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The KRA 405B radar altimeter (RADALT) is a lightweight, solid-state, airborne altimeter that provides accurate altitude measurements above terrain during various portions of flight. With more than 10,000 produced and sold to date and more than four million service hours, the KRA 405B RADALT has proven to be one of the most reliable and industry proven radar altimeters available.


N KRA 405B RADAR ALTIMETER INSTALLATION MANUAL 2. B. A calibration in an excessively noisy environment will not be accepted by the KRA 405B. A post calibration altitude of thirty to one hundred feet indicates a failed calibration. If this condition occurs, the calibration must be completed in a different location. GENERAL In most cases altimeter installations that closely follow the suggestions of this manual will need no special equipment to check the integrity of the system. The steps of Paragraph 2.6.

14 Some part numbers may not be currently available. Consult the current Honeywell catalog or contact a Honeywell representative for equipment availability. The KRA 405B System also may consist of previously TSO certified components from the following list. However the use of any configurations other than the preferred configuration will result in reduced functionality of the system. MODEL KA 54 DESCRIPTION RETROFIT ANTENNA Upon use of the above antennas or any other configurations, the STC certification will be the sole responsibility of the customer and/or the installing agent. Please contact a field representative for additional information. 1.1 DESCRIPTION OF EQUIPMENT The KRA 405B Radar Altimeter System provides the pilot with dependable, accurate AGL (altitude above ground level) information during the approach phase of a flight. The system has the capability of alerting the pilot when a predetermined altitude (decision height) is reached. The system also provides altitude information to the flight control system during the approach. The KRA 405B Radar Altimeter (P/N ), in addition to providing an ARINC 552A output for Auxiliary Out 2, has the ability to take a DH input from an EFIS or KNI 415/416 and generate an audio signal (refer to section 1.3. C. KRA 405B RECEIVER/TRANSMITTER for tone generator circuit specifications). The KRA 405B Radar Altimeter (P/N /-4001) provides enhanced accuracy ( 2 feet) below 100 feet using the digital 429 Buss labels 164 and 165. Both KRA 405B versions P/N and P/N with software 01/04, 02/04 or higher will not report negative values of altitude on the ARINC 429 digital bus unless expressly configured to do so. This feature is required for installations with Honeywell EFIS 40/ 50. One of these two unit versions (-0101 or -0202) must be used when interfacing the digital output of the KRA 405B to equipment which expect non-negative values. The KRA 405B determines the altitude above ground level (AGL) by transmitting a signal to the ground then processing the reflected signal. The altimeter outputs the altitude information as analog voltages and in ARINC 429 digital format. Page 1-2

30 The Editing window will be removed and the Memory Definitions window will again be displayed, to allow further changes, and the Main screen will display a message describing the changed parameter. After completing the all changes to the settings, refer to the KPA 900 Operators Guide P/N XX for instructions to complete the programming of the Configuration Module. Honeywell recommends that the programmed module be verified before installation. Exit the KPA 900 program, re-invoke it, read the programmed module, and verify the correctness of the settings. This step will ensure that the programming operation was successful. B. ZERO FEET OFFSET The KRA 405B Receiver/Transmitter DOES NOT require an Aircraft Installation Delay (AID). The KRA 405B R/T has provisions to calibrate to zero feet during the installation. After this calibration, the KRA 405B will provide a radar altitude of basically zero feet (see note below) when the aircraft is taxiing or stationary on the ground. NOTE: All versions of the KRA 405B with 01/03 or 02/03 software and -2001/-4001 version units with 01/03 or higher software may provide slight negative values of altitude when the aircraft is taxiing or at rest. This is normal operation as the altitude calculation may vary around zero at plus and minus the system accuracy. All other unit and software configurations will "clamp" negative calculation results to zero feet, and never go negative. The configuration module supplied offset is applied to the altitude data after the "clamp", so all unit configurations have the capability to produce negative results. The Honeywell EFIS 40 and EFIS 50 systems (and possibly other systems) will not display negative altitudes received on the digital bus. When the Honeywell EFIS detects a negative altitude value, it "declutters" or blanks the altitude information from the displays. The EFIS will also rebroadcast incorrect Radio Altitude information on the general-purpose bus. All versions of units with 01/03 or 02/03 software and -2001/-4001 version units with 01/03 or higher software must not interface to the EFIS 40 or EFIS 50 systems via the ARINC 429 bus. All flavors and software versions of he KRA 405B must not be configured with a zero foot offset when interfacing the EFIS via the digital bus. Interfaces via any of the analog outputs will function correctly. Page 2-4

34 c. For direct mounted units perform the following steps: (2) Dual Installation 1. Mark, punch, then drill mounting holes, being careful not to damage adjacent equipment or cables. 2. Using four (4) #6-32 screws, secure the unit in the position selected. The KRA 405B R/T fulfills all altitude accuracy specifications when in dual installation mode. Mutual interaction is not operationally significant. See FIGURE 2-7 DUAL RADAR ALTIM- ETER SYSTEM TYPICAL ANTENNA INSTALLATIONS. The secondary unit in a dual installation is selected by a hardware strap as described in Note 3 of FIGURE 2-17 KRA 405B RADAR ALTIMETER SYSTEM INTERCONNECT. NOTE: The operation of the primary unit is no different than the operation of a unit in a single radar altimeter installation. (3) Zero Feet Calibration The KRA 405B Receiver/Transmitter DOES NOT require an AID. The KRA 405B R/T has provisions to calibrate to zero (0) feet during installation, such that the radar altitude is 0 feet when the aircraft is taxiing or stationary on the ground. Refer to section 2.6. A. POST INSTALLATION CALIBRATION for the calibration procedure. There are provisions to allow the indicated 0 foot point to be offset from the calibrated 0 foot point to accommodate installations where the indicator reads 0 feet at the point the wheels first touch down. The offset is then stored in a configuration module. B. KNI 415/416 INDICATOR (1) Plan a location on the aircraft panel that is clearly visible to the pilot with the least deviation from his normal scan pattern while in an approach. (2) Avoid mounting the unit close to heater vents or other high heat sources. Page 2-8

36 The UB Corporation, Sensor Systems, Dorne and Margolin (EDO) and Comant Industries antennas can be purchased directly from the respective manufacturers at the following addresses: (1) UB Corporation 9829 Wilsky Blvd. Tampa, FL Telephone: (2) Comant Industries, Inc Park St. Santa Fe Springs, CA Telephone: (3) Sensor Systems, Inc Fullbright Ave. Chatsworth (LAX), CA Telephone: (4) Dorne and Margolin EDO Antenna Products and Technologies 455 Commack Road Deer Park, NY Telephone: D. PLANNING THE ANTENNA INSTALLATION Many factors are important when planning an optimum antenna installation for use with a radar altimeter system. Careful planning and attention to detail are absolutely necessary. Failure to install the antennas correctly will cause degradation in system performance. Antennas should be mounted near point of aircraft rotation. This reduces the effect of pitch and roll attitude in altitude readings during approach and landing. Antennas must be mounted close enough to the R/T so that the antenna cable length does not decrease system sensitivity. Refer to TABLE 1-2 CABLE INSTALLATIONS for minimum and maximum lengths and minimum bend radii for cables. Page 2-10

37 Antennas should be pointing straight down within plus or minus 6 when the aircraft is in a level flight attitude. Antennas mounted more than 6 off the vertical will exhibit erratic operation on the ground. See FIGURE 2-7 DUAL RADAR ALTIMETER SYS- TEM TYPICAL ANTENNA INSTALLATIONS for examples of this type of installation. Antennas may be mounted in-line or side-by-side. The in-line mounting is the preferred choice of the two. When using sideby-side installations, the antennas should be mounted on a flat surface of the aircraft. The angle between the antenna centerlines should be less than 6. Failure to correctly position antennas will result in erratic operation on the ground, i.e., the needle will fluctuate as much as 20 feet, dependent upon the angle between centerlines. Airborne operation will be satisfactory. Antennas should be mounted no less than 20 inches apart (measure from center to center) in order that leakage between the antennas remains at a tolerable level. The pointer may not stow above 2500 feet if the leakage between the antennas is too great. Antennas should not be separated by a distance greater than the antenna height above the terrain at touchdown. If the antennas are separated by more than this distance, sufficient terrain area is not illuminated for ground level operation. The antennas should be mounted closer than the antenna height above the terrain (but no less than 20 inches) if the angle between the antennas is greater than 6. Antenna locations should provide 120 clearance cones. No aircraft projection or other antenna should lie within these cones. A fixed object in the cone could cause the altimeter to lock on to a single altitude while a moving projection (gear, flaps, etc.) could cause erratic operation. Surface area between antennas should be free from seams or other discontinuities. NEVER mount an antenna directly on a seam. If antennas must be separated by a seam, make sure that the two pieces of aircraft skin are electrically bonded together by adding bonding straps (i.e., have multiple straps across seam separating the two antennas). Failure to bond properly can cause loss in system sensitivity and/or cause the pointer to momentarily come into view above 2500 feet AGL (this phenomenon is commonly called "peeking"). Page 2-11


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