The penetration is a procedure used by aircraft to effect a safe and expeditious letdown
from high altitude under instrument conditions. Normally, the penetration is begun from an
initial altitude over a designated radio facility. Upon completion, the aircraft is in a position to
make a landing at a selected field. However, for training purposes, only the airwork procedures
will be taught by assigning a penetration heading and level off altitude with no reference to a
You will be given the aircraft approaching the penetration site. Your instructor will
assign headings to fly to position the aircraft over the penetration site with a minimum of one
minute on the penetration heading prior to commencing. Once you have taken control of the
aircraft, complete the items of the Penetration Checklist, reporting each item to your instructor.
The Penetration Checklist is as follows:
Oxygen 100% (White Lever).
Fuel state checked.
Cockpit defog control As required (if required; request instructor to check).
When the above procedure has been completed and when established on your penetration
heading, commence the penetration descent, when cleared by your instructor, by:
Reducing the PCL to idle while simultaneously lowering the nose on the gyro
13 15 degrees nose down to initiate the descent.
Trim left rudder and nose down elevator as the aircraft accelerates.
As the airspeed approaches 180 knots, trim the aircraft, and maintain 180 knots.
The rate of descent on the vertical speed indicator will be about 4000 feet per
minute. The nose attitude will be approximately 11 13 degrees nose down when
trimmed at 180 knots.
Upon reaching an altitude of 10,000 feet, commence a left 30º AOB descending turn for
210º. The nose will have to be adjusted up approximately 2º and trimmed up because of the
slight loss of vertical lift in the turn; otherwise the nose will fall slightly and the airspeed will
increase. Upon rolling out of the 210º turn, vertical lift is increased. Thus, it will require
forward stick, slight nose down attitude (approximately 2º), and down elevator trim to maintain
180 knots. Immediately upon rolling wings level, check the clock and fly a straight leg for one
minute. Upon completion of this one minute timing, execute a shallow turn (15º AOB) to the
reciprocal of the initial penetration heading.
Upon reaching 1000 feet above the assigned level off altitude, increase power to
250 ftlbs. and slow the rate of descent by smoothly raising the nose halfway (5 7 degrees
nose down) toward the level flight attitude. Maintain this attitude momentarily, allowing the
aircraft to decelerate. Once the VSI is stabilized, raise the nose on the attitude gyro to set up a
BASIC INSTRUMENTS FLIGHT PROCEDURES 3-27