PALS is really a pal for naval pilots it has three modes instrumented carrier landing system mode automatic carrier landing system mode and talk down mode.
ICES MODE:For an aircraft to land it has to maintain a constant recommended speed while losing altitude gradually until touchdown on the runway how it loses altitude with respects to the runway grounds the glider also varies accordingly and is never constant so a mere pitch up of the flight deck is drastic for the landing aircraft pilot of the aircraft must be made aware of this changing glide slope this is cone through a system called lcls centre on radar system called an spn41.
Through technically not an exact radar system an spam engages in one way transmission to the landing aircraft in bandeau it has a set of radars a centre line unit and a flight deck unit the former is situated beneath the cent reline of the runway and the latter is situated slightly high on the flight deck using sector scanning bitchy units acquire and track the approaching aircraft the fight deck init and centre line unit respectively measure the aircraft vertical and horizontal deviation for the glide slope then an spn broadcast nth ye positional difference in pulse mode in bandeau in real time.
A system called aircraft approach control system presents in the aircraft with respect to the glide scope from these signals.It them covers these signals as a set of horizontal and vertical lines on the pilot HUD.
The vertical line indicates the potion of the aircraft with respect to the center line of the runway it appears in the direction that the aircraft has to move so as to align with the center line of the runway.the horizontal line indites how much the aircraft must gain or lose altitude to fit in the glide slope.
When these two lines form a cross hair the aircraft can be perfectly aligned with the glide slope can gently nudge his controls to stay in the pitching glide slope until touchdown.
Talk down mode in this mode the pilot is instituted by landing signal offers they work form an lso console situated at the edge of the flight deck.this console gathers all flight data of the approaching aircraft from many systems then lso console computers the required flight path for landing monitors the flight apathy of aircraft and the difference that the pilot has to covet.It takes inputs from the integrated launches and recovery television system radar and wind measurement system.
This is camera and television system with all weather capability in simple words its camera can video graph both during day and night with equal clarity karts has remotely operated cameras at many places on the flight deck these camera video graph the approaching aircraft along with its relative position with the horizon.horizontals the adds glide slope cross hairs parameters and other data to that imagery the resultant composite video is displayed at the lso console catch and other importance centers like CDC the aircraft alignment with respect to the horizon indicates the lso whether the aircraft should clump up or descend so as to capture the glide slope of the pitching flight deck.
Indicates the two scenarios of an aircraft approaching for landing the scale like symbol on the left indicates acceptable limits for the aircraft in the vertical axis the dash symbol near this scale indicates the position of the aircraft the aircraft has to be ideally at the center of the crosshatch ths dad indicates the actual position of the aircraft with respect to the glide slopes if the aircraft is not not within this envelope it is waved off for another approach these symbols are generated by ilrts and fed to the lso console.
Anspn this is known as a range rate radar it detects approaching aircraft tackers it and calculated its speed it then provides this data to the lso console supplied with the accurate information on the speed of the approaching aircraft lsos can wave off the aircraft at tempting to land at an unsafe speed.
Wind measurement system this is nothing but a traditional wind measuring system based on an anemometer.It is used to measure headwind tailwind and crosswind speeds these winds can terribly affects the aircraft flight by shifting the aircraft.Headwinds resists flight tail winds push the aircraft forward and crosswinds laterally move the aircraft out of glide slope. These.These winds are troublesome.Data from the system is fed to the lsls who in tum intimate the same to the pilot the pilot then files in a way offsetting the effect of these winds.
Based on these inputs lsos communicate with the approaching pilot who constantly adjusts air craft position based on the voice commands given by lsos.
ACLS mode imagine that a pilot is returning to the carrier from a battel filed which is located 500km away after bombing enemy targets and evading enemy air defense missiles.On the way back he or she had to intensely fight with enemy fighter aircraft now on returning to the carrer the pilot has to land his aircraft under pitch black conditions.the pilots physical state is not as alert as it was when he or she left for the mission the intense adrenalin rush has tried the pilot making landing of the aircraft even more difficult.Any one in the situation would dream of a system that lands the aircraft automatically without any inputs.ACLS is that dream system.
Parts of this system exists in both the carrier and the aircraft only acls equipped aircraft can be landed automatically on a carrier basically in an acls autopilot is the aircraft is controlled by the aircraft is tracked through band tracking rada span in the carrier,Instructions for the autopilot are transmitted to the aircraft.There are two radars guiding each aircraft.
The sequence starts from a point called acquisition window during approach of the aircraft.At this point the tracking radar acquires the aircraft and starts tracking it.At this point the pilot is indicated through cockpit indicators that tha aircraft is being acquired by acls.the pilot then puts the aircraft under autopilot in landing mode.The tracking radar uses a conical scan antenna and continuously interrogates a radar beacon presents in the aircraft.This beacon responds in x band for interrogation of the tracking radar.Replies of the beacon are continuously plotted on the acls computer to derive the aircraft location with respect to the glide slope.
Instruction to the autopilot are transmitted in real time thorough a uhf data link. Autopilot has a component called approach power compensatory,which increases or decreases the engines power to vary the altitude according to the glide slopes requirement.the pilot has warning lights that give indications to abort landing and try for another attempt.Similarly at any point of time,the pilot can disengage from autopilot by applying pressure on the control stick to take control of the aircraft.
The irony is that pilots do not use this mode!They say that they do not want a computer to land their aircraft.They instead use the instrumented mode and talk down mode so this mode only serve as a fallback option during haze and fog.
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