T-34 Questions - Basic Aerodynamic Principles Flashcards
State the continuity equation. What are the variables in the equation? When may the density variable be cancelled?
p1A1V1=p2A2V2 p is density. A is cross sectional area, and V is velocity. p may be canceled if altitude remains constant and airflow is subsonic.
According to the continuity equation, if the velocity of an incompressible fluid is to double, what must happen to the cross sectional area of the flow?
reduced by one half
State Bernoulli’s equation. Under what conditions does total pressure remain constant? If PT is constant, how do q and PS relate?
Pt=Ps+q Total pressure remains constant in a closed system. Ps is inversely related to q if Pt is constant.
Describe how the pitot static system works using Bernoulli’s equation.
The pitot static system consists of a total pressure sensor, the pitot tube; a static pressure sensor, the static port; and a mechanism that determines the difference between the two in order to calculate dynamic pressure which is displayed in the cockpit as indicated airspeed. (q=Pt-Ps)
For a given altitude, what is true about the pressure in the static pressure port of the airspeed indicator?
For a given altitude, the pressure in the static pressure port of the airspeed indicator is constant fro all airspeeds and all angles of attack.
Define IAS and TAS. What is the equation relating the two?
IAS is the instrument indication for the dynamic pressure the aircraft is creating during flight. True airspeed (TAS) is the actual velocity at which an aircraft moves through and airmass. formula
When will IAS equal TAS? How do IAS and TAS vary with increases in altitude?
IAS will equal TAS when p=po As altitude increases with a constant IAS, TAS will increase.
What must a pilot do to maintain a constant true airspeed during a climb?
Decrease the IAS as altitude increases.
An airplane is flying at a six nautical mile per minute ground speed. If it has a 100 knot tailwind, what is its TAS?
260 TAS
An F/A-18 is flying at an eight nautical mile per minute ground speed. If it has a TAS of 600 knots, does it have a headwind or tailwind and how much of one?
120 knot headwind.
Define Mach number and critical Mach Number (MCRIT).
Mach number is the ratio of the airplane’s TAS to the local speed of sound (LSOS). Critical Mach number is the free airstream mach number (<1) that produces the first evidence of local sonic flow.
A T-45 is climbing at a constant 350 KIAS. What would be the effect on Mach Number as it climbs? Why?
Mach number increases because TAS increases and the local speed of sound decreases.
