Narrative:

While approaching the traffic pattern at key west international airport, I attempted to lower the landing gear. When the gear switch was put down, all lighted displays on the instrument panel went dark, as if the electrical system was short-circuited. The gear failed to go down and lock, as indicated by the lack of any green gear lights. I requested permission from the tower to depart the pattern and orbit outside the air traffic area. I circled for an hour attempting to lower the gear, following procedures in the pilot operating handbook, pulling the gear circuit breaker, resetting it, and operating the gear switch about 15 times. There was no response other than a shorting of the electrical system when the gear switch was put down. I then attempted to lower the gear by the emergency backup system. I followed the checklist, pulling the gear circuit breaker, applying flaps and slowing the airplane to recommended speed. The 2 main wheels indicated down and locked by 2 green lights. The nose gear did not indicate down. I requested permission to fly-by for visual inspection, and the tower reported that the nosewheel appeared not completely down and locked. I attempted to shake the gear down by maneuvering, but to no avail. After being cleared to land, I rolled the main wheels on, slowed the airplane and allowed the nose to settle. The nosewheel had failed to lock and the nose settled onto the runway, damaging the propeller and lower cowl. The problem appears to have been caused by a malfunction in both the landing gear power pack and the emergency extension system. The power pack had been overhauled 2 months earlier. I believe these system should be reviewed by the airframe maker, and appropriate cautions or remedial action taken. Callback conversation with reporter revealed the following: the owner pilot of this aircraft is 'an electronics and avionics type mechanic. The aircraft is a tb-20 trinidad built by aerospatiale. The landing gear is raised and held in the up position by a hydraulic system that is electrically driven. When the gear is up, limit switches turn off the electrical pump. The reporter believes that the switches were out of adjustment causing the pump to try to lift the gear when it was already up. The main gear, in the emergency operation, freefalls and is pushed down by the wind. The nose gear falls forward into the wind. It is assisted by 2 'gas rods.' at each 100 hour inspection, one of the gas rods must be disconnected and the other must be able to lock the nose gear in place. The reporter believes that the gas rods have finally worn out after 10 yrs of flight. This supposition is backed by having to replace the gas rods that assist in opening the gull wing passenger entrance doors. A service bulletin regarding the emergency landing gear operation has been issued and complied with. The local FSDO is aware of this incident. The reporter is now aware of the FAA aviation safety hot line.

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Original NASA ASRS Text

Title: A TB-20 TRINIDAD LANDED WITH ITS NOSE GEAR NOT DOWN.

Narrative: WHILE APCHING THE TFC PATTERN AT KEY WEST INTL ARPT, I ATTEMPTED TO LOWER THE LNDG GEAR. WHEN THE GEAR SWITCH WAS PUT DOWN, ALL LIGHTED DISPLAYS ON THE INST PANEL WENT DARK, AS IF THE ELECTRICAL SYS WAS SHORT-CIRCUITED. THE GEAR FAILED TO GO DOWN AND LOCK, AS INDICATED BY THE LACK OF ANY GREEN GEAR LIGHTS. I REQUESTED PERMISSION FROM THE TWR TO DEPART THE PATTERN AND ORBIT OUTSIDE THE ATA. I CIRCLED FOR AN HR ATTEMPTING TO LOWER THE GEAR, FOLLOWING PROCS IN THE PLT OPERATING HANDBOOK, PULLING THE GEAR CIRCUIT BREAKER, RESETTING IT, AND OPERATING THE GEAR SWITCH ABOUT 15 TIMES. THERE WAS NO RESPONSE OTHER THAN A SHORTING OF THE ELECTRICAL SYS WHEN THE GEAR SWITCH WAS PUT DOWN. I THEN ATTEMPTED TO LOWER THE GEAR BY THE EMER BACKUP SYS. I FOLLOWED THE CHKLIST, PULLING THE GEAR CIRCUIT BREAKER, APPLYING FLAPS AND SLOWING THE AIRPLANE TO RECOMMENDED SPD. THE 2 MAIN WHEELS INDICATED DOWN AND LOCKED BY 2 GREEN LIGHTS. THE NOSE GEAR DID NOT INDICATE DOWN. I REQUESTED PERMISSION TO FLY-BY FOR VISUAL INSPECTION, AND THE TWR RPTED THAT THE NOSEWHEEL APPEARED NOT COMPLETELY DOWN AND LOCKED. I ATTEMPTED TO SHAKE THE GEAR DOWN BY MANEUVERING, BUT TO NO AVAIL. AFTER BEING CLRED TO LAND, I ROLLED THE MAIN WHEELS ON, SLOWED THE AIRPLANE AND ALLOWED THE NOSE TO SETTLE. THE NOSEWHEEL HAD FAILED TO LOCK AND THE NOSE SETTLED ONTO THE RWY, DAMAGING THE PROP AND LOWER COWL. THE PROB APPEARS TO HAVE BEEN CAUSED BY A MALFUNCTION IN BOTH THE LNDG GEAR PWR PACK AND THE EMER EXTENSION SYS. THE PWR PACK HAD BEEN OVERHAULED 2 MONTHS EARLIER. I BELIEVE THESE SYS SHOULD BE REVIEWED BY THE AIRFRAME MAKER, AND APPROPRIATE CAUTIONS OR REMEDIAL ACTION TAKEN. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE OWNER PLT OF THIS ACFT IS 'AN ELECTRONICS AND AVIONICS TYPE MECH. THE ACFT IS A TB-20 TRINIDAD BUILT BY AEROSPATIALE. THE LNDG GEAR IS RAISED AND HELD IN THE UP POS BY A HYD SYS THAT IS ELECTRICALLY DRIVEN. WHEN THE GEAR IS UP, LIMIT SWITCHES TURN OFF THE ELECTRICAL PUMP. THE RPTR BELIEVES THAT THE SWITCHES WERE OUT OF ADJUSTMENT CAUSING THE PUMP TO TRY TO LIFT THE GEAR WHEN IT WAS ALREADY UP. THE MAIN GEAR, IN THE EMER OP, FREEFALLS AND IS PUSHED DOWN BY THE WIND. THE NOSE GEAR FALLS FORWARD INTO THE WIND. IT IS ASSISTED BY 2 'GAS RODS.' AT EACH 100 HR INSPECTION, ONE OF THE GAS RODS MUST BE DISCONNECTED AND THE OTHER MUST BE ABLE TO LOCK THE NOSE GEAR IN PLACE. THE RPTR BELIEVES THAT THE GAS RODS HAVE FINALLY WORN OUT AFTER 10 YRS OF FLT. THIS SUPPOSITION IS BACKED BY HAVING TO REPLACE THE GAS RODS THAT ASSIST IN OPENING THE GULL WING PAX ENTRANCE DOORS. A SVC BULLETIN REGARDING THE EMER LNDG GEAR OP HAS BEEN ISSUED AND COMPLIED WITH. THE LCL FSDO IS AWARE OF THIS INCIDENT. THE RPTR IS NOW AWARE OF THE FAA AVIATION SAFETY HOT LINE.

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.