Worked Examples — Time, Speed, Distance

The concept lesson treats the formula D = v × t. Here are four worked exercises with typical PPL scenarios.

Exercise 1: Compute flight time

Plan: cross-country from EDLN (Mönchengladbach) to EDLE (Essen-Mülheim).

Distance = 22 NM
Planned GS = 95 kt (TAS 100 kt, slight headwind)

Question: how long does the leg take?

Solution: t = D / v = 22 / 95 = 0.2316 h = 13.9 min ≈ 14 min.

Exercise 2: Determine actual GS from flight time

Reality: 16 min actually for EDLN → EDLE (22 NM).

Question: what was actual GS?

Solution:

16 min = 16/60 h = 0.267 h
v = D / t = 22 / 0.267 = 82.4 kt (weaker than planned)

→ Wind was stronger than forecast, GS about 13 kt lower.

Exercise 3: ETA calculation

Plan: cross-country with three legs:

Leg 1: EDDM → Erding, 18 NM, planned GS 110 kt
Leg 2: Erding → Augsburg VOR, 35 NM, planned GS 105 kt
Leg 3: Augsburg VOR → EDDH (Augsburg), 8 NM, planned GS 100 kt

Off-block 1000Z, taxi + TO 8 min → waypoint 1 (departure) at 1008Z.

Question: ETA at EDDH?

Solution:

Leg 1: 18 NM / 110 kt = 0.164 h = 9.8 min ≈ 10 min → Erding 1018Z
Leg 2: 35 NM / 105 kt = 0.333 h = 20 min → Augsburg VOR 1038Z
Leg 3: 8 NM / 100 kt = 0.08 h = 4.8 min ≈ 5 min → EDDH 1043Z

ETA EDDH = 1043Z.

Exercise 4: In-flight correction

In flight between Erding and Augsburg VOR: pilot has been flying since 1018Z. Current time 1030Z (12 min after Erding). Position fix with GPS: 22 NM covered since Erding.

Question: actual GS? new ETA?

Solution:

Actual GS = 22 NM / (12/60 h) = 22 / 0.2 = 110 kt (5 kt faster than planned!)
Remaining distance to Augsburg VOR = 35 − 22 = 13 NM
Remaining time = 13 / 110 = 0.118 h = 7.1 min ≈ 7 min
New arrival Augsburg VOR = 1030Z + 7 min = 1037Z (1 min earlier than planned 1038Z).

→ ETA Augsburg consider whether further correction is needed (approach or waypoint).

Bonus: 6-min rule of thumb

6 min equals 1/10 hour. Practically:

GS 90 kt → 9 NM in 6 min
GS 120 kt → 12 NM in 6 min
GS 150 kt → 15 NM in 6 min

In the cockpit: after 6 min of flight I can estimate whether I'm on track. 9 NM covered = 90 kt; 7 NM = 70 kt → weaker GS, more headwind component than planned.