The US Federal Aviation Administration should issue warnings to operators of Convair 580s to close shut-off valves of fuel tanks not being used during crossfeed operations, according to a US National Transportation Safety Board (NTSB) accident investigation report.

The board’s recommendation follows the investigation into the 13 August 2004 crash of a Convair 580 (N586P) about 1nm (2km) south of Cincinnati airport, en route from Memphis, Tennessee. The aircraft’s first officer was killed and the captain received minor injuries.

NTSB investigators say the Convair 580, operated as Air Tahoma flight 185 for DHL Express, was caused by “fuel starvation resulting from the captain’s decision not to follow approved fuel crossfeed procedures”.

Contributing factors of the accident include “the captain’s inadequate preflight planning, his subsequent distraction during the flight, and his late initiation of the in-range checklist”, says the report.

The NTSB further says “the flightcrew’s failure to monitor the fuel gauges and to recognise the airplane’s changing handling characteristics were caused by fuel imbalance”.

Investigators found no evidence of aircraft maintenance problems, flightcrew fatigue, insufficient fuel, structural deficiencies, or weather as factors in the accident.

During pre-flight procedures, the NTSB notes the captain’s “weight and balance calculations were not within take-off limits; therefore, he should not have allowed the airplane to take off”.

The board, however, notes the captain had miscalculated, and the aircraft’s weight and balance were in fact within acceptable limits.

Investigators say the captain continued to be “preoccupied during critical portions of the flight, and as a result, he did not monitor the fuel crossfeed operations, which resulted in a fuel imbalance and unusual airplane handling characteristics”.

This failure to monitor the crossfeed operations also meant the fuel gauges were not checked. The in-range checklist also was not started at the appropriate altitude, says the report.

NTSB investigators say during this time the crew missed numerous opportunities to notice the fuel crossfeed and imbalance.Following missed opportunities to correct the problem, “all of the fuel from the airplane’s left tank that was not used by the engines transferred into the right tank because the captain intentionally kept the right fuel tank shut-off valve open during fuel crossfeed operations, which was not in accordance with approved fuel crossfeed procedures”, the report adds.

The crash occurred during descent as the fuel in the left tank – which was providing fuel to both engines – “was exhausted because both engine-driven fuel pumps drew air from the left tank into the fuel system instead of fuel from the right tank, resulting in a dual-engine flameout”.

Besides fuel tank shut-offs during crossfeed operations, NTSB officials are also recommending that both the FAA and Canadian safety regulator Transport Canada require Convair 580 operators set left and right fuel boost pump output pressure settings on their aircraft to the same setting.

The board further reiterated its 1999 recommendation to the FAA to retrofit aircraft with independently powered cockpit voice recorders for help in accident investigations.

Source: Flight International