ATM Modernization, Business & GA, Commercial

Safety: Tales of Troubleshooting

By David Evans | November 1, 2003
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The video screens mounted beneath the passenger overhead luggage bins in the cabin were retracting and extending continuously. They created a vivid image of an aircraft electrical system going out of control–and the whole notion of flight safety is that everything’s under control. Video screens taking on repetitive movement akin to that of a mental patient’s compulsive rocking is not conducive to passenger reassurance.

This particularly striking image of cascading electrical failure was taken from a review of nearly 100 reports of in-flight smoke and fire events submitted by pilots and flight attendants to the confidential Aviation Safety Reporting System (ASRS) over a period from 2000 to 2003. Five events distilled from the lot illustrate the range of challenges faced by aircrews when the first wisps of smoke appear, the lights flicker or the instruments suddenly display problem messages. Aircrews then must shift gears from a routine mindset to the hyper-vigilance of coping with an emergency. Despite the differences between these reports, certain common themes emerge. First, the reports:

Case No. 1: False Faults

From a synopsis of the video screen episode described above: "[An] A320 in cruise at 39,000 feet declared an emergency and diverted due to right AC [alternating current] bus causing flickering lights in cockpit and cabin. First officer’s flight instruments intermittent and numerous ECAM [electronic centralized aircraft monitor] alerts."

This sparse dry wording does not do justice to the dramatic details of the captain’s narrative: "I began to notice the cockpit lights flicker as if there was a power interruption. There weren’t any ECAM messages associated with it. The purser called and informed us that the right side cabin lights were flickering on and off. Additionally, the video screens on the right side were retracting and extending on their own. At the same time the first officer’s navigation display and primary flight display flickered on and off (including moments of loss of flight data to the displays). The ECAM began to cycle messages about the No. 2 yaw damper, [air conditioning] pack control, pitch trim, FWC [flight warning computer], autopilot and possibly others."

At this point, some 30 nautical miles from the nearest suitable airport, the captain suggested an immediate diversion. "After donning our oxygen masks and completing the initial QRC [quick reference card] ‘smoke and fumes’ checklist, we began our descent and then declared an emergency," the captain’s ASRS report recounted.

The purser reminded the captain that a "deadheading" pilot was on board. In the ASRS report, the pilot said, "I had him come to the cockpit and help run the required checklists for us. I handed him the QRC/checklist card and the A320 flight manual to complete the current checklist and back us up on the approach and final checklist. The descent from FL390 to landing took about 10+ minutes." The landing was uneventful, the aircraft was taxied onto the ramp area and a normal shutdown was completed.

During a subsequent telephone interview with ASRS personnel, the captain said, "At no time during the event did the ECAM indicate this was a generator loss-of-phase problem." Maintenance personnel found a feeder wire pin in the firewall connector burned with evidence of severe arcing. The failure of the ECAM system to warn of a right bus intermittent loss of phase "was reported and discussed with the company."

Case No. 2: Hot Seat

This incident involved a DC-10 freighter in cruise flight. Smoke coming from the flight engineer’s seat filled the cockpit. The pilots declared an emergency and diverted for an uneventful landing at SLC [Salt Lake City].

Installed two days before the incident flight, the seat had been involved in a previous incident of smoke on a different aircraft. Initially, the fault was thought to be in the control switch, but that was found to be functional. The second suspected problem was the motor. The seat, according to the ASRS report, "has been removed for further investigation."

Don’t think this sort of problem is limited to cockpit seats. Note that more business and first-class passenger seats feature one or more electric motors, as well as extensive electronics and wiring associated with their built-in entertainment systems. Indeed, the ongoing proliferation of in-flight entertainment (IFE) systems increases the potential for in-flight electrical smoke and fire events.

Case No. 3: Muffled Voices

A Boeing 767 passenger aircraft was operating at cruise. The captain and first officer smelled an acrid, burning odor in the cockpit, which seemed to be emanating from an overhead panel and possibly from the rotatable "gasper" air vents in the vicinity. An emergency was declared, and the flight attendants were advised and told to review their procedures in case the situation worsened. A diversion to airport "X" was considered, but it was shut down with an electrical outage. The flight continued and landed uneventfully.

The point of this vignette concerns emergency gear. Per the flight manual, the pilots donned their oxygen masks. As the ASRS report recounted, "In actual operation [this protective equipment] became very cumbersome and distracting to cockpit communications. It was almost impossible to really understand what the other crew member was saying and ATC [air traffic control] seemed to have a problem understanding us."

Perhaps smoke masks should incorporate a throat microphone. The lack of progress evidenced by this recent account is discouraging. In a 1986 incident involving spilled acid and fumes on a B727 freighter, the crew complained about the smoke goggles and emergency masks "as a detriment to…communications," according to the National Transportation Safety Board (NTSB) incident report.

Case No. 4: Sniff Test

An A320 during climb out of Los Angeles International Airport [LAX] experienced multiple circuit breaker trips and detectable cockpit smoke. From the captain’s narrative: "I looked back at circuit breaker panel and saw static, PHC [probe heat computer], angle of attack, pitot, TAT [total air temperature], DHC3 [dynamic host configuration] were popped out. I took aircraft over and had first officer try to call maintenance controller. Shortly after we smelled and saw electric smoke in cockpit. I declared [an] emergency, asked for clearance back to LAX."

The ASRS report continues: "ATC asked if I would go to Long Beach. It looked like low overcast at Long Beach. LAX was VFR [visual flight rules]. I said LAX, ASAP [as soon as possible]. Light smoke was gone, so I had FO [flight officer] lift his mask up to see if he smelled smoke. The smoke and burning smell were gone. I told flight attendant what had happened, that everything seemed OKAY, and we would return to LAX for a normal overweight landing," the ASRS report continued.

Here is one of the reporting pilot’s principal concerns: "With oxygen mask on, the sun’s glare on the mask made it very hard to see the [autopilot selector panel, normally on the A320 glareshield], the FD [primary flight display], and the ND [navigation display]."

Case No. 5: Hide and Seek

This situation involved a B777 on an overwater international flight that was forced to divert because the main ship’s battery overheated. A recently retired B777 captain who read this account said he’d rather have to deal with an engine failure, as there are at least established procedures to cope with that event.

While the aircraft was cruising at 37,000 feet, the EICAS (engine indication and crew alerting system) announced that the main battery was overheating. This was a status message, with no specific actions required by the crew. Using satellite communications, the pilots discussed with maintenance the "lack of information to deal with the message," including the battery’s location. Maintenance advised it was located in the electronics and equipment (E&E) bay, located under the cockpit and accessed through a hatch. With the first officer flying the jet, the captain elected to climb down into the E&E bay and visually check the battery. He found the battery warm and noted that "all appears normal."

The flight crew made another call to maintenance, this time to discuss ways of dealing with the EICAS message, should it occur again. "Maintenance suggests if it happens again, pull CB P320 K-9 main battery. Believe situation under control. Continue [to] monitor electrical page [which shows slight discharge]," the ASRS account continued.

A short while later, the main battery overheat message appeared again on the EICAM status page. Due to the rapid rise in current, from 26 amps to 62 amps, the captain again was forced to descend into the E&E bay, this time to pull the circuit breaker whose location he had confirmed on the first foray. "No time for PBE [portable breathing equipment]," the captain noted.

Descending into the bowels of the E&E bay, he found the battery emitting smoke and promptly pulled the circuit breaker. Even so, the battery overheat message continued to display.

Back in the cockpit, a mayday call was radioed to the nearest suitable airport. Touchdown was normal and the aircraft was stopped on the runway.

"Fire crew checked aircraft with infrared [sensors], and visual [inspection] of battery in compartment OKAY," the captain recalled. The airplane was taxied to the gate and the passengers were unloaded. Maintenance later swapped the APU [auxiliary power unit] battery with the main ship’s battery, which was still hot enough to burn the technician’s skin.

For this captain, the problem was plain in his account to ASRS: "The lack of information in the flight operations manual on battery overheat procedures and the total lack of circuit breaker location charts should be corrected. The first message was a low-level status message that required no action by the crew. No procedures were found in the flight operations manual on an overheated battery and no circuit breaker location charts are carried in the cockpit any more."

Common Themes

From these abbreviated accounts, consistent cautionary themes emerge:

  • First, events progress quickly from the first indication of a problem to an emergency landing. Overweight landings are frequent.

  • Second, in situations with smoke or fire the crew workload can get high quickly. The presence of a third pilot can help greatly. Conversely, the two-pilot cock-pit can devolve into a "one-man band." In this age of electrically actuated and secure cockpit doors, with the captain in the E&E bay and possibly unconscious, and an electrical problem that has rendered the cockpit door’s electric lock inoperative, well, one better hope the autopilot is up to flying solo.

Can’t happen, you say? It already has. A door lock solenoid got fried last April on a B747. And the captain of the Swissair MD-11 that crashed in 1998 from a runaway electrical fire was out of his seat at the moment of impact, likely driven out by falling debris from the fire overhead.

  • Third, electrical failure and fire compromise the "trust your instruments" ethic drilled into every pilot. Rather, "trust but verify" is perhaps the more appropriate guidance. Instruments malfunction, flicker, blank out and give false or possibly misleading readings. The erratic pattern of failures can confound troubleshooting, Of course, seemingly unrelated system indications can be a symptom of cascading failure, as electrical arcing and fire eat through bundles of wiring or closely packed avionics.

  • Fourth, the potentially dire implications of ECAM or EICAS "advisory" messages may need to be reconsidered. The seemingly benign indication that something is wrong is about as useful as the fleeing zoo keeper’s warning that "an animal" has escaped. There’s the visitor left in the open with his wife and four kids, wondering just how bad the situation really is. An "advisory" message (the step before a "caution") should not develop rapidly into a May Day scenario.

  • Fifth, circuit breakers that cannot be located quickly are a hazard, extending the dangerous time that power can feed an electrical malfunction or fire.

  • Sixth, personal protective equipment may not be designed for user-friendly optimal use at the very time when protected breathing, vision and good intracrew and external communications with the ground are critical. The potential for "long-range intercom" is increased, wherein a pilot mistakenly radios a message meant for fellow aircrewmen. Recurrent training may need to be more realistic, to include forcing aircrews to communicate while wearing their breathing equipment.

  • Seventh, never trade prudence for luck. Do not descend into the smoky bowels of an E&E bay without first donning protective breathing equipment.

  • And eighth, when procedures arelacking, pilots must necessarily fall back on their knowledge of aircraft systems. Sound systems training can help prepare pilots for troubleshooting. A failing electrical system cannot be expected to have the integrity to drive the ECAM or EICAS warning system to "tell on itself." The situation is analogous to the fire truck that is itself on fire—only now at 37,000 feet.

Pilots may be back to "20 guesses" about the nature of their problem. There’s a difference, though, between a wild guess and an informed guess.

David Evans can be reached by e-mail at [email protected].

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