Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Altitude Of 39000 Ft  
User currently offlineSNBru From Belgium, joined Feb 2005, 168 posts, RR: 0
Posted (8 years 9 months 3 weeks 5 days 15 hours ago) and read 8858 times:

My last SN flight was a BRU-TLV flight with an A319. The onboard route information screen informed us that we were flying at 39.000 ft. This is the highest altitude I ever noticed on a flight I guess.

My question: what is the maximum altitude for normal operated commercial flights and isn't an altitude of 39.000 very high compared to the average 33.000 ft?
How is the optimal altitude defined?

Thanks

34 replies: All unread, showing first 25:
 
User currently offlineZSOFN From United Kingdom, joined Jun 2005, 1412 posts, RR: 6
Reply 1, posted (8 years 9 months 3 weeks 5 days 13 hours ago) and read 8838 times:

39K is actually quite normal. EZY routinely fly their 73Gs (not been on their A319s yet) at 38/39k. Older a/c like F100s, DC9s etc may fly at closer to FL310/330 etc but it's quite normal for A32Xs/73Gs to fly higher.

User currently onlineTripleDelta From Croatia, joined Jul 2004, 1115 posts, RR: 7
Reply 2, posted (8 years 9 months 3 weeks 5 days 11 hours ago) and read 8797 times:
AIRLINERS.NET CREW
PHOTO SCREENER

Even during warm weather, when aircraft performance is generally reduced due to the lower air density, some airliners fly high, even on relatively short hops. ZAG - CDG is about 1h 50 mins and the OU A319 I was going with to CDG for the Paris Air Show topped out at FL380. Coming back to ZAG, a completely full A320 got up to FL390.


No plane, no gain.
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 25
Reply 3, posted (8 years 9 months 3 weeks 5 days 11 hours ago) and read 8788 times:

Nothing to do with the age of the aircraft. I once flew in an ancient B720 at FL390. Fokker 100s and DC-9s are capable of operating at FL390 too. Most twin jets will have the excess thrust to climb to high levels quickly, while four engined "heavies" on long flights are initially weight limited, so might start cruising at FL310, then step climb to FL350 or higher as the fuel burns off.


The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 4, posted (8 years 9 months 3 weeks 5 days 11 hours ago) and read 8780 times:

Quoting Jetlagged (Reply 3):
and DC-9s are capable of operating at FL390 too.

The "ten series" was only certificated up to 350.

It is not just a performance issue. It is pressure differential, and time required to get back down below a certain altitude in the event of loss of cabin pressure.

Where performance is a factor is well illustrated by the B-727-200. The 200s with dash-seven engines don't have the oomph to push you up very high. Those with dash fifteen or dash seventeen engines will happily drive you right on up to where the wings won't support it anymore. The flight speed envelope gets quite narrow up at very high altitudes for many older planes. Even the 737-700 has enough thrust to get you up where the high speed and low speed limits are only a few knots apart.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 5, posted (8 years 9 months 3 weeks 5 days 9 hours ago) and read 8727 times:

Quoting SlamClick (Reply 4):
The flight speed envelope gets quite narrow up at very high altitudes for many older planes. Even the 737-700 has enough thrust to get you up where the high speed and low speed limits are only a few knots apart.

The well known "coffin corner". For the TR-2 (formerly known as U-2) it's only 10 knots from overspeed to stall speed, and the plane has no autothrottle. Whoooo...



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 25
Reply 6, posted (8 years 9 months 3 weeks 5 days 7 hours ago) and read 8699 times:

Quoting SlamClick (Reply 4):
The flight speed envelope gets quite narrow up at very high altitudes for many older planes.

Not just an older aircraft "feature". Supercritical wings can be just as badly affected.

Quoting Starlionblue (Reply 5):
The well known "coffin corner". For the TR-2 (formerly known as U-2) it's only 10 knots from overspeed to stall speed, and the plane has no autothrottle. Whoooo...

I think you mean the TR-1. As I understand it, "coffin corner" is where the mach buffet and stall buffet speeds coincide. At that point you have nowhere to go. In contrast, the 0.3g buffet limits of an airliner are the manoeuvring limits. Exceeding them does not mean you will fall out of the sky, unless you are turning significantly at the time. 0.3g equates to about a 40 degree banked turn.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 7, posted (8 years 9 months 3 weeks 5 days 5 hours ago) and read 8647 times:

Quoting Jetlagged (Reply 6):
Not just an older aircraft "feature". Supercritical wings can be just as badly affected.

Absolutely correct. I sort of alluded to that with:

Quoting SlamClick (Reply 4):
Even the 737-700 has enough thrust to get you up where the high speed and low speed limits are only a few knots apart.

. . . but I must confess I don't know what the differences are between 737NG wings and those of the classics, apart from the greater span and area.

Quoting Jetlagged (Reply 6):
In contrast, the 0.3g buffet limits of an airliner are the manoeuvring limits.

Can I assume you mean 1.3G for maneuvering? Actually it was also quite common to flight plan at 1.5 or 1.6G when turbulence is forecast at cruise altitude.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 8, posted (8 years 9 months 3 weeks 5 days 5 hours ago) and read 8638 times:

Quoting Starlionblue (Reply 5):
For the TR-2 (formerly known as U-2) it's only 10 knots from overspeed to stall speed, and the plane has no autothrottle. Whoooo...

One of my former students was a U-2 Instructor Pilot. I guess what you said is very true, but he said that most people who do not pass the checkout fail it on visual approaches. Apparently they use a shallow approach with the engine almost unspooled and it is rather demanding.

Here's one I used to share with my students, dispatchers and pilots alike.
From a performance manual for B-737-300 with CFM-56-3-B1 engines:
With 1.5G buffet boudary protection.
Flight Level 330
120,000 lbs cruise gross weight
The low speed limit is 254 Knots and the high speed limit is 260 Knots.

That is a four-knot window! Wouldn't take much in the way of a shear to depart that envelope, one way or the other.

If you level off at the same weight at FL310 the envelope expands to 240/283. I consider that a real good option. If you stay at 310 until you burn off another five thousand pounds of fuel then climb to 330 you now have 240/268. For those of us who are ham-fisted pilots that seems like a good deal.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineMrocktor From United States of America, joined Jan 2005, 1668 posts, RR: 50
Reply 9, posted (8 years 9 months 3 weeks 5 days 4 hours ago) and read 8595 times:

To answer the otehr part of the question, the maximum practical altitude for commercial aircraft is 41,000ft.

Two issues drive that limitation: the time of useful consciousness at that altitude is less than 15 seconds. This means the pilots have 15 seconds to recover from surprise, identify decompression and put on their masks. Flying higher would further reduce this margin to the point of unfeasibility.

The second issue is that almost all conventional aircraft have engines whose plane of rotation intercepts the pressurized section of the fuselage. This means that an uncontained rotor failure can puncture the pressure vessel. The accepted model for a large rotor fragment is one third of the disk (a 120 degree pizza slice).

The FAR Part 25 requirement for pressurization states that cabin altitude may not exceed 40,000 feet (exceeding must be considered catastrophic). You can imagine how fast decompression occurs with a hole that size. If you are flying above 41,000 feet, you cant get below FL400 before pressure equalizes.

These factors mean that certifying a commercial jet for flight above 41,000 feet is not practical. Business jets get around this problem by placing the engines aft of the pressure bulkhead. Since rotor failure cannot rip open the fuselage, the largest hole they have to contend with is some antenna breaking off. This means that depressurization will be a lot slower allowing time for descent below FL400. Some of these jets do use overpressure (open air conditioning inflow to the maximum and close outflow) to further reduce the depressurization rate.

mrocktor


User currently offlineWhiskeyflyer From Ireland, joined May 2002, 224 posts, RR: 0
Reply 10, posted (8 years 9 months 3 weeks 4 days 10 hours ago) and read 8424 times:

some older jets are restricted to lower altitudes due to (1) fatigue limits. We have a complete set of structural inspections to carry out because we fly above FL300, primarily lap joints requiring NDT. (2) RVSM its not worth the money or hassle getting RVSM approval so now we flying low in the FL200s, burning more fuel.
Mrocktor........ some nice comments you made. I learnt something new today and I thought the rear engines where there so the crew could sleep in a nice quiet cockpit


User currently offlineBhill From United States of America, joined Sep 2001, 948 posts, RR: 0
Reply 11, posted (8 years 9 months 3 weeks 4 days 9 hours ago) and read 8398 times:

Slamclick, sir, by "shear" do you mean where the two boundries of the jet streams meet and a wind velocity differential exsists?

Regards



Carpe Pices
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 12, posted (8 years 9 months 3 weeks 4 days 8 hours ago) and read 8378 times:

Quoting Bhill (Reply 11):
do you mean where the two boundries of the jet streams meet and a wind velocity differential exsists?

Well yes, and more. I was referring to any of the conditions that can cause an abrupt change in the wind direction and speed, horizontally and especially vertically.

This would include, for example, the polar side of the jetstream core as well as mountain wave. Then sometimes there are just atmospheric anomalies like the "Lakeview bump" a small area of light turbulence that many of us have experienced in the mid-thirties in the vicinity of the LKV VOR. It is probably a remnant of the wave from the Cascade mountain range but it seems to exist even on days with relatively light winds aloft.

I have experienced a severe loss of airspeed downwind of the Cascades. I don't know how bad it would have become or how long it would have lasted but we got "any altitude between 280 and 350" from ATC, punched off the autopilot and started a descent - chasing airspeed. In a few seconds we flew out of whatever it was and were able to climb back to 350 and resume normal cruise.

It is likely that passengers never noticed anything but a bump or two, but I would not have wanted to be in the coffin corner when he hit that.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineBri2k1 From United States of America, joined Dec 2004, 988 posts, RR: 4
Reply 13, posted (8 years 9 months 3 weeks 4 days 8 hours ago) and read 8375 times:

I believe shear refers to any boundary between differently moving air masses, horizontal or vertical. The jet stream could certainly produce a shear plane. Even a light breeze aloft could generate the 2-3 knot differential needed to stall or overspeed that plane at that altitude though.

What happens then? I know an overspeed can result in structural damage and even engine failure depending on design. What about going too slowly? If I stall a plane and don't make an immediate, positive recovery, I'm going to lose altitude. So, if the U2 stalles at FL330 and loses some altitude, is it going to be in denser air, with a lower stall speed, effectively breaking its own stall?



Position and hold
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 14, posted (8 years 9 months 3 weeks 4 days 7 hours ago) and read 8369 times:

Quoting Bri2k1 (Reply 13):
So, if the U2 stalles at FL330

I believe that the U-2 had its more serious problems up at higher altitudes, perhaps around 70000 feet. At FL330 it should have an envelope much like any other plane. Guesses there, as I'm not remotely qualified to talk about the U-2.

Quoting Bri2k1 (Reply 13):
If I stall a plane and don't make an immediate, positive recovery, I'm going to lose altitude. So, if the U2 stalles at FL330 and loses some altitude, is it going to be in denser air, with a lower stall speed, effectively breaking its own stall?

Remember that even though you are going too slow to fly, at high altitude you still have a high mach number, a mach number possibly in the trans-sonic range (0.75 to 1.2 Mach) The dynamic airloads are still extremely high on the airplane's surfaces. The U-2 was a rather fragile airframe. So if you depart stable flight at some unimaginable altitude there is still enough airload to break the wings off it.

Second problem is that of compressor stalling. At that kind of altitude abrupt throttle movements might well cause uncontrollable compressor stalls and guess what - you are headed for lower altitude for a restart, no matter where you are in the geopolitical world.

The public was told during the Frank Powers affair that he'd had a flameout and had to descend to a lower altitude, where the missile got him. In his book he said that he was hit at his overflight altitude which was higher (around a hundred thousand, I gather) than the Air Force would even admit the plane could do.

As for finding denser air on your descent; again I'd guess that you would have to descend a very long time before the air thickened up enough to be of any real use to you. Remember you got there by using your engine (in the middle of its envelope) to push your wings up the middle of their envelope to an altitude where they could no longer support flight if anything upset them. Then something did upset them. Recoveries are much more difficult outside the envelope.



Happiness is not seeing another trite Ste. Maarten photo all week long.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 16991 posts, RR: 67
Reply 15, posted (8 years 9 months 3 weeks 4 days 7 hours ago) and read 8359 times:

Quoting Jetlagged (Reply 6):
Quoting Starlionblue (Reply 5):
The well known "coffin corner". For the TR-2 (formerly known as U-2) it's only 10 knots from overspeed to stall speed, and the plane has no autothrottle. Whoooo...

I think you mean the TR-1.

Mu apologies. It is indeed the TR-1.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineTimz From United States of America, joined Sep 1999, 6767 posts, RR: 7
Reply 16, posted (8 years 9 months 3 weeks 4 days 3 hours ago) and read 8322 times:

"These factors mean that certifying a commercial jet for flight above 41,000 feet is not practical."

But you're not saying none are certified above FL410?

I thought I once heard a 747SP at FL430-- think I'm remembering wrong?


User currently offlineIrish251 From Ireland, joined Nov 2004, 964 posts, RR: 4
Reply 17, posted (8 years 9 months 3 weeks 4 days 2 hours ago) and read 8311 times:

I heard an Air France 747-400 on a DUB-CDG ferry flight climbing to FL450 and reporting level! Also, when Aer Lingus had 767s, I once heard one en route LHR-DUB (about a 50 minute flight) at FL430 - both very unusual occurrences, I think, but presumably fully legal.

User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2543 posts, RR: 25
Reply 18, posted (8 years 9 months 3 weeks 4 days ago) and read 8298 times:

Quoting SlamClick (Reply 7):
Can I assume you mean 1.3G for maneuvering? Actually it was also quite common to flight plan at 1.5 or 1.6G when turbulence is forecast at cruise altitude.

Yes, the manuals I've seen and the data I've used refers to them as 0.3g buffet margins, which equates to manoeuvring flight at 1.3g. Margins may vary from aircraft to aircraft, on the 737-3/4/500 the buffet margin displayed on EFIS and annunciated on the FMC is 0.3g.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineBhill From United States of America, joined Sep 2001, 948 posts, RR: 0
Reply 19, posted (8 years 9 months 3 weeks 3 days 23 hours ago) and read 8280 times:

SlamClick, sir, I believe I know what you might be referring to. SEA is my "homeport" and I remember on initial descent on a NWA DC-10 a few years back experiancing a rather "uncomfortable" roll to the starboard and a single sudden drop of altitude, and my body being forced forward against my seatbelt. As I was sitting in a window seat, there was only the cirrus clouds around as you described earlier. I am still amazed at the suddenness and abruptness that caused that large aircraft to change flight like that. As if a "giant" hand was pushing against and down on the aircraft..mayhaps 2-3 seconds tops.

Regards



Carpe Pices
User currently offlineKhenleyDIA From Sweden, joined Feb 2005, 425 posts, RR: 0
Reply 20, posted (8 years 9 months 3 weeks 3 days 11 hours ago) and read 8205 times:

Quoting Irish251 (Reply 17):
Also, when Aer Lingus had 767s, I once heard one en route LHR-DUB (about a 50 minute flight) at FL430 - both very unusual occurrences, I think, but presumably fully legal.

There is a picture on a.net of the cockpit of a 767 and the altimeter clearly indicates FL430. From what I have read and been told, they are certified to that level. I also seem to recall hearing that a few other commercial airliners were certified to fly at that level, but don't remember which.

Does anyone know some of the higher altitude certified commercial airliners?

Thanks.

KhenleyDIA



Why sit at home and do nothing when you can travel the world.
User currently offlineMrocktor From United States of America, joined Jan 2005, 1668 posts, RR: 50
Reply 21, posted (8 years 9 months 3 weeks 3 days 9 hours ago) and read 8173 times:

Quoting Whiskeyflyer (Reply 10):
I learnt something new today and I thought the rear engines where there so the crew could sleep in a nice quiet cockpit

The rear positioning of the engines has many resons, ground clearance being one of the foremost. Pressurization is one fo the many variables in the decision.

Quoting Bri2k1 (Reply 13):
So, if the U2 stalles at FL330 and loses some altitude, is it going to be in denser air, with a lower stall speed, effectively breaking its own stall?

As SlamClick posted, the hard part is maintaining post-stall control of the aircraft. If you manage to maintain a decent attitude avoiding structural failure, recovery should be possible (in aircraft that don't have deep stall characteristics, at least).

Quoting Timz (Reply 16):
But you're not saying none are certified above FL410?

I thought I once heard a 747SP at FL430-- think I'm remembering wrong?



Quoting Irish251 (Reply 17):
I heard an Air France 747-400 on a DUB-CDG ferry flight climbing to FL450 and reporting level! Also, when Aer Lingus had 767s, I once heard one en route LHR-DUB (about a 50 minute flight) at FL430 - both very unusual occurrences, I think, but presumably fully legal.

I'm sayiing that the certification rules today are like that. At the time the 747 and 767 were certified, the rules may very well have been different. The advisory circular referent to uncontained rotor failures was published in 1989, for instance.

mrocktor


User currently offlineCitationJet From United States of America, joined Mar 2003, 2420 posts, RR: 3
Reply 22, posted (8 years 9 months 3 weeks 22 hours ago) and read 7952 times:

The 707 max altitude is 42,000 ft.
The 720 max altitude is 42,000 ft.
The 727 max altitude is 42,000 ft.
The 737-100, -200 max altitude is 35,000 or 37,000 ft.
The 737-300, -400, -500 max altitude is 37,000 ft.
The 737-600, -700, -800, -900 max altitude is 41,000 ft.
The 747 max altitude is 45,100 ft.
The 757 max altitude is 42,000 ft.
The 767 max altitude is 43,100 ft.
The 777 max altitude is 43,100 ft.

The DC-10 max operating altitude is 42,000 ft.
The MD-11 max operating altitude is 43,200 ft.
The L-1011-385-1 max operating altitude is 42,000 ft.
The L-1011-385-3 max operating altitude is 43,000 ft.

Some business jets are certified to higher altitudes.
The Cessna Citation X (Model 750) is certified to 51,000 ft.

Here is a link to the FAA Type Certificate Data Sheet web site that has all the certification information.
http://www.airweb.faa.gov/Regulatory...keModel.nsf/MainFrame?OpenFrameSet

.

[Edited 2005-10-05 04:50:28]


Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
User currently offlineAviation From Australia, joined Dec 2004, 1143 posts, RR: 21
Reply 23, posted (8 years 9 months 3 weeks 20 hours ago) and read 7928 times:

Id say 39,000ft is high but still in the normal range i have been on many flights were we cruise at 38,000ft never been to 39,000ft but id say its fine a 737 can fly to 44,000ft can it not is this its service ceiling?

Thanks,
Aaron J Nicoli



Signed, Aaron Nicoli - Trans World Airlines Collector
User currently offlineMrocktor From United States of America, joined Jan 2005, 1668 posts, RR: 50
Reply 24, posted (8 years 9 months 3 weeks 5 hours ago) and read 7851 times:

Quoting CitationJet (Reply 22):
The 737-600, -700, -800, -900 max altitude is 41,000 ft



Quoting CitationJet (Reply 22):
The 777 max altitude is 43,100 ft

Great information CitationJet! The 777 is a fairly recent aircraft, but it's certification basis probably precedes 1989. I wonder what the limits are for the more recent Airbuses, they could shed some light on how the rules stand nowdays.

mrocktor


25 Post contains images Tornado82 : From the meteorological standpoints of this... Yes, in a simplified term. Yes, definitely. Well, it depends which altitude you're talking about. At th
26 Bri2k1 : Very informative thread. Thanks everyone for the good info.
27 Allessandro : There is one thing I miss in all your information... and that is the maximum differential pressure the aircraft can handle... the cabin altitude is mo
28 Bri2k1 : I seem to recall flying out of ONT on UA listening to channel 9. We were on LA Center and had just switched to a higher-altitude sector frequency. For
29 Luke : As far as I know, the FMC on most modern aircraft have the function of determining when the aircraft is light enough to step up to a higher flight lev
30 Starlionblue : Yepp. On final another U-2/TR-1 pilot will drive along the runway next to the plane to help guide the pilot in. Considering the low approach speed wi
31 Post contains images TripleDelta : Don't they usually drive behind the U-2/TR-1? I have a picture or two of that in a book on "black jets" and it looks pretty intense. Something for th
32 CFCUQ : I read once that early in the U-2 program, they used SS 396 El Caminos (68-9) and placed the outrigger landing gear on the wing ends from the Camino w
33 SNBru : Thanks for all the information.
34 Bond007 : Sorry, got on this thread late. Looking at some US flight plan data I have the following info: Many Learjet 45's, Global Express, and Gulfstream 5's c
Top Of Page
Forum Index

Reply To This Topic Altitude Of 39000 Ft
Username:
No username? Sign up now!
Password: 


Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
  • DETAILED RULES
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)


Similar topics:More similar topics...
Altitude Of Landing Aircraft posted Mon May 9 2005 12:12:33 by Mrniji
Initical Cruise Altitude Of A380? posted Mon Feb 4 2002 16:39:57 by Donder10
Line Of Sight With Regard To Altitude posted Fri Dec 9 2005 21:06:53 by THVGJP
Altitude Impact On A Bottle Of Coke posted Mon Jan 3 2005 10:06:14 by 707cmf
Effect Of Altitude /temperature On Aircraft Range posted Thu Feb 12 2004 10:42:01 by Thestooges
Effect Of Altitude On V Speeds? posted Tue Apr 22 2003 20:57:09 by Kaitak
What Is The Edge Of Space (Altitude In Feet) posted Mon Sep 30 2002 19:27:43 by Wardialer
High Altitude A Part Of Flight Training In The US? posted Sat Oct 13 2001 21:58:40 by USAFHummer
Cruising Altitude From Airline Of Aircraft? posted Wed Sep 5 2001 15:33:29 by B777-200ER
Other Uses Of Airplane Engines? posted Sat Nov 18 2006 10:01:00 by DIJKKIJK

Sponsor Message:
Printer friendly format