MULTIENGINE FLIGHT

This chapter is devoted to the factors associated with
the operation of small multiengine airplanes. For the
purpose of this handbook, a "small" multiengine airplane
is a reciprocating or turbopropeller-powered
airplane with a maximum certificated takeoff weight
of 12,500 pounds or less. This discussion assumes a
conventional design with two engines—one mounted
on each wing. Reciprocating engines are assumed
unless otherwise noted. The term "light-twin,"
although not formally defined in the regulations, is
used herein as a small multiengine airplane with a
maximum certificated takeoff weight of 6,000 pounds
or less.

There are several unique characteristics of multiengine
airplanes that make them worthy of a separate class rating.
Knowledge of these factors and proficient flight
skills are a key to safe flight in these airplanes. This
chapter deals extensively with the numerous aspects of
one engine inoperative (OEI) flight. However, pilots
are strongly cautioned not to place undue emphasis
on mastery of OEI flight as the sole key to flying
multiengine airplanes safely. The inoperative engine
information that follows is extensive only because
this chapter emphasizes the differences between flying
multiengine airplanes as contrasted to single-engine
airplanes.

The modern, well-equipped multiengine airplane can
be remarkably capable under many circumstances. But,
as with single-engine airplanes, it must be flown prudently
by a current and competent pilot to achieve the
highest possible level of safety.

This chapter contains information and guidance on the
performance of certain maneuvers and procedures in
small multiengine airplanes for the purposes of flight
training and pilot certification testing. The final
authority on the operation of a particular make and
model airplane, however, is the airplane manufacturer.
Both the flight instructor and the student should be
aware that if any of the guidance in this handbook conflicts
with the airplane manufacturer's recommended
procedures and guidance as contained in the FAA approved
Airplane Flight Manual and/or Pilot's
Operating Handbook (AFM/POH), it is the airplane
manufacturer's guidance and procedures that take
precedence.

GENERAL
The basic difference between operating a multiengine
airplane and a single-engine airplane is the potential
problem involving an engine failure. The penalties for
loss of an engine are twofold: performance and control.
The most obvious problem is the loss of 50 percent
of power, which reduces climb performance 80 to 90
percent, sometimes even more. The other is the control
problem caused by the remaining thrust, which
is now asymmetrical. Attention to both these factors
is crucial to safe OEI flight. The performance and
systems redundancy of a multiengine airplane is a
safety advantage only to a trained and proficient
pilot.

TERMS AND DEFINITIONS
Pilots of single-engine airplanes are already familiar
with many performance "V" speeds and their definitions.
Twin-engine airplanes have several additional
V speeds unique to OEI operation. These speeds are
differentiated by the notation "SE", for single engine.
A review of some key V speeds and several new V
speeds unique to twin-engine airplanes follows.

• Vr – Rotation speed. The speed at which back
pressure is applied to rotate the airplane to a takeoff
attitude.
• Vlof – Lift-off speed. The speed at which the
airplane leaves the surface. (Note: some manufacturers
reference takeoff performance data to
VR, others to Vlof.)
• Vx – Best angle of climb speed. The speed at
which the airplane will gain the greatest altitude
for a given distance of forward travel.
• Vxse – Best angle-of-climb speed with one
engine inoperative.
• Vy – Best rate of climb speed. The speed at
which the airplane will gain the most altitude for
a given unit of time.
• Vyse – Best rate-of-climb speed with one engine
inoperative. Marked with a blue radial line on
most airspeed indicators. Above the single-engine
absolute ceiling, Vyse yields the minimum rate of
sink.
• Vsse – Safe, intentional one-engine-inoperative
speed. Originally known as safe single-engine
speed. Now formally defined in Title 14 of the
Code of Federal Regulations (14 CFR) part 23,
Airworthiness Standards, and required to be
established and published in the AFM/POH. It is
the minimum speed to intentionally render the
critical engine inoperative.