Hydraulic SystemsAircraft & Engines — DGCA CPL practice questions

Question 1 of 5

Pascal's law states that pressure applied to a confined fluid:

A.Acts only downward

B.Is transmitted equally in all directions

C.Decreases with distance

D.Varies with fluid colour

All 5 questions — Hydraulic Systems

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

Q1. Pascal's law states that pressure applied to a confined fluid:
- A.Acts only downward
- B.Is transmitted equally in all directions✓
- C.Decreases with distance
- D.Varies with fluid colour
Why: Equal transmission of pressure lets a small force on a small piston create a large force on a large piston — at the cost of travel distance.
Q2. Skydrol (phosphate-ester) hydraulic fluid is coloured:
- A.Red
- B.Purple✓
- C.Blue
- D.Green
Why: Phosphate-ester fluid is purple, fire-resistant, used with butyl seals; mineral-based fluid is red with neoprene seals. They are NOT interchangeable.
Q3. A hydraulic accumulator contains:
- A.Fluid only
- B.Fluid on one side of a piston/diaphragm and compressed nitrogen on the other✓
- C.Compressed oxygen
- D.A filter element
Why: The nitrogen charge stores energy: damping pressure fluctuations, meeting peak demands and providing emergency pressure.
Q4. Hydraulic reservoirs on jet aircraft are often pressurised with bleed air to:
- A.Cool the fluid
- B.Ensure positive fluid supply to the pumps and prevent foaming at altitude✓
- C.Filter the fluid
- D.Operate the brakes directly
Why: Reservoir pressurisation stops pump cavitation and fluid foaming in the thin air at altitude.
Q5. The most common pump type on large aircraft hydraulic systems is the:
- A.Constant delivery pump with automatic cutout
- B.Constant pressure (variable volume) pump✓
- C.Hand pump
- D.Centrifugal pump
Why: Constant-pressure pumps vary their output volume automatically to hold system pressure, removing the need for a cutout valve.