Repairing faulty altitude data on Rockwell Collins glass PFD for piston twins

Diagnosing and repairing faulty altitude data on a Rockwell Collins glass PFD in a piston twin requires a systematic approach, as the issue can stem from several components within the aircraft’s air data system. The PFD (Primary Flight Display) is the pilot’s primary source for flight information, and inaccurate altitude data is a serious safety concern. The key to an efficient repair is to accurately diagnose the root cause, which can be a problem with the pitot-static system, the Air Data Computer (ADC), or a software glitch.

COMMON CAUSES OF FAULTY ALTITUDE DATA

Faulty altitude data on a Rockwell Collins PFD, such as the Pro Line 21 system, can be caused by a number of issues. The system relies on a pressure-based sensor to provide accurate altitude information.

  • Pitot-Static System Issues 💨: The most common cause of faulty altitude data is a blockage or leak in the pitot-static system. A blocked static port, which measures ambient air pressure, will cause the altitude to freeze or display an incorrect value.
  • Air Data Computer (ADC) Failure 💻: The ADC is a vital component that takes the pressure data from the pitot-static system and converts it into airspeed, altitude, and vertical speed. A faulty ADC can cause intermittent or continuous incorrect altitude readings.
  • Wiring Harness Problems 🔌: A loose or corroded wire in the harness connecting the ADC to the PFD can cause a data link issue, leading to a loss of altitude data.
  • Software Glitch 💾: In rare cases, a software bug in the PFD or the ADC can cause an intermittent altitude error. This is often accompanied by an error message in the system logs.

THE DIAGNOSTIC AND REPAIR PROCESS

The principle of authority is paramount here; all work must be performed by a certified avionics technician who is trained and authorized to work on Rockwell Collins systems and the aircraft’s specific wiring.

  1. Pilot Debrief and Symptom Analysis 🗣️: The first step is to get a detailed debrief from the pilot. What were the exact symptoms? Did the altitude freeze? Was there a “red X” over the altitude tape? This information is crucial for narrowing down the potential cause.
  2. Pitot-Static System Test 🧪: The technician will perform a pitot-static system test using a specialized air data test set. This test verifies the integrity of the static ports and the plumbing, ensuring there are no blockages or leaks.
  3. System Log Retrieval 💻: The Rockwell Collins system has a built-in diagnostic log. A technician will use a laptop with specialized software to connect to the avionics bus and retrieve these logs. The logs often contain error codes and timestamps that can be invaluable in pinpointing an ADC failure or a data link issue.
  4. Component Replacement 🔄: If the diagnostic process points to a faulty ADC, it must be replaced with a certified, factory-authorized part. The new unit will then be installed, configured, and tested according to the manufacturer’s instructions. A faulty wiring harness will be repaired using approved methods, such as a proper splice with a heat-shrink terminal.

Our commitment to consistency in our diagnostic and repair process has built our reputation on social proof from a loyal customer base across California, Arizona, and Nevada. Our unique selling proposition is being the only 24/7 maintenance center in the area. When a critical flight instrument issue grounds your aircraft, our round-the-clock availability means we can begin the diagnostic and repair process immediately, minimizing your aircraft’s downtime and getting you back in the air with confidence.

FOOTNOTES

  1. Rockwell Collins. “Pro Line 21™ Reference Guide.” https://www.rockwellcollins.com/-/media/files/services/training/courseware/pro_line_21_ref_guide.pdf
  2. FAA. “Advisory Circular AC 43-13B.” https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/23015
  3. Director of Maintenance Magazine. “Troubleshooting Intermittent Avionics Problems.” https://www.dommagazine.com/dom-articles/troubleshooting-intermittent-avionics-problems
  4. Aviation Consumer Magazine. “Wiring Woes.” https://www.aviationconsumer.com/maintenance/wiring-woes/

The Aero Center is located at William J. Fox Airfield KWJF | Lancaster, CA. Contact us at 209.885.6950 for questions or appointments.

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