Potential In-Flight Fire Events Occur Daily; Many in Inaccessible Areas

Air Safety Week, April 24, 2000

"Crews don't have the diagnostic tools to locate the sources of smoke and fire."

Jim Shaw, line pilot and manager, Air Line Pilots Association in-flight fire project

DAYTONA BEACH, Fla. - If a pilot's greatest fear is an in-flight fire, aircrews in the U.S. airline industry are facing this frightening specter an average of three times a day. In one out of every three of these cases, pilots were sufficiently concerned to execute a precautionary landing.

More than 960 smoke and in-flight fire events were recorded in 1999. They triggered more than 350 unscheduled landings. In many cases, evidence of electrical arcing was discovered. After routine repairs, the aircraft were returned to service. Even if these events were trivial, although many were not, safety was affected. According to Jim Shaw, manager of the in-flight fire project for the Air Line Pilots Association (ALPA), the rate of one unscheduled landing per day compromises safety. "Every day there's at least one pilot and crew landing at an airport they are not familiar with," he declared. Shaw presented his findings at the Society of Automotive Engineers (SAE) "Advances in Aviation Safety" symposium.

Even at half the rate, Shaw's numbers are staggering. They result from a compilation of Service Difficulty Reports (SDRs) in the first 10 months of 1999. To be sure, this period of time covers the months following the Sept. 1998 fatal crash of Swissair Flight 111, in which an out-of-control electrical fire on the accident MD-11 is the primary suspect. Pilots, sensitized in the wake of the Swissair disaster, may have been landing their aircraft with unusual alacrity at the first whiff of a strange smell or the distinctive odor of an electrical malfunction. The dread is universal, as evidenced by a recent article in a Canadian publication for bush pilots.

Many events not reported

Pilot anxiety may be only a partial explanation. Shaw offers another, more chilling point: even though the SDR database represents the richest lode of such information, it may represent a significant undercount of actual events. For example, one SDR report cited "several air returns with smoke odor" (e.g., unscheduled landings) for the affected airplane. In addition, under U.S. regulations concerning Immediate Notification (49 CFR 830.5), operators are required to submit reports of in-flight fires, irrespective of the outcome. However, smoke without fire is not a reportable event, despite the folk wisdom "where there's smoke there's fire." Consequently, the Federal Aviation Administration's (FAA) incident database contained only about 1/7th the number of reports Shaw discovered in the SDR database. Of 155 SDR-reported events that necessitated an aborted takeoff, return to the block, emergency descent or unscheduled landing, only 21 such cases were found in the FAA incident database for the same time period.

For these reasons, Shaw believes his tally represents "minimum numbers," and that the actual count "can reasonably be presumed" to be greater.

Sam Holoviak, a pilot who also is a member of ALPA's central air safety committee, observed with the vivid memory of personal experience, "The sound of a popped circuit breaker raises the hair on the back of your head." With this observation in mind, highlights of Shaw's findings should raise hair on the backs of many heads:

High numbers. An average of about 100 smoke and fire-related events is being recorded per month, or roughly three per day. An SDR database search based on entering the words "Smoke and not False Warning" for the Nature of Condition, and the words "insulation or wiring, and char or burn or short" in the Summary turned up 964 events over the 10 months from Jan. 1, 1999 to Nov. 2, 1999. Only 12 reports mentioned "fire," but flames in a hidden area (e.g., behind a panel, under the floor) would more likely be recorded as "smoke." High temperatures. Most events involved high temperatures: 578 out of the 964 total. A high-temperature event was subjectively defined as one involving reference to smoke from a solid material or an electrical overload, short, bearing seizure, or whatever resulting in a popped circuit breaker. A second category involving air contamination was defined as a possibly combustible event involving smoke or mist appearing to result from leakage of oil or hydraulic fluid into the ducting (i.e., an "air contamination event."). Some 60 percent of the events met the "high temperature" definition.

Mostly electrical. Of 392 events that were categorized, more than 300, or 80 percent, related to aircraft electrical systems and components. For example, an overheated and smoking fluorescent light ballast was logically coded as an electrical malfunction. On the other hand, smoke wafting out of an air duct was not automatically presumed to be electrical in nature. In order of descending frequency, the following abridged list of failures illustrates the range of reports:

Description  Count  Description      Count
Fan          68     Connector        12
Wire         48     Circuit breaker  8
Light        27     Battery charger  4
Coffeemaker  17     Control panel    3