Pilot's Guide to Avionics 2013-2014 - 58

faa c.r.S. tfgr 831K
Setting the
Standard in today'S
World of avionicS
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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

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http://www.topflightavionics.com http://www.templeavionics.com

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