Nav 19 - Mental Dead Reckoning

Question 1

What is mental dead reckoning?

Answer 1

The use of formulae, rules of thumb and mental math to calculate information without preparation

Question 2

What id MDR used for?

Answer 2

Verify information makes sense or to quickly adjust aircraft speed/ heading

Question 3

What is the One-in-sixty rule?

Answer 3

One degree of drift will displace aircraft 1 nm for every 60 nm travelled

(1:1:60)

Question 4

How do you calculate Track Error?

Answer 4

Drift = Miles off x 60 / Miles along

Ex 2nm off x 60 / 30nm along = 4° track error

Question 5

How do you calculate Max drift?

Answer 5

Max drift = Wind speed x 60 / TAS

or

Max drift = Wind speed / TAS (nm/min)

Question 6

What are the steps to determine actual drift?

Answer 6

After max drift calculated, determine the approximate wind direction (to nearest 5°)
Use the Wind angle/ Fraction of Max drift/ Fraction of windspeed diagram

Question 7

How can the wind effect on G/S be determined?

Answer 7

The following formula

110 - wind angle = % of wind forming the component

• 110 is a constant

Question 8

Solve the following wind effect on G/S

Wind speed = 40 kts; wind angle = 60°

Answer 8

110-60° = 50% of 40 kts = 20 kts WC

Question 9

How are ETAs calculated? Provide an example.

Answer 9

ETAs are calculated by proportion.

If an aircraft is 5 minutes late 1/2 of the way along the leg, it will be 10 minutes late at the end of the leg if the wind remains the same.

Question 10

Review Questions

At 180 kts, how far will you travel in 10 mins?

Answer 10

30 nm

Question 11

Review Questions

There is 4° of drift, how far off track will you be after travelling 90 nm?

Answer 11

6 nm

Question 12

Review Questions

What is the formula for calculating max drift?

Answer 12

Wind speed x 60 / TAS

Wind speed / TAS (nm/min)