B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Human Factors
We received a windshear alert during takeoff roll. Reported weather was a few clouds at 11;000 FT; greater than 6 miles visibility; temperature 15 C; winds 210 at 7 KTS. There were none of the usual meteorological conditions that would indicate that windshear might be a possibility. There were also no windshear advisories from the Tower or PIREPs indicating windshear. The takeoff roll was normal with no airspeed fluctuations. At between 90 KTS and 100 KTS we received an aural 'windshear; windshear' alert. Airspeed was still increasing normally. The windshear symbol appeared on the map display from the nose of the aircraft symbol radiating out from the 10 o'clock position to about the 11 o'clock position. I elected to continue the takeoff as airspeed was still increasing normally; there were no airspeed fluctuations; we were rapidly approaching the high speed regime and there were no other indications of windshear. The rest of the takeoff roll and climb out were normal. No airspeed fluctuations were noted. Approximately 10 to 15 sec after we became airborne the windshear alert went away. Tower handed us off to Departure Control and we cleaned up the aircraft and continued our climb. Leaving about 5;000 FT. MSL; I switched back to Tower to tell them about our alert. As I switched over; I heard the Tower Controller tell an arriving jet that there was a 'windshear alert directly over the runway with a 20 KTS loss but it's probably a false alarm because there is not a cloud in the sky.' Obviously the Tower Controller did not think the conditions were conducive for a windshear event. I then told Tower that we had also received a predictive wind shear alert on board during takeoff but had not encountered any actual windshear. The rest of the flight continued normally. My initial inclination after take off was to chalk up the on board windshear alert as a momentary malfunction of the predictive windshear system on the plane until I switched over to Tower and heard his report. Clearly something caused both of our systems to activate. You would not normally expect a wind shear hazard on a cloudless; clear; calm; 15 C morning at sunrise.
B737 Captain reported he got an internal wind shear alert on takeoff roll that he chose to ignore because conditions did not seem conducive to windshear; but after takeoff he heard the Tower issue a similar alert to an inbound flight.