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Aviation History
1992
1992 - 0058.PDF
1 AIR TRANSPORT \ US controllers admit TCAS fears BY KIERAN DALY IN WASHINGTON, DC The US Federal Aviation Ad ministration (FAA) has con ceded that air traffic controllers were inadequately prepared for the introduction of the TCAS II traffic-alert and collision-avoid ance system. An FAA-commissioned inde pendent study by ARINC (which sets aeronautical radio stan dards) on research of the TCAS II transition programme (TTP) highlights the controller confi dence issue, but supports TCAS generally on technical grounds. The report states: "The infor mation provided from control lers' questionnaires reflects a strong negative feeling toward the effectiveness and utility of today's TCAS." It adds, however, that "...there is a great deal of misinformation on TCAS within the controller workforce" and notes that "...many [technical] handouts were either never distributed or not read by the controllers". Periodic updates on the TTP were also not received by some controllers. In response, FAA acting ad ministrator Barry Harris says the FAA is making "extraordinary efforts" to help, and adds: "I just wish we had anticipated this problem a little earlier." A separate study by Lincoln Laboratory of highly publicised controller-reported radar cover age problems in the Chicago area confirmed the controllers' observations, but found causes other than TCAS implementa tion — which the controllers had suspected.' The study, released at the FAA International Conference on TCAS Implementation in Wash ington DC, is based on more than 2 million flight hours in about 2,000 aircraft over a 15- month period. The TCAS cockpit system is sues traffic advisories (TAs) to warn pilots when an intruder is predicted to be within 40-45s of becoming a collision hazard, and resolution advisories (RAs) indi cating appropriate avoiding ac tion when the intruder is predicted to be within 20-25s of becoming a hazard. Pilot questionnaires showed that pilots complied with RAs 61% of the time, citing prior visual contact, alerts during par allel runway operations and prior ATC coordination on an intruder's intentions as reasons for non-complying. Six pilot re ports of "descend" RAs being received less than 1000ft (300m) above the ground could not be confirmed (partly because of the lack of recorded data). After finding instances of faulty radar altimeter inputs to TCAS, however, ARINC is call ing for software changes to in clude a "reasonableness check" on radar altimeter inputs. It also found potential confu sion over the "descend, descend" and "reduce descent" aural warnings, with associated misin terpretations ofvertical-speed display — both of which need investigation. "Phantom" RAs were found to be caused by faults in the mu tual suppression bus designed to mask the host-aircraft transpon der, by host-aircraft altitude being corrupted by the air data computer, and by faults in ground-based transponders. ARINC found many cases of RA-provoked altitude deviations greater than the recommended 300ft, and occasionally more than 1,000ft; some were caused by excessive vertical speed and others by miscompliance with "weakening" RAs, but they were generally attributable to pilot performance. The pilots' major concerns were excessive TAs and RAs below 2,500ft with the attendant aural warning. Use of the TA- only mode or inhibition of the aural warning at a greater alti tude than the current 500ft are possible cures, although confer ence attendees stressed the need for more precise guidance on TA-only use, which is largely discretionary at present. D Delta B-737 engine jettisoned during Dallas take-off A"major engine malfunction" caused the starboard Pratt & Whitney (P&W) JT8D to fall off a Delta Air Lines Boeing 737-200 on take-off from Dallas/ Fort Worth airport on 7 January. The aircraft landed safely. The airliner involved was de livered to Delta in August 1984, and had logged 20,200h at the time of the incident, says Boe ing. Two earlier incidents of JT8D-powered 737s losing en gines, in 1987 and 1989, were caused by cracked engine mounting bolts. After the 1987 incident, the US Federal Aviation Administra tion directed airlines to inspect the aft mounting bolts regularly. Boeing and P&W say that the 737 nacelle is designed to sepa rate from the wing in the event of a major engine malfunction, in order to prevent structural damage to the aircraft. • Deutsche Airbus assembles first A321 Deutsche Airbus has started structural assembly of the Airbus A321 twin-turbofan short- to medium-range com mercial aircraft at its Hamburg site in Germany. First flight is scheduled for the second quarter of 1993. Final assembly of the aircraft, a stretched version of the A320, will also be carried out at Ham burg — the first Airbus to be assembled outside France. Work has already begun on assembling parts of the lower fuselage shell of the aircraft. These include the wing centre section, undercar riage doors and fuselage panels. Deutsche Airbus is also re sponsible for most of the fuse lage, the tail fin and for furnishing the passenger cabin interior. From the middle of this year, components manufactured by the other Airbus members will start arriving in Hamburg. Aerospatiale is providing the cockpit and front fuselage, Brit ish Aerospace is manufacturing the wings and the tail plane is being provided by Casa in Spain. Deutsche Airbus says: "We will begin final assembly in mid-year, with the roll-out and first flight of the aircraft in the second quar ter of next year." The A321 is 7m longer than the A320, offering be tween 186 and 200 seats compared with . A320's capacity of | 150-178 seats. Ten customers have placed orders for a total of 140 A321s. The choice of engine will be made between the GE/ Snecma CFM56-5B1 and the IAE V2530- A5 turbofans. • Hamburg sees the first stretched version of the A320 assembled 8 FLIGHT INTERNATIONAL 15 - 21 January, 1992
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