New fuel gauge standards aim to reduce the risk of commercial aircraft suffering fuel exhaustion by providing earlier warnings to flight crew about possible starvation.
Europe's safety regulator is proposing the modification of the CS-25 certification standard covering powerplant requirements - which only demands a fuel quantity indicator for each tank.
There is no requirement for a low fuel level alert, although many aircraft have such devices fitted. But the European Aviation Safety Agency (EASA) said: "They are not all independent or fault-tolerant from the normal fuel gauging system, and the alert level and setting point are not standardised."
Under the amended rule, aircraft would be required to have indicators showing the total quantity of usable fuel on board and the quantity in each tank, as well as a low-fuel cockpit alert for any tank that should not become depleted.
The alert must warn the crew when the amount of usable fuel in the tank reaches the level required to operate the engines for 30min, under cruise conditions.
In its proposal, EASA said that failure scenarios for analysis should include erroneous high fuel quantity indications and loss of fuel gauge information.
"The alert and the fuel quantity indication for that tank may not be adversely affected by the same failure," it added. "It should be demonstrated that no failure of the [quantity indicator] or total loss of the primary basic [fuel quantity] information would lead to the fuel low level alert not being correctly triggered."
The modification would also provide indications to pilots of hazardous conditions - such as abnormal transfer between tanks, trapped fuel or fuel leaks - which could result in a loss of fuel supply to the engines.
EASA attributed 30 accidents and 35 incidents to fuel-related issues over the period between 1970 and February 2011.
Some sixteen of them resulted in a total of 322 fatalities - 252 in accidents which would have been prevented under the new regulation.
Among them was the fatal Tuninter ATR 72 ditching in August 2005, which followed fuel exhaustion that went undetected because the indicator for an ATR 42 had mistakenly been installed.
EASA is accepting comments on the regulatory change until 24 October.
Source: Flight International
