What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-5) During an experimental flight test to determine unusable fuel during level flight at maximum recommended cruise (FAR 23 section 959 and advisory circular number 23.959-1, appendix 1), the temporary, 21-gallon plastic fuel tank, located in the cabin, collapsed. The cabin was pressurized and the fuel tank was vented to atmospheric pressure. The tank collapsed due tot he external pressure, forcing approximately 15 gallons of fuel overboard. The deformation of the tank crushed the tank's internal aluminum suction tube assembly making the remaining fuel inaccessible. At this stage of the test, no usable fuel was present in the aircraft's standard fuel tanks. A subsequent off-airport landing was made on I-95.
As the FAA filed it
(-5) DURING AN EXPERIMENTAL FLIGHT TEST TO DETERMINE UNUSABLE FUEL DURING LEVEL FLIGHT AT MAXIMUM RECOMMENDED CRUISE (FAR 23 SECTION 959 AND ADVISORY CIRCULAR NUMBER 23.959-1, APPENDIX 1), THE TEMPORARY, 21-GALLON PLASTIC FUEL TANK, LOCATED IN THE CABIN, COLLAPSED. THE CABIN WAS PRESSURIZED AND THE FUEL TANK WAS VENTED TO ATMOSPHERIC PRESSURE. THE TANK COLLAPSED DUE TOT HE EXTERNAL PRESSURE, FORCING APPROXIMATELY 15 GALLONS OF FUEL OVERBOARD. THE DEFORMATION OF THE TANK CRUSHED THE TANK'S INTERNAL ALUMINUM SUCTION TUBE ASSEMBLY MAKING THE REMAINING FUEL INACCESSIBLE. AT THIS STAGE OF THE TEST, NO USABLE FUEL WAS PRESENT IN THE AIRCRAFT'S STANDARD FUEL TANKS. A SUBSEQUENT OFF-AIRPORT LANDING WAS MADE ON I-95.