What was found
(AUS) COCKPIT AIR INTAKE ILLEGALLY MODIFIED (SEALED OFF) PREVENTING AIR INTAKE INTO COCKPIT AND CAUSING LACK OF OXYGEN TO PILOT AND PASSENGER - TWO MONTHS PRIOR TO THIS INCIDENT THE PILOT SEALED THE COCKPIT AIR INTAKE OPENING LOCATED IN FRONT OF THE NOSE WHEELCOMPARTMENT WITH MASKING TAPE - TO COMPENSATE FOR THE AIR LOSS, THE PILOT WOULD OPEN THE LANDING LIGHT TO RECEIVE COOLING AIR INTO THE CABIN - BECAUSE THIS FLIGHT WAS GOING TO BE AROUND 9500 FT AND HEADING SOUTH (FROM NORTHERN QUEENSLAND) THE LANDING LIGHTWAS CLOSED CAUSING THE LACK OF AIR TO THE COCKPIT - UNAPPROVED PART/MODIFICATION