Lights

§ 23.1383   Taxi and landing lights.

Each taxi and landing light must be designed and installed so that:

(a) No dangerous glare is visible to the pilots.

(b) The pilot is not seriously affected by halation.

(c) It provides enough light for night operations.

(d) It does not cause a fire hazard in any configuration.

[Doc. No. 27806, 61 FR 5169, Feb. 9, 1996]

Applies to: GS-Air LED-003 – "Belly" strobe and LED taxi light unit.

Paragraph a. and b. are satisfied by installing the unit under the fuselage, in such a location as not to interfere with the pilot's vision.

Paragraph c. lends itself to variable interpretation. In August 2004, the Chicago Flight Standard District Office has provided GS-Air with this general rule: The builder of an experimental aircraft is the de-facto manufacturer of the aircraft itself. As such, he is responsible for writing the Operating Limitation paragraph, which is integral part of the aircraft Airworthiness Certificate. He is therefore responsible for determining whether the aircraft is appropriately equipped for its intended use and must so state in the Operating Limitation paragraph.

GS-Air LED-003 units contains 12 "cold" white, narrow beam LEDs, each with a 25-candle output, for a total of 300 candles (straight ahead). All the LEDs are parallel to each other and the 15 degree beam is directed straight ahead. Whether this represents "enough light" is up to the airplane builder to decide, based on the aircraft' intended use.

IN OUR OPINION this unit, when powered by the appropriate voltage (13.8 to 14.5 volts), produces a very bright beam that will make your aircraft much more visible in the pattern and on approach. It will also provide sufficient light for low-speed taxi operations in total darkness. It WILL NOT provide enough light for proper obstacle avoidance during night takeoff or landing on a non-lighted runway OR for an emergency off-field night landing. For this reason we have chosen to name this unit a "taxi light" and not a "landing light" unit. The builder/manufacturer may choose, at his/her own reponsibility, to consider LED-003' light output "enough for night operation", therefore meeting the landing light requirements for night operation

Paragraph d. is satisfied by installation of this unit away from fuel tanks or fuel lines and by the charachteristics of the materials used to manufacture this unit. All the plastic parts are made by materials complying with V-0 fire resistance specifications, and therefore qualifying as "flame resistant".

The strobe bulb specs will be discussed under the "anticollision light requirements".

§ 23.1385   Position light system installation.

 (a) General. Each part of each position light system must meet the applicable requirements of this section and each system as a whole must meet the requirements of §§23.1387 through 23.1397.

(b) Left and right position lights. Left and right position lights must consist of a red and a green light spaced laterally as far apart as practicable and installed on the airplane such that, with the airplane in the normal flying position, the red light is on the left side and the green light is on the right side.

(c) Rear position light. The rear position light must be a white light mounted as far aft as practicable on the tail or on each wing tip.

(d) Light covers and color filters. Each light cover or color filter must be at least flame resistant and may not change color or shape or lose any appreciable light transmission during normal use.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–17, 41 FR 55465, Dec. 20, 1976; Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

Applies to: LED-001, LED-002

Paragraph a., b. and c. are satisfied if the builder follows the recommended installation istructions, as provided in the installation manual.

Paragraph d. is satisfied by:

• 1. The charachteristics of the materials used to manufacture these units (all the plastic parts are made by materials complying with V-0 fire resistance specifications, and therefore qualifying as "flame resistant").
• 2. The fact that there are no color filters.
• 3. The fact that the clear dome is UV-stabilized, therefore preventing yellowing secondary to exposure to UV light.

§ 23.1387   Position light system dihedral angles.

(a) Except as provided in paragraph (e) of this section, each position light must, as installed, show unbroken light within the dihedral angles described in this section.

(b) Dihedral angle L (left) is formed by two intersecting vertical planes, the first parallel to the longitudinal axis of the airplane, and the other at 110 degrees to the left of the first, as viewed when looking forward along the longitudinal axis.

(c) Dihedral angle R (right) is formed by two intersecting vertical planes, the first parallel to the longitudinal axis of the airplane, and the other at 110 degrees to the right of the first, as viewed when looking forward along the longitudinal axis.

(d) Dihedral angle A (aft) is formed by two intersecting vertical planes making angles of 70 degrees to the right and to the left, respectively, to a vertical plane passing through the longitudinal axis, as viewed when looking aft along the longitudinal axis.

(e) If the rear position light, when mounted as far aft as practicable in accordance with §23.1385(c), cannot show unbroken light within dihedral angle A (as defined in paragraph (d) of this section), a solid angle or angles of obstructed visibility totaling not more than 0.04 steradians is allowable within that dihedral angle, if such solid angle is within a cone whose apex is at the rear position light and whose elements make an angle of 30° with a vertical line passing through the rear position light.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964; 30 FR 258, Jan. 9, 1965, as amended by Amdt. 23–12, 36 FR 21278, Nov. 5, 1971; Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

Applies to: LED-001, LED-002

Paragraph a. through d. are satisfied if the units are mounted, as recommended in the instruction manual, on the aircraft wingtips observing the following specifications:

• 1. No obstruction should be present in front of or behind the wingtip units (no mounting inside a sheared wingtip; an additional tail light will be needed in this case);
• 2. The base of the wingtip units should be mounted on a vertical plane, and the longitudinal axis of the wingtip unit should be parallel to the flight path in level flight.

§ 23.1389   Position light distribution and intensities.

(a) General. The intensities prescribed in this section must be provided by new equipment with each light cover and color filter in place. Intensities must be determined with the light source operating at a steady value equal to the average luminous output of the source at the normal operating voltage of the airplane. The light distribution and intensity of each position light must meet the requirements of paragraph (b) of this section.

(b) Position lights. The light distribution and intensities of position lights must be expressed in terms of minimum intensities in the horizontal plane, minimum intensities in any vertical plane, and maximum intensities in overlapping beams, within dihedral angles L, R, and A, and must meet the following requirements:

(1) Intensities in the horizontal plane. Each intensity in the horizontal plane (the plane containing the longitudinal axis of the airplane and perpendicular to the plane of symmetry of the airplane) must equal or exceed the values in §23.1391.

(2) Intensities in any vertical plane. Each intensity in any vertical plane (the plane perpendicular to the horizontal plane) must equal or exceed the appropriate value in §23.1393, where I is the minimum intensity prescribed in §23.1391 for the corresponding angles in the horizontal plane.

(3) Intensities in overlaps between adjacent signals. No intensity in any overlap between adjacent signals may exceed the values in §23.1395, except that higher intensities in overlaps may be used with main beam intensities substantially greater than the minima specified in §§23.1391 and 23.1393, if the overlap intensities in relation to the main beam intensities do not adversely affect signal clarity. When the peak intensity of the left and right position lights is more than 100 candles, the maximum overlap intensities between them may exceed the values in §23.1395 if the overlap intensity in Area A is not more than 10 percent of peak position light intensity and the overlap intensity in Area B is not more than 2.5 percent of peak position light intensity.

(c) Rear position light installation. A single rear position light may be installed in a position displaced laterally from the plane of symmetry of an airplane if—

(1) The axis of the maximum cone of illumination is parallel to the flight path in level flight; and

(2) There is no obstruction aft of the light and between planes 70 degrees to the right and left of the axis of maximum illumination.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

Applies to: LED-001

The requirements will be discussed as appropriate in the following paragraphs.

§ 23.1391   Minimum intensities in the horizontal plane of position lights.

Each position light intensity must equal or exceed the applicable values in the following table:

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

Applies to: LED-001, LED-002

RED and GREEN position lights: note from the table above that between 0 and 10, a light intensity of at least 40 candles is required; between 10 and 20, a light intensity of 30 candles is required; and between 20 and 110, only a light intensity of 5 candles is required.

WHITE position light: a uniform intensity of 20 candles is required between 110 and 180.

GS-AIR Red LED position light: includes 14 LEDs, each of them with a 14,000 millicandles output and a ½ output angle of 30.  The LEDs are oriented so that light intensity between 0 and 10 is > 45 candles, between 10 and 20 is > 40 candles and then tapers to about 10 candles at 110.

GS-AIR Green LED position light: includes 14 LEDs, each of them with a 16,000 millicandles output and a ½ output angle of 25. The LEDs are oriented so that light intensity between 0 and 10 is > 50 candles, between 10 and 20 is > 45 candles and then tapers to about 16 candles at 110.

GS-AIR White LED position light: Each unit includes 8 LEDs, each of them with a 22,000 millicandles output and a ½ output angle of 25 (see appendix 3 at the end of this document). Combined light intensity between 180 and 110 on the horizontal plane is uniformly > 25 candles throughout the arch.

§ 23.1393   Minimum intensities in any vertical plane of position lights.

Each position light intensity must equal or exceed the applicable values in the following table:

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

Applies to: LED-001, LED-002

Note from the table above that only 30% of relative intensity (compared to the horizontal reference plane) is needed for angles > 20 above or below the horizontal plane. The rationale is that the need for clear discrimination of light color patterns is greatest for aircraft flying at the same altitude (=same horizontal plane), and progressively declines for aircraft flying at increasingly different altitudes. In GS-Air position light systems, direct LED beams meet minimum intensity requirements between 0 and 20 from the horizontal plane, while diffused light from the chromed reflectors provides a uniformly tapering illumination from 20 to 90.

§ 23.1395   Maximum intensities in overlapping beams of position lights.

No position light intensity may exceed the applicable values in the following equal or exceed the applicable values in §23.1389(b)(3):

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 degrees; 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.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as amended by Amdt. 23–43, 58 FR 18977, Apr. 9, 1993]

§ 23.1397   Color specifications.

Each position light color must have the applicable International Commission on Illumination chromaticity coordinates as follows:

(a) Aviation red—

y is not greater than 0.335; and

z is not greater than 0.002.

(b) Aviation green—

x is not greater than 0.440−0.320y;

x is not greater than y−0.170; and

y is not less than 0.390−0.170x.

(c) Aviation white—

x is not less than 0.300 and not greater than 0.540;

y is not less than x−0.040 or y₀−0.010, whichever is the smaller; and

y is not greater than x+0.020 nor 0.636−0.400x;

Where y₀ is the y coordinate of the Planckian radiator for the value of x considered.

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, amended by Amdt. 23–11, 36 FR 12971, July 10, 1971]

§ 23.1399   Riding light.

(a) Each riding (anchor) light required for a seaplane or amphibian, must be installed so that it can—

(1) Show a white light for at least two miles at night under clear atmospheric conditions; and

(2) Show the maximum unbroken light practicable when the airplane is moored or drifting on the water.

(b) Externally hung lights may be used.

Not applicable

§ 23.1401   Anticollision light system.

(a) General. The airplane must have an anticollision light system that:

(1) Consists of one or more approved anticollision lights located so that their light will not impair the flight crewmembers' vision or detract from the conspicuity of the position lights; and

(2) Meets the requirements of paragraphs (b) through (f) of this section.

(b) Field of coverage. The system must consist of enough lights to illuminate the vital areas around the airplane, considering the physical configuration and flight characteristics of the airplane. The field of coverage must extend in each direction within at least 75 degrees above and 75 degrees below the horizontal plane of the airplane, except that there may be solid angles of obstructed visibility totaling not more than 0.5 steradians.

(c) Flashing characteristics. The arrangement of the system, that is, the number of light sources, beam width, speed of rotation, and other characteristics, must give an effective flash frequency of not less than 40, nor more than 100, cycles per minute. The effective flash frequency is the frequency at which the airplane's complete anticollision light system is observed from a distance, and applies to each sector of light including any overlaps that exist when the system consists of more than one light source. In overlaps, flash frequencies may exceed 100, but not 180, cycles per minute.

(d) Color. Each anticollision light must be either aviation red or aviation white and must meet the applicable requirements of §23.1397.

(e) Light intensity. The minimum light intensities in any vertical plane, measured with the red filter (if used) and expressed in terms of "effective" intensities, must meet the requirements of paragraph (f) of this section. The following relation must be assumed:

where:

I_e=effective intensity (candles).

I(t)=instantaneous intensity as a function of time.

t₂−t₁=flash time interval (seconds).

Normally, the maximum value of effective intensity is obtained when t₂ and t₁ are chosen so that the effective intensity is equal to the instantaneous intensity at t₂ and t₁.

(f) Minimum effective intensities for anticollision lights. Each anticollision light effective intensity must equal or exceed the applicable values in the following table.