12/5 How does an airplane know its true speed instead of air speed? Thanks.
\_ African or European? -John
\_ radar, possibly GPS
\_ oh yeah, you can get heading/speed via radar if you're
on IFR or on VRF flight following. -csua pilot
\_ http://www.csgnetwork.com/tasinfocalc.html
\_ That computes true air speed, not ground speed. -geordan
\_ what exactly is the difference between the two?
\_ If you're flying at an air speed of 300MPH eastward in some wind
whose speed is 50MPH westward, your true speed is only 250MPH.
\_ but i get screwed in physics question when they think
the instrument panel shows true speed. :(
\_ there is the true airspeed, indicated airspeed, and ground speed.
You get true airspeed by taking in account of indicated airspeed
and the environment (temperature, humidity, etc), and the know
calibrated errors from the airspeed indicator (indicated airspeed).
Then you get the approximate wind speed from ATIS, tower, or
other reliable source, recalibrate it (since wind speed is always
true north whereas your heading indicator is always magnetic
north). From those variables you can get a pretty precise ground
speed. However, GPS makes it a lot easier. -csua pilot who
quit being a programmer and is now flying turboprops in
the midwest
\- csua pilot: what are those sign like A45 R16 etc you
see by the side of runways at commercial airports.
i think they sometimes have arrows on them.
\_ A45? Don't think that exists. Suppose you see A16.
It means you're at the approach end of runway 16 and
that you better hold short of runway till clearance
from ground. A15-33 means you're approaching runway
15-33. Runway numbers are aligned to the magnet north
rounded up/down and the last digit is omitted. For
example, 15-33 means runway 15x-33x (same runway).
Say 33x is 330, then it is aligned 330 degrees and
330-180 (150) degrees. All of this information is
readily availabe on the annual publication of FAR/AIM
which is easily accessible even at Borders/B&N. If
you're really curious, go to your local flying club
and fly a plane for once! It'll be the most exhilirating
$50 you'll ever spend in your life. http://www.beapilot.com
\- oh ok good. yeah i was guessing it has something to do
bearings, but was wondering why i didnt see larger
numbers. now why in large planes, do they open the
window shades for landing [so passengers arnt
disquieted?] and turn the cabin lights on/off
during takeoff/landings.
\_ in the old days (and when you're training as a
a pilot), you turn off all the non-essential
power-hogs so that during take off you don't
overload the circuitry and blow off fuses. This
procedure has been passed down for historical
reasons and we [airlines] still do it just
because it works. As for the shades, it's just
to shut the damn passengers -csua pilot
\_ actually there have been cases where the
passenger notices something wrong with the
wing or the fuselage (which is not caught
in the sensors). But like I said all the
non-essential stuff is secondary to
flying.
\_ yeah, like the time the passenger saw
that little monster on the wing and he
was tearing apart the wing and no one
would believe him
\_ yeah!! where was that??
\_ I think it was an X-Files episode.
\_ Maybe, but it was definitely a
Twilight Zone episode.
\_ Episode with William
Shatner; in the movie with
John Lithgow. |
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