Pilot's Guide to Avionics 2013-2014 - 58
faa c.r.S. tfgr 831K Setting the Standard in today'S World of avionicS • • • • Servicing helicopters, fixed wing & light sport In-house avionics NAV/COM and autopilot repairs Avionics sales, service and installations Pitot static transponder certification Willow Run Airport (YIP) 48162 F Street Belleville, MI 48111 phone: 734-484-9511 • fax:734-484-9636 martyhall@topflightavionics.com www.topflightavionics.com TEMPLE ELECTRONICS COMPANY INC. Avionics Sales, Service and Installation • 3 locations serving the greater Houston area HOU, CXO and TME • RVSM, Bi-Annuals 14CFR 91.411 appendix G & 91.413 • Custom CNC cut panels, Powder coating, Laser Engraving with fast turn times • Glass Panel experts • In-house Avionics NAV/COM, Radar and Autopilot repairs 8484 Scranton St Houston, Texas 77061 Phone: 713-649-8175 • Fax: 713-649-8760 sales@templeavionics.com www.templeavionics.com UNDERSTANDING AUTOPILOT UPGRADES Continued from page 57 just check one thing at a time and end – don’t start – with a coupled approach check. It will take an hour, maybe a little more. But by the time you’re through, you can turn it over to the owner with a clear conscience. If the owner isn’t aboard for the flight test, we will take them up on a demo flight and make sure they know how to use it, which also is an opportunity to show off, since you know the system is working. Teaching the user how the system works is really a way to advertise as an avionics shop. This will get good word of mouth (advertising) and generate more business.” Weber agreed flying with the pilot is essential. “If we have a low-time pilot, we will try to arrange a CFI to fly with him,” Weber said. “If at all possible, we want the pilot who will be flying the system aboard, whether or not he (or she) is at the controls. This tends to be a very interactive flight with a lot of communication between us and the pilot, and we want to stay well within the airplane’s performance envelope. Ideally, you want a calm VFR day with minimal turbulence to make adjustments easier – a little turbulence can mask a lot of problems.” Hall added that a demo flight provides an opportunity to show off how well the new autopilot installation works and ensure the pilot understands any new features. “We designed the DFC-90 to replace an S-TEC 55X, so there should be no training required on those functions,” Hall said. “But we add new features like our straight-and-level button and envelope protection. Demonstrating helps the pilot understand what those functions do.” There are some tricks that can help in troubleshooting autopilot problems. According to Weber, the flight director (on airplanes equipped with one, or with a glass panel that provides equivalent functionality) “is one of the most underused items in troubleshooting, and 75 percent of the time I’ll ask the pilot or another technician what the command bars are doing. If the command bars go left and the servo goes right, it’s a bad servo. If the command bars are trying to roll the airplane on its back, it’s probably a problem with the attitude reference.” Evans said cable tension can be a special problem in business-class airplanes that operate at high altitudes. “You have thermal cycling, which can affect cable tension,” Evans said. “In the King Air and small jets, it’s not unusual to get pitch porpoising after about an hour at altitude. It’s a symptom of loose cable tension, which gets looser as the temperature drops. Set cable tension closer to the high end of the allowed range on the ground to eliminate trouble up high. “Control surface friction also is an issue for autopilots. It’s a major limitation in some jets, where you’ll have to test control-system tension against yoke deflection. If there’s too much friction, the servo won’t be able to overcome it. I’ve had a customer complain about electric elevator trim, got in the airplane and found that it required a lot of force to move the yoke. In a situation like that, the safety clutch just slips. I told the customer he didn’t have an autopilot problem, he had a serious pitch trim problem.” q - 58 -
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