18 December 1969: Colonel Joseph William Rogers and Major Gary Heidelbaugh were flying Lockheed SR-71A 61-7953 to test a new system installation followed by a training mission. The functional test had gone well and the Blackbird rendezvoused with a KC-135 tanker before proceeding with the mission.
After coming off the tanker, Colonel Rogers (call sign “Dutch 68”) radioed the regional air traffic control center for permission to climb through all flight levels to 60,000 feet (18,288 meters), or Flight Level Six Zero Zero.
A short transcript of the radio and intercom transmissions follows:
(Pilot, Colonel Joseph W. Rogers; RSO, Major Gary Heidelbaugh; L.A. Center: Los Angeles Center, the Federal Aviation Administration Air Traffic Control Center at Palmdale, California. Times listed are UTC.)
Pilot: “Los Angeles Center, Dutch 68.” [2106:45]
L.A. Center: “Dutch 68, rog, loud and clear. How me?”
Pilot: “Roger, you’re loud and clear. I’m in a left turn flight level two six zero, requesting climb above six zero zero Route Aqua.”
L.A. Center: “Rog, your routing is approved. Climb and maintain above 600 and squawk 4400.”
Pilot: “Four four squawking.” [2107:13]
L.A. Center: “Dutch 68, Rog. Have you radar contact. Report 310 climbing.” [2107:27]
Pilot: “Okay, I’m going to light them off, Gary.” [est 2107:30]
RSO: “That’s our heading.”
RSO: “What caused all that?” [est 2108:00]
Pilot: “I don’t know.”
RSO: “. . . Climbing.”
Pilot: “Let’s go.” [est 2108:15] CREW EJECTS
L.A. Center: “Dutch 68. Say your altitude.” [2110:30]
L.A. Center: “Dutch 68. Say your altitude.” [2110:50]
L.A. Center: “Dutch 68, Dutch 68, Los Angeles.” [2111:12]
L.A. Center: “Dutch 68, Dutch 68, Los Angeles.” [2111:28]
When Colonel Rogers advanced the SR-71’s throttles to go into afterburner for the climb, the compressor sections of both engines stalled. (Compressor stall is a condition that occurs when airflow through the engine intake is disrupted. Normal flow ceases, the engine stops producing thrust, and there can be violent oscillations and uncontained failure of the compressor section.) The SR-71A slowed abruptly and then violently pitched upward. Rogers said, “Let’s go,” and both men ejected from the out-of-control airplane.
Rogers and Heidelbaugh safely parachuted to the ground. 61-7953 crashed near Shoshone, California, and was totally destroyed by the crash and fire that followed.
The accident investigation determined that a small roll of 2″-wide (5.08 centimeters) duct tape was lodged inside one of the tubes of the airplane’s pitot-static system. When the new system had been installed, it required that the pitot-static tubing be modified and rerouted. A technician apparently placed the rolled duct tape inside an open section of tubing to prevent entry of dirt or foreign objects. When the tubing was reassembled, this makeshift plug was not removed. Post crash testing showed that the plug did not totally close off airflow, but that it decreased it, causing the altimeter to read too high and the airspeed indicator too fast. The normal test of the pitot-static system following the modification did not reveal the problem.
When Joe Rogers advanced the throttles, he was at approximately 27,000 feet (8,230 meters) rather than the indicated 25,000 feet (7,620 meters). He was also about 30 miles per hour (48 kilometers per hour) slower than indicated. The sudden demand for increased airflow as the throttles advanced could not be met by the thinner, slower air, and the compressors stalled.
Joe Rogers was a fighter pilot in World War II, the Korean War and the Vietnam War. He was a highly experienced test pilot with considerable experience in Mach 2+, high-altitude aircraft. He had been the commanding officer of the F-12/SR-71 Test Force at Edwards Air Force Base. Ten years and three days before this accident, he had set a World Speed Record while flying a Convair F-106A Delta Dart. (See post for 15 December 1959)
© 2016, Bryan R. Swopesby