Upon a rapid decent how long would it take to descend from 40,000 feet to 9,000?

Question

If you were on a standard commercial airliner and the cabin depressurized at 40,000 feet then how long in time would it take to descend to 9,000 feet and how noticeable to the passengers is the decent?

Answer 1

It's noticeable all right. You won't be able to BS your way out of that one should it ever happen to you.

Answer 2

Assuming a 5000 fpm descent, it would be a little over 6 minutes and it would be INCREDIBLY noticeable - think nosedive.  Anyway, compare that to a normal descent is around 1500 fpm.  

Answer 3

Standard procedure for a rapid depressurization scenario is to immediately get an oxygen mask on, then bring the engines to idle and roll the aircraft into a moderately banked turn. At the same time the spoilers are deployed and a descent initiated while the aircraft is slowed to the maximum speed at which the landing gear can be deployed. Once the landing gear is out, the nose is lowered to maintain the maximum allowed speed with the landing gear extended.

The bank will add some additional G-forces to the aircraft to help the passengers remain in their seats (probably 1.2 to 1.5 G's), while also providing some speed control. Don't overdo it, though. Usually 30 to 40 degrees of bank will be fine. The spoilers and landing gear are deployed to allow a greater descent rate without an increase in speed. Depending on the aircraft, you should be able to easily maintain a descent rate between 4,000 and 8,000 feet per minute without overstressing the aircraft. That equates to about 4 to 8 minutes to descend from 40,000 feet to 9,000 feet.

As for the passengers noticing, you can be sure they will. This is not a maneuver that is designed with passenger comfort in mind, but is rather intended to get the aircraft down to a denser atmosphere as quickly and safely as possible. Also, the oxygen masks should have deployed as soon as the depressurization occurred, and will have given the passengers an idea of what is happening.

Answer 4

emergency controlled descent due to depressurization can vary between 1000 feet per minute  (recent Quantas flight) and 9,000 feet per minute.

the descent may or may not be noticeable to the passengers due to their state of mind which is likely to be panic.

if however, you were calm, you would notice this descent from the nose down attitude, the pressure in your ears changing, and at some point, you'll notice the ground/sea to be much closer

to calculate the time, just subtract 9000 from 40,000 and then divide with the descent rate. that'll give you the minutes required.

Answer 5

About 5 minutes.  The descent is usually shallowed at 14,000' MSL.  The deck angle is about -10º, maybe steeper.  That's noticeable.  They can feel it even if they can't see it in the fogged cabin.  A 30º to 45º bank angle doesn't add much of a G load.  45º is only about 1.2 G.  Not noticeable.  Banking bives better visibility of what is below.  In some aircraft the descent speed can be as fast as Mmo, and the landing gear is not extended.