Imperial Airlines was a United States commuter airline that operated from 1964 to 1986. Imperial served a number of cities in Southern California and for a brief period several cities in Arizona.
57-844: Imperial was founded as Visco Flying Service in 1964, but later the scheduled passenger service portion of the company changed its name to Imperial Airlines . Visco Flying Service continued to operate as a crop dusting service in the Imperial Valley, for a number of years utilizing Stearman bi-wing biplane aircraft and later added helicopter aerial application as well as a turboprop powered mono-wing crop dusting aircraft. Imperial's passenger carrying operations were operated under FAR135 that initially focused on services from its home base at Imperial County Airport (IPL) in El Centro, CA to San Diego's Lindbergh Field (SAN). On January 8, 1968, at 10:40 a.m. an Imperial Beech E18S flown by
114-653: A W shape cabane, however as it does not connect the wings to each other, it does not add to the number of bays. Large transport and bombing biplanes often needed still more bays to provide sufficient strength. These are often referred to as multi-bay biplanes . A small number of biplanes, such as the Zeppelin-Lindau D.I have no interplane struts and are referred to as being strutless . Because most biplanes do not have cantilever structures, they require rigging wires to maintain their rigidity. Early aircraft used simple wire (either braided or plain), however during
171-412: A biplane aircraft, two wings are placed one above the other. Each provides part of the lift, although they are not able to produce twice as much lift as a single wing of similar size and shape because the upper and the lower are working on nearly the same portion of the atmosphere and thus interfere with each other's behaviour. In a biplane configuration with no stagger from the upper wing to the lower wing,
228-512: A biplane wing arrangement, as did many aircraft in the early years of aviation . While a biplane wing structure has a structural advantage over a monoplane , it produces more drag than a monoplane wing. Improved structural techniques, better materials and higher speeds made the biplane configuration obsolete for most purposes by the late 1930s. Biplanes offer several advantages over conventional cantilever monoplane designs: they permit lighter wing structures, low wing loading and smaller span for
285-867: A cruise speed about 215 knots (247 mph; 398 km/h), at an altitude of 10,000 feet (3,000 m; 1.9 mi), the unpressurized 360 was not the fastest turboprop in its market, but it offered acceptable performance at a reasonable price, combined with ease of service and maintainability. The PT6A turboprops are fully ICAO Stage 3 noise-compliant, making the 360 one of the quietest turboprop aircraft operating today. In 1998, approximately 110 360s were in service. In 2017 there were 42 Short 360 in service: 17 with Air Cargo Carriers , 6 with TransAir , 4 with Skyway Enterprises , 3 with Air Flamenco , 2 with Benair, Deraya Air Taxi and Freedom Air (Guam) , 1 with Ayit Aviation , Comeravia, Gryphon Airlines , International Trans Air Business, Malu Aviation and Nightexpress . The Short 360 specifically proved very popular with
342-624: A documented jet-kill, as one Lockheed F-94 Starfire was lost while slowing down to 161 km/h (100 mph) – below its stall speed – during an intercept in order to engage the low flying Po-2. Later biplane trainers included the de Havilland Tiger Moth in the Royal Air Force (RAF), Royal Canadian Air Force (RCAF) and others and the Stampe SV.4 , which saw service postwar in the French and Belgian Air Forces. The Stearman PT-13
399-513: A faster and more comfortable successor to the Dragon. As the available engine power and speed increased, the drag penalty of external bracing increasingly limited aircraft performance. To fly faster, it would be necessary to reduce external bracing to create an aerodynamically clean design; however, early cantilever designs were either too weak or too heavy. The 1917 Junkers J.I sesquiplane utilized corrugated aluminum for all flying surfaces, with
456-422: A given wing area. However, interference between the airflow over each wing increases drag substantially, and biplanes generally need extensive bracing, which causes additional drag. Biplanes are distinguished from tandem wing arrangements, where the wings are placed forward and aft, instead of above and below. The term is also occasionally used in biology , to describe the wings of some flying animals . In
513-507: A minimum of struts; however, it was relatively easy to damage the thin metal skin and required careful handling by ground crews. The 1918 Zeppelin-Lindau D.I fighter was an all-metal stressed-skin monocoque fully cantilevered biplane, but its arrival had come too late to see combat use in the conflict. By the 1930s, biplanes had reached their performance limits, and monoplanes become increasingly predominant, particularly in continental Europe where monoplanes had been increasingly common from
570-542: A single pilot with three passengers aboard crashed shortly after take-off from Lindbergh Field when an engine failed and the pilot was unable to control the aircraft. One passenger survived the accident with serious injuries, according to the NTSB report, LAX68A0065. Imperial acquired a Beechcraft Queen Air 65-B80, carrying passengers between the Imperial Valley and San Diego in daily, frequent service. Up to eleven passengers could be accommodated in modest seating that included
627-463: A small degree, but more often was used to improve access to the cockpit. Many biplanes have staggered wings. Common examples include the de Havilland Tiger Moth , Bücker Bü 131 Jungmann and Travel Air 2000 . Alternatively, the lower wing can instead be moved ahead of the upper wing, giving negative stagger, and similar benefits. This is usually done in a given design for structural reasons, or to improve visibility. Examples of negative stagger include
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#1732784041444684-473: A somewhat unusual sesquiplane arrangement, possessing a more substantial lower wing with two spars that eliminated the flutter problems encountered by single-spar sesquiplanes. The stacking of wing planes was suggested by Sir George Cayley in 1843. Hiram Maxim adopted the idea for his steam-powered test rig, which lifted off but was held down by safety rails, in 1894. Otto Lilienthal designed and flew two different biplane hang gliders in 1895, though he
741-560: Is better known for his monoplanes. By 1896 a group of young men in the United States, led by Octave Chanute , were flying hang gliders including biplanes and concluded that the externally braced biplane offered better prospects for powered flight than the monoplane. In 1903, the Wright Flyer biplane became the first successful powered aeroplane. Throughout the pioneer years, both biplanes and monoplanes were common, but by
798-536: The Bristol M.1 , that caused even those with relatively high performance attributes to be overlooked in favour of 'orthodox' biplanes, and there was an allegedly widespread belief held at that time that monoplane aircraft were inherently unsafe during combat. Between the years of 1914 and 1925, a clear majority of new aircraft introduced were biplanes; however, during the latter years of the First World War,
855-653: The First World War -era Fokker D.VII fighter and the Second World War de Havilland Tiger Moth basic trainer. The larger two-seat Curtiss JN-4 Jenny is a two bay biplane , the extra bay being necessary as overlong bays are prone to flexing and can fail. The SPAD S.XIII fighter, while appearing to be a two bay biplane, has only one bay, but has the midpoints of the rigging braced with additional struts; however, these are not structurally contiguous from top to bottom wing. The Sopwith 1½ Strutter has
912-703: The Grumman Ag Cat are available in upgraded versions with turboprop engines. The two most produced biplane designs were the 1913 British Avro 504 of which 11,303 were built, and the 1928 Soviet Polikarpov Po-2 of which over 20,000 were built, with the Po-2 being the direct replacement for the Soviet copy of the Avro 504. Both were widely used as trainers. The Antonov An-2 was very successful too, with more than 18,000 built. Although most ultralights are monoplanes,
969-617: The Lite Flyer Biplane, the Sherwood Ranger , and the Murphy Renegade . The feathered dinosaur Microraptor gui glided, and perhaps even flew, on four wings, which may have been configured in a staggered sesquiplane arrangement. This was made possible by the presence of flight feathers on both forelimbs and hindlimbs, with the feathers on the forelimbs opening to a greater span. It has been suggested that
1026-556: The Nieuport-Delage NiD 42 / 52 / 62 series, Fokker C.Vd & e, and Potez 25 , all serving across a large number of air forces. In the general aviation sector, aircraft such as the Waco Custom Cabin series proved to be relatively popular. The Saro Windhover was a sesquiplane with the upper wing smaller than the lower, which was a much rarer configuration than the reverse. The Pfalz D.III also featured
1083-814: The Short 330 . During the 1970s, the world's commuter airline market began to evolve from the 20-seat class to larger and more comfortable cabins. Short Brothers of Northern Ireland had created the Skyvan in 1962, followed by the related but larger Short 330 in 1974. The Short 360 development was announced in 1980, with the prototype's first flight on 1 June 1981 and type certification awarded on 3 September 1981. The first production Short 360 had its maiden flight on 19 August 1982 and entered service with Suburban Airlines (later merged with Allegheny Airlines / US Airways ) in November 1982. After initiating production with
1140-501: The Sopwith Dolphin , Breguet 14 and Beechcraft Staggerwing . However, positive (forward) stagger is much more common. The space enclosed by a set of interplane struts is called a bay (much as the architectural form is used), hence a biplane or triplane with one set of such struts connecting the wings on each side of the aircraft is a single-bay biplane . This provided sufficient strength for smaller aircraft such as
1197-419: The lift coefficient is reduced by 10 to 15 percent compared to that of a monoplane using the same airfoil and aspect ratio . The lower wing is usually attached to the fuselage , while the upper wing is raised above the fuselage with an arrangement of cabane struts , although other arrangements have been used. Either or both of the main wings can support ailerons , while flaps are more usually positioned on
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#17327840414441254-523: The 360 ceased in 1991 after 165 deliveries. The Short 360 is a 36-seat derivative of the 30–33 seat Short 330 . In high density configuration, 39 passengers could be carried. The two Short airliners have a high degree of commonality and are very close in overall dimensions. The later 360 is easily identified by a larger, swept tail unit mounted on a revised rear fuselage. The 360 has a 3-foot (91 cm) fuselage "plug" which gave sufficient additional length for two more seat rows (six more passengers), while
1311-514: The CR.42 was able to achieve success in the defensive night fighter role against RAF bombers that were striking industrial targets throughout northern Italy. The British Fleet Air Arm operated the Fairey Swordfish torpedo bomber from its aircraft carriers, and used the type in the anti-submarine warfare role until the end of the conflict, largely due to their ability to operate from
1368-528: The Caribou , performed the first non-stop flight between the Canadian mainland and Britain in 30 hours 55 minutes, although the intended target for this long distance flight had originally been Baghdad , Iraq . Despite its relative success, British production of the Dragon was quickly ended when in favour of the more powerful and elegant de Havilland Dragon Rapide , which had been specifically designed to be
1425-515: The First World War, the British Royal Aircraft Factory developed airfoil section wire named RAFwire in an effort to both increase the strength and reduce the drag. Four types of wires are used in the biplane wing structure. Drag wires inside the wings prevent the wings from being folded back against the fuselage, running inside a wing bay from the forward inboard corner to the rear outboard corner. Anti-drag wires prevent
1482-577: The French Nieuport 17 and German Albatros D.III , offered lower drag than a conventional biplane while being stronger than a monoplane. During the Interwar period , numerous biplane airliners were introduced. The British de Havilland Dragon was a particularly successful aircraft, using straightforward design to could carry six passengers on busy routes, such as London-Paris services. During early August 1934, one such aircraft, named Trail of
1539-661: The Germans had been experimenting with a new generation of monoplanes, such as the Fokker D.VIII , that might have ended the biplane's advantages earlier had the conflict not ended when it had. The French were also introducing the Morane-Saulnier AI , a strut-braced parasol monoplane , although the type was quickly relegated to the advanced trainer role following the resolution of structural issues. Sesquiplane types, which were biplanes with abbreviated lower wings such as
1596-647: The Imperial - San Diego city pair no longer exists. For several years circa 2015 SeaPort Airlines utilized the single engine turboprop Cessna Caravan 208 configured with nine seats and provided infrequent service. SeaPort left the market after a short period of operation. According to the airline's system timetable, Imperial was serving the following destinations in Arizona and California in September 1979: Imperial flew between LAX and El Centro in 1967/1978 plus I
1653-498: The basic model, Short marketed a number of 360 developments. First was the 360 Advanced , in late 1985, with 1,424 shp (1,062 kW) PT6A-65-AR engines. That was followed by the 360/300 , in March 1987, with six-blade propellers, more powerful PT6A-67R engines, and aerodynamic improvements, giving a higher cruise speed and improved "hot and high" performance. The 360/300 was also built in 360/300F freighter configuration. Production of
1710-407: The biplane naturally has a deep structure and is therefore easier to make both light and strong. Rigging wires on non-cantilevered monoplanes are at a much sharper angle, thus providing less tension to ensure stiffness of the outer wing. On a biplane, since the angles are closer to the ideal of being in direct line with the forces being opposed, the overall structure can then be made stiffer. Because of
1767-562: The co-pilot seat, as the airline operated with a single-pilot only, at that time permitted by the FARs. In a brief alliance with Borrego Springs, CA based Sun Aire Lines in the mid-1970s a Swearingen Metroliner "Metro II" turboprop was placed on the route. The arrangement proved problematic and the two lines went their separate ways, with the high-time Queen Air pressed back into service between Imperial and San Diego. By 1976 there were five or six round trips flown Monday through Friday, none on
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1824-608: The competition aerobatics role and format for such a biplane well-defined by the mid-1930s by the Udet U 12 Flamingo and Waco Taperwing . The Pitts Special dominated aerobatics for many years after World War II and is still in production. The vast majority of biplane designs have been fitted with reciprocating engines . Exceptions include the Antonov An-3 and WSK-Mielec M-15 Belphegor , fitted with turboprop and turbofan engines respectively. Some older biplane designs, such as
1881-470: The drag from the number of struts used. The structural forces acting on the spars of a biplane wing tend to be lower as they are divided between four spars rather than two, so the wing can use less material to obtain the same overall strength and is therefore lighter. A given area of wing also tends to be shorter, reducing bending moments on the spars, which then allow them to be more lightly built as well. The biplane does however need extra struts to maintain
1938-549: The end of World War I . At the start of World War II , several air forces still had biplane combat aircraft in front line service but they were no longer competitive, and most were used in niche roles, such as training or shipboard operation, until shortly after the end of the war. The British Gloster Gladiator biplane, the Italian Fiat CR.42 Falco and Soviet I-153 sesquiplane fighters were all still operational after 1939. According to aviation author Gianni Cattaneo,
1995-528: The extra length smoothed out the aerodynamic profile and reduced drag . Seating is arranged with two seats on the starboard side of the cabin and one seat on the port side. The 360's power is supplied by two Pratt & Whitney PT6A-65Rs. Building on the strengths and reputation of its 330 antecedent, the 360s found a niche in regional airline use worldwide, being able to operate comfortably from 4,500 ft (1,400 m) runways – opening up hundreds of airfields that would otherwise be inaccessible to airliners. With
2052-416: The gap between the wings, which add both weight and drag. The low power supplied by the engines available in the first years of aviation limited aeroplanes to fairly low speeds. This required an even lower stalling speed, which in turn required a low wing loading , combining both large wing area with light weight. Obtaining a large enough wing area without the wings being long, and thus dangerously flexible
2109-406: The hind limbs could not have opened out sideways but in flight would have hung below and slightly behind the fore limbs. Short 360 The Short 360 (also SD3-60 ; also Shorts 360 ) is a commuter aircraft that was built by UK manufacturer Short Brothers during the 1980s. The Short 360 seats up to 39 passengers and was introduced into service in November 1982. It is a larger version of
2166-639: The low speeds and simple construction involved have inspired a small number of biplane ultralights, such as Larry Mauro's Easy Riser (1975–). Mauro also made a version powered with solar cells driving an electric motor called the Solar Riser . Mauro's Easy Riser was used by "Father Goose", Bill Lishman . Other biplane ultralights include the Belgian-designed Aviasud Mistral , the German FK12 Comet (1997–),
2223-519: The lower wing. Bracing is nearly always added between the upper and lower wings, in the form of interplane struts positioned symmetrically on either side of the fuselage and bracing wires to keep the structure from flexing, where the wings are not themselves cantilever structures. The primary advantage of the biplane over a monoplane is its ability to combine greater stiffness with lower weight. Stiffness requires structural depth and where early monoplanes had to have this provided with external bracing,
2280-519: The mid 1980s, the airline had retired the Metroliner and Cessna aircraft and had standardized its fleet with Bandeirante and Short 360 turboprops. The Short 360 was the largest aircraft ever operated by Imperial. Biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer , used
2337-573: The most famed copies was the Siemens-Schuckert D.I . The Albatros D.III and D.V , which had also copied the general layout from Nieuport, similarly provided the backbone of the German forces during the First World War. The Albatros sesquiplanes were widely acclaimed by their aircrews for their maneuverability and high rate of climb. During interwar period , the sesquiplane configuration continued to be popular, with numerous types such as
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2394-609: The night ground attack role throughout the Second World War. In the case of the Po-2, production of the aircraft continued even after the end of the conflict, not ending until around 1952. A significant number of Po-2s were fielded by the Korean People's Air Force during the Korean War , inflicting serious damage during night raids on United Nations bases. The Po-2 is also the only biplane to be credited with
2451-486: The outbreak of the First World War biplanes had gained favour after several monoplane structural failures resulted in the RFC's "Monoplane Ban" when all monoplanes in military service were grounded, while the French also withdrew most monoplanes from combat roles and relegated them to training. Figures such as aviation author Bruce observed that there was an apparent prejudice held even against newly-designed monoplanes, such as
2508-424: The reduced stiffness, wire braced monoplanes often had multiple sets of flying and landing wires where a biplane could easily be built with one bay, with one set of landing and flying wires. The extra drag from the wires was not enough to offset the aerodynamic disadvantages from having two airfoils interfering with each other however. Strut braced monoplanes were tried but none of them were successful, not least due to
2565-657: The relatively compact decks of escort carriers . Its low stall speed and inherently tough design made it ideal for operations even in the often severe mid-Atlantic weather conditions. By the end of the conflict, the Swordfish held the distinction of having caused the destruction of a greater tonnage of Axis shipping than any other Allied aircraft. Both the German Heinkel He 50 and the Soviet Polikarpov Po-2 were used with relative success in
2622-728: The series of Nieuport military aircraft—from the Nieuport 10 through to the Nieuport 27 which formed the backbone of the Allied air forces between 1915 and 1917. The performance of the Nieuport sesquiplanes was so impressive that the Idflieg (the German Inspectorate of flying troops) requested their aircraft manufacturers to produce copies, an effort which was aided by several captured aircraft and detailed drawings; one of
2679-517: The southern California coastal corridor in addition to Swearingen Metroliner turboprops and smaller Cessna prop aircraft. For most of the early 1980s, the airline operated flights between San Diego International Airport and Los Angeles International Airport at thirty minutes intervals throughout the day. By 1986 the airline was suffering the effects of increased competition and it ceased operations in January of that year. Nonstop service between
2736-415: The structural problems associated with monoplanes, but offered little improvement for biplanes. The default design for a biplane has the wings positioned directly one above the other. Moving the upper wing forward relative to the lower one is called positive stagger or, more often, simply stagger. It can increase lift and reduce drag by reducing the aerodynamic interference effects between the two wings by
2793-670: The two planes when the high pressure air under the top wing and the low pressure air above the lower wing cancel each other out. This means that a biplane does not in practice obtain twice the lift of the similarly-sized monoplane. The farther apart the wings are spaced the less the interference, but the spacing struts must be longer, and the gap must be extremely large to reduce it appreciably. As engine power and speeds rose late in World War I , thick cantilever wings with inherently lower drag and higher wing loading became practical, which in turn made monoplanes more attractive as it helped solve
2850-400: The upper and lower wings together. The sesquiplane is a type of biplane where one wing (usually the lower) is significantly smaller than the other. The word, from Latin, means "one-and-a-half wings". The arrangement can reduce drag and weight while retaining the biplane's structural advantages. The lower wing may have a significantly shorter span, or a reduced chord . Examples include
2907-460: The weekends, the first departing Imperial at 6 a.m. on the 36-minute flight, with service ending each night just before 8 p.m. back in the "Valley." In mid-1978 discussions resulted in the airline being sold by James K Vedder to a group of investors from the San Diego area who believed that the deregulated airline environment would provide opportunities not before possible. Soon the lone Queen Air
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#17327840414442964-434: The wings from folding up, and run from the underside of the outer wing to the lower wing root. Conversely, landing wires prevent the wings from sagging, and resist the forces when an aircraft is landing, and run from the upper wing centre section to outboard on the lower wings. Additional drag and anti-drag wires may be used to brace the cabane struts which connect the fuselage to the wings, and interplane struts, which connect
3021-421: The wings from moving forward when the aircraft stops and run the opposite direction to the drag wires. Both of these are usually hidden within the wings, and if the structure is sufficiently stiff otherwise, may be omitted in some designs. Indeed many early aircraft relied on the fabric covering of the wing to provide this rigidity, until higher speeds and forces made this inadequate. Externally, lift wires prevent
3078-404: Was more readily accomplished with a biplane. The smaller biplane wing allows greater maneuverability . Following World War I, this helped extend the era of the biplane and, despite the performance disadvantages, most fighter aircraft were biplanes as late as the mid-1930s. Specialist sports aerobatic biplanes are still made in small numbers. Biplanes suffer aerodynamic interference between
3135-488: Was retired, replaced by four twin engine Cessna 402 prop aircraft and a single twin engine Cessna 404 . The route system immediately expanded to Yuma and Phoenix as well as Los Angeles International. About 1980 the airline moved its headquarters to McClellan-Palomar Airport in Carlsbad, California . Later the airline acquired the larger Embraer EMB-110 Bandeirante and Short 360 turboprop aircraft for its routes along
3192-573: Was the travel manager at Mattel and our execs flew to our plant in Mexico via Imperial Airways. According to the airline's route map, Imperial was serving the following destinations in California in September 1984: Imperial was operating a mix of Swearingen Metroliner and Embraer EMB-110 Bandeirante turboprops as well as smaller Cessna 402 and Cessna 404 prop aircraft during the early 1980s and had earlier operated Beech 18 prop aircraft. By
3249-777: Was widely used by the United States Army Air Force (USAAF) while the US Navy operated the Naval Aircraft Factory N3N . In later civilian use in the US, the Stearman became particularly associated with stunt flying such as wing-walking , and with crop dusting, where its compactness worked well at low levels, where it had to dodge obstacles. Modern biplane designs still exist in specialist roles such as aerobatics and agricultural aircraft with
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