Accident Boeing 727-222 N7640U, Thursday 31 May 1984
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Date:Thursday 31 May 1984
Type:Silhouette image of generic B722 model; specific model in this crash may look slightly different    
Boeing 727-222
Owner/operator:United Airlines
Registration: N7640U
MSN: 19913/672
Year of manufacture:1968
Engine model:Pratt & Whitney JT8D-7B
Fatalities:Fatalities: 0 / Occupants: 105
Other fatalities:0
Aircraft damage: Substantial, repaired
Location:Denver-Stapleton International Airport, CO (DEN) -   United States of America
Phase: Take off
Nature:Passenger - Scheduled
Departure airport:Denver-Stapleton International Airport, CO (DEN/KDEN)
Destination airport:Las Vegas-McCarran International Airport, NV (LAS/KLAS)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Before takeoff, the crew of flight UA663 noted cumulus clouds and virga in the area. At 13:27, a de Havilland Canada DHC-7 crew reported a 25 kt loss of airspeed, but several other aircraft then took off without reporting a problem. Due to radio congestion, the captain did not query other aircrews, but decided to climb out at V2 plus 20. when the controller cleared US663 for takeoff, he advised the crew of numerous wind shears in 3 quadrants, but used incorrect terminology in issuing the wind shear alert. During takeoff, the aircraft struck an ILS localizer antenna, 1074 ft from the departure end of the runway, and damaged the lower fuselage. When unable to pressurize the aircraft, the crew returned to the airport and landed.
An investigation revealed the aircraft encountered wind shear from microburst activity which reached its greatest activity as US663 was taking off. The wind sheared from an 8 kt headwind to 40 to 56 kts over a 44 second period. The crew noted a hesitation while accelerating through 120 kts, then at or beyond Vr speed of approx. 141 kts, the aircraft momentarily lost 20 kts.

Probable Cause:
weather condition..windshear

Contributing Factors:
object..approach light/navaid
weather condition..rain
weather condition..high wind
weather condition..gusts
weather condition..unfavorable wind
radio communications..excessive
weather evaluation..inaccurate..pilot in command
information unclear..atc personnel(lcl/gnd/clnc)

Accident investigation:
Investigating agency: NTSB
Report number: DCA84AA025
Status: Investigation completed
Download report: Final report




Revision history:


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