Squawk codes are four-digit octal numbers; the dials on a transponder read from zero to seven inclusive. Thus the lowest possible squawk is 0000 and the highest is 7777. There are 4096 permutations of these four digit codes, which is why they are often called "4096 code transponders." Because these squawks are sensitive, care must be taken not to squawk any emergency code during a code change. For example, when changing from 1200 to 6501 (an assigned ATC squawk), one might turn the second wheel to a 5 (thus 1500), and then rotate the first wheel backwards in the sequence 1-0-7-6 to get to 6. This would momentarily have the transponder squawking a hijack code (7500), which might lead to more attention than one desires. Pilots are instructed not to place the transponder in "standby mode" while changing the codes as it causes the loss of target information on the ATC radar screen, but instead to carefully change codes to avoid inadvertently selecting an emergency code. Additionally, modern digital transponders are operated by buttons to avoid this problem.
There are other codes known as conspicuity codes which are not necessarily unique to a particular aircraft, but may have their own meaning and are used to convey information about the aircraft to ATC, possibly when the aircraft is not in radio contact.[citation needed] Codes 2000 and 7000 are examples of conspicuity codes.
The use of the word "squawk" comes from the system's origin in the World War II Identification Friend or Foe (IFF) system, which was code-named "Parrot". Parrot today generally refers to IFF only. The parrot check is generally done as part of the last-chance inspection at the runway, or after becoming airborne. Parrot sweet, and parrot sour are given, and the aircraft will have to abort in a real-world mission when sour, or face being attacked by friendly forces. Modern use of the word Parrot refers to a test transponder located at a fixed location off the radar facility. The parrot verifies range and direction accuracy of the radar facility.[citation needed]
Routine codes
- 0000:
- military intercept code (in the US)
- mode C or other SSR failure (in the UK).
- shall not be used – is a non-discrete mode A code (Europe)
- 0001: Military code for high speed uncontrolled (non-ATC directed) flight (US)
- 0021: VFR squawk code for German airspace (5000 feet and below) - from 15 March 2007 replaced by the international 7000 code for VFR traffic.
- 0022: VFR squawk code for German airspace (above 5000 feet) - from 15 March 2007 replaced by the international 7000 code for VFR traffic.
- 0033: Parachute dropping in progress (UK)
- 0041 to 0057: In Belgium assigned for VFR traffic under Flight Information Services (BXL FIC)
- 0100: In Australia: flights operating at aerodromes (in lieu of codes 1200, 2000 or 3000 when assigned by ATC or noted in the Enroute Supplement Australia)
- 1000:
- 1200:
- Visual flight rules (VFR) flight, this is the standard squawk code used in North American airspace when no other has been assigned.
- In Australia civil VFR flights in class E or G airspace.
- 1400: VFR flight above 12,500'ASL when no other code has been assigned (Canada).
- 2000:
- 2100: Australia: Ground testing by aircraft maintenance staff.
- 3000: Australia: Civil flights in classes A, C and D airspace, or IFR flights in Class E airspace.
- 4000:
- 4400 to 4477: Reserved for use by SR-71, YF-12, U-2 and B-57, pressure suit flights, and aircraft operations above FL600 (USA only).
- 4600: Intentional OCF or Aerobatic Flight (US)[citation needed]
- 5000: Aircraft in Military Operations
- 6000: Australia: Military flights in Class G airspace.
- 7000:
- 7001:
- 7004: Aerobatic and display code in some countries.
- 7010: VFR circuit traffic code in the UK
- 707X: Paradrop activities in France (7070, 7071, 7072...)
- 7615: Australia: civil flights engaged in littoral surveillance.
- 7777:
- military interception (US) ("Under no circumstances should a pilot of a civil aircraft operate the transponder on Code 7777. This code is reserved for military interceptor operations.")
- non-discrete code used by fixed test transponders (RABMs) to check correctness of radar stations (BITE). (US, Germany, Netherlands, Belgium, ...)
Emergency codes
- 7500: Unlawful Interference (i.e. Aircraft hijacking)
- 7600: Lost Communications
- 7700: General Emergency
Codes assigned by ATC
Most codes above can be selected by aircraft if and when the situation requires or allows it, without permission from ATC. Other codes are generally assigned by ATC units. For IFR flights, the squawk code is typically assigned as part of the departure clearance and stays the same throughout the flight.VFR flights, when in uncontrolled airspace, will "squawk VFR" (or conspicuity code in the UK) (1200 in the US, 7000 in Europe). Upon contact with an ATC unit, they will be told to squawk a certain unique code. When changing frequency, for instance because the VFR flight leaves controlled airspace or changes to another ATC unit, the VFR flight will be told to "squawk VFR" again.In order to avoid confusion over assigned squawk codes, ATC units will typically be allocated blocks of squawk codes, not overlapping with the blocks of nearby ATC units, to assign at their discretion.
Not all ATC units will use radar to identify aircraft, but they assign squawk codes nevertheless. As an example, London Information – the Flight Information Service station that covers the lower half of the UK – does not have access to radar images, but does assign squawk code 1177 to all aircraft that receive a FIS from them. This tells other radar equipped ATC units that that specific aircraft is listening on the London Information radio frequency, in case they need to contact that aircraft.
1 comments:
makasih info nya, hampir lupa tuh untung diingetin....
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