My Cessna 172 SP's alternator died while stationed at a class D airport, less than 10 miles from my home field (another class D). Both airports are within the mode C veil of a nearby B airport.

Assuming that I fully charge my battery before flying to my home field for repairs, it seems to me that I can do so in full compliance with regulations. I'll fly VFR during the day, and plan to only keep my beacon (anti-collision), transponder, ADS-B out and one radio online, and shut down all other electrical equipment to make double sure my battery will have plenty enough for the flight. I'll also carry a battery-operated backup radio just in case.

My question is: am I right in assuming that I'd be perfectly legal taking this short flight? Or do I need a ferry permit from my local FSDO?

  • $\begingroup$ No A&P able to travel to the aircraft? $\endgroup$ – Ron Beyer Jul 19 at 15:19
  • $\begingroup$ That's a bad idea, even if it's legal, deep-draining a battery is a good way to ruin it and cost you more money. If you're so close to your home base it shouldn't be hard to get an A&P to replace it $\endgroup$ – GdD Jul 19 at 15:19
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    $\begingroup$ Welcome to aviation.SE! I think the real question here isn't about the mode C veil, it's whether a C172 with an inop alternator is airworthy. $\endgroup$ – Pondlife Jul 19 at 15:53
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    $\begingroup$ ATC can issue you a clearance or waiver, call them up and explain what you need to do, chances are you'll be told to go ahead but coordinate with them. $\endgroup$ – Ron Beyer Jul 19 at 16:44
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    $\begingroup$ @user4867444 Well, if the alternator is required for the aircraft to be airworthy then you'll need a ferry permit in any case. That's why I'd start with that question and go from there. $\endgroup$ – Pondlife Jul 19 at 17:26

No, you do not need a ferry permit to fly without the transponder[*]. If you wish to fly inside the Mode C veil, it is sufficient to reach out to ATC and ask for permission. For a 10 minute flight that stays low to the ground, I'm sure they'll be happy to help. It makes it easier on them if you can fly when they aren't slammed, but since you're not in their airspace, they are pretty understanding.

You might be surprised by the number of transponder-less aircraft flying under the Mode C veil: lots of old planes which never had electrical systems, lots of new ultralights, and there could even be gliders around. You won't be the only one up there without ADSB-Out.

FWIW, I expect that your plane can fly quite some distance with everything off but the transponder. They typically consume 10-20W, so you should have several hours' worth of energy.

[*] In general flight without an alternator might not be allowed, though. This depends on the Comprehensive Equipment List, or Minimum Equipment List, or Kinds of Operation Equipment List, or basic certification standards in effect when the plane was certified. If the alternator for your specific plane is on one of those lists as required equipment then the plane would be considered not airworthy and would require a ferry permit.


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