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14 CFR Ch. I (1–1–18 Edition) 

§ 1.1 

Unless otherwise stated, the critical al-
titude is the maximum altitude at 
which it is possible to maintain, at the 
maximum continuous rotational speed, 
one of the following: 

(1) The maximum continuous power, 

in the case of engines for which this 
power rating is the same at sea level 
and at the rated altitude. 

(2) The maximum continuous rated 

manifold pressure, in the case of en-
gines, the maximum continuous power 
of which is governed by a constant 
manifold pressure. 

Critical engine means the engine 

whose failure would most adversely af-
fect the performance or handling quali-
ties of an aircraft. 

Decision altitude (DA) is a specified al-

titude in an instrument approach pro-
cedure at which the pilot must decide 
whether to initiate an immediate 
missed approach if the pilot does not 
see the required visual reference, or to 
continue the approach. Decision alti-
tude is expressed in feet above mean 
sea level. 

Decision height (DH) is a specified 

height above the ground in an instru-
ment approach procedure at which the 
pilot must decide whether to initiate 
an immediate missed approach if the 
pilot does not see the required visual 
reference, or to continue the approach. 
Decision height is expressed in feet 
above ground level. 

Early ETOPS means ETOPS type de-

sign approval obtained without gaining 
non-ETOPS service experience on the 
candidate airplane-engine combination 
certified for ETOPS. 

EFVS operation means an operation in 

which visibility conditions require an 
EFVS to be used in lieu of natural vi-
sion to perform an approach or landing, 
determine enhanced flight visibility, 
identify required visual references, or 
conduct a rollout. 

Enhanced flight visibility (EFV) means 

the average forward horizontal dis-
tance, from the cockpit of an aircraft 
in flight, at which prominent topo-
graphical objects may be clearly dis-
tinguished and identified by day or 
night by a pilot using an enhanced 
flight vision system. 

Enhanced flight vision system (EFVS) 

means an installed aircraft system 
which uses an electronic means to pro-

vide a display of the forward external 
scene topography (the natural or man-
made features of a place or region espe-
cially in a way to show their relative 
positions and elevation) through the 
use of imaging sensors, including but 
not limited to forward-looking infra-
red, millimeter wave radiometry, milli-
meter wave radar, or low-light level 
image intensification. An EFVS in-
cludes the display element, sensors, 
computers and power supplies, indica-
tions, and controls. 

Equivalent airspeed means the cali-

brated airspeed of an aircraft corrected 
for adiabatic compressible flow for the 
particular altitude. Equivalent air-
speed is equal to calibrated airspeed in 
standard atmosphere at sea level. 

ETOPS Significant System means an 

airplane system, including the propul-
sion system, the failure or malfunc-
tioning of which could adversely affect 
the safety of an ETOPS flight, or the 
continued safe flight and landing of an 
airplane during an ETOPS diversion. 
Each ETOPS significant system is ei-
ther an ETOPS group 1 significant sys-
tem or an ETOPS group 2 significant 

(1) An ETOPS group 1 Significant 


(i) Has fail-safe characteristics di-

rectly linked to the degree of redun-
dancy provided by the number of en-
gines on the airplane. 

(ii) Is a system, the failure or mal-

function of which could result in an 
IFSD, loss of thrust control, or other 
power loss. 

(iii) Contributes significantly to the 

safety of an ETOPS diversion by pro-
viding additional redundancy for any 
system power source lost as a result of 
an inoperative engine. 

(iv) Is essential for prolonged oper-

ation of an airplane at engine inoper-
ative altitudes. 

(2) An ETOPS group 2 significant sys-

tem is an ETOPS significant system 
that is not an ETOPS group 1 signifi-
cant system. 

Extended Operations (ETOPS) means 

an airplane flight operation, other than 
an all-cargo operation in an airplane 
with more than two engines, during 

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