Fort Wayne, IN, USA
N688TM
Twin Commander Acft. Corp. 680V
The airplane sustained substantial damage when a main landing gear failed to fully extend during landing. The pilot could not get a gear down and locked indication at his destination and returned to the departure airport. Troubleshooting efforts were unsuccessful in getting the main gear extended and a landing with the main gear not fully extended was performed at the departure airport. On-scene and post accident examinations could not duplicate or determine the malfunction.
HISTORY OF FLIGHT On February 11, 2005, about 1350 eastern standard time, a Twin Commander Aircraft Corporation 680V, N688TM, piloted by a commercial pilot, sustained substantial damage when a main landing gear was unable to extend fully during a landing at the Fort Wayne International Airport (FWA), near Fort Wayne, Indiana. The pilot declared an emergency due to an unsafe gear indication prior to the landing. The flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. An instrument flight plan was on file and activated. The pilot and two passengers reported no injuries. The flight originated from FWA about 1110 and was destined for Peoria, Illinois. The pilot's accident report stated: On the day of February 2-11-05, I attained [a] weather briefing and filed [an] IFR flight plan on GTE duats for a trip to Peoria, IL. On or about 1015am, I arrived at the Ft. Wayne International airport to prepare for the flight. The aircraft was called out for a 1030am pull out from the hangar. I made coffee and put ice onboard. I also pulled the intake covers and tail gust lock, which was followed by my walk around preflight, nothing flagged me. At about 1110am I departed Fort Wayne and did the normal check list checks [and] procedures. We departed and everything was normal, gear and flap retraction was normal, no indications. After about 80 miles from the destination I had noticed the hydraulic pressure gauge was about 6-700 psi and flickering. I first thought about gauge error or malfunction, I noticed the "red" low pressure light was "not" on and I continued to monitor the situation. About 30 miles from destination the "red" low pressure light came on, at that time I began planning for a "no" hydraulic fluid situation. I also looked near my feet to see if there was hydraulic fluid on the floor, nothing noticed. (It should be mentioned here that this airplane had the regulator rebuilt about 5-6 months ago. The regulator was actually "pumping" hydraulic fluid overboard from the left engine. It happened 2 times and both times the gear was extended successfully and all three green lights appeared. Mercury maintenance did repairs and put the aircraft back into service.) Before I approached the Peoria airport, I went through the manual to verify procedures for this situation. I slowed the aircraft down to 120kts [knots] and put the gear down. I was aware in the manual that it would take up to 3 min for full gear extension. 5-10 min passed and the only green light on the gear indicator was for the nose gear. The mains came down about 95-97% but not to the point of down and locked with the green light illumination. I attempted to recycle the gear, they came up a few inches then returned to the near down position, still no main gear green lights. I talked to Peoria tower and advised them that I wanted to verify a possible situation and that I'd remain about 8- 10 miles from the airport. At that time I decided to cancel IFR and handle this situation in VFR conditions, while still in radio contact with the tower. About that time I had talked with maintenance at Byerly Aviation in Peoria, IL on the unicom. I talked with a mechanic and did a few maneuvers to try and force the gear into the green position. Climbs, descents, abrupt control and rudder movements were performed. I also reduced to a near stall speed and again, no gear down indication. This was tried a number of times, I then decided to return to FWA with 1000 pounds of fuel remaining. I notified Peoria tower that I was not landing and I was returning back to Fort Wayne. They handed me over to Peoria departure and they gave me VFR flight following back to Indiana. As I flew back to FWA, the gear retracted up to about a 45 deg angle, flying speed was about 145kts indicated. During the flight I went through the aircraft manual to determine what else could be done. I reviewed speeds and looked for procedures for belly up or gear up landings. There was no information on covering this situation. After the VFR hand off from Grissom, I had notified FWA approach to give me a IFR decent to VFR conditions upon reaching FWA. They did so and I cancelled the local IFR upon becoming VFR in the airport area. Upon reaching FWA, I notified Mercury [Air Center] of the situation as well as notifying the FWA controller of a precautionary landing which could change to an emergency situation. The total flight time at this point was about 2.6 hours from start to finish. I talked with FWA maintenance and they recommend again to retract the gear, I did so and nothing happened. They requested that I fly over the FBO, where there were about 5 people observing the fly over and the partially extended gear. Again, additional positive and negative load maneuvers, but still no green lights for the main gear. In talking with FWA maintenance, it was decided by both mechanic and pilot to do an emergency landing with gear partially extended, gear was about 97% in the down position, both parties agreed to land on the runway with engines secured before landing. I notified the tower what my intentions were to "now" declare an emergency landing, this was after the fly-by and on a long down wind for runway 23. Tower advised me to plan on landing on runway 23. I went through what I believed to be good operating practice to land with flaps full and both engines feathered and off to establish a reasonable glide speed. I verified by the power levers in the flight idle dent that the gear warning horn would and did sound for a gear unsafe indication. As mentioned there is no procedure in the manual for what I was about to do. I relied on years of experience and airline training to determine the best method for the situation. I briefed the passengers of the emergency evacuations procedures and main door for exits, at that time I removed the fire extinguisher from under my seat just in case of use. As I turned final and about 1200 agl and 3-4 miles out I secured the left engine first and notified that tower that all radio equipment would also be shut down, I did a last second verification that the gear indicators read: front gear green and locked, left and right gear no green light illumination. Tower was aware of the radio shut down and approved landing on runway 23. Prior to reaching about 700 agl, and runway assured, I lowered the flaps to full and secured the right engine and shut down all electrical, hydraulics valves, bleed valves and pressurization valves. I established a gradual descent and approach speed was about 120kts. Upon reaching the ground and centered on the runway centerline at minimal speed, I was able to maintain directional control with the rudder up to about 40kts. After speed deteriation, the airplane slid and skidded to the left and struck the runway 32-14 sign at about 30 kts. Upon stopping, evacuation procedures were commenced, I verified all electrical and hydraulic switches were shut down. The airplane was evacuated from the right escape hatch with no injuries and damage was only to the fuselage. I did notice that the right gear was down and locked as it was not retracted like the left gear. Therefore the right landing gear may have come down just before touch down, but this can not be verified as battery power was shut off at the time. It should be noted that the mechanic ... and I both verified that there was hydraulic fluid on the dip stick just under the full mark in the hydraulic reservoir, again this had been observed to be in "normal fluid levels" during the preflight inspection. The pilot stated that he had completed the before landing and emergency landing gear extension checklists. PERSONNEL INFORMATION The pilot held an airline transport pilot airplane multiengine land rating. He held a first-class medical certificate dated December 3, 2004. He had a flight review completed on February 6, 2004. He reported that he accumulated 7,000 hours of total time in airplanes, 500 hours total time in this make and model, 75 hours in the 90 days prior to the accident in this make and model, and 20 hours in the 30 days prior to the accident in this make and model. AIRCRAFT INFORMATION N688TM, a Twin Commander Aircraft Corporation 680V, serial number 1687-67, was a twin-engine, high-wing, pressurized airplane of all-metal construction. The 680V can be configured to seat up to nine passengers and N688TM was reported to be configured for six passengers. The airplane was powered by two Honeywell TPE 331-1-151K turboprop engines. The engines were rated at 665 shaft horsepower continuously. The pilot reported that the last annual inspection was performed on September 24, 2004, and that the airplane had accumulated 57.7 hours since the time of that inspection. The airplane had accumulated 7,115.7 hours of total time. The airplane maintenance manual, in part, described the landing gear system as: The retractable tricycle landing gear is operated hydraulically; however, a pneumatic system is provided for emergency extension of the main landing gear in the event of hydraulic system failure. The nose landing gear is held in the up position by hydraulic pressure and will free-fall to the down and locked position if the hydraulic system fails. Mechanical uplocks hold the main landing gear in the retracted position. During the retraction cycle the main landing gear strut interbody is rotated 90 degrees to permit the landing wheels to retract into a well in the aft part of the engine nacelle. Mechanically actuated nacelle doors enclose the main strut body. The wheel wells are enclosed by hydraulically operated doors which open and close during the landing gear retraction or extension sequence. The airplane's flight manual, in part stated: BEFORE LANDING 1. Safety belts - FASTENED. 2. Landing gear warning horn - CHECK (before extending landing gear). 3. Landing gear - DOWN. a. Gear safe lights - ILLUMINATED. b. Hydraulic pressure - NORMAL. c. Landing gear warning horn - SILENT CAUTION DO NOT extend landing gear when airspeed is above 156 knots (180 mph). 4. Hydraulic pressure - CHECK. 5. Condition lever - HIGH RPM. 6. Wing flaps - DOWN 1/2 (20 [degrees]). CAUTION Do not lower wing flaps at airspeeds in excess of 130 knots (150 mph). 7. Cabin pressurization switch - DEPRESS (1,000 feet above airport elevation). 8. Air conditioning selector switch - FLT AUTO. ... EMERGENCY LANDING GEAR EXTENSION If utility hydraulic system pressure or 1000 psi is not available, the landing gear may be lowered as follows: 1. Airspeed - MINIMUM (safe flight). 2. Landing gear lever - DOWN. NOTE Air pressure from the landing gear emergency air storage cylinder will extend the main landing gear to the down and locked position. The nose gear will free fall to the down and locked position. Allow 3 minutes for full extension of gear. 3. Landing gear down and locked - CHECK. METEOROLOGICAL INFORMATION At 1354, the recorded FWA weather was: Wind 260 degrees at 9 knots; visibility 8 statute miles; sky condition overcast 1,600 feet; temperature -2 degrees C; dew point -6 degrees C; altimeter 30.04 inches of mercury. AIRPORT INFORMATION The East Central US Airport/Facility Directory (A/FD) indicated FWA's field elevation was 815 feet above mean sea level (MSL). The A/FD showed FWA as a towered airport with three runways, 05/23 (12,000 feet by 150 feet), 14/32 (8,001 feet by 150 feet), and 09/27 (4,001 feet by 75 feet). TESTS AND RESEARCH The airplane was ferried to a fixed base operator at Bethany, Oklahoma for troubleshooting and repairs. The manufacturer assisted in the troubleshooting examination. The manufacturer reported the following findings: 1. Both hydraulic pumps were functional and hydraulic system operated normally. 2. A check of the main landing gear overcenter adjustment was determined to be correct. 3. Repeated landing gear retraction tests were performed. 4. The main landing gear down and locked switches were found to be out of adjustment resulting in the failure of the down and locked indicators to illuminate. 5. A check of the gear handle to selector valve rigging and security was recommended and no reports of discrepancies reported. ADDITIONAL INFORMATION Parties to the investigation included the FAA and Twin Commander Aircraft Corporation. The wreckage was released to a representative of the owner on June 8, 2005.
The malfunction of the landing gear extension assembly during approach for undetermined reasons.
Source: NTSB Aviation Accident Database
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