I85PREP
⌘ K
EASA ATPL 033 Flight Planning study materials
EASA ATPL 033 Flight Planning study resources

EASA ATPL 033 Flight Planning: Long-range and extended-range planning: EDTO, equal time point and critical fuel

EASA ATPL 033 Flight Planning · Work through your exam, one topic at a time.

All guide sections

Long-range and extended-range planning: EDTO, equal time point and critical fuel

Domain 9 covers long-range and extended-range operations: EDTO approval, adequate aerodromes, equal time points and critical fuel.

Rules and definitions

  • Without specific approval a two-engine aeroplane must remain within 60 minutes' flying time at one-engine-inoperative cruise speed from an adequate aerodrome; EDTO approval extends the threshold to 120 or 180 minutes, depending on type and route.
  • An adequate aerodrome has suitable runways, approach aids, forecasts at or above minima for the expected window and adequate rescue and fire fighting. A suitable en-route alternate must additionally be open with the required services.
  • The approval time is converted to a distance using one-engine-inoperative speed in still air for the threshold check; wind is applied for the practical diversion calculation.

Equal time point and critical fuel

  • ETP distance from A = total distance × OEI GS toward B / (OEI GS toward B + OEI GS back to A). ETPs are drawn separately for engine failure and for depressurised cases.
  • The critical fuel scenario assumes the worst credible combination: failure at the critical point, descent, cruise at the appropriate level and speed, hold, approach and missed approach, plus reserves. The en-route alternate is chosen so that fuel suffices.

Worked example

A to B is 2,000 NM. With one engine, ground speed toward B is 400 kt (420 kt TAS, 20 kt headwind) and back to A is 460 kt (40 kt tailwind). Time to the ETP = 2,000 / (400 + 460) = 2.33 h, so the ETP is 400 × 2.33 = 930 NM from A. Beyond 930 NM from A the aeroplane is nearer B in time, so B becomes the diversion aerodrome. Note that the fuel critical point may lie on the other side of the ETP, because fuel to divert depends on the critical fuel burn-off, not only on time.

Traps

  • Using all-engine cruise speed for the ETP or the threshold distance.
  • Applying wind in the same sense on both directions.
  • Confusing the time ETP with the fuel critical point.
  • Omitting the hold and missed approach from the critical fuel.