(Un) Holy Smoke! The Nightmare of Smoke, Fire, and Deadly Gas

--by James Williams, FAA Safety Briefing Staff

Confession time: What’s the one thing in general aviation (GA) that scares you, I mean really scares you? For me it’s always been fire. Just the thought of an aircraft fire unnerves me. Luckily these incidents are not common, but they happen enough to be a concern. When you look at the National Transportation Safety Board (NTSB) aviation accident files, you’ll find that there is a significant overlap among three dangers: smoke, fire, and carbon monoxide (CO).


Bad Things Come in Threes

The danger from fire requires no detailed explanation. Smoke, on the other hand, not only obscures your vision but also irritates your eyes and lungs while choking you with a mixture of tiny particulates (some still burning), hot vapors, and toxic gases. That’s why smoke inhalation causes most fire deaths according to the National Fire Protection Association. CO is the most insidious. CO is found in smoke, as well as exhaust, and contributes significantly to smoke inhalation’s deadly effects. You’ll find more information on CO in this issue’s Condition Inspection department, but suffice it to say if you were looking to design a deadly gas, CO is hard to beat.

Mechanisms of Dread

NTSB accident files indicate several common issues leading to smoke, fire, CO, or any combination thereof. The most prominent are exhaust system leaks or failures. Releasing a bunch of super-hot exhaust gases into the nacelle is exactly as bad as it sounds. In one example, a Bellanca pilot experienced an exhaust leak that caused an electrical system fire near the fuel pump and required a forced landing due to fuel starvation. Fortunately, the pilot was able to walk away with only minor injuries.

Another common ignition point is the electrical system. Short circuits in wiring can start fires on their own, but there are also situations where loose wires can chafe against other components and cause arcing. This problem is especially dangerous when wiring chafes against a fuel line, and even more if it occurs around the instrument panel. In one accident, wiring chafed against a fuel flow gauge pressure line, ignited the fuel line, and destroyed the aircraft. Luckily, the pilot was able to make an emergency landing at the first signs of smoke, and to safely exit without injury.

Maintenance errors lead to a significant number of smoke, fire, and CO-related accidents. Really simple issues like failing to properly tighten bolts or clamps can lead to catastrophe. One sport pilot accident illustrates this unfortunate reality. The pilot was the owner and builder of his experimental light-sport airplane and had spent the previous four months tracking down a fuel leak. Two days before the accident, he reported resolving the issue. The pilot was performing touch-and-gos when witnesses observed the airplane on fire before it went down. The investigation determined that an oil and fuel line had not been properly torqued down and that one of them likely came loose due to normal engine vibrations and caused a fire in the compartment. Because of fire damage in the engine compartment, investigators could not determine which line actually initiated the blaze, but neither would have been affected by the pilot’s recent repair to the fuel system.

Preventive Measures

As accident files suggest, the causes of these nightmares are often linked. An exhaust leak can grow. An electrical fire can burn a fuel line. But just as the causes are linked, so too are the solutions. Prevention is far better than dealing with an airborne fire, so here are a few strategies you may find helpful.

Prevention is far better than dealing with an airborne fire.

The first and easiest is a CO detector. They are relatively cheap and can provide a good early warning sign of potential problems. CO detectors can often alert you to the presence of CO even when you can’t smell exhaust fumes. They range from the simple color-changing dot style detectors, to more sophisticated devices that are both portable and panel mounted. The more sophisticated devices have the advantage of being active, meaning that they sound an alarm when potentially dangerous CO levels are reached.

Another good practice is to enhance your preflight when it comes to the engine compartment. Scan the exhaust system for any cracks or holes. Some common failure points you should pay attention to are the muffler and any exhaust system joints or welds. If access allows, scan the compartment for loose wires or hoses. Sometimes they can come loose from their attachment points and this can lead to chafing or fatigue damage. Check the battery for any signs of scorching or singeing that might indicate an unsafe condition around it. Finally, look for loose connections or hardware. Does that nut look like it has backed off? Is that hose clamp secure? These kinds of things can and do happen, whether it’s a mistake during maintenance, or just the parts wearing out. Undetected and unresolved, these simple issues can have deadly consequences.

Exhaust Leak

If you see damage like this, it is evidence of an exhaust leak that needs to be investigated by an AMT immediately.

Wires and Hose

Properly secured and separated wires and hoses are critical to preventing chaffing that can cause fires.

Frayed Insulation

Damaged insulation on wiring can lead to arcing which can cause both electrical and engine fires.


Pay added attention to welds or joints in your exhaust system as they can be common failure points.

What if the Nightmare Arrives?

What should you do if you find yourself in a fire and/or smoke-related nightmare? The FAA’s Airplane Flying Handbook has some good suggestions. The first step is to determine what kind of fire you are dealing with. The two major categories are engine and electrical fires.

Engine fires are generally indicated by smoke or flames coming from the cowling, although sometimes they are not visible from the cockpit. Another sign can be discoloration or bubbling of the cowling. By the time any of these signs are visible, the fire is usually well developed. You should always refer to the manufacturer’s procedures first, but here are some general guidelines:

  • Mixture — Idle Cutoff
  • Fuel Selector — OFF
  • Ignition — ON
  • Ventilate Cabin (unless fire worsens or reignites)

Do not attempt to restart the engine. Also some manufacturers will advise that you turn off the master switch while others may not. This will disable radios, transponders, etc., that could be useful in getting emergency assistance. But it also could be helpful in extinguishing the blaze.

This potential conflict, however, does not apply to electrical fires. Electrical fires can usually be distinguished by the distinct odor of burning insulation. Your specific aircraft’s procedures are the key, but in general, steps to follow if an electrical fire is detected include:

  • Attempt to identify the faulty circuit via the circuit breaker panel and other electrical systems.

If that fails, and flight conditions permit:

  • Turn battery master — OFF
  • Turn alternator/generator — OFF

If electrical power is necessary and you want to attempt to restore power, you should:

  • Turn all electrical switches — OFF
  • Turn the master back — ON
  • Individually turn each switch back ON while waiting a short time in between to check for signs of a fire.

This procedure assumes that the electrical fire doesn’t cause an engine fire, which can of course happen when it compromises a fuel or oil line.

While dealing with any kind of fire you will need to find a landing site, since there’s no way to tell how much damage the fire has caused or if it is fully extinguished.

CO is a less visible threat, but all the more dangerous due to its stealthy nature. Should you experience the symptoms of CO poisoning, or get an alert from a detector, you should take immediate action. Turn off the heater (if on), open fresh air vents and windows, and use supplemental oxygen if equipped. Once those actions are complete, land as soon as possible.

Engine fires are generally indicated by smoke or flames coming from the cowling, although sometimes they are not visible from the cockpit.

Waking Up

Smoke and fire issues are truly the nightmares that haunt many pilots. It’s far better to prevent them than to try and deal with them in flight with fewer options. Remember that fires are an absolute emergency that demand quick, correct action. Memorizing your aircraft’s specific procedures is highly encouraged as you will likely be required to divide attention between extinguishing the fire, contacting ATC, and selecting a landing site. In the case of an engine fire, you will be landing, and in the case of an electrical fire or CO exposure, you should be landing. There’s no glory in battling these nightmares. Get on the ground and live to tell the tale.

Learn More

James Williams is FAA Safety Briefing’s associate editor and photo editor. He is also a pilot and ground instructor.

This article was originally published in the September/October 2019 issue of FAA Safety Briefing magazine.
Created By
FAA Safety Team

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