278 

14 CFR Ch. I (1–1–19 Edition) 

§ 25.773 

(b) 

Precipitation conditions. 

For pre-

cipitation conditions, the following 
apply: 

(1) The airplane must have a means 

to maintain a clear portion of the 
windshield, during precipitation condi-
tions, sufficient for both pilots to have 
a sufficiently extensive view along the 
flight path in normal flight attitudes 
of the airplane. This means must be de-
signed to function, without continuous 
attention on the part of the crew, in— 

(i) Heavy rain at speeds up to 1.5 V

SR1

 

with lift and drag devices retracted; 
and 

(ii) The icing conditions specified in 

Appendix C of this part and the fol-
lowing icing conditions specified in Ap-
pendix O of this part, if certification 
for flight in icing conditions is sought: 

(A) For airplanes certificated in ac-

cordance with § 25.1420(a)(1), the icing 
conditions that the airplane is certified 
to safely exit following detection. 

(B) For airplanes certificated in ac-

cordance with § 25.1420(a)(2), the icing 
conditions that the airplane is certified 
to safely operate in and the icing con-
ditions that the airplane is certified to 
safely exit following detection. 

(C) For airplanes certificated in ac-

cordance with § 25.1420(a)(3) and for air-
planes not subject to § 25.1420, all icing 
conditions. 

(2) No single failure of the systems 

used to provide the view required by 
paragraph (b)(1) of this section must 
cause the loss of that view by both pi-
lots in the specified precipitation con-
ditions. 

(3) The first pilot must have a win-

dow that— 

(i) Is openable under the conditions 

prescribed in paragraph (b)(1) of this 
section when the cabin is not pressur-
ized; 

(ii) Provides the view specified in 

paragraph (b)(1) of this section; and 

(iii) Provides sufficient protection 

from the elements against impairment 
of the pilot’s vision. 

(4) The openable window specified in 

paragraph (b)(3) of this section need 
not be provided if it is shown that an 
area of the transparent surface will re-
main clear sufficient for at least one 
pilot to land the airplane safely in the 
event of— 

(i) Any system failure or combina-

tion of failures which is not extremely 
improbable, in accordance with 
§ 25.1309, under the precipitation condi-
tions specified in paragraph (b)(1) of 
this section. 

(ii) An encounter with severe hail, 

birds, or insects. 

(c) 

Internal windshield and window 

fogging. 

The airplane must have a 

means to prevent fogging of the inter-
nal portions of the windshield and win-
dow panels over an area which would 
provide the visibility specified in para-
graph (a) of this section under all in-
ternal and external ambient condi-
tions, including precipitation condi-
tions, in which the airplane is intended 
to be operated. 

(d) Fixed markers or other guides 

must be installed at each pilot station 
to enable the pilots to position them-
selves in their seats for an optimum 
combination of outside visibility and 
instrument scan. If lighted markers or 
guides are used they must comply with 
the requirements specified in § 25.1381. 

(e) 

Vision systems with transparent dis-

plays. 

A vision system with a trans-

parent display surface located in the 
pilot’s outside field of view, such as a 
head up-display, head mounted display, 
or other equivalent display, must meet 
the following requirements in non-
precipitation and precipitation condi-
tions: 

(1) While the vision system display is 

in operation, it must compensate for 
interference with the pilot’s outside 
field of view such that the combination 
of what is visible in the display and 
what remains visible through and 
around it, enables the pilot to perform 
the maneuvers and normal duties of 
paragraph (a) of this section. 

(2) The pilot’s view of the external 

scene may not be distorted by the 
transparent display surface or by the 
vision system imagery. When the vi-
sion system displays imagery or any 
symbology that is referenced to the im-
agery and outside scene topography, 
including attitude symbology, flight 
path vector, and flight path angle ref-
erence cue, that imagery and sym-
bology must be aligned with, and 
scaled to, the external scene. 

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