Incident Report: BCal BAC 1-11 G-AWYS
19th July 1972 Continued
The Take-off Run - continued
Yankee Sierra overran the rough ground at the end of the runway at a relatively low speed and came to rest in shallow sea water in the lagoon. The water was about 1 metre deep and came up to the fuselage.
She came to a rest gently which helped considering she crossed into water and no injuries were sustained on board the aircraft
Below is a photo of the incident
The investigation looked into all aspects of the flight.
The load sheet was compiled by Olympic Airways and found to be accurate
The operation of the aircaft was found to be normal, and the crew had taken cognisance of the weather, runway conditions, weights and performed all preflight checks. The correct paperwork and manuals were onboard and the aircraft was correctly certificated, registered and maintained.
The Flight recorder was recovered intact and without damage. It was returned to the UK for examination and processing.
A number of tests were undertaken at Gatwick on a sister aircraft of AWYS. The Flight recorder was placed in another 1-11 series 500 to establish the characteristics of the brake release (as it was hard to determine on AWYS due to immersion) and also if AC voltage supply frequency could be used as an indication of engine speed changes. All tests were undertaken by British Caledonian crews with BAC (Weybridge) staff in attendance.
They confirmed that large changes in engine speed result in changes in AC supply voltage frequency and that braking release was as expected.
Both engines were inspected on site and found to have sustained minor damage. Both engines were returned for testing and examination by Rolls Royce in the presence of an Air Accident Investigation Branch inspector.
Both engines were found to have sustained damage from ingestion of sea water. Reverse thrust was not cancelled until YS had come to rest in the lagoon. Both engines were found to have ingested hard-body elements, this was from the gravel / shingle at the end of the runway, this added to the evidence that both engines were still turning as the damage to both was nearly identical.
They did find a jammed ACU (acceleration control unit) push rod, though this is not used when the engine RPM is high enough, over 10,000RPM as the engine speed overtakes the need for controlled fuel on power up.
Below a chart derived from the data recorded.
The aircraft evacuation proceeded in an orderly manner via the overwing exits and the port wing. Small boats were quickly on the scene and passengers were taken back to shore.
Kerkyra Airport had two fire engines at the time and they were both dispatched to the scene and their crews helped the passengers to shore.
Yankee Sierra was recorded as substantially damaged in the accident.
Though she had come to rest gently, she was in soft mud and it took six days to complete her salvage. On inspection she was found to have sustained damage to some fuselage structural members as well as from salt water corrosion. Her undercarriage had remained intact and held her out of the water or it may have been a full hull loss.
The boundary fence was recorded has having sustained some damage.
The report found that both engines were functioning, though there had been a fall off in power coincidental with running through the pools of standing water around the mid point of the runway.
With the engine igniters on the engine should have re-ignited if it became flooded with the water thrown up from the pools on the runway. Though it would be possible for the engine to loose power and if the engine spooled down to below 10,000 RPM the seized ACU push rod may have hampered the engine's recovery.
Though by the time take off was abandoned the engine was accelerating back up and was at or near full power. Though this all took place in seconds (3 - 8 seconds) and with the aircraft very close to decision time.
The pulling to the left was undoubtedly the result of the pool of water on the left and the partial loss of power on that side, hence needing right rudder to control her take off course.
The investigation team found that YS needed just 160 feet to come to a stop on the runway, and this equated to 3 seconds at the speed they were travelling at.
G-AWYS was repaired and stayed in service with BCal until April 1988 and then with BA until 1993.
While YS was under repair a replacement BAC 1-11 was needed to see out the summer seasons schedule; and G-AZPE was leased from BAC from 14th August - 18th October 1972.
More information and photos follow on