Air carrier flight crew reported receiving a flap setting warning horn during initial power push for...

Attributes
ACN	1740738
Time
Date	202004
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZZ.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Events
Anomaly	Deviation - Procedural Published Material / Policy Ground Event / Encounter Other / Unknown

Narrative:

During the flight preflight; I missed resetting the flap selector to 10 degrees; as is my normal practice. During taxi out and completing the before takeoff checklist; the challenge question was asked 'flaps 10;' and due to expectation bias; and monitoring an aircraft back taxiing on the runway; I saw and confirmed 10 degrees of flaps; instead of the 15 degrees actually dialed in. When tower cleared us for takeoff I advanced the throttles; and the aircraft horn sounded due to the incorrect flap setting; I pulled the throttles to idle at approximately 5 knots applied brakes; then we reset the flaps to 10 degrees; and after confirming the correct configuration continued the takeoff.2nd leg of the day; a day after an oceanic crossing; followed by isolating in the hotel. This accompanied by the covid-19 restrictions caused broken sleep periods. While I felt fine; the fact that I was only getting 3 1/2 to 4 hours of sleep in blocks; coupled with the circadian disruptions did not help.better attention to detail.

Original NASA ASRS Text

Title: Air carrier flight crew reported receiving a flap setting warning horn during initial power push for takeoff. The Captain cited lack of sleep as a contributing factor.

Narrative: During the flight preflight; I missed resetting the flap selector to 10 degrees; as is my normal practice. During taxi out and completing the before takeoff checklist; the challenge question was asked 'Flaps 10;' and due to expectation bias; and monitoring an aircraft back taxiing on the runway; I saw and confirmed 10 degrees of flaps; instead of the 15 degrees actually dialed in. When Tower cleared us for takeoff I advanced the throttles; and the aircraft horn sounded due to the incorrect flap setting; I pulled the throttles to idle at approximately 5 knots applied brakes; then we reset the flaps to 10 degrees; and after confirming the correct configuration continued the takeoff.2nd leg of the day; a day after an oceanic crossing; followed by isolating in the hotel. This accompanied by the COVID-19 restrictions caused broken sleep periods. While I felt fine; the fact that I was only getting 3 1/2 to 4 hours of sleep in blocks; coupled with the circadian disruptions did not help.Better attention to detail.

Data retrieved from NASA's ASRS site 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.

Air carrier flight crew reported receiving a flap setting warning horn during initial power push for takeoff. The captain cited lack of sleep as a contributing factor.