View Full Version : Rapid Decent

28th Jul 2008, 02:52
With the recent incident with QF, I wanted to ask what feelings do passengers get during a rapid decent ? do you feel massive negative g as you do when you hit sudden airpockets ?

Also if this is a standard procedure, it would make a big difference if the flight crew would tell passengers whats going on, and not to panic, as we are in a rapid decent mode.

Many passengers on QF30 said they thought they were going to crash into the sea, as the rapid decent lasted 10 minutes.
This would be very terrifying for passengers if they did not know what was going on, and 10 minutes would seem like an hour.
I know the tech crew would be busy, but it would help to know whats going on, is this the case ?


28th Jul 2008, 03:11
It might make the the pax feel better but it won't keep them alive. Making a PA during an emergency descent is a secondary consideration to correctly executing the descent procedure and getting revised clearance from ATC etc. The tech crew would have been very busy indeed. Cabin crew cannot use the PA during an emergency descent because they are on oxygen too and could pass out if they took their masks off. Some aircraft automatically play recorded announcements over the PA system during an emergency descent. One I've heard goes along the lines of 'this is an emergency announcement, the aircraft is being descended to a lower altitude .... ' Would possibly help your anxiety but who knows.

28th Jul 2008, 03:13
There is an actual recap of what happened to a passenger on airliners.net. Most of your questions were already answered by the user:) Account - 1st Class Passenger On QF30 Civil Aviation Forum | Airliners.net (http://www.airliners.net/aviation-forums/general_aviation/read.main/4082678/)

28th Jul 2008, 03:13
You'd only feel real "negative g's" if the descent rate was constantly INCREASING at a very high rate - greater than 32 feet per second per second. Even the famed "Vomit Comet" flights for training astronauts, flying a parabolic descent, only get to zero g, which is not negative.

If the descent rate were increasing, but at less than 32 ft/s^2, you'd feel a bit "light in the seat" but the net g's would still be positive - i.e. your feet would remain on the floor and your - ahem - "seat" would remain in your seat.

In the real world event there would be a momentary "lightness" as the plane noses down, and then the descent rate would stabilize at 2000/3000/whatever fpm the pilot picks, your body would catch up to the descending plane, and you'd just feel 1g (normal gravity) for the remaining time of the descent.

I agree that lack of information can lead to unnecessary concern. it would not HURT for it to be standard procedure to announce "We are making an intentional emergency descent for your safety" to the pax.

OTOH the order of priorities for pilots has always been aviate/navigate/communicate, so communication, either with the pax or the ground, has always been tertiary to maintaining control of the aircraft and maintaining situational awareness.

Cabin crew also have assigned "battle stations" in the event of an emergency - but perhaps there is a way to work such an announcement into the check list without compromising other tasks.

28th Jul 2008, 03:35
With the recent incident with QF, I wanted to ask what feelings do passengers get during a rapid decent ?I'm not a pilot, I'm very infrequently SLF - but I'm a fan of large aircraft and worked on the avionics of C-141 and C-5/A during my hitch in the USAF.

I've been on 2 commercial flights and a charter which had to drop altitude rapidly due to cabin pressure issues, none of which were [fortunately] as sudden as QF 30's problem.

It's a mess, it's unpleasant, ears pop and hurt, and in the commercial flights, what started the little panic there was, was someone who knew nothing about aircraft starting to mouth off.

(There was no problem on the charter flight, as the pilot spoke directly to us.)

Several folks have mentioned that it would be a good idea to include a hint about a rapid decent in the safety speech.

That's a great idea - I think it would help the folks who don't know pooh about airplanes understand what's going on.

But, I've got to comment... Most of the people flying these days really belong on buses or ships, where life is much slower.

I miss the days when you could pay for a 1st Class ticket and get 1st Class treatment from the time you got out of the cab at departure until you got into the cab at the other end.

Now, no matter how much you pay, it's all cattle-car quality. No food, poor and harried service, a generally hostile attitude, and the pilots seem almost afraid to say 'hello' if you happen to see them while you're boarding.


28th Jul 2008, 03:41
What counts is that the Pilots do a "decent" job.:E

28th Jul 2008, 03:55
There are sensations during the event that stem from two sources. 1) The rapid descent itself, which is described in the above posts. Expect partial g force while the aircraft initiates descent, a gradually increasing nose down pitch to a steeper angle than most would be familiar with, and (2) the reason for the rapid descent, which in this case is a loss of cabin pressure. (Not experienced this myself, but spoken with medics and pilots who have practiced it in the pressure chamber.) This happens very fast in an explosive decompression. There would be sound, a big gust of air, taking lightweight or not- secured items with it, abrupt cooling of the air inside the aircraft (which causes the white mist often seen in these events, as the water vapour in the air condenses out), ear-popping, and flatus, as the body's internal pressure tries to equalize.
Not seen this, but I'd imagine it would be all over in a few seconds, then you'd expect to feel the nose drop, maybe combined with a fairly steep bank angle on some types. If (as it most usually would) the nose stops dropping, and the dive stabilizes, that's a big clue that the aircraft is under control, and the dive planned.
I've been in an airliner where this was simulated, and simulated the motion numerous times in light aircraft. It can be a somewhat revolting feeling until one is used to it, and, especially combined with the noise, wind, white mist etc, almost certainly gives rise to the reports of passengers thinking they are in a death plunge.
In the highly unlikely event you are ever in one of these, don't bother trying to grab the mask until the wind dies down and it stops jiggling around. Put it on ASAP, pull the tube (as directed,) breathe deeply. Then, once you've noticed the dive stabilizing, and noise permitting, you can reassure those near to you (if they need it) that the dive is a controlled one.
Personally, I think the surprise of being in one of these would make one forget all this, unless one repeatedly trained for it.

28th Jul 2008, 04:12
NO. It isnt much steeper than a normal 'expedited' descent.

The pax would def panic when they hear pilots psaking through oxygen masks. Would sound quite freaky, and mostly unintelligible! Thats why we dont.......................

India Four Two
28th Jul 2008, 04:35
Just to avoid confusion, goeasy is answering my question about the deck angle during descent, which I deleted, because I hadn't seen Tarq57's post.

28th Jul 2008, 06:48
10 mins to descend 19000ft is not a rapid descent. On another thread, apparently the pilot's wife has stated that the descent lasted 4 mins. That also suggests that it was not a descent at Vmo, but a slower descent with structural damage in mind. The 'deck-angle' during a rapid descent is alarming to those not expecting it, as the aircraft will be accelerating towards a constantly increasing Vmo which increases both rate of descent and pitch down attitude.
An announcement with crew oxygen masks on, will be almost unintelligable due to the announcer breathing and the sound of the oxygen flowing. Adding the warning of rapid descent to the pre-flight briefing would be a good idea and one that may well be recommended in the accident report.
HotDog- I also think the crew did a "decent " job in the "descent":E.