Federal Aviation Administration, DOT § 23.1325

airspeed indicator instrument calibra- (1) From 0.8 of the minimum value of V1 to tion error, may not exceed three per- the maximum value of V2, considering the cent of the calibrated airspeed or five approved ranges of altitude and weight; and knots, whichever is greater, through- (2) The ground run calibration must be de- termined assuming an engine failure at the out the following speed ranges: minimum value of V1. (1) 1.3 VS1 to VMO/MMO or VNE, whichever is appropriate with flaps re- tracted. * * * * * (2) 1.3 V 1 to V with flaps extended. S FE § 23.1325 Static pressure system. (c) The design and installation of each airspeed indicating system must (a) Each instrument provided with provide positive drainage of moisture static pressure case connections must from the pitot static plumbing. be so vented that the influence of air- (d) If certification for instrument plane speed, the opening and closing of flight rules or flight in icing conditions windows, airflow variations, moisture, is requested, each airspeed system or other foreign matter will least af- must have a heated pitot tube or an fect the accuracy of the instruments equivalent means of preventing mal- except as noted in paragraph (b)(3) of function due to icing. this section. (e) In addition, for commuter cat- (b) If a static pressure system is nec- egory airplanes, the airspeed indi- essary for the functioning of instru- cating system must be calibrated to de- ments, systems, or devices, it must termine the system error during the comply with the provisions of para- accelerate-takeoff ground run. The graphs (b) (1) through (3) of this sec- ground run calibration must be ob- tion. tained between 0.8 of the minimum (1) The design and installation of a value of V1, and 1.2 times the maximum static pressure system must be such value of V1 considering the approved that— ranges of altitude and weight. The (i) Positive drainage of moisture is ground run calibration must be deter- provided; mined assuming an engine failure at (ii) Chafing of the tubing, and exces- the minimum value of V1. sive distortion or restriction at bends (f) For commuter category airplanes, in the tubing, is avoided; and where duplicate airspeed indicators are (iii) The materials used are durable, required, their respective pitot tubes suitable for the purpose intended, and must be far enough apart to avoid dam- protected against corrosion. age to both tubes in a collision with a (2) A proof test must be conducted to bird. demonstrate the integrity of the static [Amdt. 23–20, 42 FR 36968, July 18, 1977, as pressure system in the following man- amended by Amdt. 23–34, 52 FR 1834, Jan. 15, ner: 1987; 52 FR 34745, Sept. 14, 1987; Amdt. 23–42, (i) Unpressurized airplanes. Evacuate 56 FR 354, Jan. 3, 1991; Amdt. 23–49, 61 FR the static pressure system to a pres- 5168, Feb. 9, 1996] sure differential of approximately 1 EFFECTIVE DATE NOTE: By Amdt. 23–62, 76 inch of mercury or to a reading on the FR 75761, Dec. 2, 2011, § 23.1323 was amended altimeter, 1,000 feet above the aircraft by revising paragraph (e), effective Jan. 31, elevation at the time of the test. With- 2012. For the convenience of the user, the re- out additional pumping for a period of vised text is set forth as follows: 1 minute, the loss of indicated altitude § 23.1323 Airspeed indicating system. must not exceed 100 feet on the altimeter. (ii) Pressurized airplanes. Evacuate * * * * * the static pressure system until a pres- (e) In addition, for normal, utility, and ac- sure differential equivalent to the max- robatic category multiengine jets of more imum cabin pressure differential for than 6,000 pounds maximum weight and com- which the airplane is type certificated muter category airplanes, each system must be calibrated to determine the system error is achieved. Without additional pump- during the accelerate-takeoff ground run. ing for a period of 1 minute, the loss of The ground run calibration must be deter- indicated altitude must not exceed 2 mined— percent of the equivalent altitude of

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the maximum cabin differential pres- § 23.1559(b) of this part, paragraph (b)(3) sure or 100 feet, whichever is greater. of this section does not apply. (3) If a static pressure system is pro- [Amdt. 23–1, 30 FR 8261, June 29, 1965, as vided for any instrument, device, or amended by Amdt. 23–6, 32 FR 7586, May 24, system required by the operating rules 1967; 32 FR 13505, Sept. 27, 1967; 32 FR 13714, of this chapter, each static pressure Sept. 30, 1967; Amdt. 23–20, 42 FR 36968, July port must be designed or located in 18, 1977; Amdt. 23–34, 52 FR 1834, Jan. 15, 1987; such a manner that the correlation be- Amdt. 23–42, 56 FR 354, Jan. 3, 1991; Amdt. 23– tween air pressure in the static pres- 49, 61 FR 5169, Feb. 9, 1996; Amdt. 23–50, 61 FR sure system and true ambient atmos- 5192, Feb. 9, 1996] pheric static pressure is not altered when the airplane encounters icing § 23.1326 Pitot heat indication systems. conditions. An antiicing means or an If a flight instrument pitot heating alternate source of static pressure may system is installed to meet the require- be used in showing compliance with ments specified in § 23.1323(d), an indi- this requirement. If the reading of the cation system must be provided to in- altimeter, when on the alternate static dicate to the flight crew when that pressure system differs from the read- pitot heating system is not operating. ing of the altimeter when on the pri- The indication system must comply mary static system by more than 50 with the following requirements: feet, a correction card must be pro- (a) The indication provided must in- vided for the alternate static system. corporate an amber light that is in (c) Except as provided in paragraph clear view of a flightcrew member. (d) of this section, if the static pressure (b) The indication provided must be system incorporates both a primary designed to alert the flight crew if ei- and an alternate static pressure source, ther of the following conditions exist: the means for selecting one or the (1) The pitot heating system is other source must be designed so switched ‘‘off.’’ that— (2) The pitot heating system is (1) When either source is selected, the switched ‘‘on’’ and any pitot tube heat- other is blocked off; and ing element is inoperative. (2) Both sources cannot be blocked off simultaneously. [Doc. No. 27806, 61 FR 5169, Feb. 9, 1996] (d) For unpressurized airplanes, para- § 23.1327 Magnetic direction indicator. graph (c)(1) of this section does not apply if it can be demonstrated that (a) Except as provided in paragraph the static pressure system calibration, (b) of this section— when either static pressure source is (1) Each magnetic direction indicator selected, is not changed by the other must be installed so that its accuracy static pressure source being open or is not excessively affected by the air- blocked. plane’s vibration or magnetic fields; (e) Each static pressure system must and be calibrated in flight to determine the (2) The compensated installation may system error. The system error, in in- not have a deviation in level flight, dicated pressure altitude, at sea-level, greater than ten degrees on any head- with a standard atmosphere, excluding ing. instrument calibration error, may not (b) A magnetic nonstabilized direc- exceed ±30 feet per 100 knot speed for tion indicator may deviate more than the appropriate configuration in the ten degrees due to the operation of speed range between 1.3 VS0 with flaps electrically powered systems such as extended, and 1.8 VS1 with flaps re- electrically heated windshields if ei- tracted. However, the error need not be ther a magnetic stabilized direction in- less than 30 feet. dicator, which does not have a devi- (f) [Reserved] ation in level flight greater than ten (g) For airplanes prohibited from degrees on any heading, or a gyroscopic flight in instrument meteorological or icing conditions, in accordance with

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