User talk:Craig.tilson127

Aviation Brakes:

Normal skid control: Comes into operation when any wheels starts decelerating towards a skid. The output sensor feeds back a signal which is proportional to wheel speed to the anti-skid control valve via the skid control box removing some of the hydraulic pressure on the braking system. This allows the wheel to rotate a little faster stopping it from skidding. A pilot can turn off the anti-skid system, error and warning messages will be shown on all flight decks should they be either turned off manually or be inoperable.

Locked wheels skid control: Causes the brakes to be fully released when its wheel locks, (for instant over a patch or ice). It occurs if the 'normal skid control' does not prevent the wheel from skidding. To relieve a locked wheel skid, the pressure is bled from the brakes for longer than in the normal skid function, this allows the wheel to regain speed. It generally comes into action if speeds are less than 15-20mph.

Touchdown Protection: Prevents the brakes being applied during landing while the aircraft is still in the air, the brakes are held off even if the brake pedals are pressed. The wheel is given the chance of rotating before the full weight of the aircraft is applied and before the brakes come into action. Two conditions must exist before the skid control valves allow brake application: A squat switch must signal the weight of the aircraft on the ground. The wheel generators sense a wheel speed of 15-20mph. A fault can easily be made in thinking that touchdown protection is made by the air to ground sensing switch. It is however the wheel speed switch which prevents the wheel brakes being applied in the air. The wheels must be allowed to run up to a set speed before the brakes can be applied.

Fail safe protection: Monitors the operation of the anti-skid system. It automatically returns the brake system to full manual operation in case of systems failure.

Meteorology- DALR & SALR
DALR & SALR:

Dry Adiabatic Lapse Rate- DALR- 3degreesC/ 1,000ft Saturated Adiabatic Lapse Rate- SALR- 1.8degreesC/ 1,000ft (figure used for JAA exams)

If we take a parcel of air and give it a trigger to rise (such as up the side of a mountain), the parcel of air begins to expand. At the top of the mountain depending on the temperature of the parcel of air and the atmospheric surrounds the parcel will either, descend, ascend, or remain at the same level. If the parcel of air ascends then the atmosphere is said to be unstable. If the parcel of air descends then the atmosphere is said to be stable, and adiabatic heating occurs. If the parcel of air remains at the same level then the atmosphere is said to be neutral.

Looking at an SALR and DALR graph of height against temperature. The absolute stability region is to the right of the SALR line, this region is known as absolute stability. The region to the left of the DALR is unstable and therefore known as absolute instability. The region between the DALR & SALR is known as Conditional Instability, however, whether the atmosphere is stable or unstable is dependent on the relative humidity (RH) of the atmosphere. If the ELR (Environmental Lapse Rate) is between 3 and 1.8 degrees per 1,000ft (Conditional Instability) and the atmosphere is dry/ unsaturated then the air is known to be stable. If however the ELR lies in the Conditional Instability region and the air is saturated then the atmosphere is unstable.

The term conditional stability is not used is JAA examinations and should therefore be treated as incorrect.

Principles of Flight: Inboard ailerons, Mass balance, Artificial feel
Inboard Ailerons

To overcome aileron reversal due to aero-elastic distortion. Ailerons are normally fitted close to the wing root (close to fuselage section), they operate with the spoilers in order to coordinate roll at high speeds. At low speeds (during take off and landing) both inboard and outboard ailerons are used. There is a mechanical locking device, operated when the flaps are retracted, which locks the outboard ailerons in a streamlined position, flush with the wing.

Mass Balance Achieved my attaching weights forward of the hinge line so that the center of gravity (C of G) moves into or slightly ahead of the hinge line. The weights are usually stored internally (possibly inside the horn balance or the arm attached to the surface). They help by altering the period of vibration and the liability to flutter.

Artificial Feel Manually operated flying control systems directly feed back stick forces to the pilot in order for him to get a feel in his controls. In a power operated flying control system there is no direct relationship and the only force felt is the movement of the servo valve. To prevent over controlling and over stress of the aircraft artificial feel in incorporated into the control columns. The artificial feel unit must be capable of producing opposing forces which vary with angle of deflection and aircraft speed.

Flight Instruments: Magnetism
Magnetism

Inverse square law: The forces of attraction and repulsion strengthen rapidly at short range. The two poles are inversely proportional to the square of the distance between them. F = K/ D(squared). F = M1 x M2/ D(squared).

Magnetic moment: A magnetic moment is used to express the strength of a magnet by indicating how strongly a magnet tries to align itself with a magnetic field. A magnetic system in an aircraft compass must be very sensitive for it to respond to the Earths weak field. To achieve this magnets with high magnetic moments (strong magnets) are used.

Hard iron: The term hard does not actually refer to the materials physical properties but to the fact that hard to magnetize. A strong magnetic field must be created and the hard iron is placed in the magnetic field. Hard iron is said to be a permanent magnet.

Soft iron: Again soft does not refer to the materials physical properties. Soft iron is easily magnetized with only a weak magnetic field. It is also considered to be a temporary magnet.

Magnetic variation: The angle measured in the horizontal plane, between the magnetic meridian at a point and the true meridian at a point. Variation can have any value from 0-180 degrees and is measured in the East, West direction. Magnetic Variation West Compass Best, Magnetic Deviation East Compass Least. What this means that if you are out to the west then your compass will be a greater value compared with if you were out to the East where you compass will read a small value.

Magnetic Dip: One end of a freely suspending magnet will dip below the horizontal and point to the nearest pole. Magnetic dip does not occur at the Magnetic equator where the reading =0. Moving the magnet North or South of the magnetic equator the dip gradually increases, it reaches about 66degrees in the UK where it is 50N. Over the Earth's magnetic poles, the dip = 90 degrees and the freely suspending magnet will point vertically down.

Isogonals: lines joining places having the same magnetic variation. Agonic lines: lines joining places where the variation is zero. Isoclinals: lines joining places having the same magnetic dip and generally follow the geographic parallels of latitude. Isodynes: lines joining places where the directive force has the same value.

Principles of Flight: Damping & Aileron reversal
Aileron Reversal

Occurs at high forward airspeeds, the direction of roll will be the opposite to that of the pilots inputs. The aero elastic distortion may be apparent as a reduction in roll at the higher forward airspeeds. (The speeds which achieve aileron reversal are outside the normal flight envelope speeds). When flaps are extended a wing twisting force occurs, this may also lead to aileron reversal, the aero-elastic distortion of the airframe may affect stability and control in pitch, yaw and roll. Aileron power increases as the square of the forward speed, whereas the torsional stiffness in the wing structure s constant with speed.

Damping Damping is the resistance to movement. A rolling force is caused by a change in lift due to aileron deflection and is proportional to the amount of aileron deflection and to EAS. Damping forces are caused by an increase in the angle of attack (AoA) of the down going wing and the decrease in AoA of the up going wing. Using vector sums the value of the damping angle of attack can be calculated.