Aviation safety investigations & reports

Kawasaki BK117-A4, VH-PHF, Balmoral Beach, Sydney NSW, 15 January 1988

Investigation number:
Status: Completed
Investigation completed


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The helicopter crew was responding to an emergency call. The aircraft was cruising at 1500 feet above sea level, at about 120 knots, with maximum continuous power applied. As descent was commenced there was a loud bang, followed by severe vibration. The helicopter was briefly out of control and the vibrations were such that the pilot was unable to read the instruments. Power and speed were reduced and the pilot was able to regain control. Because of expected difficulties with control near the ground, the pilot elected to carry out a water landing, some 80 metres from a beach. A subsequent investigation determined that the left engine access cowl had become unlatched, lifted and been struck by the main rotor blades. The hinged section had been struck at least twice and the upper fixed cowl, which had been torn from its fastenings when the hinged cowl lifted, at least once. Apart from minor impact marks to other main rotor blades, a piece of cowling had slid along one blade, causing 2.1 metres of the outboard trailing edge to separate, resulting in severe unbalance to the rotor disc. The pieces of engine cowling and main rotor blade were found approximately two kilometres south of the accident site. As two lower main cowl latches were not recovered, the reason for the cowl becoming unlatched could not be positively determined. However, during the investigation, it was found that the lower cowl latches, which appeared to be correctly locked and engaged, could release when the cowl was subjected to simulated inflight loads. The manufacturer has suggested modifications to improve the cowl latching system.


It is recommended that the Civil Aviation Authority evaluate the suggested modifications and, if satisfactory, direct their incorporation in Australian registered Kawasaki BK117 aircraft.

Download Final Report
[Download  PDF: 23KB]
General details
Date: 15 January 1988   Investigation status: Completed  
Time: 739    
Location: Balmoral Beach, Sydney    
State: New South Wales    
Release date: 18 October 1988   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Kawasaki Heavy Industries  
Aircraft model BK117  
Aircraft registration VH-PHF  
Serial number 1014  
Type of operation Aerial Work  
Damage to aircraft Substantial  
Departure point Mascot NSW  
Departure time 0734  
Destination Curl Curl Beach NSW