Increasing power required with altitude.. what's a good plain english explanation?

On Feb 2, 7:42 pm, "xerj" wrote:
What is interesting is that this author comes up with the right
answer, but he uses some false asumptions.Its obvious he hasnt spent
much time in a real airplane

What's false about the assumptions? He's talking about flight at the same
angle of attack at different altitudes.

Are you serous?
First, take a look at his opening statement.We dont fly planes like
this in real life.It seems he has made the deductions first, and then
came up with the opening statement.Also, not all of these deductions
can be true at the same time.

alice writes:

Duh.No one is arguing that a jet uses less fuel up high.It is the
reason why that is in question.You are making a HUGE misconception
about the reason why.

Less fuel = less power.

By your reasoning, A jet would never have a service ceiling!

Jets have a service ceiling for several reasons. For one, eventually
the air is too thin to provide any lift, no matter how fast you are
moving. For another, eventually the air is too thin to support
internal combustion engines.

Explain to us what a "sweet spot" is.

Greatest distance covered per unit of fuel consumed, lowest wear and
tear on the aircraft (especially engines).

Why is it that you feel the airlines dont take into account TIME
when doing the preflight planing.

They do, but fuel costs more than time. That's why flights are longer
now than they used to be: airlines plan for fuel economy, not speed.

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On Feb 2, 4:24 pm, "xerj" wrote:
If you
can maintain constant power (turbo charging), you get better and
better performance with altitude.

The TAS will increase, but say you want to hold a specific angle of attack
and its attendant IAS (maybe for range), you will need more power to do that
as you get higher.

That is correct, but that was not your original question.

On Feb 3, 9:42 am, Mxsmanic wrote:
Less fuel = less power.

MX, I am laughing now.I cant figure out if you are really that
ignorant or if you are just messing with me.The real reson jets fly
high is for speed.The higher they go, the faster they can go.Why do
you think jets measure cruise speed in Mach?What do you think happens
to Mach as a jet flys higher?Now explain how you can move a jet (Or
anything else for that mater, like a car) FASTER on LESS thrust?For
the 3rd time here MX, you have made a misconception and you are
thinking backwards.


Jets have a service ceiling for several reasons. For one, eventually
the air is too thin to provide any lift, no matter how fast you are
moving. For another, eventually the air is too thin to support
internal combustion engines.

MX, I am laughing even harder now!Can you explain the real reason
behind a jets service ceiling and what it is a function of?

Explain to us what a "sweet spot" is.

Greatest distance covered per unit of fuel consumed, lowest wear and
tear on the aircraft (especially engines).

??? I gotta ask you MX, what airline do you work for?Are you saying
they use LCR or CCR charts to determine power settings?I hate to argue
with you but when I was in initial training at my fist jet job, it was
explained (very compellingly) why we dont base cruise flight on
this.If you are doing something different, Id like to know the
reasoning behind it.

Why is it that you feel the airlines dont take into account TIME
when doing the preflight planing.

They do, but fuel costs more than time. That's why flights are longer
now than they used to be: airlines plan for fuel economy, not speed.

OK, Ill bite MX.Why are you claiming that speed is not a function of
economy.Has it not occured to you that the LONGER a plane is in the
air, the more wear and tear it is incuring?Also, the longer a plane is
in the air, the more fuel it is burning.Which of course means the more
fuel it has to carry.Which means it is heavier.Which requires more
thrust.Tell me how this saves fuel again?

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alice writes:

The real reson jets fly high is for speed.

The real reason they fly high is for fuel economy.

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alice wrote:
For
the 3rd time here MX, you have made a misconception and you are
thinking backwards.

The third time? You must be new around here.

On Feb 3, 11:13 am, Mxsmanic wrote:
alice writes:


The real reason they fly high is for fuel economy.

OK MX, You are just toying with me.And, you got the last laugh.I am
kinda curious who you fly for and what they taught you in regards to
long range cruise.The only way your statements would work out might be
in a lightly loaded biz jet or something.Clue us in here.
KM

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On Feb 3, 11:27 am, Newps wrote:
alice wrote:

For

the 3rd time here MX, you have made a misconception and you are
thinking backwards.

The third time? You must be new around here.

Yes I am new. I stumbled across this list by accident.Just got
suckered in by someone who likes to argue I guess.

On Feb 3, 10:36 am, "alice" wrote:
On Feb 2, 7:42 pm, "xerj" wrote:

What is interesting is that this author comes up with the right
answer, but he uses some false asumptions.Its obvious he hasnt spent
much time in a real airplane

What's false about the assumptions? He's talking about flight at the same
angle of attack at different altitudes.

Are you serous?
First, take a look at his opening statement.We dont fly planes like
this in real life.It seems he has made the deductions first, and then
came up with the opening statement.Also, not all of these deductions
can be true at the same time.


John Denker is a highly respected author and his book provides some of
the clearest explanation of the aerodynamics without resorting to
complex mathematics. This particular section is not about how
airplanes are flown in every day life, but an indepth exploration of
the factors that influence power, density, drag and AOA. Just because
you operate a jet does not make you an expert in aerodynamics.
Engineers and scientists build airplanes, and pilots operate them.
"Practice is not a substitute for understanding, nor vice versa" ,
which is eloquently stated in the Introduction section of his book.
If you are able to provide a better explanation, please do so, but it
seems to me that it is you who needs to spend some time reading up on
the basics.

For the 3rd time here MX, you have made a misconception
and you are thinking backwards.

The third time? You must be new around here.

Yes I am new. I stumbled across this list by accident.Just got
suckered in by someone who likes to argue I guess.

MX is the resident Troll on two groups that I read, and
reportedly an unknown number of others.

There was an interesting discussion about the matter a month
or two ago, and there is an excellent article in Wikipedia at
http://en.wikipedia.org/wiki/Internet_troll

In any case, please don't feed him any more than necessary.

Peter
(It's devilishly difficult!)