Velocity and pressure changes

T-45A/C TS, ADV & IUT Aero-02

High-Speed Flight

Sg 1, fr 5

(4) Spread at the speed of sound

Temperature and

Speed of Sound

(a) Speed of sound depends on air

Relationship

temperature, i.e., at 59 degrees F, the

sea level speed of sound is 662 knots;

at 90 degrees, it is 687 knots; at 32

degrees, it is 643 knots

(b) Speed of sound decreases with

altitude

Compressibility effects occur at lower IAS as altitude

increases

Relationship described by Mach number (the ratio of

true airspeed to the speed of sound)

Compressibility effects (assume high thickness-

to-chord ratio and rounded large radius leading

Sg 1, fr 7

edge)

Fig 1: Subsonic Flow

About an Airfoil

Local sonic flow on airfoil at speed less than

Sg 1, fr 8

Mach 1

Critical Mach Number

Critical Mach number 1.7.1.4.6

(1) Flight Mach number at which the first sonic

flow on the aircraft occurs

(2) Important reference point because it is the

beginning of the transonic flight regime

Sg 1, fr 10

(a) Airflow is mixed--part subsonic, part

Fig 2: Compression

supersonic

Wave Formation

(b) 0.8 Mach in T-45

(i) Occurs on wingtips

(ii) Occurs on landing gear door blister

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(9-99) Original