DESCENT CALCULATIONS

Question 1

How far away should you be from the airport at 20’000ft to be on a 3 deg approach path?

Answer 1

Every 300 ft is 1 nm
Take away three zeros and take that x3
20x3+(10%)=66nm

Question 2

If you are 15nm from touchdown, at what height should you be at for a 3 deg glide path?

Answer 2

4’500 ft

15x3=45

Question 3

Calculate a descent point from 20’000 ft at 220 tons with a 10 kts tailwind

Answer 3

82nm
1. Alt x3 +10%
2. Weight correction from 300 kts:
160t add 8nm
200t add 12nm
240t add 16nm
If already at 250 kts, halve the weight correction
If already at Vref30+80, disregard weight correction
3. Wind correction:
Tail wind, add a couple of miles
Head wind, subtract a couple of miles

Question 4

According to the FCTM, how do you calculate required distance to go for a descent?

Answer 4

Above FL150: Height above airport x 3 +20nm

Below FL150: Height above airport x 3 + 1nm per every 10 kts above 180kts

Question 5

In the FCTM, how can you calculate what height you should be at for a certain distance from the airport?

Answer 5

Multiply DTG x 3
At 240 tons subtract 5000 ft
At 200 tons subtract 4000 ft

Question 6

• What rule of thumb can you use when calculating distance required for speed reductions?
• How many nm do you need for a speed reduction from 300-250 kts?

Answer 6

1,5nm/10kts reduction
300-250= 8nm
300-180= 18nm
250-180= 10nm

Question 7

What rule of thumb can you use when calculating distance required for speed reductions?
300-250kts
300-180kts
250-180kts

Answer 7

1,5nm/10kts reduction
300-250= 8nm
300-180= 18nm
250-180= 10nm

Question 8

What is a quick way to calculate when to start descent using information you have on the PFD?

Answer 8

Turn on meter for altitude. Take the first 3 numbers and add 20nm or 10%