NTSB Factual Report

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 DATA/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.

NTSB Probable Cause

The malfunction of the landing gear extension assembly during approach for undetermined reasons.