D.P. Smith

Large quantities of combustibles are contained in the cargo compartments of civil aircraft, thereby presenting a significant fire hazard. In order to control such fires in relatively large Class C cargo bays, Halons are usually deployed. As a result of the Montreal Protocol and its later amendments, however, the production of Halons is to be discontinued by the year 2000, if not sooner, and so more environmentally friendly means of fire control should be evaluated as a matter of urgency.

The objective of this latest study, commissioned and funded by the CAA, was to determine the feasibility of using fine water spray for the control of fires in a simulated Class C cargo compartment of internal volume 28 m3. The combustible fire load was a 10% fill of cardboard boxes containing assorted rags; in most of the tests, concrete blocks were added as inert fire load, bringing the total fill to 50%.

For the three hour duration of the tests, temperatures were measured at 15 locations within or on the surface of the test chamber. Concentrations of the gases CO, CO2 and °2 were monitored continuously, with the detection of other gaseous species being determined using 'grab' samples taken at suitable time intervals and analyzed by infrared spectrometry and gas chromatography. Measurements were also taken of infrared radiation, chamber pressure and smoke obscuration. In addition, video recordings were made of all the tests.

The unsprayed event for a 50% total fill was characterized by a series of significant but short-lived temperature excursions due to the onset of flaming combustion which appear to be oxygen-concentration controlled. These fires were found to be generally reproducible and c°!-Tip arable in severity to those generated during earlier trials in 1987 involving the control of Class C and D cargo bay fires by Halon 1301. For 10% total fill fires, temperature profiles were more even, although average temperatures were similar to the 50% fill case.

I During the experimental programmed, four types of water spray nozzle were employed in a variety of temporal regimes. A single operation system in which the spray was discharged for 10 minutes only was relatively ineffective in controlling the fire under the defined spray conditions. More successful were so-called 'pulsed' sprays in which an initial discharge was followed by a series of relatively short discharges at regular intervals throughout the test. In these cases, there was generally good correlation between the degree of fire control and the I total quantity of water consumed. 'Reactive' sprays were initiated when a designated threshold temperature, Tr' was reached and these systems were (bund to maintain temperatures at or below the assigned value of Tr; the higher the Tr' the less water was required for successful fire control. Two types of continuous spray were also demonstrated to be effective. The first was a sustained low flow fine spray, while the second was a twin spray system comprising an initial higher flow spray followed by a continuous lower flow fine mist.

In conclusion, water sprays, when suitably deployed have been found to offer comparable control of a fire load that simulates 'loose fill' cargo in a Class C cargo bay to that provided by Halon 1301 systems.

The amount of water required will depend on the defined safety criteria. In common with Halon 1301, however, water spray is unable to extinguish fully the deep-seated fires encountered in this study.

Aim Aviation Ltd

As a result of research conducted in the UK and USA the original concept of a Cabin Water Spray System in which water was sprayed throughout the entire length of the cabin has been radically altered.

This report analyses the possible costs of a reduced weight Cabin Water Spray System installation into three typical sizes of civil aircraft. To this end a theoretical design concept was established to which all costs could be related.

This report addresses the design costs, equipment costs, installation costs, maintenance costs and direct operating costs of such a system.

Allan Abramowitz, Franklin Fann

Fire tests were conducted on a quarter-scale model of an aircraft cabin to determine ventilation effects on temperature and smoke. The ventilation rates were varied between 1 1/4 and 2 1/2 minutes' time for an air exchange (quarter scale). 'The data indicate that there were no significant changes in the cabin temperatures and in the quantity of heat being removed from the cabin by changing ventilation rates. The increased flows tended to redistribute small quantities of smoke within the cabin and out the exhaust.

Anthony R. Turner

This paper is designed to present up-to-date picture of practical applications for water mist/fog fire fighting technology in marine markets. The paper will introduce the reasons for the development of technology, discuss the test program undertaken by Marioff and highlight the insights this has provided concerning the firefighting capability of water fog systems. Practical applications in the marine markets for accommodation areas, engine rooms and other spaces will be given with reference o the actual ships on which Hi-fog systems have been fitted. Land based use will be discussed, with references to systems installed or on order.

Robert P. Garner, PH. D., Bruce C. Wilcox, Harvey M. England, & Van B. Nakagawara, O.D.

The incorporation of a cabin water spray system (CWSS) aboard commercial passenger aircraft has been suggested as a mechanism of reducing passenger death and injury from the fire and smoke commonly associated with aircraft accidents. A potential health risk associated with CWSS is the physiological stress that would be imposed upon an individual by being wet from a CWSS activation in the aircraft cabin and then evacuated into a cold environment. The severity of this type of exposure would be proportional to the degree to which the individual was doused with water and the wind speed, and inversely proportionally to the ambient temperature. The physiological responses to partial wetting and subsequent exposure to cold environmental conditions have not been studied. The effects of cold exposure, as well as the degree of protection provided to the individual, particularly the cardio respiratory system, would need to be fully investigated to determine if the survival benefits of the CWSS outweigh the potential health risks.