Equipment Installation Manual
RA-4000/RA-4500 Radar Altimeters
EQUIPMENT INSTALLATION MANUAL
FOR
FREEFLIGHT SYSTEMS
RA-4000 AND RA-4500 RADAR ALTIMETERS
Document No. 84629
Revision J
FreeFlight Systems
3700 Interstate 35 South
Waco, TX 76706-3756 U.S.A.
1 (254) 662-0000
1 (800) 487-4662
October 7, 2010
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Equipment Installation Manual
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Introduction
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Description
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Electrical Interface
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Functional Interfaces
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Mechanical
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Installation
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Environmental Categories
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Equipment Installation Manual
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Table of Contents
1 INTRODUCTION....................................................................................................... 1-1
1.1 REFERENCE DOCUMENTS......................................................................................... 1-2
1.2 TABLE OF ACRONYMS & ABBREVIATIONS ............................................................... 1-3
2 DESCRIPTION........................................................................................................... 2-1
2.1 OPERATIONAL MODES ............................................................................................. 2-1
2.2 SYSTEM LIMITATIONS .............................................................................................. 2-2
2.3 SPECIFICATIONS ....................................................................................................... 2-3
2.4 IN-FLIGHT CONDITIONS ........................................................................................... 2-4
2.5 ALTITUDE ROUNDING .............................................................................................. 2-5
2.6 COMPONENT AND ACCESSORY PART NUMBERS ...................................................... 2-6
2.7 LICENSE REQUIREMENTS ......................................................................................... 2-7
3 ELECTRICAL INTERFACE.................................................................................... 3-1
3.1 GROUND .................................................................................................................. 3-2
3.2 POWER IN ................................................................................................................ 3-2
3.3 RESET ...................................................................................................................... 3-2
3.4 STRUT INPUT ........................................................................................................... 3-2
3.5 NAV TX/RX ............................................................................................................ 3-2
3.6 NAV-BIAS ................................................................................................................ 3-2
3.7 NAV-COM ................................................................................................................ 3-2
3.8 NAV-TXA/TXB ...................................................................................................... 3-2
3.9 ARINC-TXA/TXB ................................................................................................. 3-2
3.10 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 RADAR ALTIMETER MOUNTING............................................................................... 5-1
5.2 CONNECTORS ........................................................................................................... 5-1
5.3 ANTENNA MOUNTING .............................................................................................. 5-3
5.4 OPTIONAL MOUNTING TRAY ................................................................................... 5-4
6 INSTALLATION........................................................................................................ 6-1
6.1 GENERAL INFORMATION .......................................................................................... 6-1
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6.2 UNPACKING AND INSPECTING EQUIPMENT .............................................................. 6-1
6.3 EQUIPMENT LIMITATIONS ........................................................................................ 6-1
6.4 ANTENNA INSTALLATION ........................................................................................ 6-1
6.5 RADAR ALTIMETER INSTALLATION ......................................................................... 6-5
6.6 POST-INSTALLATION TESTING ................................................................................. 6-8
7 - ENVIRONMENTAL CATEGORIES .................................................................... 7-1
7.1 DO-160E TEST CATEGORIES FOR P/N 84560-0X-XXXX ....................................... 7-1
7.2 DO-160E TEST CATEGORIES FOR P/N 84560-1X-XXXX ....................................... 7-2
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List of Figures
Figure 1-1: Radar Altimeter System Block Diagram ...................................................... 1-1
Figure 5-1: Radar Altimeter Installation Drawing........................................................... 5-2
Figure 5-2: Antenna (P/N 9-1203-115-00) Installation Drawing .................................... 5-3
Figure 5-3: Mounting Tray Installation Drawing ............................................................ 5-4
Figure 6-1: Aircraft Bottom View ................................................................................... 6-4
Figure 6-2: Antenna Orientation...................................................................................... 6-4
Figure 6-3: Typical Radar Altimeter to RAD-40 Interconnection Diagram.................... 6-6
Figure 6-4: Typical Radar Altimeter to EFIS/MFD Interconnection Diagram ............... 6-7
List of Tables
Table 2-1: System Technical Characteristics................................................................... 2-3
Table 2-2: Physical Characteristics.................................................................................. 2-4
Table 2-3: Antenna (P/N 9-1203-115-00) Physical Characteristics ................................ 2-4
Table 2-4: In-Flight Conditions ....................................................................................... 2-4
Table 2-5: Altitude Rounding .......................................................................................... 2-5
Table 2-6: Radar Altimeter .............................................................................................. 2-6
Table 2-7: Optional Installation Kit with Antennas......................................................... 2-6
Table 2-8: Optional Installation Kit without Antennas.................................................... 2-6
Table 2-9: Other Accessories........................................................................................... 2-6
Table 2-10: Optional Indicator......................................................................................... 2-7
Table 2-11: Optional Indicator Installation Kit ............................................................... 2-7
Table 2-12: Optional Cable Delay ................................................................................... 2-7
Table 3-1: Radar Altimeter 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 4-4: ARINC 429 Output Labels............................................................................. 4-3
Table 5-1: Connector Descriptions .................................................................................. 5-1
Table 6-1: Propagation Delay and Attenuation of the Antenna Cable ............................ 6-2
Table 6-2: Typical Antenna Cable Lengths ..................................................................... 6-2
Table 7-1: DO-160E Test Categories (P/N 84560-0X-XXXX) ...................................... 7-1
Table 7-2: DO-160E Test Categories (P/N 84560-1X-XXXX) ...................................... 7-2
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1 Introduction
This manual contains installation data and specifications for the FreeFlight Systems RA4000 and RA-4500 Radar Altimeters (P/N 84560-XX-XXXX), hereafter referred to as
the radar altimeter. The radar altimeter meets the requirements for a TSO-C87 Radar
Altimeter with Precision Equipment output and the requirements for category A/L/A1/A
Radar Altimeters of ETSO-2C87 (software version 300A and above only).
The radar altimeter 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 RA-4000 and the RA-4500 are functionally the same with the exception that the RA4500 contains ARINC 429 output in addition to the RS-485/422 and RS-232C output of
the RA-4000.
The system consists of three Line Replaceable Units (LRUs): the radar altimeter
Receiver/Transmitter (R/T) Unit and two antenna units (refer to section 2.6). Refer to
Figure 1-1 for a system block diagram.
I/O
RA-4000
or
RA-4500
Transmit
Power In
Strut Switch In
Altitude out:
- Serial RS-485/422
- Serial RS-232C
- ARINC 429
Receive
Figure 1-1: Radar Altimeter System Block Diagram
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1.1 Reference Documents
Document Number
RTCA/DO-160E
RTCA/DO-178B
TSO-C87
ETSO-2C87
RTCA/DO-155
EUROCAE/ED-30
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.
European Technical Standard Order; Low Range Radio Altimeters,
24.10.03
Minimum Performance Standards Airborne Low-Range Radar Altimeters;
1-Nov-1974.
Minimum Performance Specification for Airborne Low Range Radio
(Radar) Altimeter Equipment, March 1980 including Edition 2, June 1,
1980
Mark 33 Digital Information Transfer System; May 17, 2004
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1.2 Table of Acronyms & Abbreviations
The following acronyms and abbreviations are used throughout this document.
Abbreviation
A
AGL
BCD
dB
EFIS
ETSO
EUROCAE
FAR
FCC
FFS
FMCW
FMS
Hz
LRU
LSB
MFD
MHz
ms
NCD
NMS
ns
NVG
P/N
R/T
RX
SDI
SSM
TNC
TSO
TX
VCO
VDC
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Definition
Ampere
Above Ground Level
Binary Coded Decimal
Decibels
Electronic Flight Instrument System
European Technical Standard Order
European Organization for Civil Aviation Equipment
Federal Aviation Regulations
Federal Communications Commission
FreeFlight Systems
Frequency Modulated Continuous Wave
Flight Management System
Hertz
Line Replaceable Unit
Least-Significant Bit
Multi-Function Display
Mega-Hertz
Milliseconds
No Computed Data
Navigation Management System
Nanoseconds
Night Vision Goggles
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
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2 Description
A complete system consists of a radar altimeter R/T unit (P/N 84560-XX-XXXX) and
two antennas (refer to section 2.6). The radar altimeter provides AGL altitude
information from -20 feet up to 2000 feet (up to 2500 feet with software version 300A
and above) maximum via computer interface. The altitude AGL is defined as the vertical
distance from the antennas to the terrain.
The 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. With software version
300A the system forces a valid altitude output of 0 foot if the strut indicates that the
aircraft is on the ground.
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.
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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
radar altimeter system provides normal operation below 2000 feet (below 2500 feet with
software version 300A and above).
2.2.4 Response Time
When flying the radar altimeter 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 radar altimeter system surveys ground directly below the aircraft, and
should not be relied on as a forward looking device.
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2.3 Specifications
Specifications for the radar altimeter system are listed in Tables 2-1 through 2-3.
Table 2-1: System Technical Characteristics
Parameter
Value
Type
Dual antenna, FMCW
Compatible Antennas
1) FFS P/N
2) EDO P/N
Altitude Range
-20 to 2000 feet (software version 200X)
-20 to 2500 feet (software version 300X)
Altitude Accuracy
0 to 100 feet +/- 3 feet
100 to 500 feet +/- 3%
Above 500 feet +/- 5%
Frequency Range
100 MHz sweep 4.25 - 4.35 GHz
Sweep Frequency
100 Hz
Output Power
100 mW
Input Voltage
20-36 VDC
(Resettable internal fuse and reverse polarity protection)
Input Current
400 mA Max @ 28 VDC (steady-state)
Max. Inrush Current
7 A for 1 ms @ 28 VDC
Altitude Output, Rate
25 Hz
Altitude Latency
less than 100 ms (63% of final value)
Operating Temperature
-55°C to +70°C
Altitude
50,000 ft (15.2 km) per DO-160E, Cat. D2
Rain
>16 mm/hr
Self-Test / Reset
On system power-up
FCC
Grant T7YRA4XXX with emission designator
100MFXN
Environmental
DO-160E, see section 7
Certifications
TSO-C87,
ETSO-2C87 (A/L/A1/A) (version 300A and above only),
DO-178B Level C
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DM PN19-2-1
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Table 2-2: Physical Characteristics
Parameter
Value
Weight
1.9 lb
Height
3.06”
Length
(Including mounting flange)
6.78”
Width
3.15”
Connectors
2 each TNC antenna connectors
1 each 22 pin circular connector
Table 2-3: Antenna (P/N 9-1203-115-00) Physical Characteristics
Parameter
Value
Quantity
2
Weight
0.3 lbs (0.6 lbs total)
Dimensions
3.5" W x 3.65" L x .15" H
2.4 In-Flight Conditions
The altitude accuracy specified in section 2.3 is met under the following conditions (per
TSO-C87 and ETSO-2C87 Category L):
Table 2-4: In-Flight Conditions
Parameter
Value
Horizontal Velocity
0 to 200 knots (0 to 340 ft/s or 100 m/s)
Vertical Velocity*
0 to 20 ft/s up to 100 ft
0 to 25 ft/s above 100 ft
Roll Angle
0 to ±20°
Pitch Angle
0 to ±20°
Extended Roll Angles
At bank angles from 20° to 30° the error
is less than 20% of the indicated altitude.
*Note: Any errors induced by the Doppler shift in the frequency of the returned signal due to
high vertical velocities are removed in software.
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2.5 Altitude Rounding
To reduce the noise in the altitude output on the digital outputs of the radar altimeter, the
altitude is rounded depending on the current altitude reading. Table 2-5 specifies the
altitude rounding performed by the radar altimeter.
Table 2-5: Altitude Rounding
Altitude (ft)
Rounded To Nearest (ft)
-20 - 119
1
120 - 199
2
200 - 499
5
500 - 999
20
1000 - 2099
50
2100+
100
Note: The radar altimeter meets the altitude accuracy requirements of TSO-C87 and
ETSO-2C87 as stated in Table 2-1 with this rounding included.
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2.6 Component and Accessory Part Numbers
Each radar altimeter unit is shipped individually, as indicated in Table 2-6. Two antennas
and associated wiring are also required for installation. Optional installation kits are
available from FreeFlight Systems, as indicated in Table 2-7 and Table 2-8.
Table 2-6: Radar Altimeter
ITEM
Radar Altimeter R/T Unit
FFS P/N
84560-X1-XXXX (RA-4000)
or
84560-X2-XXXX (RA-4500)
QUANTITY
1 required
Table 2-7: Optional Installation Kit with Antennas
ITEM
Optional Installation Kit
Coax Cable RG-142 B/U (30 ft)
Antennas (Sensor Systems S67-2002)
Connector TNC
22 Pin connector
Connector Backshell Strain Relief
FFS 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
Table 2-8: Optional Installation Kit without Antennas
ITEM
Optional Installation Kit
Coax Cable RG-142 B/U (30 ft)
Connector TNC
22 Pin connector
Connector Backshell Strain Relief
FFS P/N
84933-01
0123-0012-00
0129-0017-00
84443
84444
QUANTITY
1 required
1 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 Radar Altimeter Units. 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 2-9: Other Accessories
ITEM
FFS P/N
N/A
N/A
84947-00
System Wiring
Circuit Breaker (3A, slow-acting)
Mounting Tray for altimeter
QUANTITY
As required
1
1
FreeFlight Systems also offers an optional TSO-C87 certified Radar Altimeter Indicator,
called RAD-40, for either standard installations or NVG compatible installations (Table
2-10). This indicator is not required (but may be used as alternate indication of radar
altitude) for installations where the Radar Altimeter is connected to an EFIS. For stand-
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alone installations, the indicator is required. An optional installation kit for the indicator
is also available (Table 2-11).
Table 2-10: Optional Indicator
ITEM
RAD-40 Radar Altimeter Display (Standard)
RAD-40 Radar Altimeter Display (NVG)
FFS P/N
84939-00-XXXX
84939-10-XXXX
QUANTITY
1 optional
1 optional
Table 2-11: Optional Indicator Installation Kit
ITEM
Optional Installation Kit
Connector DB-25 Female
Connector Hood with Level
Mounting Screws
FFS P/N
84949-00
9-2190-188-10
9-2190-188-20
9-2804-068-10
QUANTITY
1 optional
1 per kit
1 per kit
1 per kit
FreeFlight Systems also offers a delay line that eliminates the need for the minimum
cable length requirement specified in section 6.4.1.
Table 2-12: Optional Cable Delay
ITEM
FFS P/N
85856-00
21’ Cable Delay
QUANTITY
1 optional
2.7 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.
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3 Electrical Interface
Electrical interconnection to the radar altimeter is made via 22-pin connector. Refer to
Table 3-1 for a description of the pin out.
Table 3-1: Radar Altimeter Interface Pin Out
Pin
Name
Function
Direction
Level
1
Ground
Ground
-
Ground
2
Ground
Ground
-
Ground
3
Power In
Aircraft voltage in
In
20-36 VDC
4
Power In
Aircraft voltage in
In
20-36 VDC
5
Reserved
No connect
6
Reserved
No connect
7
Reserved
No connect
8
Strut
9
Reserved
10
429 Speed
Select*
ARINC 429 Output Speed Select:
Low Speed (default, pin open)
High Speed (pin to ground)
11
ARINC-TXB*
Navigation Port ARINC 429
Out
ARINC 429
12
ARINC-TXA*
Navigation Port ARINC 429
Out
ARINC 429
13
Nav-TX
Navigation Port RS-232C Transmit
Out
RS-232C
14
Nav-RX
Navigation Port RS-232C Receive
In
RS-232C
15
Reserved
No connect
16
Reserved
No connect
17
Reserved
No connect
18
Nav-Bias
RS-485 100 ohm ground
connection
-
19
Nav-Com
Navigation Port Ground
-
Ground
20
Nav-Com
Navigation Port Ground
-
Ground
21
Nav-TXA
Navigation Port Serial RS-485/422
Out
RS-485/422
22
Nav-TXB
Navigation Port Serial RS-485/422
Out
RS-485/422
Strut (active low)
In
Ground or open
No connect
In
Ground or open
RS-485 Ground
*Only applicable to part number 84560-X2-XXXX.
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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.
3.4 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. 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 Nav-Bias
This pin provides a 100 ohm resistive ground connection for the RS-485 communications
circuit.
3.7 Nav-Com
These connections provide a direct ground reference, if desired.
3.8 Nav-TXA/TXB
Used as the primary data interconnect, these pins are driven by an LTC485 device.
3.9 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.
3.10 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.
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4 Functional Interfaces
The FreeFlight Systems Radar Altimeter provides serial RS-232/422/485 interfaces and
an ARINC 429 interface (Part Number 84560-X2-XXXX 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
1
2
3
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)
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October 7, 2010
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Equipment Installation Manual
RA-4000/RA-4500 Radar Altimeters
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)
While the unit is in self-test during the first 20 seconds after power up, bit 1 (Self Test) in
the status byte is set. In case of a system failure, such as a communications error or an out
of range temperature reading, bit 2 (Status) of the status byte is set. Bit 3 (Invalid) of the
status byte is set when the ground return is insufficiently strong to determine an accurate
aircraft altitude AGL or the altitude is above the maximum system altitude.
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.
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October 7, 2010
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Equipment Installation Manual
RA-4000/RA-4500 Radar Altimeters
4.2 ARINC 429 Interface
This section applies to model RA-4500 (P/N 84560-X2-XXXX) 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 3.10) 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:
Table 4-4: ARINC 429 Output Labels
Label (octal)
164
165
377
Description
Radio Altitude (Binary)
Radio Altitude (BCD)
Equipment ID
4.2.2.4 Sign/Status Matrix (SSM)
A SSM of “normal” (0b11) is transmitted in label 164 and a SSM of “above” (0b00) or
“below” (0b11) in 165 as long as the ground return is sufficiently strong to determine an
accurate aircraft altitude AGL and as long as the altitude is at or below the maximum
system altitude. While the unit is in self-test during the first 20 seconds after power up,
the SSM of label 164 and label 165 is set to “functional test” (0b10).
If the aircraft is above the maximum system altitude or an insufficient ground return
signal is measured, the SSM of labels 164 and 165 is set to “no computed data (NCD)”
(0b01). In case of a system failure, such as a communications error or an out of range
temperature reading, the SSM of label 164 is set to “failure” (0b00) and label 165 is not
transmitted at all.
The SSM of label 377 is always set to “normal” (0b00).
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October 7, 2010
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5 Mechanical
5.1 Radar Altimeter Mounting
The mounting requirements for the radar altimeter are illustrated in Figure 5-1. Mounting
information for antenna P/N 9-1203-115-00 is illustrated in Figure 5-2. Mounting
information for the optional radar altimeter mounting tray, P/N 84947-00, is illustrated in
Figure 5-3.
5.2 Connectors
Interfaces to the radar altimeter 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
P/N 84629, Revision J
October 7, 2010
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Figure 5-1: Radar Altimeter Installation Drawing
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October 7, 2010
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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
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October 7, 2010
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5.4 Optional Mounting Tray
Refer to Figure 5-3 for mounting information for the optional radar altimeter mounting
tray, P/N 84947-00. All dimensions are specified in inches.
Figure 5-3: Mounting Tray Installation Drawing
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October 7, 2010
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6 Installation
6.1 General Information
This chapter contains suggestions and factors to consider before installing a 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 2.6 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 radar altimeter 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.”
™ The Radar altimeter 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 radar altimeter 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 radar altimeter status byte (see Table
4-2).
™ The antenna installation must comply with the specifications in Section 6.4
Antenna Installation.
6.4 Antenna Installation
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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)
3
6
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.
1
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.
2
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.
3
The manufacturer specified minimum bend radius may differ.
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6.4.2 Antenna Mounting Requirements
Refer to Figure 5-2 for mounting information. For proper performance and TSO
compliance of the radar altimeter, the radar altimeter antennas must be installed
according to the following rules:
™ Antennas should be mounted parallel to the ground within a pitch angle of 6°
when the aircraft is in level flight.
™ Antennas must be mounted with the arrows pointing along the same line. See
Figure 6-1 and Figure 6-2. They should be mounted in-line although a side-byside configuration is also acceptable with the Sensor Systems antenna (P/N 91203-115-00). The EDO antenna may only be mounted in-line.
Note: The EDO antennas may only be mounted in-line and should not be
mounted side-by-side. Only the Sensor Systems antenna may be mounted side-byside.
™ 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 120-degree cone (±60 degrees) 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.
™ The base of the antenna should be properly grounded. The maximum resistance
should be less than 0.9 Ohms.
™ 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.
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October 7, 2010
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Figure 6-1: Aircraft Bottom View
Figure 6-2: Antenna Orientation
Arrows may point at each other, away from each other, or the same direction.
However, they must be positioned to point along the same center line.
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6.5 Radar Altimeter Installation
The radar altimeter 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 altimeter antenna cables 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 at lower altitudes.
*2500 feet AGL for software version 300A and above
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6.5.1 Display Interconnect
GND
25 Pin
Conn
B
22 Pin
Conn
RA-4XXX
3
21
22
20
28 VDC
A
25
13
11
17
RAD-40
6.5.1.1 RAD-40 Display
Figure 6-3 shows the typical display interconnection between the radar altimeter and the
optional FreeFlight Systems RAD-40 Radar Altimeter Display.
Figure 6-3: Typical Radar Altimeter to RAD-40 Interconnection Diagram
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GND
B
22 Pin
Conn
RA-4500
3
12
11
20
28 VDC
A
PWR
RXA
RXB
GND
EFIS / MFD
6.5.1.2 ARINC 429 Display
Figure 6-4 shows the typical display interconnection between the RA-4500 and an
ARINC 429 EFIS or MFD.
Figure 6-4: Typical Radar Altimeter to EFIS/MFD Interconnection Diagram
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6.5.2 Altitude Zero Calibration
The radar altimeter 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 radar altimeter 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 output of the radar altimeter 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.
6.6 Post-Installation Testing
6.6.1 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.
6.6.2 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.
*2500 feet AGL for software version 300A and above
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7 - Environmental Categories
Refer to Table 7-1 and Table 7-2 for a summary of radar altimeter test categories.
7.1 DO-160E Test Categories for P/N 84560-0X-XXXX
Table 7-1: DO-160E Test Categories (P/N 84560-0X-XXXX)
Environmental Test
DO-160E
Section
Category
Temperature and Altitude
Temperature Variation
Humidity
Shock/Crash Safety
Vibration
4
5
6
7
8
Explosion Proofness
Water Proofness
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
9
10
11
12
13
14
15
16
17
18
D2
B
B
B
S Curve C
& U2
n/a
W
n/a
n/a
n/a
n/a
Z
B
A
B
19
20
21
22
ZC
RR
M
A2XXX
23
24
25
26
n/a
n/a
A
C
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7.2 DO-160E Test Categories for P/N 84560-1X-XXXX
Table 7-2: DO-160E Test Categories (P/N 84560-1X-XXXX)
Environmental Test
DO-160E
Section
Category
Temperature and Altitude
Temperature Variation
Humidity
Shock/Crash Safety
Vibration
4
5
6
7
8
Explosion Proofness
Water Proofness
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
9
10
11
12
13
14
15
16
17
18
D2
B
B
A
S Curve C
& U2
E
W
n/a
n/a
n/a
n/a
Z
B
A
B
19
20
21
22
ZC
RR
M
A2XXX
23
24
25
26
n/a
n/a
A
C
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FreeFlight Systems
3700 Interstate 35 South
Waco, TX 76706-3756 U.S.A.
1 (254) 662-0000
1 (800) 487-4662