Royal Air Force (No. 53 Squadron) Flight XH117

Royal Air Force (No. 53 Squadron) — Flight XH117

A Blackburn Beverley heavy transport aircraft crashed into the village of Sutton Wick while attempting an emergency return to RAF Abingdon, killing 18 occupants and two people on the ground. The accident was caused by fuel starvation to the port engines after a non-return valve was installed in reverse during maintenance. Shortly after takeoff, the crew shut down the No. 1 engine as a precaution; however, the No. 2 engine subsequently failed to respond to throttle inputs because the reversed valve blocked the fuel supply from the main port tank. The aircraft struck trees and cables before crashing into a farm and residential houses.

Aircraft

Blackburn Beverley C Mk 1

Registration

XH117

Phase

Cause

Souls on Board

Fatalities

Origin → Dest

RAF Abingdon, Berkshire, England → RAF Akrotiri, Cyprus

Report

Investigation Summary

The investigation revealed a critical maintenance error involving the fuel system's non-return valves. The Blackburn Beverley's fuel system for the port wing utilized a collector box fed by four tanks. A non-return valve located between the No. 1 port tank and the collector box had been fitted backwards. During the flight, the No. 1 engine was shut down as a precautionary measure. When the crew attempted to manage the remaining power, the No. 2 engine suffered fuel starvation because the reversed valve prevented fuel from reaching the collector box from the primary supply. Although two smaller fuel tanks were available, they were not selected during the flight. The Board of Inquiry determined that the captain likely believed the engines would operate correctly from the main tanks and had no reason to suspect a mechanical blockage. The technician who installed the valve was subsequently court-martialled for negligence.

Final Conclusions

The Board of Inquiry concluded the primary cause was fuel starvation resulting from the incorrect installation of a non-return valve in the fuel system. Secondary factors included the precautionary shutdown of the No. 1 engine and the fact that auxiliary fuel tanks, which might have provided a limited supply, were not selected. The investigation led to a significant redesign of aircraft components to prevent similar maintenance errors.

Video Analysis

No video analysis linked for this case file yet.

Airframe & Maintenance

Engines

Bristol Centaurus 173

Systems & Failure Modes

Fuel Non-Return Valve

A valve designed to allow fuel flow in only one direction; its reversed installation blocked the fuel supply to the port engines' collector box.

Bristol Centaurus 173 Engines

The aircraft was powered by four of these 18-cylinder radial engines; the two port engines (No. 1 and No. 2) lost power during the accident sequence.

Interesting Facts

01The aircraft was carrying members of 47 and 53 Squadrons, RAF Police, and Military Working Dogs.
02A non-return valve in the fuel system was found to have been installed in reverse.
03The crash resulted in 20 total fatalities: 15 passengers, 3 crew members, and 2 civilians on the ground.
04Four occupants survived the crash: two crew members and two passengers.
05The technician responsible for the valve installation was reprimanded following a court-martial.
06The aircraft was only one year old, having been manufactured in 1956.

Safety Actions & Advisories

Valve Redesign

The non-return valve was redesigned with different thread sizes at each end to make incorrect installation physically impossible.

Airworthiness Design Standards Update

Design standards were changed to ensure that similar critical components cannot be assembled in the wrong orientation (Poka-yoke principle).

Location

Sutton Wick, Drayton, Berkshire, England · 51.6400, -1.3200