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I am sending this note to the Lancair Mail List as well as Lancair Avionics
and Vision Microsystems. I am hopeful that I will get a solution or at least
some direction from someone. Seems that, within their areas of
responsibility, everyone has taken an understandable position, but I still
have a situation.
I have experienced problems with my fuel gauges since first flying my Super
ES. I have Electronics International probes and initially had EI fuel gauges
and OAT gauge.
Both gauges were affected when the PTT was used. After having the
instruments inspected and cleared by the manufacturer, I re-installed them
with no noticable improvement. My avionics shop and the A & P who had done
the panel installation tried many, many things (shielding, filters, diodes,
wiring checks, wiring re-routing, etc.) with no improvement in the situation.
After talking with Lancair about the problem, it was decided to change both
instruments to VMI units. We did this and saw the same problems with the new
units. VMI took the position that the problem was with the probes and that
if VM probes were installed the problem may go away. This obviously was not
sufficient motivation to cause me to remove the wings of a finished and
flying airplane.
Basically, I was told by those connected with this situation that there was
nothing that could be done and I would have to live with it. I disconnected
the warning buzzer for the EC 100 annunciator panel and "lived with it".
Turned out that living with it involved explaining to my passengers each time
the EC 100 showed WARNING: LOW FUEL that it was just a glitch and there was
no real problem. So far, to my surprise, no one has questioned my
explanation.
With all this as background, here is the kicker. As I have become
comfortable in the plane, I have been able to be more observant of details.
Recently, I noticed that when the PTT was used the oil temperature number as
well as the outside air temperature number went down. Took me a few tests to
realize what was really happening and, yes, when I talked on the radio the
numbers on those two instruments, along with the aforementioned fuel gauge
numbers, changed. When the PTT was released, the numbers would return to
normal after about a minute. Interesting part of this latest information is
that these two instruments use all VMI wiring, sending units and probes.
I assumed that I would have to once again "live with it". On a whim, I
mentioned the problem to my next door hanger neighbor who has a Glastar with
the VM 1000 display and VM outside air temp gauge. We checked his plane and,
sure enough, when his PTT was used the oil temp and outside air temp numbers
changed. Verrrrrry interrrrrresting.
Please excuse the rambling and excess detail but I need some input on this.
I no longer believe the problem is built into the plane. I think the VM 1000
may have some problems. Anyone else having this problem? Anyone solved it
yet? Any suggestions? Perhaps there is a need for some sort of an inhibit
circuit (like the one used with the Stormscope) that would "freeze" the
displayed numbers until the PTT is released. Any and all input will be
appreciated. I freely admit lack of knowledge about avionics. If I have
said something really dumb don't hold it against me.
Thanks for any help.
Jim Scales
N98AF
(115 hours on it and flying great)
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
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