522 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 135, App. A 

(a) There must be a fuel strainer or filter 

between the tank outlet and the fuel meter-
ing device of the engine. In addition, the fuel 
strainer or filter must be— 

(1) Between the tank outlet and the en-

gine-driven positive displacement pump 
inlet, if there is an engine-driven positive 
displacement pump; 

(2) Accessible for drainage and cleaning 

and, for the strainer screen, easily remov-
able; and 

(3) Mounted so that its weight is not sup-

ported by the connecting lines or by the 
inlet or outlet connections of the strainer or 
filter itself. 

(b) Unless there are means in the fuel sys-

tem to prevent the accumulation of ice on 
the filter, there must be means to automati-
cally maintain the fuel-flow if ice-clogging 
of the filter occurs; and 

(c) The fuel strainer or filter must be of 

adequate capacity (for operating limitations 
established to ensure proper service) and of 
appropriate mesh to insure proper engine op-
eration, with the fuel contaminated to a de-
gree (for particle size and density) that can 
be reasonably expected in service. The de-
gree of fuel filtering may not be less than 
that established for the engine type certifi-
cation. 

45. 

Lightning strike protection. 

Protection 

must be provided against the ignition of 
flammable vapors in the fuel vent system 
due to lightning strikes. 

Cooling 

46. 

Cooling test procedures for turbopropeller 

powered airplanes. 

(a) Turbopropeller powered 

airplanes must be shown to comply with 
FAR 23.1041 during takeoff, climb, en route, 
and landing stages of flight that correspond 
to the applicable performance requirements. 
The cooling tests must be conducted with 
the airplane in the configuration, and oper-
ating under the conditions that are critical 
relative to cooling during each stage of 
flight. For the cooling tests a temperature is 
‘‘stabilized’’ when its rate of change is less 
than 2 

°

F. per minute. 

(b) Temperatures must be stabilized under 

the conditions from which entry is made into 
each stage of flight being investigated unless 
the entry condition is not one during which 
component and engine fluid temperatures 
would stabilize, in which case, operation 
through the full entry condition must be 
conducted before entry into the stage of 
flight being investigated to allow tempera-
tures to reach their natural levels at the 
time of entry. The takeoff cooling test must 
be preceded by a period during which the 
powerplant component and engine fluid tem-
peratures are stabilized with the engines at 
ground idle. 

(c) Cooling tests for each stage of flight 

must be continued until— 

(1) The component and engine fluid tem-

peratures stabilize; 

(2) The stage of flight is completed; or 
(3) An operating limitation is reached. 

Induction System 

47. 

Air induction. 

For turbopropeller pow-

ered airplanes— 

(a) There must be means to prevent haz-

ardous quantities of fuel leakage or overflow 
from drains, vents, or other components of 
flammable fluid systems from entering the 
engine intake systems; and 

(b) The air inlet ducts must be located or 

protected so as to minimize the ingestion of 
foreign matter during takeoff, landing, and 
taxiing. 

48. 

Induction system icing protection. 

For 

turbopropeller powered airplanes, each tur-
bine engine must be able to operate through-
out its flight power range without adverse 
effect on engine operation or serious loss of 
power or thrust, under the icing conditions 
specified in appendix C of part 25 of this 
chapter. In addition, there must be means to 
indicate to appropriate flight crewmembers 
the functioning of the powerplant ice protec-
tion system. 

49. 

Turbine engine bleed air systems. 

Turbine 

engine bleed air systems of turbopropeller 
powered airplanes must be investigated to 
determine— 

(a) That no hazard to the airplane will re-

sult if a duct rupture occurs. This condition 
must consider that a failure of the duct can 
occur anywhere between the engine port and 
the airplane bleed service; and 

(b) That, if the bleed air system is used for 

direct cabin pressurization, it is not possible 
for hazardous contamination of the cabin air 
system to occur in event of lubrication sys-
tem failure. 

Exhaust System 

50. 

Exhaust system drains. 

Turbopropeller 

engine exhaust systems having low spots or 
pockets must incorporate drains at those lo-
cations. These drains must discharge clear of 
the airplane in normal and ground attitudes 
to prevent the accumulation of fuel after the 
failure of an attempted engine start. 

Powerplant Controls and Accessories 

51. 

Engine controls. 

If throttles or power le-

vers for turbopropeller powered airplanes are 
such that any position of these controls will 
reduce the fuel flow to the engine(s) below 
that necessary for satisfactory and safe idle 
operation of the engine while the airplane is 
in flight, a means must be provided to pre-
vent inadvertent movement of the control 
into this position. The means provided must 
incorporate a positive lock or stop at this 
idle position and must require a separate and 
distinct operation by the crew to displace 

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