Boeing Model 299 (XB-17)

The Boeing Model 299, the “grandfather” of the Flying Fortress.

The Model 299 was the original bomber design built by Boeing to fulfill an August 1934 requirement by the United States Army Air Corps for a bomber capable of carrying 2,000 lb (907 kg) of bombs 2,000 mi (3,218 km) at 200 mph (322 km/h). The 299 was powered by four Pratt & Whitney S1EG Hornet radial engines rated at 750 horsepower (560 kW) each at 7,000 feet (2,100 m), giving a maximum speed of 236 miles per hour (380 km/h) and a maximum gross weight of 38,053 pounds (17,261 kg). It carried a bomb load of eight 600 pounds (270 kg) bombs, with a defensive armament of five .30 caliber machine guns, with one in a nose turret and one each in dorsal and ventral mounts and two in waist blisters. In 1935, Boeing's Model 299 competed with several entries by other aircraft companies at an evaluation at Wright Field near Dayton, Ohio, USA.

On its flight from Seattle, Washington to Wright Field for the competition, the 299 set a nonstop speed record of 252 mph (406 km/h). Though it crashed and burned on takeoff during a demonstration, the crash was due to flight-crew error, not from any flaw in the aircraft. Subsequent implementation of a mandatory pre-flight checklist prior to take-off ensured avoidance of flight crew error. Despite the crash (and more important, its much higher cost per unit), Army Air Corps leaders were impressed by the bomber's performance, so Boeing was awarded an initial development contract. The aircraft has since been referred to as the XB-17, but this designation is not contemporary or official.

Model 299 Press Release: Boeing Test Bomber, Model 299

Hailed as the fastest and longest range bomber ever built, a giant four-engined all-metal airplane, today was brought to light by the Boeing Aircraft Company of Seattle after more than a year of work on the project.

Known merely as the Boeing 299, the huge craft shortly will undergo test flights before being submitted to the United States Air Corps in open competition with other types at Dayton, Ohio. These tests, it was announced, are expected definitely to stamp the plane as the most formidable aerial defense weapon ever offered this country, with far more speed and a substantially greater cruising range than any bomber ever before produced.

Military secrecy necessarily shrouds many details of the Model 299. Boeing officials said, however, that it would meet or exceed specifications of the Air Corps as set forth in a public call for bids and equipment.

Among other things, these requirements are known to call for a high speed of from 200 to 250 miles an hour at 10,000 feet altitude, for an endurance at operating speed from six to ten hours, and for a service ceiling of from 20,000 to 25,000 feet.

The Boeing "aerial battle cruiser" has a wing span of approximately 100 feet, length of 70 feet, height of 15 feet, and gross weight of about fifteen tons. It is of the all-metal mid-wing type, equipped with four Hornet engines of over 700 horsepower each and with the new Hamilton Standard three-bladed constant speed propellers. Clean streamlining is a feature, with retractable landing gear and tail wheel as further aids to speed. Officials declare the plane to be the first military type which will be able to complete a mission in the event one engine ceases to function.

A number of new armament installations, developed by Boeing engineers, are carried in addition to the latest types of flight and engine instruments, including an automatic pilot, two-way radio telephone equipment and a radio "homing" device. Air brakes are used for the first time in any American aircraft, with these as well as the craft's wheels and tires having been especially developed.

Construction is of typical Boeing semi-monocoque type, the structure consisting of longerons, skin stiffeners, bulkheads and smooth outside metal skin.

The Model 299 makes its bow as the latest in a long line of Boeing achievements dating from 1916. Among these in recent years have been the company's high-speed twin-engined bomber of 1931 and commercial transport plane of 1933, both of which established the current trend in aircraft design and construction.

An entire fleet of the transports, known as the Model 247-type, today is operating on the routes of United Air Lines, Pennsylvania Airlines, National Park Airways, Western Air Express and Wyoming Air Service. In addition, single-seater Boeing fighters are regular equipment at Army Air Corps bases, at Navy shore stations and on Uncle Sam's aircraft carriers.

War Department - July 5, 1935

Model 299 Crash: Cause of the Crash of the Boeing Bomber

The findings of the Board of Officers convened at Wright Field, Dayton, Ohio, to investigate the cause of the crash on October 30, 1935, of the Boeing Aircraft Company Bombardment plane, model 299, were to the effect that the accident was not due to structural failure, or to the malfunctioning or failure of any of the four engines, the airplane control surfaces or the automatic pilot, but to the locked condition of the rudder and elevator surface controls (primarily the latter), which made it impossible for the pilot to control the airplane.

These findings were based on the locked condition of the controls after the crash; the testimony of Lieut. Donald Putt, co-pilot; of Mr. Leslie R. Tower, Boeing Aircraft Company test pilot, as to the behavior of the airplane in the air, and the testimony of eyewitnesses as to the behavior of the airplane on takeoff and flight.

From the evidence submitted the Board reached the conclusion that the elevator was locked in the first hole of the quadrant on the "up elevator" side when the airplane took off, for had the elevator been in either of the "down elevator" holes on the quadrant or the extreme "up elevator" hole, it would have been impossible for the airplane to be taken off in the former case, and in the latter case the pilot could not have gotten into the seat without first releasing the controls. With the elevator in this position they are inclined at an angle of 12.5 degrees.

During the take-off run the airplane could not assume an angle of attack greater than the landing angle of the airplane (7.5 degrees) plus the angle of incidence of the monoplane wing to the fuselage (3 degrees) or a total angle of 10.5 degrees. This would not be particularly noticeable to the pilot during the ground run.

However, as soon as the airplane left the ground, which several witnesses testified was in a tail low attitude, the elevators, with increasing power, varying as the square of the air speed (approximately 74 miles per hour at take-off), tended constantly to increase the angle of attack, until the stall was reached. The trim tab on the elevator also tended to aggravate this extreme tail heavy position, since with locked elevators, and the pilot pushing forward on the control column, the trim tabs were up, and themselves acted as small elevators on the fixed elevator proper.

Due to the size of the airplane and the inherent design of the control system, it is improbable that a pilot, taking off under these conditions, would discover that the controls were locked until too late to prevent a crash.

The locked condition of the controls was due either to the possibility that no effort was made to unlock the controls prior to take-off, and as a result the controls were fully locked; the possibility that the pilot only partially depressed the locking handle and as a result the locking pin was only partially withdrawn from its hole in the face of the locking quadrant; or the possibility that the locking handle was fully depressed prior to take-off and, due to the malfunctioning of the system, did not fully disengage the locking pin. There is no evidence to show that the system had ever malfunctioned, but due to the inherent design it must be considered a possibility.

15 November 1935 

The Model 299 (X13372 c/n 1963) began with a sleek looking shark fin tail and gun blisters on the fuselage. It wasn't until the E model that the tail was enlarged with a huge dorsal fin creating the classic look of the B-17 commonly recognized today.

Boeing 299.

Final ground check on the Boeing 299 before its record-making flight from Seattle to Dayton, Ohio, on 20 August 1935.

Model 299, registration NX13372.

Boeing 299 (X13372 c/n 1963), Seattle, Washington, July 28, 1935.

Boeing Model 299.

Boeing Model 299.

Boeing Model 299 (XB-17) cockpit.

Bombardier and front gunner’s stations on the Boeing Model 299, the B-17 prototype, 9 August 1935.

Boeing Model 299 nose turret with gun, 24 July 1935.

Bomb sight window on the nose of the Boeing Model 299, the B-17 prototype, 9 August 1935.

Blister gun turrets were installed in the waist of the 299. These permitted the air gunners to work protected from the 250 mile-per-hour wash of the propellers. Not accepted for production; production aircraft left gunners exposed to -50 F temperatures. 18 June 1935.

Internal view of “tear drop” shaped right waist turret on the Boeing Model 299, the B-17 prototype, 18 June 1935.

Radio station on the Boeing Model 299, the B-17 prototype, 9 August 1935.

The Boeing Model 299 in flight in 1935. Composite photo.

Few airplanes have ever been given such a complete test as those first Fortresses were put through.

Two Boeing P-26A test airplanes pose below the wings of the giant Boeing XB-17 (Model 299) Flying Fortress, July 1935.

The XB-17 (Model 299) crashed during its test flight at Wright Field on 30 October 1935. Test Pilot Major Ployer Peter Hill died as a result of injuries received from the crash. Co-Pilot Donald Putt survived.

Remains of the XB-17 (Model 299) following its crash due to an attempted takeoff with locked elevator controls. 30 October 1935.