On November 9, 2013, about 0800 Pacific standard time, a Firefly Balloons, Inc., Firefly 10, N1623L, experienced a fire after landing near Temecula, California. D&D Hot Air Ballooning was operating the balloon under the provisions of 14 Code of Federal Regulations (CFR) Part 91. The airline transport pilot (commercial lighter-than-air balloon pilot) and four passengers sustained serious injuries; five passengers were not injured. The balloon was not damaged during the accident sequence. The local sight-seeing flight departed Temecula about 0700. Visual meteorological conditions prevailed, and no flight plan had been filed. A passenger reported that the balloon had landed after a 1-hour flight, and some passengers disembarked. The remaining passengers stayed on board as the operator moved the balloon toward the retrieval trailer, and sat it on the trailer. The pilot shut off one of the two burners. A passenger reported smelling propane throughout the flight, and the smell was especially strong during retrieval immediately prior to a flash and a fireball erupting. The pilot provided a written statement. He stated that he shut off the pilot light of the burner, and took the burner down from the flight position to put it in the storage bag attached to the side of the basket. While putting the burner in the bag, he bumped the blast valve, and propane came out of the burner. The propane ignited, but he did not know what the ignition source was. Burner Exams A Federal Aviation Administration (FAA) inspector and the National Transportation Safety Board investigator-in-charge supervised examination of the two burners, and a detailed report is part of the public docket for this accident. Serial Number 836 A visual examination determined that the hoses were about 9 years old. The main burner hose had minor cracks, but was not leaking. The pilot valve hose had minor cracks, but was not leaking. Utilizing a soapy spray solution, it was determined that Fire 2 hose had a minor leak at the fitting, but it was not considered dangerous. There was some black residue, which propane leaves when leaking. Serial Number 856 The main burner hose fitting was loose and leaking slightly. The pilot valve hose was in good condition with no leaks. The Fire 2 hose was in good condition with no leaks. Both burners were individually hooked up to a test unit. The hoses displayed no anomalies. A functional test of each burner was completed with no anomalies noted, and shut down was unremarkable. Flight Manual Excerpts Section 3.6 Landing Just prior to touchdown 1. Make sure that the Trigger Valve (and/or fire 2 valve if in use) is firmly closed 2. Close the pilot light safety shutoff Action 2 is a precaution against possibility that pilot lights or accidental burning might damage the envelope or ignite anything at the landing site. Note that 2 commits the pilot to the landing and must be delayed until possibility of a missed approach has passed. After landing, bleed all fuel lines. 1. Make sure that all valves are firmly closed. 2. Check for safety before bleeding fuel lines. If necessary, postpone 3 until at a safe location. 3. Open the Trigger Valve and Pilot Light Safety Shutoff Do not leave the pilot light system pressurized for long periods of time, i.e. do not leave the system with the Pilot Light Valve open, and the Pilot Light Safety Shutoff closed for extended periods. 3.7 Pack up and Storage 3.7.2 Fuel System After assuring that no fuel is trapped in any line, close the trigger valve. Leave the Pilot Light Safety Valve in the open position. Before transport: 1. Dismount the burner from the burner supports 2 Adjust fuel losses so that they do not contact tanks, vibrate against damaging objects, or protrude enough to be hit and damaged in travel. Chord or leather lacing may be used to secure hoses. The FAA inspector interviewed the pilot, and noted that the pilot did not follow the instructions in the FM. The pilot did not shut off the appropriate valves or bleed the system of gas after the pilot light was extinguished.