Multiengine Introduction and Lesson Plans

A second engine does not make an airplane twice as safe. It roughly doubles the thrust available, and it gives you a second chance at a problem that would put a single on the ground — but it also gives you a second engine to fail, a second propeller to drag, and an asymmetric airplane to fly while you sort it out. Losing one engine in a light twin is a 50% loss of thrust and an 80–90% loss of climb, and in many airplanes on many days it is a 100% loss of climb.

That arithmetic is the whole subject. Climb comes from the thrust left over after level flight is paid for. Take the FAA’s example: a twin with 200 thrust horsepower per side needs 175 to hold level flight, so both engines running leaves 225 horsepower of reserve. Lose one and the reserve is 25. Nothing about the airplane changed except that almost all of your margin went away.

Everything below is about that margin — how to keep the little of it you have, and how to decide, before the runway runs out, whether you have any at all. Nothing here replaces the AFM/POH for the airplane you’re flying, which is the final authority, or training with an instructor in it.

Key Airspeeds

Twins add a set of speeds to the ones you already know, most of them marked “SE” for single-engine. Two of them are painted on the airspeed indicator and you will spend the rest of your multiengine flying between them.

• V_MC — minimum control speed with the critical engine inoperative. Red radial. It says nothing about whether the airplane will climb.
• V_YSE — best rate of climb, one engine inoperative. Blue radial. Above the single-engine absolute ceiling it gives you the slowest rate of sink — the drift-down speed.
• V_XSE — best angle of climb, OEI. Used only to clear an obstacle; it may be only a few knots above V_MC, and even at V_XSE the gradient is paltry.
• V_SSE — safe, intentional one-engine-inoperative speed. The minimum speed at which an engine may be intentionally failed. No intentional failure in flight below it, ever.
• V_R / V_LOF — rotation and lift-off. If the manufacturer publishes neither, use V_MC + 5 knots as a minimum, and never be airborne below V_MC.

Vmc Is Not a Number

The red radial is a single number produced under one very specific set of certification conditions. Change any of them and the real minimum control speed moves — sometimes a great deal, and usually in the direction you don’t want.

Under 14 CFR part 23, V_MC is determined with:

• Maximum available takeoff power on the operating engine
• The critical engine’s propeller windmilling in the takeoff position (feathered only if autofeather is installed)
• Most unfavorable — aft-most — CG, and maximum takeoff weight
• Landing gear retracted
• Wing and cowl flaps in the takeoff position
• Trimmed for takeoff, airborne and out of ground effect
• A maximum of 5° of bank toward the operating engine

The flight test standard is that the pilot can stop the turn within 20° of heading when the critical engine is suddenly failed, then hold straight flight with no more than 5° of bank.

How each factor moves it:

• Bank angle is the big one. V_MC may rise more than 3 knots for every degree of bank given up between 5° and wings level. With the wings held level, loss of directional control can happen almost 20 knots above the published number. The 5° allowance exists so the horizontal component of lift, rather than sideslip, balances the rudder’s side force.
• Aft CG raises it. Moving the CG aft shortens the rudder’s moment arm, so the rudder does less for the same deflection.
• Reducing weight raises it. Less weight means less horizontal lift available from that bank angle. The lightly loaded training twin is not the benign case it feels like.
• Retracting the gear raises it. Extended gear adds directional stability — which is one reason the gear-down engine failure is a rejected takeoff, not a climb.
• Altitude lowers it. A normally aspirated engine makes less power up high, so there is less asymmetric thrust to fight. Turbocharged engines hold takeoff power — and therefore V_MC — up to the critical altitude.

That last one sets a trap, because stall speed does not change with altitude while V_MC falls. Climb high enough and they meet.

The Critical Engine

On a twin with both propellers turning clockwise seen from the cockpit, the left engine is critical — its failure hurts the most. At low airspeed and high angle of attack, the descending blade of each propeller takes a bigger bite than the ascending blade, so each engine’s effective thrust line shifts to the right of its hub. On the right engine that shift moves thrust outboard, lengthening its moment arm about the CG. On the left engine it moves thrust inboard, shortening it.

So the right engine, working alone, swings the airplane harder than the left engine does, and demands more rudder to hold. Lose the left one and you’re left with the stronger, longer-armed survivor. A counter-rotating right engine erases the difference — neither engine is critical, and the handling is the same either way.

PAST is the usual memory aid for the four effects that make the left engine critical. The FAA documents name P-factor as the mechanism; the other three are the traditional teaching set, and each has a simulator that isolates it:

• P — P-factor: the moment arms stop matching, as above.
• A — Accelerated slipstream: the faster air behind the descending blade lands outboard on the right wing and inboard on the left, so the surviving right engine also rolls you harder.
• S — Spiraling slipstream: only the left engine’s corkscrew wraps onto the fuselage and strikes the fin. That fin force pushes the nose left, which helps when the right engine quits and does nothing when the left one does.
• T — Torque: a clockwise propeller rolls the airplane left — toward a dead left engine, away from a dead right one. A pure couple; only the sign matters.

Zero Sideslip

With an engine out there is no instrument that tells you the airplane is flying clean. The ball is lying to you: with asymmetric thrust, a centered ball is not coordinated flight. You have to put the airplane in a predetermined attitude and leave it there.

There are only two controls available against asymmetric thrust — yaw from the rudder, and the horizontal component of lift from bank. Used alone, neither is right.

Note the order of operations after a failure: use five degrees, and up to ten, of bank initially to stop the yaw and get directional control, then relax to the two or three degrees that gives best climb. Control first, performance second.

The Drag Budget

With so little excess power left, drag is no longer a detail. A propeller windmilling at high rpm in the low blade-angle range can produce as much parasite drag as the entire rest of the airplane. Feathered, that same propeller is a small part of the total.

A word on what the certification rules actually promise, because it is less than most pilots assume. For twins over 6,000 lb (or with V_SO above 61 knots) there is a real single-engine climb requirement at 5,000 feet. For light twins at or below 6,000 lb with V_SO of 61 knots or less, the single-engine rate of climb at 5,000 feet must merely be determined — and it is allowed to be a negative number. There is no requirement that your light twin climb on one engine at any altitude, including sea level.

• Single-engine service ceiling — where the best you can do is 50 fpm.
• Single-engine absolute ceiling — where climb is zero. Above it, V_YSE buys you the slowest descent, not a climb.

Check the single-engine service ceiling against the terrain and the minimum IFR altitudes on your route before you go, not after something quits.

The Takeoff Decision

The takeoff is the one phase where you must have already decided what you’ll do, because there won’t be time to work it out. Brief it every time, even alone.

Three scenarios cover an engine failure on takeoff:

1. Landing gear still down. Close both throttles and land on the runway or overrun remaining. Keep the nose straight. Retracting, feathering, and accelerating away is not realistically available to you.
2. Gear up, climb performance inadequate. Land essentially straight ahead, under control, at V_YSE. Off-airport landings under control have a very high survival rate; stall-spin accidents from trying to fly beyond the airplane’s performance do not.
3. Gear up, climb performance adequate. Fly the procedure below.

As a planning matter, the option of continuing probably does not exist unless the published single-engine rate of climb is at least 100 to 200 fpm — turbulence, gusts, engine and propeller wear, or slightly imperfect technique will erase a 200 fpm book number.

Engine Failure Procedure

The order is Control, Configure, Climb, Checklist.

• Control. Stop the yaw with rudder — promptly, and aggressively if needed. Keep the airspeed above V_MC; if you cannot hold the yaw with full rudder, reduce power on the good engine. Bank 5° and up to 10° toward the operating engine to get control established, and lower the pitch attitude from V_Y to V_YSE.
• Configure. Execute the memory items.
• Climb. Relax to about 2° of bank with the ball a third to a half out toward the operating engine, and hold V_YSE with pitch. Climb straight ahead or with shallow turns to at least 400 feet AGL before considering a return.
• Checklist. Then, and only then, pick up the printed checklist and secure the engine.

A typical Engine Failure After Takeoff memory block:

Airspeed — V_YSE · Mixtures — RICH · Propellers — HIGH RPM · Throttles — FULL POWER · Flaps — UP · Landing gear — UP · Identify — determine failed engine · Verify — close throttle of failed engine · Propeller — FEATHER · Trim — ADJUST · Failed engine — SECURE · As soon as practical — LAND

Identify is done with your feet and hands, not the gauges: the rudder you’re holding is on the side of the working engine, so dead foot — dead engine. Verify by retarding the suspected throttle — if nothing changes, you picked right. Then feather. The other aid worth teaching is “raise the dead” — the dead engine’s wing comes up with that small bank toward the good side.

The Securing Failed Engine list follows: mixture idle cutoff, magnetos off, alternator off, cowl flap closed, boost pump off, fuel selector off, prop sync off, electrical load reduced, crossfeed considered. Apart from the cowl flap, none of these affect climb performance — which is exactly why they are done deliberately and late rather than in a rush.

Two cautions on feathering. Below roughly 800 rpm the anti-feathering lock pins engage and the blades will no longer go to feather, so if you’re going to feather, do it before the rpm decays. And not every failure is a complete one — an engine still making partial power may be worth leaving alone until you have altitude and airspeed, since shutting down a partially working engine can make things worse.

Engine Failure in Cruise

Up high there is time, and the mistake is fixating on the engine instead of flying the airplane. Airplanes have been lost at altitude to a problem that was survivable.

Most power losses are not catastrophic. Work an orderly inventory of gauges and switches: fuel selector and tank quantity, boost pump, mixture, carburetor heat or alternate air, magnetos. Heavy vibration, smoke, blistering paint, or a large trail of oil is a different matter — feather it, secure it, declare, and divert. If in doubt and the engine is still making power, leave it running.

Above the single-engine absolute ceiling the airplane will drift down: hold V_YSE, accept the descent, and know that the rate of loss is greatest right after the failure and eases as you approach the ceiling. For a long single-engine leg, crossfeed lets the operating engine draw from the opposite wing — which also keeps the airplane from going wing-heavy. Terminate crossfeed and return to the main tank before landing.

Engine-Out Approach and Landing

Fly it as close to a normal approach as you can — same pattern, same altitudes, similar speeds — with more power on the operating engine and the knowledge that some of your options are gone.

• Gear down abeam the intended point of landing if performance allows; confirm it down.
• Partial flaps (typically 10°) on downwind, and up to an intermediate setting (about 25°) on base if performance is holding. If airspeed is decaying or the sink rate is building, delay further flaps.
• V_YSE is the minimum airspeed until the landing is assured, then 1.3 V_SO or the POH speed.
• A normal 3° path. Avoid the long, flat, low approach, and avoid large or sudden power changes.
• Expect a rudder trim change in the roundout as the operating engine comes to idle. Some pilots set rudder trim to neutral on final and simply hold the pressure — either technique is fine, but pick one.
• With only one windmilling propeller there is less drag, so the airplane floats more than it does on two.

Plan to land off the first approach. A single-engine go-around from a landing configuration usually is not available: with gear and full flaps out, most light twins cannot climb, and 500 feet or more can be lost just trying to get cleaned up. Once you’re on final, gear and flaps extended, you are committed to putting it on the runway — or the taxiway, or the grass.

Systems Worth Knowing Cold

• Feathering propellers. Unlike a single’s, these are counterweighted and oil-pressure-to-decrease-pitch: oil pressure holds them out of feather, and the counterweights plus a spring or nitrogen dome charge drive them to feather when pressure is dumped. Full feathering can take up to 10 seconds.
• Unfeathering accumulator. Stores oil pressure so a feathered engine can be restarted in flight without the starter. Moving the prop control out of feather releases it.
• Prop sync / synchrophaser. Off for takeoff, landing, and all single-engine operation.
• Crossfeed. A real functional check means running each engine from crossfeed for at least a minute at 1,500 rpm or more, then re-confirming flow from the mains before takeoff. Never used for takeoff or normal landing.
• Alternators. One per engine, paralleled. Lose one and you may need to shed load.
• Combustion heater, deice and anti-ice, alternate static and induction air, nose baggage — all common on twins and all worth a systems lesson of their own. Anti-ice equipment being installed does not mean the airplane is approved for known ice.
• Weight and balance. Twins introduce nacelle lockers, nose baggage, aux tanks, ramp weight, maximum landing weight, and often a zero fuel weight limit. Some models need ballast with only two aboard. Remember that aft CG raises V_MC.

The Vmc Demonstration

Done at or above 3,000 feet AGL. Assume a conventional twin, left engine critical.

1. Gear up, flaps in the takeoff position, trimmed for takeoff. High rpm on both propellers.
2. Slow to about 10 knots above V_SSE or V_YSE, whichever is higher, on a chosen entry heading.
3. Left throttle to idle; right engine to the takeoff power setting.
4. Hold heading primarily with right rudder, and establish up to 5° of bank toward the operating engine.
5. Raise the pitch to decelerate at 1 knot per second, no faster, adding rudder as control effectiveness decays and aileron as needed to hold the bank.
6. At the first sign of uncontrollable yaw or any stall symptom — horn, buffet, or a rapid decay in control effectiveness — recover: simultaneously reduce power on the operating engine and lower the pitch attitude. Regain V_SSE or V_YSE on the entry heading, then restore symmetric power.

Never recover by adding power to the idling engine. Losing altitude is expected — this is a demonstration of controllability, not performance, and holding altitude is not a criterion.

If density altitude is high enough that the stall would arrive before the yaw, don’t press it. The accepted technique is to artificially limit rudder travel so loss of directional control is reached at a speed comfortably above the stall — about 20 knots above V_S is a reasonable target. A Vmc demo allowed to become a single-engine stall with high asymmetric thrust can depart toward the idle engine, into a spin no twin is certificated to recover from.

Teaching It

This is where the multiengine instructor earns the rating. The airplane is unforgiving of a sloppy training environment, and most of the risk is manufactured by the instructor rather than the airplane.

• Brief every flight: objectives, maneuvers, exactly how simulated failures will be introduced, what the learner is expected to do, and the completion standards. No surprises. Unannounced failures belong only in a checking scenario both pilots have agreed to beforehand.
• Never fail an engine below V_SSE. Never.
• All in-flight simulated failures below 3,000 feet AGL are introduced with a smooth throttle reduction — the engine stays running and instantly available. On the ground roll, use the mixture, at no more than 50% of V_MC.
• Low-altitude work starts at 400 feet AGL minimum, and only after the learner has mastered the procedure at altitude. Below 200 feet belongs in a simulator.
• Never pull circuit breakers to simulate failures. It leads to gear-up landings.
• Zero thrust, stated out loud. Set zero thrust and say something unambiguous: “I have the right engine; you have the left. I have set zero thrust and the right engine is simulated feathered.” Ambiguity about who owns which control is how airplanes get bent.
• Care for the “failed” engine like the learner cares for the good one — cowl flap, mixture, an occasional clearing, and no big power application right after a long cool-down at zero thrust.
• Plan actual feathering so the unfeather and restart is complete no lower than 3,000 feet AGL, positioned where a safe landing on an airport is available if it won’t unfeather.
• Teach the difference between zero thrust and a genuinely windmilling propeller. A learner who has only ever seen zero thrust may not believe how much a windmilling prop costs — and that disbelief is what makes pilots reluctant to feather when it counts.
• Training weights flatter the airplane. Most training happens light, where single-engine performance is deceptively good. Occasionally limit manifold pressure artificially to show what a hot, heavy day actually looks like. Don’t load passengers to do it for real.
• Use the airplane as a ground trainer. A great deal of procedural learning happens parked, engines off, at zero risk.
• Touch-and-goes are discouraged in twins — reconfiguring in the time available is its own hazard. Full-stop taxi-backs during familiarization; solo touch-and-goes in a twin, never.
• Nothing gets moved on the runway after landing unless there’s a clear operational need. A startling number of gear retractions happened when the pilot meant to raise the flaps.

Lesson Plans

Structured for a pilot who already holds an airplane single-engine rating and is adding airplane multiengine land. Under 14 CFR 61.63(c) there is no minimum flight time and no additional knowledge test — only training, an endorsement, and the practical test — so the syllabus is finished when the standards are met, not when the hours are. Flight lessons are flown to the Private or Commercial Airplane ACS as appropriate to the pilot’s certificate level.

Ground 1 — The Airplane and Its Systems

• Feathering propellers: counterweights, oil pressure, the dome charge, and the 800 rpm lock pins.
• Unfeathering accumulator, prop sync, crossfeed, alternator paralleling and load shedding.
• Fuel system in detail — tanks, selectors, boost pumps, crossfeed limitations.
• Combustion heater, anti-ice and deice, alternate static and induction air.
• Weight and balance: zero fuel weight, ramp and maximum landing weight, ballast, and why aft CG raises V_MC.

Completion standard: draws the fuel and propeller systems from memory and states the crossfeed limitations for this airplane; computes a loading at maximum takeoff weight and at aft CG without reference to notes.

Ground 2 — Engine-Out Aerodynamics

• The V-speeds and what each is for; the red and blue radials.
• V_MC: the certification conditions and how each one moves the real number. Bank angle emphasized.
• V_MC/V_S convergence with altitude and what it means for the demonstration.
• The critical engine and PAST; counter-rotating props.
• Zero sideslip — the three cases, and why the ball is not the answer.
• Drag: windmilling versus feathered, gear, flaps, sideslip.

Completion standard: explains, without notes, why V_MC rises with a lighter airplane and with wings level, and states the target bank and ball position for zero sideslip in this airplane.

Ground 3 — Performance, Procedures, and the Decision

• Accelerate-stop and accelerate-go from the POH charts, for the day’s actual conditions.
• Single-engine service and absolute ceiling; drift-down; checking terrain and MIAs before departure.
• The three engine-failure-on-takeoff scenarios and the takeoff brief.
• Control–Configure–Climb–Checklist; memory items; securing; cruise failures; the OEI approach.

Completion standard: recites the Engine Failure After Takeoff memory items cold; computes today’s accelerate-stop and accelerate-go and states the go/no-go for the intended runway.

Flight 1 — Familiarization

• Preflight, ground handling with differential power, run-up including the propeller and crossfeed checks.
• Normal takeoff and climb: V_R/V_LOF, gear up no later than V_YSE, the 400–500 foot transition.
• Airwork on two engines: steep turns, slow flight, power-on and power-off approaches to stall.
• Normal and crosswind landings, full-stop taxi-backs.

Completion standard: flies the airplane to ACS tolerances on two engines and completes the takeoff brief unprompted.

Flight 2 — Engine-Out Aerodynamics at Altitude

• At 3,000+ feet AGL: drag demonstration — the airplane at V_YSE clean, then gear, then flaps, then sideslip, then windmilling versus zero thrust.
• Zero sideslip with a yaw string. Find the exact bank and ball position for this airplane.
• V_MC demonstration and recovery.
• Simulated engine failure at altitude: Control, Configure, Climb, Checklist, on heading and on speed.

Completion standard: recovers from the V_MC demonstration at the first indication with a simultaneous power reduction and pitch change; holds V_YSE ±5 knots and heading ±10° through a simulated failure while completing the memory items.

Flight 3 — Feathering and Single-Engine Handling

• Actual feather and unfeather, positioned over an airport, restart complete no lower than 3,000 feet AGL.
• Single-engine climbs, level flight, and turns both directions — including turns toward the failed engine.
• Single-engine service ceiling demonstrated or computed against the day’s conditions.

Completion standard: feathers and restarts without prompting, and maintains V_YSE ±5 knots throughout.

Flight 4 — Engine-Out in the Pattern

• Engine failure on the takeoff roll (mixture, below 50% V_MC) — reject, straight, both throttles closed.
• Engine failure after lift-off with the gear down — reject and land ahead.
• Engine failure after lift-off at or above 400 feet AGL with the gear up — continue, configure, climb.
• Single-engine approaches and landings, full stop. Single-engine go-around discussed on the ground, not flown from a landing configuration.

Completion standard: the reject is instant and straight; the OEI approach arrives at V_YSE until the landing is assured and touches down in the touchdown zone without a go-around.

Flight 5 — Consolidation and the Cross-Country

• A real cross-country in the airplane, planned against single-engine ceilings and terrain.
• Engine failure in cruise: fly the airplane, inventory, decide, divert, declare.
• Crossfeed in flight. Drift-down if conditions allow it safely.
• If instrument rated: OEI instrument approach, and the missed-approach reality on one engine.

Completion standard: handles a cruise failure without loss of altitude control or fixation, and reaches a diversion decision that accounts for the single-engine ceiling.

Flight 6 — Checkride Preparation

• Every ACS task to standard, in one flight, in any order.
• Oral review: systems, V-speeds, V_MC factors, performance charts, and the takeoff decision.

Completion standard: all tasks to ACS tolerances with no instructor prompting; endorsement issued.

References

Both free from the FAA, both worth reading in full:

• Airplane Flying Handbook (FAA-H-8083-3), Chapter 13 — Transition to Multiengine Airplanes
• Flying Light Twins Safely (FAA-P-8740-66)

The AFM/POH for the specific airplane always takes precedence over anything in a handbook or on this page — and over anything an instructor tells you, including me.