Virgin's Presurisation
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Jindavik.
To answer your question the system used in these aircraft are automatic and the cabin differential is programmed to a maximum cabin altitude of about 8000 feet (at max cruise altitude of about FL410 for the 737-800).
If cruising at a lower level the cabin altitude will be lower.
Typically any pain experienced in case of inner ear infections/colds and/or eustachian tube blockages will be more noticeable whilst descending while the gases are trying to escape the body.
The system is programmed for around 300-500 feet per minute on descent which is quite comfy for the pax.
It sounds like the people affected all flew with head colds, inner ear infections or similar.
The B737 is the most popular passenger jet in the world so if this was an endemic problem with VB all pax would complain which they dont.
Coincidence maybe, but whilst pax are warned not to fly with a head cold it is quite obvious alot of pax are either ignorant of the effects of flying as described or ignore warnings.
To answer your question the system used in these aircraft are automatic and the cabin differential is programmed to a maximum cabin altitude of about 8000 feet (at max cruise altitude of about FL410 for the 737-800).
If cruising at a lower level the cabin altitude will be lower.
Typically any pain experienced in case of inner ear infections/colds and/or eustachian tube blockages will be more noticeable whilst descending while the gases are trying to escape the body.
The system is programmed for around 300-500 feet per minute on descent which is quite comfy for the pax.
It sounds like the people affected all flew with head colds, inner ear infections or similar.
The B737 is the most popular passenger jet in the world so if this was an endemic problem with VB all pax would complain which they dont.
Coincidence maybe, but whilst pax are warned not to fly with a head cold it is quite obvious alot of pax are either ignorant of the effects of flying as described or ignore warnings.
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I always thought it better to ask a dumb question than make a dumb mistake so, if you are flying at 20k or 30k feet etc what cabin pressure should I be feeling 5000' of 8000' ? Just a dumb question so Props don't get sh!tty just a simple answer will doThanks
A.H.
A.H.
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Jindo,
Have you given any of this feedback to your medico?.
He may become a ppruner.
If so, maybe you could ask him some more specifics on this inner ear bleeding. Which side of the eardrums, flow, other surrouding inflamations etc etc. Just finished a dive course in cairns?
What previous history did these particular patients have of ear problems. Did they also notice a change of taste when vegemite was sold?.
It's interesting that it's been mentioned, but I doubt the aircraft has anything to do with it. Or the operator. Virgin operate B737 aircraft the same as alot of other airlines, they would also be reporting similar problems.
I'm continuously amazed by the misconceptions of the average punter. I had a guy sitting next to me one day tell me that they wind the engines up on turnaround for the next start. He'd seen the fan windmilling and worked it out by himself.
Were any first flyers?
Have you given any of this feedback to your medico?.
He may become a ppruner.
If so, maybe you could ask him some more specifics on this inner ear bleeding. Which side of the eardrums, flow, other surrouding inflamations etc etc. Just finished a dive course in cairns?
What previous history did these particular patients have of ear problems. Did they also notice a change of taste when vegemite was sold?.
It's interesting that it's been mentioned, but I doubt the aircraft has anything to do with it. Or the operator. Virgin operate B737 aircraft the same as alot of other airlines, they would also be reporting similar problems.
I'm continuously amazed by the misconceptions of the average punter. I had a guy sitting next to me one day tell me that they wind the engines up on turnaround for the next start. He'd seen the fan windmilling and worked it out by himself.
Were any first flyers?
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300fpm with 8000 cabin = 27 minutes to descend cab. to sl, average speed on descent 6 miles a minute= start descent at 160 miles, a little early especially if at FL300
I thought 500fpm was std
I thought 500fpm was std
Timmee,
Not correct. The problem for flyers is that the "gases" ie the increasingly dense atmosphere is trying to get IN, not escape. If the eustachian tube is blocked eg a cold the eardrum collapses inward, causing the pain. When you get the eustachian tube open somehow eg yawn, cough, chew, air is let into the middle ear and and all is equalised.
I don't know where you get this idea from: 500ft a minute is quite harsh as far as I am concerned. For someone who very rarely flies (like some of these "new" Virgin pax) 500ft per min could be a real problem, and that doesn't mean only if they have a cold. If you asked joe public how they defined a cold, they would probably say in bed on panadol: that's a far cry from what we know can cause big issues with ears in aeroplanes, especially if the standard rate is 500ft per min. A simple runny nose without the correct ear-clearing procedure down the hill will cause problems.
Typically any pain experienced in case of inner ear infections/colds and/or eustachian tube blockages will be more noticeable whilst descending while the gases are trying to escape the body.
The system is programmed for around 300-500 feet per minute on descent which is quite comfy for the pax.
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I have just wrestled the computor off my daughter. I reckon the jury's in. All those punters who caught the greyhound bus are moving on to low cost airlines colds and all. V.B has attracked a lot of new flyers (good on V.B) but there is a whole new bunch of punters that need educating re: flying with head colds. That is what Iwill tell my quack.
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Harden up.......
500 ft/min is nothing outrageous. What did you do in pistons (if you flew them)? You have to come down eventually. And 500 ft/min is what is taught unless things have changed lately. On the winjeel it was 1000 ft/min.
And if you notice discomfort? That's what the valsalva manoeuvre is for.
500 ft/min is nothing outrageous. What did you do in pistons (if you flew them)? You have to come down eventually. And 500 ft/min is what is taught unless things have changed lately. On the winjeel it was 1000 ft/min.
And if you notice discomfort? That's what the valsalva manoeuvre is for.
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By my reckoning Bloggs, if your machine descends the cabin at 300fpm and assuming an 8000' cabin, you would need to descend 27 minutes prior to landing ( into an SL A/D ), even @ average GS 300, that's still 130 odd miles TOD. ( and I happen to know that your machine doesnt have excess diff to play with )
I would have thought that a wee bit too far away when crzing 28000.
I would have thought that a wee bit too far away when crzing 28000.
Cunning,
27.5 minutes, because one has to "catch the cabin" at 200ft so that the machine doesn't land pressurised. 130nm is a tad too far away, but that's what you have to do for 300ft/min. We "use" 500ft/min (as you know??!!) so we descend closer in than 130nm. Descent points being too close? Don't get me started!
Itchy,
It may be OK for for ex-RAAFees, but Joe Public wouldn't know what the valsalva manoeuvre was (and neither, possibly, do the "experienced" chooks in the back) so the first thing they know is they have sore ears or worse.
Besides, pax in pistons were probavbly so terrified of what might happen generally they didn't worry about their ears!
737 Drivers,
What does happen to your cabin rate of descent if you descend late? Does it/can it exceed 500fpm or this simply not possible because of descent path/drag issues?
27.5 minutes, because one has to "catch the cabin" at 200ft so that the machine doesn't land pressurised. 130nm is a tad too far away, but that's what you have to do for 300ft/min. We "use" 500ft/min (as you know??!!) so we descend closer in than 130nm. Descent points being too close? Don't get me started!
Itchy,
It may be OK for for ex-RAAFees, but Joe Public wouldn't know what the valsalva manoeuvre was (and neither, possibly, do the "experienced" chooks in the back) so the first thing they know is they have sore ears or worse.
Besides, pax in pistons were probavbly so terrified of what might happen generally they didn't worry about their ears!
737 Drivers,
What does happen to your cabin rate of descent if you descend late? Does it/can it exceed 500fpm or this simply not possible because of descent path/drag issues?
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Itchy Bum. Where on earth did you get that figure of 1000 fpm for a Winjeel? Your instructor must have been pulling your leg...The aircraft was designed for RAAF training including aerobatics. Try diving to get the required speed for a roll-off-the top and you can betcha the rate of climb and descent during that manoeuvre will be way in excess of 1000 ft per minute. If carrying a passenger other than aircrew types, we used good airmanship and tried to keep en-route descent rates to a reasonable figure (3-500 fpm to prevent ear pain.
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Yes I know all that. But as a student at 1FTS we never carried any passengers.
And I didn't realise you'd mistake that quoted RoD as anything other than that... "descent rate". Who looks at VSI during aeros??? I could be wrong, it was a while ago but I seem to recall Performance was gained from a Power plus an Attitude including when diving for speed for a Roll-off-the-Top. Nothing to do with RoD??
I wasn't talking about anything to do with roll-off-the-top, loop, stall-turn or any other aerobatic maneouvres... I never tried anything that fancy when recovering back for a re-join!!!
If you flew the Winjeel "operationally" then you have experience beyond mine and I'll take your word for it the techniques employed were different to the rigid processes at 1FTS.
And I didn't realise you'd mistake that quoted RoD as anything other than that... "descent rate". Who looks at VSI during aeros??? I could be wrong, it was a while ago but I seem to recall Performance was gained from a Power plus an Attitude including when diving for speed for a Roll-off-the-Top. Nothing to do with RoD??
I wasn't talking about anything to do with roll-off-the-top, loop, stall-turn or any other aerobatic maneouvres... I never tried anything that fancy when recovering back for a re-join!!!
If you flew the Winjeel "operationally" then you have experience beyond mine and I'll take your word for it the techniques employed were different to the rigid processes at 1FTS.
Moderate, Modest & Mild.
Vb's Boeing 737 pressurisation system is no different to EVERY other operator of the same equipment - including QANTAS.
Just to clear up a previous Q & A by A.H. and HotDog respectively - the cabin altitude at 20k is MUCH lower than that at 30k, at lower levels the cabin altitude is maintained at sea level (or close to) in the case of Oz & N.Z.
Cabin altitude usually increases with actual aircraft height, and at 20k actual, (without reference to the table) the cabin altitude remains at almost (in the case of Oz & N.Z.) sea level, so there is NO discernible effect.
8,000 feet cabin altitude is the MAXIMUM, and - depending on each individual aircraft types max ceiling (e.g. 37,000' or 45,000') - that will be the max. cabin alt.
From Capn Bloggs, "What does happen to your cabin rate of descent if you descend late? Does it/can it exceed 500fpm or this simply not possible because of descent path/drag issues?"
It is possible for the aircraft to "catch" the cabin with high speed (high actual ROD's), in which case the cabin will descend at the same rate as the aircraft.
However, with the 250 knot below 10,000 restriction, this hardly ever happens.
For people not familiar with the valsalva manoeuvre (holding your nostrils and exhaling against them), drinking, or chewing and swallowing has the same effect. (That's the reason candies/lollies are handed out prior to/during descent, by the F/A's
).
Likewise babies crying on descent should be ENCOURAGED by cabin crew, as it gives them relief - better still, try to get Mum to stick the baby on the tit.
Works for me EVERY TIME
Edit - To clarify, cabin "pressure" changed to cabin "altitude".
Just to clear up a previous Q & A by A.H. and HotDog respectively - the cabin altitude at 20k is MUCH lower than that at 30k, at lower levels the cabin altitude is maintained at sea level (or close to) in the case of Oz & N.Z.
Cabin altitude usually increases with actual aircraft height, and at 20k actual, (without reference to the table) the cabin altitude remains at almost (in the case of Oz & N.Z.) sea level, so there is NO discernible effect.
8,000 feet cabin altitude is the MAXIMUM, and - depending on each individual aircraft types max ceiling (e.g. 37,000' or 45,000') - that will be the max. cabin alt.
From Capn Bloggs, "What does happen to your cabin rate of descent if you descend late? Does it/can it exceed 500fpm or this simply not possible because of descent path/drag issues?"
It is possible for the aircraft to "catch" the cabin with high speed (high actual ROD's), in which case the cabin will descend at the same rate as the aircraft.
However, with the 250 knot below 10,000 restriction, this hardly ever happens.
For people not familiar with the valsalva manoeuvre (holding your nostrils and exhaling against them), drinking, or chewing and swallowing has the same effect. (That's the reason candies/lollies are handed out prior to/during descent, by the F/A's
).Likewise babies crying on descent should be ENCOURAGED by cabin crew, as it gives them relief - better still, try to get Mum to stick the baby on the tit.
Works for me EVERY TIME
Edit - To clarify, cabin "pressure" changed to cabin "altitude".
Last edited by Kaptin M; 9th Jul 2004 at 02:34.
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Kaptin M,I think that your answer wrt AH and Hot Dog is incorrect insofar as the "cabin pressure" at 20k is actually higher than at 30k.The confusion lies in that the "differential" (dependent on system and schedule) may be lower,however the actual cabin pressure will be higher.If we refer to the cabin ROC during climb we will find that it is(normally) indicating an increase in cabin altitude relative to its datum which is its departure field altitude,and will continue to do so until it reaches max diff. When on descent the cabin ROC will indicate a decrease in cabin altitude.I say "normally" above, because if your departure altitude is greater than your destination altitude eg. CBR-SYD,even though you climb out of CBR the pressurisation will descend the cabin to destination through isobaric hold,etc.The confusion arises in that we are actually controlling the rate of "depressurisation" and then limiting it to a maximum differential,and then on descent controlling the rate of pressurisation to return the differential to zero.I remember once being told that "airconditioning is the control of supply of air to the cabin and pressurisation is the control of exhaust of the supplied air" or words to that effect.
Cheers
Cheers
