The rate at which the altimeter moves helps to determine pitch
attitude. A very slow movement of the altimeter indicates
a small deviation from the desired pitch attitude, while a
fast movement of the altimeter indicates a large deviation
from the desired pitch attitude. Make any corrective action
promptly, with small control changes. Also, remember that
movement of the altimeter should always be corrected by
two distinct changes. The first is a change of attitude to stop
the altimeter movement; the second is a change of attitude to
return smoothly to the desired altitude. If altitude and airspeed
are more than 100 feet and 10 knots low, respectively, apply
power in addition to an increase of pitch attitude. If the
altitude and airspeed are high by more than 100 feet and 10
knots, reduce power and lower the pitch attitude.

There is a small lag in the movement of the altimeter;
however, for all practical purposes, consider that the altimeter
gives an immediate indication of a change, or a need for
change in pitch attitude. Since the altimeter provides the
most pertinent information regarding pitch in level flight, it
is. considered primary for pitch.

Vertical Speed Indicator (VSI)
The VSI gives an indirect indication of the pitch attitude of
the helicopter and should be used in conjunction with the
other pitch instruments to attain a high degree of accuracy
and precision. The instrument indicates zero when in level
flight. Any movement of the needle from the zero position
shows a need for an immediate change in pitch attitude to
return it to zero. Always use the VS1 in conjunction with
the altimeter in level flight. if a movement of the VSI is
detected, immediately use the proper corrective measures
to return it to zero. if the correction is made promptly, there
is usually little or no change in altitude. If the needle of the
VSI does not indicate zero, the altimeter indicates a gain or
loss of altitude.

The initial movement of the vertical speed needle is
instantaneous and indicates the trend of the vertical movement
of the helicopter. A period of time is necessary for the VSI to
reach its maximum point of deflection after a correction has
been made. This time element is commonly referred to as
instrument lag. The lag is directly proportional to the speed
and magnitude of the pitch change. When employing smooth
control techniques and small adjustments in pitch attitude are
made, lag is minimized, and the VSI is easy to interpret.

Overcontrolling can he minimized by first neutralizing the
controls and allowing the pitch attitude to stabilize, then
readjusting the pitch attitude by noting the indications of the
other pitch instruments.

Occasionally, the VSI may be slightly out of calibration.
This could result in the instrument indicating a slight climb
or descent even when the helicopter is in level flight. If the
instrument cannot he calibrated properly, this error must be
taken into consideration when using the VSI for pitch control.
For example, if a descent of 100 feet per minute (fpm) is the
vertical speed indication when the helicopter is in level flight,
use that indication as level flight. Any deviation from that
reading would indicate a change in attitude.

Airspeed Indicator
The airspeed indicator gives an indirect indication of
helicopter pitch attitude. With a given, power setting and
pitch attitude, the airspeed remains constant. If the airspeed
increases, the nose is too low and should be raised. If the
airspeed decreases, the nose is too high and should he
lowered. A rapid change in airspeed indicates a large change
in pitch attitude, and a slow change in airspeed indicates a
small change iii pitch attitude. There is very little lag in the'
indications of the airspeed indicator. if, while making attitude
changes, there is some lag between control application and
change of airspeed, it is most likely due to cyclic control lag.
Generally, a departure from the desired airspeed, due to an
inadvertent pitch attitude change, also results in a change in
altitude. For example, an increase in airspeed due to a low
pitch attitude results in a decrease in altitude. A correction in
the pitch attitude regains both airspeed and altitude.

Bank Control
The bank attitude of a helicopter is the angular relation of
its lateral axis to the natural horizon. To maintain a straight
course in visual flight, keep the lateral axis of the helicopter
level with the natural horizon. Assuming the helicopter is in
coordinated flight, any deviation from a laterally level attitude
produces a turn. [Figure 6-4]

Attitude indicator
The attitude indicator gives a direct indication of the bank
attitude of the helicopter. For instrument flight, the miniature
aircraft and the horizon bar of the attitude indicator are
substituted for the actual helicopter and the natural horizon.
Any change in bank attitude of the helicopter is indicated
instantly by the miniature aircraft. For proper interpretation
of this instrument, imagine being in the miniature aircraft. If
the helicopter is properly trimmed and the rotor tilts, a turn
begins. The turn can be stopped by leveling the miniature
aircraft with the horizon bar. The ball in the turn-and-slip
indicator should always be kept centered through proper
pedal trim.

The angle of bank is indicated by the pointer on the banking
scale at the top of die instrument. [Figure 6-5] Small bank
angles, which may not be seen by observing the miniature
aircraft, can easily he determined by referring to the banking
scale pointer.