On May 11, 1985, a Boeing B767-232 (registration N108DL) was involved in an aviation accident near D/fw Airport, TX. Investigators recorded the probable cause as: Malfunction of the pressure regulator and shutoff valve coupled with the high pressure shutoff valve, resulting in excessive pressure in the downstream ducting. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A B767 experienced a duct failure during takeoff roll after a pressure regulator and shutoff valve malfunction led to pressures exceeding 300 psig, causing extensive damage to ducting and aircraft systems.
Event Description
During the takeoff roll of a B767, a malfunction occurred involving the pressure regulator and shutoff valve coupled with the high pressure shutoff valve. This malfunction resulted in pressures exceeding 300 psig in the downstream aircraft ducting. The excessive pressure caused a coupling in the air conditioning pack bay to separate, leading to the ducting coming apart with sufficient force to damage surrounding components.
Damage
The duct failure tore loose duct supports, cracked fairing panels, and severed both right engine throttle cables. Additionally, the actuating linkage for the leading edge slat drive was broken, and the right pack bay door was blown open. A section of ducting containing the center isolation valve departed from the aircraft. Minor damage occurred to the aircraft structure.
Probable cause
Malfunction of the pressure regulator and shutoff valve coupled with the high pressure shutoff valve, resulting in excessive pressure in the downstream ducting.
