Fuel tank vents

[pelmet]

The starter circuit might be fused in some large planes but typically will not be because the starter motor needs such a high current to function normally. In automotive applications there is a heavy gauge cable straight from the battery post to the solenoid on the starter. I presume small piston engine airplanes are the same.

I seem to remember a slow blow fuse on the C-150 as well.

[pelmet]

One last point about the humble fuel cap .... be sure
that the gasket or seal is nice and new and pliant and
springy and thick. The cap should be just a little hard
to put on, as you compress the seal or o-ring.

This is really important.

As the gasket/seal ages, it compresses and contracts
and the cap gets really easy to put on. But it will allow
water (rain) to get into the tank. Ask me how I know
this.

If it rains hard enough, and the aircraft is parked outside,
you can get enough water in the tanks that you drain
out straight water - no bubbles!

Water gets into the gas tank via the filler neck, either
via old fuel cap gaskets/o-rings, or via bad gas. I've
experienced both. Not condensation. Some brain on
the internet did a calculation and said that you would
need 100 years of wx changes and condensation to
get significant water in the tank.

tl;dr

Be suspicious of aircraft that are parked outside, for
water in the tanks. Change the fuel cap seals frequently
if the aircraft is going to be parked outside in the rain.

Very good points. I must admit that have operated aircraft that had been left outside or inside for long periods of time with partially filled tanks and there was no water in the tanks making me question how much this condensation theory resulting in water in the tanks. However, it is prudent to consider such a possibility.

As stated, a bad fuel cap O-ring can let water in. But, it can cause another problem. It can let fuel out. Happened to me on a delivery flight in a Citabria that had been hangared for a long time. I had a significant fuel leak enroute and had to stop and refuel instead of going non-stop. So if you happen to fly an aircraft that has no fuel guage(some are legally allowed to do this) and especially if the fuel cap is not in view or it is night time, it is doubly important to make sure the O-ring is sealing properly.

[Beefitarian]

The starter circuit might be fused in some large planes but typically will not be because the starter motor needs such a high current to function normally. In automotive applications there is a heavy gauge cable straight from the battery post to the solenoid on the starter. I presume small piston engine airplanes are the same.

I seem to remember a slow blow fuse on the C-150 as well.

Is it the charging fuse, in parallel with the battery contactor?

[iflyforpie]

The starter will have no effect on the electrical system if it is only mechanically engaged to a running engine. The starter contactor disconnects it from the electrical system.

What will happen is it will overheat and burn out, both from the mechanical stress and from trying to get rid of the generated electricity which will be by excessive arcing to ground. I've seen it before, it's not pretty and very smelly. You will probably also get a whole whack of radio noise.

The starting circuit is just the grounding circuit for the starter contactor, so the CB is only 5A or so. I do not believe there is any protection for the starter except the alternator CB, as the positive battery post goes to the master contactor and then straight to the starter contactor on most aircraft, the main bus then taking a lead off the hot side of the starter contactor.

[CpnCrunch]

The starter circuit might be fused in some large planes but typically will not be because the starter motor needs such a high current to function normally. In automotive applications there is a heavy gauge cable straight from the battery post to the solenoid on the starter. I presume small piston engine airplanes are the same.

I seem to remember a slow blow fuse on the C-150 as well.

Its the wing flap circuit.

[Colonel Sanders]

The starter contactor disconnects it from the electrical system

Yet another thread-jack of the thread-jack, with more
useless trivia suited for an AME final exam ...

Under G, it is possible for the starter solenoid to engage
while the engine is running, even in the absence of power
to the control terminal (ie no electro-magnetic energizing)

This depends on the orientation and mounting of the
starter solenoid. For example, the early-style Ford
starter solenoid, used on many light aircraft, if mounted
upright, will engage around +4G's.



This is why Piper mounted it sideways, all those decades ago!

[iflyforpie]

This just keeps getting better and better CS!

[pelmet]

This is why Piper mounted it sideways, all those decades ago!

Interesting.

So Mr. Piper was quite smart about this possibility. Is it safe to say that Mr. Pitts was just as smart in his design?

[Colonel Sanders]

You bet! Starter solenoid is exactly as pictured (early
style Ford) and is mounted sideways beside the battery,
behind the rear seat.