Single-Engine Climb Performance
One of the most important multi-engine ideas is that losing one of two engines does not mean losing only half the climb performance. Climb depends on excess power, not total power alone. A twin may use a large share of its total power just to maintain level flight, so removing one engine can erase most of the excess power available for climbing.
Power available versus power required
In normal two-engine flight, total power available exceeds the power required to maintain level flight. The difference is excess power, which can be converted into climb. After an engine failure, power available drops dramatically while the airplane also suffers new drag and control penalties. The remaining excess power can become very small.
Why the failed propeller matters
A windmilling propeller creates very high drag. Feathering the failed propeller reduces that drag and can substantially improve performance. This is why identify, verify and feather is such an important training concept.
Configuration matters
Landing gear, flaps, cowl flaps and other drag-producing configurations can reduce single-engine climb capability. The approved procedure for the aircraft is designed to place the airplane in the configuration that provides the best available performance while maintaining control.
Density altitude
Higher density altitude reduces engine power and propeller efficiency in normally aspirated airplanes. It also reduces the margin between power available and power required. A twin that climbs acceptably on one engine near sea level may have little or no positive climb capability at a high-elevation airport on a hot day.
Weight
Higher weight increases the power required for a given flight condition and generally hurts climb performance. Weight therefore has a major effect on whether an airplane can climb, maintain altitude or only descend after an engine failure.
VYSE and best single-engine climb
VYSE, shown by the blue radial line on many light twins, is the best rate-of-climb speed with one engine inoperative under the applicable conditions. Flying substantially away from the appropriate speed can reduce climb performance further.
Service ceiling
The single-engine service ceiling is tied to a specified minimum climb rate, not simply the altitude where climb becomes zero. Knowing that distinction is common checkride material.
Continue the engine-out sequence: Multi-engine checkride study guide · windmilling vs feathered propeller · single-engine service ceiling.
FAA source
The FAA Airplane Flying Handbook explains multiengine performance and engine-inoperative flight. Open the current FAA handbook.