12.36.6(d) . drain holes, heating, and pitot cover; 

Drain holes – any water from rain or condensation which collects in the tube can drain out through drain holes
Heating – an element is fitted to the pitot head to clear potentially blocking ice formation
Pitot cover – prevents damage or blackage of pitot tube ffrom insects, dust, rain

12.36.6(c) . combined pitot-static head; 

12.36.6(b) . pitot tube; Sub Topic Syllabus Item 

Pitot tube
– mounted on the wing
– enables total pressure to be measured

12.36.6(a) . static vent(s); 

Static vent
– provides for sensing static pressure

12.36.6. Explain the operation of 
 a pitot-static system, including:











(a) . static vent(s);







- provides for sensing static pressure 










(b) . pitot tube; 






           

           

- mounted on the wing

- enables total pressure to be measured



(c) . combined pitot-static head; 





(d) . drain holes, heating, and pitot cover;


 Drain holes - any water from rain or condensation which collects in the tube can drain out through drain holes
Heating - an element is fitted to the pitot head to clear potentially blocking ice formation
Pitot cover - prevents damage or blackage of pitot tube ffrom insects, dust, rain



(e) . alternate pressure source.


 - enables the pressure inside the cabin to be sensed in the event of ice or other stuff blocking the external vents
- in unpressurised aircraft the cabin pressure is only slightly less than the external atmospheric pressure so the instrument readings will be only slightly errored if the alternate source is selected 



 
        

         
    

12.36.4. Describe static pressure and dynamic pressure, and the main factors which affectthem. 

Static Pressure
– the air exerts a pressure equally in all directions at any point in the atmosphere (static pressure)
– results from the weight of all the air molecules above that point pressing down
– not affected by any air movement

Dynamic Pressure
– any solid body which moves relative to the air surrounding it experiences an additional pressure on the surfaces facing the directin of movement
– this is dynamic pressure and is over and above the static pressure
Depends upon
– the Velocity of the body relative to the air
– the Density of the air

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;