First I’ve heard of this. I don’t think I’ve ever heard of an alternator failure provoked by startup. All the aircraft with split master switches I’ve flown, on none of them is it a checklist item to start up with the field coils off.
After the failure of my Alt 1 Voltage Regulator I am trying to find out if it’s maybe a mistake to leave the Alternator switches on at engine shutdown. The POH is not really clear here, and there’s various opinions (sure) in the Cirrus community on COPA.
How do YOU do it? (I understand that it probably depends on the electric system of the plane.)
Hmmm, never considered this. My sequence is as I was taught:
- avionics master – OFF
- throttle & mixture: IDLE / CUT-OFF
- mags – OFF
- master switch – OFF
Edit to add: this is in Cessnas (and the Pipers I learned to fly on many moons ago)
In the SR22 that would translate to what I do:
- Avionics off
- Idle/Cut-off
- Mags off
- Alt 1 and 2 off
- Bat 1 and 2 off
At my club the checklists instruct to switch alternator off prior to shutdown (on planes equipped with Lycoming 0-360 power plants).
In the Flight Design CTLS it’s:
Master Off
Batt & Gen Off
Ignition Off
Fuel Shutoff Off (high wing tanks)
BRS pin replace
First off, follow the flight manual procedure.
If there is lack of detail, avionics off before the engine stops. It certainly won’t hurt to turn the alternator off prior to shutdown if you are able, but it is not required either. In some systems, you can’t anyway.
As an aside, once I began to understand the maintenance implications on alternator drives in Continentals with gear drive alternators, I got into the habit of turning the alternator off as the landing light went on on a night final approach – for the following reason: You’re drawing a lot of current, and the landing light is the straw which will break the alternator drive coupling. Than coupling is designed to slip in some large Continentals, and once it does, it’s never going to work reliably after. When you define the current requirements (by turning on all of those lights, with radios all on, and running flaps/gear etc.) you have defined the power to be drawn. Power = torque x RPM. When you reduce RPM (to idle) the torque demanded goes way up – and you challenge the drive coupling. Once I pull off the runway, and turn off a few lights, I’d turn the alternator back on, and let it top off the battery as I taxied in.
Now that I have LED lights, I don’t worry any more :)
My generic routine:
Non-essential electrics
Avionics
Throttle 1000rpm
Mixture
Alternator
Mags (once engine stopped)
Master
Fuel
Shutdown routine SR20 :
Throttle idle
Avionics
Alternators (both)
Mixture cut off
Strobes off
BAT1, BAT2
Mags
Sometimes, when I have to write down engine data after shutdown:
Throttle idle
ALT1, ALT2
Mixture
Avionics
Strobes
Batteries
Mags
SR22
Avionics off
Alt 1 and 2 off
Idle cut-off
Mags off
Batt 1 and 2 off
1750 hours since new with the original alternators, I made an overhaul of the alt1 at 550 hrs, alt 2 never touched since new.
