Safety Pilot: Something's burning

Coping with electrical trouble

The AOPA Air Safety Foundation recently created a new Safety Brief to arm pilots with practical tips on handling in-flight electrical issues. Recommended reading for all pilots, it covers key points such as:

• Recognizing problems early
• Priorities when dealing with smoke or fire
• Tactics for in-flight troubleshooting
• Causes and consequences of smoke/fire
• “Squawking” issues for maintenance

The NASCAR Cessna 310 accident is a sobering reminder of how quickly an electrical problem can lead to disaster. Take a few minutes to read the Safety Brief to help ensure you never end up in a similar situation.

Bruce Landsberg is the president of the Air Safety Foundation.

An in-flight electrical fire is one of the worst emergencies that can confront a pilot. Fortunately, they are rare. Like many critical faults, it may start slowly at first and then build very quickly into an unrecoverable situation. The accident aircraft was a 30-year-old Cessna 310R, the only piston aircraft operated by the National Association for Stock Car Auto Racing (NASCAR) corporate aviation division.

According to the NTSB, this accident was all but certain even before the flight began. A casual approach toward a seemingly benign maintenance item turned deadly not only for the pilots, but also for people on the ground. It also shows how disregarding safety procedures that may be perceived as overly conservative or irrelevant can wind up costing lives, aircraft, and tens of millions of dollars.

Deferred maintenance

On the day before the accident flight, another company pilot had flown the Cessna and reported on a maintenance discrepancy sheet, “Radar went blank during cruise flight. Recycled—no response smell of electrical components burning, turned off unit—pulled radar [circuit breaker]—smell went away. Radar inop[erative].”

The pilot told investigators that upon landing, he documented and reported the discrepancy to NASCAR maintenance personnel, “leaving the white original page in the discrepancy binder in the airplane and providing the yellow copy to the director of maintenance [DOM], in accordance with the company’s standard operating procedure.” He also discussed the problem with the DOM and the aircraft’s mechanic. The original maintenance write-up was recovered at the crash site. The DOM was unable to find the yellow copy after the accident.

No technician looked at the aircraft, and the radar circuit breaker was not “collared” using a tie wrap to keep it from being reset. Additionally, there was no placard or sticker put in place to note the equipment was inoperative. At least one or more of these actions is required under FAR Part 91.213. The NTSB further determined that the night before the accident flight, NASCAR’s chief pilot telephoned the ATP who was to act as the safety pilot to advise him of the radar discrepancy. Moreover, a maintenance technician advised the ATP of the discrepancy in person on the morning of the accident flight. On both occasions, the ATP dismissed the issue as unimportant. It is unknown if he knew about the burning smell or just that the radar didn’t work.

The flight

On July 10, 2007, around 8:22 a.m., the Cessna 310R departed Daytona Beach, Florida, on an IFR flight plan to Lakeland, Florida. The weather was good VFR. Two pilots were on board—the pilot in command was a commercial pilot with about 270 hours, accompanied by the corporate ATP (more than 10,000 hours), who had been briefed about the discrepancy, in the right seat as a safety pilot.

About 8:32 a.m., shortly after reaching a cruise altitude of 6,000 feet, the ATP advised air traffic control that they had an emergency, stating, “Smoke in the cockpit, we need to land at Sanford.” The controller cleared the flight direct to Orlando Sanford International Airport (SFB) and issued a descent to 2,000 feet.

The last radio transmission was received at 8:33 a.m. and ended mid-sentence with the phrase, “Shut off all radios, elec[trical] .” This was also when the last transponder return was received, indicating that the master switch had been turned off. The Cessna was eight nautical miles northwest of SFB, turning toward the airport and rapidly descending. For the next 90 seconds primary radar returns showed the aircraft heading toward SFB.

The last radar return was recorded at 8:34:45 a.m., when the flight was about three miles northwest of SFB and descending through 1,200 feet agl.

The crash

The 310 crashed in a residential area about 0.7 nautical miles west of the last radar return. The NTSB report said that according to witnesses, “The airplane was traveling ‘extremely fast,’ was ‘very low,’ and its wings were ‘rocking’ as it descended. Just before impact, the airplane entered a ‘steep bank’ and made a sharp turn to the west. Several witnesses reported seeing smoke trailing from the airplane, and one witness stated, ‘Smoke was trailing from the port side.’”

The Cessna first hit some trees in a right-wing-low attitude about 65 feet agl. Then, 270 feet beyond the first tree strike, it struck a palm tree about 20 feet agl, grazed the corner of a house, and crashed into the next two houses along the street. The massive fire that ensued resulted in the deaths of both pilots, three people on the ground, and four serious injuries to people on the ground.

Forensics 1.0

The forensic analysis that follows many fatal accidents is painstaking. Not surprisingly, the findings also heavily depend on who’s doing it, which we’ll get to shortly. Much of the fuselage, wings, instrument panel, some avionics, seats, and the right engine were found in and around the second and third homes.

Although most of the airplane was destroyed during the post-impact fire, NTSB investigators noted discolorations or soot deposits on airplane parts that were not part of the ground fire. The underside of the instrument panel glare shield and deck skin, located on the roof of the first house, showed thermal damage with discolored, charred paint and soot deposits, all indicative of an in-flight fire. The unburned cabin door found some 60 feet away from the main wreckage had numerous soot deposits on the interior side, indicating the pilots opened the cabin door to vent smoke.

Most of the electrical system components and associated wiring were severely damaged or destroyed, and little electrical insulation remained. Examination of some small sections of recovered wiring and one partial wire bundle found among the fuselage wreckage showed characteristics of strand fusing and globules of re-solidified copper. According to the NTSB, “That may be consistent with electrical arcing and/or exposure to heat from the post-impact fire. Too little remained to positively identify which systems those wires were associated with or to determine when the observed characteristics were created.”

Flight instruments, avionics, controls, switches, and circuit breakers had severe post-impact fire damage and yielded no usable information regarding their pre-accident configuration or condition. Parts of the weather radar and some attached circuit boards exhibited severe impact and thermal damage; however, there was no evidence of an electrical fault.

The aircraft was built in 1977 and at the time, the FAA allowed the use of polyvinyl chloride (PVC) insulation, but it has not been used in decades since it gives off incapacitating fumes when burned.

Forensics 2.0

As mentioned earlier, perception of fact is in the eye of the beholder. NASCAR, as a party to the investigation, came to a significantly different conclusion than the NTSB. In its filed comments, which are summarized for brevity, it was noted that:

• The fire did not originate in the radar unit (the NTSB concurred).
• The fire likely originated in wiring installed behind the panel by Cessna (the NTSB concurred on the likely location of the fire but could not determine which wiring was specifically at fault. NTSB further noted the aircraft was operated by multiple owners with numerous modifications over the years. A non-factory replacement radar unit and associated wiring was installed in 1988, so the conclusion that Cessna wiring was the source is speculative.).
• The factory-installed PVC wiring on the Cessna 310 was not in compliance with the CAR 3 regulations (the NTSB did not concur, noting that the rules allowed manufacturers to continue to use PVC in aircraft in which it was already being installed).

Probable cause

Summarized for brevity, the NTSB found that the radar anomaly the day before could easily have developed into a fire except that the pilot pulled the circuit breaker. A critical point for all pilots to note is that severe damage to the 310’s wiring harness may well have already occurred and the insulation may have been badly compromised. The accident crew most likely reset the breaker during the prestart checklist, following pilot’s operating handbook guidance that one reset is allowed.

By not following good maintenance procedures of examining the aircraft, possibly removing the radar, collaring the breaker, and making a log entry, the aircraft was not airworthy. If those things had been done, and the radar was not essential to safe flight as determined by the mechanic, the aircraft could have flown legally and safely. The accident crew was aware that the radar was inoperative but may not have understood that the wiring had been compromised, as evidenced by the burning smell. When power was restored to the affected circuit it took only a few minutes to develop into a major fire, and once adjacent wiring was involved, pulling circuit breakers and shutting off the master switch had no effect. Critical point: If you note any sort of burning smell, disable the circuit immediately. The aircraft has just become not airworthy and must be thoroughly inspected by a competent technician before flying again.

The existing guidance in POHs of the era and training of GA pilots has traditionally allowed one reset of a breaker after it has cooled. Current thinking, backed up by the tragic events here, is that if a breaker trips and it is not critical to flight, do not reset it—even once. More attention must be given to aging wiring by pilots, owners, and maintenance technicians.

“The National Transportation Safety Board determines that the probable causes of this accident were the actions and decisions by National Association for Stock Car Auto Racing’s corporate aviation division’s management and maintenance personnel to allow the accident airplane to be released for flight with a known and unresolved discrepancy, and the accident pilots’ decision to operate the airplane with that known discrepancy, a discrepancy that likely resulted in an in-flight fire.”

There was an addendum to the report filed by board member Robert Sumwalt regarding NASCAR’s shortcomings that is posted on the AOPA Air Safety Foundation’s Web site. It is sobering reading and recommended for all pilots. NASCAR has filed a multi-million-dollar lawsuit against Cessna alleging improper wire was installed on the 310R.