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insulations generally used for the covering of high tension leads are easily destroyed by the action of heat. If placed near a very hot motor wall they can melt and short-circuit, frequently causing fires.
The leads ought in to case to pass under the gas pipes
1 c. Backfiring. Backfiring is caused by bad functioning of the motor, carburetor, or more rarely, the ignition. The latter is indeed rare but cannot be completely avoided. 
Knowing the gravity of the consequences, the adaptation of the motor to the airplane ought to permit all backfiring without the least danger of fire.
Realizing that the most improved motors still have danger of fire, it is essential to stop or to limit the spreading of the flames in such a manner that they may not reach in inclosure of gas or find inflammable bodies. 
For this the following principles should be a applied: 
(a) Either (1) lowering the temperature of gas by wire gauze,
or (2) mechanical isolation by automatic valves.
(b) Complete evacuation to the exterior of the fuselage of the dangerous flames which the preceding contrivances would have allowed to escape.
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