Aeronautical Engineering Interview Questions:-
Tips to prepare for Aeronautical Engineering Related Interview by Pritish Kumar Halder below:
1. What are the characteristics that keep solid and fluid different?
When the force is applied tangentially to a 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.
2. What are the objectives of Aerodynamics?
Aerodynamics deals with the theory of the 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:
- It is used to predict the forces, moments and heat transfer from the bodies that is moving through the liquid.
- It deals with the movement of wings or the use of wind force. This way it requires the calculations to be done for the aerodynamic heating of the flight vehicles and the hydrodynamic forces applied on the surface of the vehicle.
- It is used to determine the flows that are moving internally through ducts. This way it makes the calculations and measurement of the flow properties that is inside the rocket and jet engines.
3. 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:
- Pressure distribution: this is the distribution that is over the body surface
- Shear stress distribution: this is the distribution that is over the body surface
- These sources are for the body shapes and it doesn’t matter how complex they are. The mechanism that is being used to communicate with the bodies that is moving through a fluid. Both the pressure (p) and shear stress (?) having the dimension force per unit area. This helps the movement of the body through the fluid.
4. 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:
- The streamlined pattern shouldn’t be geometrically similar.
- The distribution of the volume over the change in volume (V/V8), pressure over the change in pressure (p/p8), and time over the change in time (T/T8). These changes take place throughout the flow of the field and they remain the same against the common non-dimensional coordinates
- The force coefficient remains the same.
- There is a similarity in both the flows like the solid boundaries are geometrically similar for both flows.
5. 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 a continuum flow.
- The path (?) that is of the 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.
6. What are the differences between inviscid and viscous flow?
Viscous flow is the flow in which the molecule moves in a random fashion and transfers its mass, momentum and energy from one place to another in the fluid. Whereas, an inviscid flow is a flow in which there is no involvement of friction, thermal conduction or diffusion while the molecules are moving.
The inviscid flow consists of the limited influence of friction, thermal conduction and diffusion that is limited to the thin region that is limited to the body surface. Whereas, the viscous flows involve the flows that dominate the aerodynamics of the blunt bodies like a cylinder. In this, the flow expands around the front face of the cylinder and it separates from the rear surface of it.
7. What are the differences between incompressible and compressible flows?
Incompressible flows are the flows that have a constant density (?). Whereas, compressible flows are those that consist of variable densities.
The flows that exist are compressible in nature. Whereas, incompressible flows, don’t exist in nature or are very rare.
Incompressible flows are used to model aerodynamic problems without losing any detrimental accuracy i.e. most problems that exist in hydrodynamics consider the density (?) = constant. Whereas, compressible flow is hardly used as a mathematical model to, represent the hydrodynamics.
High-speed flows are and must be treated as compressible, whereas incompressible flows are not considered high speed flows.
8. 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 the 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 consist 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, 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 change discontinuously.
- Hypersonic flow where the speed is greater than supersonic is defined when the shock waves move closer to the body surface and the strength of the shockwave increases leading to higher temperatures between the shock and body surface.
9. What are the major sectors involved in aircraft maintenance?
There are two major sectors involved in aircraft maintenance and these are handled by certified technicians in the field of support and maintenance. These are divided into two sectors:
- Category B1 (mechanical): these are the maintenance technicians that have good knowledge regarding the working of airframes, engines, electrical power systems and equipment. It also requires additional knowledge of aircraft structures and materials.
- Category B2 (avionic): this deals with the integrated knowledge of aircraft equipment, electrical, instrument and radar related systems. They undergo proper training to handle the aircraft equipment and gain practical experience to deal with day to day activities.
10. 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:
- Activities related to scheduled on field inspections for aircraft maintenance.
- Activities of complex rectification
- Fault diagnosis on aircraft systems and their equipment.
- Modification and performing special instruction to monitor and manage the system
- Repairing of airframe and other aircraft
- Activities performed like removal of aircraft components and fitting the required parts.
- Use of BITE (built-in test equipment) and diagnostic equipment to perform repair tasks.
- Supervising and certifying the work of other technicians involved in it.
11. 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 needs to be in synchronization with the aircraft auxiliary power unity (APU) before anything is done with the aircraft positioning. A standard needs to, be followed to maintain the aircraft and its parts equipped and working.
12. 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 the use of limited tools, and types of equipment 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 modifications in the aircraft carriers.
13. What is the role performed by Category C personnel in the 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.
14. What are the safety recommendations required while maintaining aircraft?
Safety recommendations are required while dealing with the accidents and the inquiry of the aircraft. The recommendations needed are as follows:
- CAA (Civil aviation authority) examines the applicability of self-certification in aircraft engineering and verifies the criticality of the tasks that need to be performed on the system. They also check the system for further services without doing any functional checks.
- A review of the system takes place to interpret the single components of the aircraft that are vital in its design.
- Reviewing of the quality assurance system and the reporting methods take place to encourage better designs to be provided for use.
- Reviewing the need to, introduce a format of job description and grades that is being provided to the engineers and managers.
- Providing a mechanism for an independent assessment to carry out the work audit and operations can be performed smoothly.
15. 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 set up 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.