14.4 V-Speeds, Markings, and Limitation Placards

ACS PA.I.F is performance and limitations. The speeds painted on the airspeed indicator and printed in the AFM Limitations section are not conveniences. 14 CFR 91.9(a) says no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards. Exceeding Vne, extending full flaps above Vfe, or ignoring a baggage-compartment placard is the same class of rule as busting a weight limit in 14.2.

The V-speeds PAR actually uses

14 CFR 1.2 defines most of the letters. Best-glide is a PHAK / AFM speed usually written Vg in training materials; it is not itself a 1.2 abbreviation. Learn the meaning, then take this airplane’s knots from the AFM — never from a friend who flies a different model.

Vx versus Vy. Vx clears an obstacle in the shortest distance. Vy gets you to altitude in the least time. As altitude increases, published Vx usually rises and Vy falls until they meet at the absolute ceiling. That pair is a Chapter 13 performance item; the limitation item is “use the AFM number for this weight and altitude,” not a memorized 62 / 74 that belonged to a different year of the same type.

Vlo versus Vle. While the gear is in transit the mechanism and doors are more vulnerable, so Vlo is the lower “you may move it” speed. Once the gear is down and locked, Vle is the higher “you may leave it there” speed. Fixed-gear PAR trainers do not use either number in the airplane, but the knowledge test still asks which letter is which.

Vg is the speed that gives the maximum lift-to-drag ratio in the published glide configuration — the farthest glide for a given height in still air. It is not Vy, and it is not the bottom of the green arc.

Color arcs — what the ASI is allowed to teach you

PHAK’s airspeed-indicator marking scheme, matching certification practice:

• White arc: Vso to Vfe. Flap-operating range in the landing-flap sense. You may fly this slow only with flaps down as the AFM allows, and you may not have full flaps out above the top of the white.
• Green arc: Vs1 to Vno. Normal operating range, flaps up (the specified clean stall at the bottom).
• Yellow arc: Vno to Vne. Caution range. Smooth air only. Structural margin against gusts is gone. If it gets rough, slow into the green.
• Red radial line: Vne. Never exceed, smooth air included. Flutter and structural failure live past that mark.

The ASI does not paint Vr, Vx, Vy, Vg, Va, Vlo, or Vle. Those live in the AFM and on placards. “Anywhere in the green is a safe maneuvering speed” is false; Va is usually below Vno and moves with weight.

Flap operating versus flap extended

Vfe is the maximum speed with the flaps in a given extended position. You also must be at or below that speed to operate (move) the flaps to that position. Light trainers usually publish one Vfe, and that number is the top of the white arc — typically the full-flap limit.

Many AFMs also publish a higher speed for a first notch of approach flaps than for landing flaps. The white arc does not grow to that higher number. Extending 10° above the top of the white can be legal if that AFM lists a higher partial-flap Vfe; extending full flaps there is not. Read the limitations table, not just the paint. Jets sometimes split flap-operating and flap-extended speeds more finely. PAR’s job is: white arc = full-flap window; any other flap speed is an AFM number.

Va decreases with weight — the painted-constant trap

Design maneuvering speed (Va) is the speed at which, in smooth air, one abrupt full deflection of a single flight control will stall the wing before the structure reaches limit load. Chapter 10 already used that sentence. The limitation half is the weight correction.

A lighter airplane stalls slower. At the gross-weight Va it is farther from the stall, so the same full elevator can build a load factor above limit before the wing quits. Therefore Va is reduced when the airplane is light:

Va_actual = Va_published × √(W_actual ÷ W_published)

Use the Example 1 airplane. Published Va is 99 KIAS at 2,550 lb. At the 2,130-lb two-up loading:

√(2,130 ÷ 2,550) = √0.8353 ≈ 0.914

99 × 0.914 ≈ 90 KIAS

Using 99 KIAS because “that is what the placard says” is the miss. The placard is the heavy number unless the AFM prints a table of Va versus weight. Va is not Vno, not the top of the green, and not a speed you hold while yanking more than one control in a gust.

91.9, the AFM, the POH, and the stickers

14 CFR 91.9(a) — comply with the operating limitations in the approved flight manual, the markings, and the placards.

91.9(b) — if 14 CFR 21.5 requires an Airplane Flight Manual (airplanes that had no flight time before March 1, 1979 and were not already certificated with an AFM, which in practice is the modern fleet), a current, approved AFM must be available in the aircraft. If 21.5 does not require an AFM, the airplane may be operated with the approved combination of manual material, markings, and placards that does exist — still 91.9(a).

AFM versus POH. The Airplane Flight Manual is the FAA-approved document. The Pilot’s Operating Handbook is the GAMA-standard format most manufacturers use. On a modern trainer the POH contains the AFM: Section 2 Limitations (and usually the approved parts of Emergency and Performance) is regulatory. Other POH pages can be manufacturer information that is not itself a 91.9 limitation. When in doubt, the Limitations section, the instrument markings, and the required placards win.

Placards that 91.9 will actually bite you on: maximum baggage weights and “solo from front seat only,” published Va, flap-speed reminders, “day-VFR only” if that is how the airplane is equipped, occupant-warning placards, and any operating-limitation sticker the TCDS or AFM requires to be in view. A missing required placard is an airworthiness problem (Chapter 3) and a 91.9 problem.

Scenario: Alex’s yellow-arc descent

Alex is light — the 2,130-lb Example 1 airplane — descending through smooth air at the top of the yellow because “redline is the only real limit.” Vno is already behind him; Vne is the red line he has not hit yet. A ridge-wave bump at that speed is a structural event, and the Va he should have been near in the first ripple is about 90 KIAS, not the 99 on the gross-weight placard. He slows into the green, then toward that reduced Va, and he treats the color code and 91.9 as the same sentence.