In Flight Fire, Emergency Descent and Crash in a Residential Area

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Causes

Post accident interviews indicated no one ever examined the aircraft (aircraft maintenance personnel) for the weather radar issue or took appropriate steps to remove the aircraft from service (DOM or Chief Pilot). The final safeguard for operation of an unsafe aircraft is the pilot pre-flight or walk around inspection. The maintenance forms had the discrepancy documented and a review by the pilots would have alerted them to the unresolved issue. This is another reason for having symbols in aircraft forms that give a quick reference to the status of the aircraft. According to the Chief Pilot, the ATP was notified of the issue and in person by the maintenance technician and the ATP dismissed the issue. The Commercial Pilot was not verbally identified about the discrepancy but responsible for determining the aircraft airworthy and should have verified the forms for any type of unresolved discrepancy. Neither of the pilot’s determined the weather radar discrepancy was an issue and accepted the aircraft with no troubleshooting or corrective action. The day before the accident, the aircraft flew an hour before the weather radar circuit breaker had to be pulled and the subsequent burning smell went away. The day of the accident, the aircraft was airborne for only 10 minutes before there was a reported problem. The accident occurred 2 minutes after the problem was identified. (NTSB, 2009)

A thorough examination was completed on the aircraft after the fire and damage but there was no way to accurately determine if the circuit breaker was reset for the weather radar. There is a checklist requirement during the pre flight to reset all circuit breakers which makes is possible that it was reset. Additionally, the aircraft was only airborne for 10 minutes before a problem started which is another indication it was reset during pre flight. There was evidence that a fire on the left side of the instrument panel had taken place. The door latch pins were not damaged upon investigating the wreckage. This indicates the door was unlatched in flight to potentially alleviate the smoke and possible heat that had occurred in the cockpit. The cabin door was also located 60 feet from the wreckage which means it came off before impact. According to the report the Safety Board concluded that the fire more than likely started by the weather radar wiring and was fueled by the fuel lines running in the same area. There was not another source that identified that could have started the fire. However, there was insufficient evidence to conclusively determine the origin of the fire.

The aircraft made a hard right turn before it crashed which indicates the pilots intentionally attempted to divert to an alternate landing site when they recognized that they would not reach SFB. The airplanes landing gear and flaps were not extended and the airplane was traveling at a high speed which indicates the pilots were not prepared for an emergency landing. This piece of evidence is hard to speculate. The pilots may have been distracted or in attentive upon initial smoke and fumes in the cockpit and banked while trying to troubleshoot the issue. The pilot’s more than likely lost situational awareness because of a pre occupation with the in flight fire. An in flight fire especially in front of the pilots and over their legs, and distracting causing the pilots to want to land as soon as possible. The Safety Board concluded that based on the evidence, it was not possible to definitively determine the events that led to the accident airplanes maneuvers away from SFB. (NTSB, 2009)

If general aviation pilots, maintenance personnel, and operators had a more thorough understanding of the potential hazards of a reset circuit breaker, they would be less likely to reset a tripped circuit breaker without knowing what caused that circuit breaker to trip.

Recommendations

Revise the SOP for multiple processes for the company. Develop detailed procedures for documenting aircraft forms & systems to identify not airworthy aircraft and steps to placard and collar circuit breakers. This system needs to be accessible to all required personnel and adequate training to understand how to operate and maintain the status and configuration of company aircraft. More thorough and continually updated guidance and information regarding maintenance and inspection of airplane electrical systems and wiring for general aviation maintenance personnel would increase the likelihood that they will be aware of current industry wiring-related concerns, such as deteriorated (aging) wiring; corrosion; improper wire installation and repairs; and contamination of wire bundles with metal shavings, dust, and fluids and would greatly increase the likelihood that their work will comply with current best practices. Identification, by an aircraft’s manufacturer or those responsible for post manufacture modifications, of which of an aircraft’s systems are critical to a flight (or to a realm of flight) would enable pilots to make better-informed decisions regarding which circuit breakers they should or should not attempt to reset before or during flight. Manufacturers should create a mission essential systems list that provides a go or no go indication to maintenance personnel and the pilots.

Provide training to pilots about the importance of doing pre flight checklist/inspections and established procedure to refuse aircraft that have potentially serious maintenance issues.

Develop a Safety Management System program to provide corporate flight departments a formal system of risk management, safety methods, and internal oversight programs that could improve safety.

Summary

Aircraft accident N501 is just one more example of how latent issues compound each other and ultimately lead to an incident or accident. From the maintainer having knowledge of the weather radar burning smell the day before the accident, the multiple layers in place to have leadership review maintenance discrepancies to the pilots doing a pre flight inspection before takeoff there were breakdowns. Inattention to maintenance procedures and understanding what systems can ground an aircraft can ultimately lead to these types of serious accidents.

References

NTSB. (2002, November 01). NTSB Aviation Investigation Manual. Retrieved from NTSB Investigation Process: http://www.ntsb.gov/investigations/process/Documents/MajorInvestigationsManual.pdf