Saturday, May 13, 2017

Airplane Factory Sling, N511NG, Sling Flying Club LLC: Accident occurred April 29, 2014 near Barstow-Daggett Airport (KDAG), San Bernardino County, California

The National Transportation Safety Board did not travel to the scene of this accident. 

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Riverside, California
The Aircraft Factory; Torrance, California

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Investigation Docket - National Transportation Safety Board: https://dms.ntsb.gov/pubdms

Aviation Accident Data Summary - National Transportation Safety Board: https://app.ntsb.gov/pdf

Sling Flying Club LLC: http://registry.faa.govN511NG

NTSB Identification: WPR14LA177
14 CFR Part 91: General Aviation
Accident occurred Tuesday, April 29, 2014 in Daggett, CA
Probable Cause Approval Date: 03/23/2017
Aircraft: AIRPLANE FACTORY (PTY) LTD THE SLING, registration: N511NG
Injuries: 1 Serious, 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The sport pilot and flight instructor were approaching the destination airport at the conclusion of a night cross-country flight in the light sport airplane. The sport pilot stated that, about 10 miles southwest of the airport, they could clearly see the airport lights and began a visual descent from 5,500 ft mean sea level. During the descent, the airplane collided with terrain about 5 miles from the airport and came to a stop. The sport pilot egressed and called for emergency services. 

Postaccident examination of the airframe and engine revealed no mechanical anomalies that would have precluded normal operation. Visual meteorological conditions were present in the area with visibility of 10 miles. Astronomical information showed that moonset had occurred about 3.5 hours before the accident. The accident occurred in a very sparsely populated area of high desert, with no ground lighting. The terrain and dark night conditions would have prevented both pilots from maintaining a visual reference to the terrain. Examination of the airplane’s Electronic Flight Information System (EFIS) revealed that the aural terrain warning function was not enabled, though the system still depicted a moving map display with terrain information. If the aural terrain warning function had been enabled, the pilots would have been alerted, and action could have been taken in sufficient time to maintain terrain clearance.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
The pilots’ failure to maintain clearance from terrain while operating in dark night, visual meteorological conditions. Contributing to the accident was the pilots’ failure to enable the aural terrain warning system.

HISTORY OF FLIGHT

On April 29, 2014, at 2355 Pacific daylight time, an Airplane Factory Sling, N511NG, impacted mountainous terrain 5 miles southwest of the Barstow-Daggett Airport, Daggett, California. The certified flight instructor was seriously injured, and the sport pilot being instructed received minor injuries. The airplane was registered to, and operated by, the Sling Flying Club under the provisions of 14 Code of Federal Regulations Part 91, as an instructional flight. Night visual meteorological conditions prevailed for the flight, and no flight plan had been filed. The flight originated from Torrance, California, about 2130.

The pilot who held the Sport Pilot certificate stated that they were about 10 miles southwest of the Barstow-Daggett Airport, and they could clearly see the airport lights. They had started their descent out of 5,500 feet mean sea level (msl) and were planning their entry into the airport traffic pattern when they suddenly impacted terrain twice and then came to full stop. The sport pilot secured the airplane's electrical equipment and fuel system, egressed the airplane, and attended to the CFI. He then called for assistance using a mobile phone.

The Daggett ASOS (automated surface observing system) recorded at 2350 clear sky, visibility 10 miles, and wind from 260 degrees at 3 knots. Astronomical information shows that moon set had occurred at 2019.

The accident occurred in a very sparsely populated area of high desert in Southern California, and that dark night conditions prevailed.

WRECKAGE & IMPACT INFORMATION

The airplane rested on its belly, positioned on a down hill slope of the east side of the ridge. The sloping desert terrain descends to the desert floor 2,000 feet below. The landing gear of the airplane had separated from the airframe at the initial collision with the ridge line. The wings, engine, and tail remained fully attached to the fuselage. The wreckage was recovered and transported to a secure facility in Phoenix, Arizona for further examination.

The airplane wreckage was examined on May 13, 2014, by the NTSB Investigator-in-Charge. The fuselage was placed on a stand. The wings and engine had been removed from the fuselage by recovery personnel for the purposes of transportation. The engine was placed on a work bench. Flight control continuity was established from the cockpit to the ailerons, elevator, and rudder. The flaps were in the retracted position. The leading edges of both wings exhibited damage. The inboard section of the right wing exhibited hydraulic deformation along the front of the fuel tank. Engine control cables were traced from the cockpit to the firewall where the cables had been cut by recovery personnel.

The airplane was equipped with two MLG Avionics Stratomaster Voyager Electronic Flight Information System (EFIS) displays, one positioned on the instrument panel in front of each cockpit seat. Aircraft power was applied to the EFIS displays. The display on the left side of the instrument panel powered up but the control buttons had been damaged and did not function. The display on the right side of the instrument panel powered up and the control buttons functioned appropriately. The display had been in night mode, which was changed during this exam to day mode for easier viewing. Various menus were displayed until the Terrain Warning setting menu was located. Once on that menu page, it was observed that the Terrain Warning box was not checked. The Collision Warning menu page displayed that the Collision Warning box was checked.

A visual examination of the engine revealed no holes in the engine case, no oil leaks, all 4 cylinders were attached to the engine case, exhaust manifold and induction manifolds both in place on the engine. The propeller hub was attached to the crank shaft flange. The top spark plugs were removed, all exhibited electrodes light gray in color with no mechanical damage. The coloration and condition of the spark plugs were consistent with normal operation per the Champion Check-A-Plug chart (AV-29). The engine crankshaft was rotated by hand. Thumb compression was achieved on all cylinders, and the valve rockers were observed to move in concert. Both left and right carburetor bowls were removed. Both bowls contained undamaged floats and no fuel was observed. The propeller was a Whirlwind 3-bladed composite propeller. Two of the three bladed remained attached to the propeller hub, and all three blades exhibited leading edge damage.

Examination of the cockpit shoulder harnesses revealed that the anchor cables for both pilot positions had separated in overload. The anchor cable separation was documented and the documentation was provided to the airplane manufacturer. The manufacturer updated the design and specified a larger diameter cable to be used for the shoulder harness anchor points.

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