B737 flight crew reported a flap system malfunction during initial climbout resulting in a diversion...

Attributes
ACN	1543797
Time
Date	201805
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	IMC
Light	Dawn
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Flap Control (Trailing & Leading Edge)
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 225 Flight Crew Type 1029
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 7551
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

After a normal flaps 5 takeoff and noise abatement climbout from ZZZ; when the flaps were retracted the flaps moved up to approximately 3.0 degrees on the left and 4.5 degrees on the right side and locked. After advising ATC of the problem and stating that we needed 220 knots and below FL200 we entered the checklist. It directed us to use the flaps alternate system to put the flaps down to 15 degrees for landing. [Advised ATC] of flight control malfunction. Once the checklist was complete; ATC; dispatch; the flight attendants and passengers were advised of our intention to divert to ZZZ1. ATC vectored us to a straight in approach for landing. Once clear of the runway the fire/crash crew inspected the airplane and released us to the gate.the flap speed; altitude and G limits were not exceeded; there was no uncommanded roll and the landing was not overweight. The only problem was in deciding the correct checklist to use. Since both checklists and initial conditions weren't completely correct we had to slow down and read them both fully. This took about 4-6 minutes extra between passenger/flight attendant/dispatch/ATC vector calls etc. Once the correct checklist was entered (based on no uncommanded roll) things went smoothly; approach speeds computed; flaps extended and a flaps 15 landing performed.

Original NASA ASRS Text

Title: B737 flight crew reported a flap system malfunction during initial climbout resulting in a diversion.

Narrative: After a normal flaps 5 takeoff and noise abatement climbout from ZZZ; when the flaps were retracted the flaps moved up to approximately 3.0 degrees on the left and 4.5 degrees on the right side and locked. After advising ATC of the problem and stating that we needed 220 knots and below FL200 we entered the checklist. It directed us to use the flaps alternate system to put the flaps down to 15 degrees for landing. [Advised ATC] of flight control malfunction. Once the checklist was complete; ATC; dispatch; the flight attendants and passengers were advised of our intention to divert to ZZZ1. ATC vectored us to a straight in approach for landing. Once clear of the runway the Fire/Crash Crew inspected the airplane and released us to the gate.The flap speed; altitude and G limits were not exceeded; there was no uncommanded roll and the landing was not overweight. The only problem was in deciding the correct checklist to use. Since both checklists and initial conditions weren't completely correct we had to slow down and read them both fully. This took about 4-6 minutes extra between passenger/Flight Attendant/Dispatch/ATC vector calls etc. Once the correct checklist was entered (based on no uncommanded roll) things went smoothly; approach speeds computed; flaps extended and a flaps 15 landing performed.

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.