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Florianopolis
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Posts: 312
Joined: Sun Mar 29, 2015 2:54 pm

737 Altitude Question

Sat Mar 10, 2018 4:21 am

This AA 737 from DFW to PSP cruised at 34,000 for the first half of the flight, and 24,000 for the second half.

Is this a pressurization problem, losing one pack maybe? If you lost RVSM and ATC didn't want to deal with you, would you end up that low?

Also, I'm sure their fuel burn was atrocious, but the ground speed went up a tick!
 
stratosphere
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Joined: Sat Sep 22, 2007 12:45 pm

Re: 737 Altitude Question

Sat Mar 10, 2018 5:03 am

Florianopolis wrote:
This AA 737 from DFW to PSP cruised at 34,000 for the first half of the flight, and 24,000 for the second half.

Is this a pressurization problem, losing one pack maybe? If you lost RVSM and ATC didn't want to deal with you, would you end up that low?

Also, I'm sure their fuel burn was atrocious, but the ground speed went up a tick!


Don't know about the 737 but the 757 you can lose a pack and it limits you to 31000. It could be RVSM related or turbulence related hard to say.
 
atcdan
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Joined: Tue Aug 01, 2017 6:52 am

Re: 737 Altitude Question

Sat Mar 10, 2018 6:31 am

I noticed many of the westbound departures this evening from DFW were filed at 260 which seems rather low. There could be a strong jet stream or as mentioned turbulence at the higher FL's.
 
Redbellyguppy
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Re: 737 Altitude Question

Sat Mar 10, 2018 7:19 am

It was super bumpy above 240 tonight within a hundred or so either side of ELP. We had to go down to 210 to find a bearable ride.
 
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TOGA10
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Re: 737 Altitude Question

Sat Mar 10, 2018 8:01 am

Redbellyguppy wrote:
It was super bumpy above 240 tonight within a hundred or so either side of ELP. We had to go down to 210 to find a bearable ride.

What does 'within a hundred or so either side of ELP' mean?
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
Redbellyguppy
Posts: 163
Joined: Sat Apr 01, 2017 3:57 am

Re: 737 Altitude Question

Sat Mar 10, 2018 9:10 am

A two hundred mile wide circle centered on El Paso...
 
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TOGA10
Posts: 184
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Re: 737 Altitude Question

Sat Mar 10, 2018 11:12 am

Gotcha, clearly wasn't fully awake this morning. Thanks.
The natural function of the wing is to soar upwards and carry that which is heavy up to the place where dwells the race of gods. More than any other thing that pertains to the body it partakes of the nature of the divine. - Plato
 
stratclub
Posts: 292
Joined: Fri Jan 05, 2018 10:38 pm

Re: 737 Altitude Question

Sat Mar 10, 2018 9:14 pm

Clearly Aviation needs an APL (Acronym Protection Program). Incident investigation: "When you say you lost a TR, do you mean a thrust reverser failed to deploy or you misplaced a transformer rectifier"?
 
travaz
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Re: 737 Altitude Question

Sun Mar 11, 2018 3:15 am

I was on a WN flight from DAL to PHX a few years ago and we stayed at 20,00 all the way because of jet stream and turbulence at higher levels. The pilot came on and explained why we were so low.
 
GalaxyFlyer
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Joined: Fri Jan 01, 2016 4:44 am

Re: 737 Altitude Question

Sun Mar 11, 2018 4:01 am

A few years, I was following another 605, CLT-SDL. Different operators due to m6 specific “mission”; but we took off next departure after them, not 3 minutes in trail. I landed at SDL a mite surprised I hadn’t heard them on the descent. There plane was being towed across the runway as we taxied to the ramp. Curious! At dinner, I asked how did they that far ahead. They manually tricked flight plan to fly at 220 until west of the Mississippi, then climb to 360 or something. My operator tries to minimize burn, not always time, so I went 360/400. They saved perhaps 20 minutes, burning 1,000 pounds more.

An airline plan would have costed it out and, perhaps, their total cost was less.

GF
 
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longhauler
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Re: 737 Altitude Question

Sun Mar 11, 2018 4:57 am

Depending on the bias one puts on the flight, sophisticated flight planning software will plan for minimum time or minimum cost, or a balance between the two. If the winds were planned to become very strong at higher altitudes, it is not uncommon to plan much lower altitudes to get out of the wind.

Also, the Flight Dispatcher can alter the flight profile depending on poor reported rides. If he knows it is very bumpy above FL240, he can force the flight down there for a smoother ride. (or as a pilot, we take the fuel he gives us to fly lower, then decide on whether we go down depending on current reports).

The flight planning software we use, will alert the dispatcher if shear values exceed 4 knots/1000' as that may indicate a rough ride. Or, it gets even more sophisticated ... our iPads will report (through the onboard wifi) a rough ride it senses and the exact position. That information is used when determining a smooth profile. (we have to be careful not to drop them when flying!)

With regard to losing a pack or bleed source. We used to be restricted to FL310 with only one. But in the last few years, that restriction was relaxed as long as the speed brakes were not MELed as well.
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
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Florianopolis
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Joined: Sun Mar 29, 2015 2:54 pm

Re: 737 Altitude Question

Sun Mar 11, 2018 5:24 pm

Thanks for the info, everybody.


longhauler wrote:
our iPads will report (through the onboard wifi) a rough ride it senses and the exact position. That information is used when determining a smooth profile. (we have to be careful not to drop them when flying!)


It's nice to see an example of technology making stuff better, and not just more complicated.

(Delta's iPad's are set to report "light chop" no matter what)
 
arcticcruiser
Posts: 216
Joined: Tue Aug 22, 2017 2:16 pm

Re: 737 Altitude Question

Sun Mar 11, 2018 6:01 pm

stratosphere wrote:
Florianopolis wrote:
This AA 737 from DFW to PSP cruised at 34,000 for the first half of the flight, and 24,000 for the second half.

Is this a pressurization problem, losing one pack maybe? If you lost RVSM and ATC didn't want to deal with you, would you end up that low?

Also, I'm sure their fuel burn was atrocious, but the ground speed went up a tick!


Don't know about the 737 but the 757 you can lose a pack and it limits you to 31000. It could be RVSM related or turbulence related hard to say.


The 757/767s I fly its 35.000’ single pack. Unknowing people tend to overestimate the increased fuel consumtion at lower levels. Mach speed (or KIAS) comes back as well so its not that bad.

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