Ignition system of gas turbine engines.

[joshuahsong]

What is the answer of the following question?
I think a) is right answer but the book says the answer is b).
Is that right?
The book is Oxford JAA ATPL - Powerplant

A gas turbine engine which has both high and low energy ignition systems uses the high energy system for (i), and the low energy system for (ii):


(i) / (ii)
a) Engine starting / High altitude relighting
b) High altitude relighting / Take off from contaminated runways
c) Take off from snowy runways / Engine start
d) Take off from flooded runways / Take off from snowy runways.

[RichardH]

According to Rolls Royce book The Jet Engine:-

High-energy ignition is used for starting all jet engines.

It then goes on to state that a high value output (12 joules) is required for relight at high altitudes. However, on contaminated runways as it may be necessary to have continuous ignition for automatic relight then a low value (3-6 joules) is better as it gives longer life to the ignition plugs/unit.

So I should say that B is the correct answer.

[joshuahsong]

Re-read the portion of the book with your answer and now I understand everything. Thanks.