World War 2 In Review

Boeing XB-15, 41st Reconnaissance Squadron, near Mitchell Field, Long Island, New York, 1941.

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 airplane 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. [Bowers says the record flight had a payload of 71,000+ lb (32,000+ kg) but the FAI record book shows 14,000+ kg (31,000+ lb)]

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.

Design and Development

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). 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. 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.

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 Twin Wasp air-cooled radial engines were used instead.

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 and the Model 294, especially its use of four engines. The Model 299 design team worked alongside Klystra's team, but difficulties in fabricating such a large aircraft slowed progress on the 294. The Model 299 flew first, on 28 July 1935.

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 designation was dropped and the Boeing prototype was once again the XB-15.

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 it first flew on 15 October. 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.

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 (320 km/h) 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). Loaded with the specified 2,000 pounds (910 kg), the maximum speed was a disappointing 145 mph (233 km/h). This was considered too slow for a combat aircraft, and the project was abandoned. 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).

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 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.

Operational History

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. Haynes was awarded the Distinguished Flying Cross and the Order of the Merit of Chile, and the whole crew earned the MacKay Trophy.

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 Wright Field 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. 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 meters". 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).

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. 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. In early May, Haynes and LeMay made a survey flight from Panama over the Galapagos islands, the inspection including Baltra Island. Haynes piloted the XB-15 back to the United States, leaving Panama on 11 May 1940.

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.

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). By this time, the aircraft was nicknamed "Grandpappy" by 20th Troop Carrier Squadron airmen. It displayed nose art depicting an elephant carrying a large crate on its back labeled "supplies". 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". "Grandpappy" traveled to the Galapagos, landing on Baltra Island at the same airfield built following the XB-15 aerial survey of May 1940.

"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. The aircraft was retired on 18 December 1944, assigned to Panama Air Depot. In June 1945, it was ordered to be scrapped at Albrook Field in Panama, 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. Squatters built shacks on stilts in the swamp, covering the remains. The former dump is now an industrial area, with "Grandpappy" underneath.

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.

Operators

United States

United States Army Air Corps

2nd Bombardment Group

United States Army Air Forces

20th Troop Carrier Squadron

Specifications (XB-15)

Type: Heavy bomber

Manufacturer: Boeing

Status: Canceled

Primary user: United States Army Air Corps

Number built: 1 prototype

First flight: 15 October 1937

Developed into: Boeing Y1B-20

Crew: 10

Length: 87 ft 7 in (26.70 m)

Wingspan: 149 ft 0 in (45.43 m)

Height: 25 ft 10 in (7.87 m)

Wing area: 2,780 sq ft (258.4 m2)

Airfoil:

root: NACA 0018

tip: NACA 0010

Empty weight: 37,709 lb (17,141 kg)

Maximum takeoff weight: 70,706 lb (32,139 kg)

Powerplant: 4 × 14-cylinder Pratt & Whitney R-1830-11 radial engines, 1,000 hp (634 kW) each

Maximum speed: 197 mph (317 km/h, 171 kn) at 5,000 ft (1,500 m)

Cruise speed: 152 mph (245 km/h, 132 kn) at 6,000 ft (1,800 m)

Range: 5,130 mi (8,260 km, 4,460 nmi)

Combat range: 3,400 mi (5,474 km, 2,957 nmi)

Service ceiling: 18,900 ft (5,760 m)

Armament:

Guns:

3 × .30 in (7.62 mm) M1919 Browning machine guns

3 × .50 in (12.7 mm) M2 Browning machine guns

Bombs: 12,000 lb (5,400 kg)

Bibliography

Boniface, Patrick. "Boeing's Forgotten Monster: XB-15 a Giant in Search of a Cause." Air Enthusiast, No. 79, January–February 1999. pp. 64–67.

Bowers, Peter M. Boeing Aircraft since 1916. London: Putnam, Third edition, 1989.

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.

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.

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. I

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.

The same photo used by a postcard publishing company after heavy retouching.

Boeing XB-15 (35-277).

Boeing Model 294 (XB-15) at Boeing Field, Seattle, Washington. The prototype bomber was rolled out for engine tests, 27 September 1937.

Boeing XB-15 at Boeing Field, Seattle, Washington, 27 September 1937.

Boeing XB-15.

Boeing XB-15 at the Boeing plant, Seattle, Washington, 1936.

Boeing XB-15.

Boeing XB-15 takes off on its first flight, Boeing Field, 15 October 1937.

Boeing XB-15, 16 November 1937.

Boeing XB-15, Cleveland, 1937.

Boeing XB-15.

Boeing XB-15 (35-277).

Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit.

Boeing XB-15. This is a cropped version of the previous photo.

Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit.

Boeing XB-15 (35-277).

Boeing XB-15.

Boeing XB-15 (35-277).

Boeing XB-15.

Boeing XB-15, 1937.

Boeing XB-15 in flight over Lake Washington.

Boeing XB-15 at NACA Langley Memorial Aeronautical Laboratory, 13 September 1938.

On February 4, 1939, the XB-15 took off from Langley Field, Virginia, on an Air Corps mercy flight to Chile. Loaded with medical supplies for earthquake victims, the plane landed at Santiago only 30 hours after leaving Langley, including two refueling stops in Panama and Peru.

Boeing XB-15, 49th Bombardment Squadron, 2nd Bombardment Group, Felts Field, Spokane, 11 May 1939.

Boeing XB-15, 49th Bombardment Squadron, 2nd Bombardment Group, Selfridge Field, 1939.

Boeing XB-15.

Boeing XB-15, 49th Bombardment Squadron, 2nd Bombardment Group.

Maj. C.V. Haynes, the Commanding Officer of the 49th Bomb Squadron, Capt. Old also of the 49th BS, and an unidentified officer stand in front of the Boeing XB-15.

2 August 1939: The Boeing Model 294, designated by the U.S. Army Air Corps as the XB-15, serial number 35-277, flown by a crew led by Major Caleb Vance Haynes, set a Fédération Aéronautique Internationale (FAI) World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, when they flew the experimental long range heavy bomber a distance of 3,109 miles at an average speed of 267.67 kilometers per hour (166.32 miles per hour) while carrying a payload of 2,000 kilograms (4,409.25 pounds). The other members of the XB-15 crew were Captain William D. Old, Walter G. Bryte, Jr., A.C. Brandt, Master Sergeant Adolph Cattarius, Staff Sergeant William J. Heldt, Technical Sergeant Daniel L. Spicer and Staff Sergeant James E. Sands.

Boeing XB-15 with formation flying in background. The caption provided with this photo states this was at the Army Air Corps 30th anniversary celebration at Wright Field, 2 August 1939. However, these are the dates for anniversaries in the establishment of what is today the U.S. Air Force: Aeronautical Division, Signal Corps (1 August 1907 – 18 July 1914); Aviation Section, Signal Corps (18 July 1914 – 20 May 1918); Division of Military Aeronautics (20 May 1918 to 24 May 1918)
U.S. Army Air Service (24 May 1918 to 2 July 1926); U.S. Army Air Corps (2 July 1926 to 20 June 1941) and U.S. Army Air Forces (20 June 1941 to 18 September 1947). The only 30th anniversary that matches 2 August 1939 is the purchase of the first aircraft for the Signal Corps on 2 August 1909 and perhaps that is the date being referred to as an anniversary. The caption's author may have assumed that was the date of the beginning of what was in 1939 called the Army Air Corps. The previous photo states that on 2 August 1939 the XB-15 set a world speed record. Perhaps that is what is being celebrated in the photo.

Boeing XB-15, 49th Bombardment Squadron, 2nd Bombardment Group, in flight over the Wright Memorial, Kitty Hawk, North Carolina.

A ¼-scale model of the Boeing XB-15 inside the Full-Scale Wind Tunnel at the National Advisory Committee for Aeronautics (NACA) Langley Memorial Aeronautical Laboratory, Hampton, Virginia. The model has a wingspan of 37.3 feet (11.37 meters).

The flight deck of the Boeing XB-15. The radio operator’s station is on the left, and the navigator’s on the right.

Boeing XB-15 front turret .50-cal. gun installation, 1935.

Boeing XB-15 top turret .50-cal. gun installation.

Boeing XB-15 right rear .30-cal. gun installation.

Boeing XB-15 engine cowlings, 28 April 1937.

Boeing XB-15 left hand outboard oil tank tubing installation in the wing, 26 March 1937.

Boeing XB-15 left hand inboard nacelle, ¾ rear right side, 23 April 1937. Inside the engine nacelle of the XB-15. The engines could be accessed in flight, and the nacelle interior seems roomy enough. Note the oil can mounted lower right. Manufactured by Brookins, it is stamped “Two Gallons”.

Boeing XB-15 landing gear.

On long flights, the Boeing XB-15 had a compartment equipped with berths.

Boeing XB-15 tail.

Boeing XB-15 painted in water color camouflage at Bolling Field, Washington, D.C., during an Air Corps display on January 12-14, 1940.

Boeing XB-15 in water color camouflage paint.

The Aquabelles and members of the 41st Reconnaissance Squadron on the Boeing XB-15, 1941.

Boeing XC-105 "Grandpappy" in Panama. 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). By this time, the aircraft was nicknamed "Grandpappy" by 20th Troop Carrier Squadron airmen. It displayed nose art depicting an elephant carrying a large crate on its back labeled "supplies".

Boeing XB-15 (35-277 c/n 1964) US Army Air Corps. Because of its cargo-carrying capacity, it was redesignated XC-105 on May 6, 1943 and was modified by the PAD. After modification, it was assigned to the 20th Troop Carrier Squadron, Sixth Air Force Service Command, based at Albrook Field in December 1943. During its eight year in service, the XB-15/XC-105 flew 60 combat missions including ASW patrols and 70 cargo trips carrying 5,200 passengers, 440,000 lb (199,581 kg) of cargo and 94,000 lb (42,638 kg) of mail. The XC-105 was placed in storage at the PAD in May 1944 due to structural damage. This one of kind aircraft was ignominiously shoved into the Curundu Swamp, east of Albrook Field, where it slowly sunk into the muck. It remains there to this day.

Boeing XC-105 in 1943, shown in Panama at Albrook Field with the airplane's flight crew posed in front of the nose which is painted with an elephant carrying supplies and the name "Grandpappy". One of the crewmen is Master Sgt. Laird N. Rosborough, the radio operator. 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". "Grandpappy" traveled to the Galapagos, landing on Baltra Island at the same airfield built following the XB-15 aerial survey of May 1940.

Boeing XC-105, circa 1943/1944. "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. The aircraft was retired on 18 December 1944, assigned to Panama Air Depot. In June 1945, it was ordered to be scrapped at Albrook Field in Panama, its engines and internal parts removed along with its vertical stabilizer and rudder.

Boeing XC-105 parked on Baltra Island in the Galápagos. Flying above are two Consolidated B-24 Liberators. The remaining airframe was deposited at Diablo dump, a swampy landfill southwest of the runway, where it slowly sank from sight. Squatters built shacks on stilts in the swamp, covering the remains. The former dump is now an industrial area, with "Grandpappy" underneath.

Boeing XC-105 with engines and fuselage glazing covered for storage. 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.

Boeing XB-15: American Heavy Bomber