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In a message dated 3/11/2003 2:56:53 PM Central Standard Time, vision_micro@hotmail.com writes:
There should be no effect on the EGT/CHT, however in some cases, depending
on transmitter com cable routing etc, especially with composite airframes,
there may be RFI strength sufficient to affect the OAT/CAT/OIL probes.
Verrrrry Interrrrresting!
David,
First, thank you very much for the reply. Let me clarify the conditions
I have a Lancair 320 slow build kit, circa 1989, first flight 1996. I have an EPI 800 system, including hardware updates that include board changes necessary for understanding rpm signals generated by LASAR double-magnet mags. I have flown with Terra com radios and Garmin 430 com. I do have an S-Tec 50 A/P. Com antenna cable routing is thru a comant switch down the panel and towards the rear as the antenna is in the vertical stab. The engine instrumentation is in the front (with the engine) and the OAT probe is located in the right wing flap fillet.
Every temperature sensor is affected during comm transmit - CHT, EGT, OAT, CAT and OIL. I have lived with this for years. The more difficult problem is the CHT warning (cyl is cooling too fast) and flashing red light during a request to ATC. Indeed, I do enter a slight dive when altitude hold is engaged (S-Tec 50) and I have keyed the mike to report that I am "level" at some altitude. My Rocky Mountain Instruments Micro-encoder OAT probe is not affected because it uses a thermistor.
A friend with a Cozy Mk IV has a similar problem with his VM 1000 system. Note that his antenna/wiring/engine location are quite a bit different than mine. Because his engine compartment is exposed at this time, we will be experimenting with your recommended solution to the oil temp problem - this will not solve our problem with other temp probes.
Note that I contacted two friends with Lancair 360s/VM1000s and neither has a problem with any temperature probe. Another with an ES and Electronics International system also see temps go cold during transmit.
To anyone out there with possible solutions - HELP!
Scott Krueger
N92EX
PS RG 58 coax sucks!
PPS: This was also sent directly to David.
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