Avielevate / DGCA CPL papers / Air Navigation / Measurement of Elements
Measurement of Elements — DGCA CPL Air Navigation
Chapter GN12 of the Air Navigation paper. 50 practice questions in the Avielevate bank, every one with its answer key, filterable into a timed set on this chapter alone.
What this chapter covers
The learning objectives we file Measurement of Elements questions under, and how many sit behind each. These come straight out of the bank and are regenerated whenever it changes — they are what is there today, not a claim.
| Learning objective | In the bank |
|---|
| __GEN__ General | 50 questions |
Sample Measurement of Elements questions, answered and explained
Real questions from this chapter, with the answer marked and the reasoning written out — the same explanations you get inside the app.
0220069 · Measurement of Elements
The total sector distance is 2,000 NM on track 090°. The W/V (Wind Velocity) is 090°/30 kt for the first 1,000 NM and 330°/18 kt for the remaining 1,000 NM. The normal TAS on 4 engines is 380 kt and the reduced TAS on 3 engines is 260 kt. Fuel on board is 2,500 kg and the reserve fuel required is 350 kg. Fuel consumption is 360 kg/hr on 4 engines and 280 kg/hr on 3 engines., find DCP (Distance to CP) and TCP (Time to CP), and DPNR (Distance to PNR) and TPNR (Time to PNR), assuming the engine fails at the PNR (Point of No Return).
- ADCP 1,067 NM, TCP 3 hr 01 min; DPNR 1,035 NM, TPNR 2 hr 56 min
- BDCP 1,000 NM, TCP 2 hr 51 min; DPNR 1,035 NM, TPNR 2 hr 56 min
- CDCP 1,035 NM, TCP 2 hr 56 min; DPNR 1,076 NM, TPNR 3 hr 01 min
- DDCP 1,035 NM, TCP 2 hr 56 min; DPNR 1,120 NM, TPNR 3 hr 15 min
Why that is the answer
When the wind changes partway along the route, the simple formulas no longer work in one go. Instead, set up the definitions directly and split the route at the wind change (look at the diagram):
- **CP** (critical point): time to carry on = time to turn back, both at the reduced TAS (260 kt).
- **PNR** (point of no return): fuel out (normal power) + fuel back (reduced power, as the engine fails at the PNR) = usable fuel.
**Groundspeeds** (track 090°, return 270°)
First 1,000 NM, wind 090°/30, straight on the nose: at 260 kt out 230 kt, back 290 kt; at 380 kt out 350 kt.
Last 1,000 NM, wind 330°/18: θ = 120°, a tailwind out. Tailwind = 18 × cos 60° = 9 kt, crosswind = 15.6 kt. At 260 kt (drift 3.4°): 259.5 kt, so out 268.5 kt, back 250.5 kt. At 380 kt (drift 2.4°): 379.7 kt, so out 388.7 kt.
**CP** (assume it is y NM past the wind change)
Time on = (1,000 − y) ÷ 268.5
Time back = y ÷ 250.5 + 1,000 ÷ 290 = y ÷ 250.5 + 3.448
Setting them equal: 3.724 − 0.003724y = 3.448 + 0.003992y, so 0.276 = 0.007716y and y ≈ 36 NM
DCP = 1,000 + 36 ≈ 1,035 NM
TCP = 1,000 ÷ 350 + 36 ÷ 388.7 = 2.857 + 0.093 = 2.95 hr ≈ 2 hr 56 min
**PNR** (assume it is y NM past the wind change)
Usable fuel = 2,500 − 350 = 2,150 kg
Fuel out = (1,000 ÷ 350) × 360 + (y ÷ 388.7) × 360 = 1,028.6 + 0.926y
Fuel back = (y ÷ 250.5) × 280 + (1,000 ÷ 290) × 280 = 1.118y + 965.5
1,994.1 + 2.044y = 2,150, so y ≈ 76 NM and DPNR ≈ 1,076 NM
TPNR = 2.857 + 76 ÷ 388.7 = 3.05 hr, just over 3 hours (quoted as 3 hr 01 min)
So **DCP 1,035 NM, TCP 2 hr 56 min; DPNR 1,076 NM, TPNR about 3 hr 01 min**.
0220094 · Measurement of Elements
During a flight out to the PET (Point of Equal Time), the GS are found to be less then expected. The PET will be moved along track?
- Ainto wind
- Binto wind, provided the wind change continues throughout the flight
- Cdownwind, provided the wind change continues throughout the flight
Why that is the answer
The **PET** (point of equal time) is where turning back and carrying on take the same time. With a headwind on the way out, carrying on is slow and turning back is fast (the headwind becomes a tailwind). That keeps turning back the quicker choice for longer, so the PET moves past halfway, towards the side the wind blows from. We say the PET **moves into wind**. Look at the diagram.
If the groundspeeds on the way out are lower than planned, there is more headwind (or less tailwind) than expected. Using the new wind, the PET would move further **into wind**.
There is a catch. The PET depends on the wind over the **whole** route: the wind you would meet carrying on and the wind you would meet coming back. A wind change found on the first part of the route only moves the PET if that new wind keeps blowing for the rest of the flight. If it is only a local change, the PET calculation for the rest of the route may not change at all.
So the PET will move **into wind, provided the wind change continues throughout the flight**.
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Frequently asked
How many Measurement of Elements questions are there for the DGCA CPL Air Navigation paper?
Avielevate's bank carries 50 published Measurement of Elements questions for Air Navigation, mapped across 1 learning objective. Every one has its answer key, and explanations are being written across the whole bank.
How much of the Air Navigation paper is Measurement of Elements?
The DGCA does not publish a per-chapter breakdown of its papers, so nobody can honestly tell you — and we will not guess. What we can tell you is what students who have just sat a paper reported meeting, which is measured rather than rumoured: that is the exam recall report inside the app.
What is the best way to revise Measurement of Elements?
Sit a short timed set on this chapter alone, tag how sure you were of each answer, then drill the two that actually leak marks: the ones you got right while guessing, and the ones you got wrong while confident. Avielevate does that tagging for you and puts anything you got wrong back in front of you on a spaced schedule.
The rest of the Air Navigation paper
One account covers every chapter of every paper.
← All Air Navigation chapters · All six DGCA CPL papers