Narrative:

At 500' during approach to land the captain requested stand IFR calls. I made the standard calls as our before landing check was complete (flaps were set to 50 degrees). After I called 'decision height--runway in sight,' the aircraft began to rapidly sink. I called 'wind ,' as I noticed that there was no real significant loss of airspeed on final. The captain continued the approach and landed the aircraft with a very nose high attitude and high power setting. Several aircraft were on approach behind us so the captain reported a 20 KT windshear over the runway threshold. Accordingly, the tower issued windshear advisories on ATIS. After we parked at the gate the captain admitted that this had happened to him several days earlier at another airport. I verified that I had visually confirmed the flaps at 50 degrees as I always do before calling 'before landing check complete.' the captain then admitted that he must have accidentally hit the flap switch while manually trimming the aircraft to land. The captain called the tower and reported that 'one of us,' must've hit the flap switch and we did not land with full flaps. We are not approved for any other than flap 50 degrees (full) lndgs. Callback conversation with reporter revealed the following: on this model light transport, the flap switch is a spring loaded toggle type with 3 position--up, 20 degrees for takeoff and full down, 50 degrees for landing. The switch is located on the aft center pedestal right next to the trim controls for the aileron and rudder and very easy to hit when adjusting the trim. Reporter feels it is a bad location and the switch is a bad design as it does not have a very positive detent and is cheaply constructed.

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Original NASA ASRS Text

Title: ACR LTT PF HIT FLAP SWITCH ON APCH CAUSING FLAPS TO RETRACT TO TKOF POSITION RESULTING IN ILLEGAL LNDG.

Narrative: AT 500' DURING APCH TO LAND THE CAPT REQUESTED STAND IFR CALLS. I MADE THE STANDARD CALLS AS OUR BEFORE LNDG CHK WAS COMPLETE (FLAPS WERE SET TO 50 DEGS). AFTER I CALLED 'DECISION HEIGHT--RWY IN SIGHT,' THE ACFT BEGAN TO RAPIDLY SINK. I CALLED 'WIND ,' AS I NOTICED THAT THERE WAS NO REAL SIGNIFICANT LOSS OF AIRSPD ON FINAL. THE CAPT CONTINUED THE APCH AND LANDED THE ACFT WITH A VERY NOSE HIGH ATTITUDE AND HIGH PWR SETTING. SEVERAL ACFT WERE ON APCH BEHIND US SO THE CAPT RPTED A 20 KT WINDSHEAR OVER THE RWY THRESHOLD. ACCORDINGLY, THE TWR ISSUED WINDSHEAR ADVISORIES ON ATIS. AFTER WE PARKED AT THE GATE THE CAPT ADMITTED THAT THIS HAD HAPPENED TO HIM SEVERAL DAYS EARLIER AT ANOTHER ARPT. I VERIFIED THAT I HAD VISUALLY CONFIRMED THE FLAPS AT 50 DEGS AS I ALWAYS DO BEFORE CALLING 'BEFORE LNDG CHK COMPLETE.' THE CAPT THEN ADMITTED THAT HE MUST HAVE ACCIDENTALLY HIT THE FLAP SWITCH WHILE MANUALLY TRIMMING THE ACFT TO LAND. THE CAPT CALLED THE TWR AND RPTED THAT 'ONE OF US,' MUST'VE HIT THE FLAP SWITCH AND WE DID NOT LAND WITH FULL FLAPS. WE ARE NOT APPROVED FOR ANY OTHER THAN FLAP 50 DEGS (FULL) LNDGS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: ON THIS MODEL LTT, THE FLAP SWITCH IS A SPRING LOADED TOGGLE TYPE WITH 3 POS--UP, 20 DEGS FOR TKOF AND FULL DOWN, 50 DEGS FOR LNDG. THE SWITCH IS LOCATED ON THE AFT CENTER PEDESTAL RIGHT NEXT TO THE TRIM CONTROLS FOR THE AILERON AND RUDDER AND VERY EASY TO HIT WHEN ADJUSTING THE TRIM. RPTR FEELS IT IS A BAD LOCATION AND THE SWITCH IS A BAD DESIGN AS IT DOES NOT HAVE A VERY POSITIVE DETENT AND IS CHEAPLY CONSTRUCTED.

Data retrieved from NASA's ASRS site as of August 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.