C3 Direction

Question 1

When measuring a true bearing from a navigational chart for a certain route you want to follow, why is it better to measure the bearing from the middle of the track and not the start of it?

Answer 1

Because as the track cuts the meridians of longitude at different angles (like a great circle) so you can get a more accurate reading by reading from the middle of the track

Question 2

What is Magnetic variation?

Answer 2

The angular difference between True and Magnetic North

Question 3

What is an isogonal?

Answer 3

A line on a map joining all the places with the same magnetic variation

Question 4

What is an agonic line?

Answer 4

An isogonal that joins the places that have a magnetic variation of 0 degrees (Magnetic North = True North)

Question 5

U have a True Heading of 065 degrees. You magnetic variation is 5 degrees West. What is ur magnetic track?

Answer 5

070 degrees.

Variation West, Magnetic Best.

So u add 5 degrees to 065

Question 6

U have a True Heading of 034 degrees, with a magnetic variation of 4 degrees East. What is ur Magnetic track?

Answer 6

030 degrees

Variation EAST, Magnetic LEAST.

So u subtract 4 degrees from 034

Question 7

What is Compass deviation?

Answer 7

The angular difference between Magnetic and Compass North

Question 8

What is Magnetic Dip?

Answer 8

A compass error, whereby the Centre of Gravity of a compass is shifted causing errors that often occur during acceleration / turning.

Question 9

What is meant by the linear acceleration error?

Answer 9

The compass has magnetic dip, and so the CG of the compass is not on the pivot, meaning that when the aircraft accelerates or decelerates, the compass will read slightly inaccurately whilst the aircraft accelerates / decelerates

Question 10

On what headings is Linear acceleration error non existent and why?

Answer 10

On headings 360 and 180

Because of compass dip, the CG of the compass is displaced directly towards the North or South Pole, so the CG is still in the plane of the magnetic lines of force that point North / South. So when accelerating, the compass can’t swing since the CG is in line with the pivot, unable to produce a moment to spin the compass.

Imagine flying Northbound ( heading 360). The magnet in the compass has its North Pole pointing straight ahead, or parallel to the aircraft. Because of compass dip, the compass’s CG is making the magnet fall forward towards the North Pole. Because the CG is not displaced slightly left or right of the magnet like flying East or West, if you accelerate towards the North, the compass won’t rotate.

Question 11

When flying on an Easterly or Westerly heading in the Northern hemisphere, what apparent turn does the compass point to in an acceleration and deceleration?

Answer 11

On an acceleration, the compass will indicate an apparent turn towards the North

On a deceleration, the compass will indicate an apparent turn towards the South

Question 12

Why should u level the wings earlier when turning through the North Pole in the Norther Hemisphere

Answer 12

Because the compass dip makes the compass act sluggishly, so it is a little behind. So if you want to go from 020 to 340 (turning through the North), roll out at around 345 degree to account for the delay

Question 13

What are the rules for leveling out when turning through a pole to account for turning errors?

Answer 13

When flying through the closer pole, level out earlier

When flying through the further pole, level out later

Question 14

Ur flying in the Southern Hemisphere, and want to turn from heading 030 to 330 through the North. Should u level off earlier or later to account for turning error of the compass?

Answer 14

Later

Since the compass dip is slightly less as ur turning through the further pole, the compass will react very lively and so the compass will read a few degrees ahead of what u really are.

Question 15

What is the acronym for accounting for turning errors in the Northern Hemisphere?

Answer 15

NESL

NORTH EARLY SOUTH LATE

Question 16

How is a gyroscope spun?

Answer 16

Either electrically or through a vacuum pump