Interview Preparation

Q. What are the pressure flight instruments, and how do they work? 

The Pressure instruments are - 

1. Airspeed Indicator (ASI) / Mach Meter (MM)

2. Altimeter

3. Vertical Speed Indicator (VSI)

Pressure instruments gauge atmospheric pressure by utilizing the pitot-static system, a combined sensor setup that identifies:

1. Total pressure (pitot pressure), comprising static and dynamic pressure, which a pitot probe measures.

2. Pure static pressure, measured through either the static port on a pitot probe or a separate static vent.

The difference between these two measurements yields the dynamic pressure, calculated as:

Dynamic pressure = Total pressure - Static pressure

Both dynamic and static pressure measurements underpin the readings displayed on flight instruments.

Q. How does the Air Speed Indicator (ASI) work? 

The Airspeed Indicator (ASI) quantifies dynamic pressure by discerning the variance between the overall pitot pressure assessed within the capsule/diaphragm of the instrument and the static pressure measured within the casing. This dynamic pressure translates into the Indicated Airspeed (IAS) expressed in knots per hour. 

Calibrated to the mean sea level (MSL) density of the international standard atmosphere (ISA), the ASI instrument aligns with a density of 1.225 kg/m³.

Q. What are the Air Speed Indicator (ASI) errors? 

The Airspeed Indicator (ASI) instrument is susceptible to the following errors:

1. Instrument error

2. Pressure error

3. Density error

4. Compressibility error

5. Maneuver induced error

6. Blocked pitot-static system