Beechcraft Queen Air A65-A2, VH-CLG, Adelaide Airport, South Australia, on 2 October 1989

Circumstances:

The aircraft engines performed normally during the run up, taxi and take-off. At approximately 500 feet after take-off, the pilot noticed the right hand engine manifold pressure gauge indication slowly decreasing. Thinking that the throttle friction may have slipped, he advanced the right hand throttle. There was a momentary pause in the decreasing manifold pressure reading. The right hand throttle was gradually advanced to the full power position, however, manifold pressure continued to decay. Following completion of the trouble checks the pilot shut down the right hand engine and feathered the propeller. Because the flight was only a six minute positioning flight, for maintenance purposes and the aircraft was performing to his satisfaction on one engine, the pilot elected to continue to Parafield. He advised air traffic services of the engine failure and of his intention to proceed to Parafield. The aircraft subsequently made an uneventful single engine landing. At the end of the landing roll the pilot who was wearing a headset, heard the fire warning bell. At the same time, he noticed for the first time that the right hand engine bay fire warning light was illuminated. A post-flight inspection revealed substantial fire damage within the right hand engine bay forward of the firewall and a large section of the number four cylinder head was found lying in the lower cowling. The cylinder head had failed at the threaded joint of the head and barrel. Metallurgical examination showed that the fatigue failure had developed over a period of approximately 900 start/stop cycles. However, the development of the crack would probably have been visible to external inspection only during the latter 15 start/stop cycles prior to failure. The failure was probably the result of defective cylinder maintenance and assembly techniques and heat treatment used during overhaul. The engine fire had developed in the vicinity of the failed cylinder and spread throughout the engine bay fed by raw fuel through the cracked cylinder head and burnt fuel lines. It is likely that the fire self-extinguished when the pilot turned the electric fuel pump off and shut the engine down. The engine bay fire warning system apparently activated and because it had not been detected by the pilot, remained activated until after the landing. The warning system did not self-cancel after the fire abated. The aural warning system was found to be inaudible at high power settings and due to the ambient light conditions prevailing during the take-off into bright sun and glare, the steady red fire warning light was not noticed by the pilot. Approved check lists did not include a check of the fire warning system as part of the emergency procedures cockpit drill.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. Defective techniques used during cylinder assembly maintenance and inspection.

2. Cockpit visual fire warning system for the engine bay operated but was not evident to the pilot under the ambient light conditions.

3. Aural fire warning could not be heard at high power setting.

4. Aural fire warning bell was not connected to audio system.

5. Aircraft emergency procedures check list did not specify pilot monitoring of fire system following engine failure.

Recommendations:

1. That the Civil Aviation Authority give consideration to: Improving surveillance of maintenance organisations where cylinder heads and barrels are separated by heat treatment with particular emphasis on:

a) techniques used in the control of heat processes during strip down and reassembly procedures such that temperatures attained do not cause softening of the alloy, and

b) reminding maintenance personnel of the necessity to maintain due care during the disassembly and reassembly stages of cylinder overhauls where heating is required, and

c) achievement of sound inspection techniques and practices.

2. Ensuring that general aviation aircraft equipped with on-board fire detection and extinguisher systems are able to provide the pilot with such vital information concerning an in-flight engine fire by:

a) changing any steady fire warning light/s to a flashing red indication;

b) ensuring that such red fire warning light/s are ergonomically placed in the pilot field of vision to permit immediate recognition of activation;

c) ensuring that where an aural fire warning system is incorporated, the minimum volume be adjusted such that it be audible under all power settings with and without noise suppressing headsets;

d) conducting a study of the feasibility of incorporating an aural fire warning alarm for reproduction through the cockpit audio system; and

e) amending emergency procedure check lists to incorporate a check of the fire alarm system where fitted.