On 18 December 1969, SR-71A (61-7953) was scheduled for a functional check flight (FCF), piloted by SR-71/F-12 Test Force director Col. Joe Rogers and his Reconnaissance Systems Operator (RSO), Maj. Gary Heidelbaugh.
The aircraft configuration included, for the first time ever, the Optical Bar Camera (OBC) nose assembly and some modification were also made to SR-71 #953’s Electronic Counter-Measures (ECM) systems
The aircraft was tasked with a test flight to ensure the ECM’s proper function, in what is known as a functional check flight (FCF), and assigned the mission callsign of “Dutch 68”.
SR-71 was parked on the hardstand behind Hangar 1414 and readied for the mission. Left engine start was uneventful, but the right engine flamed out and had to be restarted.
Rogers taxied the SR-71 to the departure end of Runway 04. Before he began engine trim runs, the astro-inertial navigation system failed. The RSO attempted to correct the malfunction without success. On the advice of DUTCH BRAVO (SR-71 Operations), a hot ground-start was attempted and the system began operating normally.
The pilot ignited the afterburners and the SR-71 rolled down the 15,000-foot concrete strip and leapt into the sky above Edwards. DUTCH 68 passed over the 44-square-mile expanse of Rogers Dry Lake, climbing to an altitude of about 15,000 feet.
Rogers and Heidelbaugh completed a subsonic FCF in the Edwards area with Lt. Col. William Campbell flying chase in an F-104. Weather conditions included clear skies but haze obscured the horizon, so Rogers had to rely on his instruments in order to maintain level flight. Campbell had noticed DUTCH 68 was wandering a bit in his altitude profile but assumed Rogers was simply preoccupied with the FCF.
Rogers then requested clearance to climb to 25,000 feet for rendezvous with SAUCE 62 (a KC-135Q tanker) in the refuelling track near Beatty, Nevada. Once in sight of the tanker, Rogers maintained altitude control by visual contact with the KC-135 and refuelling was completed without incident.
After separating from the tanker Rogers initiated a pre-planned acceleration and climb, starting with a gentle turn to the left to correct his course. After receiving clearance from Los Angeles Center to climb to flight level 600 (60,000 feet) and above, the pilot notified the RSO that he was about to select afterburner and transition to supersonic flight.
A few seconds after lighting the afterburner, Rogers and Heidelbaugh heard a loud bang and high-frequency vibration, accompanied by a loss of power and severe control difficulties.
The pilot, suspecting possible engine compressor stalls, pulled back on the throttles until the vibrations ceased and then re-engaged afterburners. The vibrations started again and the airplane’s nose began to rise. As the aircraft pitched up, Rogers realized it was uncontrollable.
Full forward stick would not prevent #953 from pitching up and when control was lost, Joe said: “Let’s go!”, and the pair ejected.
SR-71 #953 fell apart in midair and crashed on the ground east of Death Valley near the village of Shoshone, California.
Most of the wreckage of the Blackbird hit the ground atop an underground stream and took down high voltage electrical lines, blacking out several of the nearby towns. A motorist driving past snapped several photographs, some of which are seen here, that were later obtained and used by the Accident Board.
As the crew ejected and parachuted to safety the aircraft continued in a deep stall, making its grave near Shoshone at the southern end of Death Valley, California.
Volunteer firefighters from Shoshone were the first to arrive at the scene. The aft section had sheared through several Continental-Edison transmission lines that supplied power to the communities of Shoshone, Tecopa and Zabriskie.
The airplane’s fuel ignited an intense fire, but it was soon extinguished. When Air Force crews arrived from Edwards they secured the site and began cleanup operations.
Fortunately, the Mission Recorder System (MRS) survived mostly intact and provided important information.
Investigation Report of Dutch 68 SR-71 Blackbird that crash
About seven weeks after the accident, the Board found a significant clue. When the nose of #953 was modified for the new Optical Bar Camera, the pitot-static lines were in the way. New lines had to be made to go around the new camera, lines made of stainless steel and about 3/8 of an inch in diameter. Inside one of the two static lines, a piece of “duct tape” rolled up into the shape of a cigarette was found.
The Board assumed it was placed there as a makeshift dust plug when the line was fabricated and forgotten.
The static line affected fed the primary flight instruments and was not the source for the TDI or MRS data. The normal ground testing of the pitot-static system before #953 flew was completed satisfactorily. But since some air could pass through the obstructed tube, this steady state test, which is basically a leak test, did not reveal any problems.
The NASA facility at Edwards, the Dryden Flight Research Center, performed a line lag test on the tube to determine how much the static pressure available to the flight instruments would lag behind the actual aircraft altitude during climbs and descents because of the obstruction caused by the duct tape. This analysis provided an exact correlation of the discontinuity between what Joe Rogers thought #953 was doing and what the MRS actually recorded.
When Rogers’ SR-71 finished refuelling and descended about 3,000 feet, he was reading an altitude about 2,000 feet higher. When he tried to level off at 25,000 feet, the altimeter and rate of climb continued to show a slight descent so he started to climb back. A little later, when Rogers thought he had returned to 25,000 feet, he was actually about 27,000 feet and 20-30 knots slower than indicated.
At this particular combination of weight, speed, & altitude, the aircraft needed full Afterburning Thrust to maintain a steady state flight. But the engines were starved for airflow at the same time and compressor stalled. At that point, a “pitch up” and loss of the aircraft was inevitable.
Campbell stated, “There were those that said: ‘If only he had looked at the TDI, he would never lose the airplane.’
That may be true, but the Board argued that having done so was not normal practice for Joe to follow while sub-sonic.
The Board had the evidence in hand that caused #953 to go down…a 2” wide piece of tape rolled into cigarette shape made by a well meaning contractor technician to keep dust or shavings from entering, and then forgotten.”
Image Credits: www.thesr71blackbird.com