| Home | Privacy | Contact |

Airplane Flying Handbook
Ground Reference Maneuvers
Eights On Pylons (Pylon Eights)

| First | Previous | Next | Last |

Airplane Flying Handbook

Preface

Table of Contents

Chapter 1,Introduction to Flight Training
Chapter 2,Ground Operations
Chapter 3,Basic Flight Maneuvers
Chapter 4, Slow Flight, Stalls, and Spins
Chapter 5, Takeoff and Departure Climbs
Chapter 6, Ground Reference Maneuvers
Chapter 7, Airport Traffic Patterns
Chapter 8, Approaches and Landings
Chapter 9, Performance Maneuvers
Chapter 10, Night Operations
Chapter 11,Transition to Complex Airplanes
Chapter 12, Transition to Multiengine Airplanes
Chapter 13,Transition to Tailwheel Airplanes
Chapter 14, Transition to Turbo-propeller Powered Airplanes
Chapter 15,Transition to Jet Powered Airplanes
Chapter 16,Emergency Procedures

Glossary

Index

The sighting point or line, while not necessarily on the
wingtip itself, may be positioned in relation to the
wingtip (ahead, behind, above, or below), but even
then it will differ for each pilot, and from each seat in
the airplane. This is especially true in tandem (fore and
aft) seat airplanes. In side-by-side type airplanes, there
will be very little variation in the sighting lines for different
persons if those persons are seated so that the
eyes of each are at approximately the same level.

An explanation of the pivotal altitude is also essential.
There is a specific altitude at which, when the airplane
turns at a given groundspeed, a projection of the sighting
reference line to the selected point on the ground
will appear to pivot on that point. Since different airplanes
fly at different airspeeds, the groundspeed will
be different. Therefore, each airplane will have its own
pivotal altitude. [Figure 6-12] The pivotal altitude does
not vary with the angle of bank being used unless the
bank is steep enough to affect the groundspeed. A rule
of thumb for estimating pivotal altitude in calm wind is
to square the true airspeed and divide by 15 for miles
per hour (m.p.h.) or 11.3 for knots.

Speed vs. pivotal altitude.
Figure 6-12. Speed vs. pivotal altitude.

Distance from the pylon affects the angle of bank.
At any altitude above that pivotal altitude, the projected
reference line will appear to move rearward
in a circular path in relation to the pylon.
Conversely, when the airplane is below the pivotal
altitude, the projected reference line will appear to
move forward in a circular path. [Figure 6-13]

To demonstrate this, the airplane is flown at normal
cruising speed, and at an altitude estimated to be below
the proper pivotal altitude, and then placed in a
medium-banked turn. It will be seen that the projected
reference line of sight appears to move forward along
the ground (pylon moves back) as the airplane turns.

A climb is then made to an altitude well above the pivotal
altitude, and when the airplane is again at normal
cruising speed, it is placed in a medium-banked turn.
At this higher altitude, the projected reference line of
sight now appears to move backward across the
ground (pylon moves forward) in a direction opposite
that of flight.

After the high altitude extreme has been demonstrated,
the power is reduced, and a descent at cruising speed
begun in a continuing medium bank around the pylon.
The apparent backward travel of the projected reference
line with respect to the pylon will slow down as
altitude is lost, stop for an instant, then start to reverse
itself, and would move forward if the descent were
allowed to continue below the pivotal altitude.

The altitude at which the line of sight apparently
ceased to move across the ground was the pivotal
altitude. If the airplane descended below the pivotal
altitude, power should be added to maintain airspeed
while altitude is regained to the point at which the
projected reference line moves neither backward nor
forward but actually pivots on the pylon. In this way
the pilot can determine the pivotal altitude of the airplane.

The pivotal altitude is critical and will change with
variations in groundspeed. Since the headings
throughout the turns continually vary from directly
downwind to directly upwind, the groundspeed will
constantly change. This will result in the proper pivotal
altitude varying slightly throughout the eight.
Therefore, adjustment is made for this by climbing or
descending, as necessary, to hold the reference line or
point on the pylons. This change in altitude will be
dependent on how much the wind affects the groundspeed.

The instructor should emphasize that the elevators are
the primary control for holding the pylons. Even a very
slight variation in altitude effects a double correction,
since in losing altitude, speed is gained, and even a
slight climb reduces the airspeed. This variation in altitude,
although important in holding the pylon, in most
cases will be so slight as to be barely perceptible on a
sensitive altimeter.

Before beginning the maneuver, the pilot should select
two points on the ground along a line which lies 90° to
the direction of the wind. The area in which the
maneuver is to be performed should be checked for
obstructions and any other air traffic, and it should be
located where a disturbance to groups of people, livestock,
or communities will not result.

The selection of proper pylons is of importance to
good eights-on-pylons. They should be sufficiently
prominent to be readily seen by the pilot when completing
the turn around one pylon and heading for the
next, and should be adequately spaced to provide time
for planning the turns and yet not cause unnecessary
straight-and-level flight between the pylons. The
selected pylons should also be at the same elevation,
since differences of over a very few feet will necessitate
climbing or descending between each turn.

 

6-14