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The current procedures (cargo) I refer to are a descent to FL250, depressurizing, and cruising until 60 miles from landing (this could be over an hour).
Here is my take on the disconnect. If I get a main cargo deck fire warning (and I have to assume it's real) I start a mental (if not physical) 20 minute timer. Where do I want to be when that time runs out? At FL250, 45 mins from land? Hoping the engineers are right about starving the fire? Is it a lithium battery fire (10,000lbs on my last crossing) and it will never starve?
Would it not be a better use of time (the rest of your life) to descend immediately to a safe ditching altitude (say 1000'agl) and analyze the situation? From FL 330 it would take 20 minutes to get down and prepare to ditch on a good day, any delay with investigation and fire checklists at altitude will take you out of your 20 minute survivability window.
At 1000'agl, assess the situation. Is it a real fire? If so, you are ready to ditch. If not, you have the fuel to climb back up and divert (which you were going to do anyways).
FL330 to sea level in 20 minutes? That's a descent rate of 1,650 fpm. If you're intending to reach the surface and ditch because you're on fire, you're going to do a leisurely descent to the surface at less than 2,000 fpm? You should easily be able to get 5,000 fpm or better with the boards out, and that puts you on the ground in six minutes. You're going to get to 1,000 and then begin doing checklists? Get them done on the way down. If everything can't be accomplished in five minutes, then brush up on those procedures. 5 minutes is more than enough time. You're on fire.Originally Posted by decrabbitz
The current procedures (cargo) I refer to are a descent to FL250, depressurizing, and cruising until 60 miles from landing (this could be over an hour).
Here is my take on the disconnect. If I get a main cargo deck fire warning (and I have to assume it's real) I start a mental (if not physical) 20 minute timer. Where do I want to be when that time runs out? At FL250, 45 mins from land? Hoping the engineers are right about starving the fire? Is it a lithium battery fire (10,000lbs on my last crossing) and it will never starve?
Would it not be a better use of time (the rest of your life) to descend immediately to a safe ditching altitude (say 1000'agl) and analyze the situation? From FL 330 it would take 20 minutes to get down and prepare to ditch on a good day, any delay with investigation and fire checklists at altitude will take you out of your 20 minute survivability window.
At 1000'agl, assess the situation. Is it a real fire? If so, you are ready to ditch. If not, you have the fuel to climb back up and divert (which you were going to do anyways).
Five minutes is an eternity.
Why not spend the other 14 minutes enroute to your divert field, at altitude, on oxygen, running the relevant fire procedures for your aircraft? True airspeed's higher, oxygen lower in partial pressure, fire behavior less aggressive. You might have an artificially-derived 20 minutes on your personal clock, but go ditching in the North Atlantic, and you have one or two minutes in the water before you succumb, if you survive the impact at all.
If you have a self-oxidizing fire, then you won't be starving it of oxygen by remaining at altitude. In that case, work on reducing those five minutes to less. There are no guarantees that you've got 20 minutes.
Of curiosity, your position shows MD-11 first officer, but you stated you're doing 777 cargo. Different procedures, and the MD-11 relies on discharging a bottle and sealing the compartment, with a 90 minute timer to the next bottle. Not so for the 777, correct?
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Thank you. I ordered Angle of Attack, linked off the website at the opening of this thread. Looking forward to the read.Originally Posted by ptarmigan
Yes. Thank you!