2022-12 · NASA ASRS report 1963999
B737 MAX 8 flight crew reported multiple failures of the Captain's Air Speed and Altitude indications in descent. Flight crew continued to destination airport and landed.
Event began when descending through 10;500 ft. for 10;000 ft. at ZZZZZ Intersection on the ZZZ / ZZZZZ arrival. Autopilot and Auto Throttles were engaged with LNAV/VNAV selected and FO (First Officer) side selected as Master. As I (FO; PF (Pilot Flying)) monitored the descent in anticipation of level off; the Captain and I observed 'IAS DISAGREE' display on our PFDs. A 10-15 KIAS difference between our IAS was noted. All other indications were normal. As the Captain reached for the QRH I completed the memory items for Unreliable Airspeed and ensured aircraft flight path and controllability were maintained.This QRH procedure is complex with many decision trees. In order to balance resources and keep both Pilots in Normal; I handled ATC radio communication; ensuring the Captain was aware of all instructions issued; while he completed the QRH procedure ensuring I was participating in all decisions required to be made throughout the procedure. As we worked through the QRH items we determined the Captain side IAS was defective while my side was reliable; based on its close correlation with the standby IAS. We re-engaged the Autopilot but kept Auto Throttles off. Luckily we arrived in the [area] between bands of weather/precipitation. Although VMC conditions existed in our general area; lingering showers and IMC ceilings covered ZZZ and the Runway XX final approach course. We requested priority handling to expedite our approach and landing at ZZZ and prevent any adverse vectors/maneuvering due to traffic and ensure a suitable approach.As we proceeded to ZZZ we noted nonsensical winds and TAS/GS displays on the MFDs (At one point TAS at 10;000 ft. showed in excess of 400 kts.). The Captain's Altimeter began to show fluctuations large enough to cause the 'ALT DISAGREE' message to display. Although my IAS and Altimeter appeared normal; we solicited occasional ATC ground speed and Mode C altitude readouts to verify our indications. ATC provided this information at our request until touchdown. We also received wind direction and speed from adjacent aircraft in order to resolve our airspeed and ensure my IAS remained accurate. Additionally; the Captain kept the QRH reference charts for pitch/power out and as we changed flight parameters we referenced the charts to ensure aircraft airspeed/performance met expectations.Utilizing these resources in this manner kept both us in Normal and we never had a doubt as to the airspeed of the aircraft; despite the continued malfunction of the Captain IAS indication. With this knowledge we completed a normal ILS approach and landing. Turning off the runway we cancelled the request for priority handling and taxied to the gate.Even though we knew the Captain side IAS was defective the 'BUFFET ALERT' FMC messages and aural 'AIRSPEED LOW' warnings received were a distraction. In the future it would be helpful to somehow silence these warnings.
Descending through 10;000 ft.; night IMC; IAS DISAGREE Warning Illuminated. Captain's airspeed gradually decreased 50 kts. less than FO's (First Officer). Airspeed Unreliable Checklist initiated. ALTITUDE DISAGREE Warning then Illuminated. Captain's Altitude decreased 500 ft. below FO's. FO's instruments matched the Standby Instruments and ground speed verified by ATC. Priority handling requested. Multiple AIRSPEED LOW Audible Warnings received. QRH Performance Inflight tables used to verify FO's instruments and N1s. FO flew IMC ILS to uneventful landing.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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