Date: 201512
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Turbulence; Windshear; 6
Light: Night
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach; Initial Approach
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Confusion; Situational Awareness; Workload; Training / Qualification
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: Pre-flight
Result: Flight Crew Became Reoriented
Contributing factors: Chart Or Publication; Human Factors; Procedure; Weather
Primary problem: Procedure

Narrative: When on final to runway XX; tower reported winds 190/40G60 and cleared us to land.  Configuration at that time was gear down and flaps 20.  Up to that point and on descent from FL290; the autopilot had tremendous difficulty in controlling the aircraft due to the turbulence.  It could not find and capture the localizer due to the 65 knots of cross wind at altitude.  I elected to hand fly the aircraft to final and reengaged the autopilot.  I called for the flaps 1 and flaps 5 to be extended; called for gear down and then flaps 20.  I set the correct speed for flaps 20.  The aircraft was having an extremely difficult time trying to control the aircraft accurately approaching the final approach fix.  Speed was 20-25 knots above the selected speed.  I disconnected the autopilot and found it impossible to maintain consistent wings level and the proper pitch attitude to maintain glide path.  All parameters were fluid and temporary.  I discussed briefly with the First Officer (FO) the possibility of landing with flaps 20 due to my concern with controlling the aircraft attitude in view of the 40 gusting to 60 knots of wind; even thought it was only 30 degrees from runway heading.  After discussing the merits of a flaps 20 landing; we added 20 knots to the flaps 20 ref speed (125 knots for our weight) and selected 145 as our reference.  I also instructed the FO to select the flap override switch to 'override' to eliminate the nuisance flap/terrain call.  Other than the gusting winds and being very difficult to control; the remaining portion of the approach to touchdown was; all things considered; uneventful and uncomfortable.  It wasn't until I was in the hotel room that I decided to look at the 757 AOM to determine if my 'procedures' were in fact compatible with the 757; as they were with other aircraft I've flown.  I cannot find any provision in the AOM that permits or prohibits landing with flaps 20 in extremely strong and gusty winds.  I apparently; and inadvertently; landed in a flap configuration contrary to 757 AOM procedures.  Next time in this situation (for which I don't recall ever training to; wind 40G60) I will use the full 30 degree flap setting; or if it becomes uncontrollable; I will divert.




Synopsis: A B757-200 Captain made the decision to land Flaps 20 with reported winds of 190/40G60. Later; he realized the Aircraft Operating Manual permitted Flaps 20 landings only in specific conditions and winds were apparently not included.