The British Aerospace BAE – 146

I

Aircraft manufacturers had, for some four decades, attempted to design the elusive DC-3 replacement with different powerplant types, including the piston-engined Convair 240/340/440 and Martin 2-0-2/4-0-4 series and the turboprop Vickers Viscount, Fokker F.27 Friendship, and Hawker Siddeley HS.748. The latest attempt had been made by the British aircraft industry when both de Havilland and Hawker Siddeley had conducted market research and formulated designs for a small-capacity, short-range airliner powered by pure-jet engines during 1959 and 1960.

Of the two, de Havilland, with its previous Rapide, Dove, and Heron pistonliners, had had considerable regional aircraft experience and had designed the world's first pure-jet airliner in the form of the quad-engined DH.106 Comet. An initial study for such a DC-3 replacement, designated the DH.123, had featured a 60.6-foot overall length, an 81.3-foot wingspan, two 1,150 shp Gnone turboprops attached to a high wing, and a 22,100-pound maximum take off weight. So configured, it would have accommodated between 32 and 40 passengers, or slightly more than the DC-3's standard 21 to 28.

De Havilland, subsequently taken over by Hawker Siddeley and redesignated the "de Havilland Division," had forcibly discontinued design work on the DH.123 because it would have competed too closely with Hawker Siddeley's own Rolls Royce Dart-powered Avro 748 which had seated 44. Nevertheless, existing turboprop competition, coupled with de Havilland's belief that pure-jet technology would attract considerable passenger appeal, resulted in the mid-1960 DH.126 design proposal, which featured the later-standard configuration of most low-capacity, short-range twin-jets, such as the SE.210 Caravelle, the BAC-111, and the DC-9, with a swept wing, aft-mounted engines, and a t-tail. Powered by two 3,860 thrust-pound de Havilland PS92 jet engines, it had featured a 60.3-foot length for accommodation of 30 passengers and a 62-foot wingspan.

Several iterations had introduced progressive, although moderate wingspan, thrust, and gross weight increases by 1964, but further development had been hampered by four fundamental obstacles:

1. Suitable pure-jet engine availability.

2. Discontinuation of promising engine development because of several mid-1960s British engine manufacturer mergers.

3. Higher seat-mile costs over DC-3-like sectors for which the new design had been intended.

4. The inability to exploit a pure-jet airliner's speed over relatively short sectors.

Hawker Siddeley, believing that the turboprop engine had only been interim-step technology, had equally embarked on a pure-jet airliner design program of its own long before the de Havilland merger, although its low-wing, aft-engined, t-tailed configurations had strongly resembled its former competitor's.

Attempting to minimize development costs by utilizing the cockpit, forward fuselage, systems, and passenger cabin of its own Avro 748, it had proposed the HS.131 in 1964, which had featured similar 62.8-foot overall lengths and 67-foot wingspans as de Havilland's comparable DH.126, but its projected 5,000 thrust-pound Rolls Royce RB.172 engines had enabled it to offer a higher, 30,000-pound gross weight and a 32-passenger capacity.

Faced, like de Havilland, with engine unsuitability and unavailability, Hawker Siddeley devised iterations round projected powerplants. A radical configuration change, introduced by the HS.136 of 1967, for instance, had resulted in a low-wing aircraft powered by two 9,730 thrust-pound Rolls Royce Trent engines with a conventional tail accommodating 57 passengers in a five-abreast cabin and offering a 54,000-pound maximum take off weight. Although the arrangement would have eliminated the aft-mounted, t-tail's propensity toward deep-stall and flame-out conditions, and its close ground proximity would have facilitated passenger, aircraft servicing, and maintenance access, the potential for foreign object debris (FOD) engine ingestion had yielded to the proposed HS.144 two years later, which had once again reverted to the now standard aft-engine configuration.

Progressive design evolutions and dimensional and thrust increases had intermittently resulted in an airplane whose passenger capacity had been double that of the DC-3's, and with the Rolls Royce bankruptcy-sparked discontinuation of Trent development in 1970, the DC-3 replacement, now powerless, had become ever more elusive.

This low-capacity, short-range jetliner had, like never before, hinged upon a powerplant for its existence, and the only potential lay with a small turbofan being developed by Avco Lycoming in the US. Based upon the 7,000 thrust-pound F102 which had powered the Northrop A-9A, the engine, a derated civil derivative designated ALF-502, had been launched in 1969 for the Canadair CL-601 Challenger business jet and had first run two years later. In order to offer commercial application, it had been of modular construction.

Because the type's 6,500 thrust-pound rating had been inadequate for the latest aircraft design, the HS.146 of 1971, and because no other suitable powerplant had been in the development stage, the ultimate DC-3 replacement had been forcibly designed round four, not two, engines and it featured neither the standard, aft engine-mounted, t-tailed nor alternative wing-mounted configuration. Instead, it would sport two high, modestly swept wings to which the four turbofans would be pylon-mounted. Accommodating 88 passengers, or three times as many as the DC-3, the airliner, with an 86.2-foot length and 84.10-foot wingspan, had a 70,000-pound gross weight and 700-nautical mile range.

Nevertheless, the HS.146 offered several advantages over the earlier, standard-arrangement de Havilland and Hawker Siddeley design studies. Short-field performance, fully the equivalent of the turboprops it had intended to replace, had been attained by its thrust-to-weight ratio and wing, which, with 78-percent coverage of its trailing edge with Fowler flaps, had obviated the need for leading edge devices, and simplification and weight reduction had been further achieved with the elimination of thrust reversers. The t-tail, remaining from the earlier designs, had been retained in order to avoid engine and wing turbulence interference.

The four engine pods, which had been interchangeable with each other, housed modular construction cores built up of the basic fan, the accessory gearbox, the gas producer/compressor, and the combustion turbine sections.

An 11.8-foot fuselage diameter had permitted an internal, six-abreast coach seating arrangement, which had been double that of the DC-3's.

In order to cater to different route demands, Hawker Siddeley offered an initial, 88-passenger HS-146-100 and a stretched, 102-passenger HS.146-200 version, both at maximum, six-abreast densities, although capacity could be reduced with varying class, seat pitch, and abreast arrangements.

Fully intended as a pure-jet counterpart to the turboprop Viscount, HS.748, and F.27, the HS.146 had been optimized for multiple daily, high frequency, short-range sectors from short and unprepared, gravel runways, yet achieve 15-percent lower direct-operating-costs than these aircraft. Slow, controlled approach speeds, of just over 100 knots, had been attainable by its aft fuselage, petal airbrakes and 40 degrees of trailing edge flap, permitting operation from 5,000-foot runways.

Hawker Siddeley had estimated a market of 1,500 aircraft of its type by 1982.

HS.146 program launch, based upon a 40 million British pound government backing and the manufacturer's own investment, had occurred on August 29, 1973, and the first flight, of the short-fuselage HS.146-100, had been targeted for December of that year with certification following in February of 1977, while the stretched HS.146-200, coinciding with the seventh airframe, had been targeted for certification in August of 1978. A full-scale wooden mock-up had been intermittently built at Hatfield.

Like so many British commercial projects, its momentum had been abruptly arrested a little more than a year after it had been initiated. Escalating fuel prices resulting from the Arab-Israeli Yom Kippur War, changing economic conditions, and a general recession, coupled with the pending nationalization of the UK aircraft industry, had rendered the HS.146 program economically unfeasible by October of 1974. As a result, it had been halted, although small-scale engineering had continued and the aircraft's drawings, tools, and jigs had been retained.

Three years later, on March 15, 1977, British Aerospace had been formed with the merger of Hawker Siddeley and the British Aircraft Corporation, and the design, redesignated BAe-146, had been relaunched. It had been the first to have been undertaken by the new conglomerate the following year, on July 10, 1978.

Rolled out for the first time three years later on May 20, 1981 at Hatfield, the aircraft, registered G-SSSH, became the first new British design since the BAC-111 had flown 18 years earlier.

The aircraft, in its original BAe-146-100 form, featured a pressurized, semi-monocoque, aluminum alloy/copper fuselage whose inner fuselage frames bore the aircraft's bending loads and whose outer, notched rings carried the sheer loads, a construction technique which eliminated some 5,000 stringer/frame cleats. Its 11.8-foot diameter, permitting five- or six-abreast coach seating, had ensured that passengers would enjoy the same comfort on the type's typical feeder routes as that offered by wide body aircraft operating long-range sectors to which they often transferred.

Single-class capacity varied from 71 in a five-abreast, 33-inch configuration to 82 at a six-abreast, 33-inch arrangement and an ultimate 93 at a six-abreast, 29-inch density. Total capacity decreased with a forward, 12-seat, first class cabin in a four-abreast configuration.

The aircraft had an 85-foot, 11½-inch overall length.

The wings, with an 86-foot span and 832-square-foot area, had featured a 15-degree sweepback and three degrees of anhedral at their leading edges. Due to the aircraft's short, 150-nautical mile sectors, cruise speeds higher than its optimized Mach 0.7 had not been necessary and had therefore obviated the need for greater sweepback. Low-speed, short-field performance had been attained by means of its single-section, tabbed, trailing edge Fowler flaps which, with a 210-square-foot area, had covered 78 percent of the span and had been hydraulically operated by Dowty Rotol actuators. Roll control had been provided by manually-operated, trim- and servo tab-equipped ailerons, which operated in conjunction with each outer wing's hydraulically-actuated roll spoilers. Three additional inboard spoilers served as lift dumpers after touch down.

Power had been provided by four Textron Lycoming ALF-502R-5 turbofans, each rated at 6,970 pounds of thrust, and these had replaced the lower-thrust, 6,700-pound ALF-502Hs originally intended for the design. Avco Lycoming had since become "Textron Lycoming."

A total of 3,098 US gallons of fuel could be carried in two wing integral and one center section tank, the latter located above the passenger cabin and equipped with a vented and drained sealing diaphragm. The single-point pressure fueling had been located on the right wing, outboard of the number four engine.

The fixed horizontal tailplane, mounted atop the vertical fin, had not required the standard variable-incidence geometry because the absence of wing leading edge devices had eliminated the balance-out requirements ordinarily associated with the latter's pitch changes. Its location, avoiding wing downwash and engine thrust interference, provided the greatest moment-arm, thus reducing required area and weight. Its elevators had been manually operated, while the vertical fin's rudder had been hydraulically actuated.

Key to the BAe-146 design had been the 40-square-foot, hydraulically-actuated petal air brakes forming an integral, aerodynamic part of the tailcone at the extreme end of the fuselage and deployable to a maximum 60-degree position. Augmenting slow, controlled, increased descent rates, they had enabled the aircraft to descend at 7,000 fpm above 10,000 feet and 4,000 fpm below it, facilitating short-runway operation and eliminating the need for thrust reversers.

The aircraft's hydraulically-operated, tricycle undercarriage had been comprised of a steerable, telescope strut-attached, forward-retracting nose wheel and two outboard-displaced main units which retracted inwards into blister-type fairings on the fuselage's sides. All featured Dunlop wheels, while the main gear's multi-disc carbon brakes had only been previously employed by Concorde.

Two 3,000-psi hydraulic systems powered the trailing edge flaps, the petal air brakes, the undercarriage, and the wheel brakes. A Garrett AiResearch GTCP 36-100M auxiliary power unit had provided cabin conditioning and engine starting power and had been operable up to 20,000 feet.

With an 84,000-pound maximum take off weight, the BAe-146-100 had an 880-nautical mile range with its maximum payload and a 1,620-nautical mile range with its maximum fuel.

First flying on September 3, 1981, on a one-hour, 35-minute fight at a 64,000-pound take off weight, the BAe-146-100 had been pronounced as "remarkably stable, very responsive, and delightfully quiet" by its test pilot and had been awarded its Civil Aviation Authority (CAA) type certificate on February 4, 1983. FAA certification followed three months later, on May 20.

Dan-Air Services, Ltd., the type's launch customer, had placed two firm and two optioned orders the previous September, and inaugurated it into scheduled service on March 1, 1983, with an intermittently-provided aircraft from British Aerospace, on the London/Gatwick-Berne, Switzerland route, before it deployed its own aircraft on the route as of May 27. The BAe-146 had been the only pure-jet airliner which had been capable of operating from Berne's short runway.

The larger, BAe-146-200, with a five-frame stretch, featured a new, 93.10-foot overall length and could accommodate 100 passengers in a six-abreast configuration at a 33-inch seat pitch or a maximum of 112 at a 29-inch pitch, but otherwise retained the BAe-146-100's wingspan. The aircraft, with a 93,000-pound maximum take off weight, had a 1,130-nautical mile range with a full payload or a 1,570-nautical mile range with full fuel.

First flying on August 1, 1982 and registered G-WISC, the type had been inaugurated into service the following year, on June 27, by Air Wisconsin, which had placed an order for four firm and four optioned aircraft, configured for 100, on May 20, 1981, the same day that the shorter-fuselage variant had first rolled out. Joining a fleet of Fairchild Swearingen Metro IIs and de Havilland of Canada DHC-7 turboprops, the BAe-146-200 had been deployed on average, 127-mile route sectors, rarely climbing higher than 17,000 feet, and by the spring of 1984, it had served 16 mid-western cities, operating 14 daily sectors per day. It ultimately replaced the turboprops.

The largest single order, for 20 firm and 25 options, had been placed by another US regional carrier, Pacific Southwest Airlines (PSA), while other US operators had included Air-Pac of the Aleutian Islands in Alaska, Aspen Airways, Air-Cal, American Airlines, Discovery Airways of Hawaii, Presidential Airways, Royal West, USAir, and WestAir Commuter.

The BAe-146 had been the first pure-jet to have been certified to operate from London City STOLport, located in the docklands region, because of its steep approach capability, short-runway performance, and low noise emission.

In order to further expand its product line, offer increased passenger capacity, and more adequately compete with Fokker's own advanced, stretched F.100, British Aerospace offered a second stretch over its original BAe-146-100, which had entailed 8.1-foot forward and 7.8-foot aft fuselage plugs in comparison to the BAe-146-200. The resultant version, the BAe-146-300, featured a strengthened center section fuselage and a new 100-foot, 8 ¼-inch overall length, but otherwise employed the same wingspan and ALF-502R-5 turbofans. Single-class, five-abreast capacity, at a 31-inch seat pitch, had been 103, although 128 high-density passengers, at a 29-inch seat pitch, could be accommodated with the addition of type III emergency exits installed in the center fuselage. The 97,500-pound variant, with a 1,040-nautical mile range with a full payload and a 1,520-nautical mile range with full fuel, had first flown on May 1, 1987, after the BAe-146-100 prototype (G-SSSH) had been converted to this standard and reregistered G-LUXE.

Air Wisconsin, again launch customer for the version, had taken delivery of its first longer-fuselage BAe-146-300 on December 10, 1988, one of five which had comprised its previous order for -200s.

A freighter version, the BAe-146-QT Quiet Trader, had been available in all three passenger versions. Incorporating an upward-opening, hydraulically-operated, 10.11-by-6.4 foot door on its aft, left side; a strengthened floor; and a loading system; the aircraft, devoid of passenger windows and facilities, could accommodate nine LD-3 containers or six 108-by-88 inch pallets of up to 6,000 pounds each and a single 53-by-88 inch half pallet. The prototype, a BAe-146-200 converted by Hayes International Corporation, had first flown on March 20, 1986 and had been inaugurated into service by TNT International Aviation Services the following year on May 5. The operator had subsequently acquired a considerable number of them.

II

A representative BAe-146-200 flight, operated by Air Zimbabwe from Hwange to Kariba, had been taken in September of 1994.

Founded in 1967 as Air Rhodesia to operate the Rhodesian routes of Central African Airways, the carrier, continually changing as a result of increased black majority rule, had been redesignated Air Rhodesia-Zimbabwe in 1979 and, simply, Air Zimbabwe the following year after the country had attained independence. The transition period, fraught with political instability, had sparked constant route structure realignment, which had only encompassed South Africa.

When the internal situation had ultimately been restabilized, the route system had been gradually reestablished, once again offering connections between Zimbabwe and many regional African nations, as well as those in Europe. In 1982, Air Zimbabwe had operated eight Viscounts, three 720Bs, and three 707-320Bs, although additional 707s had later replaced the 720s.

Due to deregulation-spawned competition, the small carrier had increased its efforts to remain competitive with improved passenger service and a more modern, three-type fleet which had included one BAe-146-200, three 737-200s, and two 767-200ERs, serving the five Zimbabwean domestic destinations of Bulawayo, Harare, Hwange, Kariba, and Victoria Falls; the 11 African international destinations of Dar-es-Salaam, Durban, Gabarone, Johannesburg, Lilongwe, Lusaka, Manzini, Maputo, Mauritius, Nairobi, and Windhoek; and the three European intercontinental destinations of Frankfurt, Larnaca, and London.

In June of 1983, it had embarked on a "Customer Care Program" to improve service and introduce a new Executive Business Class on its two widebody aircraft in order to more effectively compete with the larger, international carriers which had operated between Europe and Africa.

It had toted three slogans: "A Tradition of Caring," in 1989; "Above All, We Care," in 1992; and "Experience our Commitment to Excellence," in 1994.

Its self-stated goal had been "to be the airline that best meets the needs of the customer, to operate profitably, and to contribute to the development of Zimbabwe using the skills and talents of a committed workforce."

The BAe-146-200 operating the day's flight, registered Z-WPD and named "Jungwe," had been configured with 91 single-class, six-abreast seats and had been fitted with a passenger audio system. Routed from Victoria Falls to Hwange, Kariba, and Harare under flight number "UM 229," it operated three sectors spanning 30 minutes, one hour, and 45 minutes in duration.

After boarding from the single terminal by means of its forward, left airstair, the high-wing, quad-engined British regional jet, sporting its colorful black, red, yellow, and green striped livery, executed a lengthy taxi roll on the concrete runway flanked on either side by Hwange National Park's dry, brown grass and scrub expanses, periodically interspersed by feeding herds of impalas.

Completing its "Before Take Off" checklist, and extending its trailing edge Fowler flaps to their 24-degree position, the aircraft throttled into its acceleration roll, its four ALF-502R-5 turbofans propelling its 35,500-kilo mass with their 6,970 pounds of thrust into life-generating speed. Leveraging itself into rotation at 112 knots with its horizontal tail-hinged elevator, the BAe-146 surrendered itself to the hot African atmosphere at a 118-knot V2 velocity, retracting its tricycle undercarriage and accelerating through a 171-knot VFTO speed toward the gray, obscuring ceiling.

Leaning into a right bank over the brown and tan African expanse at 4,200 feet, the BAe-146 retracted its flaps from the 24- to the 0-degree position, completing its "After Take Off" checklist. Ascending through 7,600 feet, at which time a 291-knot ground speed had been registered, it maintained a 1,800-fpm climb rate. Its NAV indicated a 135.4-mile distance to Kariba.

Plunging through the dirty opaque obscurity at 15,780 feet, Fight 229 triumphed over white, mountainous-appearing cumulous, now unrestrictedly bulleting through the illustriously-blue mid-afternoon purity at 18,640 feet.

Inching the throttle back a moment later, the British regional liner settled into its 21,000-foot level off plateau at a 354-knot ground speed with 97.7 miles remaining to its destination.

Cabin service on the one-hour domestic sector had included a selection of sodas, mineral water, orange juice, and lemonade and a snack try of potato chips and peanuts.

The ground speed had pinnacled at 411 knots.

Descent, initiated with 54 miles remaining on its flight plan, had been attained by dialing in 5,500 feet in the cockpit's "ALT SEL" autopilot, resulting in a 2,000-fpm descent rate.

Surrendering once again to the dense, reference-losing obscurity of the cloud deck, the aircraft plunged through 10,000 feet at a 260-knot speed with 21 miles remaining to Kariba, extending its petal air brakes at 7,000 feet, which produced a very controlled, but drag-induced profile. An altitude of 4,500 feet had been intermittently dialed into the "ALT SEL" window.

Emerging from the ceiling mist over the baby blue of Lake Kariba, which had been outlined by its dry, tan and brown scrub shoreline, the captain consulted his landing flap chart corresponding to a 34,500-kilo weight.

Extending its Fowler flaps to the 18-degree position at 3,600 feet, at which time 6.4 miles had remained on its flight plan, the airliner unleashed its undercarriage at a 162-knot ground speed and actuated its high-lift devices into the 24-degree position while arcing into a left bank over the parched expanse of desert. Black mountain silhouettes rolled into view ahead of the cockpit windows.

Descending through 2,600 feet at a 161-knot ground speed, the BAe-146-200, now sporting 33 degrees of trailing edge flap, maintained a 270-degree heading, the runway, seemingly plowed between brown straw, visible through the windshield.

Extending its petal air brakes to the 60-degree position, the aircraft, at a negligible descent rate, passed over Runway 27's threshold at 120 knots, retarding its throttle and flaring into main undercarriage contact with the sizzilingly hot concrete. Decelerating with significant brake applications, and with its spoiler handle already deployed to the "LIFT SPLR" position, the thrust reverser-devoid quad-jet consumed the centerline with its nose wheel until it had reached its other threshold and could execute a 180-degree turn.

Taxiing toward the single terminal's ramp amid the sweltering, 94-degree heat, the high-wing, t-tailed airliner, although ordinarily minuscule next to an intercontinental wide body, dwarfed the United Air PA-23 Aztec and collection of private pistons now parked around it.

The BAe-146 had, as evidenced by this sector, served as Zimbabwe's link between its often road-unconnected cities and communities.

III

Although the British Aerospace BAe-146 had only sold 219 examples of all of its versions to 45 world airlines, it had nevertheless formed the basis of its later, more advanced, Textron Lycoming LF507-powered Avro RJ70, RJ85, and RJ100 derivatives.


Source by Robert Waldvogel

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