It may look unglamorous, but without this weather-beaten little yellow box, no growling could take place. The Trolley Accumulator ("Trolley Acc" to its mates) is a heavy duty 24v battery on wheels, for jumpstarting aeroplanes.
WR963 has her own batteries, but waking up 37 litres of cold and temperamental Griffon from weeks or months of slumber requires some serious grunt. This little yellow box delivers the necessary extra juice - provided we've remembered to to charge it up of course!
A thick lead connected to the batteries is plugged into a socket under the nose of WR963 prior to engine starting.