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In my newly certified Lancair 360 (Lyc 360, Airflow Performance fuel
injection, standard electronics, etc.) I have a serious, seemingly
intractable communication problem on transmission only. In utter
frustration and bewilderment and humility, I turn to you for enlightenment.
Defining the problem is simple. On transmission on my installed Icom radio,
the reception (as explained and received by controllers) is always a loud
screeching sound. Reception within the airplane is excellent. Apparently
this sound is little or not all present on the ground when talking to ground
control. But the screeching is noticeable at 1000 feet, is disturbing at
5000 feet and is nearly insurmountable at 12,000 feet even when only 15
miles from an airport. Of even greater curiosity is that this problem does
not seem to be related at all to the aircraft electrical system because the
screeching continues even when the master switch (including alternator and
battery) are shut down. Further, I hear this screeching and interference in
the feedback of my radio but only when I attempt to transmit. The only
remaining electrical in the airplane is the magnetos and spark plugs. This
sound of screeching is positively correlated to engine rpm, i.e., gets
louder with an increase in engine rpm. On magneto check, the screeching
continues unabated on each magneto which seems to indicate that the magnetos
are not the source of the problem.
I use an Ivoprop cockpit adjustable electric prop with brushes that contact
two brass rings on the backside of the engine starter ring to supply
electrical continuity to the electric motor which alters the pitch of the
propellers. I am wondering if the brushes are the source of this screeching
even though the electrical circuitry to the brushes is shut off. If no one
else in this forum has encountered this version of communication problem,
then I must look to those features on my airplane which are completely
unique and which might be causing this problem. The Ivoprop and its
electrical are essentially unused by other Lancair 360 owners to my
knowledge and this is why I suggest it might be involved in this screeching.
The problem is so acute that I am repeatedly denied access into various
Class B airspace and of course would never be admitted to Class A. Since I
fly frequently at night and cross-country, I must find a solution. Can
anyone shed some light?
In the near future I will give a report of the test-flight and performance
of this airplane as well as lessons learned in construction; should make
interesting reading because as a builder, I've made nearly every
mistake--twice.
Greg
Nelson (gregsays@swbell.net)
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LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
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