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Pilots warned of carburettor icing risk

Carburettor icing likely resulted in the engine failure that led to the crash of an amateur‑built Van’s Aircraft RV-6 two-seat aeroplane. Tragically the pilot and passenger died in the accident.

Amateur-built Van's Aircraft RV-6, two-seat aeroplane, registered VH-TXF

On 14 September 2014 the aircraft, operated in the ‘Experimental’ category, was approaching Mudgee Airport after departing Dubbo Airport, New South Wales about 25 minutes earlier.

The pilot approached from the north-west and conducted a non-standard circuit entry including an orbit to the south of the airport. Prior to turning onto the downwind leg of the circuit, the aeroplane descended to about 600 ft above ground level. Witnesses stated the pilot conducted a tight left turn onto final approach at a slow speed and low height. Witnesses also recalled hearing the aircraft’s engine ‘splutter’ and then go silent during the turn, followed by a ‘rev’, and then again silence.

Pilots of aircraft fitted with a carburettor are advised to check the forecast weather conditions and consider the risk of carburettor icing prior to each flight.

The aircraft continued its high angle of bank left turn and then collided with terrain about 300 m south-west and short of the runway threshold. The pilot and passenger were fatally injured and the aeroplane was substantially damaged.

The ATSB found that during the turn onto final approach to land, the aeroplane’s engine ceased operating. The aeroplane’s airspeed before the engine failure was within about 0.5 kt of the estimated stall speed during the high-bank turn. After the engine failure, it is likely the aeroplane entered an aerodynamic stall. The associated loss of control was not recovered and the aircraft continued in the turn until it collided with terrain.

The ATSB also found that the engine failure was probably due to carburettor icing. No defects were identified that would have precluded normal engine operation prior to the accident, and uncontaminated fuel was being supplied to the engine at that time. However, the environmental conditions at the time of the accident were conducive to serious carburettor icing at descent power, and the pilot-operated carburettor heat control was found in the OFF position.

The ATSB also found that the aeroplane’s weight was higher than the design limits. However, the effect of this weight on aircraft performance was not considered to have contributed to the accident.

The aeroplane was not required to be, and was not fitted with an angle-of-attack indicator or stall warning device.

Safety message

All pilots of aircraft fitted with a carburettor are advised to check the forecast weather conditions and consider the risk of carburettor icing as a result of those conditions prior to each flight.

Although amateur-built aeroplanes operated in the Experimental category are not required to be fitted with a stall warning device, owner-pilots should consider the benefits of such devices as a last line of defence against the inadvertent approach to, or entry into an aerodynamic stall.

Read the full investigation report AO-2014-149

 

rId34 Carburettor icing probability chart.jpg

 
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Last update 28 January 2016