Intersection Departure and a V1 You Did Not Brief
You are cleared for takeoff on runway 27: 8,000 ft, dry, elevation 400 ft. The clearance is from intersection B, which leaves 5,400 ft. OAT 22°C, altimeter 29.88, wind 270/06. The full-length data card gives V1 136, VR 142, V2 148, accelerate-stop 3,900 ft. The 5,400-ft data give V1 118, VR 140, V2 146, accelerate-stop 2,400 ft. Both pilots briefed the full-length card because the intersection was assigned after pushback. At 110 kt during the roll, the right engine fails with a yaw and an ENG FAIL EICAS. Brake release to 110 kt used 2,350 ft. The PM calls 'engine failure' and waits for your call.
1. What is your call, and what is the stop margin using the correct data?
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Call ABORT immediately and take control of the airplane: idle, maintain centerline with rudder, maximum braking, spoilers, reverse as available, then configure for evacuation if fire is suspected.
The arithmetic supports it only because the correct data are used:
- Remaining runway: 5,400 - 2,350 = 3,050 ft.
- Accelerate-stop from 110 kt on the 5,400-ft chart: under 2,400 ft.
- Margin: at least 650 ft.
110 kt is below the correct V1 of 118 kt, so the reject is both permitted and required. If the crew had used the full-length V1 of 136, 110 kt would still have looked like a reject, but the decision would have been anchored to the wrong number, and a later failure would have produced a very different outcome.
2. Suppose the failure had occurred at 126 kt with the crew still using V1 136. What happens, and what does that reveal?
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At 126 kt the airplane is below the briefed V1 of 136, so the crew would reject. But on the 5,400-ft chart, accelerate-stop from 126 kt is roughly 3,000-3,100 ft, while brake release to 126 kt has already used roughly 3,200 ft. That leaves about 2,200 ft against a stop distance of about 3,000 ft: an overrun of perhaps 800 ft, departing the end at a low but damaging speed.
The lesson is that V1 is a function of the runway actually available, not of the runway's published length. Using full-length V1 from an intersection silently moves the decision point beyond the point where the airplane can stop. The correct action is to obtain and brief the intersection data before accepting the clearance, and if the data are not available, to decline the intersection or depart full length.
3. What preflight step prevents this, and what is the reject trigger below V1 in a twin?
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Prevention is procedural: before every takeoff, confirm the runway, intersection, and available distance against the data card actually in hand; compute V1, VR, and V2 for that available distance; and brief them aloud with the callouts. If the intersection is assigned after the brief, the takeoff is re-briefed or the clearance is declined. The data card and the clearance must describe the same runway.
Below V1, reject for anything that makes the airplane unsafe or unable to fly: engine failure or fire, loss of directional control, abnormal configuration, windshear, or a serious system warning. Above V1, continue unless the airplane cannot fly, because the stopping distance no longer exists. The judgment skill is recognizing that a reject decision is made against a briefing completed minutes earlier, not against the number painted on the data card.