Cessna 402C accident at US, 13 Jul 2003

Accident narrative

On July 13, 2003, about 1530 eastern daylight time, Air Sunshine, Inc., Flight 527, a Cessna 402C, ditched in the Atlantic Ocean about 7.35 nautical miles west-northwest of Treasure Cay Airport, Great Abaco Island, Bahamas. The ditching followed an in-flight failure of the right engine. Of the ten people aboard, one adult and one child passenger died after evacuating the airplane. Two passengers were uninjured, and five passengers and the pilot sustained minor injuries. The airplane sustained substantial damage.

### The flight

Flight 527 was a scheduled international passenger commuter flight from Fort Lauderdale/Hollywood International Airport in Florida to Treasure Cay Airport. Aboard were the pilot and nine passengers, including four children. The 46-year-old pilot held an airline transport pilot certificate and had accumulated about 8,000 hours of total flying time, including about 5,000 hours in Cessna 402 airplanes.

Before departure, the pilot briefed the passengers on the location of personal flotation devices (PFDs), exits, and safety cards. One passenger noted the briefing was short and rushed and did not include how to handle children during an emergency. The flight was cleared for takeoff at 1427:11. The pilot and adult passengers stated the cruise portion of the flight at about 7,500 feet was uneventful.

### The sequence of events

During the descent into Treasure Cay, about 20 to 25 miles from the airport and descending to about 3,500 feet, the pilot heard a bang and saw oil coming out of the right engine cowling. Passengers reported seeing white smoke from the right engine, followed by a stream of oil, a loud bang, and parts falling from the engine.

The pilot stated that he reduced power to the right engine and saw that the engine magnetos had penetrated the cowling and were hanging from wires. He attempted to feather the right propeller and shut down the engine, but the propeller continued windmilling slowly. The pilot applied full power to the left engine and slowed the airplane to the single-engine best climb rate airspeed of about 105 knots indicated airspeed (KIAS), but the airplane descended at a rate of about 200 to 300 feet per minute.

The pilot contacted the Air Sunshine station manager at Treasure Cay, reporting the engine failure and his altitude. The station manager relayed the information to the company's Director of Operations, who instructed the pilot to keep the good engine at full power and bank toward it. The pilot responded that he had already done so. The station manager alerted local agencies and another Air Sunshine pilot, who transmitted a distress call that was relayed to the Miami Air Route Traffic Control Center.

The pilot stated he slowed to about 95 KIAS to try to maintain altitude. Descending from 1,500 to 1,000 feet, he realized the airplane could not reach the airport and would have to be ditched. He ditched the airplane parallel to the waves. Passengers described the contact with the water as very hard and flat.

Passengers stated that the pilot did not instruct them to retrieve their PFDs or assume a brace position before contact with the water, only telling them to "calm down." The pilot, who reported he was not wearing his shoulder harness, hit his head on the instrument panel. The occupants evacuated through the pilot-side window hatch and the main cabin door. Only four of the ten PFDs on board were retrieved and used by passengers before the ditching; others reported they could not retrieve them from their stowage pouches. The airplane sank within several minutes. Passengers reported the pilot was incoherent in the water and had to be given a PFD. The occupants were in the water for about an hour and a half before being rescued by Coast Guard helicopters. The adult female and child who died were not wearing PFDs when they were recovered.

### What the investigation found

The airplane was recovered from the water about three weeks after the accident. Investigators found the left and right flaps possibly extended about 15 degrees, and the right engine cowl flap open. The right propeller blades were found in the feathered position, though the pilot and passengers reported the propeller continued turning until the airplane contacted the water. The Board could not determine at what point the propeller became fully feathered.

Examination of the right engine revealed that the No. 2 cylinder had separated from the engine crankcase. Two intact cylinder hold-down studs were found in the crankcase without nuts, and four studs and two through bolts were fractured. Metallurgical examination found the fractures were consistent with high-stress fatigue. The threads on the intact studs and on two hold-down nuts found in the engine compartment were undamaged, indicating the nuts had backed off. The Board concluded that two or more of the hold-down nuts became loose and backed off the studs, transferring loads to the remaining fasteners and allowing the cylinder to separate. The Board concluded this simultaneous loosening resulted from the application of insufficient torque by maintenance personnel during undocumented maintenance.

A review of maintenance records showed the last scheduled engine maintenance was a phase 1 inspection in June 2003, which included differential compression checks. An uncertificated assistant mechanic performed the checks on the right engine unsupervised, recording readings of 0 psi and 20 psi on two cylinders. The Director of Maintenance stated he repeated the checks and obtained acceptable readings, but no documentation of the repeated checks was found. The Board concluded that Air Sunshine's maintenance record-keeping and practices were not adequate.

The Board conducted an airplane performance study to determine why the airplane could not maintain altitude. Cessna data indicated the airplane should have had a climb rate of about 200 feet per minute on one engine. However, several factors degraded performance, including the windmilling propeller, the protruding magnetos, the open right engine cowl flap, and the possibility that the flaps were extended to 15 degrees during the descent. The Board calculated that the airplane's descent rate was between 560 and 212 feet per minute during its descent from 3,500 to 2,000 feet. The Board concluded that if the average descent rate had been about 200 feet per minute or less, the airplane would have been able to maintain flight and reach the airport. The Board noted the pilot had a history of below-average flight proficiency, including nine failed flight checks between 1983 and 1998, which contributed to his inability to maintain maximum flight performance.

The Board also concluded that the pilot's failure to wear his shoulder harness resulted in a head injury that reduced his ability to assist passengers. Furthermore, the pilot's failure to conduct an emergency briefing after determining he was going to ditch the airplane contributed to the passenger fatalities, as passengers would have had sufficient time to retrieve and don their PFDs if instructed to do so shortly after the engine failed.

### Probable cause

The National Transportation Safety Board determined that the probable cause of this accident was the in-flight failure of the right engine and the pilot’s failure to adequately manage the airplane’s performance after the engine failed. The right engine failure resulted from inadequate maintenance that was performed by Air Sunshine’s maintenance personnel during undocumented maintenance. Contributing to the passenger fatalities was the pilot’s failure to provide an emergency briefing after the right engine failed.