Narrative:

We were cleared to takeoff on runway 20L. Upon aligning with the runway, I gave the aircraft to my first officer, who ran up the engines toward takeoff thrust. As he advanced the power levers, the takeoff warning horn sounded, signaling something was not properly set for takeoff. Before reaching 20 KTS I assumed control of the aircraft, we taxied off the runway after telling the tower we would need a few mins to sort things out. I called for flaps 5 degrees, as we were at flaps 1 degree, I ran the power levers up, and the horn remained silent. It then occurred to both of us that we were in a 500 series aircraft where only flaps 5 degrees is an acceptable takeoff setting. Ouch! Originally we were to get a 200 series aircraft, and I had prepared a brief to be done with whoever my first officer might be. It included a discussion of when to use flaps 1 degree. That set the stage for first officer to errantly compute performance figures for that setting. The only problem is that there are no figures in the performance manual for flaps 1 degree for a 500 series aircraft. Nonetheless, in first officer mind's eye, he saw flaps 1 degree numbers (which actually were correct flaps 5 degree numbers) and set up the flaps 5 degrees takeoff V speed numbers. When I called for flaps after the after start checklist was completed, he set flaps 1 degree as per my brief. (Apparently, we were still both stuck in the flaps 1 degree mode as per my preflight brief.) we reconfirmed 'flaps 1 degree, green light, detent' during the pretkof checklist as we proceeded toward the runway. After exiting the runway, I stopped the aircraft, and made an announcement that we had a reading that we found unacceptable, that we had corrected the problem, that there was no need for alarm, and that we were going to continue the flight. After leaving 10000 ft, I called the 'a' flight attendant forward to ask about the atmosphere among the passenger when we pulled power, left the runway, made the announcement, and proceeded on our flight. He said that there was no apprehension that he could detect, and that someone actually made a small joke about the incident after the announcement, that there were a few laughs, and things were nominal. The rest of the flight proceeded normally. First officer and I reviewed the incident and came up with these conclusions: 1) I had predisposed us to the incident with my preflight briefing, 2) first officer had somehow, in his mind's eye, read all the performance figures as being for flaps 1 degree, and so set that setting for takeoff despite there being no flaps 1 degree performance data in the performance manual, 3) the absence of the old stickers in the 500 series aircraft signifying that flaps 1 degree was not an acceptable setting was unwise, and 4) that it would be prudent for the captain to run the power rapidly levers forward, and then back to the idle sometime prior to taking the runway to ensure that all settings were acceptable for takeoff as far as the takeoff warning horn was concerned.

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Original NASA ASRS Text

Title: B737-500 HAD COMPUTED TKOF NUMBERS USING 1 DEG FLAPS. NOT AUTH ON THIS ACFT. AS THE FO, PF, ADVANCED THE THRUST LEVERS GOT A TKOF WARNING HORN AND ABORTED THE TKOF. SET FLAPS PROPERLY AT 5 DEGS AND WAS CLRED FOR ANOTHER TKOF.

Narrative: WE WERE CLRED TO TKOF ON RWY 20L. UPON ALIGNING WITH THE RWY, I GAVE THE ACFT TO MY FO, WHO RAN UP THE ENGS TOWARD TKOF THRUST. AS HE ADVANCED THE PWR LEVERS, THE TKOF WARNING HORN SOUNDED, SIGNALING SOMETHING WAS NOT PROPERLY SET FOR TKOF. BEFORE REACHING 20 KTS I ASSUMED CTL OF THE ACFT, WE TAXIED OFF THE RWY AFTER TELLING THE TWR WE WOULD NEED A FEW MINS TO SORT THINGS OUT. I CALLED FOR FLAPS 5 DEGS, AS WE WERE AT FLAPS 1 DEG, I RAN THE PWR LEVERS UP, AND THE HORN REMAINED SILENT. IT THEN OCCURRED TO BOTH OF US THAT WE WERE IN A 500 SERIES ACFT WHERE ONLY FLAPS 5 DEGS IS AN ACCEPTABLE TKOF SETTING. OUCH! ORIGINALLY WE WERE TO GET A 200 SERIES ACFT, AND I HAD PREPARED A BRIEF TO BE DONE WITH WHOEVER MY FO MIGHT BE. IT INCLUDED A DISCUSSION OF WHEN TO USE FLAPS 1 DEG. THAT SET THE STAGE FOR FO TO ERRANTLY COMPUTE PERFORMANCE FIGURES FOR THAT SETTING. THE ONLY PROB IS THAT THERE ARE NO FIGURES IN THE PERFORMANCE MANUAL FOR FLAPS 1 DEG FOR A 500 SERIES ACFT. NONETHELESS, IN FO MIND'S EYE, HE SAW FLAPS 1 DEG NUMBERS (WHICH ACTUALLY WERE CORRECT FLAPS 5 DEG NUMBERS) AND SET UP THE FLAPS 5 DEGS TKOF V SPD NUMBERS. WHEN I CALLED FOR FLAPS AFTER THE AFTER START CHKLIST WAS COMPLETED, HE SET FLAPS 1 DEG AS PER MY BRIEF. (APPARENTLY, WE WERE STILL BOTH STUCK IN THE FLAPS 1 DEG MODE AS PER MY PREFLT BRIEF.) WE RECONFIRMED 'FLAPS 1 DEG, GREEN LIGHT, DETENT' DURING THE PRETKOF CHKLIST AS WE PROCEEDED TOWARD THE RWY. AFTER EXITING THE RWY, I STOPPED THE ACFT, AND MADE AN ANNOUNCEMENT THAT WE HAD A READING THAT WE FOUND UNACCEPTABLE, THAT WE HAD CORRECTED THE PROB, THAT THERE WAS NO NEED FOR ALARM, AND THAT WE WERE GOING TO CONTINUE THE FLT. AFTER LEAVING 10000 FT, I CALLED THE 'A' FLT ATTENDANT FORWARD TO ASK ABOUT THE ATMOSPHERE AMONG THE PAX WHEN WE PULLED PWR, LEFT THE RWY, MADE THE ANNOUNCEMENT, AND PROCEEDED ON OUR FLT. HE SAID THAT THERE WAS NO APPREHENSION THAT HE COULD DETECT, AND THAT SOMEONE ACTUALLY MADE A SMALL JOKE ABOUT THE INCIDENT AFTER THE ANNOUNCEMENT, THAT THERE WERE A FEW LAUGHS, AND THINGS WERE NOMINAL. THE REST OF THE FLT PROCEEDED NORMALLY. FO AND I REVIEWED THE INCIDENT AND CAME UP WITH THESE CONCLUSIONS: 1) I HAD PREDISPOSED US TO THE INCIDENT WITH MY PREFLT BRIEFING, 2) FO HAD SOMEHOW, IN HIS MIND'S EYE, READ ALL THE PERFORMANCE FIGURES AS BEING FOR FLAPS 1 DEG, AND SO SET THAT SETTING FOR TKOF DESPITE THERE BEING NO FLAPS 1 DEG PERFORMANCE DATA IN THE PERFORMANCE MANUAL, 3) THE ABSENCE OF THE OLD STICKERS IN THE 500 SERIES ACFT SIGNIFYING THAT FLAPS 1 DEG WAS NOT AN ACCEPTABLE SETTING WAS UNWISE, AND 4) THAT IT WOULD BE PRUDENT FOR THE CAPT TO RUN THE PWR RAPIDLY LEVERS FORWARD, AND THEN BACK TO THE IDLE SOMETIME PRIOR TO TAKING THE RWY TO ENSURE THAT ALL SETTINGS WERE ACCEPTABLE FOR TKOF AS FAR AS THE TKOF WARNING HORN WAS CONCERNED.

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.