aircraft had the power to fly LABS maneuvers similar to the ones Air Force fighter-bombers used.
One early Navy nuclear delivery aircraft stood out in sharp contrast to the Air Force’s aircraft: the propeller-driven Douglas AD Skyraider. At about the same time the Air Force began to develop a way for its fighters to deliver atomic weapons, the Navy began to plan nuclear deliveries using the Skyraider, mainly because of its extremely long range. The ADs’ targets were as much as 2,000 miles away, and in the test program ADs flew as long as 13 and a half hours to see how the flights affected the pilots. As a result, the nuclear Skyraiders were modified with relief tubes and extra seat cushions, and the pilots carried a supply of aspirin for headaches caused by wearing their helmets for such a long time.