N41078 – Piper Aircraft Corp PA-31-350 – 1999-06-11 NTSB Accident Report

HISTORY OF FLIGHT

On June 11, 1999, about 0723 Alaska daylight time, a Piper PA-31-350 airplane, N41078, was destroyed by impact with trees and the Yukon River, about 1.5 miles southwest of Tanana, Alaska. The airplane was being operated as Flight 1604 from Fairbanks, Alaska, to Tanana, to Galena, Alaska, as a visual flight rules (VFR) scheduled passenger/cargo flight under Title 14, CFR Part 135. The airplane was operated by Larry's Flying Service Inc., Fairbanks. The certificated airline transport pilot, the sole occupant, received fatal injuries. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect.

Flight 1604 departed Fairbanks about 0631 and was carrying cargo only. The flight landed at the Ralph M. Calhoun Memorial Airport, Tanana about 0712. According to the operator's records, 109 pounds of cargo was unloaded. About 1,236 pounds of cargo remained on the airplane. The airplane departed runway 24 about 0718 for Galena.

A witness at the airport saw the airplane arrive in Tanana. He said the engines sounded normal. When the engines were started for departure, he noted the right engine was started first after extended cranking. Once started, the right engine ran at a high idle. The left engine was then immediately started. It ran at a lower rpm, and sounded normal. The witness saw the airplane depart, and said that after the landing gear retracted, the airplane leveled off and stayed low over the river. The airplane turned to follow the Yukon River instead of climbing.

A village agent for the operator reported he heard the airplane arrive in Tanana, and it sounded normal. He departed the airport before the airplane took off. About five minutes after he left the airport, he heard a loud noise from the river area. He heard a loud bang, followed by a loud screeching noise, and then quiet.

About five minutes after departure, the pilot contacted a local weather observation service at Tanana on the common traffic advisory frequency (CTAF). The pilot radioed that he was having a problem with the airplane, and stated he may have to ditch. He did not describe the nature of the problem. About 15 seconds later, the pilot radioed that he was over the river, the airplane was clipping trees, and he was attempting to return to the runway.

The airplane collided with several trees located on a small island in the Yukon River, separating the outboard end of the left wing. The airplane then collided with the water and sank.

The accident occurred during the hours of daylight at latitude 65 degrees, 09.5 minutes north, and longitude 152 degrees, 09.4 minutes west.

CREW INFORMATION

The pilot held an airline transport pilot certificate with an airplane multiengine land rating. He held commercial pilot privileges with airplane single-engine land and sea ratings. The most recent first-class medical certificate was issued to the pilot on February 25, 1999, and contained no limitations.

The pilot was an enlisted member of the U.S. Air Force. His previous 72 hour military schedule was provided by personnel from the Eielson Air Force Base, Fairbanks. The pilot was on duty with the Air Force from 1800, June 7, to 0600, June 8. He was scheduled to be off duty from June 9, to June 11.

According to flight and duty records provided by the operator, the pilot logged 2.4 hours of flight time for the operator on June 9, from 0830 to 1100. On June 10, he logged 4.3 hours from 0630 to 1330. His anticipated flight time on June 11, was to be a repeat of the previous day. The pilot's personal flight logs were not located.

The pilot was hired by the operator on March 7, 1996. According to the operator, the pilot had accrued 3,226.7 hours of total experience, 861.2 of which were in the accident airplane make and model. In the previous 12 months before the accident, the pilot accrued 826.7 hours, of which 611.2 were in the accident airplane make and model. In the previous 30 days, the pilot accrued 51.2 hours, and 48.7 in the accident airplane. In the previous 24 hours, the pilot accrued 5.3 hours in the accident airplane.

AIRCRAFT INFORMATION

The airplane was maintained on a phase inspection program, as part of a Federal Aviation Administration (FAA) approved aviation inspection program (AAIP). A complete inspection of the airplane consists of four event inspections, each accomplished every 55 hours, for a total of 220 hours for the entire cycle. A complete inspection cycle is required to be accomplished within a 12 calendar month period, and qualifies as an annual inspection for the airplane. Each event inspection consists of detail items, and routine items. According to the AAIP, A routine inspection consists of a visual examination or check of items, as practical, without disassembly. A detailed inspection consists of an examination necessitating disassembly of items, as required. Each event inspection includes maintenance discrepancy items that are in addition to those specifically listed in the AAIP.

The most recent inspection of the airplane was an Event Four inspection, conducted on June 4, 1999. The inspection consisted of a detailed inspection of the right engine, the right propeller, the right engine turbocharger, and the landing gear. A routine inspection of the left engine, the left propeller, the left engine turbocharger, and fuselage, was also part of the Event Four inspection.

At the last inspection, the airplane had accrued 15,208.9 hours total time. The left and right engines had 1290.3 hours since overhaul. Both engines were overhauled by the operator on February 14, 1998. The left propeller had accrued 2128.6 hours since overhaul. The right propeller had accrued 1871.8 hours since overhaul.

Since the last inspection, until the airplane departed for Tanana on the day of the accident, the airplane accrued an additional 20.5 hours. Examination of the maintenance records revealed no uncorrected discrepancies since the last inspection.

Examination of the maintenance records disclosed several fuel system related discrepancies from January 1999, to June, 1999. During an Event Four inspection on January 4, 1999, the right engine fuel pump had evidence of a slight leak. It was retorqued. The right wing fuel sump drain was leaking. The sump valve was replaced. During an Event One inspection on January 22, 1999, the airplane fuel regulator was leaking. It was replaced. During an Event Two inspection on February 22, 1999, fuel stains were noted in the left engine accessory section. The fuel line to the fuel pump was tightened. During an Event Three inspection on March 18, 1999, the right engine's number one cylinder induction tube had signs of a fuel leak. New gaskets were installed. During an Event Four inspection on April 6, 1999, the right engine fuel pump had signs of fuel leaking around the adjustment head. The pump was retorqued. The left engine fuel pump had signs of fuel staining. A fitting on the pump was cleaned and resealed. During an Event Two inspection on May 6, 1999, a fuel leak was noted on the number 2 cylinder on the left engine. A bolt was replaced on the intake pipe flange. The fuel line to the airplane heater had signs of fuel staining. The fuel line fitting was tightened. During an Event Three inspection on May 23, 1999, the number three and number five cylinder induction tubes on the right engine were leaking. The gaskets were replaced.

The maintenance records note that during the Event Four inspection on April 6, 1999, a discrepancy was noted that stated, "left engine - wrench sticking out of engine by alternator." The sign-off for the discrepancy was, "removed wrench and returned to proper location."

The pilot's operating handbook for the accident airplane specifies the use of zero flaps for a normal takeoff, and 15 degrees of flaps for a short field takeoff. After takeoff, the flaps are retracted before the airplane reaches 128 knots.

The pilot's handbook specifies airplane's minimum controllable airspeed is 76 knots. The best single-engine angle of climb speed is 104 knots. The best single-engine rate of climb speed is 106 knots.

The emergency engine inoperative procedure for engine securing (feathering procedure), specified in the pilot's handbook states, in part: Throttle, close; Propeller, FEATHER; Mixture, Idle Cut-Off; Cowl flaps, close...Fuel Selector, OFF (detent).

METEOROLOGICAL INFORMATION

The closest official weather observation station is Tanana, Alaska, which is located 1.5 nautical miles northeast of the accident site. On June 11, at 0652, an Automated Weather Observation Station (AWOS) was reporting in part: Wind, calm; visibility, 40 statute miles; clouds, few at 10,000 feet, few at 18,000 feet; temperature, 57 degrees F; dew point, 48 degrees F; altimeter, 29.90 inHg.

COMMUNICATIONS

The CTAF for the Tanana airport is 122.9 MHz. There is no recording capability of communications at the airport, or with the local weather observer.

AERODROME AND GROUND FACILITIES

The Tanana airport is located along the north shore of the Yukon River. It is equipped with a single gravel surface runway on a 060 to 240 degree magnetic orientation. Runway 24 is 4,400 feet long by 150 feet wide, and is equipped with medium intensity runway lights. Local airport weather observations, (call sign: Tanana Weather), are available on the CTAF.

WRECKAGE AND IMPACT INFORMATION

FAA inspectors from the Fairbanks, Alaska, Flight Standards District Office (FSDO) responded to the area of the accident on June 11. They located an area of impact with several large trees, about 45 feet above the ground, and about 200 feet south of the northwest shoreline of Long Island. From the first observed point of impact in the tree line, heading towards the Tanana Airport, the terrain consisted of, in sequence, a heavily wooded island, a small area of open water, a large gravel bar, another area of open water, and then the airport.

From the area of tree impact, toward the wreckage point of rest in the Yukon River, a path of wreckage debris, consisting of broken tree limbs and portions of the airplane, was observed on a magnetic heading of 330 degrees. The outboard end of the left wing, the outboard left and right main landing gear doors, the inboard left main landing gear door, the right wing tip cap, and other debris, were found on the island in an area of thick trees.

At the time of the accident, the Yukon River was flowing about 6 to 8 knots. The water was highly silted. Visibility in the water was 2 to 4 inches.

Local residents located wreckage in the Yukon River in about 15 feet of water, and placed a buoy on the largest piece. FAA personnel and Alaska State Troopers supervised recovery efforts to raise the wreckage from the river. Efforts of local volunteers were unsuccessful. Alaska State Trooper divers were not utilized because of hazards to their personnel from the river current. A river barge was called to the scene by the Alaska State Troopers, but efforts to raise any wreckage were again unsuccessful. A team of commercial divers from Anchorage, Alaska, were called to assist with the recovery, and they began diving about 0315 on June 12. A diver identified the fuselage of the airplane, but recovery of wreckage or the pilot was not possible due to the speed of the current. An attempt to capture the fuselage with a net was unsuccessful. Finally, a steel cable was looped around the fuselage and it was dragged to shallow water where a diver recovered the pilot about 1515. About 1730, the fuselage was dragged partially onto a shore area of the river. The right wing, and right engine were not attached to the fuselage, and were not recovered. The left engine was attached to the wing, and was bent to the left.

On June 13, a buoy was placed on what was thought to be the separated right wing and engine. The operator continued to search for the remaining wreckage, and explored the feasibility of utilizing equipment capable of locating underwater objects. The high water flow of the river prevented the use of towed search devices. The operator later learned the buoy was attached to a submerged log.

The wreckage was transported by river barge to Nenana, Alaska, where it was loaded onto a trailer, and transported to Wasilla, Alaska.

An examination of the wreckage was conducted on June 30, at Wicks Aircraft, Wasilla. The NTSB investigator-in-charge, an FAA airworthiness inspector from the Anchorage FSDO, and the parties noted in this report participated in the examination.

The forward, lower half of the fuselage from the nose to the trailing edge of the wing, the left wing, instrument panel, cockpit, and the first row of passenger seats, were separated as one segment from the rest of the airplane. The line of separation progressed clockwise from the inboard trailing edge of the left wing, upward to the left fuselage window belt, then forward to the instrument panel, then down to the floor of the nose section, circumferentially around to the right side of the instrument panel, upward to the window belt, and downward, laterally across the wing spar, just aft of the first row of passenger seats. A second segment consisted of the windshield, upper fuselage skin, cabin, and empennage.

For transportation, the left engine was removed from the left wing. During the wreckage examination, the left engine cowl flaps were observed in the open position.

The right wing separated from the fuselage. The lower right fuselage main spar attach point was bent forward about 45 degrees. A small piece of right wing structure, the right wing tip cap, and the outboard right main landing gear door were recovered.

The outboard 4 and 1/2 feet of the left wing was separated about midspan between the left engine nacelle, and the wing tip. The area of separation had aft and upward, semicircular leading edge crushing and tearing, and chordwise tearing along the outboard end of the outboard fuel tank. The left aileron remained attached to the separated wing tip segment. The left flap remained attached to the inboard segment of the wing, and the flap actuator was extended to an 11 degree setting. The inboard section of leading edge wing, between the nacelle and the fuselage, was crushed aft and upward in a semicircular shape. The leading edge of the wing metal, from the nacelle, outboard to the end of the outboard fuel tank, was torn away and missing, exposing the forward end of the outboard fuel tank.

About four inches of fuel was present in the left inboard fuel tank, and about 3 and 1/2 inches of fuel was visible in the left outboard tank. The left nacelle tank was dry. As the wreckage was lifted from a trailer during the wreckage examination, fuel was observed draining from the inboard end of the left wing. The fuel had a blue appearance without any visible contaminants.

The cabin fuselage had minor wrinkling, and contained a large amount of silt and rocks. The upper portion of the main cabin door was attached to the fuselage. The lower half of the cabin door had separated from the fuselage. The cargo door, aft of the main cabin door, was attached to the fuselage at its upper pivot.

The leading edge of the left vertical stabilizer had semicircular aft crushing about 2 feet outboard from the fuselage. The face of the crushed area was vertically flattened, and angled aft at the bottom edge about 30 degrees. The leading edge of the outboard end of the left stabilizer was deformed upward with upward curling of the trailing edge. The right horizontal stabilizer received minor wrinkling. The elevator was attached to the stabilizer at the left and right inboard pivots. The left outboard end of the elevator was broken from the stabilizer and was wrinkled spanwise, with upward curling of the trailing edge tip. The right outboard end of the elevator was broken from the stabilizer and bent downward about midspan. The elevator trim tab was attached to the right elevator; the aft end of the actuator was fractured.

The lower 1/4 of the rudder was torn from the vertical stabilizer. The rudder trim tab was separated from the rudder at its upper attach point and bent aft. The rudder trim actuator was fully extended to a trailing edge left (nose right) position. The upper portion of the rudder was attached to the vertical stabilizer.

The overhead panel of the cockpit was crushed and folded in an aft direction. The instruments and controls contained in the panel were destroyed. The instrument panel was crushed aft and curled rearward along the right side. The entire panel was twisted and distorted toward the left. The control pedestal was displaced to the left. The throttle levers, mixture levers, and the propeller levers were all found full forward.

Examination of the fuel selector panel, located on the floor between the two front seats, revealed the left and right inboard fuel tanks were selected. The crossfeed valve was off. The left engine firewall shutoff valve was in the open/on position. Examination of each respective valve positions, located on the inboard side of left wing root, corresponded with the fuel selector positions.

The inboard and outboard left main landing gear doors separated from the underside of the wing. The leading edge of each door were crushed slightly upward and aft. A score mark was on the underside of the left wing, oriented about a 40 degree angle to the longitudinal axis of the airplane, running from near the leading edge of the wing, toward the inboard, trailing end. The left main landing gear was retracted into the wheel well, but the up-lock was not engaged.

The leading edge of the outboard right main landing gear door was crushed aft and had several brown-colored chordwise striations along the folded metal edge. The aft lip of the aft door pivot bracket was bent aft. The forward and aft pivot arms, normally attached to their respective brackets, were torn out of the brackets. The aft pivot arm, normally attached to the landing gear strut, was bent aft and separated at the threaded portion of the adjustment rod.

The left nose wheel gear door was torn from its mounting brackets. The right nose wheel gear door had minor bending of the lower aft edge. The landing gear was retracted into the wheel well. The up-lock was not engaged on its locking lug. The nose gear did not have any damage to the strut, scissors, wheel, or tire. A push/pull tube between the gear strut and the hydraulic actuator was fractured. The two nose strut mounted landing lights were undamaged.

The left engine propeller assembly remained connected to the engine crankshaft. The propeller governor housing was fractured and bent at the base. The governor control arm was broken. The propeller appeared to be feathered. The propeller will move to a feather position, or against the low pitch stop, if there is an internal failure of the governor, or a loss of engine oil pressure.

MEDICAL AND PATHOLOGICAL INFORMATION

A postmortem examination of the pilot was conducted under the authority of the Alaska State Medical Examiner, 5700 E. Tudor, Anchorage, Alaska, on June 14. The cause of death for the pilot was attributed to multiple impact injuries, and drowning.

A toxicological examination was conducted by the FAA's Civil Aeromedical Institute (CAMI) on July 13. The examination revealed the presence of Dextromethorphan in the blood and urine, dextrorphan in the urine, and azacyclonol in the urine. Dextromethorphan is contained in numerous over-the-counter cough suppressants. Azacyclonol is the metabolite of terfenadine (Seldane), a prescription antihistamine. Neither substance was detected in an amount sufficient to be quantified.

TESTS AND RESEARCH

On July 1, an examination of the left engine was conducted at Alaskan Aircraft Engines, Anchorage. The parties noted in this report participated in the examination.

The engine contained silt and water, but otherwise sustained minor impact damage. Gear and valve train continuity was established upon hand rotation. The presence of lubrication was evident throughout the engine. The exhaust tubes had minor dents, but otherwise were not damaged.

The fuel servo inlet screen contained a small blob of a grease-like material at the base of the screen. The material appeared to be a type of fuel tank sealant or fuel system lubricant. It did not block the screen fitting orifice. The screen was otherwise free of contaminants. The fuel control's mixture arm was near the off position. The butterfly was open about 3/4 of its travel.

The waste gate controller was full open. The turbocharger turbine blades turned freely upon hand rotation, without any evidence of rotational scoring.

The mechanical fuel pump drive gear was intact and hand rotation produced a pumping action that produced a small amount of water/fuel. On a test bench, the pump produced 43.5 psi at 2,000 rpm.

The engine hydraulic pump drive gear was intact. A slight binding was felt upon hand rotation.

The oil sump screen, and the engine oil filter were free of contaminants.

The propeller governor housing had impact damage. The input shaft was bent.

The vacuum pump drive gear, and the internal block was intact. It contained silt and water.

The dual magneto contained silt and water. After cleaning, the magneto, and the ignition harness produced spark from all leads, both left and right sides.

The left engine propeller was removed and examined at Dominion Propeller, Anchorage, on July 2. While still mounted in the hub, blade angle measurements revealed that blade number one was 81.8 degrees. The blade was straight with scoring and aft curling at the tip. Blade number two was 86.2 degrees. It had scoring at the tip, the stop pin was bent, and it had slight spanwise bending opposite the direction of rotation. Blade number three was 81.3 degrees. It was free of any extensive scoring, but had a slight spanwise aft bend at the tip. The blade feather position is 82.0 degrees, plus or minus 1 degree. A considerable amount of grease was found in the hub. Air pressure was noted in the hub, but the pressure was not recorded.

Following disassembly, the propeller was sent to Hartzell Propeller Inc., Piqua, Ohio, and was examined under the supervision of an FAA inspector from the Vandalia manufacturing inspection district office (MIDO), Vandalia, Ohio, on August 16. Due to the lack of propeller damage, particularly at the base, the examination did not reveal conclusive evidence that the blades were actually in feather. Hartzell personnel indicated they have no reports that excessive grease in the hub has prevented a propeller assembly from feathering. They noted a feather check is a pre-flight requirement.

The left engine propeller control was also examined at Hartzell Propeller on August 16. Disassembly of the governor revealed the control arm was broken due to impact. The internal gears contained sand and mud. No indication of rotational scoring was observed on the internal gears. No mechanical defect was found.

The left engine fuel servo was removed for examination at Precision Airmotive Corp., Everett, Washington. The examination was supervised by an NTSB Senior Air Safety Investigator from the Northwest Regional Office, Seattle, Washington, and was conducted on July 21. No mechanical malfunction was noted during the examination.

The left engine turbocharger waste gate controller was removed for examination at Consolidated Fuel Systems Inc., Montgomery, Alabama. The examination was supervised by an FAA inspector from the Atlanta MIDO, Atlanta, Georgia, and was conducted on August 17. No mechanical malfunction was noted during the examination.

ADDITIONAL INFORMATION

The Yukon River conditions presented hazardous conditions for wreckage recovery. The operator attempted to locate the right wing and right engine on several occasions, with the last attempt just before the river began to freeze. The operator's insurance company provided funds to search for the missing parts.

WRECKAGE RELEASE

The Safety Board released the wreckage, located at Wicks Aircraft, to the owner's representatives on November 23. No parts or components were retained by the Safety Board.