A B737-300's flap handle slipped out of the up detent and extended flaps and slats to the flaps 1 po...

Narrative:

The flight started in ZZZ where we discussed the MEL of 'flap transit' light while on the ground. The writeup had been deferred several days prior. While in cruise at fl 340 (my leg) we suddenly heard a very distinctive rumble at which time the captain states the leading edge devices just deployed. We both looked and realized that the flaps were at one. I did not happen to look at the handle; just the indicator at this point. He stated; 'my aircraft;' and took over the plane. At this point I reached for the checklist and went to the 'le transit light inflight' checklist since there is not really a flaps 1 at cruise checklist. The captain immediately began slowing and hoping to not exceed flap speed. The checklist calls for us to descend to 20;000' and slow to 230 kts before attempting retraction. Somewhere in the descent is where I also saw that the flap handle was at one. We called maintenance and dispatch and the captain asked maintenance if we can retract the flaps. We then retracted and they went back to normal. At this point we decided to climb back up to fl 340 and see what our burn to destination or diversion will need to be. After talking to dispatch the captain decided that he is more comfortable diverting to an enroute airport to have the flaps inspected. He turned the plane back over to me and we landed at the enroute airport without incident. While the flaps were at zero during climb and beginning of cruise; the flap handle may have been not securely in the detent. In the past I have always firmly tapped the handle into place when going to flaps zero. I will continue with this policy and check even if I am the flying pilot as in this case. My first thought was the MEL when the event happened; which can sometimes lead us in the wrong direction if we do not take time to analyze the situation.

Original NASA ASRS Text

Title: A B737-300's Flap handle slipped out of the up detent and extended Flaps and Slats to the Flaps 1 position at FL340. The flight crew diverted for a Flap inspection.

Narrative: The flight started in ZZZ where we discussed the MEL of 'FLAP TRANSIT' light while on the ground. The writeup had been deferred several days prior. While in cruise at FL 340 (my leg) we suddenly heard a very distinctive rumble at which time the Captain states the Leading Edge devices just deployed. We both looked and realized that the Flaps were at one. I did not happen to look at the handle; just the indicator at this point. He stated; 'My aircraft;' and took over the plane. At this point I reached for the checklist and went to the 'LE TRANSIT Light InFlight' checklist since there is not really a Flaps 1 at Cruise checklist. The Captain immediately began slowing and hoping to not exceed Flap speed. The checklist calls for us to descend to 20;000' and slow to 230 kts before attempting retraction. Somewhere in the descent is where I also saw that the Flap handle was at one. We called Maintenance and Dispatch and the Captain asked Maintenance if we can retract the Flaps. We then retracted and they went back to normal. At this point we decided to climb back up to FL 340 and see what our burn to destination or diversion will need to be. After talking to Dispatch the Captain decided that he is more comfortable diverting to an enroute airport to have the Flaps inspected. He turned the plane back over to me and we landed at the enroute airport without incident. While the Flaps were at ZERO during climb and beginning of cruise; the Flap handle may have been not securely in the detent. In the past I have always firmly tapped the handle into place when going to Flaps ZERO. I will continue with this policy and check even if I am the Flying Pilot as in this case. My first thought was the MEL when the event happened; which can sometimes lead us in the wrong direction if we do not take time to analyze the situation.

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.

Attributes
ACN	845113
Time
Date	200907
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Flap/Slat Control System
Person 1
Function	First Officer Pilot Flying
Experience	Flight Crew Last 90 Days 143
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Speed All Types

A B737-300's flap handle slipped out of the up detent and extended flaps and slats to the flaps 1 position at FL340. The flight crew diverted for a flap inspection.