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Some Hobbs Meters uses master electricity switch to keep the track of time.

So what If an cheapskate Skylane pilot wants to fly without electricity to lessen rent?

  • Which main six instruments would keep working?
  • Would the engine fail? (There are both carburated engines and fuel injected engines which complicates things a little bit)
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    $\begingroup$ I was once accused of this by a rental outfit. Turns out their Hobbs had broken. $\endgroup$ – pericynthion May 18 '19 at 20:56
  • $\begingroup$ Most Hobbes meters are activated by oil pressure and powered off the battery bus so you can't bypass it. $\endgroup$ – John K May 19 '19 at 0:21
  • $\begingroup$ Captain Cheapskate aside, it is still legal to fly planes that have no electric system at all, such as the Piper Cub. $\endgroup$ – Skip Miller May 19 '19 at 16:15
  • $\begingroup$ @SkipMiller flying without transponder in Class B and Class C is illegal as I remember. $\endgroup$ – Delta Oscar Uniform May 19 '19 at 16:50
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    $\begingroup$ @jonathanIrons, that is very true. But there is far more airspace below Class A space that an airplane without any electric systems at all where flying a Piper Cub or other non-electric equipped airplane is perfectly legal. And the Piper Cub and other similar planes cannot climb up to Class A space anyway... $\endgroup$ – Skip Miller May 19 '19 at 17:28
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The engine wouldn't fail. Avgas powered engines use 2 magneto systems which are independent of the battery and alternator, so if your alternator dies or you lose the electrical system it will run as if nothing happened. Starting it does require the battery and electrical system though to run the starter motor. Aviation engines with computerized ignition systems have backup batteries so they will also not fail due to an electrical system malfunction.

As for the "6 pack" cluster of instruments 3 are not powered at all: Airspeed Indicator, Vertical Speed Indicator, and Altimeter. 3 are powered, although there is no hard and fast rule the Attitude Indicator (AI) and the Heading Indicator (HI) are usually vacuum powered from the engine and the Turn Coordinator is usually electrically powered. There are many exceptions to this.

So keeping the electrical system off doesn't affect the primary instruments much, provided the airplane stays in VFR. What captain cheapskate won't have for sure is any radios, transponder, GPS, ADF, VOR, or any other communication or navigation aids.

All these things you could probably do without on a completely VFR flight, provided you don't need communications. However, the engine temperature and oil pressure gauges, EGT gauge, and fuel gauges all work using electricity as well, and I'd really hate to lose those. A typical steam gauge Cessna isn't going to have an electrical fuel pump, but many piston singles do. Running without the electrical system means you'd lose that to, and that's considered an important safety system to back up the mechanical one in case of failure.

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    $\begingroup$ Like this video proves: youtube.com/watch?v=fZtpLFICLec $\endgroup$ – Jan May 18 '19 at 20:18
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    $\begingroup$ Captain Cheapskate could use a separate radio, though. It wouldn't depend on the aircraft's electrical systems. $\endgroup$ – user May 18 '19 at 21:29
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Need electricity for a Beacon Light. Big discussion having it on all the time here

When to use beacon, anti-collision, strobe, logo, and navigation lights?

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