AOPA Pilot Magazine - July 2024 - 89

RUDDER & WRENCH
FLY ING SMART /
the aircraft has achieved VEF
airspeed
(the speed at which the critical engine
is assumed to fail during takeoff). From
there, the aircraft accelerates to a reference
airspeed, V* (more on this later).
The pilot then commands idle thrust on
the remaining engines, applies maximum
braking, and brings the aircraft to a stop.
The accelerate-stop distance is the total
distance traveled by the airplane. For a
fixed V*, a lower value of VEF
results in an
increased accelerate-stop distance. For a
given VEF
, increasing the reference speed
V* has the same effect.
If the aircraft has sufficient power
remaining, a pilot might achieve a better
outcome by continuing the takeoff in
the above engine-failure scenario. After
engine failure at VEF
ues to accelerate to the rotation speed VR
From there, it continues to climb until it
reaches takeoff safety speed, V2
Balancing act
Taking a lesson from the pros
BY CATHERINE CAVAGNARO
LAST SPRING I was pleased to present a
webinar for the Experimental Aircraft
Association. " Lessons from a Performance
Chart " focused on takeoff and climb performance,
but the general principles apply
to many other operating handbook charts.
One participant, Mike, emailed later to say
he had heard of the balanced field concept
for takeoff used by commercial operators
but confessed he didn't understand
it. Mike asked if I could offer an explanation
and wondered if there were any
takeaways that general aviation pilots
might extract for safer operations.
Having never flown for a commercial
operator, I found myself a bit flat-footed
on the concept, so I dived into various
flight manuals to brush up on the topic.
What I found was honestly confusing,
especially in the FAA's cumbersome and
incomplete explanations. It's easy to
become mired in the definitions that make
the reader hop back and forth among the
various sections of the Code of Federal
Regulations (CFRs) and miss the spirit of
the balanced field concept. The following
discussion is not meant to detail the definitions
and requirements in the CFRs.
Rather, I hope that, armed with a general
understanding, you will find the FAA
material more accessible.
Let's start by assuming that a multiengine
airplane departs a sea-level
airport on a standard day with no winds.
The airplane begins the takeoff roll and
one engine stops producing thrust when
(a speed
that provides a reasonable climb rate and
a buffer over stall speed), at a height of 35
feet above the ground. The total distance
becomes the accelerate-go distance.
If an engine failure occurs at a low
airspeed, it makes sense for the pilot to
throttle back and bring the airplane to
a halt. At higher airspeeds, though, the
pilots should continue the takeoff and
handle the failure as an in-flight problem
for the ability to stop without impacting
obstacles is compromised or impossible.
There is a middle range of airspeeds
where either, or perhaps neither, action
will produce a safe outcome. It all boils
down to the runway available.
The attached figure shows that a sufficiently
long runway provides a range
of airspeeds for which either decision-
stop or continue the takeoff-should
have a safe outcome. The changeover airspeed
(the above reference airspeed V*),
called the takeoff decision speed or V1
, is
selected to be somewhere in the middle
of that range. Such a long runway, called
a balanced field, offers a greater margin of
safety. On the other hand, if the runway is
too short, there is an airspeed band during
AOPA PILOT / July 2024
89
, the airplane contin.
MIKE
FIZER
AOPA Pilot Magazine - July 2024

Table of Contents for the Digital Edition of AOPA Pilot Magazine - July 2024
