Define V1 and explain why it changes with runway length, slope, and contamination.
What they are really probing: They want decision-speed logic, not just the textbook definition.
Model answer
Open with the regulatory definition: V1 is the maximum speed at which the pilot must take the first action (brakes, thrust idle, speedbrake) to stop within the ASDA, and the minimum speed at which take-off can be continued with one engine inoperative within the TODA. Then walk through the three balancing fields: accelerate-stop distance (ASD), accelerate-go distance (AGD), and the required take-off distance. Explain that V1 lives where ASD = AGD on a balanced field. Show how shortening the runway forces V1 down (less room to stop), how contamination reduces deceleration so V1 drops further, and how an upslope helps stopping but hurts going. Close by tying it to EK's typical OFP V1/Vr/V2 set on long ETOPS-heavy 777 sectors out of DXB 12R/30R where temperature and slope drive performance.
What fails this question
- — Reciting only the FAR/CS-25 definition with no decision logic
- — Forgetting V1 is bounded by VMCG and VR
- — Saying V1 always equals VR on long runways
Follow-ups they ask next
- — What is your action if engine fail occurs 5 knots before V1?
- — How does the Boeing 777 'improved climb' affect V1?
- — Define VMCG and explain why it limits V1 from below.