Federal Aviation Administration, DOT § 23.1323

(1) The instrument that most effec- (e) Effective under all probable cock- tively indicates the attitude must be pit lighting conditions. on the panel in the top center position; [Amdt. 23–17, 41 FR 55465, Dec. 20, 1976, as (2) The instrument that most effec- amended by Amdt. 23–43, 58 FR 18976, Apr. 9, tively indicates must be adja- 1993] cent to and directly to the left of the instrument in the top center position; § 23.1323 Airspeed indicating system. (3) The instrument that most effec- (a) Each airspeed indicating instru- tively indicates altitude must be adja- ment must be calibrated to indicate cent to and directly to the right of the (at sea level with a stand- instrument in the top center position; ard atmosphere) with a minimum prac- (4) The instrument that most effec- ticable instrument calibration error tively indicates direction of flight, when the corresponding pitot and stat- other than the magnetic direction indi- ic pressures are applied. cator required by § 23.1303(c), must be (b) Each airspeed system must be adjacent to and directly below the in- calibrated in flight to determine the strument in the top center position; system error. The system error, includ- and ing , but excluding the (5) Electronic display indicators may instrument calibra- be used for compliance with paragraphs tion error, may not exceed three per- (d)(1) through (d)(4) of this section cent of the calibrated airspeed or five when such displays comply with re- knots, whichever is greater, through- quirements in § 23.1311. out the following speed ranges: (e) If a visual indicator is provided to (1) 1.3 VS1 to VMO/MMO or VNE, which- indicate malfunction of an instrument, ever is appropriate with flaps re- it must be effective under all probable tracted. cockpit lighting conditions. (2) 1.3 VS1 to VFE with flaps extended. [Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as (c) The design and installation of amended by Amdt. 23–14, 38 FR 31824, Nov. 19, each airspeed indicating system must 1973; Amdt. 23–20, 42 FR 36968, July 18, 1977; provide positive drainage of moisture Amdt. 23–41, 55 FR 43310, Oct. 26, 1990; 55 FR from the pitot static plumbing. 46888, Nov. 7, 1990; Amdt. 23–49, 61 FR 5168, (d) If certification for instrument Feb. 9, 1996] flight rules or flight in icing conditions § 23.1322 Warning, caution, and advi- is requested, each airspeed system sory lights. must have a heated or an equivalent means of preventing mal- If warning, caution, or advisory function due to icing. lights are installed in the cockpit, they (e) In addition, for commuter cat- must, unless otherwise approved by the egory airplanes, the airspeed indi- Administrator, be— cating system must be calibrated to de- (a) Red, for warning lights (lights in- termine the system error during the dicating a hazard which may require accelerate-takeoff ground run. The immediate corrective action); ground run calibration must be ob- (b) Amber, for caution lights (lights tained between 0.8 of the minimum indicating the possible need for future value of V , and 1.2 times the maximum corrective action); 1 value of V1 considering the approved (c) Green, for safe operation lights; ranges of altitude and weight. The and ground run calibration must be deter- (d) Any other color, including white, mined assuming an engine failure at for lights not described in paragraphs the minimum value of V1. (a) through (c) of this section, provided (f) For commuter category airplanes, the color differs sufficiently from the where duplicate airspeed indicators are colors prescribed in paragraphs (a) required, their respective pitot tubes through (c) of this section to avoid pos- sible confusion.

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must be far enough apart to avoid dam- the maximum cabin differential pres- age to both tubes in a collision with a sure or 100 feet, whichever is greater. bird. (3) If a system is pro- [Amdt. 23–20, 42 FR 36968, July 18, 1977, as vided for any instrument, device, or amended by Amdt. 23–34, 52 FR 1834, Jan. 15, system required by the operating rules 1987; 52 FR 34745, Sept. 14, 1987; Amdt. 23–42, of this chapter, each static pressure 56 FR 354, Jan. 3, 1991; Amdt. 23–49, 61 FR port must be designed or located in 5168, Feb. 9, 1996] such a manner that the correlation be- tween air pressure in the static pres- § 23.1325 Static pressure system. sure system and true ambient atmos- (a) Each instrument provided with pheric static pressure is not altered static pressure case connections must when the airplane encounters icing be so vented that the influence of air- conditions. An antiicing means or an plane speed, the opening and closing of alternate source of static pressure may windows, airflow variations, moisture, be used in showing compliance with or other foreign matter will least af- this requirement. If the reading of the fect the accuracy of the instruments , when on the alternate static except as noted in paragraph (b)(3) of pressure system differs from the read- this section. (b) If a static pressure system is nec- ing of the altimeter when on the pri- essary for the functioning of instru- mary static system by more than 50 ments, systems, or devices, it must feet, a correction card must be pro- comply with the provisions of para- vided for the alternate static system. graphs (b) (1) through (3) of this sec- (c) Except as provided in paragraph tion. (d) of this section, if the static pressure (1) The design and installation of a system incorporates both a primary static pressure system must be such and an alternate static pressure source, that— the means for selecting one or the (i) Positive drainage of moisture is other source must be designed so provided; that— (ii) Chafing of the tubing, and exces- (1) When either source is selected, the sive distortion or restriction at bends other is blocked off; and in the tubing, is avoided; and (2) Both sources cannot be blocked (iii) The materials used are durable, off simultaneously. suitable for the purpose intended, and (d) For unpressurized airplanes, para- protected against corrosion. graph (c)(1) of this section does not (2) A proof test must be conducted to apply if it can be demonstrated that demonstrate the integrity of the static the static pressure system calibration, pressure system in the following man- when either static pressure source is ner: selected, is not changed by the other (i) Unpressurized airplanes. Evacuate static pressure source being open or the static pressure system to a pres- blocked. sure differential of approximately 1 (e) Each static pressure system must inch of mercury or to a reading on the altimeter, 1,000 feet above the be calibrated in flight to determine the elevation at the time of the test. With- system error. The system error, in in- out additional pumping for a period of dicated pressure altitude, at sea-level, 1 minute, the loss of indicated altitude with a standard atmosphere, excluding must not exceed 100 feet on the altim- instrument calibration error, may not ± eter. exceed 30 feet per 100 speed for (ii) Pressurized airplanes. Evacuate the appropriate configuration in the the static pressure system until a pres- speed range between 1.3 VS0 with flaps sure differential equivalent to the max- extended, and 1.8 VS1 with flaps re- imum cabin pressure differential for tracted. However, the error need not be which the airplane is type certificated less than 30 feet. is achieved. Without additional pump- (f) [Reserved] ing for a period of 1 minute, the loss of (g) For airplanes prohibited from indicated altitude must not exceed 2 flight in instrument meteorological or percent of the equivalent altitude of icing conditions, in accordance with

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