Ditched helicopter study
Keywords BMT Fluid Mechanics, Helicopters, Safety, Testing
BMT Fluid Mechanics regularly performs consultancy and testing in support of the safety of helicopter offshore operations. This ranges widely from wind generated turbulence issues when operating to helidecks on offshore platforms or warships, through to the stability of helicopters after they have ditched in the sea.
Most recently, BMT Fluid Mechanics has performed a series of hydrodynamic model tests on a ditched helicopter for the Safety Regulation Group of the Civil Aviation Authority (CAA) (Plate 1).
Plate 1 1:10 scale model of EH101 helicopter in waves prior to capsize
When floating on the surface of the sea following an enforced "ditching",helicopters are top-heavy because of the location of the engines and gearbox on top of the cabin. Consequently, if they are hit by a large breaking wave, they generally capsize into a completely inverted attitude (Plate 2).
Plate 2 Following capsize, the auxiliary flotation system prevents complete inversion and keeps doors and windows on one side above water
Once inverted, all the doors and windows are usually submerged, and escape from the cabin becomes very hazardous. The ditching research project, which was carried out in collaboration with the Haslar Hydrodynamic Test Centre and GKN Westland Helicopters Limited, was aimed at testing the effectiveness of some auxiliary emergency flotation devices intended to prevent a capsized helicopter from turning into a completely inverted attitude.
A team of specialists from BMT and GKN Westland Helicopters first devised a total of ten potential flotation systems intended to prevent the total inversion of the helicopter. Following a detailed review of the likely effectiveness,practicability and safety, these ten systems were eventually narrowed down to a short-list of three systems. These three flotation systems were model tested,and two came through these tests with flying colours.
The project was therefore successful in identifying two practical additional flotation devices which it is hoped will be developed further by the industry,and eventually installed on helicopters working on over-water routes. BMT Fluid Mechanics has prepared a complete report on the project, which will soon be published by the CAA.
Details available from: BMT Fluid Mechanics. Tel: +44 (0)181 943 5544; Fax:+44 (0)181 943 4434; e-mail: enquires@bmtfm.demon.co.uk;Web site: www.bmt.org
