View Full Version : Unpressurized flight

10th Oct 2009, 10:43
Hi gentleman:
Have you ever did a un-pressurized flight on a commercial jet? Beside to minimize climb and descent rate when departure and arrival, is there anything vital to be keep eye on? Thanks.:rolleyes:

10th Oct 2009, 13:32
I've done a lot of them in unpressurized airplanes...

What airplane in what environment are you talking about?

10th Oct 2009, 16:02
I suppose he means something like the Emirates A340 ferry flight from Melbourne to Toulouse at 10,000ft after that nasty tail strike... I hardly doubt there are many written procedures for this, I can't think of much that has to be taken care off - I guess the airframe is under a bit less tension (like a balloon with too little air) so possibly you have to limit loads a bit?!? Total stab in the dark, I'm probably wrong...

10th Oct 2009, 16:58
Lockheed ferried a Delta (ex-Eastern) L-1011 that had failed the aft pressure bulkhead over the Pacific, from LAX to Marietta, Georgia (Dobbins ARB) so it could be used in the Aging Aircraft Test Program. The crew reported lots of interesting GA chatter as thay would pass by at 10,000 feet.

10th Oct 2009, 18:14
World Airways ferried a MD-11 that had a gaping hole in the tail after a strike, N275WA from Montevedeo to Long Beach. Pretty sure they had to go on oxygen to make an Andes pass as well. Do not know how many legs they took.

10th Oct 2009, 18:42
Unpressurized flight in jet aircraft is really no problem. The biggest consideration is the higher fuel burn at lower altitude.

I ferried a 727 from California to OKC once that we could not pressurize, we used the O2 masks and flew back starting at FL27.0. About an hour out of OKC we ran out of O2 and descended to 9,000 feet for the rest of the flight. We climbed out at the normal rate of climb, but on descent I keep the rate of descent to around 1,500 feet per minute just for comfort.

Of course there was no passengers and it got pretty cold. We did have some bleed air coming into the cockpit, but not very much and the outflow valve was wired open. We had a multitude of probelms with the entire pressurization system, the outflow valve being just one of them.

10th Oct 2009, 20:31
Did it from SEA to MIA in the 727. It was a great two days of cross country flying. CAVU all the way:ok:. We laid over at a small municipal in (Columbia MO. (KCOU)). I think we got better treatment than if the suttle landed there. Fuel was never an issue as there were numerous airports along our route.

11th Oct 2009, 04:11
The crew reported lots of interesting GA chatter as thay would pass by at 10,000 feet.

What's GA ?

11th Oct 2009, 04:50
General Aviation. ie. Small aeroplanes.:ok:

11th Oct 2009, 09:10
General Aviation. ie. Small aeroplanes.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/thumbs.gif
Thanks for that.

13th Oct 2009, 15:40
I don't get why these planes flew at 10000 feet for any length of time. Is there no way the pilots could have used oxygen for the whole trip? The cost in fuel must have been astronomic.

13th Oct 2009, 19:27
I don't get why these planes flew at 10000 feet for any length of time


and it got pretty cold

Mind you, I could lend anyone my Dad's Irving jacket. But he said that his Lanc was so cold that he was still usually frozen stiff while flying it.

13th Oct 2009, 23:24
Usual practice unpressurised, but on oxygen, is to limit pressure height to FL250 to minimise the likelihood of untoward physiological problems.

7th Aug 2010, 02:36
Since our ears are kind of senstive to press change,What kind of mode do you use to climb or descent?vertical speed 500'fpm only or what?

7th Aug 2010, 03:55
It all depends upon what your company wants or allows.

We did a DP ferry and were allowed to got to FL250 on O2, no so bad.

We also did a ferry but were limited to FL100...... and hence 250kt.....
it took forever to get anywhere......:} multiple stops weren't bad though:E

If low, then no O2 and much higher fuel burn, less speed, much longer.

Depending upon why you are ferrying DP you will always get the , whats that noise.... have you heard that before paranoia that the thing is falling apart around you

just get the engineers to add more speed tape!:ok:

Capt Claret
7th Aug 2010, 11:25
After take off from Alice Springs some years ago bound for Darwin, in a 146, one of the outflow valves failed to close. Setting upnfor unpressurized flight, we were able to climb to FL110 and maintain the cabin < 10,000'. Additionally, we had sufficient fuel to make Darwin with reserves intact.

Shortly after making the decision to continue, the outflow unstuck, & the flight continued normally.

Alice had no spare parts, minimal engineering coverage, and the aeroplabe was full of folk who wanted to end up in Darwin, not return to Alice.

7th Aug 2010, 22:23
Usual practice unpressurised, but on oxygen, is to limit pressure height to FL250 to minimise the likelihood of untoward physiological problems

I met friend in Florida who had just landed his tactical jet following a flight from Puerto Rico. He had lost pressurization on climb and had elected to press on!:eek:

Despite breathing 100% oxygen, he was suffering from "the bends". Enroute altitude was in the mid 30s. Usually pre-breathing 100% oxygen 15 minutes at sea level gets rid of enough dissolved nitrogen to protect you but prior history of bends can make you more susceptible.

8th Aug 2010, 08:59
I did MEL/SYD in a B747 200 with pressurisation problems, with a full pax load. Pax were given the option of getting off and waiting for four hours or a low level scenic ride home. Most opted for the scenic ride. Whole trip was done below 10,000 feet and the pax were most impressed with the view.

8th Aug 2010, 09:54
Since the important issue has yet to highlighted here, I will explain,

I refer to the B737NG here, but this may apply to other types as well,

With the airplane below 16,000 feet, including on the ground, a vacuum compressor provides the required motive forces to flush the toilets,
Unfortunately, this compressor is provided with a pressure switch that shuts it off above FL160, with the cabin pressure differential taking over.
Again unfortunately, the vacuum compressor is not informed of the lack of cabin pressurization, and will continue to remain at rest in these circumstances.

The result is obvious, the toilets won't flush above FL160 without cabin differential pressure.

Just a thought....:uhoh:

8th Aug 2010, 11:37
...Melbourne to Toulouse at 10,000ft

- Christ that wouldnt be a ferry but a endurance test! :uhoh:

Ive had unpressurised trips on a few Boeing types and they
were no big deal. Bloodey noisey but watch you dont go over
1000 fpm on descent to protect your ears.

Havent done one yet on the Scarebus 320. Dont want to ether.