Central Flying Academy In-Flight Electrical Fire
How To Survive An In-Flight Electrical Fire
Ask any experienced pilot what they think is the worst in-flight emergency, and they'll probably tell you "fire." Most pilots feel comfortable with their ability to land an airplane without power, but a fire can be truly terrifying.
Fires are rare. But if you do have an in-flight fire in a light aircraft, there's a good chance it will be electrical.
It goes without saying that electrical fires can be very dangerous. In 1998, an electrical fire brought down Swissair Flight 111. And with all the wiring in modern aircraft, there are lots of possible sources for ignition.
Arcing Is All It Takes
Electrical fires usually start when a short in your electrical system causes an arc. Over time, chafing can wear away the insulation on your wires. And if two open wires touch, they can arc.
When an arc happens, it can ignite the surrounding wiring insulation or other flammable material nearby. But there is some good news. In the fire's early stages, it's fueled by electricity. If you remove that, you can usually stop the fire.
The First Sign Of A Fire: You Smell It
The best way to identify an electrical fire is often through its smell. It's an acrid, sharp smell that's unmistakable. And, it won't smell like burning oil or gasoline. Electrical fires can generate a faint, white smoke as well. But often times you won't see anything as the fire starts, you'll simply smell it.
As the fire grows, your circuit breakers might start to pop. And eventually, your avionics and electronics may start to shut down. But, by that time, the fire has grown significantly.
Your First Step: The Checklist
As for most emergencies in aviation, "there's a checklist for that". Every aircraft has a unique electrical fire checklist, but nearly all of them follow the same basic flow. Essentially, you want to:
- 1) Stop the fire
- 2) Clear the cabin of smoke and fumes
- 3) Land
The Cessna 172S has a pretty typical flow, and we'll use that checklist in this example. (but remember to always use the checklist for the airplane you're flying)
How To Stop The Fire
When a fire is fueled by electricity, turning off power will remove the fuel. You do that by:
- 1. STBY BATT Switch - OFF: This takes the standby battery offline and prevents it from fueling the fire
- 2. MASTER Switch (ALT and BAT) - OFF: This cuts off power from both the main battery and the alternator. Again, you're removing all power from the electrical system, cutting off the fire's fuel
Next, you want to cut off oxygen from the fire and prevent fumes from blowing into the cabin. Electrical fires often occur behind the panel, where air from the heater and vents can blow the smoke into the cabin. But, even if the fire is in the headboard or tail, you want to cut off airflow. Oxygen feeds a fire, and air flowing through your vents will help the fire grow. Here's how the checklist stops it.
- 3. Cabin Vents - CLOSED (to avoid drafts)
- 4. Cabin HT and CABIN AIR Control Knobs - OFF (push full in)(to avoid drafts)
With the source of the fire cut off, it's time to use your fire extinguisher.
- 5. Fire Extinguisher - ACTIVATE (if available) You've done everything you can to douse the fire and you've removed all electricity from the system. There are a few more steps you'll take. These steps don't remove any more electrical power, because your batteries and alternator are already off-line. However, they'll come into play if you have to power any electrical equipment back up later down the road.
- 6. AVIONICS Switch (BUS 1 and BUS 2) - OFF
- 7. All Other Switches (except MAGNETOS switch) - OFF
What About My Engine?
Since your aircraft's electrical system and engine ignition system are entirely separate, your engine will obviously continue running throughout the process. That's one of the upsides of magnetos.
However, your avionics are going to shut down, which is something you need to be thinking about, especially if you're in the clouds (which we'll get to shortly).
Is The Fire Out?
After your fire is out, it's time to clear the cabin air. But how do you know the fire's out? It's really a judgement call, because the acrid smell from the fire will linger in the air, and you may have fire retardant from your extinguisher obscuring the fire.
The best option is to give it time. Your airplane flies fine without an electrical system, so wait it out. You may see the smoke begin to clear or the acrid smell begin to dissipate. Once you've determined the fire is out, your next step is to clear the air.
Clearing The Air In Your Cabin
The next checklist steps are all about clearing the smoke and getting fresh air into the cabin.
- 8. Cabin Vents - OPEN (when sure that the fire is completely extinguished)
- 9. CABIN HT and CABIN AIR Control Knobs - ON (pull full out) (when sure that the fire is completely extinguished)
You want as much airflow as possible to clear smoke and fumes from the cabin, and by opening the vents and turning on the heat and cabin air, you'll do just that.
Now It's Time To Land
At this point, it's time to get yourself on the ground. And there are a few things you need to consider when it comes to a diversion airport.
If you're in visual conditions and you can continue the flight to a nearby airport without electrical equipment, that may be your best option. Why? Because restarting your electrical equipment might restart the fire.
If you need to contact ATC, use your mobile phone. And, if you need some GPS help along the way, your tablet and phone have that, too.
But, if you're in IMC or need electricity for aircraft systems, you might need to restore power. Take your time with this part of the checklist. Restoring power can re-ignite the fire, which you may not notice right away. Here's what the checklist tells you to do next.
IF FIRE HAS BEEN EXTINGUISHED AND ELECTRICAL POWER IS NECESSARY FOR CONTINUED FLIGHT TO NEAREST SUITABLE AIRPORT OR LANDING AREA
- 10. Circuit breakers - CHECK (for open circuit(s), do not reset): This is important - don't reset any breakers that have popped. They could be the source of your fire. But, if more start popping, they could help you identify where the fire's at. Note which breakers are already out.
- 11. MASTER Switch (ALT and BAT) - ON: This restores power to your electrical system.
- 12. STBY BATT Switch - ARM: This brings your standby battery back on-line
- 13. AVIONICS Switch (BUS 1) - ON
- 14. AVIONICS Switch (BUS 2) - ON
When you've restored power to your electrical system, it's obviously important to watch for the fire to restart. If you start to smell the fire again, or if a circuit breaker pops, power the electrical system back down right away.
What If You're In IMC And You Need Your Electrical System?
It's obviously a bad situation, and in this case, your judgement really comes into play.
If several breakers have popped, you can check the aircraft's manual to see if they're all on the same bus. If they are, you can remove power to that bus and try again.
But, you may have no idea where the fire is at. If that's the case, you can pull every breaker on your panel, power up the battery and alternator, and SLOWLY push only the most essential breakers back in. By waiting between each breaker, you can hopefully prevent the fire from restarting. And, if there's a piece of equipment you don't absolutely need, leave it off.
Backup Options On Your Tablet And Phone
If you have to shut down your avionics, your phone and tablet give you some really great backup options. Your phone can quickly replace your radio. And ForeFlight on your iPad, coupled with a Stratus, provides a backup attitude and heading system.
If you need some motivation to try out new technology, being prepared for a situation like this just might be it.
Getting Down Safely
Your first priority in an electrical fire is to identify the source of the fire, get it out, and get fresh air into the cabin.
After that, use the minimum amount of electrical equipment you need to get yourself on the ground safely. With backup options on your phone and tablet, you can get yourself on the ground, in many cases, without needing to restart your electrical system at all.
This is not an original article. It first appeared on boldmethod.com on 28 March 2017. To read the original article click here.
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