It must be emphasized that the stalling speed of a particular airplane is not a fixed value for all
flight situations. However, a given airplane will always stall at the same angle of attack
regardless of airspeed, weight, load factor, or density altitude. Each airplane has a particular
angle of attack where the airflow separates from the upper surface of the wing and the stall
occurs. Each airplane has only one specific angle of attack where the stall occurs. The airplane
can be stalled in straight and level flight by flying too slowly. As the airspeed is being
decreased, the angle of attack must be increased to retain the lift required for maintaining
altitude. The slower the airspeed becomes, the more the angle of attack must be increased.
Eventually an angle of attack is reached which will result in the wing not producing enough lift
to support the airplane and it will start settling. If the airspeed is reduced further, the airplane
will stall since the angle of attack has exceeded the critical angle and the airflow over the wing is
In naval aviation, there is great importance assigned to precise control of an aircraft at high angle
of attack conditions. Safe operation in carrier aviation demands the ultimate in precision flying
at low airspeed. The aerodynamic lift characteristics of an airplane must be fully understood by
the student naval aviator as well as the seasoned "fleet pilot" for obvious safety reasons.
Additionally, mission requirements and their execution may depend on the pilot's own
capabilities and grasp of these basic concepts.
During flight maneuvers, landing approach, takeoff, etc. the airplane will stall IF THE
CRITICAL ANGLE OF ATTACK IS EXCEEDED. The AIRSPEED at which stall occurs
will be determined by weight, load factor, altitude, and configuration, but the stall angle of attack
remains unaffected. At any particular altitude, the indicated stall speed is a function of weight
and load factor. An increase in altitude will produce a decrease in density and an increase in true
airspeed. Also, an increase in altitude will alter compressibility and airflow viscosity, which will
cause the indicated stall speeds to increase.
Modern airplanes are characterized by having a large percentage of their maximum gross weight
as fuel. Most Navy inventory aircraft carry 25-40 percent of their total gross weight in this
manner. Hence, the gross weight and stall speed of the airplane can vary considerably throughout
the flight. A general "rule of thumb" is that a 2% change in weight will cause a 1% change in
stall speed. Note that for the T-34C, a full load of fuel is only approximately 18% of the
aircraft's gross weight. Fuel burnoff will consequently have a diminished effect on stall speed as
compared to most naval aircraft in the inventory.
Load factor/centrifugal force. Turning flight and maneuvers produce an effect on stall speed,
which is similar to the effect of weight. The stalling speed of an airplane is higher in a level turn
than in straight and level flight. This is because centrifugal force is added to the airplane's
weight, and the wing must produce sufficient additional lift to counterbalance the load imposed
by the combination of centrifugal force and weight. In a turn, the necessary additional lift is
acquired by applying back pressure to the elevator control. This increases the wing's angle of
attack, and results in increased lift. As stated earlier, the angle of attack must increase as the
bank angle increases to counteract the increasing load caused by centrifugal force. If at any time
during a turn the angle of attack becomes excessive, the airplane will stall. Thus, the aircraft in a
INTRODUCTION TO T-34C AERODYNAMICS 2-9