4 (a) In any working or living space there is usually an abundance of combustible materials, plenty of oxygen in the surrounding air and many potential ignition sources fulfilling thus the main requirements of the fire/combustion triangle.Explain why then the initiation of combustion or fire is still a relatively rare event.What other conditions are necessary for the initiation of combustion or fire to happen and how does this translate to the burning of liquid and solid fuels?

(b) The European and American testing standards are based on the same two methods for determining the flammability range of flammable vapours and gases.Briefly outline these methods and discuss the differences, if any, between the American and European reported flammability limits.

c) The vapour pressure over a liquid can be approximated using the Antoine equation:log = / where P is vapour pressure (kPa), T is temperature (K), and A and B are coefficients set by the fuel. Using the reference data below answer the following:

(i) What is the boiling point of Jet A fuel at sea level?

(ii) Determine the flash point of Jet A fuel at sea level and at 10,000 m.

(iii) If the fuel temperature is 25C, is the vapour above a pool of Jet A fuel flammable at 10,000 m? [5 marks]Reference data:For Jet A fuel: A = 10.08 and B = 2263 (using units of Pa and K)For Jet A fuel: lower flammability limit (LFL) = 0.7%Air pressure at sea level: 101 kPa Air pressure at 10,000 m: 26 kPa

(d) Using the the1996 explosion on flight TWA 800, as an example, explain how changing conditions can complete the oxidant fuel ignition source triangle to generate an explosive mixture. Discuss flammability limits in this context and illustrate your answer with the appropriate P vs. T flammability limit diagram for this case study. How did altitude, design, and equipment faults contribute to the problem?