706 

14 CFR Ch. I (1–1–19 Edition) 

§ 33.29 

demonstrate by test or other accept-
able means that the overspeed function 
remains available between inspection 
and maintenance periods. 

(g) 

Software. 

The applicant must de-

sign, implement, and verify all associ-
ated software to minimize the exist-
ence of errors by using a method, ap-
proved by the FAA, consistent with the 
criticality of the performed functions. 

(h) 

Aircraft-supplied data. 

Single fail-

ures leading to loss, interruption or 
corruption of aircraft-supplied data 
(other than thrust or power command 
signals from the aircraft), or data 
shared between engines must: 

(1) Not result in a hazardous engine 

effect for any engine; and 

(2) Be detected and accommodated. 

The accommodation strategy must not 
result in an unacceptable change in 
thrust or power or an unacceptable 
change in engine operating and start-
ing characteristics. The applicant must 
evaluate and document in the engine 
installation instructions the effects of 
these failures on engine power or 
thrust, engine operability, and starting 
characteristics throughout the flight 
envelope. 

(i) 

Aircraft-supplied electrical power. 

(1) 

The applicant must design the engine 
control system so that the loss, mal-
function, or interruption of electrical 
power supplied from the aircraft to the 
engine control system will not result 
in any of the following: 

(i) A hazardous engine effect, or 
(ii) The unacceptable transmission of 

erroneous data. 

(2) When an engine dedicated power 

source is required for compliance with 
paragraph (i)(1) of this section, its ca-
pacity should provide sufficient margin 
to account for engine operation below 
idle where the engine control system is 
designed and expected to recover en-
gine operation automatically. 

(3) The applicant must identify and 

declare the need for, and the character-
istics of, any electrical power supplied 
from the aircraft to the engine control 
system for starting and operating the 
engine, including transient and steady 
state voltage limits, in the engine in-
structions for installation. 

(4) Low voltage transients outside 

the power supply voltage limitations 
declared in paragraph (i)(3) of this sec-

tion must meet the requirements of 
paragraph (i)(1) of this section. The en-
gine control system must be capable of 
resuming normal operation when air-
craft-supplied power returns to within 
the declared limits. 

(j) 

Air pressure signal. 

The applicant 

must consider the effects of blockage 
or leakage of the signal lines on the en-
gine control system as part of the Sys-
tem Safety Assessment of paragraph 
(e) of this section and must adopt the 
appropriate design precautions. 

(k) 

Automatic availability and control 

of engine power for 30-second OEI rating. 

Rotorcraft engines having a 30-second 
OEI rating must incorporate a means, 
or a provision for a means, for auto-
matic availability and automatic con-
trol of the 30-second OEI power within 
its operating limitations. 

(l) 

Engine shut down means. 

Means 

must be provided for shutting down the 
engine rapidly. 

(m) 

Programmable logic devices. 

The 

development of programmable logic de-
vices using digital logic or other com-
plex design technologies must provide 
a level of assurance for the encoded 
logic commensurate with the hazard 
associated with the failure or malfunc-
tion of the systems in which the de-
vices are located. The applicant must 
provide evidence that the development 
of these devices has been done by using 
a method, approved by the FAA, that is 
consistent with the criticality of the 
performed function. 

[Amdt. 33–26, 73 FR 48284, Aug. 19, 2008] 

§ 33.29

Instrument connection. 

(a) Unless it is constructed to pre-

vent its connection to an incorrect in-
strument, each connection provided for 
powerplant instruments required by 
aircraft airworthiness regulations or 
necessary to insure operation of the en-
gine in compliance with any engine 
limitation must be marked to identify 
it with its corresponding instrument. 

(b) A connection must be provided on 

each turbojet engine for an indicator 
system to indicate rotor system unbal-
ance. 

(c) Each rotorcraft turbine engine 

having a 30-second OEI rating and a 2- 
minute OEI rating must have a means 
or a provision for a means to: 

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