Incident Overview

Date: Saturday 28 August 1976
Aircraft Type: Lockheed C-141A-LM Starlifter
Owner/operator: United States Air Force – USAF
Registration Number: 67-0006
Location: Peterborough – ÿ United Kingdom
Phase of Flight: En route
Status: Destroyed, written off
Casualties: Fatalities: 18 / Occupants: 18
Component Affected: Primary Radar SystemPrimary Radar System
Category: Accident
A Starlifter 67-0006 experienced a critical malfunction resulting in a significant loss of aircraft capability during an enroute flight. Initial radar checks revealed a history of previous maintenance issues, leading to a delayed and ultimately unsuccessful assessment. The crew, unaware of the prior problems, signed off the radar as ‘Ops Check Okay’ despite the ongoing operational failure. The aircraft subsequently entered severe weather conditions, including a rapidly intensifying thunderstorm system, and experienced a catastrophic failure of the primary radar, leading to navigational complications and a dangerous situation. The aircraft then entered a leading edge of a strong thunderstorm cell.A Starlifter 67-0006 experienced a critical malfunction resulting in a significant loss of aircraft capability during an enroute flight. Initial radar checks revealed a history of previous maintenance issues, leading to a delayed and ultimately unsuccessful assessment. The crew, unaware of the prior problems, signed off the radar as ‘Ops Check Okay’ despite the ongoing operational failure. The aircraft subsequently entered severe weather conditions, including a rapidly intensifying thunderstorm system, and experienced a catastrophic failure of the primary radar, leading to navigational complications and a dangerous situation. The aircraft then entered a leading edge of a strong thunderstorm cell.

Description

Starlifter 67-0006 had a recent history of weather radar problems. It had been written up by crew members eight times previously. On the day of the accident the maintenance crewman, unaware of the previous problems, checked the radar. It seemed to be working, so it was signed off as “Ops Check Okay”. Shortly after takeoff from McGuire AFB, the crew noticed that the radar was inoperative. Since severe weather was not forecast, they elected to continue to Mildenhall, UK. Two hours after takeoff, British forecasters issued a SIGMET for “Moderate to occasional severe clear air turbulence from FL240 to FL400”, but the crew never got this report. Four hours after takeoff the crew updates the weather forecast. They receive a weather forecast of “3/8 at 3000 feet, 4/8 at 4000 feet with an intermittent condition of wind 030/12 gusting 22, visibility five miles in thunderstorms, 2/8 at 2000 feet 5/8 at 2500 feet”. The crew then attempted to get an update one hour from Mildenhall, but was unable to contact the base. Another station reported “4/8 Thunderstorms tops to FL260”. During the enroute decent they entered the clouds. At FL150, they requested vectors around the weather. Because the primary radar was inoperative, the controller advised that he would have difficulty providing avoidance vectors. The aircraft then entered the leading edge of a very strong line of thunderstorm cells. One estimate indicated they encountered a 100 mph downward vertical airshaft. The right wing had failed, followed quickly by the upper half of the vertical stabilizer, and the four engines.

Primary Cause

Radar malfunction and subsequent failure of primary radar system.Radar malfunction and subsequent failure of primary radar system.

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