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B737 captain questions takeoff performance calculations which require flaps 1 in windshear conditions and the flight manual which indicates that flaps 5 should be used.
| Attributes | |
| ACN | 979874 |
| Time | |
| Date | 201111 |
| Local Time Of Day | 1201-1800 |
| Place | |
| Locale Reference | DTW.Airport |
| State Reference | MI |
| Environment | |
| Flight Conditions | VMC |
| Light | Daylight |
| Aircraft 1 | |
| Make Model Name | B737-700 |
| Operating Under FAR Part | Part 121 |
| Flight Phase | Parked |
| Person 1 | |
| Function | Captain |
| Qualification | Flight Crew Air Transport Pilot (ATP) |
| Experience | Flight Crew Last 90 Days 173 Flight Crew Type 9600 |
| Events | |
| Anomaly | Deviation - Procedural Published Material / Policy |
Narrative:
I believe there may be a deficiency in the takeoff performance calculation as it relates to optimum flaps selection when windshear is also selected. We departed dtw on runway 22L last week with gusty winds and windshear reported on the ATIS. The first office selected 'windshear' on the weather portion of the calculation in addition to 'optimum flaps'. The takeoff output page gave us revised speeds; max thrust; and flaps 1. We departed without any issues; but the flap setting seemed peculiar to me. I later reviewed the precautionary takeoff profile (fom) and windshear sections. The fom indicates that windshear/precautionary takeoffs should be performed with flaps 5 unless different flaps are required. I thought this different flap requirement would only be more than 5; not less. I am unsure if the flap setting used for our windshear departure was the correct one as it seemingly goes against the recommendations in the fom.
Original NASA ASRS Text
Title: B737 Captain questions takeoff performance calculations which require flaps 1 in windshear conditions and the Flight Manual which indicates that flaps 5 should be used.
Narrative: I believe there may be a deficiency in the takeoff performance calculation as it relates to Optimum Flaps selection when windshear is also selected. We departed DTW on Runway 22L last week with gusty winds and windshear reported on the ATIS. The First Office selected 'Windshear' on the weather portion of the calculation in addition to 'Optimum Flaps'. The Takeoff Output page gave us revised speeds; max thrust; and flaps 1. We departed without any issues; but the flap setting seemed peculiar to me. I later reviewed the Precautionary Takeoff Profile (FOM) and windshear sections. The FOM indicates that windshear/precautionary takeoffs should be performed with flaps 5 unless different flaps are required. I thought this different flap requirement would only be more than 5; not less. I am unsure if the flap setting used for our windshear departure was the correct one as it seemingly goes against the recommendations in the FOM.
Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.