NTSB Factual Report

HISTORY OF FLIGHT

On April 27, 2009, at 0700 eastern daylight time, a Cessna 402C, N769EA, Cape Air flight 84, registered to Hyannis Air Service LLC, operated by Cape Air/Nantucket Airlines as a 14 Code of Federal regulations Part 135 scheduled domestic passenger flight, received minor damage when the left main landing gear collapsed during landing roll out at Nantucket Memorial Airport (ACK), Nantucket, Massachusetts. Visual meteorological conditions prevailed and a company visual flight rules flight plan was filed. The certificated airline transport pilot and eight passengers reported no injuries. The flight originated from Barnstable Municipal Airport (HYA), Hyannis, Massachusetts, at 0633.

The pilot stated he lowered the landing gear on final approach to runway 6 at ACK. The left main landing gear light did not illuminate and the landing gear unlock light and hydraulic pressure light remained illuminated. The pilot recycled the landing gear with negative results. He informed the Nantucket control tower of the malfunction and made a go-around. The pilot completed the "Gear Will Not Extend" checklist and activated the blow down bottle with negative results. He then completed the "Landing With Defective Main Gear" checklist and asked the tower operator to notify the airport rescue and firefighting. The pilot landed the airplane on runway 6 and the left main landing gear collapsed.

PERSONNEL INFORMATION

The captain, age 24, holds an airline transport pilot certificate with a rating for airplane multiengine land. He holds a commercial pilot certificate with a rating for airplane single-engine land, issued on August 13, 2008. In addition, he holds a flight instructor certificate with ratings for airplane single-engine, airplane multiengine, and instrument airplane, issued on May 29, 2008. He also holds a ground instructor certificate with ratings for advanced instruments issued on August 13, 2008.

The operator hired the captain on May 5, 2005, and he completed his initial operating experience (IOE) in the Cessna 402 on June 20, 2007. The pilot completed his initial Part 135 check ride as a second-in-command on July 14, 2005. He completed a pilot-in-command (PIC) checkride for mail and freight on June 13, 2006, and was qualified as a PIC in all company operations on June 19, 2007. His last Part 135 checkride was on January 18, 2009, and his last line check was on January 26, 2009. The captain has 3,525 total flight hours; of which, 2,750 hours are in the Cessna 402C and 3,111 hours as PIC. He holds a first-class medical certificate issued on April 15, 2009 with the limitation, "must wear corrective lenses." Review of the captain's training records revealed all pertinent aviation records pertaining to 14 CFR Part 135 airman competency and proficiency checks had been recorded as conducted.

AIRCRAFT INFORMATION

The Cessna 402C, serial number 402C0303, is a twin-engine airplane with a tricycle landing gear manufactured in 1980. The airplane has a seating capacity of one flight crew, and nine passengers. Two Continental TSIO-520-VD fuel injected 325-horsepower engines power the airplane. Hyannis Air Service LLC purchased the airplane from Canyon leasing Inc., on January 8, 1999. The last approved aircraft inspection program (AAIP) inspection was completed on April 18, 2009.The total airframe time at the time of the incident was 24,161 hours. The left engine had 2,321.6 total flight hours at the time of the incident, and had flown 5.9 hours since the inspection. The right engine had 10.8 total flight hours at the time of the incident, and had flown 5.9 hours since the inspection. The last gear retraction test before the incident and emergency gear extension test was completed on April 16, 2009.

METEOROLOGICAL INFORMATION

The 1628 ACK surface weather observation was: wind 120 degrees at 9 knots, visibility 10 miles, sky clear, temperature 10 degrees Celsius, dew point temperature 4 degrees Celsius, and altimeter 30.39 inches of mercury.

WRECKAGE AND IMPACT INFORMATION

The airplane came to a stop in the grass off the left side of runway 6, and an emergency evacuation was completed. Initial inspection of the airplane by an Federal Aviation Administration (FAA) inspector revealed the left main landing gear collapsed during landing when the left gear did not lock in the down position. The left flap was scraped on the lower left surface and the left wing tip was damaged. A dent was present on the left wing about 8 feet inboard of the left engine, where it collided with a taxiway light. The left propeller was also damaged.

The airplane was lifted up with recovery equipment; maintenance personnel extended the left main landing gear by hand, and verified the landing gear was down and in the locked position. The airplane was towed to the ramp and inspected.

An FAA inspector issued a special flight permit on April 29, 2009, and the airplane was flown to HYA for further inspection and repair. A Landing gear retraction test was conducted and the failure of the left main landing gear to extend was duplicated. It was noted that hydraulic pressure was available at the extend inlet side of the up lock actuator, but not on the extend outlet side of the actuator. Although the up lock actuator properly retracted, the up lock hook allowed the landing gear to fall from the well. The extend inlet port was removed for inspection. It was discovered that one of the small ball bearings was in the wrong position with respect to the larger ball bearing. In addition, the ball bearing was smaller in diameter, allowing the smaller ball bearing to jump the larger ball bearing, causing a blockage. The up lock actuator and the main gear actuator were removed and placed in quarantine pending further examination.

Disassembly of the up lock actuator at an authorized repair facility found an improperly sized ball bearing installed, which controls the port opening to the actuator. The actuator housing was damaged in the area of the ball seat along with the ball spring and fitting assembly. The main gear actuator was tested and all functions of the lock, unlock, and all pressure limits were within manual limits.

The operator's Director of Maintenance stated, “The up lock actuators are on a condition item and we do not have them overhauled. All work on these actuators are performed in our in-house shop by 1 individual performing this work for over 10 years. This individual was questioned and indicated that he has never replaced the ball bearings in the actuator. The only work performed on these actuators is to replace the o rings on the fittings due to leaking, and if needed due to corrosion pitting, the internal shaft is replaced.” He further stated the actuators have not been added to the tracking system. “We have no way of properly tracking it to look at its history. Since this event was a latent failure, we have no idea who, when, or how long the ball in question was placed in the actuator.”

MEDICAL AND PATHOLOGICAL INFORMATION

Toxicology specimens were taken from the captain. The specimens were sent to Mid Cape Medical Center, Hyannis, Massachusetts for analysis. The results were negative for amphetamines, opiates, marijuana, cocaine, and phencyclidine.

TEST AND RESEARCH

Review of FAA surveillance records for the Part 135 operation of Hyannis Air Service Inc., revealed the FAA conducted 81 maintenance or operation enroute inspections, 207 airworthiness surveillance inspections, 113 operations inspections, and 13 facility inspections, from April 27, 2008, through April 27, 2009.

NTSB Probable Cause

Installation of an improper bearing in the landing gear actuator.