828
14 CFR Ch. I (1–1–14 Edition)
Pt. 91, App. A
(5) Two gyroscopic direction indicating
systems.
(6) Two airspeed indicators.
(7) Two sensitive altimeters adjustable for
barometric pressure, each having a placarded
correction for altimeter scale error and for
the wheel height of the aircraft. After June
26, 1979, two sensitive altimeters adjustable
for barometric pressure, having markings at
20-foot intervals and each having a placarded
correction for altimeter scale error and for
the wheel height of the aircraft.
(8) Two vertical speed indicators.
(9) A flight control guidance system that
consists of either an automatic approach
coupler or a flight director system. A flight
director system must display computed in-
formation as steering command in relation
to an ILS localizer and, on the same instru-
ment, either computed information as pitch
command in relation to an ILS glide slope or
basic ILS glide slope information. An auto-
matic approach coupler must provide at
least automatic steering in relation to an
ILS localizer. The flight control guidance
system may be operated from one of the re-
ceiving systems required by subparagraph (1)
of this paragraph.
(10) For Category II operations with deci-
sion heights below 150 feet either a marker
beacon receiver providing aural and visual
indications of the inner marker or a radio al-
timeter.
(b)
Group II. (1) Warning systems for imme-
diate detection by the pilot of system faults
in items (1), (4), (5), and (9) of Group I and, if
installed for use in Category III operations,
the radio altimeter and autothrottle system.
(2) Dual controls.
(3) An externally vented static pressure
system with an alternate static pressure
source.
(4) A windshield wiper or equivalent means
of providing adequate cockpit visibility for a
safe visual transition by either pilot to
touchdown and rollout.
(5) A heat source for each airspeed system
pitot tube installed or an equivalent means
of preventing malfunctioning due to icing of
the pitot system.
3. Instruments and Equipment Approval
(a)
General. The instruments and equip-
ment required by section 2 of this appendix
must be approved as provided in this section
before being used in Category II operations.
Before presenting an aircraft for approval of
the instruments and equipment, it must be
shown that since the beginning of the 12th
calendar month before the date of submis-
sion—
(1) The ILS localizer and glide slope equip-
ment were bench checked according to the
manufacturer’s instructions and found to
meet those standards specified in RTCA
Paper 23–63/DO–117 dated March 14, 1963,
‘‘Standard Adjustment Criteria for Airborne
Localizer and Glide Slope Receivers,’’ which
may be obtained from the RTCA Secretariat,
1425 K St., NW., Washington, DC 20005.
(2) The altimeters and the static pressure
systems were tested and inspected in accord-
ance with appendix E to part 43 of this chap-
ter; and
(3) All other instruments and items of
equipment specified in section 2(a) of this ap-
pendix that are listed in the proposed main-
tenance program were bench checked and
found to meet the manufacturer’s specifica-
tions.
(b)
Flight control guidance system. All com-
ponents of the flight control guidance sys-
tem must be approved as installed by the
evaluation program specified in paragraph
(e) of this section if they have not been ap-
proved for Category III operations under ap-
plicable type or supplemental type certifi-
cation procedures. In addition, subsequent
changes to make, model, or design of the
components must be approved under this
paragraph. Related systems or devices, such
as the autothrottle and computed missed ap-
proach guidance system, must be approved in
the same manner if they are to be used for
Category II operations.
(c)
Radio altimeter. A radio altimeter must
meet the performance criteria of this para-
graph for original approval and after each
subsequent alteration.
(1) It must display to the flight crew clear-
ly and positively the wheel height of the
main landing gear above the terrain.
(2) It must display wheel height above the
terrain to an accuracy of plus or minus 5 feet
or 5 percent, whichever is greater, under the
following conditions:
(i) Pitch angles of zero to plus or minus 5
degrees about the mean approach attitude.
(ii) Roll angles of zero to 20 degrees in ei-
ther direction.
(iii) Forward velocities from minimum ap-
proach speed up to 200 knots.
(iv) Sink rates from zero to 15 feet per sec-
ond at altitudes from 100 to 200 feet.
(3) Over level ground, it must track the ac-
tual altitude of the aircraft without signifi-
cant lag or oscillation.
(4) With the aircraft at an altitude of 200
feet or less, any abrupt change in terrain
representing no more than 10 percent of the
aircraft’s altitude must not cause the altim-
eter to unlock, and indicator response to
such changes must not exceed 0.1 seconds
and, in addition, if the system unlocks for
greater changes, it must reacquire the signal
in less than 1 second.
(5) Systems that contain a push-to-test
feature must test the entire system (with or
without an antenna) at a simulated altitude
of less than 500 feet.
(6) The system must provide to the flight
crew a positive failure warning display any
time there is a loss of power or an absence of
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