Convair 340/440 accident at Windsor Locks, Connecticut, 19 Oct 1962 (N-8415H)

Accident narrative

On October 19, 1962, Allegheny Airlines Flight 928, a Convair 340/440 (N 8415H), experienced an explosive decompression while descending toward Bradley Field in Windsor Locks, Connecticut. The rear service door blew open, ejecting a hostess from the aircraft to her death.

### The flight Flight 928 was a scheduled passenger flight from Washington, D.C., to Providence, Rhode Island, with en route stops at Philadelphia, Pennsylvania, and Bradley Field. The crew consisted of Captain Harold E. Gould, who had 14,450 flying hours including 1,800 in the Convair 340/440; First Officer Harold T. Hawkins, who had approximately 9,000 hours; and two hostesses.

The flight departed Washington on schedule. At Philadelphia, forty-eight passengers and the crew of four were aboard.

### The sequence of events After the right engine was started at Philadelphia, the crew noted that the passenger door and rear service door warning lights were on. A ramp agent climbed on a ground power unit and closed the rear service door from the outside. The second hostess informed the captain she was having trouble closing the passenger door, and the first officer left the cockpit to assist her. The captain stated that upon the first officer's return, all door warning lights indicated the doors were closed and locked. The ramp agent stated he could see from the outside that all red warning lights were out. The flight departed at 1955 on a VFR flight plan, and the cabin pressurization system was activated.

Approximately five minutes after takeoff, the first hostess informed the captain of a noise coming from the rear service door. The first officer stated that the door warning lights were still out. He accompanied the hostess to the rear of the cabin, where a high-pitched sound was audible. He checked the door handle and overhead latches, finding them in the locked position. He felt the bottom latches, which he stated felt locked, and dropped paper around the door to check for a leak but found none. He advised the captain that he could not find anything wrong but that noise was coming from around the rubber seal.

The captain instructed the first officer to attempt to stop the noise. The first hostess dampened several pillow covers and placed them on the rear side of the door over the visible rubber seal. This stopped the high-pitched noise.

The flight cruised at 5,500 feet. The captain stated that sea level cabin pressure was maintained for passenger comfort. Near the Trinity VOR, about 57 nautical miles from Bradley Field, light turbulence was encountered and the "fasten seat belt" sign was turned on. The sign was left on for the descent. The crew contacted Bradley Approach Control and was instructed to make a straight-in approach to runway 6. Weather was clear with visibility over 15 miles.

At approximately 2052, just after passing through 4,000 feet, an explosive decompression occurred. The service door warning light illuminated. The decompression blew the cockpit-cabin door approximately eight feet down the aisle and ripped the lavatory door from its hinges, forcing the second hostess to the floor. The first hostess, who was in the buffet area, was ejected through the blown-open rear service door and fell to her death. The aircraft made a priority landing at Bradley Field at 2058.

### What the investigation found Investigators found the lower edge of the rear service door twisted rearward and one foot away from the lower lock pins. The upper latching hooks were over the upper lock pins, but the hooks were twisted and bent outward. The door handle was in the "open" position.

The door warning system utilized plunger-type switches at the upper and lower forward lock pins. The Board found there was no indication in the warning system for the position of the two rear latching hooks.

The door was reinstalled for ground tests. Investigators found that when the door was slammed shut, the warning light would go out even if the lower aft hook was not fully engaged. With the door in this semi-latched configuration, the cabin was pressurized to a 2.1 psi differential. Engine vibration and pressure caused the door handle to progress slowly toward the "open" position, and it could not be manually locked. During normal depressurization, the handle moved further open until the door popped outward at the bottom.

The Board concluded that the closing procedure at Philadelphia resulted in an insecure engagement of the aft lower latching hook. This improper latching was not indicated by the warning light and would be difficult to detect visually. During the descent to Bradley Field, the decreasing pressure differential lessened the tension on the partially engaged hook against the lock pin. This allowed the lower portion of the door to be distorted by pressure, which, assisted by aircraft vibrations, caused the door handle to move to the fully open position and disengage the forward lower hook. At the time of the accident, the pressure differential was computed to be approximately 1.7 psi, exerting a total force on the door in excess of 3,000 pounds.

The investigation noted that Allegheny Airlines had recorded seven inadvertent in-flight rear service door openings on its Convair aircraft since April 1960, three of which involved N 8415H. Convair had issued service bulletins recommending door modifications since 1954, but the Board noted the majority of these were not incorporated in N 8415H.

The Board believed the crew erred in analyzing the leak as a door seal issue. Given the history of inadvertent service door openings experienced by Allegheny, the Board believed the crew should have depressurized the aircraft and warned the flight attendants and passengers to avoid the rear service door area. The airline's operations manual at the time required dumping pressure upon evidence of a door failure, but contained no specific instructions for an impending pressurization failure.

### Probable cause The Board determines that the probable cause of this accident was "an undetected insecure latching of the rear service door resulting in an inflight explosive decompression which ejected a hostess from the aircraft."

Contributing factors were "Allegheny Airlines' inadequate emergency pressurization instructions, and the continuation of pressurized flight after discovery of the pressurization leak."