On March 18, 1939, a Boeing S-307 Stratoliner prototype departs Boeing Field in Seattle for a flight to test the ship's stability. During maneuvers, the aircraft unintentionally stalls, goes into a flat spin and crashes into a ravine near Alder, a former logging town in Pierce County, 40 miles southeast of Tacoma. The crew of 10, on board to navigate, monitor and evaluate the flight, is killed in the mishap. The Civil Aeronautics Authority, Air Safety Board will conclude that the cause of the accident had been the structural failure of the wings and horizontal stabilizers during the recovery from a steep dive.
A Sudden Stall
The Boeing S-307 Stratoliner, manufactured by the Boeing Aircraft Company in Seattle, was developed in the late 1930s and was the world's first four-engine, high-altitude, commercial transport. Its main innovation was a pressurized cabin, allowing the airplane to fly above inclement weather at an altitude up to 23,300 feet. The ship was 74.3 feet long, 12 feet wide, with a wingspan of 107 feet, and powered by four supercharged, 1,220 hp, Wright R-1820 Cyclone radial engines. At a cruising speed of 215 mph, the Stratoliner had a maximum range of 1,750 miles. The crew consisted of two pilots, one flight engineer, and two flight attendants. Its carrying capacity was 38 passengers in daytime flights and 25 at night, due to the substitution of some sleeping compartments for seats.
At 12:57 p.m. on Saturday, March 18, 1939, the first Boeing S-307 Stratoliner, registration number NX-19901, departed Boeing Field (now Seattle-Boeing Field International Airport) on its 19th flight with planned maneuvers over sparsely populated timberlands, southwest of Tacoma in Pierce County. In addition to the two test pilots, five Boeing officials, two observers from the Netherlands, representing the Dutch Air Ministry and Royal Dutch Airlines (KLM), and one observer from Trans World Airlines (TWA), were aboard to monitor and evaluate the demonstration. According to the flight plan, the aircraft was to climb to an altitude of 11,00 feet, where longitudinal stability and side-slip tests were scheduled to be made.
As witnessed by numerous observers on the ground, at 1:17 a.m., the Stratoliner suddenly stalled and went into a flat spin, making two to three gyrations. During pullout from the dive, the outer sections of the wings, left outboard engine, left horizontal stabilizer and elevator, and majors portion of the tail fin and rudder detached from the aircraft and fell to the ground. Minus lift, the aircraft fell directly into a logged-off ravine less than a quarter mile from the logging town of Alder. Pieces of the Stratoliner were found hundreds of feet away from the point of impact. Although its tanks carried some 3,000 gallons of aviation fuel, there was no explosion or fire.
Arthur A. Jacobson (1917-1997), Justice of the Peace at Alder, immediately notified the National Park Service at Longmire on Mount Rainier, informing the rangers of the disaster. An ambulance from the station arrived at the site within 15 minutes with a doctor, followed by three more ambulances from Tacoma, but there was nothing that anyone could do. The crash site was close to the Tacoma-Mount Rainier Highway (now National Park Highway) and hundreds of curious motorists flooded into the area to view the wrecked aircraft. Soon afterward, a cadre of Washington State Patrolmen arrived to disperse the crowds of onlookers and guard the integrity of the site for officials from the Civil Aeronautics Authority (CAA) and the Boeing Company.
Investigating a Disaster
On Sunday, March 19, 1939, 10 special investigators from the CAA, Air Safety Board arrived at Boeing Field and went directly to the crash site to examine the ruins in situ. The bodies of the crew had been removed to the Pierce County Morgue the previous day, leaving the safety board investigators and project engineers from Boeing free to carry out their examination. After all the debris had been identified, photographed and mapped, the Boeing Company ferried in assembly workers to dismantle the wrecked Stratoliner, which took several days to accomplish. Pieces of the aircraft were lifted by crane onto flatbed trailers which were then conveyed to a hangar at Boeing Field for comprehensive analysis.
The Stratoliner had plummeted some 3,000 feet and landed on the ground in an nearly level attitude. The fuselage was remarkably intact considering the tremendous force of impact. The flight instruments in the cockpit were complete, showing readings at the moment of contact. The instruments of the era weren't capable of recording flight history, but nevertheless did provide the investigators with important information.
On Wednesday afternoon, March 22, 1939, a joint funeral service was held for the 10 victims of the mishap at the Masonic Temple at E Pine Street and Harvard Avenue in Seattle. Production at the Boeing Company was halted at 11:30 a.m. so that coworkers could attend the ceremony. Afterward, the coffins of the Boeing employees were taken to various mortuaries in the Seattle area for private funerals and interment or cremation. The remains of the representatives from the Netherlands, Albert G. Von Baumhauer and Pieter Guilonard, were returned to Amsterdam for burial. The body of Harlan A. Hull, chief pilot for Trans World Airlines (TWA), onboard as an observer, was sent to his family in Kansas City, Missouri, for burial there.
On Thursday, June 1, 1939, the Air Safety Board delivered a 62-page report to the CAA in Washington D.C., detailing the results of its comprehensive investigation. The investigators concluded the probable cause of the accident was the "structural failure of the wings and horizontal tail surfaces due to the imposition of loads thereon in excess of those for which they were designed, the failure occurring in an abrupt pullout from a dive following recovery from an inadvertent spin" ("Crash of a Boeing 307 Stratoliner Near Alder: 10 Killed").
What had happened to the Stratoliner was abundantly clear, but why the ship had inadvertently stalled with such a disastrous result was open to speculation. The safety board's report listed eight potential factors that could have contributed to the fatal accident. First on the list was the assignment of the pilot in command, Julius A. Barr. His flight records showed that he had limited experience in testing and demonstrating this type of aircraft, particularly with respect to the maneuvers planned for this specific flight. Second, Alfred Von Baumhauer, onboard as an observer, had been found in the cockpit, occupying the copilot's seat. He was licensed as a private pilot by the Dutch Air Ministry and had no experience in flying four-engine aircraft. Nevertheless, he had been allowed to serve as copilot during various maneuvers being conducted at his request. The six other factors dealt with possible mechanical or procedural issues.
The Boeing Company produced only 10 Model S-307 Stratoliners. The first ship was destroyed in 1939 during flight testing. Five Stratoliners were purchased by TWA, three by Pan American Airways (PAA), and one heavily modified version by Howard R. Hughes (1905-1976), owner of TWA. The only surviving Stratoliner, originally flown by PAA as the Clipper Flying Cloud (registration number NC-19903), was fully restored between 1994 and 2001 in Seattle by a team of Boeing employees and volunteers. It is now on display at the Smithsonian National Air and Space Museum hangar at Dulles International Airport in Washington D.C.
Julius Augustus Barr (1906-1939), Boeing test pilot
Albert G. Von Baumhauer (1891-1939), Dutch Air Ministry aeronautical engineer
Ralph L. Cram (1906-1939), Boeing chief aeronautical engineer
William C. Doyle (1911-1939), Boeing aeronautical engineer
Earl A. Ferguson (1908-1939), Boeing chief test pilot
Pieter Guilonard (1896-1939), KLM general manager/technical director
Harlan A. Hull (1906-1939), TWA chief pilot
John Kylstra (1896-1939), Boeing aeronautical engineer
Benjamin J. Pearson (1906-1939), Boeing product sales manager/pilot
Harry T. West, Jr. (1903-1939), Boeing flight engineer