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353 

Federal Aviation Administration, DOT 

§ 25.1397 

the minimum intensity prescribed in 
§ 25.1391 for the corresponding angles in 
the horizontal plane. 

(3) 

Intensities in overlaps between adja-

cent signals. No intensity in any over-
lap between adjacent signals may ex-
ceed the values given in § 25.1395, except 
that higher intensities in overlaps may 
be used with main beam intensities 
substantially greater than the minima 
specified in §§ 25.1391 and 25.1393 if the 
overlap intensities in relation to the 
main beam intensities do not adversely 
affect signal clarity. When the peak in-
tensity of the forward position lights is 
more than 100 candles, the maximum 
overlap intensities between them may 
exceed the values given in § 25.1395 if 
the overlap intensity in Area A is not 
more than 10 percent of peak position 
light intensity and the overlap inten-
sity in Area B is not greater than 2.5 
percent of peak position light inten-
sity. 

§ 25.1391

Minimum intensities in the 

horizontal plane of forward and 
rear position lights. 

Each position light intensity must 

equal or exceed the applicable values in 
the following table: 

Dihedral angle (light in-

cluded) 

Angle from right 

or left of longitu-

dinal axis, meas-

ured from dead 

ahead 

Intensity 

(candles) 

and (forward red and 

green).

0

° 

to 10

°

..............

10

° 

to 20

°

............

20

° 

to 110

°

..........

40 
30 

A (rear white) .....................

110

° 

to 180

°

........

20 

§ 25.1393

Minimum intensities in any 

vertical plane of forward and rear 
position lights. 

Each position light intensity must 

equal or exceed the applicable values in 
the following table: 

Angle above or below the horizontal plane 

Intensity, 

0

°

.........................................................................

1.00 

0

° 

to 5

°

................................................................

0.90 

5

° 

to 10

°

..............................................................

0.80 

10

° 

to 15

°

............................................................

0.70 

15

° 

to 20

°

............................................................

0.50 

20

° 

to 30

°

............................................................

0.30 

30

° 

to 40

°

............................................................

0.10 

40

° 

to 90

°

............................................................

0.05 

§ 25.1395

Maximum intensities in over-

lapping beams of forward and rear 
position lights. 

No position light intensity may ex-

ceed the applicable values in the fol-
lowing table, except as provided in 
§ 25.1389(b)(3). 

Overlaps 

Maximum intensity 

Area A 

(candles) 

Area B 

(candles) 

Green in dihedral angle .............

10 1 

Red in dihedral angle ................

10 1 

Green in dihedral angle .............

5 1 

Red in dihedral angle ................

5 1 

Rear white in dihedral angle ......

5 1 

Rear white in dihedral angle .....

5 1 

Where— 

(a) Area A includes all directions in 

the adjacent dihedral angle that pass 
through the light source and intersect 
the common boundary plane at more 
than 10 degrees but less than 20 de-
grees; and 

(b) Area B includes all directions in 

the adjacent dihedral angle that pass 
through the light source and intersect 
the common boundary plane at more 
than 20 degrees. 

§ 25.1397

Color specifications. 

Each position light color must have 

the applicable International Commis-
sion on Illumination chromaticity co-
ordinates as follows: 

(a) 

Aviation red— 

is not greater than 0.335; and 
is not greater than 0.002. 

(b) 

Aviation green— 

is not greater than 0.440

¥

0.320

is not greater than y

¥

0.170; and 

is not less than 0.390

¥

0.170

x

(c) 

Aviation white— 

x  is not less than 0.300 and not greater than 

0.540; 

is not less than x

¥

0.040; or 

y

0

¥

0.010, which-

ever is the smaller; and 

y  is not greater than x  + 0.020 nor 

0.636

¥

0.400

x

Where 

y

0

is the 

coordinate of the Planckian 

radiator for the value of 

considered. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–27, 36 FR 12972, July 10, 
1971] 

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