1959 Washington Boeing 707 crash. On October 19, 1959, N7071, a Boeing 707, was on a demonstration and acceptance flight before being delivered to Braniff International Airways. The flight was also used to instruct the Braniff pilots. During aerodynamic maneuvers control was lost, causing the forces to rip three engines off. The plane crash landed, killing all four crew, and leaving four survivors.

Background

Aircraft 
The aircraft involved was a Boeing 707-227 registered as N7071 with serial number 17691. It was manufactured on June 11, 1959. It was operated by Boeing and it had accumulated 173 flight hours.

Crew 
Russel Baum, aged 32, was a Boeing test pilot with 5,015 flight hours. Captain John Berke, aged 49, was employed by Braniff International Airways and had logged 23,563 flight hours. Captain Frank Staley Jr., age 43, was employed by Braniff International Airways and had accumulated 20,450 flight hours. Flight Engineer Carl Hagan, aged 28, was employed by Boeing and had accumulated 1,260 flight hours. Baum served as instructor for Captains Berke and Staley, who were on their first training flight on the 707.

Flight 

The aircraft took off from Boeing Field at around 13:30 local time for a flight expected to last 4 hours and 15 minutes. Captain Berke was in the left seat, with Baum occupying the right seat. After takeoff a series of maneuvers were demonstrated by Baum after which Captain Berke executed them himself. One of these maneuvers was the dutch roll which Baum initiated and Captain Berke then made recoveries from. After doing recoveries in a clean configuration (no flaps or landing gear extended), the aircraft was slowed to 155 knots and flaps were extended to 40 degrees. Even though the absolute maximum bank angle permitted during the dutch roll was 25 degrees, the bank exceeded this limitation. An engineer riding as a passenger reminded Baum of these restrictions, which he acknowledged.

Baum suggested that he and Captain Berke switch seats. He then initiated a dutch roll with a bank angle of 40 to 60 degrees. The aircraft completed several of these rolls before recovery was attempted. Captain Berke banked to the right just as the aircraft was already banking to the right. The aircraft yawed to the right and the bank angle increased past 90 degrees. Baum used left aileron to induce a violent left roll. The aircraft spun around several times to the left, before the spinning settled as the plane was in an inverted position. The crew managed to recover from the dive, however engines Nos. 1 and 4 had detached completely with small fires burning where the engines had been. Engine No. 2 was on fire and hanging downwards due to its forward mount failing. Shortly the engine detached completely, however the intense fire remained on the wing.

The aircraft had broken through the clouds and Baum circled next to Lake Cavanaugh. The four passengers, who had been in the cockpit during the accident, went back into the rear cabin. Engine No. 3 alone would have been enough to reach an airport, however, the fire raging in the left wing destroyed the left inboard aileron and disabled the outboard ailerons. Additionally, the loss of power caused by the loss of three engines disabled the inboard spoilers and the rudder boost, leaving only the right inboard aileron and outboard spoilers. Fire damage on the wing reduced its lift, leading to a rolling momentum. This roll could be countered by reducing power on engine No. 3. Before impact engine No. 3 was shut down. Eyewitnesses reported that large portions of the left winged had burned away.

The crew elected to land in an open pasture, however they didn't have enough altitude and the plane hit treetops at an altitude of 110 feet. A 16 foot long portion of the left wing was torn off after hitting a tree. The left wing dropped and hit the ground, followed by the nose section, which was destroyed by the impact and ensuing fire, killing all 4 crew inside. The aft section detached aft of the wings and came to rest in the Stillaguamish River.

Investigation 
The accident was investigated by the Civil Aeronautics Board. They determined that the accident was a result of the instructor pilot performing a dutch roll far too extreme. There was no valid reason for him to do this as it didn't benefit the training. It is not hard to see why Captain Berke, a pilot completely new to the 707, was unable to recover.

The CAB determined that the probable cause of this accident was:

As a result of the accident several changed to the 707 were made, including the increasing of the vertical stabilizer area and made the rudder full-time boosted. These changes made the aircraft more stable and easier to control.

References 

Accidents and incidents involving the Boeing 707
Aviation accidents and incidents in the United States in 1959
Aviation accidents and incidents in Washington (state)
October 1959