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 causing his engine problems.
Paul Lamar
Amp meter is a good addition. Then put in the LED charge light. You may not be
watching like you should but when that red light comes on it will get your
attention unless you are getting lucky at the time.
Dale Davies
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