what performance should a pilot of a light, twin-engine airplane be able to maintain at vmc

Introduction

A take a chance unique to operating a multi-engine airplane is a loss of directional control following an engine failure or precautionary shutdown. Merely such an is preventable through proper training that teaches the airplane pilot to recognize the onset of a loss of directional command and apply the corrective deportment. When equipped with this cognition and skill, a pilot may see that the benefits of having a second engine outweigh the risks.

Objectives

Subsequently this lesson, the learner will exist able to:

• Define V_MC and draw how it is determined during the aircraft certification process.
• Describe situations that may outcome in a loss of directional control with one engine inoperative (OEI).
• Differentiate between the operating techniques for best climb performance (zero sideslip) and maximum directional control.
• Recognize the onset of a loss of directional control and recover properly.

Educational activity Strategy

Although "sit-in" is included in the title, this procedure must exist good to proficiently before a practical examination.

Outline

My CFI Book Content

1. What is a V_MC Demonstration?
   1. Sideslip During the Five_MC Demonstration
2. Definition of V_MC
3. How the Manufacturer Determines V_MC
4. Control and Operation Later on an Engine Failure
   1. Directional Control
   2. Climb Performance
5. 4 Factors that Make the Left Engine Disquisitional
   1. Asymmetrical Thrust (Yaw)
   2. Accelerated Slipstream (Roll and Pitch)
   3. Spiraling Slipstream (Yaw)
   4. Torque (Roll)
6. Critical Density Altitude
7. How to Perform a V_MC Demonstration
   1. Setup
   2. Performance Steps
   3. Recovery
8. Safety Considerations for V_MC Demonstrations
9. Common Errors During V_MC Demonstrations

Aircraft Specific Training

• A review of airspeeds, to include V_MC (red line), Five_YSE (bluish line), and V_SSE (safe single-engine speed)
• Proper recovery procedures specified by the manufacturer
• Immediate activity items contained in the AFM/POH

Run a risk Management

• Failure to maintain directional control with one engine inoperative
• Collision avoidance, visual scanning, obstacle and wire strike avoidance
• Distractions, loss of situational awareness, and improper job management
• Low-altitude maneuvering

Scenario

You lot take rented a multi-engine airplane to practice takeoffs and landings and to maintain your passenger currency requirements. During preflight planning, y'all make up one's mind that single-engine climb performance will be adequate given the light operating weight and low-density altitude.

On climb out following a terminate-and-go landing, the right engine sputters then completely loses power. You immediately add together right rudder force per unit area and pitch upwardly to maintain directional command and to assistance clear a group of trees across the departure cease of the rails. The rudder pedal chop-chop reaches its travel limits. Now yous take cleared the trees, merely the aeroplane begins to scroll to the left.

Describe how you will respond to this issue and how you will configure the aircraft to maintain directional control and optimal climb operation.

Resources

• FAA-H-8083-iii: Aeroplane Flying Handbook:
  • Chapter 13: Transition to Multi-Engine Airplanes

Schedule

1. Lesson Briefing (0:30)
2. Instructor Demonstrations (0:10)
3. Learner Practice (0:20)
4. Lesson Debriefing (0:ten)

Equipment

• Whiteboard, markers, and erasers
• Aeroplane models
• Airplane checklist
• Headsets and flight gear

Completion Standards

This lesson is consummate when:

• All of the learner's questions are resolved.
• The lesson objectives are met.
• The bulk of the material and the primal points are retained.

My CFI Book Content

What is a Five_MC Sit-in?

A V_MC sit-in closely resembles how manufacturers determine V_MC during the airplane's certification process:

1. Power on the critical engine is reduced to idle.
2. The airplane is configured co-ordinate to the V_MC certification criteria.
3. The pitch mental attitude is increased to reduce airspeed gradually until a loss of control occurs.
4. Proper recovery procedures are performed to reestablish controllable, single-engine flight.

Sideslip During the V_MC Demonstration

During the Five_MC demonstration, the pilot applies rudder pressure to maintain directional control until full rudder is applied. The loss of control occurs under atmospheric condition of sideslip. V_MC is not determined under atmospheric condition of zip-sideslip during aircraft certification; therefore, it is not role of a V_MC demonstration.

A nil-skid may be established subsequently the initial V_MC recovery procedure is completed. Pilot certification standards require the airplane pilot to accelerate to V_XSE or V_YSE as appropriate during the recovery, which is usually maintained in a naught-sideslip condition for best climb performance.

Definition of V_MC

V_MC is the calibrated airspeed at which, following the sudden critical loss of thrust, it is possible to maintain control of the plane. For multi-engine airplanes, Five_MC must exist determined, if applicable, for the nigh critical configurations used in takeoff and landing operations.

Directional control has been lost when full rudder deflection is applied towards the operating engine, and the shipping begins to yaw toward the inoperative engine.

How the Manufacturer Determines V_MC

14 CFR Part 23 requires airplane manufacturers to decide 5_MC, if applicable, for the most critical configurations used in takeoff and landing operations. Specific configurations are not addressed; however, the following are typically the most critical.

Standard Day Conditions at Sea Level

An aeroplane must meet performance requirements for certification in still air and standard atmospheric atmospheric condition at sea level. This is necessary to plant a standard of measurement.

Most Unfavorable Weight (Light)

A heavier plane has a lower Five_MC due to the horizontal component of elevator and inertia.

For a given bank angle, an increase in weight will require more elevator to maintain altitude. The increment in the horizontal component of lift will require less rudder force per unit area to go on the aircraft from yawing.

A heavily loaded airplane has more inertia than a lightly loaded one; thus, a heavier airplane will accept a college resistance to yawing.

Nigh Unfavorable CG Location (Aft)

The aft-most CG limit is the most unfavorable CG position. As the CG moves aft, the rudder's moment arm is shortened, producing less leverage for the rudder. This will cause the rudder to have less authority in overcoming yawing forces, causing Five_MC to increase. At the same time, the moment arm of the propeller blade is increased, aggravating asymmetrical thrust.

Critical Engine Windmilling (Propeller Controls in the Takeoff Position)

5_MC increases every bit drag increases on the inoperative engine. A windmilling propeller creates more elevate than a stationary propeller. When the propeller is stationary, an unfeathered position creates more drag than a feathered propeller. Therefore, V_MC is highest when the critical engine's propeller is windmilling at the low pitch, loftier RPM blade angle.

Propeller Drag Profiles

Flaps, Gear, and Trim in the Takeoff Position with the Airplane out of Ground Event

• Extending the flaps increases the elevate behind the operative engine. This can accept a stabilizing effect that may reduce V_MC.
• 5_MC increases when the landing gear is retracted. Extended landing gear creates a keel effect that aids directional stability, which tends to decrease 5_MC.
• Since the airplane is normally trimmed to a neutral position on takeoff, having the plane pre-trimmed as an assist to an engine failure would exist "cheating".

• Basis effect decreases drag and increases 5_MC.

Upward to 5° (Not More than) of Depository financial institution Towards the Operating Engine

V_MC is highly dependent on bank bending. In a bank, the horizontal component of elevator helps the rudder counteract the operative engine's thrust. Historically, xiv CFR Part 23 prevented airplane manufacturers from using more than v° of banking concern toward the operative engine when determining V_MC.

When banking towards the operating engine, V_MC decreases by approximately iii knots for every degree of banking company less than v°. Cyberbanking away from the operating engine increases V_MC.

Note: A v° bank does not inherently establish zero-sideslip or give the best single-engine climb performance. Zero-sideslip occurs at banking concern angles less than v°. The determination of VMC in certification is solely concerned with the minimum speed for directional command under a specific set of circumstances.

Maximum Available Takeoff Power Initially on Each Engine (Engine Failure Should Happen Suddenly)

A college power imbalance results in more asymmetrical thrust. 5_MC increases as power is increased on the operating engine.

Control and Performance Later on an Engine Failure

Directional Control

When a multi-engine aircraft experiences an engine failure and the engines are non mounted on the longitudinal centrality, at that place are unbalanced forces and turning moments about the CG.

Pitch Down: The loss of induced airflow over the horizontal stabilizer results in less negative lift produced past the tail. Additional dorsum-force per unit area is required to maintain level flying.

Scroll Toward the Inoperative Engine: The loss of the accelerated slipstream air over the wing of the inoperative engine results in a reduction of lift on that wing. Therefore, the aircraft tends to roll towards the inoperative engine due to asymmetrical lift. This requires additional aileron pressure level into the operative engine.

Yaw: Asymmetrical thrust requires rudder pressure toward the operating engine.

Climb Operation

The loss of i engine results in a 50% loss of power, but an approximate 80% loss of climb performance. This performance decrease tin can exist seen past comparison the climb operation charts for 1 engine operating and two engines operating under the same atmospheric conditions.

Four Factors that Brand the Left Engine Critical

Notation: The following factors use to a conventional twin-engine airplane with both propellers turning clockwise when viewed from the cockpit.

Asymmetrical Thrust (Yaw)

Each engine's descending propeller blade will produce greater thrust than the ascending blade when the airplane is operated nether power and at positive angles of assault.

Even though both propellers produce the same corporeality of thrust, the descending bract on the right engine has a longer moment arm or greater leverage than the left engine'south descending blade. As a result, the left engine'south failure will event in the nigh asymmetrical thrust (adverse yaw) every bit the correct engine will be providing the remaining thrust.

Accelerated Slipstream (Roll and Pitch)

Asymmetrical thrust (P-Factor) results in a longer moment arm to the eye of thrust of the right engine than to the left engine. Therefore, the centerline of lift is further out on the correct fly, resulting in a greater rolling trend with a loss of the left engine. The left engine's failure also results in a more pregnant downward pitching moment due to the greater loss of negative lift produced by the tail.

Note: With both engines operating, 18% to 30% of total lift is generated from the accelerated slipstream.

Spiraling Slipstream (Yaw)

A spiraling slipstream of air from the left engine strikes the vertical stabilizer from the left. This helps counteract the yaw acquired by a failure of the correct engine. The right engine's slipstream does not striking the vertical stabilizer. If the left engine fails, the right engine's slipstream will not counteract the yaw toward the inoperative engine.

Torque (Roll)

For every action, there is an equal and contrary reaction. A propeller that rotates clockwise (right) volition tend to roll the shipping counter-clockwise (left). The airplane will tend to roll towards the inoperative engine regardless of which engine is failed.

On a multi-engine airplane with clockwise rotating propellers, the event of torque during OEI flight volition:

• Increase the tendency of the airplane to gyre towards the inoperative engine (left engine failed); or
• Counteract the tendency of the airplane to coil towards the inoperative engine (right engine failed).

Critical Density Altitude

With normally aspirated engines, an increase in altitude or temperature results in reduced engine performance and besides propeller efficiency. This results in a lower minimum command speed (Five_MC) as altitude is increased. However, the calibrated stall speed (Five_South) does not decrease with distance.

At that place exists an altitude where each of the following exists:

• V_MC is less than 5_{Due south} (stall occurs start)
• V_MC is the same as 5_{Due south} (stall and yaw coincide>)
• Five_MC is greater than V_Southward (yaw occurs first)

The density distance where V_MC and V_{Due south} are equal is called the disquisitional density distance. At this altitude, the airplane will "stall and yaw" at the same fourth dimension. Flight at this airspeed tin exist unsafe when operating with ane engine at full ability with the other engine failed or at idle power. The airplane could experience an abrupt change in attitude or enter into a spin.

How to Perform a V_MC Sit-in

Note: If a VMC demonstration cannot be accomplished under existing weather of density altitude, information technology may, for training purposes, be washed by blocking the rudder.

Setup

• Clear the area
• Heading established and noted
• Altitude established:
  • No lower than 3,000′ AGL
• Position most a suitable emergency landing area
• Set power and aircraft configuration:
  • Adjust the mixture controls as required
  • Set up the propeller controls full forwards
  • Retract the landing gear
  • Set the flaps to the normal takeoff setting
  • Set the trim for takeoff and practise non readjust it during the maneuver
  • Ready the cowl flaps for takeoff
  • Establish a normal cruise speed

Performance Steps

1. Simulate a failed engine past retarding the throttle lever of the critical engine to idle.
2. Ho-hum the airplane to x knots to a higher place Five_SSE or V_YSE, as appropriate, or the manufacturer's recommended speed.
3. Apply total power on the operative engine while maintaining heading.
4. Banking concern the aircraft up to 5° towards the side of the operative engine and sustain one/2 ball deflection toward the operative engine.
5. Increment the pitch mental attitude slowly to decrease airspeed past one knot per 2nd. A fast reduction of airspeed would non provide an adequate sit-in or allow the procedure to exist performed with consistency.
6. Aileron control deflection should exist increased as necessary to keep the bank angle abiding as the ailerons get less effective as airspeed decreases.
7. Maintain heading as long as possible by increasing rudder input.
8. Recognize, announce, and recover at the first sign of a loss of directional control, stall alert, or buffet, whichever occurs first.

Recovery

1. Promptly and simultaneously reduce power sufficiently on the operating engine and decrease the AOA as necessary to regain airspeed and directional control. To maintain directional command as the throttle is reduced, rudder pressure will need to exist reduced.
2. Once above V_MC and control is regained, smoothly accelerate the throttle on the operative engine to full ability. Simultaneously reapply rudder force per unit area every bit needed.
3. Accelerate to Five_XSE or 5_YSE as appropriate. Do not use the failed engine (fake).
4. Recover to the original heading.

After the single-engine recovery is demonstrated:

1. Return to prowl speed with both engines, trimming as necessary.
2. Complete the cruise checklist.

Safety Considerations for Five_MC Demonstrations

• Airplanes with normally aspirated engines will lose ability as altitude increases because of the reduced density of the air inbound the induction system of the engine. This loss of power volition result in a Five_MC lower than the stall speed at higher altitudes. Therefore, recovery should be made at the first indication of loss of directional command, stall warning, or buffet.
• Practise not perform this maneuver by increasing the pitch attitude to a high angle with both engines operating and then reducing ability on the critical engine. This technique is hazardous and may result in loss of plane control.
• Instructors should besides exist alarm for any sign of an impending stall. A learner may exist focused on the maneuver'south directional command attribute to the extent that impending stall indications go unnoticed.

Common Errors During V_MC Demonstrations

• Inadequate knowledge of the causes of loss of directional command at airspeeds less than V_MC, factors affecting V_MC, and safe recovery procedures
• Improper entry procedures, including pitch attitude, bank mental attitude, and airspeed
• Failure to recognize an imminent loss of directional control
• Initiating recovery steps also early
• Failure to utilise proper recovery procedures

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Source: https://mycfibook.com/lesson-plans/vmc-demonstration/

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