FreeFlight Systems RA4XXX Radar Altimeter that measures altitude above ground level User Manual TYPE CERTIFICATION REPORT
FreeFlight Systems Radar Altimeter that measures altitude above ground level TYPE CERTIFICATION REPORT
User Manual
Rhein Tech Laboratories, Inc. 360 Herndon Parkway Suite 1400 Herndon, VA 20170 www.rheintech.com Appendix G: Client: FreeFlight Systems Model: RA-4000 Series FCC ID: T7YRA4XXX Standards: Part 87 Report #: 2008233 User Manual Please refer to the following pages for the manual. 22 of 27 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F EQUIPMENT INSTALLATION MANUAL FOR FREEFLIGHT SYSTEMS RA-4000 SERIES RADAR ALTIMETERS Part Numbers 84560-XX FreeFlight Systems 3700 Interstate 35 South Waco, TX 76706-3756 U.S.A. 1 (254) 662-0000 1 (800) 487-4662 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F REVISION HISTORY REV DESCRIPTION Initial release Released per ECN F05032 Released per ECN F06008 Released per SRR #7 Released per ECN F08008 Released per ECN F08030 DATE 02-Oct-05 21-Nov-05 11-Sep-06 20-Sep-07 14-Aug-08 21-Nov-08 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F Table of Contents 1 INTRODUCTION....................................................................................................... 1-1 1.1 REFERENCE DOCUMENTS......................................................................................... 1-2 1.2 TABLE OF ACRONYMS & ABBREVIATIONS ............................................................... 1-2 2 DESCRIPTION........................................................................................................... 2-1 2.1 OPERATIONAL MODES ............................................................................................. 2-1 2.2 SYSTEM LIMITATIONS .............................................................................................. 2-2 2.3 SPECIFICATIONS ....................................................................................................... 2-3 2.4 COMPONENT AND ACCESSORY PART NUMBERS ...................................................... 2-4 2.5 LICENSE REQUIREMENTS ......................................................................................... 2-4 3 ELECTRICAL INTERFACE.................................................................................... 3-1 3.1 GROUND .................................................................................................................. 3-1 3.2 POWER IN ................................................................................................................ 3-1 3.3 RESET ...................................................................................................................... 3-1 3.4 STRUT INPUT............................................................................................................ 3-2 3.5 NAV TX/RX ............................................................................................................ 3-2 3.6 PGM-EN ................................................................................................................. 3-2 3.7 NAV-BIAS ................................................................................................................ 3-2 3.8 NAV-COM ................................................................................................................ 3-2 3.9 NAV-TXA/TXB ...................................................................................................... 3-2 3.10 ARINC-TXA/TXB ............................................................................................... 3-2 3.11 ARINC SPEED SELECT .......................................................................................... 3-2 4 FUNCTIONAL INTERFACES................................................................................. 4-1 4.1 RS-232/422/485 INTERFACE ................................................................................... 4-1 4.2 ARINC 429 INTERFACE ........................................................................................... 4-3 5 MECHANICAL .......................................................................................................... 5-1 5.1 RA-4000 MOUNTING ............................................................................................... 5-1 5.2 CONNECTORS ........................................................................................................... 5-1 5.3 ANTENNA MOUNTING .............................................................................................. 5-3 6 INSTALLATION........................................................................................................ 6-2 6.1 GENERAL INFORMATION .......................................................................................... 6-2 6.2 UNPACKING AND INSPECTING EQUIPMENT .............................................................. 6-2 6.3 EQUIPMENT LIMITATIONS ........................................................................................ 6-2 6.4 ANTENNA INSTALLATION ........................................................................................ 6-3 6.5 RA-4000 INSTALLATION ......................................................................................... 6-4 APPENDIX A – ENVIRONMENTAL CATEGORIES............................................. 6-1 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F List of Figures Figure 1-1: RA-4000 System Block Diagram ................................................................. 1-1 Figure 5-1: RA-4000 Installation Drawing...................................................................... 5-2 Figure 5-2: Antenna (P/N 9-1203-115-00) Installation Drawing .................................... 5-3 List of Tables Table 2-1: System Technical Characteristics................................................................... 2-3 Table 2-2: RA-4000 Physical Characteristics.................................................................. 2-3 Table 2-3: Antenna (P/N 9-1203-115-00) Physical Characteristics ................................ 2-3 Table 2-4: RA-4000 Install Kit ........................................................................................ 2-4 Table 2-5: Optional FreeFlight Install Kit and Parts ....................................................... 2-4 Table 2-6: Other Accessories........................................................................................... 2-4 Table 3-1: RA-4000 Interface Pin out ............................................................................. 3-1 Table 4-1: Data Field Definition...................................................................................... 4-1 Table 4-2: Status Byte Bit Definition .............................................................................. 4-2 Table 4-3: Sample Packet at 1000’ .................................................................................. 4-2 Table 5-1: Connector Descriptions .................................................................................. 5-1 Table 6-1: Propagation Delay and Attenuation of the Antenna Cable ............................ 6-3 Table 6-2: Typical Antenna Cable Lengths ..................................................................... 6-3 ii Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 1 Introduction This manual contains installation data and specifications for the FreeFlight Systems RA4000 Series Radar Altimeters (P/N 84560-XX), hereafter referred to as the RA-4000. The RA-4000 meets the requirements for a TSO-C87 Radar Altimeter with Precision Equipment output. The RA-4000 is designed to provide altitude above ground level (AGL) data to an electronic flight instrument system (EFIS), an integrated Flight Management System (FMS), or a navigation management system (NMS). Altitude is calculated by assessing the round trip delay of a signal reflected from the ground. The system consists of three Line Replaceable Units (LRUs): the RA-4000 Receiver/Transmitter (R/T) Unit and two Antenna Units (refer to section 2.4). Refer to Figure 1-1 for a system block diagram. I/O Transmit RA-4000 Power In Strut Switch In Altitude out: - Serial RS-485/422 - Serial RS-232C Receive Figure 1-1: RA-4000 System Block Diagram 1-1 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 1.1 Reference Documents Document Number RTCA/DO-160E RTCA/DO-178B TSO-C87 RTCA/DO-155 ARINC 429 Title Environmental Conditions and Test Procedures for Airborne Equipment; 29-July-97 (incorporating Change 1 dated 14-Dec-00, Change 2 dated 12June-01, and Change 3 dated 05-Dec-02). Software Considerations In Airborne Systems And Equipment Certification; 1-Dec-92. AIRBORNE LOW-RANGE RADIO ALTIMETER; 1-Feb-1966. Minimum Performance Standards Airborne Low-Range Radar Altimeters; 1-Nov-1974. Mark 33 Digital Information Transfer System; May 17, 2004 1.2 Table of Acronyms & Abbreviations The following acronyms and abbreviations are used throughout this document. Abbreviation AGL BCD dB EFIS FAR FFS FMCW FMS Hz LRU LSB MHz ms NCD NMS ns P/N R/T RX SDI SSM TNC TSO TX VCO VDC Definition Ampere Above Ground Level Binary Coded Decimal Decibels Electronic Flight Instrument System Federal Aviation Regulations FreeFlight Systems Frequency Modulated Continuous Wave Flight Management System Hertz Line Replaceable Unit Least-Significant Bit Mega-Hertz Milliseconds No Computed Data Navigation Management System Nanoseconds Part Number Receiver / Transmitter Receive Source/Destination Indicator Sign/Status Matrix Threaded Neill-Concelman [connector] Technical Standard Order Transmit Voltage-Controlled Oscillator Volts Direct Current 1-2 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 2 Description A complete system consists of an RA-4000 R/T unit (P/N 84560-XX) and two antennas (refer to section 2.4). The RA-4000 provides AGL altitude information from -20 feet up to 2000 feet maximum via computer interface. The RA-4000 Radar Altimeter system utilizes a reliable solid-state voltage-controlled oscillator (VCO) to drive its transmitter. Embedded processors precisely measure the signal delay, calculate the altitude, and provide a simple to use computer interface. 2.1 Operational Modes Once the unit has completed a reset, it begins outputting data at a 25 Hz rate. Data consists of the altitude and a status byte on the RS-232/422/485 interface (refer to section 4 for a description of the protocol) and labels 164, 165, and 377 on the ARINC 429 interface. Following is a description of different modes for the unit. 2.1.1 Power On Self-Test At power on, the system initializes operation and performs a self-test for approximately 20 seconds. In the self-test, the lock circuitry is tested and a test signal applied to the receive circuitry. During this time, the unit reports an altitude of 40±3 feet and asserts the “Self-Test” bit in the status byte (see section 4.1.2.1.4). 2.1.2 Altitude Zero Calibration When the Altitude Zero Calibration mode is selected during installation, the unit automatically calibrates the zero altitude point. This automatically compensates for different cable lengths and different antenna installation heights above the ground that would otherwise bias the altitude reading. 2.1.3 On Ground Operation While on the ground, the unit is susceptible to erroneous readings caused by signals returned from nearby buildings or personnel. Utilization of the strut input allows the unit to ignore these erroneous signals and report zero feet. The “Strut” bit of the status byte (see section 4.1.2.1.4) provides an indication of the input signal. 2.1.4 Normal Operation When the unit detects a locked signal and does not have a strut indication (i.e. – aircraft in the air), it reports altitude with the “Signal” bit indicating locked. If unusual terrain, aircraft orientation, or environmental conditions prevent a stable received signal, the “Signal” bit of the status word indicates unlocked. 2-1 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 2.2 System Limitations 2.2.1 Terrain At altitudes above 1500 feet, terrain with poor reflectivity may cause the unit to unlock. Examples of unfavorable terrain are dry, loose soil, (e.g. - tilled farmland), or sand. 2.2.2 Excessive Pitch/Roll An excessive pitch or roll attitude may also cause the system to unlock. This sensitivity increases with altitude. In general, below 1500 feet a 30 degree bank is tolerated. Above 1500 feet, the aircraft should be maintained within a 20 degree bank for proper operation. If the unit unlocks due to marginal conditions, it will automatically relock when a signal sufficient for ranging is detected. 2.2.3 Rapid Descent In cases of extremely rapid descent, both the response time of the system and pitch of the aircraft may prevent normal operation. At a descent rate of 1500 feet/minute or less, the RA-4000 system provides normal operation below 2000 feet. 2.2.4 Response Time When flying the RA-4000 system over rapidly changing terrain, e.g., a cliff or ravine, the system is limited by the 100 ms maximum response time of the unit. Note: The RA-4000 system surveys ground directly below the aircraft, and should not be relied on as either a forward looking or warning device. 2-2 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 2.3 Specifications Specifications for the RA-4000 system are listed in Tables 2-1 through 2-3. Table 2-1: System Technical Characteristics Parameter Type Compatible Antennas Altitude Range Altitude Accuracy Frequency Range Sweep Frequency Input Voltage Input Current Max. Inrush Current Altitude Output, Rate Altitude Latency Operating Temperature Self-Test / Reset Environmental Certifications Value Dual antenna, FMCW 1) FreeFlight P/N 9-1203-115-00 2) EDO P/N DM PN19-2-1 -20 to 2000 feet 0 to 100 feet +/- 3 feet 100 to 500 feet +/- 3% 500 to 2000 feet +/- 5% 100 MHz sweep 4.25 - 4.35 GHz 100 Hz 20-36 VDC (Internal fuse and reverse polarity protection) 400 mA Max @ 28 VDC (steady-state) 7 A for 1 ms @ 28 VDC 25 Hz less than 100 ms (63% of final value) -55°C to +70°C On system power-up DO-160E TSO-C87, DO-178B Level C Table 2-2: RA-4000 Physical Characteristics Parameter Weight Height Length (Including mounting flange) Width Connectors Value 1.9 lb 3.06” 6.78” 3.15” 2 each TNC antenna connectors 1 each 22 pin circular connector Table 2-3: Antenna (P/N 9-1203-115-00) Physical Characteristics Parameter Quantity Weight Dimensions Value 0.3 lbs (0.6 lbs total) 3.5" W x 3.65" L x .15" H 2-3 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 2.4 Component and Accessory Part Numbers Each RA-4000 unit is shipped individually, as indicated in Table 2-4. Two antennas and associated wiring are also required for installation. An Installation kit is available from FreeFlight, as indicated in Table 2-5. The items listed in Table 2-6 are required, but not supplied by FreeFlight. Table 2-4: RA-4000 Install Kit ITEM FREEFLIGHT P/N 84560-XX RA-4000 R/T Unit QUANTITY 1 required Table 2-5: Optional FreeFlight Install Kit and Parts ITEM Optional Installation Kit Coax Cable RG-142 B/U (30 ft) Antennas Connector TNC 22 Pin connector RA-4000 Series Connector Backshell Strain Relief FREEFLIGHT P/N 84933-00 0123-0012-00 9-1203-115-00 0129-0017-00 84443 84444 QUANTITY 1 required 1 per kit 2 per kit 4 per kit 1 per kit 1 per kit Note: EDO Corporation’s Radar Altimeter Antenna (EDO P/N PN19-2-1) is also compatible with FreeFlight Systems RA-4000 Radar Altimeter Unit. These antennas are not sold by FreeFlight Systems and must be purchased from the manufacturer directly or from any EDO antenna dealer. Refer to the manufacturer’s documentation for the specifications for these antennas. Table 2-6: Other Accessories ITEM System Wiring Circuit Breaker System Indicator Mounting Tray for altimeter FREEFLIGHT P/N N/A N/A N/A 1900-3121-X2 QUANTITY As required 2.5 License Requirements As installed in the aircraft, the radar altimeter does not require an FCC operator’s license. For information, reference FCC 47 CFR Part 87.89 Minimum operator requirements. 2-4 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 3 Electrical Interface Electrical interconnection to the RA-4000 is made via 22-pin connector. Refer to Table 3-1 for a description of the pin out. Table 3-1: RA-4000 Interface Pin out Pin Name Ground Ground Power In Power In Reset Reserved Reserved Strut Reserved 10 429 Speed Select* 11 12 13 14 15 16 17 18 19 20 21 22 ARINC-TXB* ARINC-TXA* Nav-TX Nav-RX PGM-EN Reserved Reserved Nav-Bias Nav-Com Nav-Com Nav-TXA Nav-TXB Function Ground Ground Aircraft voltage in Aircraft voltage in Reserved Strut (active low) Direction In In In Level Ground Ground 20-36 VDC 20-36 VDC NO CONNECT In Ground or open ARINC 429 Output Speed Select: Low Speed (default, pin open) High Speed (pin to ground) Navigation Port ARINC 429 Navigation Port ARINC 429 Navigation Port RS-232C Transmit Navigation Port RS-232C Receive Reserved In Ground or open Out Out Out In In ARINC 429 ARINC 429 RS-232C RS-232C NO CONNECT RS-485 100 ohm ground connection Navigation Port Ground Navigation Port Ground Navigation Port Serial RS-485/422 Navigation Port Serial RS-485/422 Out Out RS-485 Ground Ground Ground RS-485/422 RS-485/422 *Only applicable to part number 84560-02. 3.1 Ground Aircraft ground is connected on two pins. 3.2 Power In Aircraft power of 20-36 VDC is connected on two pins. 3.3 Reset This circuit is reserved for factory test purposes only. Do not connect. 3-1 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 3.4 Strut Input The Strut signal is an active low input. That is, the input should be grounded when the aircraft is on the ground. 3.5 Nav TX/RX The Nav-TX/RX lines use RS-232C signal levels. The RS-232C Nav-TX output carries the same data as the RS-485/422 Nav-TXA/TXB pair. The Nav-TX/RX lines are used to initiate the Altitude Zero Calibration function and to reprogram the unit via serial RS232C protocol. Note that it may be advantageous to route these lines to a point which facilitates shorting them for the Altitude Zero Calibration (see 6.5.1). If this is done, care should be taken that the lines do not accidentally short during normal flight. During normal operation after the Zero Calibration has been accomplished, these lines should not be connected. 3.6 PGM-EN The Program-Enable input is used to reprogram the unit. Do not connect in normal operation. 3.7 Nav-Bias This pin provides a 100 ohm resistive ground connection for the RS-485 communications circuit. 3.8 Nav-Com These connections provide a direct ground reference, if desired. 3.9 Nav-TXA/TXB Used as the primary data interconnect, these pins are driven by an LTC485 device. 3.10 ARINC-TXA/TXB ARINC 429 labels 164, 165, and 377 are transmitted on this interface at a rate of 25 Hz. Cabling should shielded twisted pair with shield grounded to aircraft and radar altimeter chassis. 3.11 ARINC Speed Select This pin is used to configure the unit to output low-speed (12 kbps) or high-speed (100 kbps) ARINC 429 data. If this pin is left open (default) the system will output low-speed ARINC data. If the pin is connected to ground, the system will output high-speed ARINC data. 3-2 Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 4 Functional Interfaces The FreeFlight Systems Radar Altimeter provides serial RS-232/422/485 interfaces and an ARINC 429 interface (Part Number 84560-02 only). The following sections describe the protocols used. 4.1 RS-232/422/485 Interface 4.1.1 Data Rate Data is transmitted in multi-byte packets at 56,000 baud (LSB first, 8 data bits, one start, one stop, no parity). System altitude packets are output at a rate of 25 Hz. 4.1.2 Protocol Definition Note: The information in this section is intended for engineering personnel and is not required for installation. 4.1.2.1 Packet Structure Each packet conforms to the following structure: Field Content DLE 0x10 ID 0xDF LEN 0x03 DATA 3 bytes CHECKSUM 1 byte DLE 0x10 ETX 0x03 4.1.2.1.1 DLE (Data Link Escape Character) Fixed byte = 0x10. 4.1.2.1.2 ID (Identification) Fixed byte = 0xDF. 4.1.2.1.3 Len (Length) Fixed byte = 0x03. 4.1.2.1.4 Data Three data bytes are defined as follows: Table 4-1: Data Field Definition Byte Definition Altitude High byte of a 2-byte binary field. (Units: Feet; Range: -20 to 2500) Altitude Low byte of a 2-byte binary field. Status Byte (See Table 4-2) Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F Table 4-2: Status Byte Bit Definition Bit 0 – Altitude 1 – Self Test 2 – Status 3 – Invalid 4 – Strut 5 – Reserved 6 – Reserved 7 – Reserved High (1) Indication Ascending Test in progress Unit Failure Unlocked / Invalid output De-asserted (In air) Low (0) Indication Descending Normal operation Normal operation Locked / Valid output Asserted (On ground) 4.1.2.1.5 Checksum This is the one-byte 2’s complement of the sum of all the data bytes, including the packet ID and LEN bytes (i.e. 0xDF03). Refer to Table 4-3 for a sample packet with normal status (descending, locked, and good status) and an altitude of 1000 feet. Table 4-3: Sample Packet at 1000’ Byte Value DLE 0x10 ID 0xDF LEN 0x03 Alt Hi Alt Lo Status 0x03 0xE8 0x00 Chk 0x33 DLE 0x10 ETX 0x03 4.1.2.1.6 DLE (Data Link Escape Character) Fixed byte = 0x10. 4.1.2.1.7 ETX (End Of Text Character) Fixed data byte = 0x03. 4.1.2.2 DLE Stuffing This protocol requires that an occurrence of the DLE (0x10) character in either the data or checksum must be followed by another DLE character. The receiver therefore, should remove, or “unstuff”, the second DLE character when two are received in sequence. Note that the “unstuffing” should occur prior to calculation of the checksum. Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 4.2 ARINC 429 Interface This section applies to part number 84560-02 only. 4.2.1 Data Rate All ARINC 429 labels are transmitted at either low or high speed ARINC baud rates as configured at installation time (see section 3.11) and are transmitted at a rate of 25 Hz. 4.2.2 Protocol Definition Note: The information in this section is intended for engineering personnel and is not required for installation. 4.2.2.1 Parity The parity bit of all labels is set to odd parity. 4.2.2.2 Source/Destination Indicator (SDI) The SDI of all labels is set to 00. 4.2.2.3 ARINC 429 Labels The following labels are transmitted: Label (octal) 164 165 377 Description SSM Non-Fault Fault Radio Altitude (Binary) NCD/NORM FAIL Radio Altitude (BCD) NCD/NORM N/A* Equipment ID NORM NORM *In case of a failure, label 165 is not transmitted. Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 5 Mechanical 5.1 RA-4000 Mounting The mounting requirements for the RA-4000 are illustrated in Figure 5-1. 5.2 Connectors Interfaces to the RA-4000 are provided through three connectors as described below in Table 5-1. Table 5-1: Connector Descriptions Function Description Aircraft interconnections This 22-pin circular connector mates with AMPHENOL P/N 10-565995-231N. This TNC connector mates with AMPHENOL P/N 225554-6 This TNC connector mates with AMPHENOL P/N 225554-6 TX Antenna RX Antenna FRONT RA-4000 NOTE: NOT TO SCALE INSTALLATION DIMENSIONS FreeFlight Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F Figure 5-1: RA-4000 Installation Drawing Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 5.3 Antenna Mounting Refer to Figure 5-2 for mounting information for antenna P/N 9-1203-115-00. All dimensions are specified in inches. Figure 5-2: Antenna (P/N 9-1203-115-00) Installation Drawing Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 6 Installation 6.1 General Information This chapter contains suggestions and factors to consider before installing an RA-4000 radar altimeter into an aircraft. Adherence to the suggestions will assure satisfactory performance from the system. 6.2 Unpacking and Inspecting Equipment Exercise care when unpacking each unit. Make a visual inspection of each unit for evidence of damage incurred during shipment. If a claim for damage is to be made, save the shipping container to substantiate the claim. When all equipment and the installation kit have been inspected, save the packing material and container in case the unit is to be stored or reshipped. See paragraph 2.4 for equipment and optional parts supplied. 6.3 Equipment Limitations For a compliant installation in accordance with the Technical Standard Order (TSO) and the Federal Aviation Regulations (FAR), the RA-4000 installation must meet the following requirements: “The conditions and tests required for TSO approval of this article are minimum performance standards. It is the responsibility of those desiring to install this article either on or within a specific type or class of aircraft to determine that the article, when installed, performs in accordance with the design specifications that meet this TSO. The article may be installed only if further evaluation by the applicant documents an acceptable installation and is approved by the Administrator.” RA-4000 must be connected to a display in a manner that yields no additional inaccuracies and with maximum additional latency of 80 ms (TSO-C87 §2.1). Added display inaccuracies trade with latency at a rate of ±1 ft to 40 ms; i.e., a display introducing ±1 ft of presentation error requires that the permissible installation/display component of latency decreases from 80 ms to 40 ms The display connected to the RA-4000 must utilize a failure warning indicator plainly discernible under all normal flight conditions (TSO-C87 §2.6b) driven by the status and the invalid bit of the RA-4000 status byte (see Table 4-2: Status Byte Bit Definition). The antenna installation must comply with the specifications in Section 6.4 Antenna Installation. Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 6.4 Antenna Installation 6.4.1 Antenna Cable Selection The antenna cables must have a certain minimum and maximum length for the system to perform accurately and comply with the TSO. The absolute minimum cable length is limited by the required minimum signal propagation delay caused by the cable and the antenna height above the ground when the aircraft is on the ground. The absolute maximum cable length is limited by the maximum allowable attenuation of the signals caused by the cable. Table 6-1: Propagation Delay and Attenuation of the Antenna Cable Min Total Propagation Delay (ns) 31 Max Attenuation (dB) 8.5 Table 6-2 shows typical values of propagation velocities, attenuations, and the minimum bend radius for commonly used cable types. Consult the cable manufacturer’s specifications for the exact values for the cables used in the installation. Table 6-2: Typical Antenna Cable Lengths Cable RG-142 RG-393 Min Total Length1 (ft) 21.0 21.0 Max Total Length2 (ft) 28.8 47.8 Min Bend Radius3 (in) Propagation Velocity (c) 69.4 % 69.4 % Attenuation/100’ (dB) @ 4.35 GHz 29.5 17.8 Note: Total length refers to the combined lengths of the TX and the RX cables. The minimum cable length specified assumes that the antennas are mounted 18” above the ground, resulting in a 3 ns return delay (The propagation delay in air is approximately 1 ns per foot). If the manufacturer’s data indicates a different propagation velocity than the one given in Table 6-2 the minimum cable length must be recomputed by the installer. If the manufacturer’s data indicates a different attenuation than the one given in Table 6-2 the maximum cable length must be recomputed by the installer. The manufacturer specified minimum bend radius may differ. 6.4.2 Antenna Mounting Requirements Refer to Figure 5-2 for mounting instructions. For proper performance and TSO compliance of the RA-4000, the radar altimeter antennas must be installed according to the following rules: Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F Antennas should be mounted parallel to the ground within a pitch angle of 6° when the aircraft is in level flight. Antennas should be mounted with the arrows pointing forward. They may be mounted side-by-side or in-line. If the antennas are mounted in-line, which is the preferred configuration, the transmit antenna should be mounted in front of the receive antenna. The angle between the pitch of both antennas should not exceed 6°. The antennas should be mounted such that no protrusion is visible to either antenna within a 60-degree cone below the aircraft. Antennas should be mounted at least 18" apart and within 40" of each other. The antenna height above the ground when the aircraft is on the runway should be more than the separation distance between the two antennas. Antennas should be mounted as close to the aerodynamic center of the aircraft as possible to reduce the effects of aircraft attitude on the altitude measurement. Antennas should not be mounted closer than 3’ to a DME, transponder, ADF or VHF antenna. During installation, avoid locations near high heat sources or where fuel, oil or excessive moisture may collect. Bond and shield all parts of the aircraft electrical system such as generators and ignition systems. 6.5 RA-4000 Installation The RA-4000 unit installation layout is shown in Figure 5-1. Route all data and power cables away from circuits carrying high current, pulse-transmitting equipment, 400 Hz circuits and other sources of interference. Do not route with ADF antenna cables. Note: Aircraft which exhibit electrical noise on the airframe or have surfaces or panels which are not properly bonded can cause the altimeter to attempt to "relock" above 2000 feet AGL, thus causing erratic altitude output. Thorough bonding of all control surfaces, gear doors, access panels, etc. should cure the symptom, but in certain extreme circumstances, it may be necessary to install an on/off switch to disable the unit above 2000 feet. This condition is only noticeable above 2000 feet and does not degrade performance below 2000 feet AGL. Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F 6.5.1 Altitude Zero Calibration The RA-4000 should be calibrated to account for the antenna height above ground when a zero foot altitude is desired. This procedure should be performed once on initial install of the unit or after servicing the unit. Reflections due to surrounding obstacles may cause inaccurate calibration. It is recommended to Zero the RA-4000 in an open area away from buildings, trees, or other large reflecting surfaces to improve accuracy. Note: If this procedure is not performed on install, after service, or is improperly performed, altitude may not be correct. 1. 2. 3. 4. 5. 6. 7. 8. Remove or disable the Strut input to the system. Clear all obstacles from around aircraft (including personnel). Turn unit on and let run for a minimum of 5 minutes to warm up. Turn off unit and all aircraft power. Short together RS-232C navigation port TX and RX pins. Switch power on for approximately 30 seconds. Switch power off and remove the short from the TX and RX lines. Switch power on. After the self-test is complete, the unit should now output 0' while on ground. 9. Test and repeat as necessary. 10. Restore the Strut input, if necessary. 6.5.2 Pre-Flight Check List 1. Turn on power (after starting engines). 2. Verify the unit self-tests for approximately 20 seconds (during which it displays 40±3 feet and sets the self test flag). 3. After the self-test mode, the unit should output 0 feet while the aircraft is on the ground. 6.5.3 Final Testing 1. During takeoff observe AGL and verify that it is increasing while the aircraft is climbing. 2. After aircraft exceeds 2000 feet AGL verify that unit indicates “unlocked”. 3. With the aircraft above 3000 feet AGL in an open area: a. Put the aircraft into a 500-foot per minute descent. b. The unit should lock and start outputting valid altitude by 2000 feet AGL. Equipment Installation Manual RA-4000 Series Radar Altimeters P/N 84629, Rev F Appendix A – Environmental Categories Refer to Table A-1 for a summary of RA-4000 Test Categories. Table A-1: DO-160E Test Categories Environmental Test Temperature and Altitude Temperature Variation Humidity Shock/Crash Safety Vibration Explosion Proofness Waterproofness Fluids Susceptibility Sand and Dust Fungus Salt Spray Magnetic Effect Power Input Voltage Spike Audio Frequency Conducted Susceptibility – Power Inputs Induced Signal Susceptibility Radio Frequency Susceptibility Emission of Radio Frequency Energy Lightning, Induced Transient Susceptibility Lightning Direct Effects Icing Electrostatic Discharge Fire, Flammability DO-160E Section Category Compliance Method 10 11 12 13 14 15 16 17 18 D2 S Curve C & U2 n/a n/a n/a n/a n/a 19 ZC 20 RR 21 22 A2XXX 23 24 25 26 n/a n/a FreeFlight Systems 3700 Interstate 35 South Waco, TX 76706-3756 U.S.A. 1 (254) 662-0000 1 (800) 487-4662
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