Plane & Pilot
Tuesday, June 1, 2004

Devastating Details

Even minor maintenance mistakes can be fatal

Beech V35B
On January 26, 2003, at 5:36 p.m., a Beech V35B was substantially damaged during a forced landing at Pea Patch Island, near Delaware City, Del., following a total loss of engine power during cruise flight. The certificated private pilot and passenger received fatal injuries. Night visual meteorological conditions prevailed at the time of the accident. The flight had departed Wings Field (LOM) in Philadelphia, destined for Columbia Metropolitan Airport (CAE) in Columbia, S.C. An IFR flight plan was filed for the personal flight conducted under Part 91.

Review of FAA air-traffic-control data revealed that the flight departed about 5:10. At 5:12, the pilot contacted Philadelphia Departure Control and advised that he had an IFR flight plan on file. The controller acknowledged the transmission and provided the pilot a clearance, which included a climb to an altitude of 4,000 feet MSL. At 5:17, the pilot reported that he had reached 4,000 feet.

At 5:30, the pilot declared an emergency, reporting a terrible vibration, possibly an engine or propeller problem. The controller suggested that the pilot divert to New Castle County Airport (ILG), Wilmington, Del., which was eight miles behind the airplane. The pilot agreed, and the controller provided a vector to the airport.

At 5:31, the pilot reported that the airplane lost engine power. The controller stated that ILG was at the pilot’s 11:00 position and seven miles away. At 5:34, the pilot reported that he was at 1,000 feet and descending, and wouldn’t reach ILG. The controller replied that the emergency crew would be notified to respond to the landing area. About one minute later, the controller reported that radar contact was lost. The airplane impacted a wooded area about six miles south of ILG.

The pilot held a private-pilot certificate, with ratings for single-engine land and instrument airplane. His most recent FAA third-class medical certificate was current. On his medical application, the pilot reported a total flight experience of 2,960 hours.

According to a mechanic who worked on the airplane, the most recent annual inspection was performed on March 1, 2002. The mechanic estimated that the airplane had flown approximately 200 hours from the time of the annual inspection, until the accident. During November 2002, the mechanic completed a top overhaul of the engine, which included the installation of six new cylinders.

The engine was examined at the manufacturer’s facility. The magnetos had separated from their respective mounts in the vicinity of the number-one and number-two cylinders, but they remained attached to the ignition leads. The magnetos, fuel pump, vacuum pump, starter and spark plugs were removed from the engine. Approximately three to four quarts of oil were drained from the engine.

A silicone sealant was observed along mating surfaces where the cylinders were attached to the case. Additionally, the substance was on the through-bolts.

The number-two cylinder was found backed off from the case. The engine case showed evidence of rub marks from the number-two cylinder. The number-two piston ring had shattered. The number-two piston skirt exhibited impact marks consistent with the skirt striking the case. The number-two connecting rod revealed elongated holes consistent with an overstress failure, and the rod cap wasn’t recovered. Additionally, the top of the case exhibited two holes in the vicinity of the magnetos.

The engine manufacturer had issued a service information letter (SIL) 99-2A related to current authorized sealants, lubricants and adhesives. The SIL didn’t list the type of silicone sealant found by investigators as an approved sealant on the mating surfaces of the crankcase halves or cylinders to the crankcase. Additionally, a review of a service bulletin (SB) 96-7B, which related to torque values for fasteners on all of the manufacturer’s engines, stated: “Warning[—]the use of sealants or lubricants other than those specified by [manufacturer] on mating threads and between mating surfaces can cause incorrect torque application and subsequent engine damage or failure.”

In a written statement, the mechanic reported that he added the sealant to the cylinder bases during the engine assembly. He said that he had referred to SIL 99-2A, but “[the type of sealant used] isn’t mentioned, either pro or con.” During a telephone interview with investigators, the mechanic stated that he hadn’t referred to SB 96-7B.

The National Transportation Safety Board determined that the probable cause of this accident was the mechanic’s improper engine overhaul. Another factor that caused the accident was the nighttime condition.

Peter Katz
is editor and publisher of NTSB Reporter, an independent monthly update on aircraft accident investigations and other news concerning the National Transportation Safety Board. To subscribe, write to: NTSB Reporter, Subscription Dept., P.O. Box 831, White Plains, NY 10602-0831.


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