The ultra-quiet ‘whisper jet’

Press, 16 May 1989, Page 20

The ultra-quiet ‘whisper jet’

Les Bloxham, travel editor, reports

Residents on the isle of Man made a run on alarm clocks last year, and unwittingly endorsed the quietness of a revolutionary new British-made airliner. Alarms were not needed in the past, Manxmen say, because they could rely on being woken by the first flight leaving each morning. The "early-call” service had been provided by courtesy of Manx Airlines, but it apparently ended when the airline replaced its aircraft with the ultra-quiet 8Ae146 "whisper jets” last year. Their comparative lack of noise caught the islanders napping: the demand for alarm clocks soared. I am unable to verify the authenticity of the tale, but after it was first reported in the Isle’s newspaper, British Aerospace were quick to include it in their promotional brochures. I can, however, verify from three brief personal experiences with the 146 that it is, indeed, a very quiet airliner. The first was in 1984 when I sat in the tussocks at Mount Cook and watched it land and take-off during a testflight. Along with other witnesses, I saw it, but did not hear it — even the skylarks weren’t disturbed. The second occasion was at Wellington last October when a military version of the 146 called on a demonstration run. The sound of its four jets was barely inseparable from the airport’s normal background noise. I later learned, that meters set up by the Health Department to monitor the event had all failed to

register a reading. My most recent experience was at Los Angeles where I spent a night in a hotel room so close to the international airport that I thought I was sleeping in the control tower. Of all the jets that took off every minute or so, only one didn’t rattle the windows — a 8Ae146 flown by USAir. Acclaimed now internationally as the world’s quietest airliner, the “quiet trader” or “whisper jet,” as it has been tagged, has won unrestricted day and night access to many tightly controlled noise-sensitive airports in Europe, Australia, and the United States. Why is this four-engine airliner so much quieter than other modern aircraft powered by fewer engines? The answer is a combination of the aircraft’s unique engine design and exceptional landing and take-off performance.

The high level of noise produced by conventional jets is caused mainly by super-heated, high-speed core gases thrusting into the surrounding air. With the 8Ae146, however, a large by-pass fan at the front of the TextronLycoming engine wraps the hot high-speed gases from the tailpipe in a blanket of cooler, slower air which not only acts as a muffler, but also increases fuel efficiency. Geared fans and the absence of fixed vanes puts whine from the turbines above audible range.

Any noise remaining is mostly absorbed by special linings in the intake and by-pass ducts. The aircraft’s design and thrust allows it to climb away from an airport much more steeply than other jets, and to approach a runway at twice the normal angle. It has a particularly slow touch-down speed of 9.0 knots, thereby eliminating the need for reverse thrust which, on conventional jets, produces a loud burst of noise. Tests carried out by American aviation authorities at John Wayne Aiport in California, which enforces the most stringent noise-level conditions in the United States, show that the BAe 146-200 met an 89.5 dBA restriction with ease, even at its maximum take-off weight of 40,597 kg. By reducing this to 36,288 kg, the aircraft was able to keep within an even tougher limit of 86 dBA to qualify for unrestricted access.

However, to meet even the 89.5 dBA noise limit, a Boeing 737-300 had to operate at a severely reduced take-off weight of 45,360 kg —15,876 kg below its maximum. It failed to pass the 86 dBA test.

Now airlines using BAel46s can fly a full load of 100 passengers from John Wayne Airport over distancces of up to 1310 nautical miles. A 8737-300, in meeting the 89.5 dBA limit by trimming a third off its payload, could also carry 100 passengers

— but" only on a flight of 330 nautical miles.

The whisper jet’s unrestricted acceptance by airports firmly closed at night to other big aircraft, greatly impressed Sir Peter Abeles, the joint managing director of Ansett Transport Industries. His $3OOO million order three years ago for 80 of the jets set British Aerospace on the road to success. Twenty are already flying night-freight routes in Europe and Australia for his cargo express company, TNT. Others are carrying passengers for Ansett W.A. Late next month, Ansett New Zealand will take delivery of the first of eight for its main-trunk routes between Auckland and Dunedin, and the tourist routes that link Rotorua with Queenstown. Queenstown has been pressing for jet services for several years — but not at any cost. When Mount Cook Airline made a move in 1985 to serve the resort with 8737 s leased from Air New Zealand, many residents who were worried about possible noise pollution vigorously opposed the flights. Mount Cook eventually shelved the 8737 plan and has continued to serve the route with its aging, but reliable, fleet of Hawker Siddeley 7485. With barely two months to go before its main competitor introduces modern, bigger and much faster aircraft

to the routes it pioneered and developed, the Mount Cook company is left with little time to ensure it retains a competitive foothold with comparative jet equipment. Ironcially, the company let slip an opportunity to buy two BAel46s five years ago when an attractive deal negotiated by its former chief executive, Mr Philip Phillips, was rejected by the board. It was a decision that indirectly paved the way for Ansett’s entry to New Zealand. Had Mount Cook been flying the 8Ae146 jets in 1986, Newmans Air certainly would not have mounted a challenge on the tourist routes with its two turboprop de Havilland Dash-7s — a move which, in turn, led to Ansett’s takeover and ultimate expansion.

The imminent introduction of Ansett’s whisper jets is known also to have Air New Zealand worried because of the Wellington City Council’s proposal to progressively shut out noisy 8737 s from its airport over the next four years. Replacing the domestic jet fleet would cost the airline well over $5OO million, and an order would have to be placed soon to beat the deadline.

Ansett will also be able to boast after taking delivery of its eighth whisper jet next February that it has the most modern fleet of domestic aircraft in the Southern Hemisphere. There is no doubt that New Zealand’s domestic aviation scene is facing a quiet revolution in the year ahead.