Performance and Limitations

The expanded definition from AC 120-62 via the AFH: V1 is the speed selected for each takeoff, based upon approved performance data and specified conditions, representing both the maximum speed by which a rejected takeoff assures a safe stop within the remaining runway or runway and stopway, and the minimum speed which assures the takeoff can be safely completed within the remaining runway, or runway and clearway, after failure of the most critical engine at the designated speed (AFH ch. 16).

Certification anchors it: V1 may not be less than VEF plus the speed gained during the interval between engine failure and the pilot's first stopping action — applying brakes, reducing thrust, or deploying speed brakes (25.107(a)(2)). So V1 already contains recognition time; there is no cushion left for deciding at V1.

VEF is the calibrated airspeed at which the critical engine is assumed to fail for certification purposes. It is selected by the applicant but may not be less than VMCG determined under 25.149(e) (25.107(a)(1)). The chain matters for the oral: VMCG floors VEF, VEF plus the recognition increment floors V1, and V1 floors VR. If the engine fails before VEF-like speeds — below VMCG — the reject isn't a performance question at all; it's the only controllable option, because rudder alone cannot hold the centerline (25.149(e)).

VR may not be less than:

• V1
• 105 percent of VMC
• The speed that allows reaching V2 before 35 feet above the takeoff surface
• A speed producing VLOF margins over VMU (the minimum unstick speed) — e.g., 110 percent of VMU all-engines / 105 percent one-engine-inoperative (108/104 if geometry-limited) (25.107(e))

V2MIN may not be less than 1.13 VSR for two- and three-engine turboprops — and for any turbojet without provisions for a significant one-engine-inoperative stall-speed reduction, regardless of engine count — 1.08 VSR for the others, and 1.10 times VMC (25.107(b)). V2 itself must also give at least the second-segment climb gradient of 25.121(b) (25.107(c)). Never quote type numbers — they come off the takeoff data for that runway, that weight, that day (AFH ch. 16).

The minimum control speed on the ground: the calibrated airspeed during the takeoff run at which, when the critical engine is suddenly made inoperative, it is possible to maintain control using the rudder alone — without nosewheel steering — as limited by 150 pounds of force, with lateral control only to keep the wings level, and continue the takeoff safely. The demonstration standard: from the point of failure to recovery parallel to centerline, the path may not deviate more than 30 feet laterally from the centerline (25.149(e)). Established with maximum takeoff thrust, most unfavorable CG and weight, and the airplane trimmed for takeoff. Operationally this is why the pilot flying's hand comes off nosewheel steering and onto the wheel around 80 knots or VMCG (AFH ch. 16) — the certification case assumed rudder only.

The calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control with not more than 5° of bank in straight flight. Certification conditions: maximum available takeoff thrust, most unfavorable CG, airplane trimmed for takeoff, and VMC may not exceed 1.13 VSR (25.149(c)). During recovery, rudder force may not exceed 150 pounds, no reduction of thrust on the operating engines, and no dangerous attitude or heading change of more than 20° (25.149(d)). There are also approach/landing minimum control speeds — VMCL (and VMCL-2 for three-plus engines) with go-around thrust and 5° bank (25.149(f), (g)) — worth naming if your type publishes them.

From the AFH glossary: accelerate-stop distance is the distance to accelerate to V1 with all engines at takeoff power, experience an engine failure at V1, and bring the airplane to a stop; accelerate-go distance is the distance to accelerate to V1, fail the critical engine at V1, and continue the takeoff on the remaining engine(s) (AFH ch. 16). Takeoff distance itself is the greater of the one-engine-inoperative distance to 35 feet, or 115 percent of the all-engines distance to 35 feet (25.113(a)); on a wet runway the screen height drops to 15 feet (25.113(b)). When V1 is selected so the stop case and the go case need the same pavement, the field is balanced — that field length is the shortest runway that covers both outcomes, and moving V1 trades one distance against the other.

For turbine airplanes certificated under current rules, takeoff weight must allow:

• Accelerate-stop distance not exceeding runway plus stopway
• Takeoff distance not exceeding runway plus clearway, with the clearway credit limited to not greater than one-half the length of the runway
• Takeoff run not greater than the runway (121.189(c))

Corrections are required for runway, elevation, effective gradient, ambient temperature, wind component, and — where AFM limitations exist — wet versus dry surface; wet-grooved/PFC data may only be used on runways actually grooved or PFC-treated and maintained acceptably (121.189(e)).

• First segment (gear extended, between VLOF and gear fully retracted): steady gradient positive (0.3 percent for three engines, 0.5 for four)
• Second segment (gear retracted, takeoff flaps, at V2, takeoff thrust): 2.4 percent (2.7 three-engine, 3.0 four-engine), carried to at least 400 feet above the surface (25.121(b))
• Final takeoff (en route configuration, at VFTO, maximum continuous thrust): 1.2 percent (1.5/1.7) (25.121(c))
• Approach climb (go-around configuration, one engine inoperative, at not more than 1.4 VSR, gear retracted, maximum landing weight): 2.1 percent (2.4/2.7) (25.121(d))

These are certification gradients — the AFM's climb-limited takeoff weight is where they bite on a hot, high day. Second segment is almost always the limiting one; be able to say why for your type.

Takeoff weight must allow a net takeoff flight path that clears all obstacles by at least 35 feet vertically, or by 200 feet horizontally within the airport boundaries and 300 feet horizontally after passing them (121.189(d)(2)). The assumptions matter: the airplane is not banked before reaching 50 feet, and thereafter bank is limited to 15 degrees (121.189(f)) — which is why engine-out special procedures fly the published track and modest banks rather than an early turn toward downwind. "Net" means the demonstrated gradient reduced by the regulatory decrement, so the paper path sits below what the airplane should actually achieve.

No takeoff unless arrival weight allows a full-stop landing within 60 percent of the effective length of the runway from a point 50 feet above the threshold plane, at both the destination (121.195(b)) and the alternate (121.197), on the most favorable runway in still air and on the most suitable runway for the expected wind. Two modifiers: turboprop — may dispatch failing the "most suitable runway" test if an alternate is specified where it can stop within 70 percent (121.195(c)); turbojet, wet or slippery forecast — effective runway length must be at least 115 percent of the dry requirement, unless a shorter approved wet distance is in the AFM (121.195(d)).

This is a preflight gate. The separate landing distance assessment at time of arrival — and its 15 percent margin — is covered under Task III.B.

Airports report non-dry surface conditions using the Runway Condition Assessment Matrix, assigning Runway Condition Codes to each third of the runway — touchdown, mid-point, roll-out (AIM 4-3-9); the codes run from 6 (dry) down through 5–1 to 0 (nil), and the report includes the type and depth of contaminant when the runway is contaminated (SAFO 19001; AIM 4-3-9). Pair them with pilot braking action reports: Good, Good to Medium, Medium, Medium to Poor, Poor, and Nil — Nil meaning deceleration is minimal to non-existent or directional control uncertain. Two ATP-level points: friction (Mu) measurements are no longer used to report surface conditions because they don't correlate reliably with airplane braking performance, and a braking report is only reliable from a similar weight and class of airplane and recent enough for the conditions (SAFO 19001). Wet-runway definition: neither dry nor contaminated.

LAHSO — landing and holding short of an intersecting runway, an intersecting taxiway, or another designated point. The performance gate: accept only if the PIC determines the airplane can safely land and stop within the Available Landing Distance (ALD) — published in the Chart Supplement and U.S. Terminal Procedures Publications, and available from the controller on request (AIM 4-3-11). The command points:

• The PIC has final authority to accept or decline any LAHSO clearance, and pilots are expected to decline one that would compromise safety — ideally before it's issued
• Once accepted, it must be adhered to like any other ATC clearance, unless amended or an emergency occurs — but it does not preclude a rejected landing
• Read back the clearance in full, including “hold short of (runway/taxiway/point)” (AIM 4-3-11)

Preflight planning should already have determined which LAHSO combinations at the destination work for your required landing distance.

• Ill-advised reject decisions and improper technique contribute to a majority of takeoff-related commercial aviation accidents worldwide; although only about 2 percent of rejects fall in the high-speed category, aborts above 120 knots account for the vast majority of RTO overrun accidents
• The decision should be made before V1 so deceleration can begin no later than V1; if braking hasn't begun by V1, continuing is the decision by default
• Delaying the maneuver one second beyond V1 adds 4 to 6 knots on average, and crews need 3 to 7 seconds to identify and execute a reject
• Certified stopping data assumes ideal conditions — clean dry runway, maximum braking, no reverse-thrust credit; reality subtracts through contamination, wind, low density, worn brakes or tires, inoperative anti-skid, penalizing MEL or CDL items, and technique (AFH ch. 16)

State your operator's low-speed/high-speed reject split and who calls it — the PIC makes the continue/reject decision (AFH ch. 16).

Holdover time is the estimated time deicing/anti-icing fluid will prevent the formation of frost or ice and the accumulation of snow on the protected surfaces — it begins when the final application of fluid commences and expires when the fluid loses effectiveness (121.629(c)(3)). The carrier's approved ground deicing program contains the holdover timetables and procedures for adjusting HOT up or down in changing conditions. If the maximum holdover time is exceeded, takeoff is permitted only when at least one of these is true:

• A pretakeoff contamination check — conducted within five minutes prior to beginning takeoff, from outside the aircraft unless the program specifies otherwise — finds the critical surfaces free of frost, ice, and snow
• An approved alternate procedure makes that determination
• The airplane is re-deiced and a new holdover time is established (121.629(c)(3), (c)(4))

Why the clean-wing concept exists at all: contamination disrupts the smooth airflow so the boundary layer separates at an AOA lower than the critical angle — lift is greatly reduced, and as little as 0.8 millimeter of ice on the upper wing surface increases drag and reduces lift by 25 percent (PHAK ch. 5). A contaminated wing therefore stalls earlier than a stall warning system calibrated for the clean wing expects. The underlying prohibition — no takeoff with frost, ice, or snow adhering to critical surfaces — and its one authorized exception are covered under Task II.A.

Carriers load by approved average weights rather than weighing each occupant. Standard average passenger weights are built from CDC/NHANES survey data plus a clothing allowance — 5 pounds summer, 10 pounds winter — with summer weights usable May 1 to October 31 and winter November 1 to April 30; where no gender is given, the averages assume a 50/50 male-female split (AC 120-27, table 3-1 and para 3.2.1). Operators with seasonal variation that want one year-round number should use the winter weight, and baggage weights come from operator survey data (AC 120-27). The mechanics of shifting weight and resolving an out-of-limits CG are unchanged from the commercial computation you already know — the ATP layer is knowing that the whole system runs on approved averages, curtailed CG envelopes, and load planners, with the PIC still responsible for the result.

Because certified data is a flight-test ceiling, not a line-operations average. The AFH's degradation list for stopping performance is the template answer: reduced runway friction, mechanical and natural contaminants, wind, low air density, flap and bleed configuration, underinflated or failing tires, deficient brakes or RTO auto-brakes, inoperative anti-skid, penalizing MEL/CDL items, and pilot technique and proficiency (AFH ch. 16). The certified landing distance similarly excludes reverse thrust credit (AFH ch. 16). The professional response is structural, not heroic: apply the operator's required factors, prefer conservative condition inputs, and treat any performance-credit assumption (reverse, autobrakes, grooved runway) as something you must actually deliver in the deceleration.

Three ceilings compete, and the lowest wins:

• Certificated maximum operating altitude — an AFM limitation
• Thrust-limited altitude — at high altitude little excess thrust may be available for maneuvering; it is often impossible for a jet to climb and turn simultaneously (AC 61-107, para 3-3)
• Buffet-limited (aerodynamic) altitude — the margin between low-speed buffet and Mach buffet narrows with altitude and load factor: a typical jet has a 135-knot buffet-free spread at FL350 that shrinks to about 26 knots at FL450, and only 1.4 G — a 30°-bank-plus-gust kind of number — can put a heavy airplane at buffet at its optimum cruise Mach (AC 61-107, para 3-3)

So the day's optimum altitude moves with weight and temperature: burn off fuel and the buffet-limited ceiling rises, which is the logic of step climbs. Select a maximum cruising altitude that preserves buffet margin for maneuvering and expected gusts, using the type's cruise maneuver/buffet limit chart (AC 61-107). The aerodynamics behind this — coffin corner and the buffet boundaries — is Task I.D's territory, and so is descent performance (AA.I.B.K2e): the idle-descent-at-L/DMAX efficiency picture is covered there.