Takeoff warning sounded when dial a flap 24 degree used.

Attributes
ACN	166834
Time
Date	199101
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : ewr
State Reference	NJ
Environment
Flight Conditions	VMC
Light	Night
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 : captain oversight : pic
Qualification	pilot : atp pilot : commercial pilot : instrument pilot : cfi
Experience	flight time last 90 days : 120 flight time total : 10000 flight time type : 1200
ASRS Report	166834
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : rejected takeoff
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Taking off using 'dial-a-flap' setting of 24 degree. When throttles were advanced for takeoff, false 'slat' aural warning sounded. Rejected takeoff at less than 20 KTS. Taxied clear of runway and reset flap/slat handle and 'dial-a-flap' wheel. Subsequent takeoff was uneventful. This is an aggravating anomaly of the medium large transport when using flap setting of 24 degree for takeoff. Callback conversation with reporter revealed the following information. 24 degree flap is used when the aircraft is very light. Company is aware of the problem and is considering discontinuing the use of 24 degree. Reporter stated that when conditions warrant the use of 24 degree he has the first officer set 23 degree or very carefully position the selector to 24. The more normal flap setting of 15 degree is used for the heavier takeoff weights and is primarily based on second segment climb performance.

Original NASA ASRS Text

Title: TKOF WARNING SOUNDED WHEN DIAL A FLAP 24 DEGREE USED.

Narrative: TAKING OFF USING 'DIAL-A-FLAP' SETTING OF 24 DEG. WHEN THROTTLES WERE ADVANCED FOR TKOF, FALSE 'SLAT' AURAL WARNING SOUNDED. REJECTED TKOF AT LESS THAN 20 KTS. TAXIED CLR OF RWY AND RESET FLAP/SLAT HANDLE AND 'DIAL-A-FLAP' WHEEL. SUBSEQUENT TKOF WAS UNEVENTFUL. THIS IS AN AGGRAVATING ANOMALY OF THE MLG WHEN USING FLAP SETTING OF 24 DEG FOR TKOF. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. 24 DEG FLAP IS USED WHEN THE ACFT IS VERY LIGHT. COMPANY IS AWARE OF THE PROB AND IS CONSIDERING DISCONTINUING THE USE OF 24 DEG. RPTR STATED THAT WHEN CONDITIONS WARRANT THE USE OF 24 DEG HE HAS THE F/O SET 23 DEG OR VERY CAREFULLY POS THE SELECTOR TO 24. THE MORE NORMAL FLAP SETTING OF 15 DEG IS USED FOR THE HEAVIER TKOF WEIGHTS AND IS PRIMARILY BASED ON SEC SEGMENT CLB PERFORMANCE.

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.