Re: Flight Levels and Speed

From:         drholik@ameritech.net
Date:         13 Jul 1999 08:29:34 -0400
Organization: Ameritech.Net www.ameritech.net  Complaints: abuse@ameritech.net
References:   1
Next article
View raw article
  or MIME structure


--------------B973BA6E9822A2547F1E9FCD
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

The "speedometer" for lack of a better term, shows what's called "Indicated Air
Speed" (IAS) in knots.  When you ascend the atmosphere gets less dense, the
higher you go the more space between air molecules, so the Indicated air speed
reads lower even though you're not slowing down.  What you really want to look
at is your Mach speed indicator, it will provide a true reading.  Most aircraft
cruise between Mach .80-.90.  Also, remember that your airspeed and your
groundspeed are always going to be different.  If you fly west, you're flying
against the prevailing winds so your airspeed reads higher and your groundspeed
gets lower.  If you fly East, you're flying with the winds so your airspeed will
be lower than your groundspeed.  Example... flying from Indianapolis to Oakland
takes 4:00 hours flying from Oakland to Indianapolis takes only 3:30 hours,
because of the winds.  Usually, if your flying at say Mach .84 going west, your
groundspeed will be about 500 knots  if you fly at Mach .84 going east, your
ground speed would be usually about 580+ knots( i've seen almost 700 knots
before with a good tailwind) It all depends on the winds. So don't be fooled you
really are going faster than 300 knots.  ( i wondered this once upon a time
also)

ME Incorporated wrote:

> I'm sorry to post a question about a computer aircraft simulator in these
> newsgroups, but it does have something to do with Real Life (tm), and I have
> to know!
>
> I was flying in Microsoft Flight Simulator 98, which is supposed to be
> pretty realistic when it comes to the flight models of the 737-300.
>
> I noticed that the higher you go, the lower the Maximum Mach needle was.
> This needle shows the fastest your aircraft is designed to go in terms of
> Mach (speed of sound), and moves according to air density (I guess.)  If
> your indicated airspeed is near or exceeds this marker needle, you may be in
> trouble.  In real life this is bad.  In a simulator, well, reset!
>
>  At 19000 feet, you can go almost 400kts (or faster?), but at 33000, you
> can't quite get to 300Kts without having the "overspeed" warning show up.
> Is this realistic?  It makes sense, given that the density of the air is
> less, and I think I remember that the speed of sound is slower due to the
> lower air density, so therefore, the maximum mach would be at a slower Kts
> reading.
>
> I am not a physics major, but wouldn't it be faster to fly at the lower
> altitude in real life?  I can't see any difference in fuel consumption in
> the simulator, but then again, it's a (to be honest) crude simulation.
>
> Wouldn't it make sense for the airliners to fly at the lower altitude, save
> the time, and turn around the aircraft faster?  This would allow the
> airlines to use less aircraft, less crews, and make more money with more
> paying passengers per aircraft per day.  (Provided, of course, fuel
> consumption stays constant at cruise.)
>
> Obviously, there might be a safety issue at the lower altitude, but that's
> for another discussion if my simple little theory is correct...
>
> Or is the simulator just screwed up?
>
> Just wondering... and thanks in advance!
>
> --
>
> "Flying is easy... buying the tickets, that's hard."
> -MikeyB

--------------B973BA6E9822A2547F1E9FCD
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: 7bit

<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
The "speedometer" for lack of a better term, shows what's called "<b>Indicated</b>
Air Speed" (IAS) in knots.&nbsp; When you ascend the atmosphere gets less
dense, the higher you go the more space between air molecules, so the Indicated
air speed reads lower even though you're not slowing down.&nbsp; What you
really want to look at is your Mach speed indicator, it will provide a
true reading.&nbsp; Most aircraft cruise between Mach .80-.90.&nbsp; Also,
remember that your airspeed and your groundspeed are always going to be
different.&nbsp; If you fly west, you're flying against the prevailing
winds so your airspeed reads higher and your groundspeed gets lower.&nbsp;
If you fly East, you're flying with the winds so your airspeed will be
lower than your groundspeed.&nbsp; Example... flying from Indianapolis
to Oakland takes 4:00 hours flying from Oakland to Indianapolis takes only
3:30 hours, because of the winds.&nbsp; Usually, if your flying at say
Mach .84 going west, your groundspeed will be about 500 knots&nbsp; if
you fly at Mach .84 going east, your ground speed would be usually about
580+ knots( i've seen almost 700 knots before with a good tailwind) It
all depends on the winds. So don't be fooled you really are going faster
than 300 knots.&nbsp; ( i wondered this once upon a time also)
<p>ME Incorporated wrote:
<blockquote TYPE=CITE>I'm sorry to post a question about a computer aircraft
simulator in these
<br>newsgroups, but it does have something to do with Real Life (tm), and
I have
<br>to know!
<p>I was flying in Microsoft Flight Simulator 98, which is supposed to
be
<br>pretty realistic when it comes to the flight models of the 737-300.
<p>I noticed that the higher you go, the lower the Maximum Mach needle
was.
<br>This needle shows the fastest your aircraft is designed to go in terms
of
<br>Mach (speed of sound), and moves according to air density (I guess.)&nbsp;
If
<br>your indicated airspeed is near or exceeds this marker needle, you
may be in
<br>trouble.&nbsp; In real life this is bad.&nbsp; In a simulator, well,
reset!
<p>&nbsp;At 19000 feet, you can go almost 400kts (or faster?), but at 33000,
you
<br>can't quite get to 300Kts without having the "overspeed" warning show
up.
<br>Is this realistic?&nbsp; It makes sense, given that the density of
the air is
<br>less, and I think I remember that the speed of sound is slower due
to the
<br>lower air density, so therefore, the maximum mach would be at a slower
Kts
<br>reading.
<p>I am not a physics major, but wouldn't it be faster to fly at the lower
<br>altitude in real life?&nbsp; I can't see any difference in fuel consumption
in
<br>the simulator, but then again, it's a (to be honest) crude simulation.
<p>Wouldn't it make sense for the airliners to fly at the lower altitude,
save
<br>the time, and turn around the aircraft faster?&nbsp; This would allow
the
<br>airlines to use less aircraft, less crews, and make more money with
more
<br>paying passengers per aircraft per day.&nbsp; (Provided, of course,
fuel
<br>consumption stays constant at cruise.)
<p>Obviously, there might be a safety issue at the lower altitude, but
that's
<br>for another discussion if my simple little theory is correct...
<p>Or is the simulator just screwed up?
<p>Just wondering... and thanks in advance!
<p>--
<p>"Flying is easy... buying the tickets, that's hard."
<br>-MikeyB</blockquote>
</html>

--------------B973BA6E9822A2547F1E9FCD--