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Unpressurized takeoff

Old 24th Feb 2007, 14:25
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Unpressurized takeoff

Company policy is to takeoff with packs off until 1500'agl ; thereafter packs turned on. Any medical boffins care to comment as to what this might be doing to our ears if repeated four times a day, twenty times per month etc.
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Old 24th Feb 2007, 16:29
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I am not a doctor:

but can you at least tell us what kind of plane your are taking off in?

and, with some 12,000 hours, ALL flying is bad for your ears in one way or another.
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Old 24th Feb 2007, 17:30
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Flying a 319 - and with 13000 hrs I'm aware of what is good and bad - but the pressure spiking when packs are turned on ( ten second delay between pack one and two ) can't be good for the ears or ultimately the airframe.
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Old 24th Feb 2007, 18:38
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What's a pack?
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Old 24th Feb 2007, 19:17
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What's a pack?
http://www.boeing.com/commercial/cabinair/ecs.pdf
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Old 24th Feb 2007, 19:36
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I'm sure it can't be beneficial for you ... but my question is WHY ?
The 319 is not a particularly under powered aircraft - is it ?
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Old 24th Feb 2007, 19:57
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OK, this is more a technical question than a medical one, but I had always assumed that if you're pressurising to a particular level, you could just leave things open until close to that height and then close the valve and get it all going so that the pressure would then be maintained. I guess this would also give the same effect as kicking it off at 1500ft if it spikes, and also increase the chance of a repeat of the Helios incident where pressurisation didn't work.
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Old 24th Feb 2007, 21:44
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Could be a problem with passengers with "glue ear" (fluid in the ear) if you don't turn it on until a little higher.

This happened to me as a passenger on commercial flight to Canada. I boarded with glue ear (but passed fit to fly by a specialist)

On the climbout the Pilot apologised that there had been a pressurisation problem on takeoff and he hoped that no one had felt any discomfort.

Shortly after I thought something was dripping onto my neck from the overhead bin....

Later at A&E the cause of the perferated ear drum was put down as pilot error!

I didn't feel a thing.


Mickjoebill
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Old 25th Feb 2007, 00:32
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cheer up

one must ask why? is there a performance issue? why not ask the boss man to change the procedure or at least explain why?
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Old 25th Feb 2007, 03:31
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Done to increase Flex temp. for takeoff thereby reducing fuel burn and engine wear - we are a low cost airline.
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Old 25th Feb 2007, 07:01
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to increase Flex !?!

WOW - that's pretty severe !
And as someone else said above, is it really worth risking a Helios ?

I doesn't take long to climb through FL100 (especially with no packs on)

For whats its worth, I've worked for 3 low cost airlines (on three different types) and it was NOT SOP to depart packs off - nor do I know of any other airlnes (in the UK at least) that requires this to be done.

Can you say who you are flying for or where you are based ?

Last edited by AltFlaps; 25th Feb 2007 at 07:12.
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Old 25th Feb 2007, 08:32
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It's standard procedure on the 747-400 I fly. Packs on (one at a time) after CLB1 annunciated - usually Flap 5 achieved or 1000' AAL if Noise abatement take off used. Fuel saving and engine wear are the reasons quoted....

Last edited by ETOPS; 27th Feb 2007 at 04:42.
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Old 25th Feb 2007, 08:54
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Unpressurized takeoff

It is standard practice on the B747 -200/300 to switch on the first pack at 400' after takeoff then packs 2 and 3 on after climb power has been set.
However if OAT is above 25deg and you are not performance limited, then take off is done with one pack on.
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Old 25th Feb 2007, 12:47
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I have done packs off takeoff on the 737 and always thought it was BS and they should have just put bigger engines on the thing

the douglas dc9 ...we never did packs off takeoff unless one pack was just out of service and then it was just one pack on .

now on that plane (dc9) if an engine quit, the packs would trip off to get max blast from the engines.

cheer up, quite honestly, I can't stand the way modern planes and airlines are finding ways to save money.

I don't know what the laws are in your country, but if your ears go bad, I hope you can sue!
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Old 26th Feb 2007, 12:28
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I have to agree with Mickjoebill this indeed could be a serious Medical Problem in the making even for those who are aware of their medical conditions.

What happens to those that aren't aware????

Sorry Mrs Smith but poor old Johnnies head exploded but hey we'll have the Technical Fault dealt with on the next leg! have a voucher for a free meal!

mickjoebill

Could be a problem with passengers with "glue ear" (fluid in the ear) if you don't turn it on until a little higher.



Another post again stress to the Airframe not good!

Have we learnt are lessons truly from the comets days when Britain ruled the world briefly with the first jet powered passenger jet!

sensationalism I know couldn't resist but the fact remains..............
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Old 27th Feb 2007, 06:56
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Altflaps - can't get a Helios situation - Ecam warning triggered if you haven't reconfigured after takeoff. To figure out which low cost airline operates this sop - well that's easy.
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Old 27th Feb 2007, 09:40
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[QUOTE=cheer up;3144260Any medical boffins care to comment as to what this might be doing to our ears if repeated four times a day, twenty times per month etc.[/QUOTE]

Obviously, none.
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Old 27th Feb 2007, 14:28
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Reading the stuff on "Packs," it's clear that this is a fairly specialised area, and it's difficult to answer your question specifically.

An ENT man may hazard some type of guess as to the long term effect of repeated pressure changes on the ear drum, but to be fair, it'd probably be a guess, or at best, based on limited experience.

I'm not a specialist, and rarely fly above 1500 feet, but I guess "boyles law" shouldn't be an issue if the old eustachians are draining adequately- although I'm basing my assumption on theory, not experience. (I guess, from previous posts, most pilots fly when "bunged up.")

Another starting point may be to examine whether or not any studies have been performed in this area- a quick look at "Medline" revealled stuff like this http://www.ncbi.nlm.nih.gov/entrez/q...=pubmed_docsum


Medline can be a bit of a pain to use, and be aware that it contains the good, the bad and the ugly,but if your keen to answer your question, it's a good starting point.

cheers
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Old 27th Feb 2007, 16:47
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I use to (be obliged by SOPs) leave the packs off until some point down the after take-off checklist. I often saw 2,000 fpm displayed on the VSI, and the cabin wasn't far behind.

This is not a good practice, except that, saving engines/fuel/money, is I suppose, the green thing to do.

Passenger's ears are in danger. So many folk, me included, never in their lifetime, equalize quickly. Some are very slow.

Doing anything, you don't have to, in those critical moments while lumbering into the air, is perhaps counter-productive to safety.

The aircraft is fractionally weaker.

The change in the engine bleed parameters during high power settings, probably negates the saving on the extra flexi. I frankly don't know, but my guess is that there are a lot of internal fluctuations--just at a time that you want total engine stability.
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Old 27th Feb 2007, 16:55
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There is no operational necessity in any modern jet airplane that precludes the use of packs below 1500feet AGL; it's obviously an SOP issue, certainly not an operating limitation.
Most air carriers' SOPs call for at least one pack to be turned on between 400 and 1000 feet AGL.
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