Aeronautical Engineering

• Aeronautical engineers design, develop, test, and help manufacture commercial and military aircraft, missiles, and spacecraft.
• Aeronautical engineers also develop and design extraordinary technologies such as: supersonic jets, helicopters, space shuttles, satellites and rockets.
• Work done by aerospace engineers has made such things as speedy mail delivery and moon travel possible.
• Aerospace Engineers are working to launch a space shuttle to reach the moon.
• Engineers carry out routine maintenance on the ground during aircraft overhauling at airports.
• They respond to reports from air crew of any difficulties experienced during flights and carry out repairs and corrections.
• They also do maintenance and overhaul of aircraft in hangers and workshops when an aircraft is due for its regular inspection and checks.

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:

• 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 use of the 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.

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.

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 change in volume (V/V8), pressure over change in pressure (p/p8), and time over 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.

Shock Only at supersonic speed Message (about aircraft presence downstream) waves go upstream at the speed of sound. But Aircraft goes more than the speed of sound. (supersonic) Before upstream air get the message about aircraft presence, air encounter the aircraft. No time to adjust the airflow, Hence Shock.

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 and shear stress having the dimension force per unit area. This helps the movement of the body through the fluid.

There are various steps required to solve the problems of aircraft flying high and at very large speed are as follows:

• Build stiff wings that allow and provide the resistance to torsional diversion beyond the maximum speed of the aircraft.
• Use two sets of ailerons and one outboard pair that can be operated at low speeds.
• Use of one inboard pair that can be used to operate on high speeds, this will have less twisting impact when the ailerons are positioned outboard.
• Use spoilers that can be positioned independently or can be paired with ailerons. These reduce the lift on the down going wing by interrupting the airflow over the top surface.

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:

• It is used with different applications that are involved in taking off and landing to keep aircraft straight.
• Providing assistance that is, limited only for the aircraft to turn correctly.
• Used in applications during spin to reduce the roll rate of the aircraft and there are some applications that provides low speeds and high angles to allow the raising of the wings.

• The criteria that are required for an aircraft to be longitudinal statically stable, is:
• To have a nose-down pitching disturbance that is used to produce the aerodynamics forces to give a nose-up restoring moment.
• This restoring moment that is produced should be large enough to return the aircraft to its original position after the disturbance.
• The requirements are met by using the tail-plain that is horizontal stabilizer used to provide the stability to the aircraft.

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.

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 show 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.

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.

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:

• Trailing edge flaps includes different flaps like Plain flap that is used to retract the complete section of trailing edge and it is used in downward.
• Split flap gets formed by the hinged lower part of trailing edge and the lowered top surface remains unchanged and it eliminates the airflow that occurs over the top of the surface of the plain flap.
• Leading edge flap is used to augment the low speed lift that is swept on the wing aircraft. They help in increase the camber and allow the coupling to operate together with the trailing edge flaps.

The properties of the mechanics are as follows:

Strength: This is the applied force on a material that can withstand prior to fracture. It is measured by the proof or yield stress of a material that is under action.

Working stress: This is the stress that is being imposed on a material as a result of the load that is being subjected on the material. The loads that are given must be in the elastic range.

Proof stress: It defines the tensile stress.

Ultimate tensile stress (UTS): It defines of a material that is given by a relationship or its maximum load.

Specific strength: It defines the light and strong of a material that is used in aircraft making. This is done to maximize the payload and meeting all the safety requirements.

Malleability: It defines the ability to be rolled into sheets or get a shape under pressure. This includes examples of gold, copper and lead.

Elasticity: It defines the ability of a material to return to is original shape when an external force is removed from the material.

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.

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.

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.

The elements required to display oscillatory motion are as follows: Period: this is related to the time and it signifies the time that elapses in between the motion that will repeat itself after some time again. Oscillatory motions allow themselves to be repeated after equal intervals of time and this is called as periodic.

Cycle: It represents the completion of one period and it also signifies the motion that is completed in one period.

Frequency: It defines the number of cycles completed in unit time.

Amplitude: It defines the distance from one point to another or from highest to lowest point of the motion from the central position.

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 being 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 unit (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.

• Incompressible flows are the flows that have a constant density (?). Whereas, the compressible flows are those that consists of variable densities.
• The flows that exist are compressible in nature. Whereas, incompressible flows, doesn’t exist in nature or are very rare.
• Incompressible flows are used to model aerodynamic problems without loosing any detrimental accuracy i.e. most problems that exist in hydrodynamics considers 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 for high speed flows.

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:

Category B1 (mechanical): These are the maintenance technicians that have good knowledge regarding the working of airframe, engine, 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 equipments, electrical, instrument and radar related systems. They undergo proper training to handle the aircraft equipments and gain practical experience to deal with day to day activities.

 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:

• Strength
• Stiffness
• Specific strength and stiffness
• Ductility
• Toughness
• Malleability and elasticity.

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:

• Tensile strain
• Compressive strain
• Shear strain.

The safety recommendations are required while dealing with the accidents and the inquiry of the aircrafts. The recommendations needed are as follows:

• CAA (Civil aviation authority) examines the applicability of self-certification of 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.
• Review of the system takes place to interpret the single components of the aircraft that is vital in its design.
• Reviewing of the quality assurance system and the reporting methods take place to encourage more better designs to be provided for the 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.

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 schedule on field inspections for aircraft maintenance.
• Activities of complex rectification.
• Fault diagnosis on aircraft systems and their equipment’s.
• Modification and performing special instruction to monitor and manage the system.
• Repairing of airframe and other aircrafts.
• Activities performed like removal of aircraft components and fitting the required parts.
• Use of BITE (built-in test equipment) and diagnostic equipment’s to perform repair tasks.
• Supervising and certifying the work of other technicians involved in it.

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.

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 they 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 shock wave increases leading to higher temperatures between the shock and body surface.

Elastomeric bearings that elastomeric bearings are bearings constructed from a rubber type material and have limited movement that is perfectly suited for helicopter applications.

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 equipment’s 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.

When the external force is applied on the elastic body, the body will deform from its original position. There will be an internal resistance force which will act opposite to the external force with the same magnitude.  The internal resistance force per unit area is called stress. Pressure is the force which will act normal to the surface and all over the surface.

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:

Modulus of rigidity: This defines the relationship between the shear stress and shear strain.

Bulk modulus: This defines that if a body volume v is subjected to an increase in an external pressure then the volume will be changed by dV, this deformation will be change in volume not in shape.

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 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.

• Incompressible flows are the flows that have a constant density. Whereas, the compressible flows are those that consists of variable densities.
• The flows that exist are compressible in nature. Whereas, incompressible flows, doesn’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 considers 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 for high speed flows.

The high thrust producing jet engine is ramjet engine.

Viscous flow: It 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: It is consisting of the limited influence of friction, thermal conduction and diffusion that is limited to thin region that is limited to the body surface. Whereas, the7 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.

The criteria that are required for an aircraft to be longitudinal statically stable is:

• To have a nose-down pitching disturbance that is used to produce the aerodynamics forces to give a nose-up restoring moment.
• This restoring moment that is produced should be large enough to return the aircraft to its original position after the disturbance.
• The requirements are met by using the tail-plain that is horizontal stabilizer used to provide the stability to the aircraft.

Yawing motion mans the sideways motion aircraft about the lateral axis. In other words, side to side motion of aircraft.

This is the combined effect low pressure and speed of plane in sky. Body of aircraft is made up of aluminum due to its good tensile strength and good conductor.

Ram jet is a jet engine with no moving parts, only fuel spayed and burned.

VFD having three main section namely rectifier, DC bus, and inverter. By rectifier input supply AC is converted to DC , in the section main part is pulse also getting change by number of diodes. In DC bus section having capacitor the power is getting store. In inverter section the DC is converted to AC and the supply.

Yes, there is a policy and procedure to be followed for the missing clearance limit, so a Pilot can leave and reach a different altitude for sometime within the limit and should come back to the proper clearance limit once things are in control. This time limit is only as per the procedure in the manual.

Newton’s 3rd law & Bernoulli’s Principles are used in the working in every GAG.

A Pilot can descend up to 500 bare minimum, without informing the ATC (Air Traffic Controller) and this is only during an exceptional case. However, it’s always better to be in regular touch with the Air Traffic Controller and to keep him informed about the descent rate. This will not have any traffic problems during landing in the runway.

Complying and following the actual speed adjustment policies, a pilot can run and indicate plus or minus 10 knots or 0.02 Mach number of specified speed. Its always better to keep the land air officer in the loop before adjusting the air speed. Exceptions are always there to meet the emergency requirement.

Talk to your co-worker directly and explain him that you are having a problem working with him and make him understand the situation, if he is not willing to listen or not co-operating, then direct the issue to chief pilot.

The testing of small rocket engines and entails development by researching on aerospace. They are responsible to perform and experiment on laboratory facility which is dedicated to aerospace. One should be capable of solving problems by applying knowledge by solving problem of the research done. They will be working with technical team of researchers and they should have ability handle projects alone.

People working on these areas as a aerospace engineers should have familiarity and exposure to NASTRAN and MATLAB with knowledge on space environment and modeling of flexible dynamics. These aerospace engineers will be responsible to work in the areas of structural control, momentum control, line of sight (LOS), spacecraft mission design, control of space boards payloads, operational engineering.

Aerodynamics / performance analysis in military programs include responsibility like analyzing aerodynamics impacts which effects from external modifications, developing mission profiles based on requirements from the customer, performance data of the mission which includes takeoff and landing details, end route and mission data performance. Analyze the configurations using the dynamics which are fluid and computational. Additional task may include support for wind tunnel planning for test flight. Documentation, test support, data analysis should be done on regular basis. Coordination of aerodynamics with multi discipline teams and data should be provided for support flight management system or mission planning software.

 Refer to your plane manual and discuss the same with your client and ensure you make him understand the procedures and rules. If he does not respond, you will call your concerned aircraft officer at the airport and escalate and make sure your voice frequency is recorded.

In aerospace engineering there are lots of interesting topics which include rocketry, aero planes, Lego’s. As a school student I started sketching for future aircraft and space craft, military aircraft. I analyzed the importance of space travel, aviation history, and aerospace industry and hence decided to get into this field.

There are different kind of people travel in a airlines we don’t know about them. Some people may act violent normally girl’s soft nature. so the airlines prefer a beautiful girls to impress a customer so airline prefer beautiful girls for hostesses.

Reversing the armature terminal is better & applied in practice. This is Because of the following drawbacks in field reversing method.

High voltage build-up: during reversing the field terminal which is high enough to puncture the insulation of field coil.

High flash-over will occur: during reversal, the armature current should be limited to the rated value, otherwise it will draw twice the time of starting current. We can insert the external resistance to limit the current while reversing the armature terminal. Whereas, in field reversal we cannot give any provision to limit armature over current.

It jeopardizes the accuracy but it also has some advantages but cannot be used due to its inaccuracy.

Mercury is a liquid metal.

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.

To overcome obstacle, one should have strong determination and self-confidence on himself / herself. They have to face life as it comes under surface of the space shuttle will experience above 2300’c at the time of re-entering.

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.

People working on these areas as a aerospace engineers should have familiarity and exposure to NASTRAN and MATLAB with knowledge on space environment and modeling of flexible dynamics. These aerospace engineers will be responsible to conduct stress analysis on metallic and composite structures. NASTRAN, IDEAD, Oracle and PATRAN proficiency level is required. Their duties also include on aircraft which are metallic and composite structures. This includes and understanding of control surface stiffness and loop calculations, finite element modeling (FEM), fatigue testing requirement and analysis.

Aeronautical engineering deals with vehicles which operates in the atmosphere Aeronautical engineering deals with vehicles operating in space. Aeronautical engineering works on tunnel tests, analyzing flight test data, manned space flights, planning future space missions, spacecraft operations, designing and testing robotic systems, developing new propulsion system, computing optimum flight trajectories, developing communication systems for distance space probes and designing new rockets.

Astronautically engineer includes designing power systems for spacecraft structure, developing communications systems for distant space probes, developing hardware skills for operations in spacecraft, designing and testing robotic systems, developing new propulsion systems and computing optimum flight.

The main areas in aviation are:

• Artificial intelligence,
• Aircrafts and parts,
• Advanced materials, composites and specialty metals,
• Computers, electronic components and systems,
• Fighters and attack aircraft,
• Government defense policies, and goals,
• Lasers,
• Navigation controls and guidance systems,
• Ordinance and Military vehicles,
• Aviation electronic/Avionics,
• Robotics,
• Satellites,
• Search and detection equipments,
• Strategic defensive initiative,
• Sensors and instrumentation,
• Ships,
• Space vehicles and commercialization of space.

Aeronautical is not the thing to study it’s the thing to understand the concept that how to fly. Obviously in every college aero students are the best one’s in all disciplines.

Least count is the highest degree of accuracy of measurement that can be achieved.

The aircraft outer body is made of highly conductive material and insulated with the inner body. In the air Craft outer body gets charged statically which is of very high value. The design is so made that charge tries to remains at the outer surface of the craft. At the time of landing a strip type part touch the ground and all the charged decay in the earth without any damage of anything.

NO, Due to the following reasons:

• Usually Engine is very heavy, if it is put at the cantilever wing tip, the weight/lever arm is more and structurally it is not a feasible design.
• Aerodynamic characteristics of the A/C and Engines are broadly affected.
• In case of Single engine failure, tendency to yaw and roll.
• In case of Electrical fuel system malfunction, providing gravity fuel feed to the wingtip engines is complicated.

There are three types of emergency landings like:

Forced landing: This is a situation where Air Craft engine fails and Pilot is forced to land the plane in the nearest airport.

Precautionary landing: This is used when Pilot faces a problem due to severe weather conditions or being lost in the air space traffic or due to lack of fuel or expecting an engine trouble.

Ditching: This is when where Pilot cannot avoid this situation but to just land on water, which is safer than air bound.

Vibration isolation is the process of isolating an object, such as a piece of equipment, from the source of vibrations.Vibrations propagate via mechanical waves and certain mechanical linkages conduct vibrations more efficiently than others.

The testing of small rocket engines and entails development by researching on aerospace. They are responsible to perform and experiment on laboratory facility which is dedicated to aerospace. One should be capable of solving problems by applying knowledge by solving problem of the research done. They will be working with technical team of researchers and they should have ability handle projects alone.

Chief Pilot in command can deviate from rules and regulations during emergency period; he can do it to get the plane back to the normalcy or to meet the expected requirement of the emergency.

Yes, ATS has several differences courses such as the AlliedSignal TFE731 and the Rolls Royce BR715/710. Other differences courses may be developed according to client needs.