shortspatula

I was having a debate with a friend of mine about false indications and I was wondering what people thought. It's very rare obvoiusly but there's been a couple of instances at our company to have false Engine Fire indications since sometimes the fire detection loops malfunction. It's a memory item to turn the engine off if you have the indication. One time the crew just turned it off right away to find out on the ground it was a false indication. Another crew actually investigated it because they didn't notice anything wrong other than the indiction, no smoke behind them as they turned, smooth running engine etc. What would you do? It's an obvious memory item, but based on your knowledge that they have failed before and if you don't notice anything abnormal should you just blindly turn off a perfectly good engine?

JohnBurke

To "turn off the engine?" Do you mean to retard thrust levers and cut off fuel while arming or activating fire switches or T-handles to cut off bleed, electricity, oil, fuel, and hydraulics and arm the fire bottles?

I have never heard of a procedure involving making turns to see if there's "smoke behind."

The reason that we have fire detection on an engine is because we may have no other indications.

Most engines utilize at least two fire loops, and include both fire and fault logic to aid in discriminating between a fire and a loop fault. There are various reasons for a high temperature in an engine nacelle or pylon area, which could be an actual fire, a bleed leak, etc. Accordingly, fire loops use logic to look not only at a given temperature, but a temperature rise, comparing the indications of both loops, the differences, if any, the time to reach a fire indication, and so forth. Most systems will identify a fault based on certain types of logic and use that to provide a valid fire or fault indication in the cockpit.

Swissair 111, a MD-11 is a good example of a crew that didn't take the fire indication seriously. It didn't involve an engine, but a fire which developed as the result of an onboard entertainment system. The crew could have landed the aircraft, but elected to fly over the water, away from the airport, to dump fuel and set up for the approach. Everyone died. It turned out to be the worst air disaster Canada has seen.

UPS 6 was close to Doha when a lithium fire developed on the main cargo deck of the B747-400. Rather than land in Qatar, they elected to attempt a return to Dubai, and crashed in the desert. These, and numerous other mishaps point to a very grave reason that we take fire warnings seriously. If we respond appropriately to a fire warning and it does turn out to be a false alarm, we can consider the old adage that it's far better to be on the ground, wishing you were in the air, than in the air, wishing you were on the ground.

In the older A model C-130's we had photo cells in the nacelles as fire sensors, and those could be activated by sunlight or a bright reflection from the ground, into the nacelle; I have had occasion when receiving a fire indication to make a 90 degree turn to change the angle of light into the nacelle, and noted the fire indication went out.

Having said that, if we get a fire indication and it goes away, we may have just seen our fire detection destroyed by fire...that doesn't mean it's a good time to call it a false alarm and press on. A valid fire indication with a memory procedure is not the time to play second guess. We do not attempt to turn and look for a smoke trail. That would be idiotic. We do not attempt to go look at the engine to see if t's really on fire. We follow the procedure for an engine fire, wheel well fire, lav fire, etc.

Some aircraft systems may show an overheat, rather than a fire, which is most often a bleed leak, and will involve shutting off bleed air, reducing power, and other steps to detemine the source and to stop the overheat condition.

To receive a fire indication and attempt to second guess it by making the dangerous assumption that it's a "false alarm" is to quite literally play with fire. Given that a fire can double in size every 60 seconds or less, one may not have much time. Steps involved in fire procedures including removing or limiting the source of the fire, such as cutting off fuel, oil, hydraulics, bleed air, and electricity. Steps may include discharge of fire agent, depressurizing or stopping airflow to a compartment, etc. Over the years, I've experienced wheel well fires, brake fires, cabin fires, engine fires, lav fires, cockpit fires, and other fires on board in flight, and indications that appeared to be a fire, but were not. It's my considered opinion that an attempt to down play and ignore or second guess procedures and fire indications is a bloody idiotic thing to do, and quite possibly one of the last idiotic things one may ever do.

Some years ago I entered a shop one morning to find an engine being removed from an aircraft. The owner was angry that the crew had discharged fire bottles and scrubbed a flight the night before. It took only a moment to find evidence of a fire, as well as a catastrophic engine failure. I found engine pieces imbedded in the floor inside the aircraft. The owner had chewed on the crew, claiming they responded to a false fire indication. The crew followed their procedure, blew both the bottles, and landed ASAP. Everyone got out, everyone survived. The crew was right, the owner wrong.

Bottom line, when you're the pilot in command, the owner, operator, director of operations, director of maintenance, customer, FAA, president of the united states, bishop, pastor, or witch doctor, will always have less authority than you. As the pilot in command, yours is the final authority, and the owner/operator/DO/DoM/FAA/MIC/KEY/MOUSE is on the ground, where it's safe. You're not. You're responsible for that aircraft, it's contents, its safe conduct, and for adhering to the procedures developed for that aircraft. Who gives a damn if it's a false indication? If you follow the correct procedure and it turns out to be a false indication, that's a maintenance issue, but you're not there to build the airplane, or work on it. You're there to see that the aircraft is legally and safely operated. Period. End of story. Let someone else figure out if it was a false alarm, later, on their time. That's not your concern. Follow the procedure, act in the conservative, safe interest of the flight, and leave the second guessing to others who have that luxury, on the ground.

rickair7777

Modern transport category aircraft have redundancy in fire detection (especially engine fire detection)... both to ensure that a fire is detected if present, but also to vastly minimize the odds of a false alarm (especially engines).

If you get an engine fire alarm, follow the published procedure. OEI is not an actual emergency in transport aircraft, it's an abnormal, although you will declare an emergency with ATC to get priority handling.

If the second engine were to fail later, you could always restart the one you had shut down.

SonicFlyer

What in the hell kind of contraptions have YOU been flying???


But seriously, excellent post, one of the best on APC.

joepilot

Hangar flying story.

Many, many, years ago, when I was a 747-100 F/E, my company got a great deal on some engine washing solvent. Apparently, this solvent corroded something in the fire loop circuitry on the 747. On the engineers panel, there were two fire/overheat temp gauges for each engine. Zero, green, would indicate a stopped engine. Normal indications were two to three for a normal engine. A ten would set off the fire alarm. If one of the fire loops became inop, the checklist called for cutting that loop out of the warning circuit. At the time, this was not that unusual a circumstance. Then the other loop was relied upon to provide fire warning.

On this particular day, the aircraft arrived in Taiwan with a writeup on the # 4 engine A loop. It had been signed off normally. Looking back for the last week in the logbook (paper, at that time), There had been four writeups of a single fire loop (loop A or B) in the last five days (same engine). We discussed the matter as a crew, Including how to respond to a "twitchy" temp indicator. Sure enough, about five hours into the flight, The B loop on the #4 engine started giving funky readings, while the A loop, which had been written up by the previous crew, remained steady. The temp indicator actually started bouncing between zero and max, setting off the fire alarm disagree light each time. Ran the checklist, cutting out the B loop. We discussed what we would do if the A loop, which had numerous previous writeups, decided to indicate a fire. We agreed that if the next loop indicated a fire, that we would shut down the engine (light weight, daylight, good weather). Then, another fire loop on #2 engine also failed, indicating a fire. Same checklist, same actions, now decided to NOT shutdown an engine without additional confirmatory evidence of a fire.

On descent, all fire loop temperature indications, indicated a rise, which was normal for this airplane, but the indications usually stabilized at 4 or 5. The A loop on number 4 engine (which had been written up by the previous crew) continued a slow rise. I advised the Captain, and told him that I was morally certain that we were going to have a false fire warning before landing; but that of course I could not be absolutely certain that the warning would be false. We got the fire warning bell at 500', and the Captain elected to not do anything about the warning. The warning bell turned out to be intermittent, sounding for about three seconds every ten seconds. The Captain elected to shut down the engine after clearing the runway, but the temp indicator continued to bounce from the bottom to the top of the gauge, setting off the warning bell every ten seconds on taxi in.

Maintenance could find no evidence of a fire or overheat. As long as A/C power remained on the aircraft, the fire warning continued to sound intermittently until the mechanic pulled some plugs.

Joe

Mordi

Ever hear the saying "unless you're on fire or getting shot at; take your time"? Even then - "slow is smooth, smooth is fast" still applies. In the case of a fire indication "slow" means giving an extra pause to verify you have the correct fire handle and thats about it.

There was a time when I might have considered doing like you suggested - investigating, etc. That was young and dumb me. I know better now; thankfully I didn't learn the hard way. Flying airplanes is easy. Making good decisions is the hard part, especially when grounding or diverting makes the boss, customer, or your family unhappy. Sometimes that is just part of being PIC.

Mordi

Regarding your comment about a known history of false indications: By ignoring warnings, you skew the data your management uses to make good decisions too. If there was a fault with something as critical as your fire indicating system, that needs to be fixed. Ignoring the warning because it was written up on the last flight only enables your mx team to push something out the door prematurely. If an operator isn't maintaining their airplanes, a few diversions may go far to show them the financial incentive to maintain their equipment. I'm not saying I would ever divert intentionally to cause harm to my employer, but you are legally obligated to operate safely and if following procedures means shutting down an engine and diverting over a faulty indication, and the faulty indication was due to an ongoing problem that wasn't addressed - then your employer made that decision to risk incurring those costs long before you got behind the wheel.

Think of this from a human factors perspective too. Ever read much (or experience) normalization of deviancy? If you make a habit of not taking fire warnings seriously, what happens when its an oil pressure low, or TCAS RA?

What would you do on a checkride?

PurpleToolBox

Ugh ... this is 100% FALSE. STOP REPEATING THIS LIE AND THROWING THE GOOD PILOTS OF SWISS AIR 111 UNDER THE BUS !!!!

Page 257, paragraph 5 of "Other Findings" of the Swiss Air 111 Accident Investigation Report, Canadian Transportation Safety Board ... https://www.bst-tsb.gc.ca/eng/rappor...3/a98h0003.pdf

"From any point along the Swissair Flight 111 flight path after the initial odour in the cockpit, the time required to complete an approach and landing to the Halifax International Airport would have exceeded the time available before the fire-related conditions in the aircraft cockpit would have precluded a safe landing."

The investigators said a safe landing was impossible, why are you telling this lie?

JohnBurke

A favorite question in skydive circles, is to ask a jump student how long he has to deploy his reserve parachute, during a malfunction. The correct answer is "the rest of your life."

SR111 was 66 nm southwest of Halifax at the time of detection. They made the decision to divert to Boston, which was 300 miles south. Moncton control prompted them that Halifax was nearer. The crew elected to take Halifax. The crew call at the time was pan pan, not mayday, and the crew had not declared an emergency; they had smoke in the cockpit, but not reported in the cabin. Five minutes had elapsed at this point; 25% of the remainder of their lives. Note that at the time of detection (by scent); the crew had the remainder of their lives to handle the emergency. Historically we know that was twenty minutes. One quarter of that was used taking the time to decide where to go; a decision between diverting 300 miles south, or the closer Halifax. The pilots donned oxygen six minutes after detection.

The flight was cleared to 10,000' and then to 3,000' and a vector assigned; the crew replied that they needed more time to set up for landing. The crew was cleared to 3,000, but advised that they needed to stop at 8000 to take time to prepare the cabin for landing. At this point they had used half of their lifetime since identification of the scent of smoke, or approximately nine minutes.

At the 75% point in their remaining lifetime, or fifteen minutes after the first detection of the scent of smoke, the crew took a vector north, with the intent of dumping fuel. The pllots then took a turn south and advised that they were preparing for a fuel dump to reduce weight for landing, and would dump at 10,000'. They had about ten minutes left in their lifetime at that point, and were within 25 miles of the airport. With nine minutes left to live the crew took one more vector, and advised they were starting the fuel jettison.

The controller asked the pilots if they intended to remain close to the airport, or whether they intended to fly south away from the airport; the crew advised that they were willing to fly away from the airport for their fuel dump and thus took the south vectors away from the airport. It's worth noting that the both pilots were instructors, and the captain a check airman, for Swissair, though neither had ever experienced an inflight emergency, or there is no record or history of such experience. The crew was also aware that the aircraft could be landed overweight. It should also be noted that the MD11 has the fasted landing speeds of any commercial airliner. In any event, with the second vector, the crew couldn't know, but had eight minutes left to live when they reported level at 10,000'. At that point the crew began to run a smoke checklist.

Just shy of fourteen minutes into their lifetime since detection of the fire by scent, the crew declared an emergency, and were promptly advised the controller would get back to them in two minutes, or in 1/3 of their remaining lifetime. The crew acknowledged that, and at the same time advised they were starting the fuel dump. A minute later they declared an emergency again, now fifteen minutes after detection, having used 3/4 of their lifetime since detection to get to this point. The controller cleared them to dump fuel, but did not receive a response. No one would hear form them again. Just under six minutes later, an impact was both heard by observers and felt by seismographs.

Few of us know how much time we have left. How long to tell our loved ones that we care about them? In reality, the rest of our lives. Or theirs. Ten minutes? Ten hours? Ten years? We don't know that; it behooves us not to wait.

How long do we have to divert and land, rather than dump fuel, run checklists, prepare a cabin, take vectors, etc? We don't know. For SR111, the answer in retrospect is that they had just under 21 minutes.

When faced with a divert decision, the initial choice wasn't Halifax. It was Boston, 300 nm away. UPS 6 chose Dubai, their departure point, instead of Doha, nearby.

We pays our price, we takes our chances. Will they bear fruit? It's very possible that at the time of fire detection, we have the remainder of our life to sort it out. The longer we delay, the greater the chance that our remaining lifetime will be short. If we do nothing, we burn up, systems burn up, we die. We have to do something. The fire department isn't coming to us. We have to get to them. We can't pull over and ask for help. There's no bringing in additional resources; what we have at the outset is what we have to work with. We won't get to make assessments of what percentage of our lifetime (since detection) that we spent taking vectors away from the landing airport, dumping fuel, running checklists, preparing the cabin for landing, etc. But someone will. Investigators. Ground school instructors who use us as a life lesson. People on an internet web board. Someone will.

The Canadian report states in it's other section that the crew wouldn't have made it. This is not found in the primary report conclusions, but in the contributing factors; the Canadian report looks more closely at other factors, such as flame propagation, wiring, fire detection, and so forth. The Canadian report notes that the controllers didn't contribute to the mishap, though they did assign multiple vectors away from the airport, and the crew took them. Conversely, though not mentioned, has the controllers simply acquiesced to the pilot's choice, they'd have not prompted the crew to take Halifax, four five times closer to them than their initial decision, Boston.

Might the crew have made it, if they weren't flying away from the airport, leveling to dump fuel, running checklists, preparing the cabin for landing, etc? Would they have made it had they not waited until three quarters of their remaining time was over before they declared an emergency? Often, the declaration of an emergency (or mayday, vs. pan pan) marks the point in time where we've announced the seriousness with which we take the present occasion. There are certainly times when we will not be immediately aware, and there is always a sequence of events during which we continue to discover or learn of the progress of the situation. The crew in this case felt sure enough about their choices that they bet their life on those choices. They lost the bet.

This much we know: flying away from the airport will not get us closer to the airport. Taking time to jettison fuel is not time spent descending to land, or getting closer to the airport. Preparing the cabin is nice, but a tidy cabin loses its shine on impact. We may have never experienced an emergency, but the one that counts is the one right now. We can be a systems expert with a history of stressing the mechanics of smoke procedures, but that doesn't buy time, and that experience gets us no closer to the airport when we take vectors away from the airport and request a higher altitude and to stop our descent, and choose to prioritize fuel jettison over a landing.

There is no throwing the crew under the bus. They're dead. Their actions and choices and the results, are a matter of record. From the time of detection, they had the rest of their lives to get on the ground and evacuate. They chose to spend the rest of their lives taking vectors, flying away from the airport, preparing the cabin for landing, running checklists, and asking for delaying vectors, because they weren't prepared to land. This is part of the record. Call it what you will. It doesn't change the fact.

PurpleToolBox

And it doesn't change the fact that a safe landing was IMPOSSIBLE for a couple of reasons that was listed in the official Canadian TSB report. No they didn't lose the bet (taking vectors away or choosing to dump fuel) ... they were doomed anyways.

You say they had 21 minutes. Wrong, they had less. At 01:22:37 was the closest they got to the airport (30Nm). They lost all instruments at 01:25:33. At best they had 15 minutes when you subtract the time they were left with an uncontrollable aircraft. Even if they proceeded straight in without the vector to the north and back to the south, they would have lost all instrumentation before making it to Halifax. They were not visual with the airport.

Other problems.

NOT ENOUGH LANDING DISTANCE AVAILABLE: They only had 8,800 feet of runway available at Halifax. The fire destroyed the wiring to the flap/slat valves/controllers. The slats did not extend. They didn't know this. They also had no anti-skid. Because of this, they needed as much as 10,000'-12,400' depending IF the flaps would have extended beyond the 15 degrees to which they were set. This is also in the official report.

LOCALIZER BACK COURSE: They would have lost all instrumentation before flying below the clouds and becoming VFR with the field. Would they have been able to fly VFR with no instrumentation at night with a cockpit filled with smoke. I say very doubtful from my own personal experience. But you're right, they didn't take that bet.

Looking back at that 15 minutes to live, you say the first five minutes were wasted. Not really, they were still on a path proceeding to the closest airport to land. What we know is they would have lost all instrumentation before landing. They didn't have enough landing distance. We know they lost control of the airplane most likely because of no instruments in IFR and no slats (probably stalled) which might suggest why they were 20 degrees nose down and 110 degrees banked right at impact. My speculation.

Have you had a fire in an airplane? I've had a fire in a McD tri-jet at night without a place to land. Took us about 45 minutes to get to a runway. The fire was in our avionics compartment underneath the cockpit. We lost all cockpit lighting. We lost comms with one another. In order to hear each other we had to pull off our O2 mask and yell back and forth. The smoke burned our eyes and throats. The smoke made seeing outside the window extremely difficult. Our flight path afforded us a straight in ILS to a VFR field at night and we dumped until we were close to the field. I don't remember if we were overweight but the runway available was 13,100'. We had slats.

I know it has been reported that FedEx and Delta has had aircrews make it to the runway ... in the simulator ... which isn't realistic because we don't know all of the circumstances and issues they faced. Nor do we know just how much or little odor they initially smelled. They thought it was the AC which in a McD I can very well understand. Who hasn't had an odor in an MD?

They made bad decisions. But they were doomed anyways. That is the record. The officials agree with me. Yes you threw the crew under the bus because you blamed the accident on "a crew that didn't take a fire seriously."

This was a watershed moment for the airline industry. Even in my situation, it took us a minute or two to realize and accept that we had a fire and started a diversion. They took five. Subtract that from the 15 minutes to live.

They were doomed. And the record shows it. Giving you the last comment as I'm not replying after this.