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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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Quick Links

03/02/21

Message Overview:

Message Name:

ISI / ADC MACH DISAGREE

Message Code:

B3-007965

Associated CAS:

STALL PROTECT FAIL
(Caution)

Reporting LRU: STALL COMPUTER
System Description: 27-32-00
Schematic Diagram: 27-32-00
Wiring Diagram: 27-32-01

Message Description:

The ADC MACH and ISI MACH miscompare. Verify the ADCs and ISI.

Possible Causes:

  • Pitot-Static Probes
  • Integrated Standby Instrument (ISI) (A90)
  • Air Data Computer 1 (ADC) (A1)
  • Air Data Computer 2 (ADC) (A2)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin:

  • AW300-27-34-0010 - Integrated Standby Instrument (ISI) Airspeed Indication Fluctuation & Potential STALL PROTECT FAIL and/or RUDDER LIMITER FAULT Messages (20501 - 20999)

Forum Articles/Infoservice/Newsletter: None

Potential airspeed fluctuations, "STALL PROTECT FAIL" and "RUDDER LIMITER FAULT" Crew Alerting System (CAS) messages may be experienced after the aircraft has been in heavy or extended rain in flight or on the ground.

To clear the "STALL PROTECT FAIL" message that may be due to water ingestion, the following troubleshooting can be used:

CAUTION: ENSURE THE PROBES COVERS ARE REMOVED.

  1. Activate the probe heaters on ground with the following limitations: The probe heaters should not be activated on ground in still air for longer than 5 minutes.
  2. After five minutes, if the messages are still present, assume that water in the probe is not the cause of the failure.
  3. Visually inspect the probes for contamination that may be preventing proper operation of the probes. Refer to Aircraft Maintenance Manual (AMM) tasks for cleaning of the Pitot-Static Probe and cleaning of the Standby Pitot Probe.
  4. Water accumulation further in the line beyond the probe should also be considered if the fault does not clear. Visually inspect the drain tube for the P-3 pitot line per AMM to ensure that no moisture is present.

Quick Links:

Removal of the Junction Box JB3 AMM 24-63-09-000-802
Installation of the Junction Box JB3 AMM 24-63-09-400-802
Functional Test of Junction Box JB3 AMM 24-63-09-720-801
Operational Test of the Stall Protection System (SPS) AMM 27-32-00-710-801
Removal of the Stall Protection Computer AMM 27-32-01-000-801
Installation of the Stall Protection Computer AMM 27-32-01-400-801
Removal of the Data Concentrator Unit (DCU) AMM 31-41-01-000-802
Installation of the Data Concentrator Unit (DCU) AMM 31-41-01-400-802
Removal of the Integrated Standby Instrument AMM 34-12-01-000-801
Installation of the Integrated Standby Instrument AMM 34-12-01-400-801
Functional Test of the Integrated Standby Instrument AMM 34-12-01-720-801
Removal of the Air Data Computer AMM 34-13-01-000-801
Installation of the Air Data Computer AMM 34-13-01-400-801
Functional Test of the Air Data Computer AMM 34-13-01-720-801
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02
Electrical Connectors - Maintenance Practice - ALL SPM 20-20-00-02

Troubleshooting Recommendations:

  1. Reset circuit breaker CB1-C1 AIR DATA 1 and CB2-C1 AIR DATA 2.

    1. If system check are good, do close out.
    2. If fault remains, continue to next step.

  2. On center, cycle off/on the STBY INST pushbutton.

    1. If system check are good, do close out.
    2. If fault remains, continue to next step.

  3. In Maintenance Main Menu, select LRU INDEX/OPERATIONS and check Stall Computer label 354.
  4. Check status of SPC label 354 bit 22.

    1. If bit 22 = 0, go to step 7.
    2. If bit 22 = 1 and NO ISI MACH INPUT is shown on MDC, continue to next step.

  5. Inspect SPC connector A178A or ISI connector A90P1 for pin damaged. Repair/replace as required.

    1. If system check are good, do close out.
    2. If fault remains, continue to next step.

  6. Do wiring checks between SPC and ISI. Repair as required.

    1. If system checks are good, do close out.
    2. If fault remains continue to next step.

  7. Check status of SPC label 354 bit 29.

    1. If bit 29 = 0, go to step 11.
    2. If bit 29 = 1 and NO ISI MACH INPUT is shown on MDC, continue to next step.

  8. Inspect SPC connector A178AP1 and ADC connector A1P1 for pin damaged. Repair/replace as required.

    1. If system check are good, do close out.
    2. If fault remains, continue to next step.

  9. Inspect SPC connector A178BP1 and ADC connector A2P1 for pin damaged. Repair/replace as required.

    1. If system check are good, do close out.
    2. If fault remains, continue to next step.

  10. Do wiring checks of L-ADC-6 and R-ADC-6 ARINC bus between SPC and ADC. Repair as required.

    1. If system checks are good, do close out.
    2. If fault remains continue to next step.

  11. Replace ADC.
  12. Do close out.

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