549 

Federal Aviation Administration, DOT 

§ 27.1325 

prevent the continued safe flight and 
landing of a rotorcraft may be designed 
and installed without meeting the pro-
visions of paragraph (a) provided— 

(1) The system has previously been 

shown to comply with special condi-
tions for HIRF, prescribed under § 21.16, 
issued before December 1, 2007; 

(2) The HIRF immunity characteris-

tics of the system have not changed 
since compliance with the special con-
ditions was demonstrated; and 

(3) The data used to demonstrate 

compliance with the special conditions 
is provided. 

[Doc. No. FAA–2006–23657, 72 FR 44026, Aug. 6, 
2007] 

I

NSTRUMENTS

: I

NSTALLATION

 

§ 27.1321

Arrangement and visibility. 

(a) Each flight, navigation, and pow-

erplant instrument for use by any pilot 
must be easily visible to him. 

(b) For each multiengine rotorcraft, 

identical powerplant instruments must 
be located so as to prevent confusion as 
to which engine each instrument re-
lates. 

(c) Instrument panel vibration may 

not damage, or impair the readability 
or accuracy of, any instrument. 

(d) If a visual indicator is provided to 

indicate malfunction of an instrument, 
it must be effective under all probable 
cockpit lighting conditions. 

(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; 29 
FR 17885, Dec. 17, 1964, as amended by Amdt. 
27–13, 42 FR 36971, July 18, 1977] 

§ 27.1322

Warning, caution, and advi-

sory lights. 

If warning, caution or advisory lights 

are installed in the cockpit, they must, 
unless otherwise approved by the Ad-
ministrator, be— 

(a) Red, for warning lights (lights in-

dicating a hazard which may require 
immediate corrective action): 

(b) Amber, for caution lights (lights 

indicating the possible need for future 
corrective action); 

(c) Green, for safe operation lights; 

and 

(d) Any other color, including white, 

for lights not described in paragraphs 
(a) through (c) of this section, provided 
the color differs sufficiently from the 
colors prescribed in paragraphs (a) 
through (c) of this section to avoid pos-
sible confusion. 

[Amdt. 27–11, 41 FR 55470, Dec. 20, 1976] 

§ 27.1323

Airspeed indicating system. 

(a) Each airspeed indicating instru-

ment must be calibrated to indicate 
true airspeed (at sea level with a stand-
ard atmosphere) with a minimum prac-
ticable instrument calibration error 
when the corresponding pitot and stat-
ic pressures are applied. 

(b) The airspeed indicating system 

must be calibrated in flight at forward 
speeds of 20 knots and over. 

(c) At each forward speed above 80 

percent of the climbout speed, the air-
speed indicator must indicate true air-
speed, at sea level with a standard at-
mosphere, to within an allowable in-
stallation error of not more than the 
greater of— 

(1) 

±

3 percent of the calibrated air-

speed; or 

(2) Five knots. 

(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] 

§ 27.1325

Static pressure systems. 

(a) Each instrument with static air 

case connections must be vented so 
that the influence of rotorcraft speed, 
the opening and closing of windows, 
airflow variation, and moisture or 
other foreign matter does not seriously 
affect its accuracy. 

(b) Each static pressure port must be 

designed and located in such manner 
that the correlation between air pres-
sure in the static pressure system and 
true ambient atmospheric static pres-
sure is not altered when the rotorcraft 
encounters icing conditions. An anti- 
icing means or an alternate source of 
static pressure may be used in showing 
compliance with this requirement. If 
the reading of the altimeter, when on 

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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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