t-39 - Chief of Naval Air Training

T-39 FLIGHT PREPARATION STUDENT GUIDE
G-4
(7) VMCG: The speed at which the aircraft can be controlled on the ground with a failed
engine and by use of aerodynamic controls alone. The speed is based on the failed
engine windmilling, takeoff thrust on the good engine, the nosewheel off the runway, and
use of ailerons and rudder to maintain directional control within 25 feet of the desired
path.
(8) VB: The design speed for maximum gust intensity.
(9) VF: The design flap speed.
(10) VMO: The maximum operating limit speed.
(11) VSO: Stall speed or the minimum steady flight speed in the landing configuration.
(12) VREF: Final approach speed at the 50 feet threshold height in a normal landing
configuration.
(13) Balance Field Length: The distance within which the aircraft can either accelerate
to V1 and then stop, or accelerate to V1 and continue to a height of 35 feet with one
engine cut at V1.
(14) Critical Field Length: The distance within which the aircraft can either accelerate
to refusal speed and then stop, or accelerate to refusal speed and continue takeoff while
one engine is failed at refusal speed. All available runway will be required to get the
aircraft airborne.
(15) Second segment climb: The aircraft must be capable of maintaining a climb
gradient of at least 2.4 % (24 feet per 1,000 feet) with one engine inoperative and the
other engine at takeoff thrust.
(16) Third segment climb: May be used for level-flight acceleration at 800 feet above
the airport pressure altitude to final takeoff climb speed.
(17) Engine Pressure Ratio: This is the ratio of the turbine discharge total pressure to
compressor inlet total pressure. Turbine discharge total pressure is an average pressure
taken by four probes manifolded together immediately downstream of the turbine.
Compressor inlet total pressure is measured by two electrically heated pitot pressure
heads, one for each instrument, mounted on the leading edge of the vertical stabilizer.
(18) RCR: A measure of tire to runway friction coefficient. RCR is given as a whole
number. This value is used to define the braking characteristics for various runway
surface conditions. The reported RCR is therefore a factor in determining any
performance involving braking, such as critical engine failure speed and refusal speed.
Some airfields report runway braking characteristics in accordance with ICAO
documents, that is, “good”, “medium”, and “poor”. In order to relate these ICAO