Multiengine Operations
What the examiner is testing
Multiengine Operations is the core MEI domain: Vmc, critical engine, asymmetric thrust, drag reduction, single-engine performance, engine-failure procedures, and single-engine approach and landing. The examiner expects precise definitions and the ability to teach why the airplane behaves as it does.
Vmc and asymmetric flight
- Vmc is the minimum control speed with the critical engine inoperative, the other engine at maximum power, gear and flaps up, and no more than 5 degrees bank toward the operating engine. It is a control speed, not a safe operating speed.
- For most conventional twins, the left engine is critical; verify the specific airplane. Factors that raise Vmc include maximum power on the operating engine, aft CG, lighter weight, gear up, flaps up, and bank away from the operating engine.
- Vsse is the safe single-engine speed for intentional engine failure or training. Vsse is higher than Vmc. Vyse is the single-engine best rate of climb speed; Vxse is the best angle speed.
- Use zero sideslip: bank about 5 degrees into the operating engine and center the ball. Identify the dead engine with the dead foot, dead engine check, then verify before feathering.
Performance and procedures
- Reduce drag: feather the propeller, raise gear and flaps as appropriate, and clean up the airplane.
- Engine failure on takeoff requires a decision before rotation: abort if runway remains and stopping is assured; continue if committed and climb performance is available.
- Single-engine service ceiling is the altitude where the airplane can climb 50 feet per minute at Vyse; driftdown follows if above it.
Worked example
At 8,000 pounds, single-engine climb is 250 feet per minute at 100 knots ground speed. Required gradient to clear an obstacle 3 nautical miles away and 1,000 feet high is 1,000 / (3 x 6,076) = 0.055, or 5.5 percent. The airplane's gradient is 250 / (100 x 6,076 / 60) = 250 / 10,127 = 0.0247, or 2.5 percent. The airplane cannot meet the obstacle gradient. The reasoning: convert both values to the same units and compare gradient, not just climb rate.
Traps that cost marks
- Treating Vmc as a safe single-engine speed or demonstrating it at low altitude.
- Banking away from the operating engine, increasing sideslip and reducing performance.
- Feathering the wrong engine before verifying the failure.
- Forgetting to reduce drag or to check single-engine service ceiling and driftdown.
- Confusing Vxse and Vyse, or using two-engine speeds for a single-engine approach.