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Aviation History
1968
1968 - 1853.PDF
fUGHT International, 12 September (948 397 Altimeter Setting in Doubt at Ljubljana Jugoslav report criticises crew and airline PILOT ERROR is cited, though not in so many words, as thereason for the accident to Britannia Airways' BritanniaG-ANBB at Ljubljana on September 1, 1966. The Jugoslav report, translated into English, was issued by the BoT on September 8.* The accident occurred when the aircraft hit trees below the level of the threshold and broke up 11 miles from the runway during a night approach after a flight from Luton. Of the 117 people on board, 97 were killed. The Ljubljana air traffic controller had been in constant radio contact with the crew during the initial phase of the approach and had monitored the aircraft on radar from 20 miles out. Much supposition is contained in the report, especially as to what happened on the flight deck. Evidence available included the R/T tape, the controller's and meteorologists' statements, and the wreckage itself. No flight recorder was fitted to the aircraft. The significant sequence of events, which the report reconstructs from the evidence available, was that, in the first place, the crew made mistakes before they arrived in the Ljubljana area. The report says: "The pilots did not carry out the last portion of the flight, from the Jugoslav boundary up to the time of the accident, in strict accordance with the procedures and with the care expected, especially for a night approach, because it appears they had not anticipated a difficult landing—the runway being in sight ... at a distance of at least 12 n.m. from the airport. That crew pro- cedures in the cockpit were not meticulous enough and that the crew had not expected to have any difficulty in the approach and landing can be seen by the following: "(i) the crew was cleared to FL130 by the Zagreb ACC and the pilot carrying out the radio communications did not repeat it, •CAP 303: Report on the accident to Britannia G-ANBB at Ljubljana, Jugoslavia, on September 1, 1966. HMSO; price 6s. so that when he contacted Ljubljana Control he reported descending to FL120 and not to FL130. . . . "(ii) when the controller gave the radar position 'Dolsko abeam on the left side' the pilot did not disagree but acknowledged it by replying '105' yet 1 minute 20 seconds later he reported passing 'Dolsko.' "(iii) the crew set up the ILS frequency only on one equipment, while the other one was found tuned to the Zagreb VOR. The pilot was forbidden by his company regulations from making an ILS approach to Ljubljana, but this did not preclude monitoring the approach by reference to the ILS. "(iv) neither of the ADF sets were found on the frequency bands of the 'DOL' or 'MG' beacons when recovered from the wreckage. However, the tuning indicators were in the approximate positions for the frequencies of the two beacons and it is concluded that the band selectors had moved during the impact. "(v) the pilots probably did not monitor the altimeters as precisely as necessary for the final approach and landing, and the captain omitted to reset his altimeter to the QFE, as required by the operations manual, so an error was possible because neither of the altimeters had been set to the QFE-968mb. During the investigation at the place of the accident it was found that the navigator's altimeter was set to 1,011mb, i.e., to the QNH passed by the controller to the crew with the weather information. The other two altimeters, captain's and co-pilot's, were recovered, badly damaged, from the aircraft wreckage and sent to England for examination together with the navigator's altimeter. When examined their respective millibar settings were found to be as follows: captain's—left pilot seat .. 1,010.5mb .-•-•••-•••-.• co-pilot's—right pilot seat .. 1,005.5mb navigator's 1,010.5mb Tolerances for the first and second altimeter settings are ±2mb, so neither of the pilots' altimeters were set to 968mb, i.e., to the QFE that the controller passed to the crew with the meteorological information." . - Continued ovwlaaf ELEVATION OF FWST IMMCT WITHTKES (llMH-UtOHl OUra-MOn) NOTE'- FLIGHT MANUAL INFORMATION •AMD ON AIHFICL OF UJ1FHT * reconstruction of the probable approach to Ljubljana by G-ANBB showing the relevant altitudes and distances. The hill through which fie lower path appears to fit is in fact ikm to the left of the runway extended centre-line. The track of the aircraft (not shown here) indicates t/iot the crew were following the localiser signals from the ILS, although obviously not the glide-scope
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