1996 United States Air Force Boeing T-43 crash

Investigation

The official US Air Force accident investigation board report noted several reasons that led the Boeing CT-43A, callsign "IFO-21" (short for Implementation Force), to crash. Chief among the findings was a "failure of command, aircrew error and an improperly designed instrument approach procedure".

The Boeing CT-43A used for this flight was formerly a T-43A navigator training aircraft that was converted for distinguished visitor travel. The flight was on an instrument flight rules non-directional beacon (NDB) approach, which is a non-precision type of instrument approach, to Runway 12 when it strayed off course. Non-precision approaches are those that do not incorporate vertical guidance. While NDB approaches are essentially obsolete in the United States, they are still used widely in other parts of the world. Because of their infrequent use in the United States, many American pilots are not fully proficient in performing them (a NASA survey showed that 60% of American transport-rated pilots had not flown an NDB approach in the last year). The investigation board determined that the approach used was not approved for Department of Defense aircraft, and should not have been used by the aircraft crew. The board determined that the particular NDB approach used required two operating ADFs, the instrument used to fly such an approach, on board the aircraft, but this aircraft only had one ADF installed. To successfully fly the approach, one ADF was required to track the outbound course of 119° from the Koločep NDB (KLP), while another ADF was required to observe when the aircraft had flown beyond the Cavtat NDB (CV), which marked the missed approach point. Further, the board noted that the approach was rushed. The aircraft passed the final approach fix at 80 kn above the proper approach speed and had not received the proper clearance from the control tower to initiate the approach.

The crash site, on a 2,300 ft hill, was 1.6 mi northeast of where the aircraft should have been on the inbound course to the NDB. The published NDB approach brings the inbound aircraft down a valley, and has a minimum descent height of 2,150 ft at the missed approach point (where they should have climbed and turned to the right if the runway was not in view), which is below the elevation of the hills to the north. The runway is at 510 ft above sea level. Five other aircraft had landed prior to the CT-43A and had not experienced any problems with the navigational aids. No emergency call from the pilots occurred, and they did not initiate a missed approach, though they were beyond the missed approach point when they hit the hill at 2:57 pm local time.

Each country is responsible for publishing the approach charts, including minimum descent heights, for its airports, and the investigators noted that the minimum in mountainous terrain in the United States is 2,800 ft, as compared to the 2,150 ft on the chart given to the crew of IFO-21. It was a requirement of the US Air Force to review and approve all charts, and to ban flights into airports for which the charts did not meet American aviation standards. The commander of the 86th Operations Group, Col. John E. Mazurowski, revealed that he had requested (but not yet received) approval to waive the review for Dubrovnik, as the approach had worked for years, and the delay of a full review could hamper the interests of the American diplomatic mission.