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Electrical failures -- how do you protect yourself?

Following another discussion thread, I'd like to seek your input on electrical failures. We all worry about our engines and their reliability but in reality as long as there is fuel, they tend to be very reliable.

What is a lot less reliable is the electrical system. Alternators break rather often, wires break, devices break, etc. This is a situation that does not get a lot of attention during pilot training yet it can be as dangerous as an engine failure.

Imagine you're in the worst IMC on a complex flight crossing borders etc. and your electrical system fails. Maybe your alternator breaks and your battery gives you 30 minutes to sort out things (provided you notice the alternator failure). Perhaps everything goes dark at once because it's not the alternator but something in the bus. What do you do?

Here's what I would lose in my aircraft:

  • both radios and VORs
  • the turn coordinator and the autopilot
  • the flaps
  • all lights internal and external
  • DME
  • certified GPS
  • ADF (tragic!)
  • transponder
  • intercom
  • engine monitor
  • gear retraction indicator lights (I have recently added a wing mirror for that)

Here's what I would keep:

  • airspeed indicator
  • standby altimeter
  • vacuum driven standby AI
  • basic engine instruments (tachometer, MP, CHT, EGT, carb temp)
  • Aspen glass cockpit for 30 minutes (internal backup battery)
  • yoke mounted Garmin 695 for several hours
  • handheld radio (for which I have an external antenna and a headset adapter)
  • iPad with enroute and terminal charts

I think this should allow me to continue my flight safely in every situation. What are your thoughts?

I am guessing that you already have a flashlight/torch in a reliable location to add to your list of what you'd still have? Pretty essential I would think.

Arguably you should also, and assuming no icing conditions, drop the gear (using the emergency mechanism if possible) and select landing flap.

It will greatly reduce your range but you will be looking for somewhere to land ASAP anyway (somewhere with a hangar, preferably...).

Yes I have a torch too.

For your list to work well, Achimha, you need to have to hand a schematic of the aircraft so you can see which circuit breakers to pull. Maybe on yours you can turn everything off individually but on mine a lot of stuff comes on with the Master switch.

Why would you turn off the transponder so soon?

Shoreham EGKA, United Kingdom

Well, I think there are two equally important scenarios:

  • alternator fails, systems continue to run on battery for some time
  • electrical system fails, everything including battery is dead

The battery case needs load shedding. That is difficult with a 70s Cessna as most circuit breakers are of the non pullable type (you can only push them back if they trigger, provided they would still trigger after 40+ years). I've looked into replacing them but that is quite a task and costs a lot of money, too.

Regarding the flap and gear, I don't think I would retract the gear with my remaining battery power unless I am really close to an airport. On IFR this means VMC conditions, otherwise I have to assume that I have to continue to my original destination until I get the handheld COM to work. I can always manually extract the gear but not retract. The flaps I wouldn't drop either because I regularly practise non flap approaches and if I drop them to 10/20° I might still have to continue to my original destination (IFR) and when dropping them completely (40°), I would have real troubles going around.

When this happened to me (in good VFR) about 100mi N of Stockholm, Sweden control gave me the ATC phone number and got my cell number, stipulating phone contact in the event of radio failure.

In the event, they let me turn off the xpnder despite being in Arlanda airspace while diverting to Bromma and I easily made it with only the 430 switched on.

On final to land, guess what? Ping! Everything came back on line, this despite numerous cycling of Alt, Master, etc. on route.

The one (and only) good thing the CAA has done for us (G - reg a/c) is that low voltage light mod. It would be tough not to notice that.

So a cell phone ought to be on your equipment list.

EGBW / KPRC, United Kingdom

I've seen plenty of advice saying tat you should only recycle the alt once. If it trips. Again then don't recycle again in case you start an electrical fire. Having said that when it happened to me (more than once on different aircraft) I recycled any times too!

EIWT Weston, Ireland

I think the "reset once only" is the best advice one can give without knowing anything whatsoever and having to be totally general.

So if you are going to draw up a checklist, this advice is your best option.

But obviously a lot depends on why it tripped.

If you are really certain the fault is a specific piece of equipment which can be switched off itself, and resetting the CB is desirable to bring other equipment back on line, that's different.

What does amaze me is how slowly these CBs can trip. I've had pitch servo burnouts on the infamous KFC225 autopilot where the current would have been several times the CB rating for tens of seconds and yet the breaker never popped, causing a near-fire inside the servo. And this is quite common across other aircraft.

These are thermal CBs, not magnetic CBs, and they trip only via a lot of internal heating. Their prime purpose is protecting wiring (from catching fire), not equipment.

So if a CB trip was accompanied by any funny smell I don't think I would be resetting it, no matter what

Shoreham EGKA, United Kingdom

I'm currently contemplating installing a VPX-pro and a back-up alternator in my permit a/c.

Forever learning

Just googled it.

That's a seriously nice bit of kit.

One can get backup alternators which go onto a spare vac pump mount and can, subject to varying paperwork issues, be installed in CofA aircraft.

B and C is the one with some STCs which could be used to support a field approval on an N-reg aircraft even if of a different type.

Pilots who have a KI256 vacuum horizon, and this is their only vacuum instrument (true for a TB20, usually) could install a KI256-lookalike electric horizon from Castleberry Instruments and dump the vacuum pump. This would prevent the daft situation whereby a vac pump failure takes out your autopilot. But the paperwork would be "fairly significant" due to the autopilot angle. I don't think anybody had done it.

Shoreham EGKA, United Kingdom

Quite right about the recycling but I should just add that this was a pre-existing fault that was supposed to have been fixed by engineers replacing the voltage regulator. So I didn't really have any concern about the wiring catching fire having spent hours on the ground fiddling with it.

However, it wasn't the regulator or the alternator (a replacement for which a friend brought out to Finland in his hand luggage (!)), or the wiring we subsequently replaced. But it might have been the alternator field CB, which appeared to go high resistance and responded with a sharp flick of the fingernail (not a push) during yet another electrical failure.

To my mind this speaks legends about the poor design, poor manufacturing quality, poor maintenance and extreme age of these ancient 'certificated' aircraft that some of us fly around in!

EGBW / KPRC, United Kingdom
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