For each airspeed indicating system, the following apply:
(a) Each airspeed indicating instrument must be calibrated to indicate
true airspeed (at sea level with a standard atmosphere) with a minimum
practicable instrument calibration error when the corresponding pitot and
static pressures are applied.
(b) Each system must be calibrated to determine system error excluding
airspeed instrument error. This calibration must be determined --
(1) In level flight at speeds of 20 knots and greater, and over an
appropriate range of speeds for flight conditions of climb and
(2) During takeoff, with repeatable and readable indications that
(i) Consistent realization of the field lengths specified in the
Rotorcraft Flight Manual; and
(ii) Avoidance of the critical areas of the height-velocity envelope as
established under §29.87.
(c) For Category A rotorcraft --
(1) The indication must allow consistent definition of the takeoff
decision point; and
(2) The system error, excluding the airspeed instrument calibration
error, may not exceed --
(i) Three percent or 5 knots, whichever is greater, in level flight at
speeds above 80 percent of takeoff safety speed; and
(ii) Ten knots in climb at speeds from 10 knots below takeoff safety
speed to 10 knots above VY.
(d) For Category B rotorcraft, the system error, excluding the airspeed
instrument calibration error, may not exceed 3 percent or 5 knots,
whichever is greater, in level flight at speeds above 80 percent of the
climbout speed attained at 50 feet when complying with §29.63.
(e) Each system must be arranged, so far as practicable, to prevent
malfunction or serious error due to the entry of moisture, dirt, or other
(f) Each system must have a heated pitot tube or an equivalent means of
preventing malfunction due to icing.