Don’t Reset That Breaker!

The Cessna 310R departed Daytona Beach International Airport at 8:22 a.m., on a trip to Lakeland, Florida. The commercial pilot in the left seat was acting as pilot in command, while the ATP-rated pilot in the right seat functioned as a safety pilot. The NTSB report states that about 10 minutes later, shortly after reaching their cruising altitude of 6,000 feet, "the ATP contacted air traffic control to declare an emergency, stating, 'smoke in the cockpit, we need … to land at Sanford.' " The controller cleared the airplane to proceed directly to Sanford and radar data confirmed they turned towards Sanford and started a descent. A few seconds later, at about the time the last transponder signal was received from the airplane, controllers heard a partial transmission with the phrase, "shutoff all radios, elec[trical]," which was consistent with the inflight fire or smoke emergency procedure in the Cessna 310R Pilot Operating Handbook.

At that point the airplane was about eight nm northwest of the airport, turning towards the airport and descending rapidly. Primary radar returns recorded over the next minute and a half showed the airplane continuing towards Sanford. The NTSB report states that several witnesses observed the airplane traveling very low and extremely fast. They said that its wings were rocking and smoke was trailing from the port side. The airplane then entered a steep bank and crashed in a residential area several miles from the airport. Both pilots were killed, along with three people on the ground. Four other people on the ground received serious injuries.

The NTSB reports that "the airplane was fragmented and severely burned," but "the investigators observed some discolorations and/or soot deposits on airplane parts that were not directly exposed to the post-crash fire." This included the instrument panel deck skin, which was located outside the post-crash fire area but showed signs of thermal damage, including discolored primer paint, patches of charred and bubbling paint, and soot deposits. The cabin door, which was found about 60 feet away from the main wreckage, was unburned and the latching pins were not damaged. However, there were soot deposits trailing across the lower portion of the interior side of the door from an area that would have been near the lower edge of the instrument panel. Investigators said these indications were "consistent with the pilots having opened the cabin door to vent smoke during an inflight fire."

The flight instruments, avionics, controls, switches and circuit breakers were severely damaged in the post-impact fire and yielded no usable information regarding their configuration or condition prior to the accident. However, the NTSB discovered that on the day before the accident, another company pilot flying the same airplane had turned off the weather radar and pulled the related circuit breaker in response to a weather radar system malfunction and a burning smell. The burning smell went away and the pilot flew the airplane for over an hour without any other problems. After the flight he noted the incident in the airplane's maintenance discrepancy log, and placed the maintenance binder with a copy of the discrepancy report on the throttle quadrant. He provided another copy to the director of maintenance along with a verbal briefing. He also personally reported the problem to the maintenance technician who had primary responsibility for the airplane.

The 5 amp circuit breaker for the radar was located on the bottom row of the main circuit breaker panel, with associated wiring located along the left cockpit sidewall. Further investigation showed that this is the location of the greatest concentration of wiring in the Cessna 310R, and that fuel lines are routed to instrument panel gauges through this area. The NTSB determined that the aviation director, director of maintenance and chief pilot of the company that owned the 310 discussed the weather radar discrepancy after it was reported, and the ATP had been "specifically advised of the weather radar discrepancy by a telephone call from the chief pilot the night before the flight, and in person by the maintenance technician who was responsible for the airplane the morning of the accident flight." However, no one further investigated the problem to determine its severity, the system was not deactivated, a collar was not placed around the circuit breaker to prevent it being reset, and a placard was not placed in the cockpit indicating the system was inoperative.

The NTSB report pointed out that it is common for general aviation pilots to reset circuit breakers during preflight preparations unless a breaker has been placarded or collared indicating it is out of service. In fact, the Cessna 310R Before Starting Engines checklist includes a step stating "Circuit Breakers-IN." The board concluded it was likely that one of the pilots reset the circuit breaker, reenergizing the faulty wiring and leading to an inflight fire.

For many years it was common practice to reset a popped circuit breaker once to determine if there really was a problem, or if it was just a transient event. This was considered a safe approach because the breaker should trip again if there really was a problem. A number of air carrier accidents such as the SwissAir MD-11 inflight fire demonstrated that wiring damage from a short circuit is cumulative, and resetting a tripped breaker even once can result in a fire. In January 2004 the FAA issued Advisory Circular AC 120-80, "In-Flight Fires," as recommended by the NTSB.

The advisory circular specifically states that "a tripped circuit breaker should not be reset in flight unless doing so is consistent with explicit procedures specified in the approved operating manual used by the flight crew or unless, in the judgment of the captain, resetting the CB is necessary for the safe completion of the flight." This information has been widely disseminated within the air carrier community. Many Part 121 operators provide the advisory circular to their pilots and have revised their operating handbooks and checklists with detailed instructions regarding which circuit breakers are considered essential and may be reset. In addition, air carrier aircraft typically use indicators or segregated placement of the breakers to indicate which breakers are critical.

The NTSB discovered that this information has not filtered down into the general aviation community. The Advisory Circular focused on transport category operations, so much of it does not apply to small airplanes. On top of that, the information in manuals and checklists provided by the manufacturers of general aviation airplanes "often directly conflicts with the guidance contained in AC 120-80." They also found a recent training article that advised a pilot to try resetting a tripped circuit breaker once after letting the breaker cool for a few seconds.

Studies of airline accidents have shown that a flight crew may have only 15 to 20 minutes to get an airplane on the ground if a hidden fire is allowed to progress without intervention, and fires that are allowed to spread into the aircraft's overhead area may become uncontrollable in 8 to 10 minutes. However, many of those fires started in a lavatory, galley or entertainment system far removed from critical flight systems, and there is considerable space and resources available to fight a fire on a large transport-category airplane.

As demonstrated by the 310 accident, the pilot of a small general aviation airplane may have much less time to respond to a fire. The cockpit is small and confined, with little room to move around, making it very difficult to access the fire. Even if it were possible to get access to the fire, there may not be anyone available to help fight a fire while the pilot continues to fly the airplane. Any fire is likely to adversely affect the pilot and passengers very quickly as smoke and fumes fill the cockpit. Opening the door or a window may only make matters worse by adding oxygen to the fire, causing it to burn faster.

Obviously a pilot should do everything possible to avoid a fire in the first place. Do not treat an open circuit breaker or burning smell lightly. Refuse to fly an airplane that has experienced an electrical problem unless it has been examined by a mechanic to determine if the airplane is safe to fly, and any system with a possible electrical problem has been rendered inoperable and placarded as such.

If a circuit breaker trips while in flight, do not reset the breaker unless you feel it is absolutely necessary for the safe completion of the flight. Since most general aviation airplanes will fly just fine with absolutely no electrical power at all, there really isn't much that is critical to flight. If you fly a glass cockpit airplane, make sure you are proficient in flying the airplane by the standby instruments. Carry a couple of flashlights on any night flights in case you need to leave the cockpit lighting off. If a fire does occur, realize it is an extreme emergency that may make it impossible to reach an airport only eight nm away. If there is any indication the fire is growing, such as increasing smoke or heat, don't try to make it to an airport, but get the airplane on the ground as soon as possible while trying to avoid damage or injury to people on the ground. You literally may only have a minute or two left before you are overcome by the smoke and heat, or the fire causes damage that makes it impossible to control the airplane.


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