2022-02 · NASA ASRS report 1877263
B737-800 flight crew reported an airspeed unreliable condition during the takeoff roll. The crew stated the condition was near or through Vr (rotation) and they continued. Once airborne the crew completed the QRH and returned to the origin airport.
On takeoff roll the Captain (Pilot Monitoring) called 80 kts. Shortly after that he stated something was wrong and we had an IAS Disagree light. About that time we got a Master Caution light with the Engine light illuminated on the six pack. I quickly scanned the engines and they were good. I then looked at my airspeed and we were past VR and quickly eating up runway. I said Rotate? When I didn't hear anything; and saw how much runway was left; I rotated. The aircraft felt like it was accelerating and I felt comfortable rotating.Once airborne we quickly determined my airspeed was correct (crosschecked standby and ground speed). The Captain's airspeed was initially 20-30 below mine; once airborne it was 5-10 below. The Master Caution light went out sometime on climb out. We cleaned up the aircraft and leveled off at 5;000 feet to run checklists. While running the Airspeed Unreliable Checklist the Master Cation and Engine lights came on again; we scanned the engines and the overhead panel and could not find what was causing the lights. They went out after about 20 seconds.We landed uneventfully back at ZZZ. [The First Officer's response and question] is what caused the Master Caution and Engine lights during this event. Nowhere in the Quick Reference Handbook does it say this could be an indication associated with the airspeed disagree. It was extremely distracting during an already stressful event. I suspect one of the Electronic Engine Control's went into the ALT mode causing it. In any event; the Quick Reference Handbook should add this as a possible indication associated with an IAS disagree.
On takeoff roll; near 90 kts. I noticed my airspeed indicator sluggish; just then First Officer questions 'Rotate?'; I looked out the windscreen at the end of the runway approaching quickly and First Officer's and Standby Airspeed Indicator's and stated 'Rotate'. We got airborne and still had a 20-30 kt difference; but we quickly determine it was Captain Airspeed indicator was erroneous. At that point we ran the Airspeed Unreliable Quick Reference Checklist and Quick Reference Handbook cleaned up the Airplane and asked for Vectors to work the problem and talk to company. We use Ops Frequency for a patch to Dispatch for guidance as we're running Performance Weight and Balance landing speeds; Dispatch told us we could land back in ZZZ1 and there was a spare aircraft available.We ran Performance Weight and Balance as well as diversion checklist; and still in the Airspeed Unreliable Checklist. We asked ATC for a return to ZZZ1 and landed with no other problems. Once safely on the ground we ran Brake Cooling; time not required. We had an overweight landing was caused by the Air Return. ZZZ2 was not as Cooperative as I wished they might have been. They asked us to go into a hold; which I declined and asked again for vectors. Then on final and still in Quick Reference Handbook and briefing flight attendants and passengers; ZZZ2 wanted us to go off and pick up new ATIS. I requested the information be read to us; they did eventually give it to us.Maybe I should have declared an emergency as to eliminate the extra threats. Once on the ground or maybe on approach; I'm unsure when it happened; as we were trying to keep from getting a stick shaker on the approach; we received an Engine Master Caution for just a few seconds; or maybe even a minute. I believe the Electronic Engine Control went into Soft Alternate for a moment. When on the ground it went back to Normal Mode. We eventually got a different Aircraft and took off for ZZZ3 with no other issues. [The Captain suggests] pitot covers for Routine Overnight Aircraft in all ZZZ4 locations as I believe this was caused by Mud Daubers building nests in the Pitot Tubes; and I also believe this aircraft had been sitting a few days in ZZZ5.
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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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