Fundamental Aerodynamic PrinciplesAircraft & Engines — DGCA CPL practice questions

All 5 questions — Fundamental Aerodynamic Principles

Aircraft & Engines · DGCA CPL. The correct option is marked on each.

1. Q1. According to the principle of continuity (incompressible flow), a reduction in the cross-sectional area of a streamtube causes:

   • A.A decrease in velocity
   • B.An increase in velocity✓
   • C.An increase in density
   • D.No change in velocity

   Why: With Area × Velocity constant at low subsonic speeds, narrowing the tube must speed the flow up — the basis of aerofoil lift.

2. Q2. Bernoulli's theorem states that for an ideal fluid in steady flow:

   • A.Static pressure plus dynamic pressure remains constant✓
   • B.Static pressure equals dynamic pressure
   • C.Velocity is constant along a streamline
   • D.Density increases as velocity increases

   Why: Static + Dynamic = Total (Pitot) pressure = constant, so an increase in velocity must reduce static pressure — the key to lift.

3. Q3. Changes in air density may be ignored (incompressible flow assumed) below approximately:

   • A.Mach 0.4✓
   • B.Mach 0.7
   • C.Mach 0.84
   • D.Mach 1.0

   Why: Below about M0.4 (≈300 kt) density changes are insignificant, simplifying continuity to Area × Velocity = constant.

4. Q4. An increase in flow velocity over the upper surface of a wing causes the static pressure there to:

   • A.Increase
   • B.Decrease✓
   • C.Stay constant
   • D.Equal total pressure

   Why: By Bernoulli, faster flow = lower static pressure; the upper-surface suction provides most of the lift.

5. Q5. Total pressure is also referred to as:

   • A.Ambient pressure
   • B.Pitot pressure✓
   • C.Vapour pressure
   • D.Gauge pressure

   Why: The sum of static and dynamic pressure is Total or Pitot pressure — what the pitot tube senses.