521 

Federal Aviation Administration, DOT 

Pt. 135, App. A 

must be provided in the Airplane Flight 
Manual. 

38. 

Engines. 

(a) 

For turbopropeller powered 

airplanes. 

The engine installation must com-

ply with the following: 

(1) 

Engine isolation. 

The powerplants must 

be arranged and isolated from each other to 
allow operation, in at least one configura-
tion, so that the failure or malfunction of 
any engine, or of any system that can affect 
the engine, will not— 

(i) Prevent the continued safe operation of 

the remaining engines; or 

(ii) Require immediate action by any crew-

member for continued safe operation. 

(2) 

Control of engine rotation. 

There must be 

a means to individually stop and restart the 
rotation of any engine in flight except that 
engine rotation need not be stopped if con-
tinued rotation could not jeopardize the safe-
ty of the airplane. Each component of the 
stopping and restarting system on the engine 
side of the firewall, and that might be ex-
posed to fire, must be at least fire resistant. 
If hydraulic propeller feathering systems are 
used for this purpose, the feathering lines 
must be at least fire resistant under the op-
erating conditions that may be expected to 
exist during feathering. 

(3) 

Engine speed and gas temperature control 

devices. 

The powerplant systems associated 

with engine control devices, systems, and in-
strumentation must provide reasonable as-
surance that those engine operating limita-
tions that adversely affect turbine rotor 
structural integrity will not be exceeded in 
service. 

(b) 

For reciprocating engine powered air-

planes. 

To provide engine isolation, the pow-

erplants must be arranged and isolated from 
each other to allow operation, in at least one 
configuration, so that the failure or malfunc-
tion of any engine, or of any system that can 
affect that engine, will not— 

(1) Prevent the continued safe operation of 

the remaining engines; or 

(2) Require immediate action by any crew-

member for continued safe operation. 

39. 

Turbopropeller reversing systems. 

(a) Tur-

bopropeller reversing systems intended for 
ground operation must be designed so that 
no single failure or malfunction of the sys-
tem will result in unwanted reverse thrust 
under any expected operating condition. 
Failure of structural elements need not be 
considered if the probability of this kind of 
failure is extremely remote. 

(b) Turbopropeller reversing systems in-

tended for in flight use must be designed so 
that no unsafe condition will result during 
normal operation of the system, or from any 
failure (or reasonably likely combination of 
failures) of the reversing system, under any 
anticipated condition of operation of the air-
plane. Failure of structural elements need 
not be considered if the probability of this 
kind of failure is extremely remote. 

(c) Compliance with this section may be 

shown by failure analysis, testing, or both 
for propeller systems that allow propeller 
blades to move from the flight low-pitch po-
sition to a position that is substantially less 
than that at the normal flight low-pitch stop 
position. The analysis may include or be sup-
ported by the analysis made to show compli-
ance with the type certification of the pro-
peller and associated installation compo-
nents. Credit will be given for pertinent 
analysis and testing completed by the engine 
and propeller manufacturers. 

40. 

Turbopropeller drag-limiting systems. 

Tur-

bopropeller drag-limiting systems must be 
designed so that no single failure or malfunc-
tion of any of the systems during normal or 
emergency operation results in propeller 
drag in excess of that for which the airplane 
was designed. Failure of structural elements 
of the drag-limiting systems need not be con-
sidered if the probability of this kind of fail-
ure is extremely remote. 

41. 

Turbine engine powerplant operating 

characteristics. 

For turbopropeller powered 

airplanes, the turbine engine powerplant op-
erating characteristics must be investigated 
in flight to determine that no adverse char-
acteristics (such as stall, surge, or flameout) 
are present to a hazardous degree, during 
normal and emergency operation within the 
range of operating limitations of the air-
plane and of the engine. 

42. 

Fuel flow. 

(a) For turbopropeller pow-

ered airplanes— 

(1) The fuel system must provide for con-

tinuous supply of fuel to the engines for nor-
mal operation without interruption due to 
depletion of fuel in any tank other than the 
main tank; and 

(2) The fuel flow rate for turbopropeller en-

gine fuel pump systems must not be less 
than 125 percent of the fuel flow required to 
develop the standard sea level atmospheric 
conditions takeoff power selected and in-
cluded as an operating limitation in the Air-
plane Flight Manual. 

(b) For reciprocating engine powered air-

planes, it is acceptable for the fuel flow rate 
for each pump system (main and reserve sup-
ply) to be 125 percent of the takeoff fuel con-
sumption of the engine. 

Fuel System Components 

43. 

Fuel pumps. 

For turbopropeller powered 

airplanes, a reliable and independent power 
source must be provided for each pump used 
with turbine engines which do not have pro-
visions for mechanically driving the main 
pumps. It must be demonstrated that the 
pump installations provide a reliability and 
durability equivalent to that in FAR 
23.991(a). 

44. 

Fuel strainer or filter. 

For turbopropeller 

powered airplanes, the following apply: 

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