Originally published April 1997
This month's program was given by Jeff Landon of High Desert Avionics at Fox Field. He started off by showing us an instrument panel mockup that he uses to explain the proper plumbing of Pitot-static instruments. He noted that it's not a good idea to plumb the altimeter into the DG, as this can leave you indicating about 5000 feet above your actual altitude. He then addressed questions for the gathered masses.
Legal Radios: Recently the FCC declared that all aircraft must be fitted with 720 channel radios. Technically, the sticking point is that frequency stability must be ±0.03 MHz, not the previously required ±0.05 MHz. While some 360 channel radios can be retrofitted to meet the new standard, in general he said it would not be cost effective, i.e. it would almost be the cost of a new 720 channel radio.
Can homebuilders install their own radios: Technically yes. The question comes up because Bendix-King and other companies do not like their dealers playing mail order house with the high-end equipment. Besides, Jeff, who recommends King avionics, will sell it to you at cost (make you a "smokin' deal"). If he sells enough, he gets a kickback from King. Remember, he makes his money and his reason for being there by doing the installation or working with you to do the insulation. Support your local merchants. The downside is that thieves also like King Radios, so be sure your insurance is ready for them to be stolen. Since the radios hold their value well, you shouldn't be out too much to replace them. What about a better lock on the door? Then they'll just tear up the door getting to the radios. Less of a problem if the airplane spends most of its time in a locked hangar.
What about using laptop technology for a Mission Computer/Data Acquisition System: Jeff really couldn't address this, since he normally works with certificated aircraft. This did launch into an animated digression by Mike Meyer and some other folks. Looks like Gary Aldrich needs to talk to Mike Meyer about putting on a meeting program.
Pitot-Static Plumbing Materials: Jeff keeps a supply of this stuff on hand, so use the good stuff. You'll save yourself untold headaches later by minimizing the number of leaks to find. Yes, this is a big problem in the homebuilt community.
Transponder Antenna in Compost Aircraft: Jeff recommends using a normal antenna either sticking out the bottom or located inside the fuselage with a real ground plane. He has seen way too many problems with people who use the mylar tape glued into the fuselage for a ground plane.
Interference: Ideally, your transponder and COMM antennas should be separated by at least 5 feet, and the feed wire should be on opposite sides of the fuselage to avoid cross-talk.
Transponder Check: required every two years for VFR flying. Jeff can do it for you right there in the shop. Figure $60 for the transponder and $125 for the Pitot-static leak check. Why a leak check? He has to connect directly to the encoder to do the test, which means opening up the static system. Figure on paying more if he has to fix a bunch of leaks.
Handheld vs. Panel Mount GPS: For homebuilts, which can plan the instrument panel to allow a location to put a handheld GPS, handhelds are the way to go. They can be developed much faster, many have moving maps which panel mounts don't, and you can take them with you so the thief who takes your radios won't get it. When costing out a handheld, remember to plan on using an external antenna for good coverage and how you're going to get power to it.
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Revised -- 8 April 1998