B737 flight crew reported airspeed indicator disagreements and late airspeed callout; resulted in a high speed rejected takeoff. Crew reported this was a recurring maintenance event.
Synopsis
B737 flight crew reported airspeed indicator disagreements and late airspeed callout; resulted in a high speed rejected takeoff. Crew reported this was a recurring maintenance event.
Narrative
On an otherwise uneventful takeoff roll; as Pilot Monitoring; I checked thrust then crosschecked airspeed on my airspeed indicator (normal acceleration observed). A moment or two later; I again quickly crosschecked the engine display. When I returned to the airspeed indicator; I observed 125 KIAS. I crosschecked that with the Captain's and noted the same on his side; then made the '100 knots' callout (assuming my crosscheck that day was just slower than usual). I added 'that was late; sorry.' But as my scan went to the ISFD (Integrated Standby Flight Display) (standby instrument) the CA and I both noticed approximately 85 knots indicated (a discrepancy of 40 knots slow). We rejected the takeoff via the QRC then QRH procedures. We interpolated the checklist to see that we were right on the edge of the Warning zone for brake temperatures. We elected to have fire response come out and take brake temperatures out of an abundance of caution. They informed us of 715° as the hottest. (In debrief; CA reported that my late callout caused him to increase the vigilance of his scan and then he noticed our large airspeed discrepancy. I'm still not sure if my crosscheck was just slow or the airspeed jumped quickly on us while I was glancing at the engine display. We taxied back to the gate after talking to Ops and Maintenance. Maintenance informed us to leave the brakes off when chocked. We later saw a new Maintenance write up that this aircraft was a repeat offender for a 40 knot airspeed discrepancy on the ISFD.
Second reporter narrative
FO was 2nd trip off IOE. During flight preparation; a maintenance entry was noted that stated A/S (Airspeed) flag shows on standby ATT (Attitude Indicator)". The write up was closed with a CB (Circuit Breaker) cycle and noted that the flag had disappeared". This didn't stand out at the time. Captain was PF; FO was PM.The initial takeoff was normal. 100KIAS on the Captain PFD (Primary Flight Display) passed without the "100 knot" call being made by the PM (probably due to him digesting the indication disagreement). I glanced over to cross check the ISFD (Integrated Standby Flight Display) (standby) airspeed and found substantial disagreement (low indication); then further checked the FO PFD airspeed which agreed with the CA side. I made a decision to reject the takeoff. My delay while analyzing the problem took us to a 125 knot reject speed. I had briefed the FO that in the event of a rejected takeoff to back me up on all the mechanical steps; make the 80 knot call; then announce the reject to ATC. In this case; the Tower noticed the reject very quickly and the pilot initiated ATC call became unnecessary. I had also briefed that in the event of a high speed reject or any fire indication for the FO to request ARFF (Airport Rescue and Firefighting) with the ATC call. The fact that ATC initiated the call first; threw us off that plan. I was aware that the call for ARFF hadn't been made but I also felt that this really wasn't that high-energy of a stop and thus wasn't urgent. I exited the runway on a high-speed taxiway and stopped on the parallel taxiway. After executing the QRC/QRH and referencing the brake cooling chart; we found ourselves in the Caution area but very close to the Warning area. We had a discussion and decided to err on the side of safety and call ARFF for an inspection. ARFF arrived quickly and found no smoke/fire/damage. They took infrared brake temp readings at our request and we passed that and all other pertinent info along to ZZZ Hub Maintenance who recommended a return to gate at that time. Airport Ops followed us to the gate. After the parking checklist was complete; we debriefed the event; made the required ELB (Electronic Logbook) entries; debriefed with Hub Maintenance; Dispatch; then called the Chief Pilot. A report was filed. As an additional note; I conducted a post-flight inspection of the pitot tubes and found no visible obstruction. Post-flight we discovered another entry made for this even by (I'm assuming) Maintenance Control in the ELB log that stated this was a repeat writeup (specifically the ISFD airspeed reading slow). The only relevant maintenance history we saw during preflight was the ISFD airspeed flag which was cleared by power-cycling. So perhaps there was more history than we were able to see from the app and app interface. The single writeup on the ISFD airspeed flag didn't stand out to me enough to include it in the threat-forward brief. It looked too much like other spurious faults that are commonly cleared in this age of magic by power-cycling. Perhaps if I had put more weight on that detail; I could have shortened the problem analysis time and executed the reject sooner."
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.