Cessna 400/800 Encoding Altimeter Service Manual

DISASSEMBLY PROCEDURES .................................•.. Electronic Components ......................................... . Mechanical Components ......................................... . Removal of Cover Assembly ....................................... . Plate and Printed Wiring Assembly, Disassembly From Encoding Altimeter ....... . Plate and Printed Wiring Assembly, Disassembly of Unit ................... . Capsule and ServoAssembly, Removal of ............................. . SECTION 6- DIAGRAMS SECTION 7- ILLUSTRATED PARTS LIST INTRODUCTION GENERAL ................................................. . FIGURE AND INDEX NUMBER COLUMN ........................... . PART NUMBER COLUMN ....................................... . DESCRIPTIVE COLUMN ....................................... . UNITS PER ASSEMBLY COLUMN ................................. . USABLE ON CODE COLUMN ..................................... . SECTION 8- EA-801A DIFFERENCE DATA SCOPE ..................................................... . EQUIPMENT SUPPLIED ......................................... . REFERENCE DATA ........................................... . FUNCTIONAL DESCRIPTION ..................................... . Page 5-1 5-1 5-1 5-1 5-2 5-2 5-2 5-5 •·6 5-11 5-15 5-15 5-15 5-16 5-16 5-17 5-17 5-17 5-18 5-18 5-18 5-18 5-18 5-19 5-19 5-19 5-19 5-19 5-20 7-1 7-1 7-1 7-1 7-1 7-1 7-1 8-1 8-1 8-1 8-1 - - Paragraph 8-5 8-6 Figure No. 1-1 2-1 2-2 3-1 4-1 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 6-1 6-2 6-3 6-4 6-5 7-1 7-2 7-3 7-4 8-1 8-2 Contents/Illustrations TABLE OF CONTENTS (Cont) SECTION 8- EA-801A DIFFERENCE DATA (Cont) INSTALLATION ILLUSTRATED PARTS LIST ..................................... . LIST OF ILLUSTRATIONS Title EA-401 A Encoding Altimeter ..................................... . Encoding Altimeter, Installation Diagram ............................. . Encoding Altimeter, Interconnection Diagram ........................... . Encoding Altimeter, Operating Control and Indicators ..................... . Encoding Altimeter, Functional Block Diagram ......................... . Special Test Fixture, Fabrication Diagram ............................. . Performance Tests, Interconnection Diagram ........................... . A2,Printed Wiring Assembly, Location of Jumper Tie Points For Temperature Compensation ............................................... . Altitude Compensation Cam ....................................... . Encoding Altimeter Cover Assembly, Rear View ......................... . Encoding Altimeter, Left-Side View ................................. . Encoding Altimeter, Top View .............................. : ...... . Encoding Altimeter, Right-Side View ................................. . Encoding Altimeter, Bottom View ................................... . Plate and Printed Wiring Assembly, Front View ......................... . Plate and Printed Wiring Assembly, Rear View ......................... . Encoding Altimeter, Top-Front View ................................. .Capsule and Servo Assembly, Rear View ............................. .Capsule and Servo Assembly, Front Oblique View ....................... . Counter and Dial Assembly, Rear View ............................... . Counter and Dial Assembly, Side-Oblique View ......................... . Encoding Altimeter, Schematic Diagram (2 Sheets) ....................... . Encoding Altimeter, Wiring Diagram ................................. . A 1, Printed Wiring Assembly, Wiring Diagram ........................... . A2, Printed Wiring Assembly, Wiring Diagram ........................... . A3, Printed Wiring Assembly, Wiring Diagram ........................... . Encoding Altimeter, Exploded View ................................. . Capsule and Servo Assembly, Exploded View ........................... . Counter and Dial Assembly, Exploded View ........................... . A 1, Printed Wiring Assembly, Parts Location Diagram ..................... . EA-801A Encoding Altimeter, Right-Side View ......................... . EA-801A Encoding Altimeter, Bottom View ........................... . Page 8-2 8-2 Page 1-1 2-2 2-3 3-1 4-5 5-3/5-4 5-7/5-8 5-9 5-10 5-16 5-21/5-22 5-21/5-22 5-21/5-22 5-21/5-22 5-23/5-24 5-23/5-24 5-23/5-24 5-23/5-24 5-23/5-24 5-23/5-24 5-23/5-24 6-3 6-7 6-9/6-10 6-11/6-12 6-13/6-14 7-3/7-4 7-7/7-8 7-13 7-20 8-5/8-6 8-6/8-6 iii Table 1-1 1-2 3-1 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 8-1 iv LIST OF TABLES Title Encoding Altimeter Specifications ................................... . Model Identification Chart for Encoding Altimeters ....................... . Encoding Altimeter Controls and Indicators ........................... . Required Test Equipment ......................................... . Preconditions To Alignment and Calibration Procedures ................... . Temperature Compensation Procedure, Data Sheet ....................... . Conditions For Performance Test Procedures ........................... . Input Voltage Adjustments, Warning Flag, and Voltage Variation Tests, Data Sheet .. Reference Voltage (E/2) Adjustment and Case Leak Test, Data Sheet ........... . Slew Speed and Static and Slew Speed Currents Measurements Test, Data Sheet ... . Dial Pointer Scale Error Test and Friction Error, Data Sheet ................. . Hysteresis and After Effect Test, Data Sheet ........................... . Digitizer Transistion Test, Data Sheet ............................... . Baroset Scale Error Test, Data Sheet ................................. . Position Error Test, Data Sheet ..................................... . EA-801 A Specifications ......................................... . Page 1-2 1-2 3-2 5-2 5-5 5-13 5-14 5-25/5-26 5-25/5-26 5-27/5-28 5-27/5-28 5-27/5-28 5-29/5-30 5-29/5-30 5-29/5-30 8-1 - - General Information SECTION 1 GENERAL INFORMATION 1-1. SCOPE. This manual contains general information, installation, oper- ation, trouble shooting, maintenance, and parts information for the EA-401 A Encoding Altimeter and difference data for the EA-801A Encoding Altimeter. 1-2. GENERAL'. The Encoding Altimeter (figure 1-1) is a panel mounted barometric altimeter with a built-in optical type altitude en- coder. Altitude is indicated by dial and digital readouts. The Encoding Altimeter provides aircraft altitude informa- tion to a pilot and to the aircraft transponder. Altitude pressure is sensed through an aneroid capsule and a pat- ented displacement detector. Visual displays, dial pointer and digital drum counter are driven from a servo system. The servo system is indirectly driven from the aneroid capsule through photocell amplifier which detects pressure induced movement of the capsule. Altitude range is from -1000 to 35,000 feet. 0392-10 Figure 1-1. EA-401A Encoding Altimeter Barometrically sensed altitude information is encoded, in digital form, by an optical encoder. These data, a ten bit word, are sent to the aircraft transponder for transmission to an ATCRBS (Air Traffic Control Radar Beacon System) ground beacon during Mode C (altitude) reporting to that facility. The encoding function produces a ten bit word in the ICAO (International Civil Aviation Organization) code corresponding to the altitude being sensed. The en- coder, a solid state optical type, is directly connected to the Encoding Altimeter's servo gear train. Altitude indications are displayed through a single dial pointer and a supplementary digital readout. The dial has ten major divisions of one hundred feet per major division. Major divisions are further subdivided into five equally spaced increments of twenty feet each. Every revolution of the dial pointer is equal to one thousand feet of altitude. The digital readout indicates in both thousands and in hun- dreds of feet. A striped warning flag appears during a "power off" condition to block the digital readout from view. The BAROSET knob, a front panel control, compensates for ambient atmospheric pressure. Adjustable range is from 28.1 to 31 in. Hg (946 to 1049 millibars). A four digit display, at the bottom of the dial, indicates adjusted setting. Encoded altitude data are not affected by BAROSET adjust- ments since encoded altitude is always referenced to stand- ard pressure of 29.92 in. Hg. Electrical connections to the Encoding Altimeter~ are made through a single connector on the rear of the unit. A static pressure line, from the aircraft pilot system, is connected to the rear of the Encoding Altimeter. Through this connection, exterior atmospheric pressure only is appliecko the aneriod diaphragm assembly. 1-3. REFERENCE DATA. Specifications for the Encoding Altimeter are listed in table 1-1. 1-1 TABLE 1-1. ENCODING ALTIMETER SPECIFICATIONS Parameter Input Voltage Range (Display and Encoding) Barometric Scale Range Lag Encoded Output Certification Dimensions Weight 1-4. EQUIPMENT SUPPLIED. The encoding Altimeter is supplied for either 14 Vdc or 28 Vdc operation and with a baroset readout either in inches of mercury (in. Hg.) or in millibars. Part numbers assigned to identify each of the instruments and their differences are listed in table 1-2. The Encoding Alti- meter is available with either illuminated or non-illum- inated front panels. 1-5. EQUIPMENT REQUIRED BUT NOT SUPPLIED. Electrical interconnections between Encoding Altimeter, ATCRBS Transponder, and aircraft power and ground Specifications and/or Range 14 Vdc or 28 Vdc -1000 feet to 35,000 feet (@ 29.92 in.Hg) 28.10 in. Hg to 31 in. Hg or 946 millibars to 1049 millibars Instantaneous altitude tracking greater than 20,000 feet/minute Logic "0" Output: Open, typically +5V from trans- ponder. Logic "1" Output: +0.7V, 0.2 rna maximum TSO-C10b, TSO-C88 (MTG-IP) 3~" X 3~" X 8" long_ 2¥.! pounds are terminated in 19-pin plug connector P1, ARC PN 42816-0000 (not supplied), which mates with receptacle J1 on the rear of the Encoding Altimeter. The Encoding Altimeter must be connected to the aircraft static line. Connection is made at the rear of the Encoding Altimeter through a 1/8-27 NPT connector which is not supplied. 1-6. EQUIPMENT SIMILARITIES. There are basic similarities between EA-401 A and EA-801 A Encoding Altimeter comprising installation, operation, and maintenance. For specific details, refer to the Difference Data material located within the 800 Series section of this manual. TABLE 1-2. MODEL IDENTIFICATION CHART FOR ENCODING _ALTIMETERS Part No. 42540- Primary Power Baroset Readout Unlit Panel Lighted Panel Vdc 2114 and 5114 14 in. Hg 3114 and 6114 14 in. Hg 4114 and 7114 14 in. Hg 2214 and 5214 14 Millibars 3214 and 6214 14 Millibars 4214 and 7214 14 Millibars 2128 and 5128 28 in. Hg 3128 and 6128 28 in. Hg 4128 and 7128 28 in. Hg 2228 and 5228 28 Millibars 3228 and 6228 28 Millibars 4228 and 7228 28 Millibars 1-2 - Installation SECTION 2 INSTALLATION 2-1. POWER REQUIREMENTS. Primary power requirements are either 14 Vdc or 28 Vdc de- pending on model selected. Interconnection with aircraft primary power source is through the 5 Ampere circuit breaker at the 14 Vdc or 28 Vdc MAIN power bus. 2-2. INSPECTION AND ADJUSTMENT. Inspect Encoding Altimeter for obvious physical damage. Checkout dial face, electrical and static line connectors (figures 2-1 and 5-4}. and cover assembly. BAROSET knob should turn evenly without binding. As BAROSET knob is rotated, dial readout for barometric pressure should indicate change and altitude dial pointer should advance (CW or CCW) depending on direction of rotation of BAROSET knob. 2-3. PREINSTALLATION BENCH TEST. Prior to installation, bench test the Encoding Altimeter using this procedure. (See figures 2-1 and 5-3.) Step 1. Interconnect test cable (figure 5-3) between Encoding Altimeter and power supply only. Leave power supply 0 F F. Step 2. Connect and adjust rated primary power, as required, using substep a or b. a. For a 14 volt model, connect 14 Vdt from power source to connector pin J1-P. Adjust DC OUTPUT voltage to 13.75 ±0.5 Vdc. b. For a 28 volt model connect 28 Vdc from power source to connector pin J1-N. Adjust DC OUTPUT voltage to 27.5 ±0.5 Vdc. Step 3. Apply power to the Encoding Altimeter from power source. Striped warning flag should disappear from view. Step 4. Obtain accurate local barometric pressure. Using BAROSET knob, adjust dial readout for local barometric pressure. Dial pointer and digital drum counter readout should indicate local altitude. 2-4. INSTALLATION REQUIREMENTS. 2-5. Mechanical Installation. The Encoding Altimeter should be rear mounted on a vibra- tion isolated aircraft instrument panel within convenient reach and view of a pilot. Mechanical installation details and specific dimensions are shown on figure 2-1. The following procedure outlines the basic mechanical instal- lation. Step 1. Locate mounting position and scribe markings on instrument panel for cutout. Use dimensions given on figure 2-1. Step 2. Drill three 5/32-inch holes for mounting screws at positions indicated on figure 2-1. Step 3. Drill 1/4-inch (0.125 radius) hole, for shaped cutout, at lower left of panel cutout. Step 4. Cutout mounting hole (3.150 diameter) and finish rough edges. Step 5. Finish shaping cutout that was started in step 3. Step 6. Mount and secure Encoding Altimeter with 6-32 steel screws of a length that will not pene- trate more than 3/8 of an inch nor less than 1/4 of an inch into the instrument mounting hole. 2-6. Electrical Interconnections. Electrical interconnections between Encoding Altimeter and aircraft primary power, aircraft light dimmer circuit, and transponder are outlined in this procedure. Detailed point- to-point wiring and required wire guages are indicated on figure 2-2. Step 1. Implement all electrical interconnections to the Encoding Altimeter through 19-pin plug connector P1, PN 42816-0000 (not supplied). Step 2. Interconnect aircraft ground wire between air- craft primary power supply and connector pin P1-M. Step 3. Connect rated primary power from Encoding Altimeter side of aircraft MAIN 5 Ampere. cir- cuit breaker to connector P1 per substep a or bas required. 2-1 a. For a 14 volt model, connect 14 Vdc air- craft power to connector pin P1-P. b. For a 28 volt model, connect 28 Vdc air- craft power to connector pin P1-N. Step 4. For lighted panel models only, interconnect aircraft light dimmer circuit with connector pin P1-V. Step 5. Interconnect designated pins of connector P1 with appropriate pins of aircraft trans- ponder. Refer to applicable transponder manual for location of specific connections within that unit. .625 3.500 DIA. I 3.150 DIA. J~ ----12 DIA. (3 HOLES) -PANEL CUT-OUT- Notes: 2-7. Static Line Connection. Do not apply pressure to static con- nection port at rear of Encoding Altimeter. Application of pressure to this port will cause permanent damage to the aneroid diaphragm. Connect aircraft static line to static connection port at rear of Encoding Altimeter. A 1/8-27 NPT connector is required, but not supplied, for this fitting. (See figures 2-1 and 5-4.) .,. I I I _J I I I I I IOO_J_I~Uj -DETAIL- CONNECTOR, RECEPTACLE, ELECTRICAL, J I (P/N 42847-0000) (NOTE 2) 5rATIC LINE FITTING (P/N 43585·0000) {NOTE I) 0392·11 1. Static Line Fitting takes 1/8-27 NPT Connector PN 43585-0000 (not supplied). 2. Connector ReceptacleJ1 mates with Connector Plug P1, PN 42816.0000 (not supplied). 3. Allow 3 inches for plug removal. Figure 2-1. Encoding Altimeter, Installation Diagram 2-2 -- Notes: 1. Connectors Data : (a) J1: Connector Re~ptacle, Electrical, PN 42847-0000. (b) P1 : ConneC!Or Plug, PN 42816-0000 (not supplied) . "1 2 . For 28 volt model only: Connector pin P1-N is interconnected, as indicated, with 28 Vdc MAIN BUS. Connector pin P1-P is not connected. 3. For 14 volt model only: Connector pin P1-P is interconnected, as indicated, with 14 Vdc MAIN BUS. Connector pin P1-N is not connected. 4 . Dial Illumination : (a) For illuminated panel models on ly : Interconnect connector pin P1-V as indicated. (b) For non-illuminated panel models only: Conn ector pin P1-V is not connected. 5 . Interconnecting Wiring Information : (a) All wires are stranded copper. (b) All unmarked wires are No . 22 AWG with insulating jacket . (c) All wires marked with asterisk ( •l indicate No. 20 A WG. ENCODIN~ ALTl ME. TE.R MODII='\E.D 10 Dtc.-IT GRtl.'< CODE OUTPUT 8 04 HC4 t- cz D Cl 8 B4 C...B2 £BI JA-4 ICA '2. 1\;f A I DIGITIZER COMMON ~CFT GND +'28 VDC +14VDC RESOLVER[~~~~i~ TAP RS 1 STATOR Ll t-IE -----t STATOR COSiiJE ---+ OPTIONAL. DI~L ILLUM\NA.TION (D5'2. ~ DS3) STATIC LINE 'i='ITTIN~ PN 43585-0000 '---....---' Installation r--~ 11 ] (NOTE 1) I v (;. Ry I f!;t~ N ~RY / 6Lv TO ~TCRBS TRA.~SPONDER ~R Y/bR N RY I Y£L R'/ /R£P .;HT/ fJC.~ JTO A.CFT t----- *------ POWER SOURCE GND J --*-5 -~-p--J +28VDC (NOTE '2.) +14\IDC (NOTE 3) AREA <)\-\OW~ I k1 RED IS FOR E.A - 801 ONLY TO ACFT INSTRUMEI-JT JTO A.C!='T LICt14T DIMME.R CIRCUIT (NOTE. 4) 1/g- '2.7 NPT E~TERNAL CONNECTOR (NOT SUPPLtE.D) Figure 2-2. Encoding Altimeter, Interconnection Diagram 0392-.12 2-3 ENCODIN~ P..L Tl M E.\E.R MOOII='\E.D 10 DIC..IT GR~'< CODE OUTPUT D4 C4 cz Cl B4 B2 Bl A.4 A.'2. AI DIGITIZER COMMOI'-1 A.CFT GND +'26 VDC t 14VDC RESOLVER[~1~~~~ TAP RSI STATOR Lit-lE--- -t STAiOR C051~E -- --1 OPTIONAL. Dlt>..L I LLUtv\ INA. T ION (D52 ~ DS3) STATIC LINE 'i="ITTINC:J PN 43565-00 00 L...___--.--__1 J IJ (NOTE 1) PI TO A.TCRBS TRA.~SPONDER JTO A.CFT t-- -- -* - -- - -- POWER SOURCE GND J __ *_s_;_p __ l+28 VDC (NOTE '2.) j +14\IDC (NOTE 3) AREA )\-\OW"-li~RED IS FOR EA-801 ONLY TO ACFT 11-lSTRUME:\JT JTO A.CI="T LIGHT DIMMER CIRCUIT (NO IE. 4) 1/g - '2-7 NPT E~TERNA.L CONNECTOR (NOT SUPPLIE-D) 0392 -12 2-4 Notes: 1. Connect o rs Data: (a) J1 : Co nn ector Receptacle , Elec trical , PN 42847-0000 . (b) P1: Connector Plug, PN 42816-0000 (not suppl ied ) . 2. For 28 vo lt model only : Con nect or pin P1-N is inte r co nn ect ed, as indicated , w it h 28 Vdc MA IN BUS . Connecto r p in P1-P is not conne cted . 3. For 14 vo lt model only: C onn ect o r pin P1-P is i nt ercon nected , as ind ic at ed , w i th 14 Vdc M A IN BUS. Co nnect or pin P1 -N is not c on nec ted . 4. Dial I llum in ation : (a) For illum inated panel models o nly: Interco nnect connector pin P1-V as ind ic a ted. (b) For n on -illuminated panel mo de ls only: Connect or pi n P1-V is not co nn ect ed. 5. Inte rco nn ecti ng Wi'r ing In for m at io n: (a) All w ir es are stranded cop per . (b ) A ll unmarke d w ires are No. 22 AWG with in sul at ing j acket . (c) A ll wi r es mar k ed with asterisk ( +) indicat e N o. 20 A W G. Figure 2-2. Encoding A ltimeter, Interconnection Diagram - - Operation SECTION 3 OPERATION ~-1. FUNCTIONAL OPERATION. The Encoding Altimeter provides the dual functions of visual altitude indications within an aircraft and encoding altitude data for further transmission to an ATCRBS ground beacon through an aircraft transponder. 3-2. Operating Limitations. The Encoding Altimeter provides continuous altitude infor- mation, both visual and encoded data, over a range from -1000 to 35,000 feet. Below -1000 feet and above 35,000 feet, internal control circuits stop the Encoding Altimeter's servomotor preventing lower or higher altitude indications. When this occurs, altimeter power remains on and the striped warning flag does not show. When the striped warning flag appears across the altitude digital drum counter, a primary power loss to the Encoding Altimeter is indicated. All Encoding Altimeter functions cease until power is restored. When visible, the striped warning flag indicates a power off condition but not necessarily a malfunction. When not visible. the strioed ALTITUDE READOUT WARNING FLAG BAROSET KNOB----- warning flag indicates that some power is applied to the unit. It does not indicate a trouble-free Encoding Altimeter. 3-3. OPERATING CONTROLS AND INDICATORS. Operating controls and indicators for the Encoding Altim· eter are described in table 3-1. Encoding Altimeter operation is limited to power ON/OFF and adjustment of BAROSET knob. A basic operating pro· cedure follows. (See figure 3-1.) Step 1. To operate Encoding Altimeter, place the Air· craft Master Power Switch to ON. Striped warning flag should disappear from view. Step 2. Prior to take-off, adjust BAROSET knob for local barometric pressure. Adjusted setting appears in barometric pressure window at bottom of dial face. The Encoding Altim· eter's dial pointer now indicates local altitude. Step 3. For lighted panels only, dial lig~t intensity. is controlled through adjustment of aircraft LIGHT DIMMER switch. -------ALTITUDE DIAL POINTER BAROMETRIC PRESSURE WINDOW 0392·13 Figure 3-1. Encoding Altimeter, Operating Controls and Indicators 3-1 TABLE 3-1. ENCODING ALTIMETER CONTROLS AND INDICATORS. Control/Indicator Function Encoding Altimeter ON/OFF Switching ON/OFF switch is the aircraft Master Power Switch which connects primary power (14 Vdc or 28 Vdc) to the Encoding Altimeter. Warning Flag Indicates a power OFF condition only. BAROSET Knob Allows setting of local barometric pressure. Ad- justable range is from 28.1 to 30.99 in. Hg (946 to 1049 millibars). When adjusted, an alti- tude offset is applied to the dial pointer. Encoded altitude data is not affected since this data is always referenced to standard barometric pressure of 29.92 in. Hg (1013:2 millibars). Barometric Pressure Window Displays adjusted barometric pressure. Altitude Dial Pointer Indicates altitude. One complete revolution Is equal to 1000 feet of altitude Ten major divisions Each division is 100 feet of altitude Five subdivisions Each subdivision is 20 feet of altitude Altitude Readout (Drum Counters) Displays altitude in hundreds and thousands of feet. Registers 100 feet for every major subdivision traversed by dial pointer. Registers 1000 feet for each revolution of dial pointer. - 3-2 - - Trouble Shooting SECTION 4 TROUBLE SHOOTING 4-1. SCOPE. This section contains trouble shooting information and a block diagram analysis of the Encoding Altimeter. 4-2. TROUBLE SHOOTING. If major trouble develops in the Encoding Altimeter, re- move the assembly from the aircraft and do a complete set of performance tests (located in Section 5) on the unit. Test results will help to localize the subassembly in which a malfunction exists. When suspected faulty unit has been located, trouble may be cleared by performing one of the alignment or calibra- tion procedures located in Section 5. If the trouble cannot be cleared through any of the foregoing procedures, return the Encoding Altimeter or the known faulty subassembly to the manufacturer for repair. Prior to removing the instrument from the aircraft, the following procedures should be performed as preliminary steps to further trouble shooting. 4-3. Local Altitude Check. I WARNING I When checking the Encoding Altim- eter, an accurate barometer must be used as a reference. Setting the En- coding Altimeter against a incorrect reference may only confirm an exist-. ing error that will not be apparent. An unknown error could cause dan- gerous situations to develop during actual use of the Encoding Altimeter. Step 1. Using the BAROSET knob, set Encoding Altim- eter's barometric readout to identical readout of an accurate barometer. Step 2. Indicated altitude on Encoding Altimeter should equal local altitude plus height of the aircraft. If indicated altitude is in error by more than ±75 feet, do not use Encoding Altimeter for IFR flight. 4-4. Primary Power Check. Verify normal application and value of primary power to Encoding Altimeter. Step 1. Be sure that aircraft master power switch is ON. Striped warning flag should disappear from view. If the flag remains in view, proceed to Step 2. Step 2. Check primary power applied to Encoding Altimeter using substeps a or bas required. a. For a 14 volt model: 13.75 ±0.5 Vdc. b. For a 28 volt model: 27.5 ±0.5 Vdc. Step 3. Check for presence of primary power at con- nector plug P1. a. For a 14 volt model, check connector pin P1-P. b. For a 28 volt model, check connector pin P1-N. Step 4. If striped warning flag remains in view, remove unit from aircraft and check primary power within Encoding Altimeter. Check power at warning flag solenoid L1. (See figure 6-1.) 4-5. Encoding Altimeter Checkout. If the results of. paragraphs 4-3 and/or 4-4 are negative, re- move the unit from the aircraft and proceed to performance testing. Results of these tests should indicate the subassem- bly responsible for the trouble. If trouble is an electronic component on any of the three printed wiring boards (A 1, A2, or A3), replace the faulty component and retest the unit using performance test pro- cedures. If the failure was on the A2 board in the Capsule and Servo subassembly, perform the temperature calibration procedure in addition to performance tests. The temperature calibration procedure is required to check validity of tem- perature compensation with a new component in the A2 board. If mechanical trouble is suspected in the Capsule and Servo 4-1 subassembly, do not disassemble that unit. Return the sub- assembly to the manufacturer for repair. 4·6. FUNCTIONAL DESCRIPTION. A functional description of the Encoding Altimeter is pro- vided in the following paragraphs. This discussion is based on the Functional Block Diagram, figure 4-1. 4-7. Generation of Error Signal. Aircraft altitude is sensed through the aneroid diaphragm assembly which expands or contracts in response to higher or lower altitude levels. A slotted vane, mounted on the diaphragm, is moved either up (diaphragm expansion) or down (diaphragm contraction). Light intensity from lamp DS1 is directed through the slot in the vane and brought to focus on dual photocell V1. Under static conditions, zero altitude change, light intensity from lamp DS1 is distributed equally over both elements of dual photocell V1. For the static condition then, there is zero error sig- nal. When a change of altitude occurs, diaphragm expansion or contraction drives the vane forward or backward between lamp DS1 and dual photocell V1. The resulting unbalanced light intensity on dual photocell V1 causes an output vol- tage, or error signal, to develop. After amplification in A1AR1A, the error signal appears at the inverting input of summing amplifier A1AR1B as the variable input. The amplified error signal will then appear as the driving vol- tage for servomotor B 1 after further amplification in driver amplifiers A 1AR2 and A 1AR3. Direction of rotation of B1 depends on whether the greater amplitude voltage is from amplifier A 1AR2 or A 1AR3. The relative polarity of the originating error signal determines its magnitude at the output of either A 1AR2 or A 1AR3. 4-8. Error Signal Null. A servoloop from servomotor B1 to diaphragm vane assem- bly tends to drive error signal voltage to a null. or zero level. The servo loop includes servomotor B 1, gear train assembly, coupling shafts, diaphragm vane assembly, and altitude compensator vane assembly. Whenever servomotor B1 is driven, coupling shafts engage the mounting shaft of the aneroid diaphragm assembly and raise or lower the entire unit. The vane, mounted on the assembly, will be driven toward a position so as to equalize light intensity, through the slotted vane, over dual photocell V1. When the condition of equal light intensity on V1 is obtained, the error signal is again equal to zero and servomotor B 1 stops. 4-2 4-9. Altitude Compensation. To account for non-linear elements, altitude compensation is required. A compensator vane, having the same operating motion as the vane attached to the aneroid capsule, is driven by a cam and lever arrangement from the servomotor. The altitude compensation cam (figure 5-1 and 5-6) func- tions to offset the light from lamp DS1 in a direction which will linearize altitude readout. The cam is adjustable and is calibrated to known altitude settings over the entire range of the instrument. 4-1 0. Tachometer-Generator G1. During the terminal phase of a null seeking condition, error voltage is reduced in level and may cause overshoot with attendant hunting for .the null position. This would be demonstrated by an oscillation in the instrument's dial pointer. To provide for smoother operation, another vol- tage takes control of servomotor B1 operation during the terminal phase of the null seeking condition. This terminal phase controlling voltage is derived from tachometer-gener- ator G 1. Tachometer-generator G 1, driven from servomotor B 1, provides a swamping voltage to override the error signal voltage. Since the tachometer is sensing the rate of change of rotation of B 1, tachometer voltage can more accurately control the slew rate toward zero error position. 4-11. Temperature Compensation. Thermistor bridge and amplifier A2U1 provide temperature ·compensation for any temperature induced error voltage. Thermistor A2RT1 changes resistance inversely as tem- perature changes. The resulting bridge circuit unbalance causes a change in output voltage across both inputs to bridge amplifier A2U 1. Bridge amplifier A2U 1 outputs a reference voltage that is temperature compensated to the non inverting input of summing amplifier A 1AR 1 B. Whenever temperature induced movement of aneroid diaphragm assembly is incurrred, the resulting error voltage will be offset at the inverting input to summing amplifier A 1AR 1B by an equal and opposite temperature compen- sated voltage at the non inverting input to this same amp- lifier. The net result is to provide a zero output from the summing amplifier under any temperature induced circuit change. 4-12. Altitude Display. Servomotor B1 drives a dial pointer through gear train and differential assemblies. A mechanical counter with digital readout is activated by the dial pointer to indicate altitude in hundreds andthen throusands of feet. 4-13. BAROSET Adjustment. The BAROSET adjustment, through differential gearing, allows limited adjustment of the dial pointer without any interaction with servomotor B1. This feature permits ad- justment of the dial indicator to actual barometric pressure and local elevation. An additional linkage from the . BAROSET knob connects to another mechanical counter which presents a digital display of barometric pressure in either inches of mercury or in millibars. This display is located at the bottom of the dial face. The BAROSET adjustment does not interact with the encoding function. Encoded altitude data are not affected by the BAROSET adjustments since encoded altitude is always referenced to standard pressure of 29.92 inches of mercury (in. Hg). Trouble Shooting 4-14. Encoder Transducer MT1. The encoder transducer interprets mechanically coded altitude data as electrical levels. These levels are coded, in suitable logic circuits, into a ten-digit modified Gray code. Coded data are sent out on ten separate lines to the aircraft transponder for transmission to an ATCRBS ground beacon. At the ground beacon, the data are de- coded and interpreted as the aircraft's altitude. Altitude data are transmitted by request only and are not in con- tinuous transmission. The transponder must be switched to MODE C (altitude reporting) before the encoder logic will output a ten-digit code to the transponder. When the transponder is in any other mode, the encoder logic, in the Encoding Altimeter in inhibited from outputi,ng a code. 4-3/4-4 Maintenance SECTION 5 MAINTENANCE 5-1. SCOPE. This section contains calibration, tests, removal, and dis· assembly procedures for the Encoding Altimeter. The pro· cedures are intended for field depot maintenance and pro- vide adequate coverage for the extent of repair or testing at this level. Disassembly or repair of items not covered under these procedures should not be attempted in the field. 5-2. PREVENTIVE MAINTENANCE. The Encoding Altimeter should be checked for normal oper- ation using preliminary procedures given in Section 4 (pri- mary power check and local altitude check). These proce- dures can be performed with the instrument mounted in the aircraft. The input voltage can be checked at the main power bus of the aircraft (see figure 2·2). Since preventive maintenance schedules are not necessary, the referenced procedures need only be applied as preliminary measures for a suspected malfunction. 5-3. Transponder. If trouble develops with encoded altitude information, isolate the malfunction to the faulty unit - either Encoding Altimeter or the aircraft Transponder because these two units are interconnected and it is necessary to first deter· mine where encoded altitude data are malfunctioning. 5-4. CORRECTIVE MAINTENANCE. The Encoding Altimeter consists of three main subassemblies: Plate and Printed Wiring Board (figures 5-10 and 5-11 ); Cap- sule and Servo (figures 5-13 and 5-14); and Counter and Dial (figures 5-15 and 5-16). If minor adjustments or alignments to one of these items are indicated, corrective action may be undertaken to the extent prescribed by procedures given in this section. Certain minor mechanical and electrical re· pairs can be made to the Dial and Counter and Plate and Printed Wiring subassemblies without special test equip- ment and test fixtures. Under no circumstances is further dis- assembly of the Capsule and Servo sub- assembly to be attempted at field depot level. If repair to this item is required, disassemble the Capsule and Servo sub· assembly from the top assembly and return it to the manufacturer for repair or replacement. 5-5. SPECIAL TEST EQUIPMENT. 5-6. Test Jog (Special Test Fixture). For certain procedures, a Special Test Fixture (figure 5-1) is required. The Encoding Altimeter with its cover assembly removed can be inserted into this Special Test Fixture and operated under changing altitude conditions. A plastic win- dow with a tool insert (Bristol splined wrench) provides access to the set screws of the altitude compensation cam (13, figure 5·7). Under various test altitudes and under nor· mal operating conditions, adjustments can be made to the altitude compensation cam while the Encoding Altimeter is inside the Special Test Fixture. The fabrication diagram (figure 5-1) provides instructions for fabricating a test fixture having three containers which would allow for simultaneous testing of three Encoding Altimeters. 5-7. Temperature Controller. A Temperature Controller is required for temperature con- trolled testing. This device must have sealed access holes to accommodate test cables (electrical and air lines). The device must be able to sustain test temperatures over a three hour period (thermostatically controlled). Internal temperature variation between -30° to +55°C is a requirement. 5-1 5-8. TEST EQUIPMENT AND TOOLS. Test equipments required are itemized in table 5·1. The spe· cial Test Fixture is required for altitude accuracy calibration. A Temperature Controller is required for temperature con· trolled testing. Required tools include assorted screwdrivers and Bristol (splinedl wrenches with four and six splines for loosening and tightening setscrews. Additionally. a set of small box wrenches is required for removing threaded mounting rods. 5-9. CLEAN ROOM. All maintenance procedures are to be performed within the confine of a clean room. This precaution also applies to dis· assembly procedures when internal components are exposed. The Encoding Altimeter must always be completely assembled when it is in any other environment. 5-10. ALIGNMENT, CALIBRATION, AND COMPENSATION. The following procedures are to be performed whenever sub· assembly or major part replacements have been required. TABLE 5-1. REQUIRED TEST EQUIPMENT Item Source/Model AltimeterNSI Test Set Mensor Corp. Model 10620-001 0 to 32 in. Hg (Absolute) Digitizer Test Set Instrument Technology Corp. Model 90,000·115 Power Supply Power Designs Inc. Model 6060A, 14 and 28 Vdc@ 1 Ampere capac· ity. Front panel meter monitors out· put voltage and current. Pressure Source 10 PSI, dry, high purity nitrogen (N 2 l or filtered and dried com· pressed air. Pump-Vacuum Sargent-Welsch Co., Model 1405 Test Cable Fabricate locally (Figure 5-2) Test Jig (Special Test Fixtures) Fabricate locally (Figure 5·1 and refer to paragraph 5·6). Temperature Controlled Test Chamber Requires access holes for test cable (electrical) and air line from Altimeter/ VSI Test Set. Range of control is -30°C to +55°C. Stopwatch Required range of ONE minute Digital Multimeter Fluke Corp. Model 8000A 5-2 - Maintenance TABLE 5-2. PRECONDITIONS TO ALIGNMENT AND CALIBRATION PROCEDURES Condition Position Pressure· Ambient Primary Power 14 volt model: Voltage: Current: 28 volt model: Voltage: Current: Temperature-Ambient Warmup Clean Room Preconditions applicable to all of the procedures are specified in table 5·2. The procedures must be performed within the confines of a clean room. 5-11. Encoder Alignment. This procedure is to be performed whenever repair or re· placement of the Dial and Counter. Capsule and Servo sub· assemblies, or any function concerned with the encoding function has been repaired or aligned. After reassembling the Encoding Altimeter. perform this procedure prior to performing the altitude accuracy calibration procedure. This procedure is performed with the cover assembly re· moved. NOTE This procedure is performed with the cover assembly removed. Step 1. Loosen locking screw (3. figure 5·12) for sector· Requirement Unless otherwise specified. the instrument shall be calibrated, aligned. or compensated while in its normal operating position. 29.92 in Hg 13.75 ±0.5 Vdc 600 milliamperes de (maximum) 27.50 ±0.5 Vdc 350 milliamperes de (maximum) 71° ± 10°F Prior to beginning any procedure, the instrument shall have had power applied for five minutes. All of these procedures are to be performed within the confines of a clean room. gear lever (6, figure 5-15). Slide sector-gear lever to side to disengage servomotor gears from Dial and Counter subassembly. Step 2. Turn altitude counter bevel-gear (10. figure 5·16) by hand until counter displays all zeros and dial pointer is at zero. The dial pointer and altitude drum counter should move freely with no evidence of binding or sticking. Step 3. Be sure that BAROSET knob moves freely and that BAROMETRIC display indicates pressure (in. Hg or millibars) throughout the range of 28.1 to 30.99 in. Hg (946 to 1049 millibars). Note that upper and lower baroset knob stops (8, figure 5·161 are set so that BAROMETRIC display indicates slightly above and below speci· tied range. Step 4. Set BAROSET knob for an indication of 29.92 in. Hg (1013.2 millibars). Leave BAROSET dis- play in this position throughout this procedure. Step 5. Loosen set screws on encoder disc drive gear ( 1. figure 5·91. Step 6. Connect test cable (figure 5-21 between Encoding Altimeter. power supply. and digitizer. Apply 5-5 primary power per table 5-2 and perform checks as follows: a. Check that current supplied agrees with specified current of table 5-2. b. Check warning flag operation as power is switched ON and OFF. There should be no binding or hang up of warning flag. As power is switched OFF there will be a slight delay as flag drops into view. After power has been applied to the Encoding Altimeter, the servomotor should run and then stop at a null positi·Jn. If servomotor does not stop, switch power OFF. If servomotor is allowed to run continuously without nulling out, severe or permanent dam· age to the Capsule and Servo sub· assembly will occur. Step 7. Switch primary power ON. l.J!t servomotor seek a null position. Aneroid capsule (5, figure 5-9) should be in approximate mid· range position. Step 8. Manually, move altitude compensator vane (7, figure 5-7) toward rear of Encoding Altimeter and hold in this position. The servomotor should start and then stop. Step 9. Release altitude compensator vane. Servomotor should reverse direction and then stop. Step 10. Manually, turn encoder disk (2, figure 5·9) until readout on digital altitude decoder indicates all zeros. Continue turning encoder disk until read· out indicates +100 feet. Step 11. Manually, rotate altitude counter bevel-gear ( 10, figure 5-16) until dial pointer indicates +50 feet. Step 12. Lightly, retighten encoder disk drive-gear set screws. Step 13. Turn altitude counter miter-gear until dial pointer indicates -50 feet. The readout on the altitude decoder (Digitizer) should indicate -100 feet. If this requirement is not met, repeat steps 10 through 13 and split error difference. EXAMPLE: Dial pointer on plug side of 0 indicates +50 feet and on minus side of 0 the dial pointer indicates -30 feet. Total error is 80 feet (1+50/+/-30). Divide total error (in this case 80 feet) by 2 and get 40 feet. Reset dial pointer to indicate +40 feet when digitizer indicates +100 feet. Dial pointer on minus side of 0 should indicate -40 feet when digitizer indicates -100 feet. The error is now evenly divided. Step 14. Slide sector gear lever (6, figure 5-15) back into position to engage sector gear with servomotor drive train. Retighten sector gear lever locking screw (3, figure 5-12). Do not turn any gears at this point. Step 15. Tighten encoder disk drive gear set screws ( 1, figure 5-9). Be sure not to let encoder disk (2, figure 5-9) rotate independently while tight· ening set screws. Step 16. Insert Encoding Altimeter into Special Test Fix· ture and connect test equipment per figure 5-2. Step 17. Adjust Mensor for an atmospheric pressure of -1000 feet. Continue to change pressure below -1000 feet until Encoding Altimeter's dial pointer stops, indicating that servomotor lower altitude limit switch 51 (9, figure 5-7) has opened. This should occur at or below -1,100 feet. If this condition is not met, perform alti- tude accuracy calibration procedure and set the operating point at which lower altitude limit switch S1 functions. Step 18. Adjust Mensor for an atmospheric pressure of +35,000 feet. Continue to change pressure above +35,000 feet until Encoding Altimeter's dial pointer stops, indicating that servomotor upper altitude limit switch 52 (1, figure 5-7) has opened. This should occur above 35,250 feet. If this condition is not met, perform altitude accuracy calibration procedure and set the oper- ating point at which upper altitude limit switch 52 functions. Step 19. Proceed with performance tests for the Enocding Altimeter to determine accuracy and validity of this procedure. 5-12. Altitude Accuracy Calibration. This procedure is to be performed whenever repair or replace· ment of components or subassemblies, affecting altitude cal- ibration, has been accomplished. This procedure is performed with cover assembly removed and requires the use of the Special Test Fixture, previously described in this section. (See figure 5-1J Step 1. Adjust power supply OUTPUT DC voltage to the rated value for the Encoding Altimeter under test. Rated voltages are specified in table 5·2. Switch power supply OFF. - NotM: 1. Fabricate Tnt Cable locally using Connector Plug P1 and llranded copper wire as follows: (a) Use No. 20 AWG lor connector pins P1·M !GNO) and P1-P or P1-N whichever is used lor Primary Power. (b) Use No. 22 AWG lor all other wires. 2. For Connector Plug P1 usestral{lht connector plug PN 42816-0000 (not supplied). /. EI-JCODHJ~ ALTIMETER [+14 VDC- p PRIMARY +'l8 voc- 1-J POWER GND- M / 04- A C4- C'l- C ~ODIFIE.D 10 DIGIT GRAV CODE OUTPUT Cl- B4 - B'l- e>t- D E F G A4- H A?. - J AI- K DIGITIZER _ l CO~MO~ OPTIONAL [t 14 VDC DIAL OR - ILLUMI~ATIO~ +'l8 VDC v Jl PI ().JOTE 2) rTEST CABLE (~OTE I) J Maintenance POWER SUPPL"' POWER DESIGijS I~C MODE.L 60GOA +]OUTPUT JACKS DIGITI'Z.ER TEST SET r--------------------------4--~------------------------~ I~STRUMENT TECHNOLO~YCORP MODEL 90000·115 ALTIMETER/VSI TEST SET TWO STAGE VACUUM PUMP SARGEI-.&T-WELSCH CO. MODEL 1405 STATIC LINE fiTTI~G Pt-1 4358~·0000 tD fAIR LINE \__1/8- 27 ~PT MENSOR CORP MODEL 10620-0001 (0 TO 3'2 1~. H<l) 1 EXTERt-.IAL CO"-l~E.CTOR (NOT SUPPL I E.D) PRESSURE SOURCE. 10 PSI DRY , HIGH PURITY I\IITROGE.t-.1 (t-.12) OR FILTE.RE.D At.JD DRIED COMPRESSED AIR Figure 5-2. Performance Tests, Interconnection Diagram 0392·30 5-715-8 - Step 2. Interconnect test cable (figure 5·2) between En· coding Altimeter and power supply. Step 3. On worm gear (4, figure 5·81, loosen two set· screws, disengage worm gear, and slide it out of the way toward the end of its shaft. Step 4. Switch power supply ON. Allow Encoding Alti· meter to warm up for five minutes before con· tinuing with this procedure. Step 5. Adjust BAROSET knob for an indication of 29.92 in. Hg (1013.2 millibars) on barometric readout. This setting will not be changed throughout this procedure. Step 6. On Encoding Altimeter's A2 Board (7, figure 5·8), connect voltmeter(+) lead to pin 10 (see figure 5·3 for pin location) and voltmeter(-) lead to GND. Step 7. Adjust potentiometer A1R6 REFERENCE VOL· TAGE (E/21 ADJUSTMENT (4, figure 5· 11 l for required voltmeter indication as follows: a. For a 14 volt model: 6.75 Vdc b. For a 28 volt model: 13.75 Vdc Step 8. Switch power supply OFF. Step 9. On altitude compensation cam (13, figure 5·7). adust all seven cam set screws (14, figure 5·7) to their nominal position using a Bristol (splined) U1 0 15 • Notes: Maintenance wrench. Manually rotate altitude compensation cam. Altitude compensator vane (7. figure 5-7) should remain nearly motionless as cam is ro· tated throughout its entire range. If altitude compensator vane moves at any point of cam rotation, readjust cam set screw so that inter· acting compensating pin (15, figure 5·71 does not touch contact lever ( 10. figure 5·7). When completed, the altitude compensator vane lever should remain parallel to the rear servo plate (5, figure 5· 7) as the cam is rotated throughout its entire range. Step 10. Disconnect test cable from Encoding Altimeter. Insert Encoding Altimeter into Special Test Fixture and connect test equipment per figure 5·2. Turn ON all test equipment. Step 11. Adjust Mensor for sea level atmospheric pres· sure (29.92 in Hg) and wait until dial pointer stops (servo has nulled out). Step 12. Switch power supply OFF and remove Encoding Altimeter from Special Test Fixture. Step 13. Loosen sector gear lever locking screw (3. figure 5·12). Slide sector gear lever (6. figure 5-15) aside to disengage gear train. Step 14. Manually. rotate altitude counter bevel gear (10, figure 5·16) until a zero indication is ob· tained on altitude readout and dial pointer. OS9Z -ze 1. For POSITIVE compensation. strap pins 10 to 11 and strap pins 12 to 13. 2. For NEGATIVE compensation, strap pins 10 to 12 and strap pons 11 to 13. Figure 5·3. A2 Printed Wiring Assembly, Location of Jumper Tie Points For Temperature Compensation 5-9 Step 15. Reengage gear train by sliding sector gear lever back to its original position. Tighten sector gear lever locking screw (3, figure 5·121 after adjusting for slight backlash when gears have meshed. Step 16. Return Encoding Altimeter to Special Test Fixture and switch power supply ON. Step 17. Adjust Mensor for an atmospheric pressure of 18,000 feet. let pressure stabilize and let dial pointer stop (indicating servo has nulled out). Check for excessive leaks from Special Test Fixture before proceeding. Step 18. Adjust Mensor for an atmospheric pressure of 35,500 feet. let pressure stabilize and check altitude indication on Encoding Altimeter and digitizer. Step 19. Switch power supply OFF. Reduce pressure with· in Special Test Fixture to local altitude andre· move Encoding Altimeter from Special Test Fix· ture. Step 20. Manually. rotate altitude compensation cam ( 13, figure 5-71 to its maximum CCW position. When fully rotated, a protruding lever. attached to the lower cam shaft, will engage the ON/OFF button of upper altitude limit switch S2 (1, figure 5-71. The ON/OFF button must be fully depressed and held in this position while performing the next 1ST SET SCREW ADuUSl MENT 24000 1 TORSION WIRE SPRING----' <NOTE ? > Notes: step. Check cam springs for proper alignment. (See figure 5-4.1 Step 21. Return worm gear (4, figure 5·81 to its normal position (mated with the cam's shaft gear). When properly mated, tighten worm gear setscrews. Be sure that ON/OFF button on switch S2 has been fully depressed by cam lever throughout the performance of this step. Step 22. Return Encoding Altimeter to Special Test Fix· ture. Switch power supply ON. NOTE Throughout the following adjustments. adjust barometric pressure from Mensor so that each succeeding altitude compen· sation cam set screw (figure 5·4 and 14, figure 5-71 is aligned under the Bristol (splined) wrench in the plastic window in Special Test Fixture. Pressure and altitude standards from the Mensor will be used as reference. Step 23. Adjust Mensor for an atmospheric pressure of 35,000 feet. Continue to adjust Mensor until seventh set screw (figure 5-41 is under Bristol (splined) wrench in plastic window of Special Test Fixture. HELICAL TORSION SPRING (NQlE I) 7TH .SET SCREW -1000 1 >APPROXIMATE ALTIUDES .... ~--4000" SOCKET HfAO CAM AO.JUSTIIAEWT SCREWS 12000 1 ----18000' OJIZ-21 1. Ensure that helical tension spring is centered bet-nand does not touch -1000 and 35.000 foot adjustment pins. 2. Ensure that torsion wire spring is centered in grooves of adjustment pins. Figure 5-4. Altitude Compensation Cam 5-10 - - - Step 24. Adjust cam set screw with Bristol (splinedl wrench until altitude indication on Encoding Altimeter is identical with altitude indication on Mensor or there is minimum difference between these two indication. Step 25. Adjust Mensor so that sixth cam set screw is aligned under Bristol (splined) wrench in plastic window of Special Test Fixture. Adjust cam set screw so that altitude indications are identical on Encoding Altimeter and Mensor or so that there is minimum difference between these two indications. Step 26. Repeat step 25 for remaining cam set screws until all have been adjusted. Step 27. Perform a dial pointer scale error test on the Encoding Altimeter. Use the procedure given in this section under performance tests. Use the data sheet associated with dial pointer scale error test (table 5·81. For each of the 20 test steps, enter the dial pointer altitude indi· cation on the data sheet. Check all written data against the specified tolerances on data sheet (column 5, table 5-81. If the specified requirements are met, the Encoding Altimeter is properly calibrated. If these requirements are not met, continue with this procedure. Step 28. From dial pointer scale error test data, deter· mine which test steps are out of tolerance. Re- adjust Mensor to test altitude (column 2, table 5-81 and reset corresponding altitude compensation cam set screw until dial pointer indicates an altitude that is within the tolerance specified (column 5, table 5-81. Repeat the procedure of this step for all out of tolerance test steps (column 1, table 5-81 until all data falls within the tolerances specified under column 5, table 5-8. Step 29. Adjust Mensor for local altitude and switch OFF power supply. Remove Encoding Altim· eter from Special Test Fixture and replace cover assembly. Step 30. Proceed with performance tests for Encoding Altimeter to determine accuracy and validity of this procedure. 5-13. Temperature Compensation Procedure. This procedure is to be performed whenever repair or re· placement to Encoding Altimeter's A2 printed wiring board is accomplished. If Capsule and Servo subassembly have been replaced, and replacement unit has jumper wires (figure 5-31 for temperature compensation in place, assem· ble Encoding Altimeter and perform this test as a validation Maintenance checkout without making any adjustments to the Encoding Altimeter. If all tolerances are met, the unit is acceptable. If test requirements are not met, perform this procedure making adjustments as stipulated in procedure. This test requires the use of the temperature controller. The Encoding Altimeter is completely assembled while undergoing temperature environmental testing. Step 1. On Encoding Altimeter's A2 printed wiring board (7, figure 5-81. do the following (cover assembly removed I: a. Rotate potentiometer A2R 1 (3, figure 5-91 to full CCW position. b. Strap pins of A2 board for positive compen- sation. (See figure 5-3.1 Step 2. With no load connected, adjust power supply OUTPUT DC voltage to rated voltage of En- coding Altimeter under test. Use specified vol· tages of substep a or b as required. Switch power supply OFF when voltage adjustment has been completed. a. For a 14 volt model: b. For a 28 volt model: 13.75 ±0.5 Vdc 27.5 ±0.5 Vdc Step 3. Using test cable (figure 5-21. interconnect En- coding Altimeter with power supply as shown in figure 5-2. Step 4. Switch power supply ON, check applied DC voltage and reset if necessary. Allow a 15 minute warmup period before proceeding further into this procedure. Step 5. Remove test cable and reassemble Encoding Altimeter. Place Encoding Altimeter into tem- perature controller. Step 6. Interconnect Encoding Altimeter with test equip- ment as shown in figure 5-2 (the digitizer is not required). Step 7. With ter.1perature controller at ambient temper- ature, do the following: a. Perform case leak test as described under performance tests in this section. b. Verify that pressure leakage from Encoding Altimeter does not exceed the 100 feet per minute altitude loss as specified in leak test. c. Verify that pressure leakage from air line between Mensor and Encoding Altimeter does not exceed the 100 feet per minute altitude loss. This may be done by observing Encoding Altimeter's dial pointer for loss of altitude. 5-11 d. Verify that all requirements of this step are met before continuing this procedure. Step 8. Adjust Mensor for an atmospheric pressure of +1000 feet. let pressure stabilize within En· coding Altimeter. Step 9. Verify Encoding Altimeter's dial pointer indi· cates exactly +1000 feet. If dial pointer does not so indicate, adjust BAROSET knob until dial pointer indicates +1000 feet. Record dial pointer indication at start of test step 1, column 4, table 5·3. Step 10. Adjust temperature controller for an internal temperature of -30°C and log the local time that this is done. This test will continue over a five hour period and data must be recorded at discrete time intervals. Take note of these specific time intervals, as listed in column 3 on data sheet (table 5·3), and be available to record test data during these periods. Step 11. After three hours. do the following: a. Record altitude indication of Encoding Altimeter in test step 2. column 4, table 5·3. b. Adjust temperature controller for an inter· nal temperature of +55°C and log the local time. c. From data sheet, table 5·3, determine the algebraic difference between reference altitude (column 2) and indicated altitude recorded in substep a of this procedure (indicated altitude in column 4- 1000 Feet). Record this difference in test step 2, column 10, table 5·3. d. Compare difference recorded in column 10 with specified tolerance of column 5 and determine whether data is in or out of tol· erance and by what amount. Record this figure in test step 2, column 11 or 12, table 5·3. Step 12. After three hours and fifteen minutes, repeat step 11 of this procedure for test step 3, table 5·3. Step 13. After three hours and 30 minutes, repeat step 11 of this procedure for test step 4, table 5·3. Step 14. After three hours and 45 minutes, repeat step 11 of this procedure for test step 5, table 5-3. Step 15. After five hours, repeat step 11 of this pro· cedure for test step 6, table 5·3. Step 16. Shutdown heating applied to temperature con· 5-12 troller. Remove Encoding Altimeter from test chamber and let stabilize for two hours before compensating. After two hours, remove cover assembly and reconnect test cable (figure 5-2}. Compensation will be performed under ambient temperature and pressure conditions. NOTE There are two categories of temperature error which permit compensation. Deter· mine applicable category by comparing test results (columns 11 and 12, table 5·3) and information in steps 17 and 18 of this procedure. Compensate the Encod· ing Altimeter accordingly. If however. an error is indicated in test steps 2 and 6, under column 12, table 5·3, and these errors are both in the same direction, the unit can not be compensated as is. Step 17. Compare adjusted data for -30° C and 55° C as recorded in columns 11 and 12, table 5·3 and proceed as follows: a. Adjusted data will indicate that at one of these temperatures the direction is positive and at the other temperature the direction is negative. b. Of these data, one will be within tolerance (column 11, table 5-3) and the other will be out of tolerance (column 12, table 5-3). c. Temperature compensate Encoding Altimeter by adjusting potentiometer A2R 1 (3, figure 5·9) until dial pointer is rotated by the same amount and direction as the error noted in column 12, table 5-3. Step 18. Compare adjusted data for -30°C and +55°C as recorded in columns 11 and 12, table 5-3 and proceed as follows: a. Adjusted data will indicate that at both of these temperatures, the direction of error is the same. b. Of these data, one will be within tolerance (column 11, table 5-3) and the other will be out of tolerance (column 12, table 5-3). c. If error is at +55°C and is greater than +50 feet, decrease indicated altitude by the dif- ference between the error and +50 feet. When decreasing altitude indication, the compensat· Maintenance TABLE 5-3. TEMPERATURE COMPENSATION PROCEDURE, DATA SHEET Temperature Compensation Test Data Adjusted Data TemperatureTest Run Compensation Data Test -30°C (Cold Soak) Transitional Period +55°C (Hot Soak) Difference In Within Test Altitude Time Indicated Tolerance Indicated , Tolerance Indicated Tolerance Altitudes Tolerance Error Step (Feet) Into Test Altitude (feet) Altitude (Feet) Altitude (Feet) (Indicated-Test) (Feet) (Feet) 8 0 0 0 0 0 0 0 0 G @ @ Start Test 1 ~ 1000 0.0 Hours 3.0 (Column 4-1000) 2 1000 Hours ±40 -1----- 3 Hrs (Column 6-1 000) 3 1000 +15 Min ±70 ' 1-- - 3 Hrs (Column 6-1000) 4 1000 +30 Min ±70 - ---------··--- ~------ I- 3 Hrs (Column 6-1000) 5 1000 +45 Min ±70 f---- 5 Hrs I (Column 8-1000) 6 1000 End of Test ' ±50 5-13 TABLE 54. CONDITIONS FOR PERFORMANCE TEST PROCEDURES Condition Requirement Position Unless otherwise specified, the Encoding Altim- TABLE 5·3. TEMPERATURE COMPENSATION PROCEDURE, DATA SHEET eter shall be tested in its normal operating position. Temperature Compensation Test Data Adjusted Data Pressure, Ambient Approximately 29.92 in. Hg (1013.2 millibars) Temperature Test Run Compensation Data Rest Period Prior to testing, the unit shall have been at re- Test -30°C (Cold Soak) Transitional Period +55°C (Hot Soak) Difference In Within qui red ambient pressure and ambient temper- Test Altitude Time Indicated Tolerance Indicated Tolerance Indicated Tolerance Altitudes Tolerance Error ature for a minimum of 12 hours. Step (Feet) Into Test Altitude (Feet) Altitude (Feet) Altitude (Feet) (Indicated- Test) (Feet) (Feet) 8 0 0 0 0 0 0 0 0 G @ @ Temperature, Ambient Approximately 77°F ±10° Vibration (To Minimize Friction) Performance testing is to be done with Encoding Start Test Altimeter subjected to vibration of 0.002 to 1 1000 0.0 Hours 0.005 inch double amplitude at a frequency of 1500 to 2000 cycles per minute. 3.0 (Column 4-1000) 2 1000 Hours ±40 Tapping (As a Substitute for If vibration equipment is not available, vibration Vibration) can be performed by lightly tapping the Encoding 3 Hrs (Column 6-1000) 3 1000 +15 Min ±70 Altimeter at the edge of the bezel and the top of the cover assembly. A hard rubber screwdriver handle may be used for this operation. 3 Hrs (Column 6-1000) 4 1000 +30 Min ±70 Primary Power 14 volt model 3 Hrs (Column 6-1000) 5 1000 +45 Min ±70 Voltage 13.75 ±.0.5 Vdc Current 600 milliamperes DC (maximum) 5 Hrs (Column 8-1000) 6 1000 End of Test ±50 28 volt model Voltage 27.50 ±0.5 Vdc Current 350 milliamperes DC (maximum) Individual Requirement The Encoding Altimeter under test shall be the model specified by the manufacturer. Clean Room These tests are to be performed within the con- fines of a clean room. 5-14 ing pins on the A2 board (see figure 5-3) must be strapped for NEGATIVE compensation. Potentiometer A2R 1 is then adjusted for re- quired dial pointer offset. d. If error is at +55°C and is greater than -50 feet, increase indicated altitude by the dif· terence between the error and -50 feet. In- crease dial pointer indication through adjust- ment of potentiometer A2 R 1. e. If error is at -30°C and is greater than +40 feet, increase indicated altitude by the dif- ference between the error and +40 feet. In· crease dial pointer indication through adjust· ment of potentiometer A2 R 1. f. If error is at -30°C and is greater than -40 feet, decrease indicated altitude by the dif· terence between the error and -40 feet. When decreasing altitude indication, the com· pensating pins on the A2 board (figure 5-3) must be strapped for NEGATIVE compensa- tion. Potentiometer A2R1 is then adjusted for required dial pointer offset. Step 19. When Encoding Altimeter has been temperature compensated, repeat this procedure to ensure validity of results of this procedure. Step 20. Proceed to performance tests and perform the complete set of tests. 5-14. PERFORMANCE TESTS. The following procedures are to be performed after repair, replacement of a subassembly, and after alignment, calibra- tion, or compensation procedures. Results of these tests will verify whether or not the Encoding Altimeter under test is accurately calibrated and up to performance standards. All of these tests are to be performed within the confines of a clean room. Test equipment and tools required for performance tests will be found in the listing under table 5-1. Unless otherwise specified, the conditions listed in table 5-4 (page 5-14) apply to all performance tests. 5-15. Input DC Voltage Adjustment. Step 1. Disconnect any external load from power supply OUTPUT jacks. Adjust unloaded power supply OUTPUT for rated voltage of Encoding Altim· eter under test. Use substep a or bas required. a. For a 14 volt model, adjust power supply OUTPUT for 13.75 ±0.5 Vdc. Record actual voltage in test step 1, column 2, table 5·5. Maintenance b. For a 28 volt model, adjust power supply OUTPUT for 27.5 ±0.5 Vdc. Record actual voltage in test step 1, column 3, table 5-5. Before interconnecting test cable, ad· just power supply for rated voltage of Encoding Altimeter under test. Failure to preset power supply may result in the application of an ex- cessively high voltage to Encoding Altimeter circuits. If this error is made, permanent damage to elec- tronic circuits will occur. Step 2. With power supply switch OFF, interconnect test cable only between test equipment and Encoding Altimeter as shown in figure 5-2. Leave static connection port on Encoding Altimeter disconnected. Step 3. Switch power supply ON and let equipment stabilize for five minutes. As power supply is switch ON, striped warning flag on En- coding Altimeter should disappear from view. Check FLAG indication in test step 2, column 5 or 6, table 5-5. Step 4. When equipment has stabilized, recheck rated DC voltage applied to Encoding Altimeter. If applied DC voltage is not as required, then readjust interconnected power supply per specifications given in step 1, substep a or b of this procedure. 5-16. Voltage Variation (±15%) Test. Step 1. With Encoding Altimeter connected as shown in figure 5-2, adjust Mensor to supply sea level atmospheric pressure (29.92 in. Hg or 1013.2 millibars). Step 2. Check power supply for nominal output vol- tage per substep a or b. a. For a 14 volt model: +13.75 Vdc b. For a 28 volt model: +27.75 Vdc Step 3. Vary power supply output voltage± 15% from nominal value as indicated in substep a or b. In every case, dial pointer indications shall not vary by more than ± 10 feet. a. For a 14 volt model: 11.7 to 15.8 Vdc. Re- cord dial pointer indication for each voltage in test step 3, column 8, table 5-5. 5-15 b. For a 28 volt model: 23.3 to 31.7 Vdc. Re- cord dial pointer indication for each voltage in test step 4, column 8, table 5-5. Step 4. Reset power supply output voltage to the value specified in step 2. 5-17. Reference Voltage (E/ 21 Adjustment. Step 1. Set Mensor Ps switch at SHUTOFF. Adjust Mensor to supply local atmospheric pressure. Step 2. On Encoding Altimeter, adjust BAROSET knob for an indication of 29.92 in. Hg (1013.2 millibars) in barometric pressure window . Avoid sudden application of high pressure differences between Encoding Altimeter and Mensor. Since Encoding Altimeter is at local pressure, be sure to adjust Mensor to local pressure prior to connecting or disconnecting static line on Encoding Altimeter. Capsule or other component damage may result from sudden application or rapid evac- uation of pressure from Encoding Altim- eter . Step 3. Interconnect air line between Mensor OUTPUT and static line fitting on Encoding Altimeter. (See figure 5-2.) Step 4. On Mensor, set Ps switch to OUTPUT and ad- just unit to supply seal level atmospheric pres- sure (29.92 in. Hg or 1013.2 millibars). Let pressure stabilize. 5-16 (1) cov ASSY (2) Jl RTNG SCR (3) Jl CONN 0392- 15 Figure 5-5. Encoding Altimeter Cover Assembly, Rear View Step 5. Observe Encoding Altimeter dial pointer and proceed as follows: a. If indicated altitude is 0.0 feet, adjustment is not required and this procedure is termin- ated . b. Note offset of dial pointer from 0.0 feet and continue with this procedure. Record altitude offset and direction in test step 1, column 3, table 5-6. If local altitude is well above sea level, removal of A 1 R6 cover screw (2, figure 5-5) will cause sudden evacuation of pressure within Encoding Altimeter. Avoid this condition by adjusting Mensor to supply local atmospheric pressure before removing A 1 R6 cover screw. Step 6. If local altitude is at or near sea level, remove A1 R6 cover screw. (5, figure 5-5). If local altitude is well above sea level, adjust Mensor to supply local atmospheric pressure before removing A 1 R6 cover screw. Let Encoding Altimeter dial pointer stabilize after A 1 R6 cover screw has been removed. Step 7. Adjust potentiometer A 1 R6 so that dial pointer is offset by the same amount and in the opposite direction as was noted in step 5b. Step 8. Replace A 1 R6 cover screw and readjust Men- sor to supply sea level atmospheric pressure (29.92 in. Hg). Encoding Altimeter's dial pointer should indicate an altitude of 0.0 feet with barometric pressure display of 29.92 in. Hg (1013.2 millibars). If this requirement is not met, repeat steps 4 through 8 of this procedure until the requirement is met. 5-18. Case Leak Test. Step 1. At rear of Encoding Altimeter's cover, check all screws (eleven) and static connection port fitting for tightness. Step 2. Adjust Mensor to supply atmospheric pressure of 20,000 feet. Let pressure stabilize. Encoding Altimeter should indicate 20,000 feet± 130 feet. Record altitude in test step 2, column 4, table 5-6. Step 3. On Mensor, place Ps switch at SHUTOFF. Step 4. On Encoding Altimeter, observe dial pointer. - Indication should not decrease by more than 100 feet over an elapsed time of one minute from pressure shutoff. Record dial pointer indi- cation in test step 2, column 5, table 5-6. 5-19. Slew Speed and Static and Slew Currents Measure- ments Tests. Step 1. Adjust Mensor to supply atmospheric pressure of 20,000 feet. Let pressure stabilize. Encoding Altimeter's altitude indication should be 20,000 feet± 130 feet. Digitizer readout should also indi- cate 20,000 feet. Record this data in test step 1, columns 3 and 4, table 5-7. Step 2. With Encoding Altimeter is quiescent state (dial pointer at rest). measure static current. Record measured current in test step 1, column 6, table 5-7. Step 3. Remove power to Encoding Altimeter by switch- ing power supply OFF. Step 4. Adjust Mensor to sea level atmospheric pressure (29.92 in. Hg or 1013.2 millibars). Let pressure stabilize. NOTE Read steps 5 and 6 before performing step 5. The current measurement of step 6 can be performed only during the slewing operation indicated in step 5. Step 5. Using stopwatch, note time required for Encod- ing Altimeter's dial pointer to return to an indi- cation of zero feet after power supply has been switched ON. A maximum of one minute is the specified time limit for this slew speed. Record elapsed time in test step 2, column 5, table 5-7. Record final altitude and digitizer indications in test step 2, columns 3 and 4, table 5-7. Step 6. As dial pointer slews toward an indication of zero feet, measure input (slew) current to En- coding Altimeter. Record measured slew current in test step 2, column 7, table 5-7. 5-20. Dial Pointer Scale Error Test. Step 1. With Encoding Altimeter connected as shown in figure 5-2, adjust BAROSET knob for an indica- tion of 29.92 in. Hg (1013.2 millibars). Step 2. On Mensor, set FUNCTION switch to MEASURE and Ps VENT/NORMAL switch to VENT. Step 3. The Encoding Altimeter is now subjected to am- bient pressure and should indicate local altitude. Maintenance Record altitude from dial pointer in test step 1, column 3, table 5-9 (Hysteresis and After Effect Test, Data Sheet). Also record value of atmos- pheric pressure indicated on Mensor in test step 1, column 3, table 5-9. Step 4. On Mensor, set FUNCTION switch to CONTROL and Ps VENT/NORMAL switch to NORMAL. Step 5. Sequentially perform test steps 1 through 20 of table 5-8. Observe the following for each test step. a. Using Mensor, approach each altitude at 8000 feet/minute until within approximately 500 feet of test altitude. Then, maintain an approach speed so that no overshoot of test step altitude occurs. b. Progress sequentially without regression. If a test step is omitted, repeat test from the beginning. c. When test step altitude is reached, let pres- sure stabilize before taking a reading. Record Encoding Altimeter altitude indication in appropriate test step, column 3, table 5-8. d. Note altitude indication on Digitizer. Indica- ted altitude should agree with altitude indi- cated on Encoding Altimeter's dial pointer. Enter a "D" next to test point in table 5-8 only if these two altitudes agree within tol- erance specified in column 5. Note any dis- crepancy in this same column and on back of table 5-8. e. Observe dial pointer for irregular motion, jumps, and evidence of backlash as pressure is uniformly changed. Note any irregularity on back of table 5-8. f. For certain test points, and after taking the scale error reading, a vibration reading is re- quired. The Encoding Altimeter is either vi- brated or tapped according to specifications of table 5-4. Record readings taken after vibration in selected test steps, column 4, table 5-8. These test steps are: 4, 6, 7, 8, 11, 13, 16, 18, 19, and 20. Step 6. At conclusion of scale error test, let atmospheric pressure to Encoding Altimeter remain at 35,000 feet. The starting point for the following test (hysteresis), is from the upper scale limit. 5-21. Friction Error Computations. Step 1. From table 5-8, scale error test data, determine the algebraic difference between data in columns 3 (before vibration) and 4 (after vibration). Step 2. Record these differences in column 6, table 5-7. Step 3. Observe that recorded differences in column 6, 5-17 fall within specified tolerances in column 7, table 5-8. 5-22. Hysteresis and After Effect Test. Step 1. Operate Mensor so that Encoding Altimeter's dial pointer decreases toward 25,000 feet. Approach at 8000 feet/minute until within approximately 500 feet of test altitude. Then, maintain an approach speed so that no overshoot of test step altitude occurs. Let pressure stabilize, Record Encoding Altimeter's altitude indication in test step 1, column 4, table 5-9. Step 2. Repeat the operation of step 1 for an altitude of 20,000 feet. Record the indicated altitude in test step 2, column 4, table 5-9. Step 3. Repeat the operation of step 1 for an altitude of zero feet. Record the results in test step 3, column 4, table 5-9. Step 4. On Mensor, set FUNCTION switch to MEASURE and Ps VENT/NORMAL switch to VENT. The Encoding Altimeter is now subjected to ambient pressure and should indicate local altitude. Re- cord altitude from dial pointer in test step 4, column 4, table 5-9. Step 5. From table 5-8, transcribe column 3 (BV) data for 0, 20,000, and 25,000 feet to the corres- ponding position under column 3, table 5-9. Step 6. In table 5-9, determine algebraic difference between data of columns 3 (Up) and 4 (Down) and record in column 5. These differences should not exceed the values specified in column 6. 5-23. Digitizer Transition Test. Step 1. Connect equipment as shown in figure 5-2. Step 2. Adjust Mensor until digitizer altitude readout indicates -900 feet (test step 1, column 2, table 5-10). Encoding Altimeter's dial pointer should indicate within the specified range (test step 1, column 3, table 5-1 0). Record Encoding Altimeter's actual altitude indication in test step 1, column 4, table 5-10. Step 3. Verify status of lamps for digitizer code against code word bits listed on data sheet (test step 1, columns 5 through 14, table 5-10. Step 4. Repeat steps 2 and 3 of this procedure for test steps 2 through 11, table 5-10. Record data and check code word bits in corresponding columns of table 5-10. Step 5. Verify that all recorded data falls within speci- fied tolerances listed in column 3, table 5-10. 5-18 5-24. Barometric Scale Error Test. Step 1. Connect Encoding Altimeter as shown in figure 5-2. Step 2. Adjust BAROSET knob for a barometric pres- sure indication of 28.50 in. Hg. Step 3. Adjust atmospheric pressure from Mensor until Encoding Altimeter indicates an altitude of 1340 feet. Do not change Mensor for the remainder of this test. Record indicated altitude in test step 1, column 5, table 5-11. Step 4. Adjust BAROSET knob for a barometric pres- sure indication of 28.10 in. Hg. Record indica- ted altitude of Encoding Altimeter in test step 2, column 5, table 5-11. Step 5. Repeat step 4 of this procedure for test steps 3 through 8, table 5-11. Record indicated altitude for each test step in column 5, table 5-11. Step 6. Determine algebraic difference between corres- ponding altitudes in column 4 and indicated altitudes in column 5, table 5-11 for all test steps. Step 7. Determine that each calculated difference in column 6 is within specified tolerance listed in column 7, table 5-11. 5-25. Position Error Test. Step 1. Connect Encoding Altimeter as shown in figure 5-2 but do not connect Mensor. Encoding Altim- eter will remain at ambient atmospheric pressure during this test. Step 2. With Encoding Altimeter in normal position, record its indicated altitude in test step 1, column 3, table 5-12. Step 3. Rotate Encoding Altimeter to remaining three sides (90°, 180°, and 270°) and record indicated altitude for each position in test steps 2 through 4, column 3, table 5-12. Step 4. Hold Encoding Altimeter vertically (dial upper- most) and record altitude indication in test step 5, column 3, table 5-12. Step 5. Determine that indicated altitude, for each posi, tion tested, does not exceed specified tolerances listed in column 4, table 5-12. 5-26. DISASSEMBLY PROCEDURES. The following procedures permit disassembly of the three main subassemblies of the Encoding Altimeter: Plate and Printed Wiring Assembly (figures 5-10 and 5-11); Capsule and Servo Assembly (figures 5-13 and 5-14); Counter and - - - Dial Assembly (figures 5-15 and 5-16). To reassemble the Encoding Altimeter, follow these procedures in reverse order. These procedures must be performed within the confines of a clean room. 5-27. Electronic Components. Electronic components may be located from schematic dia- gram (figure 6-1), photographs in this section, and from the illustrated parts list (figures 7-1,7-2,7-3, and 7-4). Replace- ment of components or of a complete printed wiring assembly can be performed at the field level. Once replaced, however, a complete set of performance tests in required to check Encoding Altimeter accuracy. Special mention, concerning the A2 printed wiring board, is required here. If a compon- ent or the complete A2 board is replaced, the temperature compensation procedure must be performed to verify accuracy of that function. The performance tests must then be performed. 5-28. Mechanical Compenents. Removal of gears requires special attention to the number of shims used to align the gear or gears. If a gear is removed, be sure to check the number of shims as disassembly proceeds. In the Counter and Dial Assembly, replacement of mechan- ical or electrical components can best be performed using the illustrated parts list (figure 7-3). The Capsule and Servo Assembly requires an accuracy in assembly which can be performed only at the manufacturer. Do not further disassemble the Capsule and Servo Assembly beyond the level described in this procedure. If the unit can- not be made to perform to required standards as outlined in performance testing, return the unit to the manufacturer for repair. 5-29. Cover Assembly, Removal Of. Step 1. Remove six retaining screws (2, figure 5-5) for connector receptacle J1. Step 2. Remove one screw (5, figure 5-5) from access slot for potentiometer A 1 R6. Step 3. Remove four cover assembly retaining screws (6, figure 5-5). Exercise care when removing or re- placing cover over main assembly of Encoding Altimeter. When re- placing cover, hold protruding wires and connectors away from cover to prevent damage to these items. Maintenance Step 4. Remove cover by sliding it towards rear of En- coding Altimeter main assembly. Step 5. When replacing cover, position 0-ring seal (14, figure 5-6) on top of outside perimeter of bezel (2, figure 5-6). Carefully slide cover for- ward until it just engages bezel rear flange (15, figure 5-6). Hold cover in this position and then slide 0-ring seal into groove between bezel and edge of cover. Slide cover forward to terminal position and partially engage one cover assembly retaining screw to retain cover. Be sure that 0-ring seal is completely seated before cover is secured. 5-30. Plate and Printed Wiring Assembly, Removal From Top Assembly. For some maintenance applications, it may not be necessary to cut cable lacing ties or to completely remove Plate and Printed Wiring Assembly from Encoding Altimeter. If this be the intent, terminate this procedure with step 2. Printed wiring assembly A 1, will then be accessible to effect minor repair. At this stage of disassembly, the plate may be separ- ated from the printed wiring assembly be performing Plate and Printed Wiring Assembly disassembly procedure. Step 1. Disconnect connectors J3, J4, and P5 (8, 5, and 9, figure 5-6). Step 2. Remove four retaining screws (1, figure 5-11) from rear plate. NOTE Observe and note location of all cable lacing ties to be removed in step 3. Replace all cable lacing ties, that were removed during disassem- bly, with new lacing cord when re- assembling unit. Step 3. Slowly, withdraw Plate and Printed Wiring Assembly to a point where interconnecting wiring is visible. Cut only cable lacing ties necessary to free connectors J3, J4, and P5 (8, 5, and 9, figure 5-6). Step 4. Remove Plate and Printed Wiring Assembly from Encoding Altimeter. 5-31. Plate and Printed Wiring Assembly, Disassembly Of Unit. Step 1. Lightly, squeeze front and rear of assembly to- gether and completely loosen four retaining screws (1, figure 5-10) on printed wiring assem- 5-19 bly A 1. Maintain pressure to prevent four sleeve spacers (3, figure 5-8) from falling out. Step 2. Separate plate from printed wiring assembly. Set aside fastening hardward (4 screws, 4 lock- washers, and 4 sleeve spacers). Step 3. Remove braided wire heat sink (6, figure 5-6) from its receptacle and set it aside while working with printed wiring board. Be sure to replace this item when reassembling unit. 5-32- Capsule and Servo Assembly, Removal Of. The Capsule and Servo Assembly is not to be further dis- assembled other than described in this procedure. Dis- assembly beyond separation of this unit from the top assem- bly of the Encoding Altimeter cannot be performed with- out special tools, gauges, and test equipment. If a defective subassembly is apparent, from results of alignment, cali- brating temperature compensation, or performance tests, return the Capsule and Servo Assembly to the manufacturer for repair. Step 1. Remove Plate and Printed Wiring Assembly (refer to procedure). 5-20 Step 2. Disconnect connector plug P2 (3, figure 5-7). Step 3. Remove four threaded rods (6, figure 5-8) using a box wrench. Step 4. Partially loosen sector gear lever locking screw (3, figure 5-12). Slide sector gear lever to side to disengage servomotor gear train from Counter and Dial Assembly. Step 5. Slide Capsule and Servo Assembly straight out and away from Dial and Counter Assembly. At This point, the Encoding Altimeter has been dis- assembled into its three main subassemblies. NOTE When reassembling Capsule and Servo Assembly with Counter and Dial Assem- bly, be sure that mating pins ( 1, figure 5-14 and 4, figure 5-15) are aligned with their receptor holes. Be certain that these mating pins are fully seated when retight- ening mounting hardware. (15) BEZEL REAR (14) 0-RING SEAL (13) MTl ENCODER TRANSDUCER (11) J2 CONNECTOR SOCKET (10) P 2 CONNECTOR PLUG (8) J3 CONNECTOR SOCKET (1) ALTITUDE DRUM COUNTER DRIVE GEARS (7) SLEEVE SPACER (4 E A C H) (2) OUTSIDE PERIMETER OF BEZEL (3) BAROSET DISPLAY DRIVE GEAR ----(4)P4 CONNECTOR PLUG ----( 5)J4 (6) BRAIDED W IR E HEAT S INK CONNECTOR SOCKET 0392·16 Figure 5-6. Encoding Altimeter, Left -Side View (15) CO~ / >ENSATING PINS (7 EACH) ( 14) SET SCREW (7 EACH) (13) ALT I TUDE COMPENSATION CAM (12) TORSI O N SPRING (11) TENSIONING HELI CAL SPRING (lO)C O NTA CT LE VER (9) P3 CONNECTOR PLUG (L OWER ) SOCKET (UPP ER ) (1) 52 ALTITUDE LIM IT SW ITCH (UPPER LIMI T) (2) J2 CONNECTOR SOCKET ( 3) P2 CO NNECTOR P LUG LIMIT SWITCH (LOWER LIMIT) (5) REAR SE RVO PLATE ALTITUDE COMP ENSATOR VANE LEVER (7) ALTITUDE COMPE NSA TOR VANE Figure 5-l. Encoding Altimeter, To p View (8) A3 PR I NTED WIRING BOARD (7) A2 WIRING BOARD CAPSULE AND SERVO ASSEMBLY Figure 5-8. Encoding A ltimeter, Right-Side View (1) ALT I TU DE COUNTER M I TE R GEAR (2) ALTI T UDE COUN T ER BE VEL GEA R (3) DIFFERENTIAL GEAR (5) SPACER PLA T E TO PRINTED W I RING BOARD (4 EACH ) (4) WO RM GEAR 03 9 2· 18 ( 8 ) A3 PRIN TED WIRING BOARD ( 7 ) SER VOMOTOR B1 (6 ) CAPSULE AND SERVO ASSEMBLY R EA R PL ATE Maintena nce -LJ ~ ----- (1 ) E NCODER - DISK Figure 5-9. Encoding A ltim eter, Bottom View DR I V E GEAR ( 2 ) ENCODER D ISK ( 3 ) A2R1 POTENT I OMET ER (4 ) A2 PR I N T E D W I R I NG B OARD (5 ) ANEROID CAPS U LE 0 39 2 - 19 5-21 /5-22