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5 Answers

Multi-Engine alternator failure

Asked by: 7696 views Aircraft Systems, FAA Regulations, Flight Instructor

Is it legal to fly a multi-engine airplane with an alternator failure if the second alternator is ok? Does it make a difference if the flight is VFR/IFR/Day/Night?

Thanks.

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5 Answers



  1. Lucas on Apr 13, 2013

    Dear Oren

    If you are flying and experience an alternator failure it is technically legal for you to continue the flight to your destination, but it is way more preferable to land as soon as possible to make repairs. The alternator failure could be a symptom of a major electrical problem and lead to the second alternator failing and then no radios no navs and especially no gear. Its not always a good idea to trust the emergency extension. Even if it works how do you know the gear is down and locked (no green lights).

    If the airplane is on the ground and you need to initiate the flight then it is not legal for you to fly with a broken alternator. You need to keep in mind that FAR 91.205 describes the minimum equipment for VFR day/night and IFR operations, but 91.213 says that you may not take off with inoperative equipment unless you have a Minimum Equipment List (MEL) that says you may take off with a broken alternator (not likely that you have an MEL unless you are an air carrier, and unlikely that the MEL would authorize such an operation). An alternative would be to have a mechanic disconnect or remove the alternator and placard it inoperative, but I am pretty sure no mechanic in his right mind would do this.

    So sorry to say but, long story short, you shouldn’t and can’t.

    Lucas
    http://passfaaexams.com/

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  2. Matthew Waugh on Apr 13, 2013

    I have flown aircraft with MELs and I have been dispatched multiple times with a failed generator, and I have shut down generators in flight and the procedures didn’t say anything about landing as soon as possible or practicable.

    If the second alternator is not required by the type certificate and you can comply with 91.205 (which requires no power during the day, and just adequate electric power) and you can comply with 91.213 (and even if you decide the alternator needs intervention from an A&P I can’t think of any reason why they wouldn’t assist you) then you can fly the plane day or night VFR or IFR.

    Whether it is a good idea is a different question – but that’s why they anointed you Pilot in Command – so you can make the hard decisions.

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  3. John D. Collins on Apr 13, 2013

    I would check in the aircraft limitations section, kinds of operation limits subsection. This will specify if two alternators are required and differs by specific aircraft and model. For example, the 55 Baron indicates that only one alternator is required for day – VFR, otherwise 2 are required. In the 58 Baron, it indicates that 2 are always required. There is a significant difference in how the alternators are driven by the engine, the 55 Baron uses a belt drive while the 58 Baron a direct drive at the front of the engine. If the alternator in the former fails because of the drive system or the alternator shaft bearings freeze, you just lose electrical power from that alternator. In the latter case, if the same thing occurs, it can drop metal into the engine and the engine can fail or be badly damaged. Loss of an alternator in the second case would make me want to take Lucas good advice and get on the ground as soon as practical. Each airplane is different.

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  4. Sam Dawson on Apr 13, 2013

    91.213 does NOT just cover airplanes with MEL’S. There is a detailed procedure in 91.213 (d) for operating an aircraft without an MEL and lists those areas one must check. Among the areas you must check:
    1. The day VFR type certificate. Look at FAR 23 (or CAR 3 if you ar flying an older airplane) and the TCDS. I am assuming CAR 3/FAR 23 airplanes.
    2. The aircraft equipment list and Kinds of Operation List (KOL).
    3.THEN 91.205- not the first place you check.
    4. ADs (airworthiness directives).
    Then, if not listed in any of these areas and as pointed out earlier, the item must be removed or disabled and placarded inop.

    I’m not sure why CFIs continue to teach 91.205 and the silly mnemonic TOMATOEFLAMES as it has gotten pilots in trouble and resulted in certification action. As some examples, you will not find CHT gauge in 91.205, yet if the airplane has cowl flaps it must have an operational CHT gauge. IFR? You must have pitot heat if the airplane was certified under FAR 23 (though not CAR 3). Carb engine? Carb heat must be operational (again, CAR 3 and FAR 23). Flying a 172? IAW and AD you must have a vented fuel cap. Some newer airplanes require GPS to be operational for IFR if you look in the kinds of operations list. Flying a 172 R/S? The annunciator panel must be operational- it’s in the equipment list.

    So in this case you must go through this procedure for your specific airplane.

    Finally, as John pointed out electrical problems can be funny. It may not be just an alternator problem but something deeper- the alternator may be just a symptom. As an example, I had a generator go out in a Cessna 310. It was not a bad generator, but a bad generator control unit and, in the process of going bad it first shorted out the one generator. It was soon followed by the smell of smoke as the GCU started to melt.

    Don’t have it with me now but I will post later the case where a pilot took off with inoperative carb heat in a Cessna 150 after he and the mechanic used TOMATOFLAMES. The airplane crashed and his certificate was suspended for not knowing the procedure I outlined above.

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  5. Sam Dawson on Apr 14, 2013

    For those interested, here is the case I mentioned where the pilot used 91.205 to justify flying an airplane with inoperative carb heat.

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