§ 91.411 Altimeter system and altitude reporting equipment tests and
(a) No person may operate an airplane, or helicopter, in controlled airspace
under IFR unless—
(1) Within the preceding 24 calendar months, each static pressure system,
each altimeter instrument, and each automatic pressure altitude reporting system
has been tested and inspected and found to comply with appendices E and F of
part 43 of this chapter;
(2) Except for the use of system drain and alternate static pressure valves,
following any opening and closing of the static pressure system, that system has
been tested and inspected and found to comply with paragraph (a),
appendix E, of
part 43 of this chapter; and
(3) Following installation or maintenance on the automatic pressure altitude
reporting system of the ATC transponder where data correspondence error could be
introduced, the integrated system has been tested, inspected, and found to
comply with paragraph (c), appendix E, of part 43 of this chapter.
(b) The tests required by paragraph (a) of this section must be conducted by—
(1) The manufacturer of the airplane, or helicopter, on which the tests and
inspections are to be performed;
(2) A certificated repair station properly equipped to perform those
functions and holding—
(i) An instrument rating, Class I;
(ii) A limited instrument rating appropriate to the make and model of
appliance to be tested;
(iii) A limited rating appropriate to the test to be performed;
(iv) An airframe rating appropriate to the airplane, or helicopter, to be
(3) A certificated mechanic with an airframe rating (static pressure system
tests and inspections only).
(c) Altimeter and altitude reporting equipment approved under Technical
Standard Orders are considered to be tested and inspected as of the date of
(d) No person may operate an airplane, or helicopter, in controlled airspace
under IFR at an altitude above the maximum altitude at which all altimeters and
the automatic altitude reporting system of that airplane, or helicopter, have
§ 91.413 ATC transponder tests and inspections.
(a) No persons may use an ATC transponder that is specified in
91.215(a), 121.345(c), or §135.143(c) of this chapter unless, within the
preceding 24 calendar months, the ATC transponder has been tested and inspected
and found to comply with appendix F of part 43 of this chapter; and
(b) Following any installation or maintenance on an ATC
transponder where data correspondence error could be introduced, the integrated
system has been tested, inspected, and found to comply with paragraph (c),
appendix E, of part 43 of this chapter.
(c) The tests and inspections specified in this section must
be conducted by—
(1) A certificated repair station properly equipped to perform
those functions and holding—
(i) A radio rating, Class III;
(ii) A limited radio rating appropriate to the make and model
transponder to be tested;
(iii) A limited rating appropriate to the test to be
(2) A holder of a continuous airworthiness maintenance program
as provided in part 121 or §135.411(a)(2) of this chapter; or
(3) The manufacturer of the aircraft on which the transponder
to be tested is installed, if the transponder was installed by that
§ 23.1325 Static pressure system.
(a) Each instrument provided with static pressure case connections must be so
vented that the influence of airplane speed, the opening and closing of windows,
airflow variations, moisture, or other foreign matter will least affect the
accuracy of the instruments except as noted in paragraph (b)(3) of this section.
(b) If a static pressure system is necessary for the functioning of
instruments, systems, or devices, it must comply with the provisions of
paragraphs (b)(1) through (3) of this section.
(1) The design and installation of a static pressure system must be such
(i) Positive drainage of moisture is provided;
(ii) Chafing of the tubing, and excessive distortion or restriction at bends
in the tubing, is avoided; and
(iii) The materials used are durable, suitable for the purpose intended, and
protected against corrosion.
(2) A proof test must be conducted to demonstrate the integrity of the static
pressure system in the following manner:
(i) Unpressurized airplanes. Evacuate the static pressure system to a
pressure differential of approximately 1 inch of mercury or to a reading on the
altimeter, 1,000 feet above the aircraft elevation at the time of the test.
Without additional pumping for a period of 1 minute, the loss of indicated
altitude must not exceed 100 feet on the altimeter.
(ii) Pressurized airplanes. Evacuate the static pressure system until
a pressure differential equivalent to the maximum cabin pressure differential
for which the airplane is type certificated is achieved. Without additional
pumping for a period of 1 minute, the loss of indicated altitude must not exceed
2 percent of the equivalent altitude of the maximum cabin differential pressure
or 100 feet, whichever is greater.
(3) If a static pressure system is provided for any instrument, device, or
system required by the operating rules of this chapter, each static pressure
port must be designed or located in such a manner that the correlation between
air pressure in the static pressure system and true ambient atmospheric static
pressure is not altered when the airplane encounters icing conditions. An
antiicing means or an alternate source of static pressure may be used in showing
compliance with this requirement. If the reading of the altimeter, when on the
alternate static pressure system differs from the reading of the altimeter when
on the primary static system by more than 50 feet, a correction card must be
provided for the alternate static system.
(c) Except as provided in paragraph (d) of this section, if the static
pressure system incorporates both a primary and an alternate static pressure
source, the means for selecting one or the other source must be designed so
(1) When either source is selected, the other is blocked off; and
(2) Both sources cannot be blocked off simultaneously.
(d) For unpressurized airplanes, paragraph (c)(1) of this section does not
apply if it can be demonstrated that the static pressure system calibration,
when either static pressure source is selected, is not changed by the other
static pressure source being open or blocked.
(e) Each static pressure system must be calibrated in flight to determine the
system error. The system error, in indicated pressure altitude, at sea-level,
with a standard atmosphere, excluding instrument calibration error, may not
exceed ±30 feet per 100 knot speed for the appropriate configuration in the
speed range between 1.3 VS0with flaps extended, and 1.8 VS1with
flaps retracted. However, the error need not be less than 30 feet.
(g) For airplanes prohibited from flight in instrument meteorological or
icing conditions, in accordance with §23.1559(b) of this part, paragraph (b)(3)
of this section does not apply.