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63-440: The Airacuda was Bell Aircraft's answer for a " bomber destroyer " aircraft. Although it did see limited production, and one fully operational squadron was eventually formed, only one prototype and 12 production models were ultimately built, in three slightly different versions. In an effort to break into the aviation business, Bell Aircraft created a unique fighter concept touted to be "a mobile anti-aircraft platform" as well as

126-532: A chase plane for safety. Eventually the decision was made to disperse the aircraft to various airfields to give pilots an opportunity to add the unusual aircraft to their log books. Airacudas were sent at various times to Langley Field , Virginia; Maxwell Field , Alabama; Hamilton Field, California ; and Wright Field , in Dayton, Ohio. YFM-1 38-488 was displayed at the 1940 World's Fair in New York, finished in

189-637: A "convoy fighter". Created to intercept enemy bombers at distances beyond the range of single-seat fighter interceptors, the YFM-1 ( Y , service test; F , fighter; M , multiplace) was an innovative design incorporating many features never before seen in a military aircraft, as well as several never seen again. Using a streamlined, "futuristic" design, the Bell Airacuda appeared to be "unlike any other fighters up to that time". According to Major Alexander De Seversky 's 1942 book Victory Through Air Power ,

252-512: A broken oil line started a fire. The cause of the broken line appeared to be serious airframe vibration encountered during the flight. With no way of extinguishing the fire, both the pilot and crew chief agreed to bail out. The pilot was killed when his parachute failed to deploy (he may have struck the tail while bailing out). This was the only fatality to occur during the flying of Airacudas. The accident investigation report stated "inherent defects in design caused constant maintenance difficulties and

315-400: A common shaft. The first prototype was finished in 1915 with the aim of overcoming the power loss experienced by aircraft engines due to the decreased density of air at high altitudes. However, the prototype was not reliable and did not reach production. Another early patent for turbochargers was applied for in 1916 by French steam turbine inventor Auguste Rateau , for their intended use on

378-425: A design by Scottish engineer Dugald Clerk . Then in 1885, Gottlieb Daimler patented the technique of using a gear-driven pump to force air into an internal combustion engine. The 1905 patent by Alfred Büchi , a Swiss engineer working at Sulzer is often considered the birth of the turbocharger. This patent was for a compound radial engine with an exhaust-driven axial flow turbine and compressor mounted on

441-455: A gyro-stabilised and an optical sight to aim the weapons; and a radio operator/gunner armed with a pair of machine guns stationed at mid-fuselage waist blisters for defense against attack from the rear. An unusual feature of the Airacuda was the main door for entry. The door was opened and pulled down and hinges folded in on three steps for the crew to climb into the aircraft. The Airacuda

504-412: A later book Destiny: A Flying Tiger's Rendezvous With Fate as Flying the Bell Airacuda was a new experience for me, since it was the first pusher aircraft I'd ever flown. Its handling characteristics were foreign to anything I had ever had my hands on. Under power it was unstable in pitch, but stable with power off. While flying straight and level, if a correction in pitch was required, a forward push on

567-405: A limiting factor in the peak power produced by the engine. Various technologies, as described in the following sections, are often aimed at combining the benefits of both small turbines and large turbines. Large diesel engines often use a single-stage axial inflow turbine instead of a radial turbine. A twin-scroll turbocharger uses two separate exhaust gas inlets, to make use of the pulses in

630-467: A loss of interest in building bomber destroyers as a specific class of aircraft. Even small fighters were able to carry enough firepower to deal effectively with enemy bombers, and high-performance all-purpose late-war fighters—the P-51 Mustang being the prime example—excelled at all fighter roles: pursuit, bomber escort, interception, and ground attack. The interest in interceptors was renewed during

693-574: A pioneering role with turbocharging engines as witnessed by Sulzer, Saurer and Brown, Boveri & Cie . Automobile manufacturers began research into turbocharged engines during the 1950s, however the problems of "turbo lag" and the bulky size of the turbocharger were not able to be solved at the time. The first turbocharged cars were the short-lived Chevrolet Corvair Monza and the Oldsmobile Jetfire , both introduced in 1962. Greater adoption of turbocharging in passenger cars began in

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756-401: A stop before bailing out. Because of the tandem seating, it was necessary for Sparks to exit the aircraft first, and in doing so he struck the empennage, breaking his legs – and in the process, freeing the rudder. Strickler decided to stay with the aircraft and attempt an emergency landing. By this time, the aircraft had lost sufficient altitude that there was not time to restart

819-430: A tendency to fill the gun nacelles with smoke whenever fired and, additionally, fears persisted as to how the gunners would escape in an emergency, with the propellers directly behind them. An emergency bailout would have required both propellers to be feathered , though additional provision was made with the use of explosive bolts on the propellers to jettison them in the event of a bailout. As with other types armed with

882-813: A training facility at Chanute Field , Illinois, where the aircraft were assigned to the 10th Air Base Squadron to be used for ground crew instruction. By March 1942, all Airacudas had been scrapped. Data from General characteristics Performance Armament Aircraft of comparable role, configuration, and era Related lists Bomber destroyer Bomber destroyers were World War II interceptor aircraft intended to destroy enemy bomber aircraft . Bomber destroyers were typically larger and heavier than general interceptors, designed to mount more powerful armament, and often having twin engines. They differed from night fighters largely in that they were designed for day use. The United States Army Air Corps considered powerfully armed destroyers, like

945-412: Is done with the use of adjustable vanes located inside the turbine housing between the inlet and turbine, which affect flow of gases towards the turbine. Some variable-geometry turbochargers use a rotary electric actuator to open and close the vanes, while others use a pneumatic actuator . If the turbine's aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio

1008-474: Is increasing. The companies which manufacture the most turbochargers in Europe and the U.S. are Garrett Motion (formerly Honeywell), BorgWarner and Mitsubishi Turbocharger . Turbocharger failures and resultant high exhaust temperatures are among the causes of car fires. Failure of the seals will cause oil to leak into the cylinders causing blue-gray smoke. In diesel engines, this can cause an overspeed,

1071-515: Is powered by the kinetic energy of the exhaust gases, whereas a supercharger is mechanically powered (usually by a belt from the engine's crankshaft). However, up until the mid-20th century, a turbocharger was called a "turbosupercharger" and was considered a type of supercharger. Prior to the invention of the turbocharger, forced induction was only possible using mechanically-powered superchargers . Use of superchargers began in 1878, when several supercharged two-stroke gas engines were built using

1134-402: Is that the optimum aspect ratio at low engine speeds is very different from that at high engine speeds. An electrically-assisted turbocharger combines a traditional exhaust-powered turbine with an electric motor, in order to reduce turbo lag. This differs from an electric supercharger , which solely uses an electric motor to power the compressor. The compressor draws in outside air through

1197-411: Is that the two nozzles are different sizes: the smaller nozzle is installed at a steeper angle and is used for low-rpm response, while the larger nozzle is less angled and optimised for times when high outputs are required. Variable-geometry turbochargers (also known as variable-nozzle turbochargers ) are used to alter the effective aspect ratio of the turbocharger as operating conditions change. This

1260-490: Is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, variable-geometry turbochargers often have reduced lag, a lower boost threshold, and greater efficiency at higher engine speeds. The benefit of variable-geometry turbochargers

1323-441: Is unable to produce significant boost. At low rpm, the exhaust gas flow rate is unable to spin the turbine sufficiently. The boost threshold causes delays in the power delivery at low rpm (since the unboosted engine must accelerate the vehicle to increase the rpm above the boost threshold), while turbo lag causes delay in the power delivery at higher rpm. Some engines use multiple turbochargers, usually to reduce turbo lag, increase

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1386-528: The Bell YFM-1 Airacuda prototype, to counter a potential attack of high-performance bombers. The Lockheed P-38 Lightning and Bell P-39 Airacobra were also initially specified to carry very heavy armament based on a central 37 mm cannon, specified as interceptor aircraft working in the anti-bomber role. In the pre-war era the UK, by contrast, favored development of the "turret fighter", such as

1449-739: The Boeing B-17 Flying Fortress in 1938, which used turbochargers produced by General Electric. Other early turbocharged airplanes included the Consolidated B-24 Liberator , Lockheed P-38 Lightning , Republic P-47 Thunderbolt and experimental variants of the Focke-Wulf Fw 190 . The first practical application for trucks was realized by Swiss truck manufacturing company Saurer in the 1930s. BXD and BZD engines were manufactured with optional turbocharging from 1931 onwards. The Swiss industry played

1512-485: The Boulton Paul Defiant , which mounted the armament in a rotating turret. Turret fighters were expected to work together to coordinate fire on unescorted bombers (due to limits of German fighter range), able to attack from all quarters, and not be limited by the brief firing opportunity of a single seat fighter in a high speed attack. The P-38, a small, single-crewed example of the bomber destroyer type,

1575-733: The Cold War ; both the United States and the Soviet Union designed and produced dedicated "pure" interceptors such as the Convair F-106 Delta Dart and the Mikoyan-Gurevich MiG-25 . These aircraft were generally never referred to as "bomber destroyers", even though their primary mission was the destruction of enemy strategic bombers. Few dedicated interceptors have been designed or produced since

1638-413: The crankshaft ) whereas a turbocharger is powered by the kinetic energy of the engine's exhaust gas . A turbocharger does not place a direct mechanical load on the engine, although turbochargers place exhaust back pressure on engines, increasing pumping losses. Supercharged engines are common in applications where throttle response is a key concern, and supercharged engines are less likely to heat soak

1701-412: The 1960s. Turbocharger In an internal combustion engine , a turbocharger (also known as a turbo or a turbosupercharger ) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the engine in order to produce more power for a given displacement . The current categorisation is that a turbocharger

1764-414: The 1980s, as a way to increase the performance of smaller displacement engines. Like other forced induction devices, a compressor in the turbocharger pressurises the intake air before it enters the inlet manifold . In the case of a turbocharger, the compressor is powered by the kinetic energy of the engine's exhaust gases, which is extracted by the turbocharger's turbine . The main components of

1827-403: The 37 mm M4, the low muzzle velocity of the weapon made it difficult to use as an aerial weapon, limiting the useful range. The Allison V-1710 -41 engines, though relatively trouble-free in other types, had insufficient cooling. Like many pusher designs, they were prone to overheating while on the ground, since there was no propwash blowing over the engines to cool them. On the ground,

1890-478: The Air Corps when pilot John Strickler, a Bell pilot and engineer/co-pilot Brian Sparks, Bell's chief test pilot, encountered problems recovering from a deliberate spin attempt which was part of the test flight profile. Despite every effort to emerge from the spin, the aircraft would not respond, and it appeared that the rudder had locked. Co-pilot Sparks shut down the engines and waited for the propellers to come to

1953-533: The Airacuda was intended, the aircraft were stricken from inventory. The prototype, known as the XFM-1 , incorporated a tailwheel, side "blister" ports, and a smooth, rounded canopy. This is the best known, and most produced version. An updated version called the YFM-1A eliminated the side blisters and added externally mounted radiators and turbo-superchargers . Produced in 1940, the final version designated YFM-1B ,

Bell YFM-1 Airacuda - Misplaced Pages Continue

2016-427: The Bell Airacuda "represents a great engineering achievement. But its designation as 'convoy fighter' is erroneous, since that requires different disposition of armament. With its maximum firepower directed forward, it really offers a preview of an effective long-range interceptor fighter ." A forward-firing 37 mm (1.46 in) M4 cannon with an accompanying gunner was mounted in a forward compartment of each of

2079-543: The Renault engines used by French fighter planes. Separately, testing in 1917 by the National Advisory Committee for Aeronautics (NACA) and Sanford Alexander Moss showed that a turbocharger could enable an engine to avoid any power loss (compared with the power produced at sea level) at an altitude of up to 4,250 m (13,944 ft) above sea level. The testing was conducted at Pikes Peak in

2142-708: The United States using the Liberty L-12 aircraft engine. The first commercial application of a turbocharger was in June 1924 when the first heavy duty turbocharger, model VT402, was delivered from the Baden works of Brown, Boveri & Cie , under the supervision of Alfred Büchi, to SLM, Swiss Locomotive and Machine Works in Winterthur. This was followed very closely in 1925, when Alfred Büchi successfully installed turbochargers on ten-cylinder diesel engines, increasing

2205-523: The YFM-1 airframes were changed on the production line to accept the V-1710-41 without turbo-supercharging, becoming YFM-1Bs. This is noted in a contract change dated 19 October 1939, which shows that aircraft 38-489 and 38-490 had their turbos, all associated ducting, and controls removed and V-1710-41(D2A) "altitude rated" engines installed instead. The (D2A) was essentially a -23 with higher supercharger gear ratios (8.77:1 versus 6.23:1), which allowed

2268-461: The aircraft had to be towed to and from the runway and could only be started when the Airacuda was able to take off immediately. Even in the air overheating was not uncommon. Although designed for turbo-supercharging , the first flights were made with V-1710-9 single-stage supercharged engines that only delivered 1,000  hp (750  kW ) each. Despite the 5 ft (1.5 m)-long shaft extensions, there were no problems with this feature. When

2331-471: The aircraft's many faults, only two were lost in accidents (although considering that only 12 were ever built, the statistics are not favorable with many other types, at a 16.6% loss ratio; especially when the actual aircraft saw so little operational service that would even expose it to hazard of accidents). The seventh aircraft (38-492) was on its final test flight from the Buffalo factory prior to delivery to

2394-449: The compressor blades. Ported shroud designs can have greater resistance to compressor surge and can improve the efficiency of the compressor wheel. The center hub rotating assembly (CHRA) houses the shaft that connects the turbine to the compressor. A lighter shaft can help reduce turbo lag. The CHRA also contains a bearing to allow this shaft to rotate at high speeds with minimal friction. Some CHRAs are water-cooled and have pipes for

2457-464: The control resulted in the airplane wanting to pitch over even more. Pitch control became a matter of continually jockeying the controls, however slightly, even when the aircraft was in proper trim. The same applied if pulling back on the control. It would tend to continue pitching up, requiring an immediate corrective response. The same happened in a turn with power off, the Bell became stable in pitch. This

2520-406: The defensive anti-bomber role (leaving it for the light fighters), and envisaged a heavy fighter for offensive missions: escorting the bombers, long-range fighter suppression, and ground attack. The German designs suffered performance deficits as they were weighed down by a two- or three-man crew and extra cockpit accommodations. After World War II, improvements in engine power and armament led to

2583-403: The engine rpm is within the turbocharger's operating range – that occurs between pressing the throttle and the turbocharger spooling up to provide boost pressure. This delay is due to the increasing exhaust gas flow (after the throttle is suddenly opened) taking time to spin up the turbine to speeds where boost is produced. The effect of turbo lag is reduced throttle response , in

Bell YFM-1 Airacuda - Misplaced Pages Continue

2646-559: The engine's coolant to flow through. One reason for water cooling is to protect the turbocharger's lubricating oil from overheating. The simplest type of turbocharger is the free floating turbocharger. This system would be able to achieve maximum boost at maximum engine revs and full throttle, however additional components are needed to produce an engine that is driveable in a range of load and rpm conditions. Additional components that are commonly used in conjunction with turbochargers are: Turbo lag refers to delay – when

2709-418: The engine's intake system, pressurises it, then feeds it into the combustion chambers (via the inlet manifold ). The compressor section of the turbocharger consists of an impeller, a diffuser, and a volute housing. The operating characteristics of a compressor are described by the compressor map . Some turbochargers use a "ported shroud", whereby a ring of holes or circular grooves allows air to bleed around

2772-424: The engines. Strickler put the Airacuda down hard in a farmer's field and walked away unhurt. The Airacuda was so badly damaged that it had to be scrapped. All three Airacudas with tricycle landing gear encountered problems and were damaged at one time or another. The most serious accident occurred to YFM-1A (Model 8) 38-497, on a flight between Chanute Field , Illinois , and Keesler Field , Mississippi , when

2835-410: The flow of exhaust gases to mechanical energy of a rotating shaft (which is used to power the compressor section). The turbine housings direct the gas flow through the turbine section, and the turbine itself can spin at speeds of up to 250,000 rpm. Some turbocharger designs are available with multiple turbine housing options, allowing a housing to be selected to best suit the engine's characteristics and

2898-400: The flow of the exhaust gasses from each cylinder. In a standard (single-scroll) turbocharger, the exhaust gas from all cylinders is combined and enters the turbocharger via a single intake, which causes the gas pulses from each cylinder to interfere with each other. For a twin-scroll turbocharger, the cylinders are split into two groups in order to maximize the pulses. The exhaust manifold keeps

2961-464: The flying of this type has been very limited". Despite these problems, one fully operational Airacuda squadron was eventually assembled, and operated from 1938 until 1940. Funds were appropriated, but never released, for the purchase of two groups of Airacudas. Continuing problems gave the aircraft a reputation as "hangar queens". Near the end of the type's operational life, the aircraft were flown primarily for photo opportunities and always accompanied by

3024-404: The form of a delay in the power delivery. Superchargers do not suffer from turbo lag because the compressor mechanism is driven directly by the engine. Methods to reduce turbo lag include: A similar phenomenon that is often mistaken for turbo lag is the boost threshold . This is where the engine speed (rpm) is currently below the operating range of the turbocharger system, therefore the engine

3087-410: The gases from these two groups of cylinders separated, then they travel through two separate spiral chambers ("scrolls") before entering the turbine housing via two separate nozzles. The scavenging effect of these gas pulses recovers more energy from the exhaust gases, minimizes parasitic back losses and improves responsiveness at low engine speeds. Another common feature of twin-scroll turbochargers

3150-502: The intake air. A combination of an exhaust-driven turbocharger and an engine-driven supercharger can mitigate the weaknesses of both. This technique is called twincharging . Turbochargers have been used in the following applications: In 2017, 27% of vehicles sold in the US were turbocharged. In Europe 67% of all vehicles were turbocharged in 2014. Historically, more than 90% of turbochargers were diesel, however, adoption in petrol engines

3213-480: The markings of the 27th Pursuit Squadron . During this time, the aircraft saw limited flight time, as few pilots were interested in flying the unusual aircraft. Several plans were made to modify the Airacudas to give them operational status, including modifying the airframe and adding more powerful engines, but all proposals were eventually rejected. In early 1942, despite fears of enemy bomber attacks against which

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3276-591: The motor to develop around 1,090 horsepower (810 kW) up to 13,200 ft (4,000 m) ASL. They used the same ratings and components as the altitude-rated V-1710-33(C15) Allison fitted to the original Curtiss XP-40. Allison was paid $ 1,690 to modify each engine. Initial flight testing by Lt. Ben Kelsey proved the Airacuda virtually impossible to control with only one engine, as the aircraft would go into an immediate spin. Problems with stability in pitch were also encountered and had to be corrected by reducing power. Test pilot Erik Shilling described his experiences in

3339-407: The performance requirements. A turbocharger's performance is closely tied to its size, and the relative sizes of the turbine wheel and the compressor wheel. Large turbines typically require higher exhaust gas flow rates, therefore increasing turbo lag and increasing the boost threshold. Small turbines can produce boost quickly and at lower flow rates, since it has lower rotational inertia, but can be

3402-560: The power output from 1,300 to 1,860 kilowatts (1,750 to 2,500 hp). This engine was used by the German Ministry of Transport for two large passenger ships called the Preussen and Hansestadt Danzig . The design was licensed to several manufacturers and turbochargers began to be used in marine, railcar and large stationary applications. Turbochargers were used on several aircraft engines during World War II, beginning with

3465-399: The range of rpm where boost is produced, or simplify the layout of the intake/exhaust system. The most common arrangement is twin turbochargers, however triple-turbo or quad-turbo arrangements have been occasionally used in production cars. The key difference between a turbocharger and a supercharger is that a supercharger is mechanically driven by the engine (often through a belt connected to

3528-455: The single generator. The generator, with its own supercharger, was located in the belly of the aircraft. In the event of a failure (and they occurred frequently), the crew was instructed to begin immediate emergency restart procedures, as the aircraft basically shut down. When the APU failed, the pilot had "NO fuel pressure, NO vacuum, NO hydraulic pressure, NO gear, NO flaps and NO ENGINES". Despite

3591-407: The turbocharger are: The turbine section (also called the "hot side" or "exhaust side" of the turbo) is where the rotational force is produced, in order to power the compressor (via a rotating shaft through the center of a turbo). After the exhaust has spun the turbine it continues into the exhaust piping and out of the vehicle. The turbine uses a series of blades to convert kinetic energy from

3654-572: The turbos were fitted to the later YFM-1, they were plagued by cranky turbo regulators that backfired continuously. An explosion during a September 1939 test flight made it apparent that the teething engine troubles would not be solved easily. Marshall Wainwright notes that other sources indicate the first eight aircraft were to originally have been powered by Allison V-1710-13 engines fitted with GE Type B-6 turbo-superchargers (turbochargers). These aircraft were eventually delivered with improved V-1710-23(D2) engines. Wainwright further states that two of

3717-413: The two engine nacelles . Although capable of aiming the cannons, the gunners' primary purpose was simply to load them with the 110 rounds of ammunition stored in each nacelle. The crew of five included the pilot and gunners; a copilot/navigator who doubled as a fire-control officer, using a Sperry Instruments "Thermionic" fire control system (originally developed for anti-aircraft cannon) combined with

3780-473: Was eventually outfitted with a 20 mm cannon and four .50-caliber machine guns in a central nacelle instead of a heavier cannon; it proved itself a highly competent fighter aircraft in the early phase of World War II. A deceptively similar, although completely different, designation was the German Zerstörer (meaning "destroyer"). Introduced on 1 May 1939, the term did specifically exclude

3843-423: Was fortunate because during approach and landing, it was very stable, and a nice flying airplane. The Airacuda was also saddled with a complex and temperamental electrical system and was the only aircraft ever built to rely on an independent auxiliary power unit (APU) to power both engine fuel pumps, as well as all aircraft electrical systems. Systems usually powered by an aircraft's engines were instead powered by

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3906-465: Was plagued with problems from the start. The lofty performance estimates were unobtainable as, despite its sleek looks, the Airacuda was heavy and was slower than most bombers. In the event of interception by enemy fighters, the Airacuda was not maneuverable enough to dogfight, while the meager 600 lb (270 kg) bombload was of little use in the intended fighter-bomber role. Even the 37 mm cannons were of less value than predicted. The cannons had

3969-465: Was slightly larger, had slightly less powerful Allison engines and incorporated a tricycle landing gear. The canopy was redesigned, with a flat forward windshield. A rearward-facing belly gunner's position was also added. The resulting aircraft was roughly the size of a Douglas B-18 Bolo medium bomber . Three YFM-1Bs were produced in 1939 before production was finally terminated. By 1942, all nine surviving YFM-1 airframes had been flown by ferry crews to

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