551 

Federal Aviation Administration, DOT 

§ 27.1351 

indicate to the pilots the current mode 
of operation. Selector switch position 
is not acceptable as a means of indica-
tion. 

[Amdt. 27–21, 49 FR 44435, Nov. 6, 1984, as 
amended by Amdt. 27–35, 63 FR 43285, Aug. 12, 
1998; Amdt. 27–51, 88 FR 8738, Feb. 10, 2023] 

§ 27.1337

Powerplant instruments. 

(a) 

Instruments and instrument lines. 

(1) Each powerplant instrument line 
must meet the requirements of §§ 27.- 
961 and 27.993. 

(2) Each line carrying flammable 

fluids under pressure must— 

(i) Have restricting orifices or other 

safety devices at the source of pressure 
to prevent the escape of excessive fluid 
if the line fails; and 

(ii) Be installed and located so that 

the escape of fluids would not create a 
hazard. 

(3) Each powerplant instrument that 

utilizes flammable fluids must be in-
stalled and located so that the escape 
of fluid would not create a hazard. 

(b) 

Fuel quantity indicator. Each fuel 

quantity indicator must be installed to 
clearly indicate to the flight crew the 
quantity of fuel in each tank in flight. 
In addition— 

(1) Each fuel quantity indicator must 

be calibrated to read ‘‘zero’’ during 
level flight when the quantity of fuel 
remaining in the tank is equal to the 
unusable fuel supply determined under 
§ 27.959; 

(2) When two or more tanks are close-

ly interconnected by a gravity feed sys-
tem and vented, and when it is impos-
sible to feed from each tank sepa-
rately, at least one fuel quantity indi-
cator must be installed; and 

(3) Each exposed sight gauge used as 

a fuel quantity indicator must be pro-
tected against damage. 

(c) 

Fuel flowmeter system. If a fuel 

flowmeter system is installed, each 
metering component must have a 
means for bypassing the fuel supply if 
malfunction of that component se-
verely restricts fuel flow. 

(d) 

Oil quantity indicator. There must 

be means to indicate the quantity of 
oil in each tank— 

(1) On the ground (including during 

the filling of each tank); and 

(2) In flight, if there is an oil transfer 

system or reserve oil supply system. 

(e) Rotor drive system transmissions 

and gearboxes utilizing ferromagnetic 
materials must be equipped with chip 
detectors designed to indicate the pres-
ence of ferromagnetic particles result-
ing from damage or excessive wear. 
Chip detectors must— 

(1) Be designed to provide a signal to 

the device required by § 27.1305(v) and 
be provided with a means to allow 
crewmembers to check, in flight, the 
function of each detector electrical cir-
cuit and signal. 

(2) [Reserved] 

(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49 
U.S.C. 1354(a), 1421, and 1423; sec. 6(c) 49 
U.S.C. 1655(c)) 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–12, 42 FR 15046, Mar. 17, 
1977; Amdt. 27–23, 53 FR 34214, Sept. 2, 1988; 
Amdt. 27–37, 64 FR 45095, Aug. 18, 1999] 

E

LECTRICAL

S

YSTEMS AND

E

QUIPMENT

 

§ 27.1351

General. 

(a) 

Electrical system capacity. Elec-

trical equipment must be adequate for 
its intended use. In addition— 

(1) Electric power sources, their 

transmission cables, and their associ-
ated control and protective devices 
must be able to furnish the required 
power at the proper voltage to each 
load circuit essential for safe oper-
ation; and 

(2) Compliance with paragraph (a)(1) 

of this section must be shown by an 
electrical load analysis, or by elec-
trical measurements that take into ac-
count the electrical loads applied to 
the electrical system, in probable com-
binations and for probable durations. 

(b) 

Function.  For each electrical sys-

tem, the following apply: 

(1) Each system, when installed, 

must be— 

(i) Free from hazards in itself, in its 

method of operation, and in its effects 
on other parts of the rotorcraft; and 

(ii) Protected from fuel, oil, water, 

other detrimental substances, and me-
chanical damage. 

(2) Electric power sources must func-

tion properly when connected in com-
bination or independently. 

(3) No failure or malfunction of any 

source may impair the ability of any 
remaining source to supply load cir-
cuits essential for safe operation. 

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