12.36.2. Identify the three basic instruments which rely on air pressure for their operation.

Airspeed Indicator – relates the diffrence between total pressure and static pressure to the speed through the air

Altimeter – converts static pressure to altitude

Vertical Speed Indicator – relates the rate of change of static pressure to a rate of climb or descent

12.34. Engine Instruments

12.34.2(f) . fuel quantity gauges. 

– two main types,Variable resistance (Ratiometer) and Capacitance Indicators,
– light aircraft normally use Ratiometer which makes use of a float in the tank which moves up or down with the fuel level. This varies the resistance in an electrical circuit and this is used to give a reading on the instrument,
Capacitance Indicators measure the capacitance between two probes. The capacitance changes as the ratio of fuel to air in the tanke changes. One or more sets of probes may be used.

12.34.2(e) . outside air temperature gauges; 

12.34.2(d) . vacuum gauges; 

not an engine instrument. The vacuum gauge uses a Boudon tube to measure the amount of vacuum (suction) less than atmospheric pressure which is produced by the vacuum pump in order to drive vacuum powered instruments.

12.34.2(c) . direct reading oil pressure gauges; 

– a thin tube takes oil from after the oil pump to the instrument. A Boudon tube is used to provide the indication on the instrument.

12.34.2(b) . manifold pressure and boost gauges; 

12.34.2(a) . tachometers (rpm) gauges (centrifugal and drag cup); 

12.34.2. Describe the function and principle of operation of the following instruments:

12.32. Lubrication Systems - Engines