New Helicopter Autopilot (HeliSAS) From Cobham Available For
In the helicopter world, autopilots have been a luxury reserved
for big-ticket ships like the Bell 412, Eurocopter EC155 and
Sikorsky S76. But that may change in within the next few weeks as
Texas-based avionics firm Cobham closes in on FAA certification for
HeliSAS, its two-axis autopilot system.
HeliSAS consists of four main components. Two of them are
servos, which physically connect to the control tubes that link the
cyclic to the pitch and roll sides of the swash plate. The third is
the flight control computer, which serves as the electronic
interface between the servos, the aircraft's avionics, and the
fourth component-a slim control head mounted in the instrument
As an autopilot, HeliSAS offers heading (HDG), navigation (NAV),
back course (BC), altitude (ALT) and vertical speed (VRT) hold.
When coupled to the Garmin GNS-530, SAS and NAV modes, along with
one or the other vertical hold commands, directs the aircraft along
published instrument approaches. Once again, power and yaw inputs
are pilot-controlled. In SAS mode, the system takes an "electronic
picture" of the cyclic's position, as sensed by the pitch and roll
servo arms at the time of activation. HeliSAS then keeps the cyclic
in that position until the SAS function is disengaged by on/off
buttons on the control panel, or either one of the cyclic grips.
Cobham says it is so precise, it will even hold a fairly stable
Should the pilot change the position of the cyclic slightly,
HeliSAS assumes it is inadvertent, and returns the cyclic to its
original orientation. But if the cyclic is moved to a greater
degree, the SAS will assume that the pilot is executing an evasive
maneuver and disengage, thus immediately restoring full control to
SAS is also designed with the ability to recover the aircraft
from an unusual attitude. If the pilot should become disoriented,
HeliSAS will gently return the aircraft to straight and level
flight, power permitting.
HeliSAS requires physical attachment between the two servos and
the tubes that connect the cyclic to the pitch and roll actuators.
Engineers solved this requirement by mounting the 3.4-lb pitch and
roll servos under the front seats, and attaching them to the cyclic
control tubes with connecting rods. The HeliSAS computer then
marries the system to the aircraft's avionics.
At 15 lbs total, HeliSAS does not create a significant weight
and balance issue. In fact, it was designed with light helicopters,
such as the Bell Jet Ranger and Robinson R44, in mind. And while a
price for the unit is not yet firm, Cobham plans to keep
acquisition costs well below $75,000, and installation time around