Flashcards
Pneumatic System
Cards in this deck (26)
- 1Ground Idle, Take off and Cruise compressor pressure and air temperature- Ground Idle (least stressful) : 50psi/180ºC
- Take off: 410 psi/ 410ºC
- Cruise: 150ºC/ 400ºC - 2Engine bleed air tasks- Start the engine (APU or crossbled) - Anti-ice - Motive power for the engine thrust reversers - Cabin pressurization - Pressurization of hydraulic reservoirs - Hot air for rain dispersal - Pressurization of water and waste system
- 3Auxiliary Power Unit (APU) definitionThe APU is primarily designed to provide electrical and pneumatic power by a shaft driven generator and compressor.
- 4APU tasksProvide an independent source of electrical power and compressed air while on ground. Used as a backup provider of power while airborne, assist in in-flight engine re-lighting and to relieve the engines of offtakes load in certain areas of the flight envelope.
- 5Engine Bleed Air Control Steps- Air taken from intermediate stage of high pressures stage - A pneumatically controlled HP SOV regulates pressure around 100 psi and controls supply. - The PRSOV regulates the air to 40 psi before pre-cooler. - Flow through pre-cooler regulated by fan valve which controls the bleed air entering aircraft system.
- 6Why flying at high altitude?- Burns less fuel fora given speed than with the same airspeed at a lower altitude because the reduction of drag due to reduction of density of air.
- Avoid bad weather and turbulence and convective activity occuring in the lower troposphere. - 7Hypoxia DefinitionThe sluggish condition of mind and body produced by insufficient oxygen. The air contains 21% of O2, but the rate at which O2 can be absorbed into the blood depends upon the oxygen pressure. Greater pressure pushes the O2 from the lung alveoli into bloodstream. When reduced, less O2 absorbed
- 8Positive pressure breathingUsed for military airplanes pilots. An increase of the lungs pressure (through a pressurizing suit) increases the efficiency of the lungs.
- 9ECSEnvironmental Control System
- 10Tasks of the ECS- Cope with widely differing temp. conditions - Extract moisture, provide optimum humidity - Ensure sufficient oxygen pressure - Provide suitable conditions for avionics, fuel and hydraulic system.
- 11Cabin pressurization functions- Maintain a cabin pressure altitude of approx. 8000ft or lower regardless the real altitude. - Prevent rapid changes - Circulate air from inside to outside (staled air leads to odors and infections) - Cabin air heated or cooled.
- 12Important aspects of cabin pressurization- Fuselage must withstand forces associated to differential pressure
- Metal fatigue weakens the airframe - 13How can the negative effects of reduced atmospheric pressure be overcomed?- Incresing the pressure of oxygen (cabin pressurization) for large aircrafts.
- Incrasing the quantity of oxygen in the aire mixture (large and medium aircrafts) They also may have portable oxygen for first aid. - 14MSOC stands forMolecular Sieve Oxygen Concentrators
- 15MSOC functioningIt uses air taken from the ECS as a source of gas. Most gases in air have bigger molecules than oxygen which are sieved out until almost only oxygen is left.
- 16MSOC disadvantagesIf the air supply from the engine stops, so does the oxygen supply. A small backup is necessary in order to give time to the pilot to descend to altitudes where oxygen levels are high enough for breathing
- 17Air conditioning: heating or cooling?In the past, heating systems needed at low speed. Now, with military high performances need of cooling systems. Heating is never a problem: use of hot air bled from the engines. Heating still required for cold nights and quick warm-up after freezing conditions on ground
- 18Heat sources giving rise to the cooling problem- Kinetic heating
- Solar Heating
- Metabolic heat from occupants
- Avionics heat loads
- Airframe system heat loads - 19Kinetic heatingAircraft skin heats up due to heat transfer by convection. The skin heats the interior of the aircraft such as cockpit and equipment bays. Kinetic heat loads can be negative.
- 20Solar heatingAffects a military aircraft cockpit through the windscreen and conopy. Equipment bays and civil aircrafts affected indirectly. Significantly affecting cabin and equipment bays on ground standby (rise 20ºC above ambient temp.)
- 21Avionics heat loadsIncrease use of avionics and high density digital electronics have increased the heat load per unit volume of avionics equipment. Air is ducted to these areas for cooling and then re-circulated or dumped overboard
- 22Aircraft system Heat loadsheat produced by all aircraft system (radiation from energy consuming components in the systems). Cooling essential to maintain operational efficiency and prevent chemical breakdown of fluid leading to degradation in their performance cooling
- 23Name: heat sinks- Ram Air cooling
- Fuel cooling - 24Ram Air CoolingRejects aircraft heat load by scooping air from the aircraft bounday layer. The air is forced through a scoop which faces into the external air flow, through a heat exchanger and then rejected overboard
- 25Ram Air cooling disadvantages- Increased aircraft drag, head losses in heat exchanger - Ram air temperature increases with airspeed (kinetic heating) - At high altitude, low density, reduced cooling capacities.
Situation improved by cooling fan (civil aircraft), jet pump (military) - 26Fuel CoolingHigher heat capacity and heat transfer coefficient. Limited: fuel flow variable. Fuel is typically used to cool engine oil, hydraulic oil and gearbox oil.
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- Sistemas Flashcards on Pneumatic System, created by Ana Castilla on 13/06/2020.
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- Ana Castilla
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