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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
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
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
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
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
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.
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.
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:
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.
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.
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
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
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.