The Problem With The Boeing 727’s Rear Door

The Boeing 727’s rear door, or otherwise described as the rear ventral airstair, could be opened mid-flight. Unlike other doors on the 727, there was no mechanical preventative stopping the rear door being opened while in flight and, say, a passenger jumping from the plane. This very scenario famously occurred with the D.B. Cooper Hijacking back in 1971.

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The rear stairs of the Boeing 727. Photo: Piergiuliano Chesi via Wikimedia

The problem with the 727 rear door

The Boeing 727 features a rear staircase that deploys under the tail of the aircraft. Airlines would use it when an aircraft would park at a remote ramp or when a stair car was not available. In the early days of jet aircraft, many planes were low enough that stairs were a useful addition to a plane.

However, the one flaw of the stairs were that they could open while the aircraft was in flight. Because the stairs were to the rear of the plane, the door could open without fighting against the wind.

In 1971, a robber boarded a Northwest Orient Airlines Boeing 727 with the pseudonym Dan Cooper and hijacked the aircraft between Portland and Seattle. Upon landing, he received his demands – $200,000 ($1.26 million today) and four parachutes. He then instructed the aircraft to fly towards Mexico City, via Reno (for refueling).

Approximately midway into the second journey, the pilots noticed that the aft door was open and that the criminal had jumped from the aircraft. The money and the man never reappeared, although some believe that he died during the parachuting attempt.

Following the event, North America experienced thirty-one hijackings, nineteen of which used precisely the same method. The criminal would ask for a parachute and money and intend to jump from the plane in flight.

A Northwest Orient Airlines Boeing 727. Photo: Jon Proctor via Wikimedia

How was it fixed?

In 1972, the FAA decided that something needed to change to prevent more copycat hijacking attempts. They mandated that a new mechanical component would be to be added to the door to prevent it from being opened in flight.

This new component was called the Cooper Vane (after the famous robber).

cooper vane
The small Cooper Vane. Photo: Tank67 via Wikimedia

The way it works is with a small weather vane attached to a spring-loaded paddle. When the plane is stationary at the gate or on the tarmac, there is no wind; therefore, the paddle remains deployed. When its deployed perpendicular to the fuselage, the stairs can be raised or lowered.

When the aircraft takes off, the paddle is forced back by the wind and then covers the stairs. The stairs can’t wedge past the paddle and thus cannot open. A surprisingly effective low tech solution.

While we can commend the work done by Boeing to update its aircraft line (And McDonnell Douglas, who also updated the DC-9 aircraft that had rear stairs) with Cooper vanes, in the end, airlines simply just moved away from using the stairs.

Either airlines sealed the stairs on the Boeing 727 or simply phased out the aircraft. Rear stairs onboard aircraft are massive and another item that may break down, so Boeing designed future aircraft without them.

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