AC 120-28D Appendix 4 07/13/99
0.8
1.2
1.0
0.8
0.6
0.4
0.2 0 1.0 1.2 1.4 1.6 1.8 h/h i
SELECTED DESCRIPTION FOR VARIANCES OF
HORIZONTAL TURBULENCE COMPONENTS
2.0 { .4 h > h i [ 0.177 + 0.823 h/h i ]
1.0 1 σu =σv σw σw == σu/σw===σ v σw h < h i Figure A4-5
AC 120-28D 07/13/99 Appendix 4
1.2
1.0
0.8
0.6
0.4
0.2 0 0.2 0.4 0.6 0.8 1.0 h/h i Lu = L v Lw hi = Altitude above which turbulence is isotropic Lv = L u Lw ={ Lu ={ h,h<h i d,h = h i Lw σu σw 3 d = h [0.177 + 0.823 h/h i ] 1.2 h < h i h > h i Lw /h i ,L u/h i = Lv/h i
SELECTED INTEGRAL SCALE DESCRIPTION Figure A4-6
AC 120-28D Appendix 4 07/13/99 Wind Model B.
Mean Wind It may be assumed that the cumulative probability of reported mean wind speed at landing, and the crosswind component of that wind are as shown in Figure A4-7. Normally, the mean wind which is reported to the pilot is measured at a height which may be between 6m (20 ft.) and 10m (33 ft.) above the runway. The models of wind shear and turbulence given in the following paragraphs assume this reference height is used.
Wind Shear Normal Wind Shear. Wind shear should be included in each simulated approach and landing, unless its effect can be accounted for separately. The magnitude of the shear should be defined by the expression:
u = 0.43 U log10 (z) + 0.57 U, for z ≥ 0.05 m (1) u ≅ 0, for z < 0.05m where z is the height in meters u is the mean wind speed at height z (meters) U is the mean wind speed at 10m (33 ft.).
Abnormal Wind Shear. The effect of wind shears exceeding those described above should be investigated using known severe wind shear data.
Turbulence.
Horizontal Component of Turbulence. It may be assumed that the longitudinal component (in the direction of mean wind) and lateral component of turbulence may each be represented by a Gaussian process having a spectrum of the form:
()ΦΩ Ω=• +2 12 22σπ L L (2) where ()ΦΩ = a spectral density in (meters/sec)2 per (radian/meter).
σ = root mean square (rms) turbulence intensity = 0.15 U L = scale length = 183m (600 ft.)
Ω = frequency in radians/meter.
Vertical Component of Turbulence. It may be assumed that the vertical component of turbulence has a spectrum of the form defined by equation (2) above. The following values have been in use:
σ = 1.5 knots with L = 9.2m (30 ft.)
or alternatively σ = 0.09 U with L = 4.6m (15 ft.) when z < 9.2m (30 ft.)
and L = 0.5 z when 9.2 < z < 305m (30 < z < 1000 ft.)
AC 120-28D 07/13/99 Appendix 4 403020100 Total Wind Head Wind ComponentCross Wind Component Tail Wind Component
WIND SPEED KNOTS Cumulative probability of reported Mean Wind, and Head Wind, Tail Wind Cross Wind Components, when landing.
NOTE: This data is based on world wide in-service operations of UK airlines (sample size about 2000) P R O B A B I L I T Y O F E X C E E D I N G G I V E N W I N D S P E E D
0.01
0.05
0.1
0.2
0.5 1 2 8 10 20 30 40 50 60 70 80 90 95 98 99
99.8
99.9
99.99 Figure A4-7
AC 120-28D 07/13/99 Appendix 5 Page 1 and 2 APPENDIX 5. [RESERVED]
AIRWORTHINESS DEMONSTRATION OF DECELERATION AND BRAKING SYSTEMS OR DISPLAYS.
THIS APPENDIX INTENTIONALLY LEFT BLANK [RESERVED]
AC 120-28D 07/13/99 Appendix 6 APPENDIX 6
AFM PROVISIONS AND EXAMPLE AFM WORDING
6.1. Example Provision - AFM "Certificate Limitation" Section.
6.2. Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Operational and Fail Passive FGS Capability]
6.3. Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability]
AC 120-28D Appendix 6 07/13/99
6.1 Example Provision - AFM "Certificate Limitation" Section (With "Type Specific" Example Information and Notes) ____________________________________________________________________________ (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 1 - CERTIFICATE LIMITATIONS
ELECTRONIC SYSTEMS
AUTOPILOT/FLIGHT DIRECTOR SYSTEM Automatic Landing Maximum wind component speeds when landing weather minima are predicated on autoland operations:
Headwind: 25 knots Tailwind: 15 knots Crosswind: 25 knots The maximum and minimum glideslope angles are 3.25 degrees and 2.5 degrees respectively.
The autoland capability may be used with flaps 20 or 30, with both engines operative or with one engine inoperative. The Autopilot Flight Director System (AFDS) status annunciation must have LAND 2 or LAND 3 displayed and the SLATS DRIVE message must not be present.
Automatic Approach with Flaps 25 Autoland is not approved with flaps 25.
FAA APPROVED (Date) Section 3 Page ___
AC 120-28D 07/13/99 Appendix 6
6.2 Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Operational and Fail Passive FGS Capability] ____________________________________________________________________________ (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 3 - NORMAL PROCEDURES
AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS)
LOW WEATHER MINIMA - AUTOMATIC LANDING - FAIL-OPERATIONAL The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category III as specified in FAA Advisory Circular (AC) 120-28D Appendix 3 for a failoperational automatic landing system, with the following functions operative and LAND 3 annunciated:
Autoland status annunciation on both PFD’s Autothrottle Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
LOW WEATHER MINTMA - AUTOMATIC LANDING - FAIL-PASSIVE The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category III as specified in FAA AC 120-28D Appendix 3 for a fail-passive automatic landing system, with the following functions operative and LAND 2 annunciated:
Autoland status annunciation on both PFD’s Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS The demonstration for fail-passive autoland operations with LAND 2 annunciated included a requirement for a go-around if a subsequent autopilot system failure were to be detected on approach, if operational credit for use of autoland is required.
CAUTION: If the autopilot disconnects during an engine-out go-around, loss of autopilot rudder control can result in large yaw and roll excursions.
FAA APPROVED (Date) Section 3 Page ___
AC 120-28D Appendix 6 07/13/99 Section 3 - NORMAL PROCEDURES AUTOPILOT - F LIGHT DIRECTOR SYSTEM (AFDS) (Continued)
LOW WEATHER MINIMA - AUTOPILOT APPROACH The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category II as specified in FAA (AC) 120-29__ Appendix __ for automatic approach with the following functions operative and LAND 3 or LAND 2 annunciated:
Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
LOW WEATHER MINIMA - FLIGHT DIRECTOR The flight director system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category II as specified in FAA (AC) 120-29__ Appendix __ for manual approach with the following functions operative:
Normal flight controls Air Data Inertial Reference Unit Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
SINGLE SOURCE F/D FAA APPROVED (Date) Section 3 Page ___
AC 120-28D 07/13/99 Appendix 6
6.3 Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability] ____________________________________________________________________________ (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 3 - NORMAL OPERATIONS
AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) The Autopilot-Flight Director System is used as either a single channel autopilot or flight director for en route and single channel approaches. Dual autopilot channels provide fail-passive operation for automatic landing and go-around. Dual flight directors provide for takeoff, approach and go-around guidance.
The following flight path control functions for automatic (autopilot) and/or manual (flight director) control of the airplane are provided:
Lateral navigation Vertical navigation VOR Localizer (Front course only) Approach Autoland (Dual autopilot only) Go-around (Dual autopilot and/or flight director only) The following pilot assist functions for automatic (autopilot) and/or manual (flight director) control of the airplane are provided:
Control Wheel Steering (Autopilot only) Heading select and hold Vertical speed select and hold IAS/Mach select and hold (Elevator control of speed in level change) Altitude Select/Acquire or Capture and Hold Takeoff (Dual Flight director only) Go-around, one engine inoperative (Dual Flight director only) The Captain's and First Officer's instruments (Display Source, VHF NAV and IRS) must not be on the same source when credit for use of the AFDS is necessary to make lower weather minima approaches.
An interlock is provided with the electrical transfer bus sensing circuit to preclude dual-channel autopilot operation on a single source of power. However, the Auxiliary Power Unit generator may be used as an independent power source.
FAA APPROVED (Date) Section 3 Page ___