Chapter 3 - Pressure

Question 1

Why are we interested in Px

Answer 1

Because A/C can base their height on it, to aid with traffic and terrain avoidance

Question 2

How do we measure Px on the ground

Answer 2

Mercury barometer using formula P = Force/Area

Question 3

How do we measure Px on A/C

Answer 3

Using a simple Aneroid Barometer

Question 4

Air moves because of

Answer 4

Px differences

Question 5

Elongated bars are called what for High and Low Px

Answer 5

Ridge/wedge

Troughs

Question 6

In the northern hemisphere which way does the wind move round high and low Px

Answer 6

Clockwise round Hpx

Anti clockwise round Lpx

Question 7

Low Px air is moving how

Answer 7

Convergent - asending air - adiabatic cooling

Question 8

High Px air is moving how

Answer 8

Diverging - descending air - adiabatic warming

Question 9

Describe the effect of temperature on Px in column of air

Answer 9

colder it will over read for the true height - a/c believes to be higher than actual

warmer it will under read for the true height - a/c believes to be lower than actual

Question 10

constant pressure charts can be display what and are measured in

Answer 10

Isohypes (Contour) lines of equal Px above the surface

Metres x 10 = decometres/DAMS

Question 11

Which air falls more quickly out of hot and cold

Answer 11

cold

Question 12

What does QFE =

Answer 12

Field Elevation - usually measure accurately

Question 13

What does QNH =

Answer 13

Nautical Height - calculated using QFE - ISA Lapse rate

Question 14

What does QFF =

Answer 14

calculated using QFE - actual pressure lapse rate for the day

Question 15

What does SPS =

Answer 15

Standard Pressure Setting = 1013.25H Pa Mainly used in commercial a/c

Question 16

What is the Lapse rate of pressure

Answer 16

27 ft / H Pa - 8 m / H Pa

Question 17

What are regional pressure settings? (RPS)

Answer 17

When flying below transition altitude, pilots can use RPS which is valid for an hour in that region

Question 18

If you wind on Px on the Altimeter

Answer 18

It increases the indicated height

Question 19

How is Transition Altitude calculated? And what do we do?

Answer 19

It is published

Swap to SPS

Question 20

How do we calculate Transition Level? And what do we do?

Answer 20

It is calculated for that day.

Swap to QNH

Question 21

What happens in Cold to Warm air

Answer 21

Indicated Altitude will be higher = safer

Question 22

What happens to Warm to Cold air

Answer 22

Indicated Altitude will be lower = dangerous

Question 23

what is the calculation for working out temp correction

Answer 23

for every 10 degrees - apply 4%

Question 24

Temp calculation only applies where?

Answer 24

Air is

Question 25

Valleys do what to altimeters?

Answer 25

convergent duct so Px goes down so altimeter will read higher