We perform air pressure testing on all aircraft types to diagnose the entry and exit point of the fuel leak, all pressure testing is carried out IAW your specific AMM procedures. Quite often we perform preventative fuel leak maintenance which involves air pressure testing all fuel tanks prior to a fuel on leak check, this procedure is carried out towards the end of your maintenance check. This procedure helps prevent unknown fuel leaks from appearing when you're ready to hand the aircraft back to your customer & prevents any delays. Please remember we perform all tank entry maintenance on all types of aircraft.