Type training · Boeing 757 B1.1 · ATA 24

Boeing 757 B1.1: Electrical Power (ATA 24)Type training questions & answers

IDGs, APU generator, bus power control, AC and DC distribution, TRUs, batteries and standby power.

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Sample Electrical Power questions with answers

Three questions from the free preview. Think of your answer first, then open the explanation.

  1. 1.What are the output characteristics of each Boeing 757 integrated drive generator (IDG)?

    • A.115/200 V AC, 3-phase, 400 Hz, rated at 90 kVA
    • B.115/200 V AC, 3-phase, variable frequency, 120 kVA
    • C.28 V DC, rated at 400 A
    Show answer and explanation

    Correct answer: A. 115/200 V AC, 3-phase, 400 Hz, rated at 90 kVA

    Each IDG supplies 115/200 V AC, three-phase, 400 Hz power and is rated at 90 kVA (about 86 kVA is available at the load bus after feeder losses).

  2. 2.Can two AC power sources on the 757 be connected in parallel?

    • A.No, the system prevents parallel operation
    • B.Only the APU generator and external power
    • C.Yes, the IDGs normally run in parallel
    Show answer and explanation

    Correct answer: A. No, the system prevents parallel operation

    The power sources cannot be paralleled. Bus tie breaker logic and the interlock circuits make sure only one source feeds a given bus at a time.

  3. 3.What does the integrated drive generator (IDG) contain?

    • A.A constant speed drive and generator in one housing
    • B.A generator driven through a separate gearbox CSD
    • C.A generator and a hydraulic pump in one housing
    Show answer and explanation

    Correct answer: A. A constant speed drive and generator in one housing

    The IDG combines a hydromechanical constant speed drive (CSD) and an oil-cooled brushless generator in the same housing.

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Part of the Boeing 757 B1.1 type course

One chapter of the Boeing 757 B1.1 type course question bank, for the 757-200 with Rolls-Royce RB211-535E4 engines, written in our own words for revision. Your type course and the aircraft maintenance manual stay the authority: limits and procedures can differ between airframes and operators.

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