26point2
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What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 5:51 pm

I've always wondered why the media and general public often refers to "30,000 feet" as a commercial airliner cruise altitude. Seems it's the standard phrase so much that it's become a cliche. "Terror at 30,000 feet", "Hi-jinks at 30,000 feet", etc.

I believe most airliners would fly much higher than this at cruise and more importantly, before the advent of RVSM wasn't FL300 an unusable altitude?

Was 30,000 EVER the "go-to" altitude?
 
futureualpilot
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 6:26 pm

Probably the same reason any surface not a runway at an airport is the "tarmac" but even then you can be sitting at the gate and hear someone say they're sitting on the "runway" or why we still have "stewardesses" or how so many people assume I make 6 figures a year with 3/4 of the month off, or fly a certain route all the time, or anything not 747 is "small" or people frown at boarding a Dash-8-Q400 that has maybe 100hrs on the airframe and comment on how old the airplane must be, after flying a 40 year old DC-9 or 25yr old 757 to the hub airport. I've had people comment on how I messed up the landing because one side touched down before the other in a crosswind gusting to 40.

People just don't know. It isn't necessarily bad, most of the general public knows as much about the inner workings and details of aviation and airlines as I do about being a doctor or working in an ER.
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citationjet
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 7:26 pm

I believe it is because it is a nice round number. It is easier and shorter to say and remember "Thirty thousand feet", rather than "Thirty seven thousand feet". Most people recall that airlines fly at altitudes that start with Thirty thousand. Whether it is 37,000, 32,000 or 39,000 doesn't really matter to them.

There was a 1954 movie 20,000 Leagues Under the Sea, which referred to the distance traveled beneath the ocean. They could have called it 22,500 Leagues, but it wouldn't have been as easily remembered.
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KELPkid
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 7:38 pm

Probably because, before the advent of pure jet airliners, it was a pretty darned hard altitude to get to (and maintain!). Not that there weren't radial powered piston aircraft that could do it. But it wasn't a comfortable place to be in a piston-powered aircraft, as engine power drops up precipitously up there (even with a supercharger), and engine cooling goes way down. Not to mention that the piston-era cabin heating systems really struggle at that high of an altitude. And you took forever to climb that high.

Some turboprops still struggle to get that high. It is a number that stuck with the minds of the media and the non-flying public. Remember, in the 1950's, the name of the game was "faster, higher, farther..."  
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Fabo
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 9:45 pm

Quoting CitationJet (Reply 2):
There was a 1954 movie 20,000 Leagues Under the Sea, which referred to the distance traveled beneath the ocean. They could have called it 22,500 Leagues, but it wouldn't have been as easily remembered.

There used to be a book by that name long before. But your point stands.

Quoting KELPkid (Reply 3):
Some turboprops still struggle to get that high.

Which do even try? I was not aware of any civilian turboprops flying that high, save for T114...
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bikerthai
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 10:23 pm

Had a hunch . . .

Looked up the temperature profile vs altitude and found that there is a temperature inversion near the 10Km mark (near 32000ft).

http://www.aerospaceweb.org/question/atmosphere/q0112.shtml

Atmospheric 101.

Could this be the hard ceiling they are referring to?

Beyond that you go into the "STATOSPHERE . . . ERE . . . ERE . . .ERE" - Echo effect here for emphasis . . .:D

bikerthai

[Edited 2011-10-24 15:25:23]
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mandala499
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 10:41 pm

And someone once told me...
"Flying goes up to 30,000ft, after that, it's a job" and "Adventure goes up to 30,000ft, after that, it's just a ride to get somewhere"

   (although I'm sure he meant 25,000ft but 30,000ft sounds better)
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spacecadet
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 11:42 pm

I'm sure it's just a nice round number. And it doesn't make a bad "average" even today. Remember, not every flight is a trans-pacific flight on an A380. Many, many of the world's flights are short hops using CRJ's or even turbo-props. The last time I flew from SFO-RDM, we cruised at 24,000 feet.

The last 777 flight I flew to Japan, we started our cruise at 29,000 feet, then stepped to 32,000 feet and ended up at 35,000 feet. So it's not like it's even that far off for large airliners.
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N243NW
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 24, 2011 11:55 pm

Quoting spacecadet (Reply 7):
The last time I flew from SFO-RDM, we cruised at 24,000 feet.

I got you beat. A typical route for me is MKE-ORD, which typically sees 7,000 feet.

Quoting 26point2 (Thread starter):
I've always wondered why the media and general public often refers to "30,000 feet" as a commercial airliner cruise altitude.

It seems that I hear 35,000 as much, if not more, than 30,000 nowadays.

On an unrelated note, I wonder how many pilots realize that they're actually lying to passengers during their PA announcements. Unless the pressure is exactly 29.92 at sea level, we're not cruising at 34,000 feet. We're cruising at FL 340. 
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rfields5421
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 12:25 am

As an old fart - I remember airline ads which focused on all jet service for certain routes - emphasizing that the route was flown at "30,000 feet"

As mentioned above about easy to remember round numbers - 30,000 feet was a great advertising hook back when jets were first introduced.

Once something gets 'standardized' in the news media - nothing can change that - no logic, nor the truth.

Someday maybe it will be 40,000 feet, but only after a new generation of yet unborn editors and writers becomes the majority in the new media.

I've seen the Concorde referred to as cruising across the Atlantic at 30,000 feet in a magazine article.
 
my235
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 1:45 am

Quoting Fabo (Reply 4):
Which do even try? I was not aware of any civilian turboprops flying that high

Avanti Piaggio: 41,000ft surface ceiling,
Beechcraft Starship: Same,
MU-2: 29,600ft (SC),
Piper PA-31T Cheyenne: 29,000ft (SC),
King Air B200: 35,000ft (SC),
Merlin IVC: 31,000ft (SC),
Conquest II: 35,000ft (SC)

[Edited 2011-10-24 18:48:59]
 
wn700driver
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 2:11 am

Quoting spacecadet (Reply 7):

I'm sure it's just a nice round number. And it doesn't make a bad "average" even today. Remember, not every flight is a trans-pacific flight on an A380. Many, many of the world's flights are short hops using CRJ's or even turbo-props. The last time I flew from SFO-RDM, we cruised at 24,000 feet.

Yup. EN's (DBA US Airways Exp) PHL - SBY run rarely gets above 5000 agl. Saves a pressure cycle too.
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ThirtyEcho
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 5:11 am

30,000 feet is where an airplane is prone to hit an "air pocket" and do a "loop the loop" straight into the "tarmac."

!930s airplane movies still dominate MSM aviation reporting.
 
Fabo
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 11:11 am

Quoting my235 (Reply 10):

Thank you.
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Dufo
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 9:45 pm

Quoting my235 (Reply 10):
Avanti Piaggio: 41,000ft surface ceiling,
Beechcraft Starship: Same,
MU-2: 29,600ft (SC),
Piper PA-31T Cheyenne: 29,000ft (SC),
King Air B200: 35,000ft (SC),
Merlin IVC: 31,000ft (SC),
Conquest II: 35,000ft (SC)

Embraer 120: 32,000ft
Saab 340: 31,000ft

Probably only during certification flights 
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aklrno
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 9:59 pm

It's a very important number to me. I have to watch my weight so I try to eat only healthy foods and in limited amounts. I do have a few exceptions, and one is the "30,000 foot rule". Basically, anything eaten over 30,000 feet is not limited. The rational is (choose one or more):
1. It's a miracle if any food presented to me above 30,000 feet is any good.
2. If there is food at all over 30,000 feet that is another miracle.
3. I am flying F or J and that meal is costing me a fortune.
4. When traveling it may be a long time before you see anything edible again.


If I'm just flying OAK-RNO and we never get over 23,000 I don't even have the peanuts.

So far it has worked out OK.
 
B777LRF
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 10:26 pm

Quoting bikerthai (Reply 5):
Looked up the temperature profile vs altitude and found that there is a temperature inversion near the 10Km mark (near 32000ft).

What you are referring to is the tropopause, the actual height of which varies. The main variable is where you are on the globe; the tropopause is highest over equator and decreases towards the poles. This is, incidentially, the reason for Concorde flying higher (over 60K) when on her sojourns to the Southern Ocean, than on her usual trans Atlantic journeys where she schlepped about in the 50s.

As to the original question, it's just plain old media laziness and affinity for smart sound bites.

[Edited 2011-10-25 15:29:30]
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KELPkid
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RE: What's The Big Thing With "30,000 Feet"?

Tue Oct 25, 2011 11:27 pm

Quoting Dufo (Reply 14):
Embraer 120: 32,000ft
Saab 340: 31,000ft

Probably only during certification flights

Some T-Props (like the Dash 8) don't even have passenger oxygen masks. They just use the beta range on the props during emergency descent to make it down to 10,000' in the allotted time 
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Bellerophon
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RE: What's The Big Thing With "30,000 Feet"?

Wed Oct 26, 2011 12:48 pm

bikerthai

...Looked up the temperature profile vs altitude and found that there is a temperature inversion near the 10Km mark (near 32000ft)...

There is no temperature inversion near the 10km mark, under ISA conditions,

Under ISA conditions, temperature is assumed to decrease linearly from +15°C at sea level to -56.5°C at around 11,000m/36,100ft, the height at which the tropopause is deemed to start.

In the tropopause (around 11,000m/36,100ft to 20,000m/66,000ft) temperature remains constant at -56.5°C.

I suspect you've misread the temperature v altitude graph on the site you quote, where they have (rather unhelpfully) omitted to identify the tropopause region. It isn't very clear, but if you look closely at their graph you will see a small vertical portion of the temperature line, just above 10,000m on their graph, which represents the tropopause region.

Only above 20,000m / 66,000ft, under ISA conditions, does the temperature start to rise (slowly) again.

ISA is, of course, a theoretical model, and what happens on the day can vary significantly from theory, particularly the height of the tropopause, which is lower over the Poles and higher over the equator.

In my experience, whilst the temperature in the tropopause can and does vary significantly from ISA, an inversion in that region is rare.

Best Regards

Bellerophon

[Edited 2011-10-26 05:49:58]
 
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bikerthai
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RE: What's The Big Thing With "30,000 Feet"?

Thu Oct 27, 2011 4:25 am

Quoting Bellerophon (Reply 18):

Thanks, probably should have read the tables instead.

bikerthai
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57AZ
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RE: What's The Big Thing With "30,000 Feet"?

Sat Oct 29, 2011 4:52 pm

Some high performance piston twins such as Cessna's 414 and 421 have a service ceiling of 30,000 feet.
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bueb0g
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RE: What's The Big Thing With "30,000 Feet"?

Sat Oct 29, 2011 10:46 pm

Quoting N243NW (Reply 8):
I wonder how many pilots realize that they're actually lying to passengers during their PA announcements. Unless the pressure is exactly 29.92 at sea level, we're not cruising at 34,000 feet. We're cruising at FL 340. 

All pilots realise they're lying, you think pilots get to where they are without knowing the difference between height, altitude and flight levels? We do that at PPL level  
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FlyboyOz
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RE: What's The Big Thing With "30,000 Feet"?

Sun Oct 30, 2011 10:28 am

30 000 feet is somewhat close to 10km...
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KELPkid
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RE: What's The Big Thing With "30,000 Feet"?

Sun Oct 30, 2011 9:39 pm

Quoting 57AZ (Reply 20):

Some high performance piston twins such as Cessna's 414 and 421 have a service ceiling of 30,000 feet.

Would you really want to be up there, though, with passengers? How quick can you climb up there? If you're not a professional pilot, are you clear in what should happen if there's a problem up that high? Nothing personal, just pointing out that just because you can doesn't mean you should in aviation  
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sccutler
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 31, 2011 4:09 pm

Quoting KELPkid (Reply 23):

Some high performance piston twins such as Cessna's 414 and 421 have a service ceiling of 30,000 feet.

Would you really want to be up there, though, with passengers? How quick can you climb up there? If you're not a professional pilot, are you clear in what should happen if there's a problem up that high? Nothing personal, just pointing out that just because you can doesn't mean you should in aviation

Agreed - engine cooling at that altitude is terrible.

How would you like to fly in the T210F, which had a service ceiling of (if I recall correctly) 31,300' - that sounds like my idea of No Fun.
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Rara
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 31, 2011 5:38 pm

It's "ten-thousand meters" here.   Just a nice round number.
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KELPkid
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 31, 2011 7:51 pm

Quoting sccutler (Reply 24):

Agreed - engine cooling at that altitude is terrible.

How would you like to fly in the T210F, which had a service ceiling of (if I recall correctly) 31,300' - that sounds like my idea of No Fun.

And how's ATC going to like little piston-powered GA planes buzzing around in the flight levels?    If you join an airway, lots of traffic is going to have to be vectored around you. And you will be sucking oxygen through a mask in the T210 for sure...maybe even the 421 and 414 (don't know how well the pressurization systems in those birds can cope with 30,000 feet). And the lack of cooling air through the fins of the engine...

Sucking O2 sucks   (been there, done that...) Doubly so when the cabin heat is inadequate.
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tcasalert
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RE: What's The Big Thing With "30,000 Feet"?

Mon Oct 31, 2011 9:21 pm

Quoting KELPkid (Reply 26):
And how's ATC going to like little piston-powered GA planes buzzing around in the flight levels?    If you join an airway, lots of traffic is going to have to be vectored around you. And you will be sucking oxygen through a mask in the T210 for sure...maybe even the 421 and 414 (don't know how well the pressurization systems in those birds can cope with 30,000 feet). And the lack of cooling air through the fins of the engine...

Had a Piper Cheyenne fly over here on airways the other day at FL270.....

Must have been fun to be so high up in such a little aircraft!
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KELPkid
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RE: What's The Big Thing With "30,000 Feet"?

Tue Nov 01, 2011 6:55 pm

Quoting TCASAlert (Reply 27):
Had a Piper Cheyenne fly over here on airways the other day at FL270.....

Must have been fun to be so high up in such a little aircraft!

Well, the Cheyenne is a turboprop...much better than a Navajo (the piston equivalent) at that altitude  
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