One-Engine-Inoperative Performance

• VYSE — best rate of climb with one engine inoperative. Marked with a blue radial line on most airspeed indicators. Above the single-engine absolute ceiling, VYSE yields the minimum rate of sink
• VXSE — best angle of climb with one engine inoperative
• VSSE — safe, intentional one-engine-inoperative speed. The minimum speed at which to intentionally render the critical engine inoperative
• VMC — minimum control speed, red radial line

(AFH ch. 13)

Unless otherwise noted, V-speeds given in the AFM/POH apply to sea level, standard day conditions at maximum takeoff weight. Performance speeds vary with aircraft weight, configuration, and atmospheric conditions (AFH ch. 13).

Speeds may be in mph or knots, and given as CAS or IAS. Newer AFM/POHs generally show KIAS; some V-speeds are stated in KCAS to meet regulatory requirements. Whenever available, operate from published indicated airspeeds (AFH ch. 13).

• All-engine service ceiling — the highest altitude at which the airplane can maintain a steady rate of climb of 100 fpm with both engines operating. Absolute ceiling is where climb is no longer possible
• Single-engine service ceiling — reached when the airplane can no longer maintain a 50 fpm rate of climb with OEI. Single-engine absolute ceiling is where climb is no longer possible

(AFH ch. 13)

The runway length required to accelerate to a specified speed (either VR or VLOF, as specified by the manufacturer), experience an engine failure, and bring the airplane to a complete stop (AFH ch. 13).

The horizontal distance required to continue the takeoff and climb to 50 feet, assuming an engine failure at VR or VLOF as specified by the manufacturer (AFH ch. 13).

No. The regulations do not specifically require that runway length be equal to or greater than accelerate-stop distance. Most AFM/POHs publish accelerate-stop distances only as an advisory — it becomes a limitation only when published in the limitations section of the AFM/POH (AFH ch. 13).

Experienced multiengine pilots nonetheless insist on runway lengths of at least accelerate-stop distance as a matter of safety and good operating practice.

Under ideal circumstances, a point a mere 50 feet above the takeoff elevation — little more than one wingspan above the terrain, assuming it was absolutely level and without obstructions (AFH ch. 13).

And to achieve even that meager climb the pilot had to instantaneously recognize and react to an unanticipated failure, retract the landing gear, identify and feather the correct engine, all while maintaining precise airspeed and bank angle as speed is nursed to VYSE.

As a practical planning matter, the option of continuing the takeoff probably does not exist unless the published single-engine rate-of-climb performance is at least 100 to 200 fpm (AFH ch. 13).

Even 200 fpm can be negated by thermal turbulence, wind gusts, engine and propeller wear, or poor technique in airspeed, bank angle, and rudder control.

At VYSE with maximum available power and minimum drag — meaning flaps and landing gear retracted, the failed engine's propeller feathered, and then the key element: minimizing sideslip (AFH ch. 13).

A windmilling propeller at high speed in the low range of blade angles — near flat pitch — can produce parasite drag as great as the parasite drag of the entire airframe (AFH ch. 13).

At high rpm this can make the airplane difficult or impossible to control. In the feathered position, by contrast, propeller parasite drag is at a minimum — a small part of the airplane's total drag.

If the airplane is above its single-engine absolute ceiling when the failure occurs, it slowly loses altitude. Maintain VYSE to minimize the rate of altitude loss (AFH ch. 13).

The drift-down rate is greatest immediately following the failure and decreases as the single-engine ceiling is approached. Because of performance variations from engine and propeller wear, turbulence, and pilot technique, the airplane may not maintain altitude even at its published single-engine ceiling — though any further rate of sink would likely be modest.

Because turning flight reduces climb performance. Climb should be made straight ahead or with shallow turns to avoid obstacles, to an altitude of at least 400 feet AGL before attempting a return to the airport (AFH ch. 13).

The AFH is blunt in its climb illustration: any turn, such as to return to the airport, seriously degrades the already marginal climb performance of the airplane.

Climb rate: altitude gained per unit of time — unaffected by wind.

Climb gradient: altitude per 100 feet of horizontal travel, expressed as a percentage — affected by wind: improved by a headwind component, reduced by a tailwind component (AFH ch. 13).

Obstacle clearance is a gradient problem.

No. Not all multiengine airplanes have published accelerate-go distances in their AFM/POH, and fewer still publish climb gradients. When such information is published, the figures were determined under ideal flight testing conditions — it is unlikely that this performance is duplicated in service conditions (AFH ch. 13).

With an inoperative engine, a centered ball no longer indicates zero sideslip, because of asymmetric thrust — in fact, no flight deck instrument directly indicates the zero-sideslip condition (AFH ch. 13).

That's different from normal flight: with a single-engine airplane, or a twin with both engines operating, sideslip is eliminated when the ball is centered — the airplane presents its smallest profile to the relative wind and drag is at a minimum. Pilots know this as coordinated flight.

Two control inputs can counteract asymmetric thrust: yaw from the rudder, and the horizontal component of lift from bank. Used individually, neither is correct (AFH ch. 13).

1. Wings level, ball centered — requires large rudder toward the operative engine. Result: a moderate sideslip toward the inoperative engine, reduced climb performance, and VMC significantly higher than published because there is no horizontal component of lift helping the rudder
2. Ailerons alone (no rudder) — requires an 8 to 10 degree bank toward the operative engine, ball displaced well toward the operative engine, and climb performance greatly reduced by the large sideslip. Instructors should not normally demonstrate this
3. Rudder and ailerons together, in the proper combination — approximately 2 degrees of bank toward the operative engine, ball displaced one-third to one-half toward the operative engine. Result: zero sideslip and maximum climb performance

The AFH gives ranges, because it varies by model, power, and airspeed.

Bank angle: varies among airplanes from one and one-half to two and one-half degrees toward the operating engine.

Ball position: one-third to one-half of a ball width from instrument center, toward the operative engine (AFH ch. 13).

These recommendations apply to reciprocating twins flown at VYSE with the inoperative engine feathered. The zero-sideslip ball position for straight flight is also the zero-sideslip position for turning flight.

Because that is how they were flown in testing. The AFM/POH performance charts for one-engine-inoperative flight were determined at zero sideslip, so this technique must be used to obtain the charted OEI performance (AFH ch. 13).

Any attitude other than zero sideslip increases drag, decreasing performance — and whether the airplane can climb at all depends on weight, density altitude, and pilot technique.

A piece of string or yarn approximately 18 to 36 inches long, taped to the base of the windshield or the nose near the windshield along the airplane centerline (AFH ch. 13).

In two-engine coordinated flight the relative wind aligns it with the longitudinal axis — straight up the center of the windshield. That is zero sideslip. With an engine out, a particular combination of aileron and rudder likewise establishes zero sideslip, and the string aligns itself vertically to show it. Maintain adequate altitude, flying speed, and caution if experimenting.

With one engine feathered or set to zero thrust and the airplane slowed to VYSE, climb with maximum power on the remaining engine. That reveals the precise bank angle and ball deflection for zero sideslip and best climb performance (AFH ch. 13).

Zero thrust means power set on one engine such that the drag from its rotating propeller equals that of a stopped, feathered propeller — the standard training substitute for an actual feather.