In safe-life design , products are intended to be removed from service at a specific design life .
71-465: The Hawker Siddeley HS 748 (formerly Avro HS 748 ) is a medium-sized turboprop airliner originally designed and initially produced by the British aircraft manufacturer Avro . It was the last aircraft to be developed by Avro prior to its absorption into Hawker Siddeley. The HS 748 was developed during the late 1950s as a move to re-orient the company towards the civil and export markets. Powered by
142-400: A Pratt & Whitney Canada PT6 , and an under-speed governor on a Honeywell TPE331 . The turboprop is also distinguished from other kinds of turbine engine in that the fuel control unit is connected to the governor to help dictate power. To make the engine more compact, reverse airflow can be used. On a reverse-flow turboprop engine, the compressor intake is at the aft of the engine, and
213-424: A propelling nozzle . Air enters the intake and is compressed by the compressor. Fuel is then added to the compressed air in the combustor, where the fuel-air mixture then combusts . The hot combustion gases expand through the turbine stages, generating power at the point of exhaust. Some of the power generated by the turbine is used to drive the compressor and electric generator . The gases are then exhausted from
284-465: A bombing raid. In 1941, the engine was abandoned due to war, and the factory converted to conventional engine production. The first mention of turboprop engines in the general public press was in the February 1944 issue of the British aviation publication Flight , which included a detailed cutaway drawing of what a possible future turboprop engine could look like. The drawing was very close to what
355-494: A current Certificate of Registration. Current operators are: Data from Jane's Civil and Military Aircraft Upgrades, 1994–95 , BAE Systems General characteristics Performance Related development Aircraft of comparable role, configuration, and era Related lists Turboprop A turboprop is a turbine engine that drives an aircraft propeller . A turboprop consists of an intake , reduction gearbox , compressor , combustor , turbine , and
426-471: A dihedral would have to be introduced to keep the tailplane clear of the jet exhaust. It was envisioned that the reengined aircraft could offer larger seating arrangements of up to 64 seats. In addition to the British production line, manufacture of the 748 was also performed overseas. Early on, India had placed orders for the type. Both the 748 Series 1 and Series 2 were licence-produced by Indian manufacturer Hindustan Aeronautics (HAL), aircraft produced by
497-450: A four abreast layout; however, the majority of later-serving passenger HS 748s were typically operated as quick change combis . These aircraft are fitted with a movable bulkhead that divides the main cabin, housing between 4 and 40 seats in the rear section while cargo is placed in the forward section. The 748 has also been widely used as a pure freighter, having a typical maximum payload of about 12,000 lbs. Several carriers have used
568-442: A governor, and overspeed governor, and a fuel-topping governor. The governor works in much the same way a reciprocating engine propeller governor works, though a turboprop governor may incorporate beta control valve or beta lift rod for beta operation and is typically located in the 12 o'clock position. There are also other governors that are included in addition depending on the model, such as an overspeed and fuel topping governor on
639-566: A greater emphasis upon the civilian market. Ten years prior, it had launched a civilian airliner, the Avro Tudor series, but this had encountered few sales; thus, during 1958, it was decided to commence work upon a clean-sheet design, which would eventually become the HS 748. On 9 January 1959, the existence of the project, then referred to as the Avro 748 , was announced to the public. By this point,
710-504: A low-wing 40-seat configuration. It was this latter arrangement that was chosen for the 748 project. Another important focus for the prospective airliner was compliance with both British and American standards of airworthiness ; accordingly, it would be one of the first medium-sized aircraft to incorporate fail-safe design principles for its structure in place of the then-common safe-life principles being practiced. The airframe effectively lacked any imposed lifespan; during development, it
781-453: A major goal for the design team was to produce an aircraft that would be capable of operating from any airfield from which the DC-3 could be operated. Early intentions for the airliner was planned to be a 20–30 seat aircraft, adopting a somewhat similar configuration to the future rival Fokker F27 Friendship ; however, following discussions with several potential customers, the company opted for
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#1732791002148852-410: A mode typically consisting of zero to negative thrust, is used for all ground operations aside from takeoff. The Beta mode is further broken down into 2 additional modes, Beta for taxi and Beta plus power. Beta for taxi as the name implies is used for taxi operations and consists of all pitch ranges from the lowest alpha range pitch, all the way down to zero pitch, producing very little to zero-thrust and
923-419: A pair of HS 748s starting in 1973 as a navigational trainer. Following Cyclone Tracy , relief aid was delivered across Darwin, Northern Territory , using the type; after being fitted with various electronic countermeasures (ECM) during the late 1970s, HS 748s were also used for electronic warfare training. In a typical passenger configuration, the HS 748 can accommodate around 40–48 economy class seats in
994-446: A primary load-bearing member should fail, whereas the latter has alternative load paths so that if a primary load-bearing member cracks, residual strength remains because the loads can be assumed by adjacent members. In modern aircraft, fail-safe structures with up to three alternative load paths are provided, but back in 1947 the main load-bearing structure was safe life. This did not matter on an interim airframe designed for operations in
1065-581: A small amount of air by a large degree, a low disc loading (thrust per unit disc area) increases the aircraft's energy efficiency , and this reduces the fuel use. Propellers work well until the flight speed of the aircraft is high enough that the airflow past the blade tips reaches the speed of sound. Beyond that speed, the proportion of the power that drives the propeller that is converted to propeller thrust falls dramatically. For this reason turboprop engines are not commonly used on aircraft that fly faster than 0.6–0.7 Mach , with some exceptions such as
1136-452: A strengthened cabin floor. During 1979, the Series 2B was introduced, which saw a 4-foot increase in wingspan , the adoption of Mk 536-2 engines, along with a modernised passenger cabin, and various improvements to the fuel, water methanol injection system , and engine fire protection systems . During 1976, Eric Johnson, sales engineering manager of Hawker Siddeley Manchester, stated that
1207-591: A test-bed not intended for production. It first flew on 20 September 1945. From their experience with the Trent, Rolls-Royce developed the Rolls-Royce Clyde , the first turboprop engine to receive a type certificate for military and civil use, and the Dart , which became one of the most reliable turboprop engines ever built. Dart production continued for more than fifty years. The Dart-powered Vickers Viscount
1278-489: Is coupled to the turbine through a reduction gear that converts the high RPM /low torque output to low RPM/high torque. This can be of two primary designs, free-turbine and fixed. A free-turbine turboshaft found on the Pratt & Whitney Canada PT6 , where the gas generator is not connected to the propeller. This allows for propeller strike or similar damage to occur without damaging the gas generator and allowing for only
1349-446: Is employed in critical systems which are either very difficult to repair or whose failure may cause severe damage to life and property. These systems are designed to work for years without requirement of any repairs. The disadvantage of the safe-life design philosophy is that serious assumptions must be made regarding the alternating loads imposed on the aircraft, so if those assumptions prove to be inaccurate, cracks may commence prior to
1420-434: Is reliant on many conditions, including the ratio of maximum load to minimum load (R-ratio), the type of material being inspected, and the regularity at which the cyclic stresses (or strains) are applied. Today, the curve is still consequential by experimentally testing laboratory specimens at many continuous cyclic load levels, and detecting the number of cycles to failure (Oja 2013). Michael Oja states that, “Unsurprisingly, as
1491-407: Is that it can also be used to generate reverse thrust to reduce stopping distance on the runway. Additionally, in the event of an engine failure, the propeller can be feathered , thus minimizing the drag of the non-functioning propeller. While the power turbine may be integral with the gas generator section, many turboprops today feature a free power turbine on a separate coaxial shaft. This enables
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#17327910021481562-421: Is typically accessed by moving the power lever to a beta for taxi range. Beta plus power is a reverse range and produces negative thrust, often used for landing on short runways where the aircraft would need to rapidly slow down, as well as backing operations and is accessed by moving the power lever below the beta for taxi range. Due to the pilot not being able to see out of the rear of the aircraft for backing and
1633-634: The P-3 Orion , and the C-130 Hercules military transport aircraft. The first turbine-powered, shaft-driven helicopter was the Kaman K-225 , a development of Charles Kaman 's K-125 synchropter , which used a Boeing T50 turboshaft engine to power it on 11 December 1951. December 1963 saw the first delivery of Pratt & Whitney Canada's PT6 turboprop engine for the then Beechcraft 87, soon to become Beechcraft King Air . 1964 saw
1704-841: The Piper Meridian , Socata TBM , Pilatus PC-12 , Piaggio P.180 Avanti , Beechcraft King Air and Super King Air . In April 2017, there were 14,311 business turboprops in the worldwide fleet. Between 2012 and 2016, the ATSB observed 417 events with turboprop aircraft, 83 per year, over 1.4 million flight hours: 2.2 per 10,000 hours. Three were "high risk" involving engine malfunction and unplanned landing in single‑engine Cessna 208 Caravans , four "medium risk" and 96% "low risk". Two occurrences resulted in minor injuries due to engine malfunction and terrain collision in agricultural aircraft and five accidents involved aerial work: four in agriculture and one in an air ambulance . Jane's All
1775-614: The Tupolev Tu-114 can reach 470 kn (870 km/h; 540 mph). Large military aircraft , like the Tupolev Tu-95 , and civil aircraft , such as the Lockheed L-188 Electra , were also turboprop powered. The Airbus A400M is powered by four Europrop TP400 engines, which are the second most powerful turboprop engines ever produced, after the 11 MW (15,000 hp) Kuznetsov NK-12 . In 2017,
1846-403: The Tupolev Tu-95 . However, propfan engines, which are very similar to turboprop engines, can cruise at flight speeds approaching 0.75 Mach. To maintain propeller efficiency across a wide range of airspeeds, turboprops use constant-speed (variable-pitch) propellers. The blades of a constant-speed propeller increase their pitch as aircraft speed increases. Another benefit of this type of propeller
1917-554: The 1990s, a larger, stretched development of the HS 748, the BAe ATP , was developed and had attempted to compete with market leaders such as the de Havilland Canada Dash 8 and ATR 42 , but saw only limited sales prior to production being terminated. Following the release of the 1957 Defence White Paper , in which then- Minister of Defence Duncan Sandys announced the termination of almost all manned military aircraft development, aircraft manufacturer Avro decided that it should place
1988-503: The 748 as a bulk fuel hauler, in which capacity it is normally with either seven or eight fixed tanks in the cabin, possessing a total capacity of about 7,500 L (1,600 imp gal; 2,000 US gal). The ICAO designator as used in flight plans is A748. As of July 2020, a total of 13 HS 748 aircraft (all variants) remained in airline service. As of May 2023, Transport Canada (TC) listed 7 HS 748 in Canada with
2059-560: The Advanced Composite Airframe Program (ACAP), and Manufacturing Methods and Technology (MM&T) projects, such as UH-60 Low Cost Composite Blade Program, it is estimated that within a few years composite materials could be applied to as much as 80% of the airframe and rotor weight of a helicopter in a production program” (Reddick). Along with this application, it is the essential obligation that sound, definitive design criteria be industrialized in order that
2130-609: The F27's largest operator prior to its decision to replace both it and its remaining DC-3s with the HS 748, which represented a significant sales coup for Hawker-Siddeley. Other major civil operators included Aerolíneas Argentinas , VARIG , Thai Airways , LAN-Chile , and Bouraq Airlines . Several of these operators would utilise its STOL capabilities in their services; according to Flight International, over one-third of all scheduled operations reportedly involved operations from rough airstrips with minimalist facilities. Another key market for
2201-473: The HS 748 was the executive role; the type was repeatedly procured to serve as the designated aircraft for various heads of state , including those of Argentina , Brazil , Chile , India, Venezuela , Zambia , Thailand and the United Kingdom. The HS 748 was one of the last planes to be flown by noted aviator and business magnate Howard Hughes . During 1972, Hughes performed several flights of
Hawker Siddeley HS 748 - Misplaced Pages Continue
2272-639: The PWC 126/127 engines. Total production of this variant was only 67 aircraft. According to BAE Systems , a successor company to Hawker Siddeley, during the type's production life, a total of 381 aircraft had been produced, which included both the Andover and HAL-built examples. Within its first decade of its availability, sales of the HS 748 had reportedly been relatively brisk; by 1976, the sale of 312 aircraft had been recorded, of which 259 had been to export customers. Within ten years of its launch, India had emerged as
2343-533: The Soviet Union had the technology to create the airframe for a jet-powered strategic bomber comparable to Boeing's B-52 Stratofortress , they instead produced the Tupolev Tu-95 Bear, powered with four Kuznetsov NK-12 turboprops, mated to eight contra-rotating propellers (two per nacelle) with supersonic tip speeds to achieve maximum cruise speeds in excess of 575 mph, faster than many of
2414-461: The World's Aircraft . 2005–2006. Safe-life design Safe-life is particularly relevant to simple metal aircraft, where airframe components are subjected to alternating loads over the lifetime of the aircraft which makes them susceptible to metal fatigue . In certain areas such as in wing or tail components, structural failure in flight would be catastrophic. The safe-life design technique
2485-420: The additional expansion in the turbine system, the residual energy in the exhaust jet is low. Consequently, the exhaust jet produces about 10% of the total thrust. A higher proportion of the thrust comes from the propeller at low speeds and less at higher speeds. Turboprops have bypass ratios of 50–100, although the propulsion airflow is less clearly defined for propellers than for fans. The propeller
2556-671: The adoption of increasingly powerful Dart engines and a higher gross weight. Perhaps the most distinct variant was the HS 780 Andover , a dedicated military transport model developed for the Royal Air Force (RAF) that featured a large rear loading ramp and a squatting main landing gear to assist in loading bulky freight items. By 1988, the year in which production of the type was terminated, 380 aircraft had been produced between Hawker Siddeley (the owning company of Avro) and Indian aviation company Hindustan Aeronautics Limited (HAL). During
2627-530: The airliner were designed to be easy to inspect and to perform repairs upon, even when at unprepared airstrips with limited equipment available. Likely as a consequence of these favourable qualities, the 748 quickly attracted the attention of a variety of airlines, particularly those that typically operated in remote areas, which has been attributed to its ability to operate from short, rough fields without any ground service equipment while being capable of hauling payloads in excess of 10,000 lb. On 24 June 1960,
2698-414: The amount of debris reverse stirs up, manufacturers will often limit the speeds beta plus power may be used and restrict its use on unimproved runways. Feathering of these propellers is performed by the propeller control lever. The constant-speed propeller is distinguished from the reciprocating engine constant-speed propeller by the control system. The turboprop system consists of 3 propeller governors ,
2769-413: The basic price for a new Avro 748 Series 1 was £176,000, while that of the corresponding Avro 748 Series 2 was reportedly £196,000. During 1967, the series 2A was introduced, which was the same basic aircraft powered by Mk. 532 engines along with a further increase in gross weight. From 1971 onwards, several new options were made available to customers, including a large freight door in the rear cabin and
2840-516: The calm upper air, but at around 500 ft the loads and stresses were more volatile. The safe-life design philosophy is applied to all helicopter structures. In the current generation of Army helicopters, such as the UH-60 Black Hawk , composite materials make up as great as 17 percent of the airframe and rotor weight (Reddick). Harold Reddick states that, “With the advent of major helicopter composite structures R&D projects, such as
2911-585: The company was studying options for equipping a model of the HS 748 with turbofan engines, and that a preferred powerplant at that point was the Rolls-Royce/SNECMA M45H , as used on the VFW-Fokker 614 jetliner. Other changes would likely have been incorporated, including the addition of lift dumpers and adaptive brakes for better landing performance, while electrical, hydraulic and air conditioning systems would be redesigned; externally,
Hawker Siddeley HS 748 - Misplaced Pages Continue
2982-522: The company were designated HAL-748 . On 1 November 1961, the first Indian-assembled HAL-748 made its initial flight. By the end of production, HAL had completed 89 Indian-built aircraft, 72 of which were for the Indian Air Force and 17 were delivered to national flag carrier Indian Airlines . While the HS 748 was originally intended to be marketed principally towards the civilian market, numerous examples were sold to military customers around
3053-403: The component being removed from service. To counter this disadvantage, alternative design philosophies like fail-safe design and fault-tolerant design were developed. One way the safe-life approach is planning and envisaging the toughness of the mechanisms in the automotive industry. When the repetitive loading on mechanical structures intensified with the advent of the steam engine, back in
3124-593: The early 1960s, Avro's individual identity within the Hawker Siddeley Group was expunged, after which the airliner was marketed by the parent company as the HS 748 . After the initial batch of series 1 aircraft was completed, production transitioned to the improved series 2. The series 2 was largely similar to its predecessor, principally benefiting from the adoption of more powerful Dart RDa 7 Mk 531 engines and an increased gross weight. According to aviation periodical Flight International , during 1960,
3195-459: The easy mounting of strong landing gear . Operationally, pilots were provided with a choice of three takeoff flap settings to select the level of STOL performance required. Another supportive feature of the 748 was a design decision to adopt straightforward systems and use proven components where realistically possible. For operator convenience, the engines were provided with an internal ignition system; various other systems and structures throughout
3266-407: The exhaust is situated forward, reducing the distance between the turbine and the propeller. Unlike the small-diameter fans used in turbofan engines, the propeller has a large diameter that lets it accelerate a large volume of air. This permits a lower airstream velocity for a given amount of thrust. Since it is more efficient at low speeds to accelerate a large amount of air by a small degree than
3337-499: The first jet aircraft and comparable to jet cruising speeds for most missions. The Bear would serve as their most successful long-range combat and surveillance aircraft and symbol of Soviet power projection through to the end of the 20th century. The USA used turboprop engines with contra-rotating propellers, such as the Allison T40 , on some experimental aircraft during the 1950s. The T40-powered Convair R3Y Tradewind flying-boat
3408-458: The first Avro 748 made its maiden flight from the company's Woodford, Cheshire , aircraft factory. Flight testing of the two prototypes quickly validated the type's short-field performance. Eighteen Avro 748 Series 1 aircraft were produced; during April 1962, the first production aircraft were delivered to launch customer Skyways Coach-Air Limited . However, the majority of the series 1 were export sales to operator Aerolíneas Argentinas . During
3479-564: The first deliveries of the Garrett AiResearch TPE331 , (now owned by Honeywell Aerospace ) on the Mitsubishi MU-2 , making it the fastest turboprop aircraft for that year. In contrast to turbofans , turboprops are most efficient at flight speeds below 725 km/h (450 mph; 390 knots) because the jet velocity of the propeller (and exhaust) is relatively low. Modern turboprop airliners operate at nearly
3550-449: The four-engined Vickers Viscount had already secured the larger end of the short-haul market, therefore Avro decided that it would design a smaller regional airliner , powered by a pair of Rolls-Royce Dart turboprop engines. It was envisioned that this aircraft would be a suitable replacement for the many DC-3 Dakotas that were by then reaching the end of their economic lifespan. According to aviation periodical Flight International ,
3621-465: The future Rolls-Royce Trent would look like. The first British turboprop engine was the Rolls-Royce RB.50 Trent , a converted Derwent II fitted with reduction gear and a Rotol 7 ft 11 in (2.41 m) five-bladed propeller. Two Trents were fitted to Gloster Meteor EE227 — the sole "Trent-Meteor" — which thus became the world's first turboprop-powered aircraft to fly, albeit as
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#17327910021483692-598: The largest single market for the airliner, Indian Airlines being the largest HS 748 operator with a fleet of 26 aircraft. It had been popular with numerous commercial operators; across the Caribbean and Latin America alone, 63 HS 748s were in operation with 11 separate operators. The HS 748 had been able to achieve some triumphs over competing rivals, including the F27 Friendship. Philippine Airlines had been
3763-437: The load decreases, the life of the specimen increases” (Oja 2013). The practical limit of experimental challenges has been due to frequency confines of hydraulic-powered test machines. The load at which this high-cycle life happens has come to be recognized as the fatigue asset of the material (Oja 2013). There are two generic types of aircraft structure, safe life and fail safe. The former is one that has low residual strength if
3834-460: The loading of bulky freight items. The 780 also used the more powerful RDa.10/1 3,245 hp (2,419.80 kW) estimated power at 15,000 rpm, with Water/Methanol injection During 1988, production of the HS 748 was terminated, while the last British-assembled aircraft made its first flight on 1 December of that year. BAE then started producing a product improved, stretched version the BAE ATP 61 which uses
3905-424: The mid-1800s, this approach was established (Oja 2013). According to Michael Oja, “Engineers and academics began to understand the effect that cyclic stress (or strain) has on the life of a component; a curve was developed relating the magnitude of the cyclic stress (S) to the logarithm of the number of cycles to failure (N)” (Oja 2013). The S-N curve because the fundamental relation is in safe life designs. The curve
3976-671: The most widespread turboprop airliners in service were the ATR 42 / 72 (950 aircraft), Bombardier Q400 (506), De Havilland Canada Dash 8 -100/200/300 (374), Beechcraft 1900 (328), de Havilland Canada DHC-6 Twin Otter (270), Saab 340 (225). Less widespread and older airliners include the BAe Jetstream 31 , Embraer EMB 120 Brasilia , Fairchild Swearingen Metroliner , Dornier 328 , Saab 2000 , Xian MA60 , MA600 and MA700 , Fokker 27 and 50 . Turboprop business aircraft include
4047-418: The popular Rolls-Royce Dart turboprop engine, it was specifically designed as a modern feederliner to act as a replacement for the aging Douglas DC-3s then in widespread service. Originally intended to seat a smaller number of passengers, market research indicated that a seating capacity of around 40 passengers would be optimal for the type. As a means to differentiate the new airliner from competitors, it
4118-493: The power section (turbine and gearbox) to be removed and replaced in such an event, and also allows for less stress on the start during engine ground starts. Whereas a fixed shaft has the gearbox and gas generator connected, such as on the Honeywell TPE331 . The propeller itself is normally a constant-speed (variable pitch) propeller type similar to that used with larger aircraft reciprocating engines , except that
4189-534: The propeller to rotate freely, independent of compressor speed. Alan Arnold Griffith had published a paper on compressor design in 1926. Subsequent work at the Royal Aircraft Establishment investigated axial compressor-based designs that would drive a propeller. From 1929, Frank Whittle began work on centrifugal compressor-based designs that would use all the gas power produced by the engine for jet thrust. The world's first turboprop
4260-403: The propeller-control requirements are very different. Due to the turbine engine's slow response to power inputs, particularly at low speeds, the propeller has a greater range of selected travel in order to make rapid thrust changes, notably for taxi, reverse, and other ground operations. The propeller has 2 modes, Alpha and Beta. Alpha is the mode for all flight operations including takeoff. Beta,
4331-452: The prospective airliner to be operated from smaller and more austere airports, including those without modern runways . This STOL capability was accomplished via several features, including the adoption of a long, high lift wing , which was fitted with a unique single slot flap with a hinged flap tab at the trailing edge . This wing was mounted low on the fuselage with dihedral from the root, allowing for good overall ground clearance and
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#17327910021484402-592: The same speed as small regional jet airliners but burn two-thirds of the fuel per passenger. Compared to piston engines, their greater power-to-weight ratio (which allows for shorter takeoffs) and reliability can offset their higher initial cost, maintenance and fuel consumption. As jet fuel can be easier to obtain than avgas in remote areas, turboprop-powered aircraft like the Cessna Caravan and Quest Kodiak are used as bush airplanes . Turboprop engines are generally used on small subsonic aircraft, but
4473-415: The turbine. In contrast to a turbojet or turbofan , the engine's exhaust gases do not provide enough power to create significant thrust, since almost all of the engine's power is used to drive the propeller. Exhaust thrust in a turboprop is sacrificed in favor of shaft power, which is obtained by extracting additional power (beyond that necessary to drive the compressor) from turbine expansion. Owing to
4544-546: The type, each time accompanied by Hawker Siddeley test pilot Tony Blackman , flying from the company's airport in Hatfield , Hertfordshire . The Australian military purchased several aircraft; specifically, the Royal Australian Air Force (RAAF) procured a fleet of ten HS 748s, the first of which arrived in 1968 for navigation training and transporting VIPs . The Royal Australian Navy (RAN) operated
4615-399: The world. Hawker Siddeley used the design as the basis for the HS 780 Andover , a military transport aircraft developed and produced for the Royal Air Force . In terms of its design, the HS 780 was broadly similar to the 748, differing primarily by its redesigned rear fuselage and empennage , which incorporated a large rear loading ramp and a squatting main landing gear to better facilitate
4686-573: Was designed by the Hungarian mechanical engineer György Jendrassik . Jendrassik published a turboprop idea in 1928, and on 12 March 1929 he patented his invention. In 1938, he built a small-scale (100 Hp; 74.6 kW) experimental gas turbine. The larger Jendrassik Cs-1 , with a predicted output of 1,000 bhp, was produced and tested at the Ganz Works in Budapest between 1937 and 1941. It
4757-401: Was designed to possess a high level of performance, including its short takeoff and landing (STOL) capabilities and overall ruggedness. First flying on 24 June 1960, the series 1 HS 748 entered revenue service in 1961. Once in service, the HS 748 found itself a niche within the short-haul market. Several different models would be developed of the regional airliner , typical improvements being
4828-467: Was of axial-flow design with 15 compressor and 7 turbine stages, annular combustion chamber. First run in 1940, combustion problems limited its output to 400 bhp. Two Jendrassik Cs-1s were the engines for the world's first turboprop aircraft – the Varga RMI-1 X/H . This was a Hungarian fighter-bomber of WWII which had one model completed, but before its first flight it was destroyed in
4899-714: Was operated by the U.S. Navy for a short time. The first American turboprop engine was the General Electric XT31 , first used in the experimental Consolidated Vultee XP-81 . The XP-81 first flew in December 1945, the first aircraft to use a combination of turboprop and turbojet power. The technology of Allison's earlier T38 design evolved into the Allison T56 , used to power the Lockheed Electra airliner, its military maritime patrol derivative
4970-531: Was successfully tested using a water tank for up to the equivalent of 100,000 flight hours. Avro was not the only company to see the potential for a DC-3 replacement and, by this point, work on the 748's direct competitor, the Dutch -built F27 Friendship, was well advanced. To differentiate itself from the competition, Avro decided to focus its efforts upon achieving a more rugged design that offered superior short takeoff and landing (STOL) performance, which enabled
5041-603: Was the first turboprop aircraft of any kind to go into production and sold in large numbers. It was also the first four-engined turboprop. Its first flight was on 16 July 1948. The world's first single engined turboprop aircraft was the Armstrong Siddeley Mamba -powered Boulton Paul Balliol , which first flew on 24 March 1948. The Soviet Union built on German World War II turboprop preliminary design work by Junkers Motorenwerke, while BMW, Heinkel-Hirth and Daimler-Benz also worked on projected designs. While
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