Back on May 2, 1980, one of the MD-80 demonstrators was conducting a test sortie to evaluate landing distance. During one of the approaches, the pilot flew a steeper than normal approach, flared late, and touched down hard. But what happens next is incredible.
The MD-80 that was being tested had a HUD in the pilot’s position. But the copilot just had traditional instrumentation. During the last seconds of the final approach, the pilot saw that he was near the maximum descent rate of 720 feet per minute. The pilot reported that he felt a slight increase in the descent rate but kept the power in later and applied back pressure on the yoke a bit early to arrest the descent rate.
The aircraft touched down hard as the nose slammed down and the tires blew. After touchdown, the pilot continued the planned landing procedure. He applied full brakes, deployed the thrust reverser and stopped on the runway.
The aircraft not only exceeded the structural limitations (ie- a hard landing), but landed so hard that the aircraft sustained structural failure. The aircraft touched down 2,298 feet down the runway. Upon the hard landing, the tail buckled and then sheared off. The plane continued down the runway, minus its tail. It stopped at 5,634 feet down the runway.
Here’s the crazy part…they didn’t know they lost the tail until they shutdown the aircraft after stopping on the runway.
The crew knew it was a hard landing but didn’t expect it to be that bad. Can you imagine the shock of exiting the aircraft and not seeing a tail?
Seven people were on-board the aircraft. Only one flight-test engineer was injured. He broke his left leg. Everyone else survived without injury.
The NTSB determined that the official cause of the accident was the pilot’s failure to fly a stabilized approach within manufacturer’s tolerances. Contributing to the accident was the fact that the manufacturer’s procedures didn’t require crews to call out critical flight parameters. You can read the full report here.
Repaired and returned to service
The aircraft suffered substantial damage. Not only did the tail separate but the gear was heavily damaged and there was some buckling of the fuselage skin.
McDonnell Douglas decided to repair the aircraft. It returned to service as a test article, later flying the McDonnell Douglas’s test UHD Unducted Fan. The aircraft remained with McDonnell Douglas until it was broken up in 1994
The main reason the tail snapped off was due to a change to the angle that attached the DC-9 vertical stabilizer leading edge to the upper fuselage. It originally was one piece. A cost savings around 1977 broke it into 3; the formed part that wrapped around the leading edge, and the 2 side pieces further aft. What they didn’t realize was further forward of the break, 2 upper longerons ended, transferring the load to the attach angles. That left a weak spot. DC-9’s weren’t affected as much, but the heavier MD-80 loads caused a crack to form across the upper crown sooner. It showed up on some Hawaiian MD-80s which got more landing cycles. They had to return to the original design. That error could have resulted in losing the tail in flight if an inspection hadn’t caught it.
At this time FAA permitted credit for sink rate up to a maximum. Manufacturers wanted full credit to minimize certified landing distance required (and sell more jets, and make more money). In this landing the sink rate was targeted, but the crew failed in their execution. The ability to use touchdown sink rate was later eliminated resulting in a safer FTT.