1. Why refrigeration is done inside aircraft, and why aircraft body is made of aluminum’s?
This is the combined effect low pressure & speed of plane in sky. Body of aircraft is made up of aluminum’s due to its good tensile strength & good conductor.
2. What is ram jet?
It is a jet engine with no moving parts, only fuel spayed and burned.
3. Does not simplification of complex honeycomb designed for thermal protection system of are usable launch vehicles jeopardize the accuracy of results?
It jeopardize the accuracy but it also has some advantages but cannot be used due to its inaccuracy.
4. Are thermal protection systems of space crafts commonly composed of one panel or a collection of smaller tiles?
Thermal protection system of space crafts will be of tiles which are made up of ceramics and ceramic composites to with stand thermal shocks and to avoid cracks it is used as tiles.
5. What is a liquid metal?
6. What is the highest temperature the space shuttle under surface experiences during its mission?
Under surface of the space shuttle will experience above 2300’c at the time of re-entering.
7. Explain how you overcame a major obstacle?
To overcome obstacle, one should have strong determination and self confidence on himself / herself. They have to face life as it comes.
8. What is SPICE? Where was it developed?
The full form of SPICE is Simulation program with integrated circuit emphasis. This is the widely used analog simulator which was developed at electronics research lab of California University.
9. What are the three tactical elements of electronic warfare?
Electronic warfare has three main elements:
10. What is the requirement to become a Professional Engineer (PE) in the field of Aerospace?
Professional Engineer license is required for people who aspire to go in as officially approved engineer. The design specification is done by self employed people or working in small business. General aerospace engineers work for government or for big companies and hence few people are not very keen on becoming PE’s. To become a PE one has to pass an exam on fundamentals of engineering which takes a lot of hours to gruel and work under a licensed PE for about four years. Also they have to grow through a principle and practice of engineering exam which requires about 8 hours.
11.What are the characteristics that keep solid and fluid different?
When the force is applied tangentially on solid then it experiences a finite deformation and shear stress that is proportional to the deformation. Whereas, when the same shear stress is applied on the surface of fluid then it experiences continuous increasing deformation where, the shear stress is proportional to the rate of change of deformation.
The fluid dynamic is dividend in three different areas. They are as follows: Hydrodynamics (flow of liquids), Gas dynamics (flow of gases) and Aerodynamics (flow of air). Whereas, the state of, solid doesn’t represent any of the stages.
12.What are the objectives of Aerodynamics?
Aerodynamics deals with the theory of flow of air and it has many practical applications in engineering. There are some objectives that are being used in aerodynamics and these are as follows:
13.What are the sources involved in aerodynamics?
There are two sources that are involved in the case of aerodynamics forces and moments that are on the body. These forces are as follows:
14.What are the conditions given for the two flows to be dynamically similar?
To measure the dynamicity of the two flows consider two different flow fields over two different bodies. This way the conditions that get generated are as follows:
15.What are the differences between continuum flow and free molecule flow?
The flow that is moving over the body i.e. in a circular cylinder of diameter d is the continuum flow, whereas the flow that consists of individual molecules moving in random motion is the free molecule flow.
The mean free path (?) defines the mean distance between the collisions of the molecule and if this path (?) is smaller than the scale of the body measured (d) then the flow of the body is considered as continuum flow.
The path (?) that is of same order as the body scale then the gas molecules then the body surface will have an impact of the molecules and this is known as free molecular flow.
16.What are the differences between inviscid and viscous flow?
Viscous flow is the flow in which the molecule moves in random fashion and transfers their mass, momentum and energy from one place to another in fluid. Whereas, an inviscid flow is the flow in which there is no involvement of friction, thermal conduction or diffusion while the molecules are moving.
Inviscid flow consists of the limited influence of friction, thermal conduction and diffusion that is limited to thin region that is limited to the body surface. Whereas, the viscous flows involve the flows that dominates the aerodynamics of the blunt bodies like cylinder. In this the flow expands around front face of cylinder and it separates from the rear surface of it.
17.What are the differences between incompressible and compressible flows?
18.What are the different speed types of flows used in identifying Mach number?
There are four types of flows that consist of different speeds and can be identified using Mach number:
Subsonic flow where M<1 everywhere, this is a field that is defined as subsonic if it matches the Mach number that is less than 1 at every point. These are displayed by smooth streamlines that consists of no discontinuity in slope. The flow velocity is everywhere less than the speed of sound and the disturbances are all around the flow field.
Transonic flow, where mixed regions exist and M<1 or M>1, this is a flow field that defines that the M8 is increased just above the unity and it is formed in front of the body. These are the mixed subsonic and supersonic flows that are influenced by both the flows.
Supersonic flow where M>1 everywhere, this type is defined when Mach number is greater than 1 at every point. They are represented by the presence of shock waves across which the flow properties and streamlines changes discontinuously.
Hypersonic flow where the speed is greater than supersonic, this is defined when the shock waves moves closer to the body surface and the strength of the shockwave increases leading to higher temperatures between the shock and body surface.
19.What are the major sectors involved in aircraft maintenance?
There are two major sectors involved in aircraft maintenance and these are handled by certifying technician in the field of support and maintenance. These are divided into two sectors as:
20.What are the operations performed by Category B technicians?
Category B consists of two sectors in the field of maintenance and they are divided in B1 and B2 with certain roles. The operations performed by Category B technicians are as follows:
21.What is the main source of power in aircraft?
The main source of power is the hydraulic motor that is provided by the scheduled service and involves operations that allow technicians to solve complex system problems. This setup required certifying the technician to operate all the system the same way as it is been done with one system. The hydraulic motor needs to be operated the same way and maintained in a proper way. The alignment need to in synchronization with the aircraft auxiliary power unity (APU) before anything is done with the aircraft positioning. A standard need to, be followed to maintain the aircrafts and its parts equipped and working.
22.What are the differences in the job performed by line maintenance certifying staff and base maintenance certifying staff?
The difference that exists between the two is that line maintenance certifying staff has the responsibility to inspect, rectify and perform the related or associated maintenance activities on the aircraft on the airfield. Whereas, the base maintenance certifying staff, perform the maintenance activities away from the live aircraft areas.
The maintenance that is being performed by the line maintenance staff is restricted to use limited tools, and equipments that are present on the site to perform the first line diagnostic maintenance. Whereas, Base maintenance certifying staff is associated with the line maintenance staff as it requires inspecting and performing complex modification in the aircraft carriers.
23.What is the role performed by Category C personnel in maintenance of aircraft?
Category C personnel are responsible for maintaining the management role of controlling the progress of the base maintenance inspections and seeing the work that is getting performed. These handle the category B and category A staff and monitor their work. They are responsible for ensuring the good work that will be carried out by providing the certification of maintenance. Category C personnel upon the completion of the maintenance job done by the base maintenance staff provides the certificate to allow the servicing of the aircraft to proceed. This way the people working in the staff become eligible to perform and provide services for flight.
24.What are the safety recommendations required while maintaining aircraft?
The safety recommendations are required while dealing with the accidents and the inquiry of the aircrafts. The recommendations needed are as follows:
25.What are the different stress types present in aircraft operations?
Stress is a result that is caused when a solid e.g. metal bar is subjected to an external force. Stress is defined as force per unit area and the basic unit includes MN/m2, N/mm2 and Pa. There are basically three types of stress:
Tensile stress: it is the stress that is setup when the force tries to pull the material apart.
Compressive stress: it is the stress that is produced by the force that is trying to crush the material.
Shear stress: is the stress that results from the force that tends to cut through the material i.e. tend to put one material slide over another one.
26.Why is strain a major factor in aircraft engineering?
Strain is when a material is altered in shape, this happens due to the fact that the force is acting on the material. The body is strained internally as well as externally without having any differences of dimension but it just has the differences at the atomic level. It is the ratio of change in dimension over the original dimension. It is very important due to the fact that building an aircraft requires the knowledge of these factors and the formulas that are associated with it to successfully implementing the parts together. There are three types of strain:
27.What are the different types of modulus involved in mechanics?
Modulus of elasticity is given by the Hooke’s law that states that stress is directly proportional to strain, while the material remains elastic. The external forces that are acting on the material is just having the sufficient to stretch the atomic bonds this way the material can also return back to the original shape. The different types of modulus are as follows:
28.What are the mechanical properties required to know before performing maintenance?
The mechanical properties provide the definition of the behavior of the material that is being put under the action of external forces. This is an important aspect to aeronautical engineering that is also used to gain knowledge for applications developed for aircrafts. This provides an overall view of the structure of the aircraft and the maintenance aspect of it. The properties used are as follows:
29.Explain in brief about each property used in mechanics?
The properties of the mechanics are as follows:
30.What is the purpose of load extension graphs?
Load extension graphs are used to show the result of mechanical test done on the material to know their certain properties for example finding out the heat treatment of a material. These graphs shows certain phases of a material when it is being tested for destruction of the properties like elastic range, limit of proportionality, etc. The material needs to obey Hooke’s law. The elastic limit needs to be at or very near to the limit of proportionality. If the limit is passed the material ceases to be proportional to the load. If the stress increases on the material then the waist reduces as the stress = force/area. This graph represents a curve that shows different stages like elastic stage, and plastic stage.
31.Why is torsion such an important feature in aircraft engines?
Torsion is used to drive shafts for aircraft engine driven pumps and motors. They are also involved in having a force behind propeller shafts, pulley assemblies and rive couplings for machinery. The shear stress is setup within the shafts and it results from the torsional loads. The size and the nature of torsional loads and stresses need to be known while making the design or else premature failure can occur. The shafts are used as a component to transmit torsional loads and twisting moments or torque. They can be a cross section or a circular component as it is more suitable to transmit the torque for pumps and motors to supply the power to the aircraft system.
32.What is the main function of propulsive thrust?
Propulsive thrust is used in aircraft system, when an aircraft is traveling through air in straight or level flight then the engine produces a thrust that is equal to the air resistance or the drag force on the aircraft. If the engine thrust exceeds the drag then the aircraft will accelerate and if drag exceeds the engine thrusts then the aircraft system will slow down. The thrust force that is used for aircraft propulsion should always come from air or gas pressure. The forces that are external always act on the engine or propeller. This propeller can be driven either by a piston or a gas turbine engine. If there is a use of jet engine then the high velocity exhaust gas is produced.
33.Why is the study of gyroscopes motion required to learn aircraft applications?
Gyroscopic motion is considered as an important study for aircraft application for the inertia and momentum of the body that is used in circular motion. The momentum is the product of the mass of a body and its velocity. This is a measure of the quantity of motion of a body. Inertia is the force that doesn’t allow any change to happen in momentum. Gyroscope is the rotating mass that can be moved freely at right angles to its plane of rotation. This utilizes the gyro rotor or gyroscopic inertia to provide the motion unless it is compelled by an external force to change the state. This uses property of rigidity as gyroscope acts as a reference point in space.
34.What are the laws of gyro-dynamics?
Gyro-dynamics deals with gyroscopic motion that is used for creating aircraft application as it allows inertia and momentum of the body. These laws consist of the two properties of rigidity and precession to provide the visible effects gyro-dynamics. These are as follows:
If a rotating body is mounted and it is free to move about any axis that passes through the center of mass, then the spin axis that is used will remain fixed in inertial space without displacing any of the frame.
If a constant torque is applied to any direction such as about an axis, or perpendicular to the axis, then the spin axis will move about an axis that is mutually perpendicular to both the spin and the torque axis.
35.What is being expressed by Sperry’s rule of precession?
Sperry’s rule of precession describes about the direction in which the precession takes place. This precession is dependent on the direction of rotation for the mass and the axis of the torque that is applied on the material. It provides a guide to the direction of precession that allows easy finding of the direction of the applied torque. This also helps in finding out the direction of the rotation of gyro-wheel. If the torque is applied and is perpendicular to the spin axis then it can be transferred as a force.
36.What are the elements required to display oscillatory motion?
The elements required to display oscillatory motion are as follows:
37.What are the different lift augmentation devices present?
Lift augmentation devices provides flaps that are moving wing sections that increase wing camber and provide an angel of attack. Flaps have their own use like if an aircraft takes off and land in a short distance then the wings of it should produce sufficient lift at lower speed. Flaps provide a way to slow down the aircraft. There two categories and they are as follows:
38.What are the steps required to solve the problems of aircraft flying high and at very large speed?
There are various steps required to solve the problems of aircraft flying high and at very large speed are as follows:
39.What are the functions performed by rudder?
The rudder is involved in providing the movement to the ports that gives a lift force to starboard. This will allow the aircraft to turn and uses the ailerons effectively to bank the aircraft by minimum use of rudder. The functions performed by rudder are as follows:
40.What are the criteria need to be followed for an aircraft to be longitudinal statically stable?
The criteria that are required for an aircraft to be longitudinal statically stable, is: