Narrative:

We were approaching to land at ZZZ airport about 7 miles out I called, as flying pilot, flaps 15 (initial flap position for landing). The flaps moved to approximately 15 degree and we received a flap disagreement on the outboard flaps. We complied with the checklist and left the flaps at the first selected position (15 degree) flap disagreements are very common with the emb 120 and typically happen when flaps are selected to 25 degree or 45 degree. We elected to land flaps 15 degree and captain stated we had performance to land but upon landing and closer review this was a grey area. The runway analysis prohibits a zero flap landing at our weight but we were not at flaps 0 degree. Normal landing data provides data for only 25 degree and 45 degree flap lndgs. The checklist gives no guidance for partial flap landings. The checklist only states to 'apply the zero flap weight penalty if landing flaps zero.' there is no guidance for landing flaps 15 degree due to a malfunction. We elected to land due to the fact that we would have had to climb back to altitude to reach our dispatch and mx and then if we would have diverted we would have landed with well less than reserve fuel minimums. The landing was uneventful and reference speeds for 15 degree verses 25 degree only added about 10 knots to our approach airspeed. After landing, the malfunction cleared and after conferring with our mx control they stated not to write up the discrepancy since it cleared. The only question in my mind is the fact that there was no official landing data for a partial flap landing, only flap 0 degree which we were overweight for or 25 degree or 45 degree which we could not do because of malfunction. How do you know if a partial flap is legal? Does any aircraft have data for this? Callback conversation with reporter revealed the following information: the reporter stated that flap failure to extend beyond 15 degrees is a common failure on the embraer 120 and is most often not written by crews. The reporter said maintenance has a standard policy of advising the crews who experience trailing edge flap failure to check the flaps on the ground and if ok make no discrepancy logbook write-up. The reporter stated in the last three days two trailing edge flap failures occurred with one event with flaps full up. The reporter said the frequency of flap failures are such that the crew don't bother to write the report in the maintenance log. The reporter stated the flight operations manual needs revision to add aircraft and airport performance numbers for flaps 15 lndgs.

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Original NASA ASRS Text

Title: AN EMBRAER 120 ON APCH AT 2500 FT HAS TRAILING EDGE FLAP FAILURE AT 15 DEGS. OPS MANUAL HAS NO PERFORMANCE NUMBERS FOR THIS SETTING.

Narrative: WE WERE APCHING TO LAND AT ZZZ ARPT ABOUT 7 MILES OUT I CALLED, AS FLYING PLT, FLAPS 15 (INITIAL FLAP POSITION FOR LNDG). THE FLAPS MOVED TO APPROX 15 DEG AND WE RECEIVED A FLAP DISAGREEMENT ON THE OUTBOARD FLAPS. WE COMPLIED WITH THE CHKLIST AND LEFT THE FLAPS AT THE FIRST SELECTED POSITION (15 DEG) FLAP DISAGREEMENTS ARE VERY COMMON WITH THE EMB 120 AND TYPICALLY HAPPEN WHEN FLAPS ARE SELECTED TO 25 DEG OR 45 DEG. WE ELECTED TO LAND FLAPS 15 DEG AND CAPT STATED WE HAD PERFORMANCE TO LAND BUT UPON LNDG AND CLOSER REVIEW THIS WAS A GREY AREA. THE RWY ANALYSIS PROHIBITS A ZERO FLAP LNDG AT OUR WT BUT WE WERE NOT AT FLAPS 0 DEG. NORMAL LNDG DATA PROVIDES DATA FOR ONLY 25 DEG AND 45 DEG FLAP LNDGS. THE CHKLIST GIVES NO GUIDANCE FOR PARTIAL FLAP LANDINGS. THE CHKLIST ONLY STATES TO 'APPLY THE ZERO FLAP WT PENALTY IF LNDG FLAPS ZERO.' THERE IS NO GUIDANCE FOR LNDG FLAPS 15 DEG DUE TO A MALFUNCTION. WE ELECTED TO LAND DUE TO THE FACT THAT WE WOULD HAVE HAD TO CLB BACK TO ALTITUDE TO REACH OUR DISPATCH AND MX AND THEN IF WE WOULD HAVE DIVERTED WE WOULD HAVE LANDED WITH WELL LESS THAN RESERVE FUEL MINIMUMS. THE LNDG WAS UNEVENTFUL AND REF SPEEDS FOR 15 DEG VERSES 25 DEG ONLY ADDED ABOUT 10 KNOTS TO OUR APCH AIRSPEED. AFTER LNDG, THE MALFUNCTION CLRED AND AFTER CONFERRING WITH OUR MX CTL THEY STATED NOT TO WRITE UP THE DISCREPANCY SINCE IT CLRED. THE ONLY QUESTION IN MY MIND IS THE FACT THAT THERE WAS NO OFFICIAL LNDG DATA FOR A PARTIAL FLAP LNDG, ONLY FLAP 0 DEG WHICH WE WERE OVERWT FOR OR 25 DEG OR 45 DEG WHICH WE COULD NOT DO BECAUSE OF MALFUNCTION. HOW DO YOU KNOW IF A PARTIAL FLAP IS LEGAL? DOES ANY ACFT HAVE DATA FOR THIS? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT FLAP FAILURE TO EXTEND BEYOND 15 DEGS IS A COMMON FAILURE ON THE EMBRAER 120 AND IS MOST OFTEN NOT WRITTEN BY CREWS. THE RPTR SAID MAINT HAS A STANDARD POLICY OF ADVISING THE CREWS WHO EXPERIENCE TRAILING EDGE FLAP FAILURE TO CHECK THE FLAPS ON THE GND AND IF OK MAKE NO DISCREPANCY LOGBOOK WRITE-UP. THE RPTR STATED IN THE LAST THREE DAYS TWO TRAILING EDGE FLAP FAILURES OCCURRED WITH ONE EVENT WITH FLAPS FULL UP. THE RPTR SAID THE FREQ OF FLAP FAILURES ARE SUCH THAT THE CREW DON'T BOTHER TO WRITE THE RPT IN THE MAINT LOG. THE RPTR STATED THE FLT OPS MANUAL NEEDS REVISION TO ADD ACFT AND ARPT PERFORMANCE NUMBERS FOR FLAPS 15 LNDGS.

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.