Air carrier medium large transport flight crew makes high speed abort for takeoff flap configuration warning caused by flap slipping from flex flap 17 pt 4 degree position fixed detent 15 pt 0 degree position.

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Attributes
ACN	181319
Time
Date	199106
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : lga
State Reference	NY
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	climbout : takeoff other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : instrument pilot : atp pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 8000 flight time type : 5000
ASRS Report	181319
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 30000 flight time type : 2200
ASRS Report	181322
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : insufficient time
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On takeoff (lga runway 4) at about 120 KTS we received a 'flaps' warning call from flap warning system. Initial setting called for 17.4 degrees using dial-a-flap. It appears that the flap handle slipped from the 17.4 degree position to the 15 degree position. The takeoff was aborted. (No problems with abort). It's my feeling that the dial-a-flap detent on the medium large transport either becomes worn or somehow fails to hold the selected flap position when close to the fixed 15 degree flap detent. In this case, with flaps set (and checked with power lever advancement numerous times) to 17.4 degree and on a rough surface runway as lga runway 4, that the flaps slipped due to constant jarring from takeoff roll and being close to the fixed 15 degree detent. Supplemental information from acn 181322. Problem was caused by flex takeoff flap apparently slipping out of flex detent thereby not agreeing with takeoff condition computer. The solution is either using fixed flaps for takeoff or modifying the flex flap system to be more reliable.

Original NASA ASRS Text

Title: ACR MLG FLC MAKES HIGH SPEED ABORT FOR TKOF FLAP CONFIGURATION WARNING CAUSED BY FLAP SLIPPING FROM FLEX FLAP 17 PT 4 DEG POSITION FIXED DETENT 15 PT 0 DEG POSITION.

Narrative: ON TKOF (LGA RWY 4) AT ABOUT 120 KTS WE RECEIVED A 'FLAPS' WARNING CALL FROM FLAP WARNING SYS. INITIAL SETTING CALLED FOR 17.4 DEGS USING DIAL-A-FLAP. IT APPEARS THAT THE FLAP HANDLE SLIPPED FROM THE 17.4 DEG POS TO THE 15 DEG POS. THE TKOF WAS ABORTED. (NO PROBS WITH ABORT). IT'S MY FEELING THAT THE DIAL-A-FLAP DETENT ON THE MLG EITHER BECOMES WORN OR SOMEHOW FAILS TO HOLD THE SELECTED FLAP POS WHEN CLOSE TO THE FIXED 15 DEG FLAP DETENT. IN THIS CASE, WITH FLAPS SET (AND CHKED WITH PWR LEVER ADVANCEMENT NUMEROUS TIMES) TO 17.4 DEG AND ON A ROUGH SURFACE RWY AS LGA RWY 4, THAT THE FLAPS SLIPPED DUE TO CONSTANT JARRING FROM TKOF ROLL AND BEING CLOSE TO THE FIXED 15 DEG DETENT. SUPPLEMENTAL INFO FROM ACN 181322. PROB WAS CAUSED BY FLEX TKOF FLAP APPARENTLY SLIPPING OUT OF FLEX DETENT THEREBY NOT AGREEING WITH TKOF CONDITION COMPUTER. THE SOLUTION IS EITHER USING FIXED FLAPS FOR TKOF OR MODIFYING THE FLEX FLAP SYS TO BE MORE RELIABLE.

Data retrieved from NASA's ASRS site as of July 2007 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.