Airframe Mechanical System
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Here in this report we have discussed various design and performance parameters of aircraft. In a basic way we have discussed so many things in this report. The motive is to make a clear view on various aspects of aircraft. Here in this topic we have discussed mainly four things. These four things are the design and operation of a basic hydraulic system, design and operation of cabin environmental control system, operation and layout of aircraft protection system and electrical power distribution sub-systems and components used in aircraft.
One by one these above stated parameters are discussed in detail format,
Explore the Design and Operation of a Basic Hydraulic System
1. The most important and the common mechanism are used in every aircraft for this new era of technology is the hydraulic system. Not only in aircraft mechanisms, it is used in various other aspects also for different requirements. Here in this report for our requirement we are discussing about various parameters considered for the operation of hydraulic systems in aircraft. The basic requirement of a hydraulic system in aircraft is to actuate various components attached with the subpart of a craft.
There are so many reasons behind the extreme use of hydraulic systems in aircraft. Only in hydraulic system we can get high pressure or force output by the help of very small amount of oil. This is also a very robust system, having a failure rate very less. For an aircraft there the needs are to control the brakes, landing gears and wing movement for lifting up or down, these all things are performed by the help of hydraulic systems. Still the entire hydraulic system is heavier than pneumatic system but the extreme use against its use is for its reliability.
The hydraulic system works on a very basic principle based on hydrodynamics. Hydrodynamics are the topic where the pressurized oil is used to do mechanical works. The basic principle is based on Pascal’s law of hydrodynamics. It states that “Pressure exerted in a confined incompressible fluid is transmitted equally in all the direction throughout the fluid such that pressure ration remains same”.
The basic principal is just like a manual actuating hydraulic pump. An image is included in it to understand, what the hydraulic is actually?
regarding its features. The fluid used in the hydraulic system is not only for pressuring purpose, it is used for the lubrication of the equipments inside the mechanism. It also provides the cooling effect to the system. Basically in hydraulic systems three types of fluids are used these are Vegetable, Mineral and Synthetic oil. These oils have their own properties and have their specific requirements.
- For vegetable oil it was used in older aircrafts, now this days the use of vegetable oil as a fluid in hydraulic system is not so common. The vegetable hydraulic oil is made of alcohol and castor oil, the color of this fluid is blue. It provides a high corrosion.
- The mineral oil is largely used in so many hydraulic applications in aircraft. The behavior of this fluid is very stable. It does not change its state under high temperature also. The lubricating property of this fluid is also very good for this kind of fluid. It is colored red, and one thing is to be consider, it is very inflammable.
- Synthetic hydraulic fluid has one of the best properties among all the hydraulic oils. But the main problem is that, it has a very corrosion effect on the hydraulic system equipments. Except this parameter this kind of fluids having very high lubrication effect and low temperature coefficient for viscosity.
The power supply system of a hydraulic actuator in an aircraft consists of various equipments like pump, reservoir, valves etc. For the use of this hydraulic mechanism any higher management system is not required. A very common switching with the help of a pump or engine is used to power the whole system.
Fig: Hydraulic systems on aircraft
2. Landing gear is one of the important part and mechanism in the aircraft operation. At the time of takeoff and landing the landing gear plays the most important role. The whole operation of the landing gear is performed by the hydraulic systems. After taking off from the runway and before landing on the runway it will perform all this things. The basic parameters of a landing gear are to be taken into consideration is,
- Dead load of the entire aircraft
- Absorbing the force exerted at the time of landing
- Vibration damping at the runtime
- Providing the brake and the steering mechanism to the wheels
For landing mechanism, the pilot needs to actuate the landing switch which powers on the actuator pump for the hydraulic fluid. Fluid flows through the check valve and poured with a high pressure at the desired cylinder. And lift it up or down. By lifting it up and down the entire process is comes into play at the time of takeoff and landing. At the reaction time when the aircraft is in air then pilot actuates the pump to make a flow in opposite direction and automatically the landing gear lifts up. This is the very basic landing gear operation. For steering purpose also in aircraft hydraulic mechanism is used. The reason behind it is that kind of high pressure and force cannot be access by any other manual mechanism.
Fig: Hydraulic actuating landing gear of an aircraft
3. For flying control system also, the pilot needs to lift up or lift down some parts attached to the wings of the aircraft. The whole procedure is very complex. But the system used is very simple. At the time of flight is air there is the only mechanism used to steering the air craft by using the tail wing movement. This is also done by the hydraulic mechanism. All these things are performed by hydraulic power pack equipped with motor, actuators and valves. For each section there are individual power pack solutions.
Design and Operation of Cabin Environment Control Systems
1. One of the most important topics is the air circulation in terms of ventilation into an aircraft. The ventilation system is very much important for the passengers inside any aircraft. Not only the ventilation is required, along with then ventilation the circulation of air is very important for an aircraft. At the time of pouring the air from outside at the time of flight it will be kind of that, the air entering into the craft is so cold. That is why a proper circulation mechanism is required to maintain an ambient condition in it. On the context of air ventilation, the circulation is being done throughout the total length of the cabin. The flow of air maintained by the diffusers located at the ceiling of any aircraft. The intake of air from the outside is being maintained by considering the ambient condition into the cabin.
The need of the circulation done for maintaining an ambient temperature also. To maintain the temperature at the cabin so many calculations are required for heat exchange analysis. That has been shown in the air conditioned and pressurized section of this report. By the help of these mechanisms using outlet ducts the intake is being done in any aircraft and with the help of several ducts the circulation is done.
Fig: The air flow in the aircraft
2. In this part of this report we have discussed the oxygen supply mechanism into an aircraft on normal and emergency condition. In a normal condition at the time of flight the oxygen is being supplied to the cabin from the engine turbine blades. A high pressure intake is being done with the help of those turbine blades and the high pressure air circulated by several ducts into the cabin. The bleed air contains fresh oxygen that comes into the cabin for normal respiration of the passengers, pilots and the staff member.
Along with this there might be some kind of situation may occur, the normal ventilation oxygen supply will not work at that time to prevent such uncertain condition we can see for modern aircrafts there are some kind of inbuilt oxygen generation chemical arrangements are incorporated. That will help to make sufficient oxygen. These are the general arrangement for oxygen circulation.
In case of an emergency situation, the circulation of oxygen is the critical thing is to be considered. The emergency oxygen demands are occurring at a very high altitude. When there is not the possibility of taking oxygen from outside as well as to produce oxygen by oxygen generator. At that time a pre pressurized tank of oxygen is used for breathing purpose of the passengers and the crew members. This kind of pre filled or pre pressurized oxygen tanks are the feature for every commercial flights. For these kinds of emergency situations an oxygen mask is available under each seat of the passengers. At a very high altitude with a extensively low air pressure this mechanism works. All this process is not applicable for a high extend of time. Since it is an emergency feature that is why, it sustained for a very short time on that time being the pilot needs to get a certain altitude, where there is no need of external oxygen requirements. In every aircraft for passengers the supply of oxygen in their mask is typically made for a service of 15 to 20 minutes. This is all about the emergency situation oxygen demand and its supply.
Fig: Air circulation in the aircraft cabin
3. Here the pressurization and the air conditioning principals are discussed in this part of this report. In general the pressurization means the increase the pressure at any certain region. Since the air pressure falls at higher altitude that is why the air pressurize arrangement is necessary for every aircraft. The need of this is to make a good environment for human breathing. In general an air craft is specified to a pressure about its sustainable pressure. For light aircraft it is 3-5 psi, for large reciprocating engine aircraft it is 5.5 psi and for turbine powered transport aircraft it is 9 psi. This pressurization method is applied for the air conditioning purposes. Pressurization is done by the compressor of the turbocharger, the hot air is then cooled by the help of inter cooler arrangements. After that the discharge is controlled into the cabin. There are also some outflow valves; they control the air pressure at the cabin by allowing the pressurized air into the cabin. Some dump valves are also there to release the maintained air pressure into the cabin when it lands. For emergency purpose there are negative pressure releasing valves are in use which do not allow the pressure to fall from a certain limited value. This is all about the maintaining the air pressure and air conditioning.
Operation and Layout of Aircraft Protection System
1. The precipitation of ice at the time of flight is a very common but worst condition ever faced by pilots. It is such a condition where all over the aircraft’s ice precipitation areas are covered with ice. It happens only when the flight height is very high and the temperature is very less. At that time if the precipitation is more in air or the clouds are extensively precipitated then, the ice condensation is a common matter. Still it is a common matter; the aircraft needs to get rid of such kind of situation. The importance is that, from ice formation on the external surface of an aircraft the aerodynamic shape will hamper. For this reason, some anti-icing arrangements are there in an aircraft. These are designed to remove the ice from outer surface of the flight. Since it is an emergency condition, it works at that time only. Some channels are made inside the external wall in between them some kind of anti icing fluid are there. These anti icing fluids prevent to form ice. For now, there are so many features are there to prevent this kind of problems like hot air flow by electric heaters.
2. One of the most basic hazards in any kind of aircraft is the fire in the cabin of a aircraft. The fire in any kind of aircraft has broadly classified to some parts, like galley fire, electrical fire, lavatory fire, waste container fire, overhead compartment fire, seat fire and passenger PED fire etc. The electrical fire is a kind of fire which is occurred by the electrical short circuit. The lavatory fire is kind of situation when burnt cigarettes being placed in waste paper bin from that source fire can be placed. Overhead compartment fire is kind of that which occurs for passengers hand bag material due to the presence of lithium ion batteries in their bags.
To prevent this kind of situations there are so many equipments are there in each aircraft. Some kind of optical smoke detectors are provided in each aircraft to detect the fire or smoke. Some portable fire extinguishers are also mounted on the inner wall of the aircraft. Some automatic fire extinguishers are also provided. Fire protection suits, gloves and goggles are also there in an aircraft. For some extensive fire there are fire blankets are used.
Fig: Fire protection system incorporated in aircraft
3. We have gone through the various emergency situations like ice formation and the fire in the aircraft. Now this part of this report says about the various measures are to be taken and the equipments are used to make a suitable condition on such kind of uncertain situations. Here we are analyzing the operations of the various equipments used here.
For the ice formation on the outer surface of the aircraft it will hamper the aerodynamic shape of the craft and for flight it may cause some difficulties. To get rid of such kind of situations there are so many arrangements are incorporated with an aircraft like,
- Pilot tube is being heated
- Static port heating is also done
- Fuel vents are also heated with the help of hot flue air
- Stall warning sensors are also heated for their general operation
- Some kind of thin graphite foil heating tape is also attached in some ice prone areas for preventing this issue.
Another method is also applied for now, that is TKS ice protection mechanism. It is manufactured by CAV ice protection is based on the fluid base ice protection system. This mechanism is extremely used in the ice prone areas of aircraft.
Fig: The ice prevention system in typical aircraft
For fire protection system, various fire extinguishers are used in air craft. Various fire and smoke detection equipments and sensors are there for detecting fires and smoke. The basic principles of extinguishing fire are,
- First the fire safety crew members are needed to find the source of the fire and the smoke.
- Then they need to extinguish the fire as soon as possible completely
- After the fire gets turned off the whole settlements is required
- The extinguishers need to be refill
- If extensive fire is there in the cabin at that time the only option is to land the craft from air and exit from the aircraft
These are the basic operational guide for preventing the fire in an aircraft.
Electrical Power Distribution Sub-Systems and Components Used in Aircraft
1. The most important subsystem of any aircraft is its fuel and fuel system. It is not that much easy system like any other crafts. In aircrafts the main complex thing is maintaining of pressure and temperature of the fuel. The purpose of any aircraft fuel system is to store the fuel, and to send it to the proper position. Fuel system should contain some of the parameters like fuel pressure, fuel flow, warning signal and quality. Typically, the fuel system in any aircraft is kind of gravity feed system and the pressurized system. The components are to be consider at the time of describing the fuel are, pump, tanks, lines valve, fuel flow meters, filters, quantity indicators, warning component, fuel drains and heaters.
Fuel pumps are basically used to transfer the fuel from one tank to another tank and for some cases to provide sufficient amount of fuel to the engine also the pumps are used.
The tank is the portion for storing the fuel on to the aircraft. It is basically located at the wings of an aircraft.
Line valves are the valves at the fuel lining provides a one-way fuel flow for the engine requirement.
Fuel flow meter is the meter used to detect the flow of fuel into the engine.
Filters are also provided in the fuel line which provides a clean filtered fuel to the engine.
Quantity indicator is the indicator or the meter which shows the amount of fuel in the aircraft.
Warning component is the component used to show warning signal for low level of fuel or any other warnings.
Fuel drains and the heaters are also provided for the draining purpose and heating purpose of the fuel for better combustion.
Fig: The fuel storage and circulation system in aircraft
2. Basically three kinds of fuels are used in aviation purposes they are, Aviation gasoline, Aviation Turbine, Aviation Turbine Gasoline. The basic specifications of such kind of fuel for gas turbine engine and piston engine should contain these parameters,
- It should have the property of flowing at all circumstances
- It should have the ability of proper combustion
- It should have high calorific value
- The purity is to be maximum
- It should not damage the engine
- It should have low fire hazard
At the time of selecting the fuel some kind of characteristic are to be consider these are volatility, vapor lock.
Gasoline vapor pressure: 5.5-7 psi at 100F
Jet A vapor pressure 0.1 psi at 100 F
Jet B vapor pressure 2-3 psi at 100F
Along with this a safe handling is very much important for refueling and fuel handling. For that reason some safety standard is to be maintain these are,
- At the time of refueling an aircraft only the professional trained personals are to be allowed for that particular job.
- At the time of refueling for emergency purpose we need to be prepared for all uncertain situations, for that reason emergency equipments are needed to be in front of those personals.
- For fueling purpose fuel hoses are to be joint properly.
- It should be check that, there is not any kind of open fire sources near the location of the fueling.
- The tank vehicle from which the fueling id going on should be in ignition off mode.
These are the safe handling parameters to be taken into consideration at the time of fuel handling.
3. The main airframe fuel system is described here in detail for better understanding. In this part of this report the basic parts on any aircraft for fuel flow system is being shown. The main components are.
Pump: The pump is the only one most important item for fueling purpose and to provide the engine a sufficient amount of fuel as per requirement.
Tank: The tank is basically the storage tank for fuel. For most of the cases this tank is in the wings of the aircraft. Now in these days’ permanent chambers are made into the wings, but in previous days there were rubber chambers.
Line valve: It is the valve provided on the fuel pipe line makes a single side flow of fuel from the tank to the engine.
Filter: The filters are used in fuel pipe lines for providing the filter a clean and filtered fuel.
Flow meter: It is the meter also attached at the fuel pipe line to shoe the intake of the engine.
Quantity indicator: It is the general gauge meter provides a general idea about the quantity of fuel in the tank.
Warning component: It is a warning device that shows or warns the pilot on emergency situation, like low fuel.
Fuel drain: It is basically a drain port provided at the tank for draining purpose.
Heaters: At high altitude the temperature is very less, that is why the combustion effect is decreases for the fuels at higher altitude. For that reason, to make the temperature of the fuel higher a heater is used.
These are the basic components and their usage in the fuel system of any aircraft.
What we need to make as a conclusion of this report is very common. Since all the available aircrafts right now having perfect parameters discussed above. We can say only, the things are discussed above are the very basic one, but at the time of designing the aircraft we need to be much more careful on this topic and we need to study all this in more detail. Then only we will be able to get exactly the clear ideas and overview on this topic. Still it is enough to study on this topic which is being provided in this report. Only the very basic and some detail overview can be taken from this particular report with their operational brief.
Rosenkrans, W. (2011, March). Grear Shakes (Expanded Version). AeroSafety world.
Neese, B., 1999, “Aircraft Environmental Systems”, Endeavor Books.
Anderson, John D. Jr., (1999) Aircraft Performance and Design, McGraw-Hill, New York.
Roskam, J. (1985) Airplane Design, Roskam Aviation and Engineering Corp., Ottawa, Kansas.
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Essays, BookMy. (November 2018). Airframe Mechanical System. Retrieved from https://www.samples.bookmyessay.com/airframe-mechanical-system/
Essays, Bookmy. (November 2018). Airframe Mechanical System. Retrieved from https://www.samples.bookmyessay.com/airframe-mechanical-system/
All Answers ltd, 'Airframe Mechanical System' (Bookmyessays.com, September 2019) https://www.samples.bookmyessay.com/airframe-mechanical-system/ accessed Friday 10th July 2020