The typical start sequence of a gas turbine engine on the ground and the main components involved would be the following:

• Start selected: the start valve admits air supplied by the pneumatic system to operate the starter. On nowadays commercial aircraft, the FADEC controls the start valve electrically and operates it pneumatically with bleed air.
• Ignition ON: the igniters are selected ON and are ready to light the mixture.
• High-pressure fuel ON: after fuel is delivered by the high-pressure shut-off valve (HPSOV) it is sprayed into the combustion chamber by fuel nozzles under high-pressure where it is mixed with compressed air and lights up.
• Light-up: the mixture starts burning and the flame spreads all along with the combustion chamber (since it is interconnected). The flame becomes self-sustainable.
• Self-sustaining speed: all the engine’s spools have reached a self-sustaining speed where assistance from the air starter is not needed anymore. The air starter is disengaged by the coupling between engine N2 spool and starter by the use of centrifugal forces.
• Starter circuit canceled.

Incorrect answers:

• “A combustion chamber, a starter, and bleed air to ignite the air/fuel mixture” – bleed air is not igniting anything. The igniters light up the mixture, not the bleed air. Bleed air from the APU, another engine, or a ground pneumatic unit is only directed to the air starter that will rotate the HP compressor (N2).
• “A turbine to compress and ignite the air/fuel mixture in the combustion chamber” – the turbine is not compressing the air; it is only driving the compressor that will compress the incoming air mass flow.
• “High-pressure fuel pumps and a compressor to raise the pressure of the air/fuel mixture for starting” – HP fuel pumps are definitely needed, however, what is wrong with this answer option is that it states that the compressor raises the pressure of the air/fuel mixture. This is incorrect as the compressor only raises the pressure of the air.