Boeing 737-236 series 1, G-BGJL: Main document - Leonardo

mm can be anticipatedat peak power, and the calculation showed that thermal stressesin the order
of 29,000 psi would therefore be generated in theliner material. Tests on sample Hastelloy X
material at elevatedtemperatures showed that, at this stress level, the fatigue lifeof the material
would vary between 100 cycles at 980°C to1,000,000 at 815°C. These results serve to emphasise
thevery damaging effects of high temperatures and it can thereforebe argued that hot spots in the
can will suffer rapid localisedcracking within, say, 1,000 flights from new or repair whilstthe cooler
regions would have a vastly greater life. The fatiguelife of the can is thus essentially limited by the
performanceof the cooler, longer-life regions, rather than the performanceof localised hot spots.
1.16.2 Search of existing data on Aircraft Fires
1.16.2.1 Emissions from burning aircraft cabin materials
Much attention has been paid to the emissions from the syntheticfoams used in cabin-seat cushions.
Thermal decomposition of suchfoams in air produces a complex mixture of smoke and gases,
whichnot only varies with the type of foam (eg polyurethane, polyetherurethaneetc) and whether it
has added constituents (eg flame-retardants),but is also dependent upon combustion conditions - eg
flamingor non-flaming (eg smouldering) conditions. However, the othercabin materials such as
wall panels, windows/surrounds, overheadpassenger service unit panels, overhead baggage
compartments,ceiling panels, sealing strips, curtains etc. also produce toxic,irritant gases and
smoke when burnt.
Comprehensive data on the gases emitted from the combustion ofseat-foams and other cabin
materials is contained in a FederalAviation Administration (FAA) report1 (Appendix 15a). These
dataindicate that the well known problems associated with the foamsused in cabin seat-cushions
represent only one part of the generalproblem concerning the products of combustion of aircraft
cabinmaterials.
Polyvinylchloride (PVC) material from cabin panels produces almostas much carbon monoxide as
does polyurethane foam, for the sameweight burnt, but also produces almost six times the
concentrationof the acidic gas hydrogen chloride.
Polyurethane foam produces less hydrogen cyanide than modacrylicmaterial, which can be used for
curtains, carpets etc. Relativelysmall weights of any such materials can produce substantial
concentrationsof toxic/irritant gases and smoke when burnt within an aircraftcabin volume.
eg. The burning of only some 5.7 lbs of modacrylic curtain materialin a
cabin volume of about 6,000 cubic feet, will produce a critical
concentration of 200 parts per million (ppm) of hydrogen cyanide-
sufficient to induce rapid incapacitation and death.
Wool is often preferred to modalcrylics for curtains, carpetsetc (as was the case on G-BGJL), but
also produces hydrogen cyanide,although in reduced quantities.
Fluorinated materials which are frequently applied in the formof decorative films to cabin wall
panels (eg 'Tedlar' Polyvinylfluoridefinish on the wall panels of G-BGJL at Manchester) emit the
intenselyirritant hydrogen fluoride acidic gas when burnt.
Fibreglass materials generally exhibit much lower toxic/irritantgas emissions, dependent upon the
resin used - eg phenolic fibreglassis superior in this regard to epoxy fibreglass. Such materialscan
still, however, emit large concentrations of particulate -ie 'smoke'.