flaps30
Posts: 187
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Cruising At FL410 On Short Flights

Wed Jun 14, 2000 1:08 am

I hope some airline pilots who fly frequently within California could answer some questions I have. While on a stopover at SJC, I listened to some clearance deliveries and noticed that some flights going to S. California (Ontario, Burbank, Orange County) had been assigned a cruising altitude of FL410.
With a cruising altitude that high, how long does it take to reach that altitude, and at what point along the flight do you begin the initial descent for, say,
Ontario airport? I suppose Avenal VOR is a little too soon to begin the descent, but it can't be too far past that, otherwise you'd fly right over Ontario airport.

I get the feeling that if the aircraft is relatively heavy, a 1-hour flight with FL410 as the cruising altitude is like driving a car over a mountain- half the trip is spent just climbing to the summit, then the other half is spent descending to the airport.

Thanks for any replies.

Flaps 30
every day is a good day to fly
 
cedarjet
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 2:20 am

You're right about the trajectory (up and down), in fact when I did a jumpseat ride from Heathrow to Paris CDG we were at cruising altitude (I think about 25,000 ft) for precisely 120 seconds! Then we started down again.

Those FL410 flights you mention are almost certainly bizjets, which have much better performance than big airliners, and commonly cruise at at least 41,000 ft on most flights. I have never heard of any short haul airliner getting that high even on a long flight - maybe 747SPs, 767ERs, 744s et al but no way would a 737-200 get within a mile (literally, almost) of FL410+.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz
 
timz
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 7:04 am

I've heard 757's climbing to 410 on SFO-LAX and SFO-SNA. Haven't listened enough to the 737-700's to know if they do the same, but I suspect they usually don't.
 
Guest

RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 10:41 am

The 737 can't do 41000. I think the 737NG can go up to 41000, the 737-100 to -500 can only do 35000.

The basic rule is the higher an altitued the aircraft acieves on a flight, the less overall fuel you use - even if the flight is short and you spend hardly any time at that altitude.

My shortest cruise was on a BA 757 LHR-MAN flight where we cruised at 24000ft for exactly 3 seconds!
 
mcomess
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 10:58 am

You're certainly right in that it doesn't make sense, practically or economically for an airline to operate short haul at FL410, even if the aircraft is certified to do so. I've only made it up that high once, and it was on a 767 or 757 (can't remember) due to weather. Although the fuel burn rate is cut drastically, pilots avoid doing this, as often the winds can often get quite high up there- high enough to justify staying at a lower altitude and sacraficing the fuel burn. I have an MD-83 flight manual laying around here where there is actually a guide to determine the benefits/costs of swiching to higher altitudes while inflight. Was there significant weather in your area when you heard this? Nonetheless, I have found that airlines prefer to reroute or request vectors around weather, instead of climbing above it.
 
desertjets
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 12:19 pm

If I remember correctly the 757 is among the only few commercial aircraft that can fly up at 41000'. The 737NG is certified to 37000 and the A320 to 35000.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia
 
albatross
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 1:03 pm

Max Cruising Alt for 737NG is 41000; Max Cruising Alt for 777 is 43100
 
Gnomon
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737NG Service Ceiling

Wed Jun 14, 2000 1:04 pm

The 737NG is certified to a service ceiling of FL410, not FL370. In fact, I hear that Southwest routinely operates its 737-700s at FL410 when winds permit to minimize fuel consumption on medium- to long-haul eastbound flights. There's a trip report on the general aviation forum involving a SW -700 cruising from MDW to somewhere on the East Coast at FL410...check it out. It's a well-written post, although I can't remember the author. But, yes, 737NGs are certified to FL410 - and not an inch higher.
 
Panman
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RE: 737NG Service Ceiling

Wed Jun 14, 2000 5:56 pm

Gnomon wrote:
-------------------------------
But, yes, 737NGs are certified to FL410 - and not an inch higher.

I don't know where you got that 'not an inch higher' info from.

The main reason why commercial airliners have a service ceiling is mainly to do with cabin pressurisation. Up to the service ceiling the pressure controller is able to maintain a cabin altitude of 8000ft. Above that the altitude of the cabin will climb at the same rate as the aircraft. If the aircraft does go over it's service ceiling then the PSUs will activate (i.e. the oxygen masks will drop for the passengers) and the pilots will have to turn their oxygen supply system to 100% oxygen. [I remember reading somewhere that over 40,000 ft (I think) one of the flight crew must have his oxygen mask on and set to 100% oxygen (in case of cabin depressurisation and incapacitation of the other pilot).]

So though the 737NG may have been certified to a service ceiling of 41,000 ft, it can fly as high as it's engines will enable it to.

PANman
 
BigGiraffe
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RE: Cruising At FL410 On Short Flights

Wed Jun 14, 2000 7:55 pm

Well, I'm confused. I thought service ceiling was based on controllability?
 
dnalor
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RE: Cruising At FL410 On Short Flights

Thu Jun 15, 2000 1:33 am

I'm sure I have been on a 737 300/400 upto 37000 if not 39000!
 
mcomess
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RE: Cruising At FL410 On Short Flights

Thu Jun 15, 2000 3:16 am

Service Ceiling and Max Structural Ceiling are two different things.

Service Ceiling is a published figure that the manufacturer recommends to airlines to be used for maximum performance and reliability over several years of service. Max Structural Ceiling, on the other hand, is the maximum altitude you can get the airplane up to before parts of the wings begin to come apart. This is usually not published, as the manufacturers get this data by testing models, making predictions, etc., not by testing an actual aircraft as they do with the Service Ceiling data.
 
BigGiraffe
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RE: Cruising At FL410 On Short Flights

Thu Jun 15, 2000 5:47 am

Max Structural Ceiling? The wings begin to come apart?

Not. There is no such thing as max structural ceiling, and wings do not come apart at high altitude. The airplane ceases to climb when the engines can't put out enough thrust, but that is not a structural issue.
 
prebennorholm
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Max Structural Ceiling

Thu Jun 15, 2000 6:03 am

Max structural ceiling, where wings fall apart...!
No no, that's wrong, it is Min Strutural Ceiling where everything comes apart. And that's the same altitude for all planes, just about zero feet above ground level - and not one inch lower  
Always keep your number of landings equal to your number of take-offs
 
VC-10
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RE: Cruising At FL410 On Short Flights

Thu Jun 15, 2000 6:14 am

Max Structural ceiling, if there is such a term, will be based on the max differential pressure that the fuselage can take. The differential pressure being the difference between the pressurised cabin and the ambient pressure. As a general rule the fuselage will be designed for a max diff of about 9.5 psi. In normal ops max diff is about 8 psi

Pressuristion Controllers will be able to control cabin rate of climb above FL410, the outflow valves will just close more. The limiting factors will be how quickly the engines can pump air into the cabin and the max diff limit.

The 'rubber jungle' will only drop out if the cabin alt exceeds 14 000 ft or if manually selected.

One or two posts have mentioned the fuel saving benefits of flying at high altitude, this has to be balanced against the fuel burnt to get to that altitude
 
timz
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737 Ceilings

Thu Jun 15, 2000 7:19 am

According to Jane's the 737-200's maximum pressure differential was (and is, we suspect) 7.5 pounds per square inch. Since this is the difference between the standard-day pressures at 8000 ft and FL350, the latter figure becomes the certified ceiling for that model. Although Jane's gives the same figure for the 737-300, I've heard them climbing to FL 370, so apparently Jane's isn't perfect.

Incidentally, the 727 is allowed to climb to FL410 (or maybe 420?), but I've never heard one actually get up there.
 
Gnomon
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Panman

Thu Jun 15, 2000 1:19 pm

Regarding your post a couple days ago:

I'm perfectly aware that the aircraft can fly far in excess of FL410, structurally. I said it is "certified" to fly to FL410. "Certified" means that, on the various legal documents issued by the manufacturer, FAA, etc., the aircraft is permitted to fly to FL410 in normal passenger-carrying activities. I'm sure that, on occasion, it does actually reach maybe 41,000 feet and 3 inches...

But there are structural components that figure into that altitude, including the maximum pressurization differential, which can exert stresses on the airframe that must be within certain structural limits during normal pax-carrying flights. I'm sure that FL410 would stress the airframe, and I'm sure that FL430 wouldn't, either, but there's a margin of safety built into that number.

And I didn't mean "not an inch higher" literally.
 
AAR90
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RE: Cruising At FL410 On Short Flights

Thu Jun 15, 2000 1:51 pm

Back to the original questions:

>With a cruising altitude that high, how long does it take to reach
>that altitude,

Without restrictions (traffic or lack of ATC clearance, etc.) AA's 757s can reach FL410 in about 17-20 minutes for normal N/S Calif. flights. Quickest I've done was 16 minutes from brake release at SNA and that was with derated climb power up to FL310!

>...and at what point along the flight do you begin the initial
>descent for, say, Ontario airport? I suppose Avenal VOR is a
>little too soon to begin the descent, but it can't be too far
>past that, otherwise you'd fly right over Ontario airport.

Prior to Avenal as there are some altitude restrictions on the ONT arrivals.

>I get the feeling that if the aircraft is relatively heavy,

Light, not heavy. This is very short flight for a 757.

Someone else writes:
>Those FL410 flights you mention are almost certainly bizjets,
>which have much better performance than big airliners, and
>commonly cruise at at least 41,000 ft on most flights.

I am constantly restricted in both climb and speed by slow climbing and slow flying business jets. Guess it depends upon what type of bizjet and how it is loaded. OTOH, I've never knowingly been holding up a bizjet.  

*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
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Bruce
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RE: Cruising At FL410 On Short Flights

Mon Jun 19, 2000 5:27 am

When you talk about altitudes, why do you differentiate between east-west flights and other flights? Is there different altitude restrictions between north-south and east west flights?
and what if your flight is actually a southeast to northwest direction flight - then which rule do you follow?
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Pacific
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RE: Cruising At FL410 On Short Flights

Mon Jun 19, 2000 5:36 pm

I'm under the assumption that cruising speeds are under Mach speeds and not a fixed speed. As the speed of sound is slower at FL410 compared with FL350, if you have to fly longer, would the plane burn more fuel at the end due to the longer flight time?
Embarracing Question- How do you convert knots into Kph or Mph?
 
timz
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Knots Etc

Tue Jun 20, 2000 3:45 am

Since the nautical mile is based on the size of the earth (which is not spherical) there have been various "nautical mile"s in the past, but I think it's now defined as 1852 meters exactly. Since the statute mile is exactly 1609.344 meters that makes the conversion factor knots-to-mph 1.1508.

Yes, most airliners do have a slightly lower airspeed at FL410 than at 350, but the fuel burn per mile is almost always lower, wind etc being equal.
 
Guest

A320 Cruise Level

Thu Jun 22, 2000 5:36 pm

I always hear A320-200 cruising at FL390 here in Australia (Above the ceiling altitude someone mentioned above). I also have experience FL370 myself in a B737-300 which proves that the service ceiling altitudes are only a guide for an airline. Obviously the more modern an aircraft is the best performance or cruise altitude it would have!

Steve.
 
timz
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Only A Guide?

Fri Jun 23, 2000 9:56 am

Yes, the A320 is allowed FL390, and the 737-300 can go to 370, but I doubt that those ceilings are "only a guide". If some airline did decide to start flying an airliner higher than its certificated ceiling, somebody is supposed to object-- don't ask me who.

I think the Comet was allowed to climb higher than the A320, but most people would consider the A320 the more modern aircraft. Ditto the 727 and 707.
 
Citation
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Boeing Max Operating Altitudes

Sun Jun 25, 2000 7:55 am

The FAA Type Certificate Data Sheets list the following Maximum Operating Altitudes in their operating limitations sections:
707 42,000 ft.
727 42,000 ft.
737-100, 200 35,000 ft, unless 37,000 ft is authorized by Flight Manual
737-300, -400, -500 37,000 ft.
737-600, -700, -800 41,000 ft.
747-100 -200, -300, SR, SP, -400 45,100 ft
757-200, -300 42,000 ft
767-200, -300 43,100 ft
777-200, -300 43,100 ft.

Cessna Citations are certified to either 45,000 ft or 51,000 ft depending on the model.
 
Citation
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DesertJets

Sun Jun 25, 2000 8:06 am

All of the Boeing aircraft EXCEPT the 737-100 thru -500 have max operating altitudes HIGHER than 41,000 ft. This includes the 707, 727, 737-600 thru-800, all 747s, all 757s, all 767s, and all 777s.
The 757 max operational altitude is 42,000 ft.
 
Guest

Highest Altitude You Have Heard For 744?

Tue Jun 27, 2000 5:39 pm

What is the highest altitude anyone has seen or heard on their scanner that a Boeing 747-400 has cruised at?
 
B727-200
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RE: Cruising At FL410 On Short Flights

Fri Jun 30, 2000 2:39 pm


All B767 operations between MEL-SYD (and v'v) are conducted at FL410 (both AN and QF). This is only a 65 min sector.

I have been in the jumpseat though a couple of times and found it quite interesting. Even though the autopilot has been set to 41,000 ft. I have never seen an aircraft go this high. They seem to stop around 40,400.

Of the 65 min, only about 10 min is spent at cruise altitude FL410. From this level they seem to start decent at around 220km out, and based on the cruise time, would mean it takes about 330km to get to this altitude.

These are just observations I have made, with not really much science behind it.

Rgds,
B727-200.
 
Skystar
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RE: Cruising At FL410 On Short Flights

Fri Jul 07, 2000 7:20 pm

Okay,

The Operating Ceilings for aircraft that I am familiar with.

B733/4/5 - FL370
B762/3 - FL430
A320/319/321 - FL391
A330/340 - FL410
B744 - FL450

Now, how do they work out the operating ceiling. As some have mentioned, aircraft are certainly capable of higher altitudes, but there are pressurisation considerations.

The main issue with operating ceilings is pressurisation related. It is the time it takes from the ceiling to a safe cruising altitude (where we can all breathe). It's not as simple as just pointing the nose down 90° - because that presents you with another problem - aircraft speeds/airspeeds. So, to combat that, we have spoilers. Spoiler panels/systems add weight, so one must make a compromise between operating ceilings and weight. Naturally, these are only part of several factors that contribute to an aircrafts ceiling.

B744s rarely ever get to FL450. I recall the QF LHR-SYD "Longreach" flight got to FL450 over WA. QF's 747SPs also would get to FL450 somtimes for the last two hours on LAX-SYD services.

I don't know how long the US sectors that you are talking about are, but as someone has mentioned B767s routinely get to FL410 on the short Australian hops on the eastern seaboard. MEL-SYD-BNE. MEL-SYD is ~706km by air (well, according to Ansett Global Rewards). Your equivalent A320 would get up to FL370-390.

Cheers,

Justin
 
richie
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Joined: Wed Dec 22, 1999 10:28 pm

RE: Cruising At FL410 On Short Flights

Fri Jul 07, 2000 10:16 pm

It actually makes a lot of sense taking airplanes higher on short routes than on the long ones (at least in the beginning).

Flight Ops manuals show you a best altitude (and the FMS does so too) at a certain gross weight. Now even the mighty 747-400 is not routeinely flown much above FL270 in the initial part of a very long haul (12 hrs plus), as you would have to burn so much fuel to just keep it there, that this would not make any sense. If now you fly the same aircraft overa very short stretch (1hr or so), it may make a lot of sense to get it high, as the climb is going to be very short because the gross weight is so low. And, up at FL410 the engines are burning almost nothing (compared to the FL270 of the long haul), again due to the fact that the aircraft is very light. Decent does not matter, as most of the time you descent with flight idle only anyway.

Where exactly it starts making sense to go to what FL is a complex question, but that's why dispatchers have their computers for. Thumb rule, the lighter the higher.
 
nikonman
Posts: 223
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RE: Cruising At FL410 On Short Flights

Sat Jul 08, 2000 3:24 pm

I've never heard of planes going to Burbank and Ontario going to 41000. They normally cruise at 29000 up to 33000. I have flown on Alaska's NGs to and from SJC and we were at 41000 and 40000.

Higher than a kite you could say...

 
Guest

Where The Ratings Come From

Sat Jul 15, 2000 12:51 pm

Per a friend of mine who was a 737-300/500 pilot, the 300/500 (and I assume 400) is rated at 37,000 feet simply because of how long the emergency oxygen supply will last.
Any 737 pilots care to comment?

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