The alternator checked out OK. The last flight I flew I left both the fuel pumps on
the whole flight. Usually, I only use both when on take off and landing. Maybe the
current draw was too much for the 40 amp alternator. The guy at the alternator shop
said that at and above 2/3 the rated current, the voltage starts to drop off. Hmm. I
have two of the fuel pumps that Tracy sells, I don't know what the current draw on
them is, a dynon D10- 1 amp aproximately, Xcom radio- . 5 amp, Terra transponder- .75
amps, EC2 and EM2- ? amps, 4 LS1 coils- ? amps and two 18 AH saturated mat batteries.
Maybe time to do a current check on the batteries and trade one out for a new one. I
have a new one, the old ones are coming up to two years old. I have them on a float
charger anytime I'm not running the engine. Any thoughts?
Brian Trubee
You need an ammeter.
Paul Lamar
Brian,
In my opnion you do not need a ammeter as only more
weight! The voltmeter will tell you what state your battery is, you do
not really need to know what the alternator is putting out. If the
voltage is going down and the alt is OK then you alt is not up to the
job! as dale? said put a clamp-on the alternator output and turn
EVERYTHING on and watch the voltmeter and if the draw is more than say
30 amps get a bigger alternator or ditch some of the load.
John Burey
Get realistic John. The weight is ounces. You cannot have too much
information. An ammeter gives an instant early warning of what can happen.
If suddenly the ammeter shows a discharge the EFI and electronic ignition engine is
going to stop sooner or later. You can then turn off non essential electric devices
to give you more time to land. You will instantly know if you have solved the
problem. You can't just pull over to the side of road and stop.
Paul Lamar
You get the same info more easily with a voltmeter Paul. And, it's easy to set up a
low voltage warning. If the alternator isn't keeping up, the bus voltage will be
low. It's easy to figure out. You don't always need "more information" when you're
trying to fly the airplane.
Matt-
There is a delay with a voltmeter. No delay with an ammeter. Some times you need a
warning. A C182 will fly with a completely dead battery. The cost is next to nothing
and there is no down side to an ammeter. If you are having trouble flying the
airplane you already have an emergency.
Paul Lamar
I always wonder about the excuses made by "interested parties" for compromising on
the presentation/collection of real time system data. You are all so smart that you
have the ability to extrapolate all permutations of a single point of collection,
voltage or current that you can ascertain the complete health of an electrical system
based on a single factor in a complex multi-functional power distribution system that
your life depends on? 4 ounces, maybe $50 to get 2 factors of a basic power equation
is out of the question?
I know why experimental aircraft have double the rate of GAs accidents and fatalities.
I have been working with electrical systems for over 30 years and have never
encountered a situation where I had TOO MUCH INFORMATION.
I'll be blunt here. YA'LL ARE STUPID!
C. Smith
ROFL
Paul Lamar
Oh boy! We need more info! Let's get it with more sensors and more indicators!
Lets put manometers in all places on the engine and airframe, just in case one of
your baffle seals starts leaking! The engine might overheat and you wouldn't know why!!
How could anyone not be lured by the siren song of having access to more data?
The thing that you aren't discussing is that your primary job is to be the test
pilot. As such, you need to put limits on the volume of data that you're trying to
pay attention to. In professional test programs, the test pilots aren't looking at
diagnostic info while in flight. They're looking at their flight instruments. The
reason for this is safety.
You don't have a flight engineer on board.
If you need more data, go ahead and add the instrumentation, but I recommend doing so
such that it feeds data to an acquisition system (logger). Paul can recommend one.
It can be PC based. It could be a video camera.
Paul, you have been involved in at least one accident investigation that involved a
pilot that lost control of the airplane. It's quite possible this was because he
wasn't focusing on the fundamentals of flight, but instead was worried about trying
to figure out why the engine was doing what it was.
After your system is bomb proof, you can tear out all of the stuff that you'll never
look at again, and regain the simplicity, light weight, and lower the number of
points of failure.
Don't underestimate the danger of distraction.
Matt-
That fatal accident I was involved in had nothing to do with distraction.
It had everything to due with pilot judgment. He tried to turn back and the canard
stalled. There was a plowed field ahead he could have landed in.
He knew he was having trouble with his engine running reliably.
Perhaps if he had more instrumentation to begin with he could have figured out what
was causewaying his engine problems.
Paul Lamar
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