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Life rafts 
 
by: Sven Scheffers
Introduction
To provide protection for survivors, all aircraft flying over the sea normally carry sufficient liferafts for the crew and passengers. Several types of liferaft are used and the type title is synonymous with the number of people the liferaft is designed to carry. For example the type SS is a single seat liferaft and the type MS 26 is a multiseat liferaft designed to carry 26 people. All liferafts are designed with 50% 'reserve' buoyancy which permits a considerable overload. This chapter aims briefly to describe various types of liferaft.

Single Seat Liferafts
The single seat liferaft is always fitted in a personal survival pack. The type of personal survival pack will depend on the aircraft in which it is fitted, and in most cases it forms part of the seat of the aircraft. There are several marks of single seat liferaft currently available. In general they are similar and vary only in detail.

SS Mk 15 Liferaft
The buoyancy chamber is inflated from a carbon dioxide cylinder operated by a lanyard. Should further inflation be required, it may be done via an inflation point on the buoyancy chamber adjacent to the occupant's left thigh. The floor consists of a double layer of quilted fabric which can be orally inflated by a tube located at the occupant's right hip to provide insulation between the survivor and the sea. The canopy is also double skinned and quilted. This may be inflated by means of a tube and valve situated near the occupant's right shoulder. The canopy incorporates a hood and visor which can be pulled over the head and face. The buoyancy chamber and floor of the SS Mk 15 are black or dark grey in color and the canopy fluorescent flame orange. The single seat liferaft is attached to the survivor by a lanyard connected to the life preserver. This connection should not be released until a rescue ship or helicopter has secured the survivor.


a single seat liferaft

Multi-seat liferafts
Various types of multi-seat liferaft are currently in use. Among them are types designated as MS 5, MS 10, MS 26 and MS 33. The exact location and stowage medium of the liferaft(s) in an aircraft will depend on the aircraft type. No liferaft installation is considered to be satisfactory if the liferaft cannot be released, launched and inflated by one man. To make this possible some mechanical assistance may be provided to relieve the operator of some or all of the bulk and weight of the liferaft installation. The MS 10 is considered to be the largest liferaft which can be lifted by one person.

Blow Out Stowage
Blow out systems for multi-seat liferafts are provided in some aircraft. In these aircraft, the liferafts and survival aids are stored in panniers in compartments integral with the aircraft wing or engine nacelle. The system is operated by pulling an operating handle in the aircraft, the liferaft compartment cover lifts off, closely followed by. the inflating liferaft. If the interior handle fails to initiate the release sequence, an alternative control close to, or within, the stowage compartment can be used to release the liferaft.

Valise Stowage
In aircraft not fitted with blow out stowage facilities the liferaft is carried inside the fuselage. In these cases the liferaft may be packed into a valise. The valise is a canvas bag with webbing handles and is held closed by a lace. Should it be necessary to use the liferaft, a nylon line from the valise is connected to an aircraft strong point and the valise is thrown into the sea.

The nylon line is attached to the liferaft and to the inflation cylinder. When the line is pulled, the liferaft inflates and bursts out of the valise by breaking the lace.

Container Stowage
Container Stowage is a development of the valise stowage method. The containers are made from rigid plastic material and shaped to suit the requirements of particular aircraft. Some containers are disc shaped and therefore may be easily rolled from their stowage position to emergency exit. The liferaft in a container is inflated by a method similar to that employed on a liferaft stowed in a valise.

Design
The design characteristics of all multi-seat liferafts are similar although individual types vary in detail. They are normally inflated from carbon dioxide filled cylinders operated by a lanyard. The canopy is held up by inflatable pillars and is fitted with rainwater catchments areas. The liferaft floor and canopy are double skinned to provide thermal insulation but only the floor can be inflated by means of the bellows via one or more inflation points. All multi-seat liferafts except the MS 5 are fitted with two entrances and inflatable ramps to assist boarding. Water pockets under the liferaft provide improved stability in rough sea conditions.

MS 26 Liferaft
The picture below shows an MS 26 multiseat life raft. A central inflated pillar rises from the floor to support a double layered canopy. The two doors of the liferaft have double closure panels. In addition to the doors there are two observation apertures in the canopy, at right angles to the doors. These apertures can be closed with sleeves which are not inflatable. The canopy has rainwater catchment ducts on the sides, terminating in tubes inside, the liferaft.


MS26 multi seat liferaft

 

"Venz" /  "Hud"  flightgear on-line 2002/2003