FTW01LA049
FTW01LA049

On January 11, 2001, approximately 1614 central standard time, a Dehavilland DHC-6-300, twin-engine airplane, N824ED, was substantially damaged when it impacted trees and terrain during a forced landing following a dual engine failure during an ILS 34R approach to Meacham Airport, near Fort Worth, Texas. The airplane was owned by Twin Otter, LLC, of Gaithersburg, Maryland, and operated by Earth Data Aviation of Haggerstown, Maryland. Instrument meteorological conditions prevailed, and an instrument flight rules (IFR) flight plan was filed for the 14 Code of Federal Regulations Part 91 business flight. The commercial pilot and his two passengers were not injured. The cross-country flight originated from Alexandria, Louisiana, at 1315.

The pilot reported to the NTSB investigator-in-charge (IIC) that on the day prior to the accident, the airplane was fueled at Essler Regional Airport, near Alexandria, Louisiana, and flown to the Alexandria International Airport where it was placed in a hangar for the night. On the day of the accident, the flight departed Alexandria for Fort Worth, Texas. The passengers were planning to deplane at Fort Worth, and the pilot planned to continue the flight to Houston, Texas. The pilot stated that before starting a descent from 6000 feet msl, he performed the before landing checklist and switched to the NORMAL position on the fuel selector. The flight was cleared for the ILS 34R approach and as the airplane was approaching the point of glideslope intercept, both engines lost power. The airplane was vectored toward the Sycamore Airport; however, after exiting the clouds, the pilot realized that the flight could not make the airport. The pilot initiated a forced landing to a field, and during the landing roll, the airplane crossed a road, and the right wing struck a tree. Subsequently, the nose landing gear separated when it struck a dirt berm. The airplane came to a stop upright.

The pilot later reported that after reviewing the events that transpired, he determined that at the time of the dual engine failure, the fuel selector was selecting the aft tank, thereby feeding both engines from the aft fuel tank. He further reported that when both engines failed, he immediately switched the fuel selector to "Both" ("NORMAL").

The FAA inspector responding to the site found the aft main tank 1/3-1/2 full of fuel, and the forward main tank 90% full of fuel. The integrity of the right wing tank was compromised and fuel was leaking from the right wing. The left wing tank was found empty. Examination of the cockpit revealed that the fuel selector for the main tanks was found in the NORMAL position. The inspector reported that in the NORMAL position, the aft main tank supplies fuel to the left engine, and the forward main tank supplies fuel to the right engine.

According to the aircraft manufacturer, with the fuel selector in the NORMAL position, each engine is fed by an independent fuel supply, and in the absence of multiple failures, a double flameout would not occur, particularly with no prior indication, unless the fuel was contaminated. The manufacturer representative stated that "it is conceivable that there was a problem with the aft tank related to the ability of the ejector system to keep the collector tank full. A flapper valve stuck in the open position or an ejector system fault are the most likely candidates. These would result in a uniform fuel level in all the cells in the aft tank. Although the collector would not stay topped up, the low level fuel warning would illuminate with approximately 330 lbs of fuel instead of 75 lbs. In addition to the low fuel warning, the caution lights for both boost pumps would illuminate, indicating a loss of fuel pressure."

Examination of the fuel system, by the NTSB IIC and the FAA inspector revealed that the flapper valve was not stuck open, no faults were found with the ejector system, and the low level fuel warning light illuminated when tested. The fuel boost pumps were activated and fuel flowed from the fuel supply lines. The left and right airframe fuel filters and the left and right engine fuel filters contained fuel. No anomalies were observed during the examination of the fuel system.

A representative from Pratt & Whitney, under the supervision of the NTSB IIC, examined both engines. No anomalies were observed that would have precluded the operation of the engines.

The aircraft's flight manual directs the pilot to position the fuel selector to "NORMAL" prior to takeoff and for approach.

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