Presentation on theme: "EFD1000 to Century II/III Autopilot Interface Training & Troubleshooting Presented by Tim McNany Field Service Engineer October, 2011."— Presentation transcript:
EFD1000 to Century II/III Autopilot Interface Training & Troubleshooting Presented by Tim McNany Field Service Engineer October, 2011
Agenda 2 Century II/III Basics Radio Coupler types What’s a Lubber line Roll Centering Alignment to the ACU Alignment of R1 Roll Centering Adjustment Troubleshooting HDG/CRS Datum signal flow
Operation of DG version Radio Couplers 1C388, 1C388M, 1C388C, 1C388MC Uses Left/Right deviation from the GPS/NAV or in the case of the EFD1000, the ACU. ACU HDG Datum output (PFD HDG Bug) controls A/P HDG Mode ACU HDG Datum output controls GPSS operation via autopilot HDG Mode ACU HDG Datum output controls the autopilot “CRS*” input in NAV/OMNI/LOC Modes *CRS input is the heading datum input with these radio couplers (the PFD HDG Bug will be used in place of the CRS pointer) Century II/III Basics 3
Operation of HSI version Radio Couplers 1C388-2 and 1C388-3 Uses Left/Right deviation from GPS/NAV or in the case of the EFD1000, the ACU. ACU HDG Datum output (PFD HDG Bug) controls autopilot HDG Mode ACU HDG Datum output controls GPSS operation via autopilot HDG Mode ACU CRS Datum (PFD CRS pointer) output controls the autopilot CRS input in NAV/OMNI/LOC Modes 4
Lubber line 12 o’clock position of the CRS Pointer or HDG Bug Autopilot Basics 5
45⁰ right of Lubber line Autopilot Basics 6
90⁰ left of Lubber line Autopilot Basics 7
Roll “null” Centering All autopilots have a roll centering adjustment including the Century II/III. The roll centering adjustment is used to “null” out any offsets in the VG (Attitude Indicator) or HDG Datum signal. Most installations will require the adjustment of the roll centering pot after the installation of the EFD1000. Why? The mechanical DG or HSI that is removed did not have a centered HDG Datum when the HDG Bug was under the lubber line. The ACU does. Autopilot Basics Aircraft flies right or left of the runway during approach or the CDI does not center in NAV/LOC modes Aircraft flies right or left of GPS course line in GPSS mode Symptoms HDG Bug does not center in HDG Mode 8
When it’s not a Roll “null” Centering Issue Usually the HDG bug is within 0-10 degrees of the lubber line if it is a roll null issue. If the HDG bug is out of center more than this it is more likely a wiring issue or an ACU with a shorted HDG or CRS output. Autopilot Basics Symptom HDG Bug is more than 10° out of center when the yoke nulls in HDG Mode. 9 Causes R1 has not yet been adjusted for a 45° intercept angle (see Slides 12-17) Verify wiring between the ACU and the transformers is correct. Check radio coupler pin A for 0vrms when the HDG Bug is under the lubberline. If not 0vrms then the ACU HDG Datum (pin 22) output has gone bad. Make sure the wiring is not shorted and then replace the ACU. VG must be level (can be unplugged) during this test
10 Aircraft must be in proper trim (rudder and aileron) Verify slip/skid ball is centered – if not, apply appropriate rudder command to center. If HDG bug is now centered no further action is required. (may look into adjusting rudder trim tab) Make small adjustments to autopilot roll “null” centering pot Allow 15 seconds or so for autopilot to settle Re-adjust pot as necessary, waiting 15s between adjustments, until HDG Bug is centered or aircraft is on course Autopilot Basics In Air - Roll “null” Centering Adjustments (Follow autopilot manufacturers’ instructions)
Century II/III Radio Coupler R1 Alignment and Theory 11 Radio CouplerComputer AMP It is recommended that a pre-EFD1000 flight test be performed on the autopilot to verify acceptable operation Disclaimer – The following pages contain information that should only be used to align the ACU to the radio coupler and it assumes the radio coupler was properly aligned and functioning correctly prior to the EFD1000 installation. Follow all autopilot manufacturers instructions for any needed autopilot alignments or for autopilot return to service instructions.
Three ways to align the ACU to the Radio Coupler 1.Prior to removal of the DG/HSI you would measure the HDG Datum voltage (radio coupler pin A) when the HDG Bug is 90⁰ off of the lubber line. After the EFD1000 installation, set R1 so that the ACU generates the same voltage at pin A. 2.Roll the vertical gyro (AI or Attitude Indicator) 10⁰ left and then put the HDG Bug 10⁰ left. Put the selector in HDG mode and engage the A/P. Adjust R1 so that the yoke is still. This may be the easiest option with the Century gyro substitution box. 3.Adjust R1 to produce a 45⁰ intercept angle in “OMNI” mode. Instructions to follow. Century II/III - Alignment 12
Century II/III interface with Radio Couplers 1C388, 1C388M, 1C388MC, 1C388-C only HDG Datum input only, therefore HDG Bug controls HDG/NAV/OMNI/LOC Modes CRS Pointer position is irrelevant R1 is set for a 45⁰ intercept angle: Procedure: Century II/III - Alignment 3. Engage the autopilot in “OMNI” mode 2. Position the HDG Bug 45⁰ right on the PFD 1. Generate a full deflection CDI left using VOR/ILS signal generator 13 AI must be level (can be unplugged) during this test 4. Adjust R1 until the yoke stops turning.
Century II/III interface with Radio Couplers 1C388, 1C388M, 1C388MC, 1C388-C only Likewise: Century II/III - Alignment CDI full scale right HDG Bug 45⁰ left Nulls the yoke 14 If you have trouble adjusting R1 to stop the yoke movement. Turn the HDG bug from 5° to 90° to locate the spot where the yoke moves back and forth following the bug. If this position is less than 45° then R1 is too small. If it is higher than 45° then R1 is too large.
Datum Signal Flow 15 R1: 0-300KΩ
Century II/III interface with Radio Couplers 1C388-2 and 1C388-3 only These use CRS Datum input for NAV/OMNI/LOC Modes (HDG Bug position is irrelevant) R1 is set for 45⁰ intercept angle: Procedure: Century II/III - Alignment AI must be level (can be unplugged) during this test 1. Generate a full deflection CDI left using a VOR/ILS signal generator 2. Position the CRS Pointer 45⁰ to right on the PFD 3. Engage the autopilot in “OMNI” mode Adjust R1 until the yoke stops turning
Century II/III interface with Radio Couplers 1C388-2 and 1C388-3 only Likewise: Century II/III - Alignment CDI full scale right CRS Pointer 45⁰ left Nulls the yoke 17 If you have trouble adjusting R1 to stop the yoke movement. Turn the CRS Pointer from 5° to 90° to locate the spot where the yoke moves back and forth following the CRS. If this position is less than 45° then R1 is too small. If it is higher than 45° then R1 is too large.
Datum Signal Flow 1C and -3: 0-5KΩ 18
Century II/III - Alignment On Ground - Roll “null” Centering Adjustments (Note – this will get it close. Follow autopilot manufacturers’ instructions for final adjustment) 1.Un-plug the VG (AI), (52C77, 52D267, etc) 2.Sync the HDG Bug to the lubber line 3.Engage the A/P in HDG mode 4.Adjust the autopilot roll centering pot until yoke is still Do Not forget to re-connect the VG (AI) connector if removed! 19
20 The 1C388, 1C388C, 1C388M and the 1C388MC radio couplers can be replaced with a 1C388-2 or 1C388-3 radio coupler if the customer desires the CRS Pointer to drive the autopilot like an HSI. If you are having difficulty obtaining the 45° intercept angles or the autopilot does not respond to the heading bug the way it did with the old DG installed then you could have one of the radio couplers with a lower input impedance. Try using a TY-145 or SP-67 transformer for T2 as shown in Installation Manual Rev Z or later. Century II/III - Extras The End