Narrative:

The crew reported a 'stall fail' crew alerting system (cas) message in flight that was intermittent. The crew followed the abnormal checklist and disengaged one side of the stall warning system for the remainder of the flight. Upon inspection after landing; it was found that the right-hand (right/H) angle of attack (aoa) transducer voltage checks failed. These voltage checks were provided by bombardier technical support and not listed in the maintenance manual (M/M). The unit in question passed the linearity (resistance checks) which is a required check every 300 flight hours. It was interesting that the resistance checks passed but the non-published voltage checks failed.there is an airworthiness directive (ad) (ad 2003-22-12) for this system for the bombardier CL604 challenger model; but not for the CL605 system. This ad requires that the resistance be checked every 300 hours. This unit would have passed that check. The voltage check showed a voltage error of approximately .8 volts low for every five degrees of aoa travel. This equaled approximately four degrees of error between the left/H and right/H aoa vane which caused the stall fail message to illuminate. The right/H aoa transducer was replaced with a new unit and the aircraft was returned to service.it should be noted that the required aoa transducer resistance check may not be enough on its own to check the serviceability of these units. Bombardier aoa transducer part number (P/north) 600 59154-3.

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Original NASA ASRS Text

Title: An Aircraft Maintenance Technician (AMT) with Avionics experience reported the Linearity Resistance Check of AOA Vane Assembly transducers required by Airworthiness Directive (AD) on Bombardier aircraft should include a Voltage Check to properly determine the Serviceability of the AOA assemblies. Troubleshooting for an inflight 'Stall Fail' CAS warning revealed that the Right AOA vane had passed the Resistance Check; but failed the Voltage Check.

Narrative: The crew reported a 'Stall Fail' Crew Alerting System (CAS) message in flight that was intermittent. The crew followed the Abnormal Checklist and disengaged one side of the Stall Warning System for the remainder of the flight. Upon inspection after landing; it was found that the Right-Hand (R/H) Angle Of Attack (AOA) transducer Voltage checks failed. These Voltage checks were provided by Bombardier Technical support and not listed in the Maintenance Manual (M/M). The unit in question passed the Linearity (Resistance Checks) which is a required check every 300 flight hours. It was interesting that the Resistance Checks passed but the Non-published Voltage Checks failed.There is an Airworthiness Directive (AD) (AD 2003-22-12) for this system for the Bombardier CL604 Challenger model; but not for the CL605 system. This AD requires that the resistance be checked every 300 hours. This unit would have passed that check. The Voltage Check showed a voltage error of approximately .8 volts low for every five degrees of AOA travel. This equaled approximately four degrees of error between the L/H and R/H AOA Vane which caused the stall fail message to illuminate. The R/H AOA transducer was replaced with a new unit and the aircraft was returned to service.It should be noted that the required AOA Transducer Resistance Check may not be enough on its own to check the serviceability of these units. Bombardier AOA transducer Part Number (P/N) 600 59154-3.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.