More newbie Qs

Ramapriya wrote:

1. How does a pilot get to know the distance to the airport that he has
to land in, so that he plans his descent accordingly, in planes that
don't have an onboard computer?

If the aircraft has no electronic means of determining position, the pilot uses
"pilotage" to keep track of his location. Basically, the pilot notes things on
the chart close to his course that can be seen from the air; these are called
"waypoints". Once in the air, the speed over the ground can be determined by
timing how long it takes to fly between two of these waypoints. The pilot can
then figure out the point at which he wants to start the descent and how long it
will take to reach that point from the closest waypoint to it. Pass over that
waypoint and start your descent at the appropriate time.

2. What exactly is a VOR? Sounds like it's a constant all-direction
radio transmission from a fixed point on the airport to help locate
where the airstrip is.

Pretty much, except that VORs aren't always (or even usually) located at
airports. The transmitter broadcasts a signal that is modulated in such a way
that the receiver can tell in what direction the transmitter lies. The pilot can
then twist a dial to center a needle on an instrument called a "course deviation
indicator" and read off the direction.

3. If a pilot needs to land at an airport that doesn't have a control
tower, how does he figure its elevation so that he may plan his
descent?

The elevation is recorded on charts and in airport directories.

4. When a pilot says, "Give me a vector", what does he actually mean?

He's asking someone to tell him what heading to fly.

5. When pilots use miles in conversations, does it mean the miles we
normally use, or is it always nautical miles?

In conversation with ATC, we use nautical miles.

6. The difference between airspeed and groundspeed is that airspeed is
the net of the plane's speed and opposing windspeed, while groundspeed
is just the plane's speed. Right?

Airspeed is the speed the aircraft is traveling through the air. Groundspeed is
the speed the aircraft is traveling over the ground. The speedometer in an
aircraft measures airspeed (with varying degrees of accuracy). This is called
"indicated airspeed". Pilots can correct this for inaccuracies to determine the
actual (or "true") airspeed. Let's say that I'm flying into a 20 knot wind and
my airspeed indicator shows I'm going 100 knots and it's accurate. My
groundspeed will be 80 knots. If I then turn around and go the other way, my
groundspeed will be 120 knots, but my airspeed will not change.

7. What is "density altitude", and how to compute it? If I'm not wrong,
its use is to plan the length of takeoff roll and angle of climb.

It's a measure of air density and, yes, we use it to calculate the effects of
atmosperic conditions on the performance of the plane. Low pressure, high
temperature, and high humidity all reduce air density and reduce performance. An
airport may be at 90' ASL, but the plane performs as if the airport were at
3,000' ASL if the density altitude is 3,000' (as it may be in high summer).
Usually charts or calculators are used to determine density altitude. I get the
current figures as part of weather briefings.

First, set the altimeter to 29.92 Hg and read the altitude. This is called the
"pressure altitude" and will frequently be different from the actual elevation
of the airport. Then I would use a graph from my pilot's manual to determine the
density altitude for that pressure altitude and the current temperature. It's 7
degrees C at the moment and I am close to sea level. From my graph, that
temperature at that level reduces density altitude by about 800', so an aircraft
will perform better than usual. If the temperature were 30 degrees C, the
density altitude at sea level would be about 2,000' when the air pressure is
29.92 Hg.

George Patterson
The desire for safety stands against every great and noble enterprise.