ASN Wikibase Occurrence # 216284
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| Date: | Wednesday 28 August 2002 |
| Time: | 20:25 |
| Type: |  Robinson R44 |
| Owner/operator: | Heli Express |
| Registration: | N7189T |
| MSN: | 0870 |
| Year of manufacture: | 2000 |
| Total airframe hrs: | 484 hours |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Winstanley Lake, about 40 miles east of Ketchikan, Alaska -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | Ketchikan International Airport,Ketchikan, Alaska (KTN/PAKT) |
| Winstanley Lake, Alaska | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
On August 28, 2002, about 20:25 ADT (Alaska Daylight Time), a Robinson R-44 helicopter, N7189T, sustained substantial damage during a collision with water, after an in-flight loss of control at Winstanley Lake, about 40 miles east of Ketchikan, Alaska. The helicopter was being operated by the pilot as a visual flight rules (VFR) personal flight under Title 14, CFR Part 91, when the accident occurred. The commercial pilot and the sole passenger received fatal injuries. Night visual meteorological conditions prevailed, and no flight plan was filed. The flight departed Ketchikan at 19:40 ADT.
During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 29, a flight service specialist from the Ketchikan Flight Service Station (FSS) said he had spoken with the pilot of the accident helicopter on the afternoon of August 28. He said the pilot told him he and his passenger were going to spend the night in a public use cabin at Winstanley Lake, and that they would return around noon on August 29. The pilot requested that in the event they did not return, he would like the FSS specialist to send someone to the lake to look for them in the event they were having trouble with the helicopter. When the helicopter did not return the following day, the FSS specialist, who was in radio contact with a charter pilot transiting the area of Winstanley Lake, asked the charter pilot to check the area of the lake for the helicopter. The charter pilot reported seeing the helicopter floating inverted in Winstanley Lake.
On August 30, the NTSB IIC spoke with the Juneau FAA flight standards aviation safety inspector (ASI) assigned to assist in the accident investigation. He said he was in Ketchikan on the night of August 28, and that the night was very dark due to the low clouds and intermittent precipitation. He said on August 29, he interviewed the line person at the Ketchikan airport who fuelled the accident helicopter during the evening of August 28. He said the line person told him that after fuelling the helicopter, the pilot said he and the passenger were headed for Winstanley Lake to spend the night. The pilot told the line person he would return to Ketchikan on August 29.
A Garmin model 196 portable GPS was found floating on the surface of the lake near the helicopter, and was identified as belonging to the pilot. The GPS was returned to the manufacturer, and a record of the accident flight's GPS track was extracted from the memory. The GPS recorded date, time, position, ground speed, heading, and altitude. Information was recorded as sequential data points, and time between data points varied from 1 to 16 seconds. The GPS track indicated the flight departed Ketchikan at 19:40 ADT, and followed a course southeast along the north side of the Revillagigedo Channel to Point Alava. From there the flight proceeded northeast along the west shore of the Behm Canal, crossing to the east shore via Smeaton Island and Candle Island. The Behm Canal is a saltwater canal off of the Pacific Ocean. Winstanley Lake is about 2 miles inland from the canal to the east, and has a surface elevation of about 390 feet msl. There is a creek that originates at the west end of Winstanley Lake, and flows to the canal.
According to the GPS information, upon reaching the mouth of the creek the helicopter initiated a circling climb to an altitude of 1,098 feet amsl, and then continued a cruise/climb to 1,268 feet amsl. Once across the ridge line at the headwaters of the creek, the helicopter descended toward Winstanley Lake. The GPS ground track indicates the helicopter followed the north shore of Winstanley Lake to the area where the destination cabin was located.
According to the data, during the last 5 minutes of the accident flight, the helicopter descended to about 35 feet above the lake in the vicinity of the public use cabin, maneuvered there for several minutes, and then reversed course. After the course reversal, the helicopter's ground speed and altitude increased, until the helicopter reached about 170 feet above lake level with a ground speed of about 15 mph. Seventeen seconds later at 20:25 ADT, the GPS track ended indicating a steep descent about 1,020 FPM (Feet Per Minute), to the lake level altitude, with a ground speed of 66 mph.
Winstanley Lake is located within the Misty Fjords National Monument Wilderness, which is prohibited for helicopter operations without permission from the National Parks Service (NPS). The pilot did not obtain permission from the NPS to operate the helicopter at Winstanley Lake. Winstanley Lake is bounded on the north by a ridge line with a summit elevation of 3,779 feet amsl, and on the south by a ridge line with a summit elevation of 3,355 feet amsl. The terrain around the lake is steep and heavily treed. The lake runs roughly west to east with a dogleg to the south at the eastern end. Public use cabins are located along the north shoreline. Usually there is a beach between the cabin and the lake, but due to unusually heavy seasonal rains, at the time of the accident, the lake's surface level was even with the tree line that surrounds the entire lake shore. The water of the lake contains algae that gives the water a black colour, and limits the visibility in the water to about 24 inches.
Poor weather conditions for several days after the accident kept the NTSB IIC from reaching the accident site.
According to statements and photographs received from Alaska State Troopers and rescuers who reached the accident site four days later, the helicopter was floating inverted on the surface of the lake, suspended from its inflatable emergency floats. Later inspection by an NTSB air safety investigator revealed the helicopter's manual inflation switch had not been activated. The switch was still armed, with the locking device in place.
After recovery from the lake, the helicopter was taken to a hangar in Ketchikan and inspected by investigators from the NTSB, FAA, and the manufacturer. The left side fore and aft skid cross tube mounts were broken. The portion of the nose forward of the front skid cross tube was torn away at the bottom, but still attached at the top. The mid section of the fuselage belly between the fore and aft skid cross tubes was buckled. The tail cone was bent downward about 45 degrees, 2 feet aft of the fuselage. The tail cone aft of the bend was relatively undamaged. All the major tail components with the exception of one tail rotor blade were relatively undamaged. The damaged tail rotor blade was bent inward about 40 degrees, 4 inches from the blade grip.
The nose exhibited major crushing upward and aft from the forward skid cross-tube to the nose. The floor pan was torn loose along a line parallel to the forward skid tube. The aft cabin area was intact. The main rotor pylon had forward flexing, while the transmission deck area exhibited downward flexing. The engine cage tubing was flexed down and forward. The tail boom was bent downward and twisted counter-clockwise (looking forward), about 2 feet aft of the fuselage.
The tail boom and tail section were relatively undamaged aft of the tail boom twist. One tail rotor blade was bent inward, about 40 degrees, the other blade was straight. The tail rotor gearbox, and all mechanical components and attachments to the tail rotor blades, were intact. The tail rotor drive shaft was intact forward to the twist in the tail boom. Tail rotor drive train continuity was established from the twist in the tail boom forward to the tail rotor pulley drive system. Rotational scoring from the tail rotor driveshaft was observed on the tail boom supporting structure where the tail boom attaches to the fuselage.
Both the engine and transmission/tail rotor drive pulleys were intact. The pulley drive belts were present and undamaged, although displaced from the pulleys. Mechanical continuity through the transmission to the main rotor head and blades was established. One main rotor blade remained attached to the rotor head. The trailing edge of the blade had span-wise compression folding. Both the top and bottom of the blade exhibited rearward flexing and bending, with the bending more pronounced near the blade tip.
The second main rotor blade was bent sharply upward about 3 feet from the blade grip, and severed. The missing portion of the second blade was not recovered.
The engine was intact, and no pre-impact mechanical anomalies were noted. Rotational transfer signatures were found on the front edge of the crankshaft-mounted cooling fan, the upper sheave pulley, and areas of the airframe where the pulley made contact.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain control of the helicopter in-flight due to spatial disorientation, which resulted in an uncontrolled descent and impact with the surface of a lake. Factors contributing to the accident were the high terrain surrounding the lake, and the lack of visual cues due to the dark night and low clouds.
Accident investigation:
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Sources:
1. NTSB Accident Number: ANC02FA108 at https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?EventID=20020910X01577&AKey=1&RType=HTML&IType=FA
2. FAA: https://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?omni=Home-N-Number&nNumberTxt=7189T
3. http://www.sitnews.us/Kiffer/CrashHistory/082507_fatal_crashes.html
4. https://newspaperarchive.com/fairbanks-daily-news-miner-sep-04-2002-p-13/
5. https://news.slashdot.org/story/02/09/04/2333216/rip-leonard-zubkoff
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 16-Oct-2018 01:10 | Dr.John Smith | Added |
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