8 December 2009
The purpose of this Advisory is to inform Owners, Flight Crew and Maintainers regarding safety concerns with certain fuel system configurations for the Kelowna Flightcraft - Convair 340/440 (580) model aircraft.
The report states the probable cause of the accident as, “…fuel starvation resulting from the captain’s decision not to follow approved fuel crossfeed procedures.”
Fuel Crossfeed and Transfer
The manufacturer’s approved aircraft Flight Manual (AFM), section: “EMERGENCY FUEL SYSTEM (CROSS-FEED) OPERATION” (EFSCO) procedure for an aircraft with a 1730 gallon fuel capacity states, “…Turn boost pump switch ON for tank being used and place the cross-feed switch in the ON position …Place the booster pump switch of the tank not being used to the OFF position…Move the fuel shutoff valve switch to CLOSED.”
It has come to the attention of Transport Canada Civil Aviation (TCCA) that some flight crews of the Convair 580, in an effort to balance their fuel loads, follow part of the EFSCO procedure. They do not close the shutoff valve for the tank not being used but keep the valve open. There is a common belief that fuel tank shutoff valves have a tendency to fail and if failed in the closed position, would prevent use of the fuel in the corresponding tank.
While carrying out this unapproved procedure to balance the fuel load, the fuel being pumped from the tank being used will be flowing through the open shutoff valve of the tank not being used, leading to a potential safety risk. This was the configuration set up on the accident aircraft, resulting in a significant fuel imbalance and eventual fuel starvation of the engines. The aircraft crashed one mile south of its destination destroying the aircraft and killing one flight crewmember.
TCCA recommends that directors of operations, chief pilots and instructors review the procedures contained in their company operating and training manuals and revise them as necessary to ensure the approved AFM cross-feed procedures are clear to the flight crew and highlight the importance of closing the fuel shutoff valve for the tank not being used.Prop-Jet Convair Bulletin PJCB 10-21
In 1969 Allison issued Prop-Jet Convair Bulletin PJCB 10-21 to, “…improve the service life of the aircraft fuel boost pump motor.“ The Instructional Bulletin allows for the installation of the same model pump but installed with a reduced output pressure in conjunction with an appropriate fuel low pressure switch.
The NTSB believes that the fuel system presently in use is acceptable and different boost pump output pressures do not constitute hazards by themselves. However, the NTSB concluded that the existence of different fuel boost pump configurations could allow fuel transfer when the fuel crossfeed valve is unintentionally left open. The Board is therefore concerned that these configurations, appearing since the issuance of Convair Bulletin PJCB 10-21, could increase the safety risk.
TCCA recommends that owners check the status of their Convair 580 aircraft fuel boost pump installation (i.e. pre or post Instructional Bulletin PJCB 10-21). It is recommended that both the left and right boost pumps be configured to the same output pressures specified in either the manufacturer’s approved maintenance manual or Instructional Bulletin PJCB 10-21.
For further information, contact a Transport Canada Centre, or Mr. Robert Dixon, Continuing Airworthiness, Ottawa at 613-952-4357, email firstname.lastname@example.org
For Director, National Aircraft Certification
Chief, Continuing Airworthiness