38 Design Features Flashcards
How does the T38 having a symmetrical wing affect lift and drag?
Symmetrical wings produce less lift than cambered wings. There is less drag with a symmetrical wing
How does the T38 having a low aspect ratio affect lift and drag?
Low aspect ratio wings produce less lift and have a higher stall airspeed at any given AOA.
They have lower parasite drag and better yaw stability, but higher induced drag
Does a low aspect ratio wing require a lower or higher AOA for max lift?
Higher
Is a low aspect ratio wing less or more sensitive to AOA changes?
Less sensitive
How does the T38 having a wing taper affect lift and drag?
A wing taper reduces induced drag and moves the lift distribution by moving the center of wing loading closer to the wing root.
How does a wing taper affect where a wing stalls first?
A wing with wing taper causes the wing tips to stall first, which can cause sudden rolls near stalls
What 3 things about the T-38’s wing design affect its high speed flight characteristics and why?
- Symmetrical Wing
- Low Aspect Ratio
- Wing Taper
There is less parasitic drag and lift
What is the key factor when determining the speed of sound?
Temperature
What is mach number (equation)?
TAS/Speed of Sound
What happens to Mach number as you increase in altitude?
TAS remains constant while Mach number increases
What happens to CAS/IAS as you increase altitude?
CAS/IAS decrease as altitude increases
What is the critical mach number?
The lowest freestream speed at which some point in the air flow around the aircraft reaches the speed of sound
What is force divergence mach number?
The speed where wave drags begin throughout the transonic regime (5-10% above critical mach)
What is wave drag?
Shock waves decrease lift and increase parasitic drag due to air slowing when shock waves decelerates the air flowing around it
What happens to the T38’s flight characteristics at transonic and supersonic airspeeds and why?
The T38 becomes more stable and less maneuverable
Due to the Aerodynamic center is moved farther AFT of the CG, creating greater longitudinal pitch stability
What is aspect ratio?
The actual
aspect ratio (AR) of a wing is equal to the wingspan (b) squared, divided
by the wing area (S).
What is the T38s aspect ratio?
3.75
What is the 38s wing taper ratio?
0.2
What is wing taper ratio?
The reduction in chord length from root to tip
What is the T38s wing sweep back angle?
24 degrees
How is wing sweep measured?
The quarter chord sweep angle, which is
measured between the lateral axis and a line 25 percent of the way back from the leading edge of the wing
How does the area rule effect the T38 and what is the area rule?
The cross-section area of the aircraft should change gradually and smoothly as you move
from the nose to the tail. This design minimizes the need for abrupt changes in airflow and the associated drag
What is the definition of transonic flow?
Mixed airflow around the aircraft that is part subsonic and part supersonic
