2022-02 · NASA ASRS report 1876809
Air carrier crew reported a GPWS Predictive Windshear Warning as they started the takeoff roll even though there was no adverse weather. The pilots rejected the takeoff and returned to the gate where the aircraft systems were checked and reset by maintenance.
After an uneventful brief; pushback; startup; and taxi; we were cleared for takeoff on Runway 9R; intersection BB; at O'Hare (ORD). I was the pilot flying. The weather was perfect. No clouds; no precipitation; light winds; dry runway; and light takeoff weight (362K pounds). I was well rested and not fatigued at all. After advancing the throttles and handing them off to the Captain; everything was fine. Between 80 and 100 knots; a Red Windshear warning appeared on the ND (Navigation Display) along with an aural Windshear warning. There was NO associated pie-shaped wedge on the display to indicate where the windshear was. There was only a very narrow band about 50 degrees left of the nose from the triangle at the center of the display extending radially outward all the way to the outside of the ND. This band was only a degree or two wide and seemed to be a very clearly erroneous; spurious indication. Given the perfect weather; a windshear indication was completely unexpected and the unusual display caused confusion. Within a second or two; the Captain clearly stated 'I've got it' and initiated rejected takeoff procedures which were uneventful. After clearing the runway and accomplishing all applicable checklists; we contacted Maintenance; who directed us to return to the gate; which we did.
On takeoff from Runway 9R/BB; we received a Windshear Warning at approximately 85-90 KIAS. The First Officer was performing the takeoff. At approximately 95 KIAS; I called out 'Reject; I have the aircraft'; and we performed the rejected takeoff procedure. RTO (Rejected Takeoff) autobrakes engaged; the speed brakes deployed and reverse was used. The aircraft decelerated quickly. We advised Tower and taxied clear of the runway where we conducted the Rejected Takeoff Checklist. We advised the flight attendants and the passengers of our status. We contacted Dispatch and Maintenance Control which led us to return to the gate. Upon arrival we wrote up the RTO and what we believed was an erroneous Windshear warning due to the atmospheric conditions at the time of our takeoff. Maintenance inspected the aircraft for the RTO. Additionally; they checked the warning systems for proper operation and basically reset the warning systems to help correct any potential software issues; as I understand it. The aircraft was refueled and we coordinated with Dispatch for the subsequent departure. The next takeoff was normal and the flight to ZZZ was completed without further issue.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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