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From Wikipedia, the free encyclopedia

XB-15
XB-15 Bomber.jpg
XB-15 on a test flight
Role Heavy bomber
Manufacturer Boeing
First flight 15 October 1937
Status Canceled
Primary user United States Army Air Corps
Number built 1 prototype
Developed into Boeing Y1B-20

The Boeing XB-15 (Boeing 294) was a United States bomber aircraft designed in 1934 as a test for the United States Army Air Corps (USAAC) to see if it would be possible to build a heavy bomber with a 5,000 mi (8,000 km) range. For a year beginning in mid-1935 it was designated the XBLR-1. When it first flew in 1937, it was the most massive and voluminous aircraft ever built in the US. It set a number of load-to-altitude records for land-based aircraft, including carrying a 31,205 lb (14,154 kg) payload to 8,200 ft (2,500 m) on 30 July 1939.[1]

The aircraft's immense size allowed flight engineers to enter the wing through a crawlway and make minor repairs in flight. A 5,000 mi (8,000 km) flight took 33 hours at its 152 mph (245 km/h) cruising speed; the crew was made up of several shifts, and bunks allowed them to sleep when off duty.

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  • ✪ X-15 The Ultimate Flying Machine
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  • ✪ Boeing X-32A/B JSF competition video compilation (part 1)
  • ✪ X-37B - What is it doing up there?

Transcription

"It was the ultimate flying machine, no airplane can live up to what the x-15 did", that's what retired test pilot and astronaut Joe angle said of the first real space plane and 50 years after it's record-breaking flight of October 3rd 1967 when US Air Force test pilot William J Knight achieves a top speed of mach 6.72, 4519 miles an hour or 7273 km/h it is still the fastest manned powered aircraft and if you thought the SR-71 blackbird was the fastest jet then you're absolutely correct because the X-15 wasn't a jet, it was a rocket-powered single seater aircraft that looked a bit like an oversized art and had to be launched from the underside of a modified B-52 at 45,000 feet because the XLR 99 rocket engine would burn through all of its fuel in just two minutes. Not only did the x-15 set speed records it also went past the point of were space officially starts at 100 kilometers 62.1 miles on two occasions both times piloted by Joseph A Walker at at 105.9km, 347,000 feet and 107.8km 353,000 feet. Although in the 1960s the US Air Force considered space for start at 80 kilometers or 50 mile,s any crew that flew over the 50 mile limit were awarded an astronaut badge, 13 of the X-15 flights went higher than this and two of the pilots Neil Armstrong and Joe Engle went on to become fully fledged astronauts in the Apollo and space shuttle programs. But apart from being a record-breaking aircraft research from the X-15 program led to things like the first full pressure suit that would work in space, the first use of reaction controls the little gas jets at position spacecraft in space, the first use of super alloys in the plane structure that could withstand the heat of a hypersonic reentry and the development of the first large restartable throttleable rocket engine, the XLR 99. These are a small selection of the developments and discoveries that would go on to contribute to later space programs including the Mercury, Gemini, Apollo and the Space Shuttle. in the early 1950s research that started with a bell X-1 the first supersonic plane began looking into the problems that would be encountered by space flight. At the time it was still unknown as to what would happen to the stability as well as other issues of a craft when traveling at hypersonic speeds that's between Mach 5 and Mach 10 or between about or between about 3800 and 7,700 mph ( 6,200 to 12,400 km/h). This will be the type of speed that would be required to get to the edge of space and the re-entry. In 1952 the National Advisory Committee for Aeronautics or in NACA, NASA's predecessor started looking into the problems. By 1954 they had contacted both the US Navy and the Air Force to propose building a research aircraft that would become the X-15. By 1956 the contract for the airframe had gone to North American Aviation and the rocket engine was to be built by Reaction Motors. After the contract had been awarded to North American and before the launch of Sputnik in october 1957, North American had considered making an X-15B orbital space plane that would carry a crew of two by launching it into low-earth orbit on top of a pair of SM-64 in Navajo missile boosters. If this had been done it could have predated the Space Shuttle by over 20 years. However after Sputnik the X-15B orbital space plane idea was shelved and revived several times until it was finally over taken by the mercury space program when NACA became NASA in 1958. In 1960 NASA considered using the b-52 an X-15 as a launch system for the Blue Scout rocket to carry small satellites into orbit. The B-52 would be the first stage with the x-15 being the second stage carrying the Blue Scout which will be the third stage to 180,000 feet before it was launched, the payload into orbit. This idea of using high-performance aircraft as launch platforms is now gaining interest once more as a method of launching for new generation and nano satellites into orbit. Three X-15's were built and performed 199 missions over a nine-year period from 1959 to 1968. Due to delays in the engine development the first 24 flights used to smaller XLR 11 engines but in 1960 the XLR-99 engines were fitted over tripling the thrust to 57,000 pounds and these will be used throughout the remainder of the flight programs. The X-15 generally performed two types of research flight paths, level high speed runs at around a 100,000 feet and altitude runs where it would try to fly as high as possible. because of the speeds that the x-15 could reach, the temperature on the exposed areas like the leading edges of the wings and the nose could reach 1,200 degrees Fahrenheit or 650 degrees celsius at mach 6. The fuselage was made from titanium and covered Inconel X, a nickel chromium based super alloy used to make the thrust chamber in the Saturn F1 engines and could withstand the high temperatures without weakening. Although Inconel was capable of withstanding the heat stress, the stresses that built up between the hot and cooler areas was causing concern as NASA was looking at testing a hypersonic ramjet engine that in theory could push the X-15 to around Mach 8 that's around 6,000 miles an hour or 9,900 km/h. NASA were also looking for an ablative coating, that's a layer of material the burns and turns the gas to protect the structure underneath and could easily be applied to reusable spacecraft to cut the refurbishment costs and turnaround times, the X-15 would be an ideal test bed for this type of heat shield. After a minor crash in 1967 the second X-15 was rebuilt and renamed the X-15A-2 it was extended by 28" about 71 centimeters for the extra hydrogen tanks of a proposed ramjet engine and fitted with detachable auxiliary fuel tanks that increase the flight time by 60 seconds. It was also coated in an experimental ablative coating. It took six weeks to apply of a spray-on coating and when it was done the X-15A-2 was now white instead black. It was also fitted with a dummy ramjet to test the design but during the record-breaking flight of October 3rd 1967, it also revealed major issues data from the flight showed that in places like the nose cone and the wing edges whilst the coating had worked it also prevented the Inconel structure underneath to cool as it was designed and it nearly brought about the structural failure of the X-15 due to the uneven heat stresses that had built up, also when the craft reached mach 6 the gases released from the ablator turned the cockpit glass opaque so the pilot could no longer see out of it. Luckily one of the two windows have been fitted with a metal eyelid which was raised before the landing so he could use the other unaffected window. Due to unexpected air flow problems the temperature was so high that the dummy ramjet was seriously heat damaged and three of the four explosive bolts which held it to the mounting pylon ignited, it was then ripped from the aircraft as the final bolt failed and this was the end of the ramjet powered X-15. It was said that the X-15A-2 came back looking like a burnt-out firework and whilst it was sent to be refurbished the idea of the ablative coating was dropped due to the problems of getting an adequate depth of the ablator over the structure. Due to the research nature of the X-15 there were accidents and incidents with some of the test flights but there was only one fatal crash on the 15th November 1967, when Air Force test pilot Major Michael J Adams lost control at 230,000 feet with the X-15 entering a Mach 5 spin. There were no recommended techniques to recover from a supersonic spin as no one knew what the X-15 would do in such a situation. Although Adams tried to recover it, at 65,000 feet whilst traveling at Mach 3.93 and tumbling through the air the X-15 broke up scattering the wreckage over a 50 square mile area. As the 1960s drew to a close and after the fatal crash, support within NASA of the X-15 project waned, many of the major research goals have been completed in the years before and now spacecraft were the new priority. The last flight took place on the 24th October 1968 piloted by Bill Dana and within a year the remaining X-15's were retired and one of the most influential aircraft research programs was shut down for good. The two remaining X-15's are now on display in the National Air and Space Museum Washington DC and in the National Museum of United States Air Force at Wright-Patterson Air Force Base. And as always thanks for watching and please subscribe, rate and share.

Contents

Design and development

The XB-15's .50 in (12.7 mm) front gun turret
The XB-15's .50 in (12.7 mm) front gun turret

The specification that produced the XB-15 began in mid-1933 as "Project A", USAAC discussions regarding the possibility of flying a very large bomber with a range of 5,000 mi (8,000 km).[2] In April 1934 the USAAC contracted with Boeing and Martin to design a bomber capable of carrying 2,000 lb (910 kg) at 200 mph (320 km/h) over a distance of 5,000 miles.[3] Boeing gave the project the internal name of Model 294, while the USAAC called it the XB-15. Martin's design, the XB-16, was judged inferior by the USAAC before a prototype was built, and was canceled.[2]

The Boeing design team, headed by Jack Kylstra, initially intended the aircraft to use 2,600 hp (1,900 kW) Allison V-3420 liquid-cooled W engines; since these were not ready, 850 hp (630 kW) Pratt & Whitney R-1830 air-cooled radial engines were used instead.[2]

Starting in August 1934, Boeing began designing the Model 299 in answer to a proposal by the USAAC to replace the Martin B-10 bomber. The Model 299 design team incorporated elements of the Boeing 247[4] and the Model 294, especially its use of four engines.[5] The Model 299 design team worked alongside Klystra's team, but difficulties in fabricating such a large aircraft slowed progress on the 294.[3] The Model 299 flew first, on 28 July 1935.[6]

In mid-1935, the USAAC combined Project A with Project D; a proposal asking for "the maximum feasible range into the future." The combined program was designated BLR for "Bomber, Long Range". The XB-15 was renamed the XBLR-1; it was joined under the BLR program by two other projects: one from Douglas Aircraft, the XBLR-2 which later became the XB-19; and one from Sikorsky Aircraft called the XBLR-3, later canceled. The next year, the XBLR was dropped and the Boeing prototype was once again the XB-15.[2]

Unusual features that the XB-15 pioneered included an autopilot, deicing equipment, and two gasoline generators used as auxiliary power units (independent of the main engines) to power the 110-volt electrical system. The main engines were serviceable in flight using an access tunnel inside the wing. The aircraft contained a sizable crew compartment with bunkbeds, a galley and a lavatory. Finally, in September 1937 construction was finished, and on 15 October it first flew. Its double-wheel main landing gear remained down from takeoff to landing. On 2 December 1937, the XB-15 flew from Seattle to Wright Field in Ohio to be accepted by the USAAC for testing.[7]

With the Twin Wasp radial engines installed — the same number and type of engines fitted to the later Consolidated B-24 Liberator, with individual turbochargers added on the Liberators' Twin Wasp powerplants — the specified speed of 200 mph for the Twin Wasp-powered XB-15 was not quite reached even when the aircraft was empty; the best speed attained in level flight was 197 mph (317 km/h).[7] Loaded with the specified 2,000 pounds, the maximum speed was a disappointing 145 mph (233 km/h).[3] This was considered too slow for a combat aircraft, and the project was abandoned.[8] However, Boeing engineers projected that the prototype would be capable of carrying the heaviest air cargo to date: a load of 8,000 lb (3,600 kg).[3]

The design challenges stemming from the great size of the XB-15 were difficult to master, but the lessons learned by Boeing were later applied to the Model 314 flying boat, which essentially used the XB-15's wing design[2] with four of the more powerful Wright Twin Cyclone fourteen-cylinder radials for power. In 1938, the USAAC proposed to update the XB-15 to make the slightly larger Y1B-20, again using four Wright Twin Cyclones as with the Boeing 314, but the Secretary of War, Harry Hines Woodring, canceled the project before construction began, in favor of the expensive Douglas XB-19. Boeing went ahead with an internal redesign of the XB-15 called Model 316, a very heavy bomber with a high wing, a pressurized cabin and tricycle gear. The Model 316 was not built. The progression of design work starting with the XB-15 finally bore fruit with the Model 345 presented to the USAAC in May 1940, the very heavy bomber which resulted in the USAAF's Boeing B-29 Superfortress.[7]

Operational history

A Red Cross agent and Major Caleb V. Haynes supervise the loading of emergency medical supplies on the XB-15 in early 1939
A Red Cross agent and Major Caleb V. Haynes supervise the loading of emergency medical supplies on the XB-15 in early 1939

The single prototype was assigned to the 2nd Bombardment Group at Langley Field, Virginia. Following the 24 January 1939 Chillán earthquake in Chile, the prototype flew a relief mission, carrying medical supplies. Commanded by Major Caleb V. Haynes, the aircraft carried 3,250 lb (1,470 kg) of American Red Cross emergency supplies to Santiago, making only two stops along the way, at France Field in the Panama Canal Zone, and at Lima, Peru.[9][10] Haynes was awarded the Distinguished Flying Cross and the Order of the Merit of Chile, and the whole crew earned the MacKay Trophy.[9]

Haynes piloted the XB-15 again on 10 June 1939 to return home the body of Mexican flier Francisco Sarabia who had died in a crash in the Potomac River. After flying back from Mexico City, Haynes and his copilot William D. Old undertook flight tests at Fairfield, Ohio with heavy loads. The XB-15 lifted a 22,046 pounds (10,000 kg) payload to a height of 8,228 feet (2,508 m), and 31,164 pounds (14,136 kg) to 6,561.6 feet (2,000.0 m), setting two world records for landplanes.[11] Haynes was awarded certificates issued by the National Aeronautics Association (NAA) for an international record for "the greatest payload carried to an altitude of 2,000 metres".[12] The XB-15 was not fast for a bomber but it was the fastest aircraft that could carry so much weight, and for such distances. In July 1939 Haynes received certificates from the NAA for an international 5,000 km (3,100 mi) speed record with a 2,000 kg (4,400 lb) payload. The latter performance also established a national closed circuit distance record of 3,129.241 miles (5,036.025 km).[12]

Flying from Langley, the XB-15 arrived at Albrook Field in Panama on 10 April 1940 and immediately began classified bombing tests of canal lock protections, commanded by Haynes and including Captain Curtis LeMay as navigator and Lieutenant John B. Montgomery as bombardier.[13] Of 150 bombs dropped, only three hit the target: a specially made bunker simulating a reinforced machine room. The few hits nevertheless led to improvements in bunker design.[10] In early May, Haynes and LeMay made a survey flight from Panama over the Galapagos islands, the inspection including Baltra Island.[8] Haynes piloted the XB-15 back to the United States, leaving Panama on 11 May 1940.[13]

In late 1940 the XB-15's defensive guns were removed at Duncan Field in Texas. Seats were attached so that Lend Lease aircraft ferry crews could be returned after delivery.[13]

XC-105 "Grandpappy" in Panama
XC-105 "Grandpappy" in Panama
The XC-105 parked on Baltra Island in the Galápagos. Flying above are two Consolidated B-24 Liberators.
The XC-105 parked on Baltra Island in the Galápagos. Flying above are two Consolidated B-24 Liberators.
The flight crew in front of "Grandpappy" in Panama in 1943. Note the absence of the nose gun.
The flight crew in front of "Grandpappy" in Panama in 1943. Note the absence of the nose gun.

Cargo aircraft

On 6 May 1943 the Army Air Forces converted the only prototype into a transport, the aircraft being redesignated XC-105. A cargo hoist was mounted, and cargo doors fitted. Its maximum gross weight was increased to 92,000 lb (42,000 kg).[7] By this time, the aircraft was nicknamed "Grandpappy" by 20th Troop Carrier Squadron airmen.[14] It displayed nose art depicting an elephant carrying a large crate on its back labeled "supplies".[13] During World War II, the XC-105 carried freight and personnel to and from Florida, and throughout the Caribbean, based out of Albrook Field beginning in June 1943. Hundreds of young women were flown in "Grandpappy" from Miami to the Canal Zone to engage in US government work; these trips were dubbed the "Georgia Peach Run".[13] "Grandpappy" traveled to the Galapagos, landing on Baltra Island at the same airfield built following the XB-15 aerial survey of May 1940.[13]

"Grandpappy"′s flight crew, reduced to six men, described the aircraft as difficult to fly and service. Two fires and a complete failure of the electrical system occurred in the air.[7][13] The aircraft was retired on 18 December 1944, assigned to Panama Air Depot.[13] In June 1945, it was ordered to be scrapped at Albrook Field in Panama,[7] its engines and internal parts removed along with its vertical stabilizer and rudder. The remaining airframe was deposited at Diablo dump, a swampy landfill southwest of the runway, where it slowly sank from sight.[10][13][14] Squatters built shacks on stilts in the swamp, covering the remains. The former dump is now an industrial area, with "Grandpappy" underneath.[14]

During its 18 months of transport service, the XC-105 carried more than 5,200 passengers, 440,000 lb (200,000 kg) of cargo and 94,000 lb (43,000 kg) of mail. It flew 70 cargo trips and 60 missions including anti-submarine patrol. Unusually, the aircraft was consistently referred to as "he" by its crew.[13]

The XB-15 parked on an airstrip.
The XB-15 parked on an airstrip.

Operators

 United States
2d Bombardment Group
20th Troop Carrier Squadron

Specifications (XB-15)

Data from Boeing Aircraft since 1916 [15]

General characteristics

Performance

Armament

See also

Related development

Aircraft of comparable role, configuration and era

Related lists

References

Notes

  1. ^ The Putnam says the record flight had a payload of 71,000+ lb, but the FAI record book shows 14,000+ kg.
  2. ^ a b c d e Yenne 2005, p. 43.
  3. ^ a b c d Moy 2001, pp. 70–72.
  4. ^ Swanborough and Bowers 1963, p. 74.
  5. ^ Moy 2001, p. 73.
  6. ^ "History: The Boeing Logbook: 1933–1938". Boeing. Archived from the original on December 8, 2006. Retrieved 26 May 2012.
  7. ^ a b c d e f g Kohn 2002 pp. 43–44.
  8. ^ a b Boniface 1999, pp. 64–67.
  9. ^ a b Haulman, Daniel L.One Hundred Years of Flight: USAF Chronology of Significant Air and Space Events 1903–2002. Maxwell AFB, Alabama: Air Force History and Museums Program, Air University Press, 2003.
  10. ^ a b c Liang, Susan Hall. "Grandpappy's dead and buried, but he's not forgotten." The Panama Canal Spillway, 19 October 1979, p. 3. Retrieved: 26 May 2012. Hosted by the University of Florida Digital Collections, George A. Smathers Libraries.
  11. ^ Maurer 1987, pp. 304–307, 355–360, 405–406.
  12. ^ a b "USAF Biography: Major General Caleb V. Haynes". Archived from the original on June 13, 2009. Retrieved June 25, 2014.
  13. ^ a b c d e f g h i j Bouché, Georges G. " 'Grandpappy'-The XB-15." Aerospace Historian, Air Force Historical Foundation, Volume 26, Number 3, September 1979, pp. 171–181.
  14. ^ a b c Millam, Ed S. Jr."Grandpappy". AAHS Journal' (American Aviation Historical Society), Volume 50, 2005, pp. 46–54.
  15. ^ Bowers 1989, p. 230.
  16. ^ "Fact Sheets: Boeing XB-15". National Museum of the United States Air Force. Archived from the original on November 21, 2007. Retrieved 7 August 2009.

Bibliography

  • Boniface, Patrick. "Boeing's Forgotten Monster: XB-15 a Giant in Search of a Cause." Air Enthusiast, 79, January–February 1999.
  • Bowers, Peter M. Boeing Aircraft since 1916. London: Putnam, Third edition, 1989. ISBN 0-85177-804-6.
  • Kohn, Leo. "Boeing XB-15 Super Flying Fortress: U.S. Heavy Bomber". In Ray Merriam. "U. S. Warplanes of World War II." World War II Journal, 69. Bennington, Vermont: Merriam Press, 2002. ISBN 1-57638-167-6.
  • Maurer, Maurer. Aviation in the U.S. Army, 1919–1939. Washington, D.C.: United States Air Force Historical Research Center, Office of Air Force History, 1987. ISBN 0-912799-38-2.
  • Moy, Timothy. War Machines: Transforming Technologies in the U.S. Military, 1920–1940 (Texas A&M University Military History Series, 71)."] College Station, Texas: Texas A&M University Press, 2001. ISBN 1-58544-104-X.
  • Swanborough, F. Gordon and Peter M. Bowers. United States Military aircraft since 1909. London: Putnam, 1963.
  • Yenne, Bill. The Story of the Boeing Company. Minneapolis, Minnesota: Zenith Imprint, 2005. ISBN 0-76032-333-X.

External links

This page was last edited on 4 January 2019, at 03:42
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