550 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.1327 

the alternate static pressure system, 
differs from the reading of the altim-
eter when on the primary static system 
by more than 50 feet, a correction card 
must be provided for the alternate 
static system. 

(c) Except as provided in paragraph 

(d) of this section, if the static pressure 
system incorporates both a primary 
and an alternate static pressure source, 
the means for selecting one or the 
other source must be designed so 
that— 

(1) When either source is selected, the 

other is blocked off; and 

(2) Both sources cannot be blocked 

off simultaneously. 

(d) For unpressurized rotorcraft, 

paragraph (c)(1) of this section does not 
apply if it can be demonstrated that 
the static pressure system calibration, 
when either static pressure source is 
selected is not changed by the other 
static pressure source being open or 
blocked. 

(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral Aviation Act of 1958 (49 U.S.C. 1354(a), 
1421, 1423, 1424, and 1425); and sec. 6(c) of the 
Dept. of Transportation Act (49 U.S.C. 
1655(c))) 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–13, 42 FR 36972, July 18, 
1977] 

§ 27.1327

Magnetic direction indicator. 

(a) Except as provided in paragraph 

(b) of this section— 

(1) Each magnetic direction indicator 

must be installed so that its accuracy 
is not excessively affected by the 
rotorcraft’s vibration or magnetic 
fields; and 

(2) The compensated installation may 

not have a deviation, in level flight, 
greater than 10 degrees on any heading. 

(b) A magnetic nonstabilized direc-

tion indicator may deviate more than 
10 degrees due to the operation of elec-
trically powered systems such as elec-
trically heated windshields if either a 
magnetic stabilized direction indi-
cator, which does not have a deviation 
in level flight greater than 10 degrees 
on any heading, or a gyroscopic direc-
tion indicator, is installed. Deviations 
of a magnetic nonstabilized direction 
indicator of more than 10 degrees must 

be placarded in accordance with 
§ 27.1547(e). 

(Secs. 313(a), 601, 603, 604, and 605 of the Fed-
eral Aviation Act of 1958 (49 U.S.C. 1354(a), 
1421, 1423, 1424, and 1425); and sec. 6(c) of the 
Dept. of Transportation Act (49 U.S.C. 
1655(c))) 

[Amdt. 27–13, 42 FR 36972, July 18, 1977] 

§ 27.1329

Automatic pilot and flight 

guidance system. 

For the purpose of this subpart, an 

automatic pilot and flight guidance 
system may consist of an autopilot, 
flight director, or a component that 
interacts with stability augmentation 
or trim. 

(a) Each automatic pilot and flight 

guidance system must be designed so 
that it: 

(1) Can be overpowered by one pilot 

to allow control of the rotorcraft; 

(2) Provides a means to disengage the 

system, or any malfunctioning compo-
nent of the system, by each pilot to 
prevent it from interfering with the 
control of the rotorcraft; and 

(3) Provides a means to indicate to 

the flight crew its current mode of op-
eration. Selector switch position is not 
acceptable as a means of indication. 

(b) Unless there is automatic syn-

chronization, each system must have a 
means to readily indicate to the pilot 
the alignment of the actuating device 
in relation to the control system it op-
erates. 

(c) Each manually operated control 

for the system’s operation must be 
readily accessible to the pilots. 

(d) The system must be designed so 

that, within the range of adjustment 
available to the pilot, it cannot 
produce hazardous loads on the rotor-
craft, or create hazardous deviations in 
the flight path, under any flight condi-
tion appropriate to its use or in the 
event of a malfunction, assuming that 
corrective action begins within a rea-
sonable period of time. 

(e) If the automatic pilot and flight 

guidance system integrates signals 
from auxiliary controls or furnishes 
signals for operation of other equip-
ment, there must be a means to pre-
vent improper operation. 

(f) If the automatic pilot system can 

be coupled to airborne navigation 
equipment, means must be provided to 

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