96-507: The M133 is a turbocharged inline-four engine produced by Mercedes-Benz . Since its debut in 2013, it has been awarded International Engine of the Year three times in the "Best New Engine" and "1.8-litre to 2-litre" categories. The M133 is based on the M270 engine but has been extensively revised by AMG . It features a twin-scroll turbocharger, BlueDIRECT direct injection , iron-carbon alloy on
192-576: A Consolidated B-24 Liberator , part of the United States Navy 's contribution ("Project Anvil"), en route for Heligoland piloted by Lieutenant Joseph P. Kennedy Jr. (future U.S. president John F. Kennedy 's elder brother) exploded over the Blyth estuary . Blast damage was caused over a radius of 5 miles (8.0 km). Naval flights stopped but a few more missions were flown by the USAAF. The Aphrodite project
288-422: 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 is powered by the kinetic energy of the exhaust gases, whereas a supercharger is mechanically powered (usually by
384-572: A 20% increase in aircraft weight. The B-17's turbocharged Wright R-1820 Cyclone 9 engines were upgraded to increasingly more powerful versions of the same powerplants throughout its production, and similarly, the number of machine gun emplacement locations was increased. The B-17F variant was the primary version used by the Eighth Air Force to face the Germans in 1943, and standardized the manned Sperry ball turret for ventral defense, also replacing
480-399: 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
576-400: 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
672-588: A condition known as diesel engine runaway . Boeing B-17 Flying Fortress The Boeing B-17 Flying Fortress is an American four-engined heavy bomber aircraft developed in the 1930s for the United States Army Air Corps (USAAC). A fast and high-flying bomber, the B-17 was used primarily in the European Theater of Operations and dropped more bombs than any other aircraft during World War II . It
768-425: 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
864-510: A further five squadrons of Spitfire Vs to cover the withdrawal) on the first USAAF heavy bomber raid over Europe, against the large railroad marshalling yards at Rouen -Sotteville in France, while a further six aircraft flew a diversionary raid along the French coast. The operation, carried out in good visibility, was a success, with only minor damage to one aircraft, unrelated to enemy action, and half
960-561: A legal loophole, the Air Corps ordered 13 YB-17s (designated Y1B-17 after November 1936 to denote its special F-1 funding) for service testing. The YB-17 incorporated a number of significant changes from the Model 299, including more powerful Wright R-1820 -39 Cyclone engines. Although the prototype was company-owned and never received a military serial (the B-17 designation itself did not appear officially until January 1936, nearly three months after
1056-405: 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
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#17328633327221152-478: A number of B-17Gs were also converted for search-and-rescue duties, later to be redesignated B-17H. Late in World War ;II, at least 25 B-17s were fitted with radio controls and television cameras, loaded with 20,000 lb (9,100 kg) of high explosives and designated BQ-7 "Aphrodite missiles" for Operation Aphrodite against bombing-resistant German bunkers. The operation, which involved remotely flying
1248-566: 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
1344-650: A sufficient supply of modern heavy bombers, with the largest available long-range medium bombers in any numbers being the Vickers Wellington , which could carry 4,500 pounds (2,000 kg) of bombs. While the Short Stirling and Handley Page Halifax became its primary bombers by 1941, in early 1940, the RAF agreed with the U.S. Army Air Corps to acquire 20 B-17Cs, which were given the service name Fortress Mk.I. Their first operation, against Wilhelmshaven on 8 July 1941
1440-518: A test flight determining the rate of climb and service ceiling was planned. The command pilot was Major Ployer Peter Hill , Wright Field Material Division Chief of the Flying Branch, his first flight in the Model 299. Copilot was Lieutenant Donald Putt, while Boeing chief test pilot Leslie R. Tower was behind the pilots in an advisory role. Also on board were Wright Field test observer John Cutting and mechanic Mark Koegler. The plane stalled and spun into
1536-584: A top speed of at least 200 mph (320 km/h). They also desired, but did not require, a bomber with a range of 2,000 mi (3,200 km) and a speed of 250 mph (220 kn; 400 km/h). The competition for the air corps contract was to be decided by a "fly-off" between Boeing's design, the Douglas DB-1 , and the Martin Model 146 at Wilbur Wright Field in Dayton, Ohio . The prototype B-17, with
1632-464: A well-framed, 10 panel plexiglass nose, the B-17Bs were delivered in five small batches between July 1939 and March 1940. In July 1940, an order for 512 B-17s was issued, but at the time of the attack on Pearl Harbor , fewer than 200 were in service with the army. A total of 155 B-17s of all variants were delivered between 11 January 1937 and 30 November 1941, but production quickly accelerated, with
1728-412: 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
1824-470: 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,
1920-402: 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
2016-411: 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
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#17328633327222112-510: Is the third-most produced bomber of all time, behind the American four-engined Consolidated B-24 Liberator and the German multirole, twin-engined Junkers Ju 88 . The B-17 was also employed in transport, anti-submarine warfare, and search and rescue roles. In a USAAC competition, Boeing's prototype Model 299/XB-17 outperformed two other entries but crashed, losing the initial 200-bomber contract to
2208-490: 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
2304-441: 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
2400-710: 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
2496-591: The Douglas B-18 Bolo . Still, the Air Corps ordered 13 more B-17s for further evaluation, which were introduced into service in 1938. The B-17 evolved through numerous design advances but from its inception, the USAAC (from 1941 the United States Army Air Forces , USAAF) promoted the aircraft as a strategic weapon. It was a relatively fast, high-flying, long-range bomber with heavy defensive armament at
2592-453: The Japanese battleship Haruna , which was later acknowledged as a near bomb miss on the heavy cruiser Ashigara . Nonetheless, this deed made him a celebrated war hero . Kelly's B-17C AAF S/N 40-2045 (19th BG / 30th BS) crashed about 6 mi (10 km) from Clark Field after he held the burning Fortress steady long enough for the surviving crew to bail out. Kelly was posthumously awarded
2688-413: 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
2784-414: 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
2880-404: The 8th, had ordered the second Schweinfurt mission to be cancelled as the weather deteriorated, but the lead units had already entered hostile air space and continued with the mission. Most of the escorts turned back or missed the rendezvous, and as a result, 60 B-17s were destroyed. A third raid on Schweinfurt on 24 February 1944 highlighted what came to be known as " Big Week ", during which
2976-771: The American and British bomber commands were organized at the Casablanca Conference in January 1943. The resulting " Combined Bomber Offensive " weakened the Wehrmacht , destroyed German morale, and established air superiority through Operation Pointblank 's destruction of German fighter strength in preparation for a ground offensive. The USAAF bombers attacked by day, with British operations – chiefly against industrial cities – by night. Operation Pointblank opened with attacks on targets in Western Europe. General Ira C. Eaker and
Mercedes-Benz M133 engine - Misplaced Pages Continue
3072-644: The Aphrodite drones onto their targets by accompanying CQ-17 "mothership" control aircraft, was approved on 26 June 1944, and assigned to the 388th Bombardment Group stationed at RAF Fersfield , a satellite of RAF Knettishall . The first four drones were sent to Mimoyecques (V-3 site), the Siracourt V-1 bunker , and the V-2 Blockhaus d'Éperlecques at Watten, and La Coupole at Wizernes on 4 August, causing little damage and two pilots were killed. On August 12,
3168-667: The B-17 once holding the record for the highest production rate for any large aircraft. The aircraft went on to serve in every World War II combat zone, and by the time production ended in May 1945, 12,731 B-17s had been built by Boeing, Douglas , and Vega (a subsidiary of Lockheed ). Though the crash of the prototype 299 in 1935 had almost wiped out Boeing, now it was seen as a boon. Instead of building models based on experimental engineering, Boeing had been hard at work developing their bomber and now had versions ready for production far better than would have been possible otherwise. One of
3264-466: The B-17 were designed defensively, the large-tailed B-17E was the first model primarily focused on offensive warfare. The B-17E was an extensive revision of the Model 299 design: The fuselage was extended by 10 ft (3.0 m); a much larger rear fuselage, vertical tailfin, rudder, and horizontal stabilizer were added; a gunner's position was added in the new tail ; the nose (especially the bombardier's framed, 10-panel nose glazing) remained relatively
3360-539: The B-17B was altered to include larger rudders and flaps . The B-17C changed from three bulged, oval-shaped gun blisters to two flush, oval-shaped gun window openings, and on the lower fuselage, a single "bathtub" gun gondola housing, which resembled the similarly configured and located Bodenlafette /"Bola" ventral defensive emplacement on the German Heinkel He 111 P-series medium bomber. While models A through D of
3456-547: The Big Week raids. By September 1944, 27 of the 42 bomb groups of the 8th Air Force and six of the 21 groups of the 15th Air Force used B-17s. Losses to flak continued to take a high toll of heavy bombers through 1944, but the war in Europe was being won by the Allies. And by 27 April 1945, 2 days after the last heavy bombing mission in Europe, the rate of aircraft loss was so low that replacement aircraft were no longer arriving and
3552-465: The Boeing factory designation of Model 299, was designed by a team of engineers led by E. Gifford Emery and Edward Curtis Wells , and was built at Boeing's own expense. It combined features of the company's experimental XB-15 bomber and 247 transport. The B-17's armament consisted of five .30 caliber (7.62 mm) machine guns , with a payload up to 4,800 lb (2,200 kg) of bombs on two racks in
3648-621: The Eighth Air Force placed highest priority on attacks on the German aircraft industry, especially fighter assembly plants, engine factories, and ball-bearing manufacturers. Attacks began in April 1943 on heavily fortified key industrial plants in Bremen and Recklinghausen . Since the airfield bombings were not appreciably reducing German fighter strength, additional B-17 groups were formed, and Eaker ordered major missions deeper into Germany against important industrial targets. The 8th Air Force then targeted
3744-577: The FEAF received word of the attack on Pearl Harbor, General Lewis H. Brereton sent his bombers and fighters on various patrol missions to prevent them from being caught on the ground. Brereton planned B-17 raids on Japanese airfields in Formosa , in accordance with Rainbow 5 war plan directives, but this was overruled by General Douglas MacArthur. A series of disputed discussions and decisions , followed by several confusing and false reports of air attacks, delayed
3840-654: The Model 299. In one of their first missions, three B-17s, directed by lead navigator Lieutenant Curtis LeMay , were sent by General Andrews to "intercept" and photograph the Italian ocean liner Rex 610 miles (980 km) off the Atlantic coast. The mission was successful and widely publicized. The 13th Y1B-17 was delivered to the Material Division at Wright Field, Ohio, to be used for flight testing. A 14th Y1B-17 ( 37-369 ), originally constructed for ground testing of
3936-499: The RAF had lost eight B-17Cs in combat and had experienced numerous mechanical problems, and Bomber Command abandoned daylight bombing raids using the Fortress I because of the aircraft's poor performance. The experience showed both the RAF and USAAF that the B-17C was not ready for combat, and that improved defenses, larger bomb loads, and more accurate bombing methods were required. However,
Mercedes-Benz M133 engine - Misplaced Pages Continue
4032-527: 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
4128-405: The U.S. Navy was giving the flight a 21-gun salute to celebrate the arrival of the bombers, after which he realized that Pearl Harbor was under attack. The Fortress came under fire from Japanese fighter aircraft, though the crew was unharmed with the exception of one member who suffered an abrasion on his hand. Japanese activity forced them to divert from Hickam Field to Bellows Field . On landing,
4224-585: The USAAF continued using the B-17 as a day bomber, despite misgivings by the RAF that attempts at daylight bombing would be ineffective. As use by Bomber Command had been curtailed, the RAF transferred its remaining Fortress Mk.I aircraft to Coastal Command for use as a long-range maritime patrol aircraft. These were augmented starting in July 1942 by 45 Fortress Mk.IIA (B-17E) followed by 19 Fortress Mk II (B-17F) and three Fortress Mk III (B-17G). A Fortress IIA from No. 206 Squadron RAF sank U-627 on 27 October 1942,
4320-744: 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
4416-544: The United States, when one was destroyed in a fatal mid-air collision with another warbird at an airshow. On 8 August 1934, the USAAC tendered a proposal for a multiengine bomber to replace the Martin B-10 . The Air Corps was looking for a bomber capable of reinforcing the air forces in Hawaii, Panama, and Alaska. Requirements were for it to carry a "useful bombload" at an altitude of 10,000 ft (3,000 m) for 10 hours with
4512-575: The Wright engines normally used on the B-17 become unavailable. The only prototype XB-38 to fly crashed on its ninth flight, and the concept was abandoned. The Allison V-1710 was reallocated to fighter aircraft. The YB-40 was a heavily armed modification of the standard B-17 used before the North American P-51 Mustang , an effective long-range fighter, became available to act as escort. Additional armament included an additional dorsal turret in
4608-587: The Y1B-17. Also, the Y1B-17A's new service ceiling was more than 2 miles (3,200 m) higher at 38,000 feet (12,000 m), compared to the Y1B-17's 27,800 feet (8,500 m). These turbo-superchargers were incorporated into the B-17B. Opposition to the Air Corps' ambitions for the acquisition of more B-17s faded, and in late 1937, 10 more aircraft designated B-17B were ordered to equip two bombardment groups, one on each U.S. coast. Improved with larger flaps and rudder and
4704-595: The aircraft overran the runway and ran into a ditch, where it was then strafed. Although initially deemed repairable, 40-2049 (11th BG / 38th RS) received more than 200 bullet holes and never flew again. Ten of the 12 Fortresses survived the attack. By 1941, the Far East Air Force (FEAF) based at Clark Field in the Philippines had 35 B-17s, with the War Department eventually planning to raise that to 165. When
4800-467: The airframe's strength, was upgraded by Boeing with exhaust-driven General Electric turbo-superchargers , and designated Y1B-17A. Designed by Sanford Moss , engine exhaust gases turned the turbine's steel-alloy blades, forcing high-pressure air into the Wright Cyclone GR-1820-39 engine supercharger. Scheduled to fly in 1937, it encountered problems with the turbochargers, and its first flight
4896-417: The attack was successful at disrupting the entire works, severely curtailing work there for the remainder of the war, it was at an extreme cost. Of the 291 attacking Fortresses, 60 were shot down over Germany, five crashed on approach to Britain, and 12 more were scrapped due to damage – a loss of 77 B-17s. Additionally, 122 bombers were damaged and needed repairs before their next flights. Of 2,900 men in
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#17328633327224992-531: The authorization of the sortie. By the time the B-17s and escorting Curtiss P-40 Warhawk fighters were about to get airborne, they were destroyed by Japanese bombers of the 11th Air Fleet . The FEAF lost half its aircraft during the first strike, and was all but destroyed over the next few days. Another early World War II Pacific engagement, on 10 December 1941, involved Colin Kelly , who reportedly crashed his B-17 into
5088-585: The ball-bearing factories in Schweinfurt , hoping to cripple the war effort there. The first raid on 17 August 1943 did not result in critical damage to the factories, with the 230 attacking B-17s being intercepted by an estimated 300 Luftwaffe fighters. The Germans shot down 36 aircraft with the loss of 200 men, and coupled with a raid earlier in the day against Regensburg , a total of 60 B-17s were lost that day. A second attempt on Schweinfurt on 14 October 1943 later came to be known as " Black Thursday ". While
5184-436: The bomb bay behind the cockpit. The aircraft was powered by four Pratt & Whitney R-1690 Hornet radial engines , each producing 750 hp (600 kW) at 7,000 ft (2,100 m). The first flight of the Model 299 was on 28 July 1935 with Boeing chief test pilot Leslie Tower at the controls. The day before, Richard Williams, a reporter for The Seattle Times , coined the name "Flying Fortress" when – observing
5280-456: The bombing missions were directed against German aircraft production. German fighters needed to respond, and the North American P-51 Mustang and Republic P-47 Thunderbolt fighters (equipped with improved drop tanks to extend their range) accompanying the American heavies all the way to and from the targets engaged them. The escort fighters reduced the loss rate to below 7%, with a total of 247 B-17s lost in 3,500 sorties while taking part in
5376-558: The bombs landing in the target area. Two additional groups arrived in Britain at the same time, bringing with them the first B-17Fs, which served as the primary AAF heavy bomber fighting the Germans until September 1943. As the raids of the American bombing campaign grew in numbers and frequency, German interception efforts grew in strength (such as during the attempted bombing of Kiel on 13 June 1943 ), such that unescorted bombing missions came to be discouraged. The two different strategies of
5472-449: 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
5568-413: The crews, about 650 did not return, although some survived as prisoners of war . Only 33 bombers landed without damage. These losses were a result of concentrated attacks by over 300 German fighters. Such high losses of aircrews could not be sustained, and the USAAF, recognizing the vulnerability of heavy bombers to interceptors when operating alone, suspended daylight bomber raids deep into Germany until
5664-485: The cylinder walls to reduce friction, and zircon in the cylinder heads to increase thermal conductivity. The cooling system is also based on the one found in the Mercedes-Benz SLS AMG . The M133 was updated in 2015, and features performance improvements of 15 kW (20 PS; 20 hp) and 25 N⋅m (18 lb⋅ft). Turbocharger In an internal combustion engine , a turbocharger (also known as
5760-631: The development of an escort fighter that could protect the bombers all the way from the United Kingdom to Germany and back. At the same time, the German nightfighting ability noticeably improved to counter the nighttime strikes, challenging the conventional faith in the cover of darkness. The 8th Air Force alone lost 176 bombers in October 1943, and was to suffer similar casualties on 11 January 1944 on missions to Oschersleben , Halberstadt , and Brunswick . Lieutenant General James Doolittle , commander of
5856-498: The earlier, 10-panel framed bombardier's nose glazing from the B subtype with an enlarged, nearly frameless Plexiglas bombardier's nose enclosure for improved forward vision. Two experimental versions of the B-17 were flown under different designations, the XB-38 'Flying Fortress' and the YB-40 'Flying Fortress .' The XB-38 was an engine testbed for Allison V-1710 liquid-cooled engines, should
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#17328633327225952-403: 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
6048-559: 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
6144-418: 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
6240-493: The evaluation, thus disqualifying it from the competition. While the Air Corps was still enthusiastic about the aircraft's potential, Army officials were daunted by its cost; Douglas quoted a unit price of $ 58,200 (equivalent to $ 1,018,000 in 2023 ) based on a production order of 220 aircraft, compared with $ 99,620 (equivalent to $ 1,743,000 in 2023 ) from Boeing. MacArthur's successor, Army Chief of Staff Malin Craig , canceled
6336-619: The expense of bomb load. It also developed a reputation for toughness based upon stories and photos of badly damaged B-17s safely returning to base. The B-17 saw early action in the Pacific War , where it conducted air raids against Japanese shipping and airfields. But it was primarily employed by the USAAF in the daylight component of the Allied strategic bombing campaign over Europe, complementing RAF Bomber Command 's night bombers in attacking German industrial, military and civilian targets. Of
6432-529: The final moments before release. The USAAF began building up its air forces in Europe using B-17Es soon after entering the war. The first Eighth Air Force units arrived in High Wycombe, England , on 12 May 1942, to form the 97th Bomb Group. On 17 August 1942, 12 B-17Es of the 97th, with the lead aircraft piloted by Major Paul Tibbets and carrying Brigadier General Ira Eaker as an observer, were close escorted by four squadrons of RAF Spitfire IXs (and
6528-674: The first of 11 U-boat kills credited to RAF Fortress bombers during the war. As sufficient Consolidated Liberators finally became available, Coastal Command withdrew the Fortress from the Azores, transferring the type to the meteorological reconnaissance role. Three squadrons undertook Met profiles from airfields in Iceland, Scotland, and England, gathering data for vital weather forecasting purposes. The RAF's No. 223 Squadron , as part of 100 Group , operated several Fortresses equipped with an electronic warfare system known as " Airborne Cigar " (ABC). This
6624-410: 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
6720-400: 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
6816-404: 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
6912-410: 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
7008-468: The ground soon after takeoff, bursting into flames. Though initially surviving the impact, Hill died within a few hours, and Tower on 19 November. Post-accident interviews with Tower and Putt determined the control surface gust lock had not been released. Doyle notes, "The loss of Hill and Tower, and the Model 299, was directly responsible for the creation of the modern written checklist used by pilots to this day." The crashed Model 299 could not finish
7104-508: The gun stations were finalized, and other adjustments were completed. The B-17G was the final version of the Flying Fortress, incorporating all changes made to its predecessor, the B-17F, and in total, 8,680 were built, the last (by Lockheed) on 28 July 1945. Many B-17Gs were converted for other missions such as cargo hauling, engine testing, and reconnaissance . Initially designated SB-17G,
7200-410: The head of GHQ Air Force. MacArthur and Andrews both believed that the capabilities of large four-engined aircraft exceeded those of shorter-ranged, twin-engine aircraft, and that the B-17 was better suited to new, emerging USAAC doctrine. Their opinions were shared by the air corps procurement officers, and even before the competition had finished, they suggested buying 65 B-17s. On 30 October 1935,
7296-499: 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
7392-418: The large number of machine guns sticking out from the new aircraft – he described it as a "15-ton flying fortress" in a picture caption. The most distinctive mount was in the nose, which allowed the single machine gun to be fired toward nearly all frontal angles. Boeing was quick to see the value of the name and had it trademarked for use. Boeing also claimed in some of the early press releases that Model 299
7488-453: The lighter bombers once they had dropped their bombs, so the project was abandoned and finally phased out in July 1943. The final production blocks of the B-17F from Douglas' plants did, however, adopt the YB-40's "chin turret", giving them a much-improved forward defense capability. By the time the definitive B-17G appeared, the number of guns had been increased from seven to 13, the designs of
7584-442: The most significant weapons of World War II would be ready, but only by a hair. The aircraft went through several alterations in each of its design stages and variants. Of the 13 YB-17s ordered for service testing, 12 were used by the 2nd Bomb Group at Langley Field, Virginia, to develop heavy bombing techniques, and the 13th was used for flight testing at the Material Division at Wright Field, Ohio. Experiments on this aircraft led to
7680-526: The number of bombers per bomb group was reduced. The Combined Bomber Offensive was effectively complete. On 7 December 1941, a group of 12 B-17s of the 38th (four B-17C) and 88th (eight B-17E) Reconnaissance Squadrons, en route to reinforce the Philippines, was flown into Pearl Harbor from Hamilton Field, California , arriving while the surprise attack on Pearl Harbor was going on. Leonard "Smitty" Smith Humiston, co-pilot on First Lieutenant Robert H. Richards' B-17C, AAF S/N 40-2049 , reported that he thought
7776-459: The order for 65 YB-17s and ordered 133 of the twin-engined Douglas B-18 Bolo, instead. Secretary of War Harry Hines Woodring in October 1938 decided that no four-engine bombers, including B-17s, would be purchased by the War Department in 1939. The loss was not total... But Boeing's hopes for a substantial bomber contract were dashed. Despite the crash, the USAAC had been impressed by the prototype's performance, and on 17 January 1936, through
7872-407: 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
7968-548: 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
8064-547: The prototype crashed), the term "XB-17" was retroactively applied to the NX13372's airframe and has entered the lexicon to describe the first Flying Fortress. Between 1 March and 4 August 1937, 12 of the 13 Y1B-17s were delivered to the 2nd Bombardment Group at Langley Field in Virginia for operational development and flight tests. One suggestion adopted was the use of a preflight checklist to avoid accidents such as that which befell
8160-419: The radio room, a remotely operated and fired Bendix-built "chin turret" directly below the bombardier's accommodation, and twin 50 caliber (12.7 mm) guns in each of the waist positions. The ammunition load was over 11,000 rounds. All of these modifications made the YB-40 well over 10,000 lb (4,500 kg) heavier than a fully loaded B-17F. The YB-40s with their greater weight, had trouble keeping up with
8256-399: 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
8352-696: The roughly 1.5 million tons of bombs dropped on Nazi Germany and its occupied territories by Allied aircraft, over 640,000 tons (42.6%) were dropped from B-17s. At the start of 2024, six aircraft remain in flying condition. About 50 survive in storage or are on static display, the oldest of which is The Swoose , a B-17D which was flown in combat in the Pacific on the first day of the United States' involvement in World War II. There are also several reasonably complete wrecks, such as underwater, that have been found. B-17 survivors gained national attention in 2022 in
8448-410: The same as the earlier B through D versions had; a Sperry electrically powered manned dorsal gun turret just behind the cockpit was added; a similarly powered (also built by Sperry) manned ventral ball turret just aft of the bomb bay – replaced the relatively hard-to-use, Sperry model 645705-D remotely operated ventral turret on the earliest examples of the E variant. These modifications resulted in
8544-402: The then-secret Norden bombsight , known as the "Blue Ox", which was an optical electromechanical gyrostabilized analog computer . The device was able to determine, from variables put in by the bombardier, the point at which the bombs should be released to hit the target. The bombardier essentially took over flight control of the aircraft during the bomb run, maintaining a level altitude during
8640-407: 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
8736-458: The use of a quartet of General Electric turbo-superchargers, which later became standard on the B-17 line. A 14th aircraft, the YB-17A, originally destined for ground testing only and upgraded with the turbochargers, was redesignated B-17A after testing had finished. As the production line developed, Boeing engineers continued to improve upon the basic design. To enhance performance at slower speeds,
8832-518: Was delayed until 29 April 1938. The aircraft was delivered to the Army on 31 January 1939. Once service testing was complete, the Y1B-17s and Y1B-17A were redesignated B-17 and B-17A, respectively, to signify the change to operational status. The Y1B-17A had a maximum speed of 311 mph (270 kn; 501 km/h), at its best operational altitude, compared to 239 mph (208 kn; 385 km/h) for
8928-792: Was effectively scrapped in early 1945. The B-17 began operations in World War II with the Royal Air Force (RAF) in 1941, and in the Southwest Pacific with the U.S. Army. During World War II, the B-17 equipped 32 overseas combat groups, inventory peaking in August 1944 at 4,574 USAAF aircraft worldwide. The British heavy bombers, the Avro Lancaster and Handley Page Halifax , dropped 608,612 long tons (681,645 short tons; 618,378 t) and 224,207 long tons (251,112 short tons; 227,805 t) respectively. The RAF entered World War II without
9024-401: Was operated by German-speaking radio operators to identify and jam German ground controllers' broadcasts to their nightfighters . They could also pose as ground controllers themselves to steer nightfighters away from the bomber streams . The air corps – renamed United States Army Air Forces (USAAF) on 20 June 1941 – used the B-17 and other bombers to bomb from high altitudes with the aid of
9120-598: Was the first combat aircraft that could continue its mission if one of its four engines failed. On 20 August 1935 , the prototype flew from Seattle to Wright Field in nine hours and three minutes with an average ground speed of 252 mph (219 kn; 406 km/h), much faster than the competition. At the fly-off, the four-engined Boeing's performance was superior to those of the twin-engine DB-1 and Model 146. In March 1935 Army Chief of Staff General Douglas MacArthur created GHQ Air Force and promoted lieutenant colonel Frank Maxwell Andrews to brigadier general to become
9216-529: Was unsuccessful. On 24 July three B-17s of 90 Squadron took part in a raid on the German capital ship Gneisenau and Prinz Eugen anchored in Brest from 30,000 ft (9,100 m), to draw German fighters away from 18 Handley Page Hampdens attacking at lower altitudes, and in time for 79 Vickers Wellingtons to attack later with the German fighters refueling. The operation did not work as expected, with 90 Squadron's Fortresses being unopposed. By September,
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