JIMMYTWO Posted January 30, 2013 Posted January 30, 2013 Is this possible? Just reading a report in the Daily Telegraph today that a Qantas 737-800 travelling from Brisbane to Townville was forced to descend at 30metres (100 feet) per second. That works out at 1000 feet every 10 seconds? Official reports tracking data shows the aircraft dropped from 40,000 feet to 10,000 feet in 5 minutes. So my question is,Can a passenger jet descend at 6,000 feet a minute safely
Guest Error404 Posted January 30, 2013 Posted January 30, 2013 My understanding is that a 738 climbs at around 3000 fpm depending on load, possibly in the 5's I believe so 6 isn't out of the question one could assume for a descent.
Guest Andys@coffs Posted January 30, 2013 Posted January 30, 2013 its all a function of time, assuming complete depressurisation then the OMG masks deploy and from that point you have a max of around 10 minutes to be under 10,000ft because thats how long the O2 sources wil last. If we assume crusing was around FL400 then you need to loose 30,000ft in 10 minutes or 3k per minute so 6k per minute seems a bit higher than needed.... but that said at 40k the O2 masks probably cant sustain consciousness in some of your passengers and if a passenger is feeling stressed by the situation, having the guy/gal next to him keel over isnt going to help in reducing that stress level.... so the lower you get to as fast as possible the less chance that someone will become O2 deprived and become all floppy.... I suspect that the limiting factor will be that you cant exceed a max velocity on the way down. throttles to idle and speed breaks are whats available to help limit speed on the way down Andy
Sapphire Posted January 30, 2013 Posted January 30, 2013 Guess there are no cyl. heads to crack on those a/c. Idle throttle, flaps, spoilers, air brakes, side slip-as long as done at limiting speeds.
biggles5128 Posted January 30, 2013 Posted January 30, 2013 Interestingly enough, I have an app on my phone which has radar tracking of aircraft etc, this app also sends an alert when an aircraft in the world squarks emergency codes. Yesterday I received an alert which when the app is opened, takes me to a satellite view with the aircraft superimposed over the top. This aircraft squared 7700 and I could see by the information provided in real time by the app that the altimetre was unwinding pretty rapidly, did not time the decent however remember thinking that it must have been a cabin pressure problem, as the aircraft defended to 11500 feet if I recall and I could see it diverting to Rockhampton. Great little app. I was able to watch my wifes aircraft all the way from Melbourne one time and saw it safely land in Brisbane. I could even see that it landed on 01.
Patrick Normoyle Posted January 30, 2013 Posted January 30, 2013 Maybe some clear air turbulance, even a feather will drop like a stone from FL400. That's my guess.
alf jessup Posted January 30, 2013 Posted January 30, 2013 In cruise it is probably doing 47500fpm (9 miles a minute) so bunting it over to make the houses look bigger shouldn't be an issue if it is controlled and the VNE isn't exceeded. I''m sure in an explosive decompression situation they will decend at 20,000fpm +- It will be the passengers that feel it the plane will be in it's own element. Alf
damkia Posted January 30, 2013 Posted January 30, 2013 The standard decent rate that was quoted by one of the QANTAS reps was given as 3000'/min. The aircraft had decompressive incident. The decent was from FL 40 to about 10 000 AGL in about 8 mins. Some of the early reports... http://www.couriermail.com.au/news/queensland/qantas-tight-lipped-on-why-737-plane-diverted-to-rockhampton-just-before-due-to-land-in-townsville/story-e6freoof-1226564425248 http://www.recreationalflying.com/threads/qantas-plane-makes-unscheduled-landing.56249/ Can a passenger jet descend at 6,000 feet a minute safely At the stated decent rate of 3000', yes, when you factor in the horizontal velocity and the "nose down" attitude of the aircraft supporting your seat. Next time you are in a plane try going to the loo and doing a bit of a jump on the way there while the A/C is at TOD just starting to descend. You can "lift off" for just a bit longer than you do on earth, not quite weightless, but "light"....
rgmwa Posted January 30, 2013 Posted January 30, 2013 I believe the space shuttle used to descend at 10,000 ft/min. rgmwa
Sapphire Posted January 30, 2013 Posted January 30, 2013 I believe the space shuttle used to descend at 10,000 ft/min.rgmwa It was a sreamline brick with very high wing loading. They wern't looking for thermals 1
GAFA Posted January 30, 2013 Posted January 30, 2013 It's been a while since flown then the 737, but from memory the target speed during an emergency descent was Mmo/Vmo with full speed brake out. In this config you will easy do 5000 fpm if not more.
Guest Howard Hughes Posted January 30, 2013 Posted January 30, 2013 Probably flight aware! It's not unheard of for jets to be able to descend at 6000+ fpm when required, I even know of one that can peg the VSI at 9000!!
Gentreau Posted January 30, 2013 Posted January 30, 2013 ......I even know of one that can peg the VSI at 9000!! But those were called Stukas, and they don't fly them anymore
facthunter Posted January 30, 2013 Posted January 30, 2013 There's two basic configurations / High and low speed. The latter is used if it is suspected there may e structural damage. You are usually doing it because there has been a loss of cabin pressure and oxygen is required but you can't be sure that everyone has got it so you need to get to fl120 rapidly and safely. ( sometimes 10,000') High speed is power off and full speedbrake, nose over to get Vmo/Mmo, whichever is limiting. Low speed is power off, speedbrake ext, slow to gear extend speed and lower gear and then go to Vle. You are suppose to turn off track and tell ATC what is going on. You don't wait to get a clearance out of your level but you could talk about it when you are not too busy. You both put on oxygen masks as well and make sure you have communication. It IS an" emergency descent". 6,000 fpm would be fairly normal, but I think I have seen more. Jets can descend at quite amazing rates. You can do a normal circuit( size) and be 10,000 feet on downwind. ( wait till you have a bit of time on the plane first) Nev 1 2
biggles5128 Posted January 31, 2013 Posted January 31, 2013 What's the radar tracking app? Sounds useful! The app is called Flight Radar 24, think it was a couple of bucks, great entertainment though.
Guest Howard Hughes Posted January 31, 2013 Posted January 31, 2013 But those were called Stukas, and they don't fly them anymore Actually the aircraft capable of such feats, is lovingly known as the 'Jew canoe' !!
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