Flying twin-engine aircraft opens the door to many exciting challenges, both in real-world flying and in Flight Simulator. In a twin-engine aircraft, you can fly faster than in a single-engine aircraft, carry a heavier payload, and benefit from more backup systems. Twin-engine aircraft are the choice of pilots who routinely fly over mountains and water, travel long distances, fly at night, and cruise at high altitudes. Having more than one engine to keep you airborne brings a new safety factor into play. It also emphasizes the need to keep special piloting skills polished in case an engine fails.
Transitioning to a twin-engine aircraft, you will acquire new flying skills and perform different procedures than in a single-engine aircraft. Not only does a twin-engine airplane have two engines to control, but the aircraft usually is equipped with more complex features, such as retractable landing gear and variable pitch propellers. There's just more to learn: more instruments and more systems, more procedures that help you control a larger and more powerful aircraft on longer and often higher flights. That's the exciting challenge of twin-engine flying.
Two Approaches to Twin-Engine Flying in Flight Simulator
In general terms, flying twin-engine aircraft is not much different than flying single-engine aircraft in Flight Simulator. That is, if you only want to hop in the Flight Simulator cockpit and fly, all you have to do is throttle up and take off. Throttles and engines are synchronized by default. But Flight Simulator offers the virtual pilot the chance to learn twin-engine techniqueand that includes what to do if you lose an engine.
Basically, there are two ways to approach twin-engine flying in Flight Simulator:
- Just throttle up and fly.
- Let twin-engine flying change your approach to flying. Once you do this, you'll begin to calculate what you will do if an engine fails on takeoff, soon thereafter, or somewhere during flight. And all this extra thought makes you a better pilotand a better-prepared pilotno matter how many engines your aircraft may have.
V Speeds to Remember for Twin-Engine Flying
V1Takeoff decision speed: V1 is the speed at which it may not be possible to stop the airplane on the runway in case of rejected takeoff (RTO).
V2Minimum takeoff safety speed: V2 is the minimum safe flying speed should an engine fail immediately after takeoff.
Vyse: Vyse is the best single-engine climb speed when flying with one engine inoperative and the other operating at full power. Pilots often refer to flying at Vyse as "flying the blue line" because Vyse is marked by a blue line on the airspeed indicator. See the Baron's airspeed indicator's Vyse blue line marked at 101 knots (above). Vyse is determined with the aircraft at maximum gross weight, which is a worst-case scenario because the heavier the aircraft the higher the Vyse. It's safest to reach Vyse as soon as possible after takeoff.
Vmc: Vmc is the minimum airspeed at which the aircraft's directional control can be maintained when the critical engine is inoperative and the other is operating at full power. At speeds below Vmc, the rudder is no longer able to overcome the asymmetrical yawing force produced by the remaining operating engine. On the Beechcraft Baron's airspeed indicator (above) Vmc is indicated by the red line at 84 knots. No twin-engine aircraft should leave the runway before reaching Vmc.
Actual Vmc Will Vary
Vmc is a number published in most twin-engine aircraft handbooks. But that number may not turn out to be your actual Vmc because Vmc depends on how much weight the aircraft is carrying. If, for example, your aircraft is loaded with full fuel and carrying a full payload, the airplane's Vmc will be higher than a lighter-loaded aircraft. See the Single-Engine Savvy (AOPA) article for information about factors that affect Vmc.
Between Vmc and Vyse: The Danger Zone
Airspeeds between Vmc and Vyse are often considered a danger zone when taking off. That's because if your aircraft were to lose an engine during takeoff while flying between these two V speeds, you would be dangerously close to Vmc and not be able to achieve your single-engine maximum climb rate. Without some altitude, there is little or no room for recovery or climbing above obstacles on the ground.
Real-world twin-engine pilots review engine-out procedures before every flight, even if they've already made several flights that day. It's a good idea for Flight Simulator pilots to review engine-out procedures, too.
Here's an easy pre-takeoff twin-engine review. Speak these to yourself before every twin-engine flight:
- "If an engine fails before V1: Close both throttles and use the brakes to stop on the remaining runway."
- "If an engine fails after V1: Take off and deal with the problem as per the engine-out procedure."
Just saying these sentences aloud provides an instant review of what to do and reminds you that an engine could fail at any time. Remember, if an engine does fail on takeoff, you'll only have an instant to decide what to do.
Engine Failures in Flight Simulator
Of course, engine failures won't happen in Flight Simulator unless you make some errors, such as running out of fuel, forgetting to switch fuel tanks, or forgetting to lean the mixture. But you can also plan to have an engine failure. (For information, see Setting Up Failures.)
Saving Flights with Engine Failures
Saving flights with engine failures will help keep you in practice for engine-out procedures. Perhaps you'll want to select a few engine-out scenarios, such as having an engine fail on takeoff or during flight.
What to Do When an Engine Fails
Flying on one engine: The Beechcraft Baron 58 with a feathered propeller.
When an engine fails, you've got to do everything possible to:
- Control the aircraft (airspeed, pitch, and yaw).
- Achieve maximum power possible.
- Reduce drag as much as possible.
A set procedure will help you compensate for the lost power and the effects of asymmetrical thrust. Today's twin-engine aircraft must be able to fly after losing an engine. This requirement, however, does not mean that that the airplane must be able to keep climbing.
Once you recover from losing an engine, the goal is to get the most power from the remaining engine(s) you have left, and reduce your aircraft's drag as much as possible.
Before you try to memorize the particulars of a procedure, here's the big picture of what you must do when an engine fails:
- Take care of the bad engine.
- Take care of the good engine.
- Find a place to land.
- Go there.
To perform a standard engine-out procedure
Securing a Dead Engine
Once you have completed the engine-out procedure and you are sure that you will not be able to restart the engine, you'll want to secure the dead engine.
To secure the dead engine
In a twin-engine aircraft, it may seem that if you lose one engine, then you'll have half the usual amount of power. But that's not the case. The power available in excess of the power required to maintain level flight determines aircraft climb performance. With an engine out, your aircraft is now a single-engine aircraft that is carrying the dead weight of the nonfunctioning engine, as well as any excess drag from the nonoperating engine and propeller. Under normal operating conditions, you need roughly 40 percent of your total power for level flight. When you lose an engine, you lose 50 percent of your aircraft's power, but 80 percent of your aircraft's performance. If you lose an engine on takeoff, a go-around will be difficult or impossible.
P-Factor and the Critical Engine
The most critical engine is the engine that affects directional control the mostit's the engine you don't want to fail because when the critical engine fails, directional control is often difficult to regain.
The P-factor (or asymmetric propeller thrust) and the rotation of the engines determine which engine is the critical engine. The P-factor is caused by the different thrust of rotating propeller blades at certain flight attitudes. Because the downward moving blade has a greater angle of attack than the upward moving blade whenever the aircraft is flying in attitudes which are not parallel to thrust lineespecially when the aircraft is pitched up, or flying at slow airspeeds or high-power conditionsthe propeller produces more thrust on the downward rotating side than the upward rotating side. This effect is especially noticeable during takeoff.
On twin-engine aircraft where the propellers rotate the same direction (usually clockwise when viewed from the pilot's seat of the aircraft on many light twins), the center of thrust is actually at the right side of each engine. The turning (or yawing) force of the right engine is greater than the left engine because the center of thrust for that engine is farther from the centerline of the fuselage. Thus, when the right engine is running and the left engine is not, the yawing force is greater than if the left engine were the only engine running. Directional control may be difficult when the left engine (the critical engine, in this example) fails. In summary, the critical engine is the engine that requires the most rudder force to correct the yaw when that engine fails.
Some aircraft have counter-rotating propellers, which both rotate toward the fuselage. In this case, there is no critical engine because the yawing force is the same for each propeller.
The Dangers of Falling Below Vmc
Vmc is the minimum speed at which the aircraft can maintain directional control with one engine producing full power. Below Vmc, by definition, you do not have enough rudder to counteract the turning moment, but the pilot still has some control of the aircraft. For example, pitch control is still available and will be needed in the recovery from flight below Vmc.
This means that when a twin-engine aircraft operating on only one engine falls below Vmc, the asymmetric force of one operating engine will cause the aircraft to yaw. The instant a directional change in the aircraft is noted at or near Vmc, the pilot must take steps to attain a speed at or greater than Vmc and control the aircraft.
To regain control of the aircraft below Vmc
Remember, however, that below Vmc you have no directional control of the aircraft. The recovery procedure above works in many sub-Vmc conditions, but without directional control below Vmc, you may end up in an unusual attitude, perhaps inverted, and the exact recovery procedure may depend more on the particulars of the situation than on any one procedure. The main thing to remember in a sub-Vmc situation is that to regain control, you must reduce power on the good engine as well as get the aircraft moving faster than Vmc. This latter objective usually means getting the nose pitched down. If you have plenty of altitude, recovery from such an "upset" is possible, perhaps likely. But if you are flying low and encounter such a situation, the results can ruin your day.
Restarting the Engine
The following procedure is adapted from the Beechcraft Baron 58 Pilot Operating Handbook.
To restart the engine
Approach and Landing with an Engine Out
Landing with an engine out is not much different from a normal approach and landing. Until you are sure to make the runway, the final approach speed should be greater than Vyse. This is so you will maintain maximum single-engine climbing speed if you need to abort the landing. Also, when lowering flaps be aware that most light twin-engine aircraft cannot make a go-around on a single engine with full flaps.
Differential Thrust: Controlling Engines Independently
When executing the engine-out procedures or when using differential thrust during taxiing or crosswind landings in twin-engine aircraft, you need independent engine control. Watch the King Kwik Tips Video above to learn how to control engines independently.
When you increase/decrease the throttle on your joystick or keyboard, both throttles are synchronized by default. The same is true when you change the mixture and propeller controls.
To control the engines independently
Twin-Engine Flying Tips
To feather the propeller
To control the throttle
To control the mixture
To control the cowl flaps
To control magnetos
Moving Up to Jets
Now that you've mastered twin-engine flying in light twin-engine piston aircraft, it's time to move up to turbine aircraft, such as the Beechcraft King Air 350, Bombardier Learjet 45, and modern jet airliners. To get you started, here are a few tips:
To learn more about flying the Beechcraft Baron 58, see the Beechcraft Baron 58 Aircraft Information article.
You may also want to read Multi-Engine Flying by Paul A. Craig, McGraw Hill, 1997.