harrisonjones

A transatlantic flight diverted to Boston last night due to smoke in the cabin. This is one of the more un-nerving situations for a flight crew because there are so many unknowns involved. Make yourself comfortable on the observer’s seat and we’ll watch the crew deal with the problem. The emergency checklist for this particular  procedure is ten pages long, but I promise I will not bore you with the details. Fortunately, there are only two initial action items:

1.      Oxygen Mask……….On/100%
2.      Establish crew communications 

This sounds simple enough, but it’s more involved than you think. First, the mask is actually a quick donning full face oxygen/smoke mask and your head is now being squeezed by pneumatic tubing to seal it against your face. You’re viewing the world through a clear plastic window and your peripheral vision is somewhat limited. If you wear glasses you hope they stay on your nose and not your chin. Next, you are now breathing 100% oxygen under pressure, which means when you part your lips to speak, your mouth fills with oxygen and you sound like a hissing alien. Establishing communications with the crew is simple enough. You flip the switch one way to  talk to the copilot and the opposite way to talk to ATC. However, I promise you will soon be asking the copilot for clearance to the nearest suitable airport and profanely urging ATC to hurry with the checklist; all in the alien voice. You desperately want to call time out, but of course you can’t.  

Now to solve the problem. The checklist contemplates three possible sources for the smoke or toxic fumes;  electrical, air-conditioning, or leaking/damaged dangerous goods (The nuclear waste someone shipped in the forward cargo hold). Since we don’t have the time, space or inclination to consider all three, we’ll just look at the most common which is electrical. The airplane has tons (literally) of electrical equipment, any of which may overheat or short out and create smoke or fumes. The electrical system of a modern airliner can power a small city and takes about a day and a half of ground school to teach. I’ll give you the short course. Each engine drives a generator to produce AC power plus there is an auxiliary power unit with a supplementary generator. There is also an emergency, wind driven generator that can be deployed, but let’s not go there. The ship’s battery will  power a few basic instruments if all else is lost, but without the normal charging system you only have about thirty minutes to find an airport or at least VFR conditions. 

The procedure now involves isolating sections of the electrical system, called busses, until you identify the  problem. You start with the cabin busses and hope the fault is in a fluorescent light transformer or a galley oven. If not, you have to isolate busses involving instruments, autopilots, and flight controls. You can see why the checklist is ten pages long. The possibility exists that the best case scenario will involve flying an ILS approach to minimums with no autopilot and only raw data basic instruments. Don’t forget you’re still wearing the mask and turning your head instead of using peripheral vision. The hissing alien voices are now speaking soprano at a rapid clip. On your next proficiency check, if the instructor puts you under the hood and takes away your color TV, thank him for his foresight and professionalism. By the way the smoke cleared before the flight landed in Boston last night and I’m sure the dulcet tones of the pilot’s voices was a comfort on the PA. Nice job guys.