Study guide
20.2 Multiengine Knowledge: VMC, VYSE, and Engine-Out Fundamentals
FAA Private Pilot — Airplane PAR
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1 Introduction & Exam Overview
1.1 Current Exam Facts 1.2 ACS Codes, the AKTR, and How to Use This Guide
2 Pilot Qualifications & Medicals
2.1 Eligibility, Training, and Knowledge-Test Authorization 2.2 Private Pilot Privileges and Limitations 2.3 Medical Certificates, Duration, and Disqualification 2.4 BasicMed (14 CFR 61.113(i) and Part 68)
3 Airworthiness, Documents & Currency
3.1 Required Pilot and Aircraft Documents 3.2 Inspections, Airworthiness Directives, and Preventive Maintenance 3.3 Inoperative Equipment and 91.213 3.4 Recent Flight Experience and the Flight Review
4 14 CFR Part 91 Operating Rules
4.1 Right-of-Way, Minimum Safe Altitudes, and Speed Limits 4.2 VFR Cruising Altitudes, Altimeter Settings, and Oxygen 4.3 Fuel Requirements, Transponder, ADS-B, and ELT 4.4 NOTAMs, TFRs, and Accident/Incident Duties
5 National Airspace System
5.1 Class A, B, and C Airspace 5.2 Class D, E, and G Airspace and VFR Weather Minimums 5.3 Special Use Airspace 5.4 Other Airspace, TFRs, TRSA, ADIZ, and SFRA
6 Aviation Weather Theory
6.1 Atmosphere, Pressure, Temperature, and Density 6.2 Stability, Clouds, and Moisture 6.3 Air Masses and Fronts 6.4 Wind, Jet Stream, and Local Wind Systems
7 Weather Hazards
7.1 Thunderstorms and Convective Weather 7.2 Structural Icing, Frost, and Carburetor Ice 7.3 Fog, Low Ceilings, and Visibility 7.4 Wind Shear, Microbursts, Turbulence, and Mountain Waves
8 Weather Products & Briefings
8.1 METAR Decoding 8.2 TAF and Graphical Forecast Products 8.3 PIREPs, AIRMET, SIGMET, Convective SIGMET, and Winds Aloft 8.4 Briefings and Go/No-Go Decisions
9 Principles of Flight
9.1 Four Forces and Lift Production 9.2 Angle of Attack, Critical AoA, and Stalls 9.3 Drag, L/D, and Ground Effect 9.4 Axes, Stability, and Flight Controls
10 Maneuvering Flight, Stalls & Spins
10.1 Load Factor, Bank Angle, and Stall Speed 10.2 Left-Turning Tendencies 10.3 Slow Flight, Power-On/Off Stalls, and Spin Awareness 10.4 Steep Turns and Ground-Reference Maneuvers
11 Powerplant, Fuel & Electrical Systems
11.1 Reciprocating Engines, Mixture, Detonation, and Preignition 11.2 Ignition, Magnetos, Carburetor vs Fuel Injection 11.3 Fuel Grades, Contamination, and Fuel-System Management 11.4 Electrical System and Alternator Failure
12 Flight Instruments & Avionics
12.1 Pitot-Static Instruments and Blockage Errors 12.2 Gyroscopic Instruments, Vacuum Failure, and Magnetic Compass Errors 12.3 Engine Instruments, Transponder Modes, and Basic Avionics
13 Aircraft Performance
13.1 Pressure Altitude, Density Altitude, and Performance Effects 13.2 Takeoff and Climb Performance 13.3 Cruise, Descent, and Landing Performance 13.4 Wind, Gradient, Surface, and Crosswind Component
14 Weight and Balance
14.1 Weight-and-Balance Principles 14.2 Moment, CG, and Sample Computations 14.3 Forward and Aft CG Effects 14.4 V-Speeds, Markings, and Limitation Placards
15 Charts, Pilotage & Dead Reckoning
15.1 Sectional Chart Symbology and Airspace Depiction 15.2 Pilotage and Dead Reckoning 15.3 Variation, Deviation, Wind Triangle, and E6B 15.4 VFR Cross-Country and Fuel Planning
16 Radio Navigation, Lost Procedures & Airport Operations
16.1 VOR Navigation 16.2 GPS, RAIM, and Radar Services 16.3 Lost Procedures and Diversion 16.4 Communications, Light-Gun Signals, Lighting, and Traffic Patterns
17 Aeromedical Factors
17.1 Hypoxia, Hyperventilation, and Carbon Monoxide 17.2 Spatial Disorientation, Illusions, and Vision 17.3 Scuba-to-Flight, Alcohol/Drugs, and IMSAFE
18 ADM, Night Operations & Emergencies
18.1 ADM, Hazardous Attitudes, PAVE, and DECIDE 18.2 Night Operations and Night Illusions 18.3 Emergency Descent, Engine Failure, and System Malfunctions 18.4 Survival Gear, ELT, and Forced-Landing Considerations
19 Preflight Procedures & Airport Ground Operations
19.1 Preflight Assessment, Airworthiness Determination, and the Preflight Inspection 19.2 Flight Deck Management, Passenger Briefings, and Engine Starting 19.3 Taxi Operations: Signs, Markings, Lighting, and Runway Incursion Avoidance 19.4 Before-Takeoff Check, After-Landing, and Securing the Airplane
20 Class-Specific Knowledge: Seaplane & Multiengine
20.1 Seaplane and Water Operations Knowledge 20.2 Multiengine Knowledge: VMC, VYSE, and Engine-Out Fundamentals
20.2 Multiengine Knowledge: VMC, VYSE, and Engine-Out Fundamentals
Key Takeaways Explain This Topic AI
On a multiengine airspeed indicator, the RED radial line is VMC (minimum control speed with the critical engine inoperative) and the BLUE radial line is VYSE (best single-engine rate of climb).
On a conventional twin with both propellers turning clockwise, the LEFT engine is critical, because P-factor puts the right engine’s thrust on a longer moment arm about the CG.
VMC decreases with increasing density altitude in normally aspirated twins, so at altitude the airplane may stall before it reaches VMC — a stall with asymmetric thrust can become a spin.
Zero sideslip is achieved with about 2 degrees of bank toward the operating engine and the ball about one-half width toward that engine, not with wings level and the ball centered.
If directional control is being lost below VMC, immediately reduce power on the operating engine and lower the nose to accelerate; never attempt to power out of a VMC rollover.
Last updated: August 2026
The Private Pilot Airplane Category ACS includes AMEL and AMES , so Area IX Tasks E, F, and G and all four Tasks of Area X carry multiengine knowledge elements. Even a candidate who will never touch a twin should own this vocabulary — it recurs on every later FAA knowledge test.
The two radial lines and the speed that is not marked
Speed Marking Meaning
VMC RED radial line Minimum control speed with the critical engine inoperative . Below it, full rudder and up to 5 degrees of bank cannot hold heading.
VYSE BLUE radial line Best rate of climb, single engine. "Blue line" is the speed you fly after an engine failure — it buys the most altitude per minute, or the slowest descent.
VXSE not marked Best angle of climb, single engine — used only to clear an obstacle.
VSSE not marked Safe, intentional one-engine-inoperative speed. A manufacturer-designated minimum for intentionally shutting an engine down in training.
The critical engine
The critical engine is the one whose failure most adversely affects the performance or handling of the airplane. On a conventional U.S. twin with both propellers rotating clockwise as seen from the cockpit, the left engine is critical .
The reason is P-factor (Section 10.2). At a positive angle of attack, each propeller's descending blade generates more thrust, and the descending blade of a clockwise-turning propeller is on the right side of that propeller. So each engine's effective thrust line is displaced to the right of its own centerline. That puts the right engine's thrust on a longer moment arm about the airplane's center of gravity, and the left engine's on a shorter one. Lose the left engine and the remaining — right — engine produces the larger yawing moment, which is the more critical case.
Twins with counter-rotating propellers have no critical engine , because the moment arms are symmetric.
What raises and lowers VMC
VMC is a certification number determined under deliberately unfavorable conditions, and the test asks which way it moves.
Density altitude up → VMC down (normally aspirated engines). Higher up, the operating engine makes less power, so there is less asymmetric thrust to counter. This is the trap: at altitude the airplane may reach its stall speed before it reaches VMC , and a stall with asymmetric thrust rolls toward the dead engine and can spin.
CG moves aft → VMC up. An aft CG shortens the moment arm from the CG to the rudder, so the rudder has less authority.
Propeller windmilling → VMC up. A windmilling propeller adds drag on the dead side, increasing the yawing moment. Feathering lowers it.
Bank up to 5 degrees toward the operating engine → VMC down. Wings level with the ball centered gives the highest VMC.
Zero sideslip — the configuration that actually climbs
After an engine failure, three configurations are possible, and only one performs:
Wings level, ball centered. The airplane flies in a large sideslip. Huge drag penalty; often no climb at all.
Wings level, rudder holding heading. Still sideslipping badly.
Zero sideslip: approximately 2 degrees of bank toward the operating engine , with the inclinometer ball about one-half width toward the operating engine . Drag is minimized and the airplane delivers the single-engine climb performance the book promises.
Two degrees is barely perceptible — it is a sliver of bank, not a turn.
Identify, verify, feather, secure
The engine-failure flow in Tasks IX.F, IX.G, X.A:
Identify. "Dead foot, dead engine" — the foot that is not pushing rudder is on the side of the failed engine.
Verify. Slowly retard the throttle of the suspected engine. If nothing changes, you identified correctly.
Feather. Move that propeller control to feather — the blades rotate to a high, streamlined pitch nearly parallel to the relative wind, which converts an enormous drag disc into a thin one. Most light twins have a centrifugal latch that blocks feathering below roughly 800 RPM , so the propellers do not feather on every normal shutdown.
Secure. Mixture, fuel, magnetos, alternator, cowl flaps per the checklist.
Drag reduction (PA.IX.F.K5, PA.IX.G.K4) is the whole game: gear up, flaps up, propeller feathered , and the airplane held at zero sideslip. A windmilling propeller alone can cost more drag than the entire rest of the airframe.
Accelerate-stop, accelerate-go, and the honest performance picture
Accelerate-stop distance is the total distance to accelerate to a specified speed and then, with an engine failure at that speed, brake to a full stop on the remaining surface.
Accelerate-go distance is the distance to accelerate to that speed, lose an engine, and continue the takeoff to a height of 50 feet on the remaining engine. It is normally far longer than accelerate-stop, and many light twins cannot do it at all at high weight or high density altitude.
Losing one of two engines does not cost 50 percent of climb performance. Climb comes from excess power, and the excess is a small fraction of total power — so losing half the installed power typically costs roughly 80 percent or more of the climb capability . That is why a light twin's single-engine service ceiling can be below the terrain it is crossing, and why "the second engine takes you to the scene of the accident" is a saying rather than a joke.
Loss of directional control below VMC (PA.X.B.K3) has exactly one immediate answer: reduce power on the operating engine and lower the nose to accelerate . Reducing the asymmetric thrust restores control. Adding power to climb away from the ground makes the roll worse.