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Modern design, engineering, and manufacturing technology have produced outstanding multiengine airplanes. Their utility and acceptance have more than fulfilled the expectations of their builders. As a result of this rapid development and increasing use, many pilots have found it necessary to make the transition from single-engine airplane to those with two or more engines and complex equipment. Good basic flying habits formed during earlier training, and carried forward to these new sophisticated airplanes, will make this transition relatively easy, but only if the transition is properly directed.
The following paragraphs discuss several important operational differences which must be considered in progressing from the simpler single-engine airplanes to the more complex multiengine airplanes.
Preflight visual inspections of the exterior of the airplane should be conducted in accordance with the manufacturer's operating manual. The procedures set up in these manuals usually provide for a comprehensive inspection, item by item in an orderly sequence, to be covered on a complete check of the airplane. The transitioning pilot should have a thorough briefing in this inspection procedure, and should understand the reason for checking each item.
The transitioning pilot must realize that multiengine airplanes characteristically have many more controls, switches, instruments. and indicators. Failure to position or check any of these items may have much more serious results than would a similar error in a single-engine airplane. Only definite procedures. systematically planned and executed can ensure safe and efficient operation. The cockpit checklist provided by the manufacturer in the operations manual must be used, with only those modifications made necessary by subsequent alterations or additions to the airplane and its equipment.
In airplanes which require a copilot, or in which a second pilot is available, it is good practice for the second pilot to read the checklist, and the pilot in command to check each increased item by actually touching the control or device and repeating the instrument reading or prescribed control position in question, under the careful observation of the pilot calling out the items on the checklist (Fig. 16-2).
Even when no copilot is present, the pilot should form the habit of touching, pointing to, or operating each item as it is read from the checklist.
In the event of an in-flight emergency, the pilot should be sufficiently familiar with emergency procedures to take immediate action instinctively to prevent more serious situations. However, as soon as circumstances permit, the emergency checklist should be reviewed to ensure that all required items have been checked.
Tailwheel-type multiengine airplanes are usually equipped with tailwheel locks which can be used to advantage for taxiing in a straight line especially in a crosswind. The tendency to weathervane can also be neutralized to a great extent in these airplanes by using more power on the upwind engine, with the tailwheel lock engaged and the brakes used as necessary.
On nosewheel-type multiengine airplanes. the brakes and throttles are used mainly to control the momentum and steering done principally with the steerable nosewheel. The steerable nosewbeel is usually actuated by the rudder pedals, or in some airplanes by a separate hand-operated steering mechanism.
No airplane should be pivoted on one wheel when making sharp turns, as this can damage the landing gear. Tires, and even the airport pavement. All turns should be made with the inside wheel rolling, even if only slightly.
Brakes may be used, as with any airplane, to start and stop turns while taxiing. When initiating a turn though, they should be used cautiously to, prevent overcontrolling of the turn. Brakes should be used as lightly as practicable while taxiing to prevent undue wear and heating of the brakes and wheels, and possible loss of ground control. When brakes are used repeatedly or constantly they tend to heat to the point that they may either lock or fail completely. Also, tires may be weakened or blown out by extremely hot brakes. Abrupt use of brakes in multiengine as well as single-engine airplanes, is evidence of poor pilot technique; it not only abuses the, airplane, but may even result in loss of control.
Due to the greater weight of multiengine airplanes, effective braking is particularly essential. Therefore, as the airplane begins to move forward when taxiing is started, the brakes should be tested immediately by depressing each brake pedal. If the brakes are weak, taxiing should be discontinued and the engines shut down.
Looking outside the cockpit while taxiing becomes even more important in multiengine airplanes. Since these airplanes are usually somewhat heavier, larger, and more powerful than single-engine airplanes they often require more time and distance to accelerate or stop, and provide a different perspective for the pilot. While it usually is not necessary to make S-turns to observe the taxiing path, additional vigilance is necessary to avoid obstacles, other aircraft, or bystanders.
Multiengine airplanes should be retrimmed in flight for each change of attitude, airspeed, power setting, and loading. Without such changes, constant application of firm forces on the flight controls is necessary to maintain any desired flight attitude.
In the interest of safety it is important that the flight. crew have a plan of action to cope with engine failure during takeoff. It is recommended that just prior to takeoff the pilot in command review. or brief the copilot on takeoff procedures. This briefing should consist of at least the engine out minimum control speed, best all-engine rate of climb speed, best single-engine rate of climb speed, and what procedures will be followed if an engine fails prior to reaching minimum control speed. This latter speed is the minimum airspeed at which safe directional control can De maintained with one engine inoperative and one engine operating at full power.
The multiengine (light twin) pilot's primary concern on all takeoffs is the attainment of the engine-out minimum control speed prior to liftoff. Until this speed is achieved, directional control of the airplane in flight will be impossible after the failure of an engine, unless power is reduced immediately on the operating engine. If an engine fails before the engine-out minimum control speed is attained. THE PILOT HAS NO CHOICE BUT TO CLOSE BOTH THROTTLES. ABANDON THE TAKEOFF. AND DIRECT COMPLETE ATTENTION TO BRINGING THE AIRPLANE TO A SAFE STOP ON THE GROUND.
The multiengine (light-twin) pilot's second concern on takeoff is the attainment of the single-engine best rate-of-climb speed in the least amount of time. This is the airspeed which will provide the greatest rate of climb when operating with one engine out and feathered (if possible), or the slowest rate of descent. In the event of an engine failure, the single-engine best rate-of-climb speed must be held until a safe maneuvering altitude is reached, or until a landing approach is initiated. When takeoff is made over obstructions the best angle-of-climb speed should be maintained until the obstacles are passed, then the best rate of climb maintained.
The engine-out minimum control speed and the single-engine best rate-of-climb speed are published in the airplane's FAA approved flight manual, or the Pilot's Operating Handbook. These speeds should be considered by the pilot on every takeoff, and are discussed in later sections of this chapter.
It usually is inadvisable to execute full stalls in multiengine airplanes because of their relatively high wing loading; therefore, practice should be limited to approaches to stalls (imminent), with recoveries initiated at the first physical indication of the stall. As a general rule, however, full stalls in multiengine airplanes are not necessarily violent or hazardous.
The pilot should become familiar with imminent stalls entered with various flap settings, power settings, and landing gear positions. It should be noted that the extension of the landing gear will cause little difference in the stalling speed, but it will cause a more rapid loss of speed in a stall approach.
Power-on stalls should be entered with both engines set at approximately 65 percent power. Takeoff power may be used provided the entry speed is not greater than the normal lift-off speed. Stalls in airplanes with relative low power loading using maximum climb power usually result in an excessive nose-high attitude and make the recovery more difficult.
Because of possible loss of control, stalls with one engine inoperative or at idle power and the other developing effective power are not to be performed during multiengine flight tests nor should they be practiced by applicants for multiengine class ratings.
The same techniques used in recognition and avoidance of stalls of single-engine airplanes apply to stalls in multiengine airplanes. The transitioning pilot must become. familiar with the characteristics which announce an approaching or imminent stall, the indicated airspeed at which it occurs, and the proper technique for recovery.
The increase in pitch attitude for stall entries should be gradual to prevent momentum from carrying the airplane into an abnormally high nose-up attitude with a resulting deceptively low indicated airspeed at the time the stall occurs. It is recommended that the rate of pitch change result in a 1 knot-per-second decrease in airspeed. In all stall recoveries the controls should be used very smoothly, avoiding abrupt pitch changes. Because of high gyroscopic stresses, this is particularly true in airplanes with extensions between the engines and propellers.
Smooth control manipulation is particularly a requisite of flight at minimum or critically slow airspeeds. As with all piloting operations, a smooth technique permits the development of a more sensitive feel of the controls with a keener sense of stall anticipation. Flight at minimum or critically slow airspeeds gives the pilot an understanding of the relationship between the attitude of an airplane, the feel of its control reactions and the approach to an actual stall.
Generally, the technique of Right at minimum airspeeds, is the same in a multiengine airplane as it is in a single-engine airplane. Because of the additional -equipment in the multiengine airplane, the transitioning pilot has more to do and observe, and the usually slower control reaction requires better anticipation. Care must be taken to observe engine temperature indications for possible overheating, and to make necessary power adjustments smoothly on both engines at the same time.
The accepted technique for making stabilized landing approaches is to reduce the power to a predetermined setting during the arrival descent so the appropriate landing aflar extension speed will be attained in level flight as the downwind leg of the approach pattern is entered (Fig. 16-3). With this power setting, the extension of the landing grear (when the airplane is on the downwind leg opposite the intended point of touchdown) will further reduce the airspeed to the desired traffic pattern airspeed. The manufacturer's recommended speed should be used throughout the pattern. When practicable, however, the speed should be compatible with other air traffic in the traffic pattern. When within the maximum speed for flap extension, the flaps may be partially lowered if desired, to aid in reducing the airspeed to traffic pattern speed. The angle of bank normally should not exceed 300 while turning onto the legs of the traffic pattern.
The prelanding checklist should be completed by the time the airplane is on base leg so that the pilot may direct full attention to the approach and landing. In a power approach, the airplane should descend at a stabilized rate, allowing the pilot to plan and control the approach path to the point of touchdown. Further extension of the flaps and slight adjustment of power and pitch should be accomplished as necessary to establish and maintain a stabilized approach path. Power and pitch changes during approaches should in all cases he smooth and gradual.
The airspeed of the final approach should be as recommended by the manufacturer; if a recommended speed is not furnished, the airspeed should be not less than the engine-out best rate-of-climb speed (Vyse) until the landing is assured, because that is the minimum speed at which a single-engine go-around can be made if necessary. IN NO CASE SHOULD THE APPROACH SPEED BE LESS THAN THE CRITICAL ENGINE-OUT MINIMUM CONTROL SPEED. If an engine should fail suddenly and it is necessary to make a go-around from a final approach at less than that speed, a catastrophic loss of control could occur. As a rule of thumb, after the wing flaps are extended the final approach speed should be gradually reduced to 1.3 times the power-off stalling speed (1.3 Vso).
The roundout or flare should be started at sufficient altitude to allow a smooth transition from the approach to the landing attitude. The touchdown should be smooth, with the airplane touching down on the main wheels and the airplane in a tail-low attitude, with or without power as desired. The actual attitude at touchdown is very little different in nosewheel- and tailwheel-type airplanes. Although airplanes with nosewheels should touch down in a tail-low attitude, it should not be so low as to drag the tail on the runway. On the other hand, since the nosewheel is not designed to absorb the impact of the full weight of the airplane, level or nose-low attitudes must be avoided.
Directional control on the rollout should be accomplished primarily with the rudder and the steerable nosewheel, with discrete use of the brakes applied only as necessary for crosswinds or other factors.
It should be remembered that FAA requires that most airplanes have satisfactory control capabilities when landing in a direct crosswind of not more than 20 percent of the stall speed (0.2 Vso). Thus, an airplane with a power-off stalling speed of 60 knots has been designed for a maximum direct crosswind of 12 knots (.2 x 60) on landings. Though skillful pilots may successfully land in much stronger winds, poor pilot technique is apt to cause serious damage in even more gentle winds. Some light and medium multiengine airplanes have demonstrated satisfactory control with crosswind components greater than .2 Vso. If this has been done it will be noted in the Pilot's Operating Handbook under operations limitations.
The two basic methods of making crosswind landings, the slipping approach (wing-low) and the crabbing approach may be combined. These are discussed in the chapter on Approaches and Landings.
The essential factor in all crosswind landing procedures is touching down without drift, with the heading of the airplane parallel to its direction of motion. This will result in minimum side loads on the landing gear.
Unless absolutely necessary, the decision to go around should not be delayed to the point where the airplane is ready to touch down (Fig. 16-4). The more altitude and time available to apply power., establish a climb, retrim, and set up a go-around configuration. the easier and safer the maneuver becomes. When the pilot has decided to go around, immediate action should be. taken without hesitation, while maintaining positive control and accurately following the manufacturer's recommended procedures.
Go-around procedures vary with different airplanes, depending on their weight, flight characteristics, flap and retractable gear Systems, and flight performance. Specific procedures must be learned by the transitioning pilot from the Pilot's Operating Handbook, which should always be available in the cockpit.
There are several general go-around procedures which apply to most airplanes, and are worth pointing out:
The basic requirements of a successful go-around, then, are the prompt arrest of the descent, and the attainment and maintenance of the best rate-of-climb airspeed.
At any time the airspeed is faster than the flaps-up stalling speed, the flaps may be retracted completely without losing altitude if simultaneously the angle of attack is increased sufficiently. At critically slow airspeeds, however, retracting the flaps prematurely or suddenly can cause a stall or an unanticipated loss of altitude. Rapid or premature retraction of the flaps should be avoided on go-arounds, especially when close to the ground, because of the careful attention and exercise of precise pilot technique necessary to prevent a sudden loss of altitude. It generally will be found that retracting the flaps only halfway or to the specified approach setting decreases the drag a relatively greater amount than it decreases the lift.
The FAA approved Airplane Flight Manual or Pilot's Operating Handbook should be consulted regarding landing gear and flap retraction procedures because in some installations simultaneous retraction of the gear and flaps may increase the flap retraction time, and full flaps create more drag than the extended landing gear.
From the transitioning pilot's point of view. the basic difference between a light-twin and single-engine airplane is the potential problem involving engine failure. The information that follows is confined to that one basic difference.
The term "light-twin" as used here pertains to the propeller driven airplane having a maximum certificated gross weight of less than 12,500 pounds, and which has two reciprocating engines mounted on the wings.
Before the subject of operating technique in light twin-engine airplanes can be thoroughly discussed, there are several terms that need to be reviewed. "V" speeds such as Vx, Vxe, Vy, Vyse, and Vmc are the main performance speeds the light-twin pilot needs to know in addition to the other performance speeds common to both twin-engine and single-engine airplanes. The airspeed indicator in twin-engine airplanes is marked (in addition to other normally marked speeds) with a red radial line at the minimum controllable airspeed with the critical engine inoperative, and a blue radial line at the best rate-of-climb airspeed with one engine inoperative (Fig. 16-5).
Vx - The speed for best angle of climb. At this speed the airplane will gain the greatest height, for it. given distance of forward travel. This speed is used for obstacle clearance with all engines operating. However, this speed is different when one engine is inoperative. and in this handbook is referred to as Vxse (single-engine).
Vy - The speed for the best rate of climb. This speed will provide the maximum altitude gain for a given period of time with all engines operating. However, this speed too will be different when one engine is inoperative and in this handbook is referred to as Vyse (single-engine).
Vme - The minimum control speed with the critical engine inoperative. The term Vmc can be defined as the minimum airspeed at which the airplane is controllable when the critical engine is suddenly made inoperative, and the remaining engine is producing takeoff power. The Federal Aviation Regulations under which the airplane was certificated, stipulate that at Vmc the certificating test pilot must be able to: (1) stop the turn which results when the critical engine is suddenly made inoperative within 20 degrees of the original heading, using maximum rudder deflection and a maximum of 5 degrees bank into the operative engine, and (2) after recovery, maintain the airplane in straight flight with not more than a 5 degree bank (wing lowered toward the operating engine). This does not mean that the airplane must be able to climb or even hold altitude. It only means that a heading can be maintained. The principle of Vmc is not at all mysterious. It is simply that at any airspeed less than Vmc, air flowing along the rudder is such that application of rudder forces cannot overcome the asymmetrical yawing forces caused by takeoff power on one engine and it powerless windmilling propeller on the other. The demonstration of Vmc is discussed in a later section of this handbook.
Many pilots erroneously believe that because a light-twin has two engines, it. will continue to perform at least half as well with only one of those engines operating. There is nothing in FAR Part 23, governing the certification of light-twins, which requires an airplane to maintain altitude while in the takeoff configuration and with one engine inoperative. In fact, many of the current light-twins are not required to do this with one engine inoperative in any configuration, even at. sea level. This is of major significance in the operations of light-twins certificated under Part -23. With regard to performance (but not controllability) in the takeoff or landing configuration, the light twin-engine airplane is, in concept, merely a single-engine airplane with its power divided into two individual units. The following discussion should help the pilot to eliminate any misconceptions of single-engine operation of light-twin airplanes.
When one engine fails on a light-twin, performance is not really halved, but is actually reduced by 80 percent or more. The performance loss is greater than 50 percent because an airplane's climb performance is a function of the thrust horsepower which is in excess of that required for level flight. When power is increased in both engines in level flight and the airspeed is held constant, the airplane will start climbing — the rate of climb depending on the power added (which is power in excess of that required for straight-and-level flight). When one engine fails. However, it not only loses power but the drag increases considerably because of asymmetric thrust and the operating engine must then carry the full burden alone. To do this, it must produce 75 percent or more of its rated power. This leaves very little excess power for climb performance.
As an example, an airplane which has an all-engine rate of climb of 1.860 FPM and a single engine rate of climb of 190 FPM would lose almost 90 percent of its climb performance when one engine fails.
Nonetheless. the light-twin does offer obvious safety advantages over the single-engine airplane (especially in the enroute phase) but only if the pilot fully understands the real options offered by that second engine in the takeoff and approach phase of flight.
It is essential then that the light-twin pilot take proficiency training periodically from a competent flight instructor.
In general, the operating and flight characteristics of modern light-twins with one engine inoperative are excellent. Them airplanes can be controlled and maneuvered safely as long as sufficient airspeed is maintained. However, to utilize the safety and performance characteristics effectively, the pilot must have a sound understanding of the single-engine performance and the limitations resulting from an unbalanced of power.
A pilot checking out for the first time in any multiengine airplane should practice and become thoroughly familiar with the control and performance problems which result from the failure of one engine during any flight condition. Practice in all the control operations and precautions is necessary and demonstration of these is required on multiengine rating flight tests. Practice should be continued as long as the pilot engages in flying a twin-engine airplane, so that corrective action will be instinctive and the ability to control airspeed, heading, and altitude will be retained.
The feathering of a propeller should be demonstrated and practiced in all airplanes equipped with propellers which can be feathered and unfeathered safely in flight. If the airplane used is not equipped with feathering propellers, or is equipped with propellers, which cannot be feathered and unfeathered safely in flight, one engine should be secured (shut down) in accordance with the procedures in the FAA approved Airplane Flight Manual or the Pilot's Operating Handbook. The recommended propeller setting should be used, and the emergency setting of all ignition. electrical, hydraulic, and fire extinguisher systems should be demonstrated.
When an engine fails in flight the movement of the airplane through the air tends to keep the propeller rotating, much like a windmill. Since the failed engine is no longer delivering power to the propeller to produce thrust but instead, may be absorbing energy to overcome friction and compression of the engine, the drag of the windmilling propeller is significant and causes the airplane to yaw toward the failed engine (Fig. 16-6). Most multiengine airplanes are equipped with "full-feathering propellers" to minimize that yawing tendency.
The blades of a feathering propeller may be positioned by the pilot to such a high angle that they are streamlined in the direction of flight. In this feathered position, the blades act as powerful brakes to assist engine friction and compression in stopping the windmilling rotation of the propeller. This is of particular advantage in case of a damaged engine, since further damage, caused by a windmilling propeller creates the least possible drag on the airplane and reduces the yawing tendency. As a result, multiengine airplanes are easier to control in flight when the propeller of an inoperative engine is feathered.
Feathering of propellers for training and checkout purposes should be performed only under such conditions and at such altitudes and locations that a safe landing on an established airport could be accomplished readily in the event of difficulty in unfeathering the propeller.
The following procedures are recommended to develop in the transitioning pilot the habit of using proper procedures and proficiency in coping with an inoperative engine.
At a safe altitude (minimum 3,000 feet above terrain) and within landing distance of a suitable airport, an engine may be shut down with the mixture control or fuel selector. At lower altitudes, however, shut down should be s imulated by reducing power by means of the throttle to the zero thrust setting. The following procedures should then be followed:
The pilot must be proficient in the control of heading, airspeed, and altitude, in the prompt identification of a power failure, and in the accuracy of shutdown and restart procedures as prescribed in the FAA approved Airplane Flight Manual or Pilot's Operating Handbook.
There is no better way to develop skill in single-engine emergencies than by continued practice. The fact that the techniques and procedures of single-engine operation are mastered thoroughly at one time during a pilot's career is no assurance of being able to cope successfully with an engine-out emergency unless review and practice are continued. Some engine-out emergencies may be so critical that there may be no safety margin for lack of skill or knowledge. Unfortunately, many light-twin pilots never practice single-engine operation after receiving their multiengine rating.
The pilot should practice and demonstrate the effects (on engine-out performance) of various configurations of gear, flaps, and both; the use of carburetor heat; and the failure to feather the propeller on an inoperative engine. Each configuration should be maintained, at best engine-out rate-of-climb speed long enough to determine its effect on the climb (or sink) achieved. Prolonged use of carburetor heat, if so equipped, at high power settings should be avoided.
"P-factor" is present in multiengine airplanes just as it is in single-engine airplanes. Remember, P-factor is caused by the dissimilar thrust of the rotating propeller blades when in certain flight conditions. It is the result of the downward moving blade having a greater angle of attack than the upward moving blade when the relative wind striking the blades is not aligned with the thrust line (as in a nose-high attitude).
In most U.S. designed light-twins, both engines rotate to the right (clockwise) when viewed from the rear, and both engines develop an equal amount of thrust. At low airspeed and high power conditions, the downward moving propeller blade of each engine develops more thrust than the upward moving blade. This asymmetric propeller thrust or "P-factor," results in a center of thrust at the right side of each engine as indicated by lines D1 and D2 in Fig. 16-7. The turning (or yawing) force of the right engine is greater than the left engine because the center of thrust (D2) is much farther away from the center line (CL) of the fuselage-it has a longer level arm. Thus, when the right engine is operative and the left engine is inoperative, the turning (or yawing) force is greater thin in the opposite situation of a "good" left engine and a "bad" right engine. In other words, directional control may be difficult when the left engine (the critical engine) is suddenly made inoperative.
It should be noted that some light-twin engine airplanes are equipped with engines turning in opposite directions; that is, the left engine and propeller turn clockwise and the right engine and propeller turn counterclockwise. With this arrangement, the thrust line of either engine is the same distance from the center line of the fuselage, so there will be no difference in yaw effect between loss of left or right engine.
Every light-twin engine airplane checkout should include a demonstration of the airplane's engine-out minimum control speed. The engine-out minimum control speed given in the FAA approved Airplane Flight 'Manual. Pilot's Operating Handbook, or other manufacturer's published limitations is determined during original airplane certification under conditions specified in the Federal Aviation Regulations. These conditions normally are not duplicated during pilot training or testing because, they consist of the most adverse situations for airplane type certification purposes. Prior to a pilot checkout, a thorough discussion of the factors affecting engine-out minimum control speed is essential.
Basically, when one engine fails the pilot must overcome the asymmetrical thrust (except on airplanes with center line thrust) created by the operating engine by setting up a counteracting moment with the rudder. When the rudder is fully deflected. its yawing power will depend on the velocity of airflow across the rudder-which in turn is dependent on the airspeed. As the airplane decelerates it will reach a speed below which the rudder moment will no longer balance the thrust moment and directional control will be lost.
During engine-out flight the large rudder deflection required to counteract the asymmetric thrust also results in a "lateral lift" force on the vertical fin. This lateral "lift" represents an unbalanced side force on the airplane which must be counteracted either by allowing the airplane to accelerate sideways until the lateral drag caused by the sideslip equals the rudder "lift" force or by banking into the operative engine and using a component of the airplane weight to counteract the rudder-induced side force.
In the first case, the wings will be level, the ball in the turn-and-slip indicator will be centered and the airplane will be in a moderate sideslip toward the inoperative engine. In the second case, the wings will be banked 3-5 degrees into the good engine, the ball will be deflected one diameter toward the operative engine, and the airplane will be at zero sideslip.
The sideslipping method has several major disadvantages: (1) the relative wind blowing on the inoperative engine side of the vertical fin tends to increase the asymmetric moment caused by the failure of one engine; (2) the resulting sideslip severely degrades stall characteristics; and (3) the greater rudder deflection required to balance the extra moment and the sideslip drag cause a significant reduction in climb and/or acceleration capability.
Flight tests have shown that holding the ball of the turn-and-slip indicator in the center while maintaining heading with wings level drastically increases Vmc as much as 20 knots in some airplanes. (Remember, the value of Vmc given in the FAA approved flight manual for the. airplane is based on a maximum 5 degree bank into the operative engine.) Banking into the operative engine reduces Vmc, whereas decreasing the bank angle away from the operative engine increases Vmc at the rate of approximately 3 knots per degree of bank angle.
Flight tests have also shown that the high drag caused by the wings level, ball centered configuration can reduce single-engine climb performance by as much as 300 FPM, which is just about all that is available at sea level in a non-turbocharged light twin.
Banking at least 5 degrees into the good engine ensures that the airplane will be controllable at any speed above the certificated Vmc, that the airplane will be in a minimum drag configuration for best climb performance, and that the stall characteristics will not be degraded. Engine-out flight with the ball centered is never correct.
The magnitude of these effects will vary from airplane to airplane, but the principles are applicable in all cases.
NOTE. A bank limitation of up to 5 degrees during demonstration is applicable only to certification tests of the airplane and is not intended as a limit in training or testing a pilot's ability to extract maximum performance from the airplane.
For an airplane with nonsupercharged engines, Vmc decreases as altitude is increased. Consequently, directional control can be maintained at a lower airspeed than at sea level. The reason for this is that, since power decreases with altitude the thrust, moment of the operating engine becomes less, thereby lessening the need for the rudder's yawing force. Since V., is a function of power (which decreases with altitude). it is possible for the airplane to reach a stall speed prior to loss of directional control.
It must be understood, therefore., that there is a certain density altitude above which the stalling speed is higher than the engine-out minimum control speed. When this density altitude exists close to the ground because of high elevations or temperatures, an effective flight demonstration is impossible and should not be attempted. When a flight demonstration is impossible, the check pilot should emphasize orally the significance of the engine-out minimum control speed, including the results of attempting flight below this speed with one engine inoperative, the recognition of the imminent loss of control, and the recovery techniques involved.
Vmc is greater when the center of gravity is at the rearmost allowable position. Since the airplane rotates around its center of gravity. the moments are measured using that point as a reference. A rearward CG would not affect the thrust moment, but would shorten the arm to the center of the rudder's horizontal "lift" which would mean that a higher force (airspeed) would be required to counteract the engine-out yaw. Figure 16-8 shows an exaggerated view of the effects of a rearward CG.
Generally, the center of gravity range of most light twins is short enough so that the effect on the Vmc is relatively small, but it is a factor that should be considered. Many pilots would only consider the rear CG of their light-twin as a factor for pitch stability, not realizing that it could affect the controllability with one engine out.
There are many light-twin pilots who think that the only control problem experienced in flight below Vmc is a yaw toward the inoperative engine. Unfortunately, this is not the whole story.
With full power applied to the operative engine, as the airspeed drops below Vmc, the airplane tends to roll as well as yaw into the inoperative engine. This tendency becomes greater as the airspeed is further reduced, since this tendency must be counteracted by aileron control, the yaw condition is aggravated by aileron yaw (the "down" aileron creates more drag than the "up" aileron). If a stall should occur in this condition, a violent roll into the dead engine may be experienced. Such an event occurring close to the ground could be disastrous. This may be avoided by maintaining airspeed above at all times during single-engine operation. If the airspeed should fall below Vmc for whatever reason then power must be reduced on the operative engine and the airplane must be banked at least 5 degrees toward the operative engine if the airplane is to be safely controlled.
The Vmc demonstrations should be performed at an altitude from which recovery from loss of control could be made safely. One demonstration should be made while holding the wings level and the ball centered, and another demonstration should be made while banking the airplane at least 5 degrees toward the operating engine to establish "zero sideslip." These maneuvers will demonstrate the engine-out minimum control speed for the existing conditions and will emphasize the necessity of banking into the operative engine. No attempt should be made to duplicate Vmc as determined for airplane certification.
After the propellers are set to high RPM, the landing gear is retracted, and the flaps are in the takeoff position, the airplane should be placed in a climb attitude and airspeed representative of that following a normal takeoff. With both engines developing as near rated takeoff power as possible, power on the critical engine (usually the left) should then be reduced to idle (windmilling, not shut down). After this is accomplished, the airspeed should be reduced slowly with the elevators until directional control no longer can be maintained. At this point, recovery should be initiated by simultaneously reducing power on the operating engine and reducing-the angle of attack by lowering the nose. Should indications of a stall occur prior to reaching this point, recovery should be initiated immediately by reducing the angle of attack. In this case, a minimum engine-out control speed demonstration is not possible under existing conditions.
If it is found that the minimum engine-out control speed is reached before indications of a stall are encountered, the pilot should demonstrate the ability to control the airplane and initiate a safe climb in the event of a power failure at the published engine-out minimum control speed.
The most critical time for an engine-out condition in a twin-engine airplane is during the two or three-second period immediately following the takeoff roll while the airplane is accelerating to a safe engine-failure speed.
Although most twin-engine airplanes are controllable at a speed close to the engine-out minimum control speed, the performance is often so far below optimum that continued flight, following takeoff may be marginal or impossible. A more suitable recommended speed, termed by some aircraft manufacturers as minimum safe single-engine speed, is that at which altitude can be maintained while the landing gear is being retracted and the propeller is being feathered.
Upon engine failure after reaching the safe single-engine speed on takeoff, the twin-engine pilot (having lost one-half of the normal power) usually has a significant advantage over the pilot of a single-engine airplane, because, if the particular airplane has single-engine climb capability at the existing gross weight and density altitude, there may be the choice of stopping or continuing the takeoff. This compares with the only choice facing a single-engine airplane pilot who suddenly has lost half of the normal takeoff power — that is stop!
If one engine fails prior to reaching Vmc, there is no choice but to close both throttles and bring the airplane to a stop. If engine failure occurs after becoming airborne, the pilot must decide immediately to land or to continue the takeoff.
If the decision is made to continue the takeoff, the airplane must be able to gain altitude with one engine inoperative. This requires acceleration to Vyse if no obstacles are involved, or to Vxse if obstacles are a factor.
To make a correct decision in an emergency of this type, the pilot must consider the runway length, field elevation, density altitude, obstruction height, headwind component, and the airplane's gross weight. (For simplification purposes, additional factors such as runway contaminants [rubber, soot, water, ice, snow] and runway slope will not be discussed here.) The flightpaths illustrated in Fig. 16-9 indicate that the "area of decision" is bounded by: (1) the point at which Vy is reached and (2) the point where the obstruction altitude is reached. An engine failure in this area demands an immediate decision. Beyond this decision area, the airplane, within the limitations of engine-out climb performance, can usually be maneuvered to a landing at the departure airport.
The "accelerate-stop distance" is the total distance required to accelerate the twin-engine airplane to a specified speed and, assuming failure of an engine at the instant that speed is attained, to bring the airplane to a stop on the remaining runway. The "accelerate-go distance" is the total distance required to accelerate the airplane to a specified speed and, assuming failure of an engine at the instant that speed is attained, continue takeoff on the remaining engine to a height of 50 feet.
For example, use the chart in Fig. 16-10 and assume that with a temperature of 80 degrees F., a calm wind at a pressure altitude of 2,000 feet, a gross weight of 4,800 pounds, and all engines operating, the airplane being flown requires 3,525 feet to accelerate to 105 MPH and then be brought to a stop. Assume also that the airplane under the same conditions requires a distance of 3,830 feet to take off and climb over a 50-foot obstacle (Fig. 16-11) when one engine fails at 105 MPH.
With such a slight margin of safety (305 feet) it would be better to discontinue the takeoff and stop if the runway is of adequate length, since any slight mismanagement of the engine-out, procedure would more than outweigh the small advantage offered by continuing the takeoff. At higher field elevations the advantage becomes less and less until at very high density altitudes a successful continuation of the takeoff is extremely improbable.
Competent pilots of light-twins will plan the takeoff in sufficient detail to be able to take immediate action if and-when one engine tails during the takeoff process. They will be thoroughly familiar with the airplane's performance capabilities and limitations, including accelerate-stop distance, as well as the distance available for takeoff, and will include such factors in their plan of action. For example, if it has been determined that the airplane cannot maintain altitude with one engine inoperative (considering the gross weight and density altitude), the seasoned pilot will be well aware that should an engine fail right after lift-off, an immediate landing may have to be made in the most suitable area available. The competent pilot will make no attempt to maintain altitude at the expense of a safe airspeed.
Consideration will also be given to surrounding terrain, obstructions., and nearby landing areas so that a definite direction of flight can be established immediately if an engine fails at, a critical point during the climb after takeoff. It is imperative then, that the takeoff and climb path be planned so that all obstacles between the point of takeoff and the available areas of landing can be cleared if one engine suddenly becomes inoperative.
In addition, a competent light-twin pilot knows that the twin-engine airplane must be flown with precision if maximum takeoff performance and safety are to be obtained. For example, the airplane must lift off at a specific airspeed, accelerate to a definite climbing airspeed, and climb with maximum permissible power on both engines to a safe single-engine maneuvering altitude. In the meantime, if an engine fails. a different airspeed must be attained immediately. This airspeed must be held precisely because only at this airspeed will the pilot be able to obtain maximum performance from the airplane. To understand the factors involved in proper takeoff planning, a, further explanation of this critical speed follows, beginning with the lift-off.
The light-twin can be controlled satisfactorily while firmly on the ground when one engine fails prior to reaching Vmc during the takeoff roll. This is possible by closing both throttles, by proper use of rudder and brakes, and with many airplanes by use of nosewheel steering. If the airplane is airborne at less than Vmc, however, and suddenly loses all power on one engine, it cannot be controlled satisfactarily. Thus, on normal takeoffs, lift-off should never take place until the airspeed reaches and exceeds Vmc. The FAA recommends a minimum speed of Vmc plus 5 knots before lift-off. From this point, an efficient climb procedure should be followed (Fig. 16-12).
An efficient climb procedure, is one in which the airplane leaves the ground slightly above Vmc, accelerates quickly to Vy (best rate-of-climb speed) and climbs at Vy. The climb at Vy should be made with both engines set to maximum takeoff power until reaching a safe single-engine maneuvering altitude (minimum of approximately 500' above field elevation or as dictated by airplane performance capability and/or local obstacles). At this point, power may be reduced to the allowable maximum continuous power setting (METO ï¿½ maximum except takeoff) or less, and any desired enroute climb speed then may be established. The following discussion explains why Vy is recommended for the initial climb.
To improperly trained pilots, the extremes in takeoff technique may suggest "hold it down" to accelerate the airplane to near cruise speed before climbing, or "pull it off" below Vmc and climb as steeply as possible. If one considers the possibility of an engine failure somewhere during the takeoff, neither of these procedures makes much sense for the following reasons: Remember, drag increases as the square of the speed; so for any increase in speed over and above the best rate-of-climb speed, Vy, the greater the drag and the less climb performance the airplane will have. At 123 knots the drag is approximately one and one-half times greater than it is at 100 knots. At 141 knots the drag is doubled, and at 200 knots the drag is approximately four times as great as at 100 knots. While the drag is increasing as the square of the velocity (V2), the power required to maintain a velocity increases as the cube of that velocity (V3).
In the event of engine failure, a pilot who uses excessive speed on takeoff will discover suddenly that all the energy produced by the engines has been converted into speed. Improperly trained pilots often believe that the excess speed can always be converted to altitude, but this theory is not valid. Available power is only wasted in accelerating the airplane to an unnecessary speed. Also, experience has shown that an unexpected engine failure so surprises the unseasoned pilot that proper reactions are extremely lagging. By the time the initial shock wears off and the pilot is ready to take control of the situation, the excess speed has dissipated and the airplane is still barely off the ground. From this low altitude, the pilot would still have to climb, with an engine inoperative, to whatever height is needed to clear all obstacles and get back to the approach end of the runway. Excess speed cannot be converted readily to the altitude or distance necessary to reach a landing area safely.
In contrast, however, an airplane will fly in level flight much easier than it will climb. Therefore, if the total energy of both engines is initially converted to enough height above the ground to permit clearance of all obstacles while in level flight (safe maneuvering altitude), the problem is much simpler in the event an engine fails. If some extra height is available, it usually can be traded for velocity or gliding distance when needed.
Simply stated then, altitude is more essential to safety after takeoff than is excess airspeed. On the other hand, trying to gain height too fast, in the takeoff also can be very dangerous because of control problems. If the airplane has just become airborne and the airspeed is at or below Vmc when an engine fails, the pilot could avoid a serious accident by retarding both throttles immediately. If this action is not taken immediately, the pilot will be unable to control the airplane.
Consequently, the pilot always should keep one hand on the control wheel (when not operating hand-controlled nose steering) and the other hand on the throttles throughout the takeoff roll. The airplane should remain on the ground until adequate speed is reached so that a smooth transition to the proper climb speed can be made. THE AIRPLANE SHOULD NEVER LEAVE THE GROUND BEFORE Vmc IS REACHED. Preferably, Vmc + 5 knots should be attained.
If an engine fails before leaving the ground it is advisable to discontinue the takeoff and STOP. If an engine fails after lift-off, the pilot will have to decide immediately whether to continue flight, or to close both throttles and land. However, waiting until the engine failure occurs is not the time for the pilot to plan the correct action. The action must be planned before the airplane is taxied onto the runway. The plan of action must consider the density altitude, length of the runway, weight of the airplane, and the airplane's accelerate-stop distance, and accelerate-go distance under these conditions. Only on the basis of these factors can the pilot decide intelligently what course to follow if an engine should fail. When the flight crew consists of two pilots, it is recommended that the pilot in command brief the second pilot on what course of action will be taken should the need arise.
To reach a safe single-engine maneuvering altitude as safely and quickly as possible, the climb with all engines operating -must be made at the proper airspeed. That speed should provide for:
To make a quick and easy transition to the single-engine best rate-of-climb speed, in case an engine fails, the pilot should climb at some speed greater than Vyse. If an engine fails at less than Vyse, it would be necessary for the pilot to lower the nose to increase the speed to Vyse in order to obtain the best climb performance. If the airspeed is considerably less than this speed, it might be necessary to lose valuable altitude to increase the speed to Vyse. Another factor to consider is the loss of airspeed that may occur because of erratic pilot technique after a sudden, unexpected power loss. Consequently, the normal initial two-engine climb speed should not be less than Vy.
In summary then, the initial climb speed for a normal takeoff with both engines operating should permit the attainment of a safe single-engine maneuvering altitude as quickly as possible; it should provide for good control capabilities in the event of a sudden power loss on one engine; and it should be a speed sufficiently above Vyse to permit attainment of that speed quickly and easily in the event power is suddenly lost on one engine. The only speed that meets all of these requirements for a normal takeoff is the best rate-of-climb speed with both engines operating (Vy).
After runup and pretakeoff checks have been completed, the airplane should be taxied into takeoff position and aligned with the runway. If it is a tailwheel-type, the tailwheel lock (if installed) should be engaged only after the airplane has been allowed to roll straight a few feet along the intended takeoff path to center the tailwheel.
If the crew consists of two pilots, it is recommended that the pilot in command brief the other pilot on takeoff procedures prior to receiving clearance for takeoff. This briefing consists of at least the following: minimum control speed (Vmc), rotation speed (Vr), liftoff speed (Vlof), single-engine best rate-of-climb speed (Vyse), all engine best rate-of -climb speed (Vy), and what procedures will be followed if an engine failure occurs prior to Vmc (Fig. 16-12).
Both throttles then should be advanced simultaneously to takeoff power, and directional control maintained by the use of the steerable nosewheel and the rudder. Brakes should be used for directional control only during the initial portion of the takeoff roll when the rudder and steerable nosewheel are ineffective. During the initial takeoff roll it is advisable to monitor the engine instruments.
As the takeoff progresses, flight controls are used as necessary to compensate for wind conditions. Lift-off should be made at, no less than Vmc + 5. After lift-off, the airplane should be allowed to accelerate to the all-engine best rate-of-climb speed Vy, and then the climb maintained at this speed with takeoff power until a safe maneuvering altitude is attained.
The landing gear may be raised as soon as practicable but not before reaching the point from which a safe landing can no longer be made on the remaining portion of the runway. The flaps (if used) should be retracted as directed in the airplane's operating manual.
Upon reaching safe maneuvering altitude, the airplane should be, allowed to accelerate to cruise climb speed before power is reduced to normal climb power.
If it is necessary to take off over an obstacle or from a critically short field, the procedures should be altered slightly. For example, the initial climb speed that should provide the best angle of climb for obstacle clearance is Vx rather than Vy. However, Vx in some light twins is below Vmc. In this case, if the climb were made at Vx and a sudden power failure occurred on one engine, the pilot would not be able to control the airplane unless power were reduced on the operating engine. This would create an impossible situation because it would not be likely that the airplane could clear an obstacle with one engine inoperative and the other at some reduced power setting. In any case, if an engine fails and the climb is to be continued over an obstacle, Vxse must be established if maximum performance is to be obtained.
Generally, the short field or obstacle clearance takeoff will be much the same as a normal takeoff using the manufacturer's recommended flap settings, power settings, and speeds. However, if the published best angle-of-climb speed (Vx) is less than Vmc + 5, then it is recommended that no less than Vmc + 5 be used.
During the takeoff roll as the airspeed reaches the best angle-of-climb speed, or Vmc + 5, whichever is higher, the airplane should be rotated to establish an angle of attack that will cause the airplane to lift off and climb at that specified speed. At an altitude of approximately 50 feet or after clearing the obstacle, the pitch attitude can be lowered gradually to allow the airspeed to increase to the all engine best rate-of-climb speed. Upon reaching safe maneuvering altitude, the airplane should be allowed to accelerate to normal or enroute climb speed and the power controls reduced to the normal climb power settings.
If an engine should fail during the takeoff roll before becoming airborne, it is advisable to close both throttles immediately and bring the airplane to a stop. The same procedure is recommended if after becoming airborne an engine should fail prior to having reached the single-engine best rate-of-climb speed (Vyse). An immediate landing is usually inevitable because of the altitude loss required -to increase the speed to Vyse.
The pilot must have determined before takeoff what altitude, airspeed, and airplane configuration must exist to permit the flight to continue in event of an engine failure— the pilot also should be ready to accept the fact that if engine failure occurs before these required factors are established, both throttles must be closed and the situation treated the same as engine failure on a single-engine airplane. If it his been predetermined that the engine-out rate of climb under existing circumstances will be at least 50 feet per minute at 1,000 feet above the airport, and that at least the engine-out best angle-of-climb speed has been attained, the pilot may decide to continue the takeoff.
If the airspeed is below the engine-out best angle-of-climb speed (Vxse) and the landing gear has not been retracted, the takeoff should be abandoned immediately.'
If the engine-out best angle-of-climb speed (Vxse) has been obtained and the landing gear is in the retract cycle, the pilot should climb at the engine-out best angle-of-climb speed (Vxse) to clear any obstructions, and thereafter stabilize the airspeed at the engine-out best rate-of-climb speed (Vyse) while retracting the landing gear and flaps and resetting all appropriate systems.
When the decision is made to continue flight, the single-engine best rate-of-climb speed should be attained and maintained (Fig. 16-13). Even if altitude cannot be maintained, it is best to continue to hold that speed because it would result in the slowest rate of descent, and provide the most time for executing the emergency landing. After the decision is made to continue flight and a positive rate of climb is attained, the landing gear should be retracted as soon as practical.
If the airplane is just barely able to maintain altitude and airspeed, a turn requiring a bank greater than approximately 15 degrees should not be attempted. When such a turn is made under these conditions, both lift, and airspeed will decrease. Consequently, it is advisable to continue straight, ahead whenever possible, until reaching a safe maneuvering altitude. At that time a steeper bank may be made safely-and in either direction. There is nothing wrong with banking toward a "dead" engine if a safe speed and zero sideslip are maintained.
When an engine fails after becoming airborne, the pilot should bold heading with rudder and simultaneously roll into a bank of at least 5 degrees toward the operating engine. In this attitude the airplane will tend to turn toward the operating engine, but at the same time, the asymmetrical power resulting from the engine failure will tend to turn the airplane toward the "dead" engine. The result is a partial balance of those tendencies and provides for an increase in airplane performance as well as easier directional control.
NOTE: In this situation the ball in the turn-and-bank indicator will be approximately one ball width off center toward the good engine.
The best way to identify the inoperative engine is to note the direction of yaw and the rudder pressure required to maintain heading. To counteract the asymmetrical thrust, extra rudder pressure will have to be exerted on the operating engine side. To aid in identifying the failed engine, some pilots use the expressions "Best Foot Forward," or "Dead Foot Dead Engine." Never rely on tachometer or manifold pressure readings to determine which engine has failed. After power has been lost on an engine, the tachometer will often indicate the correct r.p.m. and the manifold pressure gauge will indicate the approximate atmospheric pressure or above.
Experience has shown that the biggest problem is not in identifying the inoperative engine, but rather in the pilot's actions after the inoperative engine has been identified. In other words, a pilot may identify the "dead" engine and then attempt to shut down the wrong one — resulting in no power at all. To avoid this mistake, the pilot should verify that the dead engine has been identified by retarding the throttle of the suspected engine before shutting it down.
When demonstrating or practicing procedures for engine failure on takeoff, the feathering of the propeller and securing of the engine should be simulated rather than actually performed, so that the engine may be available for immediate use if needed; but all other settings should be made just as in an actual power failure.
In all cases, the airplane manufacturer's recommended procedure for single-engine operation should be followed. The general procedure listed below is not intended to replace or conflict with any procedure established by the manufacturer of any airplane. It can be used effectively for general training purposes and to emphasize the importance of Vyse. It should be noted that this procedure is concerned with an engine failure on a takeoff where obstacle clearance is not critical. If the decision is made to continue flight after an engine failure during the takeoff climb, the pilot should maintain directional control at all times and:
Normally, when an engine failure occurs while enroute in cruising flight, the situation is not as critical as when an engine fails on takeoff. With the more leisurely circumstances, the pilot should take time to determine the cause of the failure and to correct the condition, if possible. If the condition cannot be corrected, the single-engine procedure recommended by the manufacturer should be accomplished and a landing made as soon as practical.
A primary error during engine failure is the pilot's tendency to perform the engine-out identification and shutdown too quickly, resulting in improper identification or incorrect shutdown procedures. The element of surprise generally associated with actual engine failure may result in confused and hasty reactions.
When an engine fails during cruising flight, the pilot's main problem is to maintain sufficient altitude to be able to continue flight to the point of intended landing. This is dependent on the density altitude, gross weight of the airplane, and elevation of the terrain and obstructions. When the airplane is above its single-engine service ceiling, altitude will be lost. The single-engine service ceiling is the maximum density altitude at which the single-engine best rate-of-climb speed will produce 50 FPM rate of climb. This ceiling is determined by the manufacturer on the basis of the airplane's maximum gross weight, flaps and landing gear retracted, the critical engine inoperative, and the propeller feathered.
Although engine failure while enroute in normal cruise conditions may not be critical, it is a recommended practice to add maximum permissible power to the operating engine before securing or shutting down the failed engine. If it is determined later that maximum permissible power on the operating engine is not needed to maintain altitude. it is a simple matter to reduce the power. Conversely, if maximum permissible power is not applied, the airspeed may decrease much farther and more rapidly than expected. This condition could present a serious performance problem, especially if the airspeed should drop below Vyse.
The altitude should be maintained if it is within the capability of the airplane. In an airplane not capable of maintaining altitude with an engine inoperative under existing circumstances, the airspeed should be maintained within ï¿½5 knots of the engine-out best rate-of-climb speed (Vyse) so as to conserve altitude as long as possible to reach a suitable landing area.
After the landing gear and flaps are retracted and the failed engine is shut down and everything is under control (including heading and altitude), it is recommended that the pilot communicate with the nearest ground facility to let them know the flight is being conducted with one engine inoperative. FAA facilities are able to give valuable assistance if needed, particularly when the flight is conducted under IFR or a landing is to be made at a tower-controlled airport. Good judgment would dictate, of course, that a landing be made at the nearest suitable airport as soon as practical rather than continuing flight.
During engine-out practice using zero thrust power settings, the engine may cool to temperatures considerably below the normal operating range. This factor requires caution when advancing the power at the termination of single-engine practice. If the power is advanced rapidly, the engine may not respond and an actual engine failure may be encountered. This is particularly important when practicing engine-out approaches and landings. A good procedure is to slowly advance the throttle to approximately one-half power, then allow it to respond and stabilize before advancing to higher power settings. This procedure also results in less wear on the engines of the training aircraft.
Restarts after feathering require, the same amount of care, primarily to avoid engine damage. Following the restart. the engine power should be maintained at the idle setting or slightly above until the engine is sufficiently warm and is receiving adequate lubrication.
Although each make and model of airplane must be operated in accordance with the manufacturer's instructions, the following typical checklist is presented to familiarize the transitioning pilot with the actions that may be required when an engine fails.
ENGINE FAILURE DURING FLIGHT
AIRSTART (After Shutdown)
Airplanes Without Propeller Unfeathering System:
Airplanes With Propeller Unfeathering System:
Essentially, an engine-out approach and landing is the same as a normal approach and landing. Long, flat approaches with high power output on the operating engine and/or excessive threshold speed that results in floating and unnecessary runway use should be avoided. Due to variations in the performance, limitations, etc., of many light twins, no specific flightpath or procedure can be proposed that would be adequate in all engine-out approaches. In most light twins, however, a single-engine approach can be accomplished with the flightpath and procedures almost identical to a normal approach and landing (Fig. 16-14). The light-twin manufacturers include a recommended single-engine landing procedure in the airplane's operating manual.
During the checkout, the transitioning pilot should perform approaches and landings with the power of one engine set to simulate the drag of a feathered propeller (zero thrust), or if feathering propellers are not installed, the throttle of the simulated failed engine set to idling. With the "dead" engine feathered or set to "zero thrust," normal drag is considerably reduced, resulting in a longer landing roll. Allowances should be made accordingly for the final approach and landing.
The final approach speed should not be less than Vyse until the landing is assured; thereafter, it should be at the speed commensurate with 'the flap position until beginning the roundout for landing. Under normal conditions the approach should be made with full flaps; however, neither full flaps nor the landing gear should be extended until the landing is assured. With full flaps the approach speed should be 1.3 Vso or as recommended by the manufacturer.
The pilot should be particularly judicious in lowering the flaps. Once they have been extended it may not be possible to retract them in time to initiate a go-around. Most of the light twins are not capable of making a single-engine go-around with full flaps.
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