8.33 explained

So, VHF Airband 108.000MHz to 137.000MHz used to be divided up by 25kHz. So from 108.000 the next would be 108.025, then 108.050 etc etc right the way through. Now it’s different it’s spaced by 8.33khz. So before pilots would be told to enter the frequency in their radio, this would be the frequency the transmission was centred on and the bandwidth would be 25kHz centred on the frequency…. however now ATC give the channel! If it’s in the 25kHz spacing the radio does the same, but if it’s a 8.33 Chanel it narrows the bandwidth and transmits on the real frequency of that channel. So if they set 118.400 that’s 25kHz so it says transmit on 118.400 frequency at 25kHz bandwidth BUT if they are told to enter 118.405 that says transmit on 118.400 BUT change the bandwidth to 8.33kHz. So Channels 118.400 & 118.405 are both the same frequency but the first has a 25kHz bandwidth and second has an 8.33kHz bandwidth. Because the bandwidth is narrower you can fit more channels in (an extra 2 for each 1 in the old system) so you get 3 for the price of 1. So Norwich Tower Channel has changed to 124.255 but the frequency (the bit you need in your scanner) stays 124.250

The problem comes with scanning when you have one of the two new channels in between two old ones. So channel 118.410 is frequency 118.4083 and if you enter that in your scanner set to 12.5/25kHz spacing your scanner will be like “what the heck” and move it to the nearest step. However if it’s in 8.33kHz mode on the band Plan it will cope!

Frequencies ending .#00/.#25/.#50/.75 are the old ones, 25kHz bandwidth/spaced, so the actual frequencies.

New ones are ending:

.#05/.#10/.#15/.#30/.#35/.#40/.#55/.#60/.#65/.#80/.#85/.#90 and are 8.33kHz bandwidth/spaced so you need to look up the actual frequency.


Air to Air


Air to Air


Air Combat Manoeuvres


The Gold Standard Transponder Mode with more features above Mode S. Along with that data they crucially send their GPS location. These aircraft can then be plotted on a map without the need for multiple receivers on the same network in different locations. These are used mainly by Airliners and some of the newer military Aircraft.


Short for Affirmative, Yes


Air to Ground


Friendly Aircraft


Angle of attack AOA is a direct measurement of what angle the airflow is hitting the wing, this angle can be increased to the Critical AOA which if exceeded will stall the wing


Air Surface (Ground)

As Fragged

As briefed


Automatic Terminal Information Service: An looped voice recording of airfield and weather information available to pilots on a separate frequency. This means they can get airfield information inbound or before startup without having to use an Air Traffic Controller or waste time on a main frequency. It will remain the same recording on a loop until a new one is issued, it will be prefixed with the time of issue and a letter number ie “Information Code Alpha, timed at 0800 Zulu.” When an Aircraft hands over the controller will normally ask: “Do you have information Code Alpha?” If not or if they have a previous ATIS Code the controller will normally update them on that frequency with the latest information.


Air Traffic Service Unit, A Unit offering Air Traffic Services


Aerodrome Traffic Zone, an area depicted on charts around an airfield. It extends to 2,000ft above Aerodrome Level (AAL) with either a 2nm or 2.5nm radius depending on the length of the longest runway.


Amplitude Modulation: A Modulation Type. Airband is nearly always in AM. Technically it’s the modulation of a wave by varying its amplitude.


Short for Auxiliary Radio, generally an American Term for the Radio in Fast Jets used for things like Air to Air/Interplane communication. Generally they will refer to their radios as “Prime & Aux” (Primary & Auxiliary) where UK forces tend to use “Front & Back”


To request or provide a response for a coded challenge


Basically a Radio repeater System, where a Radio on a Ship or Aircraft can “repeat” a signal to give it further range. I believe their are different settings but usually it will receive a broadcast and almost instantaneously re-broadcast it on another frequency, it can then do this in reverse to get the reply back to the originator


Where an aircraft will taxi against the Landing direction in order to either Line up for takeoff or depart the runway onto a taxiway


Enemy Aircraft


Information/directive to execute launch and defend tactics


Basic Fighter Manoeuvres


A Minimum Fuel state, calculated so that if the aircraft has not been cleared to land by, it should divert to the designated diversion airfield, in order to have enough fuel left to land at minimum landing fuel.


The callsign for CRC Scampton, see CRC


An unidentified Aircraft


Stands for Bearing, Range, Azimuth, Aspect and is used for relaying the location of a Contact, from the position of either bullseye or the receivers position. An example from Bullseye for the following….

  • B: 150 (Degrees)
  • R: 30 (Nautical Miles)
  • A: 3000 (ft AMSL)
  • A: Northbound

Would be heard as: “Bullseye, 150, 30, 3000ft, Northbound”

Break Away

Tanker or receiver requires immediate disconnect is required


A common reference point where object locations will be given in reference from. Locations of these objects will be given in Bearing and Range from Bullseye, often by AWACS


Combat air patrol (CAP) is a type of flying mission for fighter aircraft. A combat air patrol is an aircraft patrol provided over an objective area, over the force protected, over the critical area of a combat zone, or over an air defense area, for the purpose of intercepting and destroying hostile aircraft before they reach their target. Combat air patrols apply to both overland and overwater operations, protecting other aircraft, fixed and mobile sites on land, or ships at sea.


Close Air Support


CASualty EVACuation


Ceiling and Visibility OK. No significant cloud below 5,000ft, Visibility at least 6miles, no precipitation or storms


The Line going down the middle of the Runway, along its length. It can also be used in terms of an “extended centreline” which is where the line would be “virtually” if it continued beyond the end of the runway


Control & Reporting Centres, as part of ASACS the CRC’s watch the UK skies to ensure no aircraft are flying abnormally or no unidentified aircraft are heading for the UK on Primary Radar. There are two Secure CRC’s in the UK, “Blackdog” at RAF Scampton and “Hotspur” at RAF Boulmer. If they designate a Track as a Target of Interest “Zombie” they will gather as much information as possible and report this to the NADOC at RAF High Wycombe. They will scramble QRA if needed and co-ordinate and task air assets as required. They control Aircraft in the tactical environment on Frequencies called TAD’s (Tactical Air Designators)

Cleared Hot

Cleared to drop ordnance


Not Active

Colour Code

Military Colour Code System applied to airfield weather to signify cloud height, visibility and service state


Digital Automatic Terminal Information Service: A digital voice automatically reading electronic information out on an ATIS rather than a recorded Human voice, see ATIS

Diversion Airfield

All military flight sorties will have pre designated a diversion airfield for their sortie. When discussed as Station Diversion, Sortie Diversion etc it is often because the diversion airfield has changed, not that they are intending to diver (unless otherwise stated)


Drop Zone


Estimated Time of Arrival


Estimated Time of Departure

Fence (In/Out)

Set cockpit switches as appropriate prior to entering/exiting the combat area (mnemonic for fire-control system/ECM/navigation/communication/Emitters)

Flight Levels

Height in hundreds of feet. For Example 10,000ft is FL100. Due to Aircraft using Air Pressure to work out height they use a Standard Pressure Setting of 1013hpa to ensure they are all on the same setting when they are all using “Flight Levels.” For this reason it is rarely the actual height above the Ground or indeed Sea Level as Air Pressure goes up and down depending on the weather conditions. For these reasons only aircraft over a certain height fly at Flight Levels, this height is called the Transition Level.


Frequency Modulation. A modulation type, Airband is nearly always in AM instead. FM tends to be used for ground handhelds only and not to or from an aircraft. Technically it is the encoding of Information in a carrier wave by varying the instantaneous frequency of the wave.


Simulated or Actual Launch of a Weapon. 1 is Air to Air, 2 is Infrared Guided Missile, 3 is Active Radar Guided Missile. Fox Mike means FM Radio


General Aviation


Ground-controlled interception: An air defence tactic whereby one or more radar stations or other observational stations are linked to a command communications centre which guides interceptor aircraft to an airborne target.


General Handing: General flying manoeuvres in a given area, normally assigned, or in a requested altitude block.


G Force Induced Loss of Consciousness


Helicopter Landing Site

Hotel Fox

HF Radio

Holding Hands

Aircraft in visual formation


The Callsign for CRC Boulmer, see CRC


International Air Transport Association


International Civil Aviation Organisation


Instrument Flight Rules


Instrument Landing System: A Precision approach method relying on complicated ground equipment to provide an aircraft on approach a picture of where it is in terms of glideslope and centreline. It also provides a distance measure at significant points as the aircraft passes over Markers. Pilots do not need to see the ground until at the minimums set for that class of aircraft. Due to it being a precise method of navigating it can help pilots land in bad weather are not required to see the runway until a lot later and lower in the Approach than normal.


Instrument Meteorological Conditions (Also referred to as “India Mike”)


In Season Practice – A display practice performed inside the Display Season after gaining PDA


A pre-determined fuel calculation that signifies the point Operations need to conclude by in order to proceed back to home base and successfully undertake an missed approach, a successful approach before reaching Bingo Fuel. See Bingo Fuel


A friendly track of interest

Knock it off

Safety directive to cease air combat exercise/manoeuvres/attacks/activities


A Lower Airspace Radar Service (LARS) is a free service available to all aircraft for the provision of the radar element of UK Flight Information Services (UK FIS). This is usually available within approximately 30 nm of each participating Air Traffic Service (ATS) Unit to all aircraft flying outside controlled airspace up to FL100, within the limits of radar/radio cover.

Line Abreast

Side by Side


Landing Zone


A Callsign used by AWACS Controllers to control aircraft. Often referred to as the “Backseaters” in an AWACS as the Flight Crew will operate under a different Callsign with an ATSU, often under “NATO” Callsigns.


Military Air Traffic Zone: An area depicted on charts around a military airfield. It extends to 3,000ft above Aerodrome Level (AAL) and has a radius of 5nm.


An additional area of the MATZ with a width of 4nm, extending a further 5nm along a final approach path for main instrument runways and extending 1,000ft to 3,000ft above Aerodrome Level.


MEDical EVACuation


An Actual Meteorological (Weather) Report published electronically from an Airfield. Usually every hour and usually Automated, it’s a snapshot of the weather at a certain time. It is given in a form of abbreviation/shorthand that can be difficult for the average person to understand but many apps and sites will “decode” this information to make it easier to interpret.



Mode 1

A Military Transponder Mode that automatically replies electronically to interrogation with a 2-digit 5-bit mission code entered into the Transponder by the pilot.

Mode 2

Transponder Mode that automatically replies electronically to interrogation with a 4-digit octal unit code.

Mode A

Technically Mode 3A is a Transponder Mode that automatically replies electronically to interrogation with a four digit number set by the pilot in the Transponder. These use the numbers 0 to 7 and not 8 and 9, they are often called Squawks

Mode C

Technically Mode 3C is a Transponder Mode that automatically replies electronically to interrogation with the aircrafts pressure altitude (Set to SPS 1013.2hpa) it is often combined with Mode A as a Mode 3A/C Transponder.

Mode 3 A/C

Combines mode A & C replies. These transponders are generally used in General Aviation Aircraft as they are one of the more basic Transponder modes, with Mode S and ADSB offering more features. Generally speaking Mode 3A/C Transponders can not be tracked because they don’t offer any “identification code” unique to one aircraft. The same Squawks and indeed same altitudes could be coming from another aircraft so it’s hard for tracking websites to be sure if it’s one aircraft or more they are getting data from.

Mode S

An enhanced Transponder Mode with more features above Mode 3A/C. Along with that data they crucially send their identity in the form of a Hex Code, with these code ranges allocated by the ICAO internationally and can be looked up on a database to get aircraft information such as Registration/Serial. Therefore computers can, with reasonable certainty, know which signals are coming from that one aircraft. We can then track them by working out their location by MLAT. However it’s crucial to understand Mode-S Transponders do not send their location out like ADSB Transponders so this MLAT calculation will generally need to be in range of 5 receivers on the same network to locate them. Mode-S Transponders span General Aviation, Military and Light or Older Commercial Aircraft.

Mode 4

A Military Transponder Mode that automatically replies electronically to encrypted interrogation with a 3 pulse reply.

Mode 5

A Military Transponder Mode that uses encryption and automatically replies electronically with, essentially, a secure version of Mode/S and ADSB.


Minimum Descent Altitude and is referenced to mean sea level


Minimum Descent Height and is referenced to the aerodrome elevation


Minimum Separation Distance


National Air Defence Operations Centre, the former name for NASOC:


National Air and Space Operations Centre, based at RAF High Wycombe. Responsible for the Defence of the UK’s skies. They receive intelligence from the CRC’s and are the people who will speak to the Designated Government Minister, briefing them on the threat and receiving their instructions.


NOTIce to AirMen: A Notice of occurrences that may affect air activity in a given area (think a digital notice board for Pilots.) Primarily for flight safety but to aid in coordination between air service users. As Open Source Information it can be useful for Enthusiasts to gain more information about an event like time, location or route. They often use an agreed set of abbreviations sometimes making them difficult to interpret. But don’t worry too much as we tend to put the important ones on our Diaryanyway!


Operational Control: In radio terms operational information or Operational Control Frequency or Company Frequency (Not Air Traffic Controllers controlling aircraft)


Out of Season Practice – A display practice performed outside the Display Season prior to gaining PDA


Precision Approach Radar: A Precision approach method relying on dedicated RADAR that can measure where an aircraft is on the Approach in terms of distance glideslope and centreline. A Talkdown Controller Can then give the Pilot this information, alongside corrections to talk them down on approach. Pilots do not need to see the ground until at the minimums set for that class of aircraft. Due to it being a precise method of navigating it can help pilots land in bad weather are not required to see the runway until a lot later and lower in the Approach than normal.




Practice Diversion to another airfield to perform one or more approaches. Often used in terms of a “PD Booking” where a sortie has pre booked a PD to perform one or more approaches at the respective airfield.


Public Display Authority – For Military Display Teams they practice until a week or so before the Summer Display Season starts. They are then assessed by a Senior Officer (AOC 22 Group for the Red Arrows) where displays are observed, SOP’s checked, briefings observed and they deemed fit to safely display for the public and are granted their Public Display Authority for the season. To keep this authority live a minimum number of displays must be flown in a given timescale, usually 1 Display in 7 days.


A request for tactical information, often used by fighters to AWACS requesting “Picture”


Positive Identification

Primary Radar

What we generally think of first when we say Radar, a Radio Signal sent out, to bounce off aircraft surfaces and be returned, in order to determine their range and bearing from the Radar Head


Change frequency to stated frequency/channel/Stud


Air pressure at Aerodrome elevation. To be entered into an altimeter so it so shows aircraft height above the Airfield elevation. This is used for landings, takeoffs and circuits as when on the ground the altimeter would read (approx) 0ft and otherwise height above aerodrome level (AAL).


Air pressure at mean sea level (MSL). To be entered into an altimeter so it shows aircraft altitude above MSL, as altimeters work off air pressure. Good for terrain avoidance when flying low as ground and ground features (Masts etc) are shown in chart in AMSL (Above Mean Sea Level) For a QFE Approach you need to know the Airfield Elevation as your altimeter won’t read 0ft on the ground with QNH set, it will read the airfield elevation at that point on the ground. For this reason approaches are normally flown on QFE.


Quick Reaction Alert: Where crews are on standby to quickly react to a tasking. Mostly used to describe the Typhoons on Standby in an air defence role. In the UK there are two QRA Stations, North and South, North at RAF Lossiemouth and South at RAF Coningsby. QRA’s operate on TAD’s (Tactical Air Designator) used for things other than QRA as well. Hotspur is the Callsign for CRC Boulmer & Blackdog for CRC Scampton (Control & Reporting Centres) one of which will generally communicate with the QRA Birds. A QRA Aircraft Callsign will be a mission code consisting of 5 letters & numbers and accompanied by a Squawk Code in the range of 1301-1327 designated as NATO Air Policing. Interceptors will be Typhoons from QRA Station North at RAF Lossiemouth or QRA Station South at RAF Coningsby. A tanker will be tasked to support, usually but not always from Brize unless they re-task one already in Flight, occasion an E3 Sentry May also be tasked depending on the needs of the mission. More about QRA’s

Red Arrows Tracking

Red Arrows use Mode A/C transponders most of the time which can’t be tracked. Jet XX242 has Mode-S which can be tracked at a reasonable altitude with an MLAT network such as 360radar, however it’s only on a handful of times a year unfortunately, so it will show, just not often. The Aircraft Hex Code (Unique ID) is within the UK Military Range and a lot of commercial Civil Aircraft tracking services block out that block of codes. I have seen it show on some but it’s unclear if they have allowed it through on a one off basis or as a more permanent exclusion to their usual military blocking policy. You may also see “RED10” on a Juno (Previously Squirrel) Helicopter used as a Shuttle for RED10 back and forth to Display sites in season for commentary etc. The easier transponders to track ADSB/FLARM are not carried.


Rolling the time of given exercise by a number of Minutes from the original time


Regional Pressure Setting: The forecasted pressure (QNH) at mean sea level (AMSL) for a designated area. Used when not operating at an airfield but flying below the Transition Level where the Standard Pressure Setting would be used to fly at Flight Levels


Return to Base


Essentially a receive only radio designed to search a list or range of frequencies really quickly and stop on an active frequency allowing to to hear to transmission. If you are looking to purchase one ensure if covers the Military (UHF) and Civil (VHF) Airbands at a minimum. As they get more advanced they become faster and offer better features such as being computer programmable/controllable.


Standard Operating Procedures – Procedures for a given task, it’s often said SOP’s are written in blood as they are often shaped from mishaps of the past and lessons learnt from accidents. They have usually been developed and refined over the years to ensure safety and compliance with any relevant legislation.


A NATO brevity codeword signifying a System is not operational as expected


A NATO brevity Codeword meaning: An interrogated group/Radar contact which lacks the Air Tasking Order established (or equivalent) IFF Modes and codes required for identification criteria.


A four digit Mode 3A Transponder Code. As there are reserved squawk ranges for ATSU’s or certain purposes Squawk Codes can often tell you who an aircraft is speaking to or what they are doing. It is therefore worth turning on the squawk label on tracking sites, a full list is provided on our Squawk Codes Page


Surveillance Radar Approach: A Non Precision Approach by using the normal Surveillance Radar to give a controller a picture of where the aircraft approaching is and allows to pass on this information and correction to Pilots over the Radio. It is similar to a PAR but less precise. It aids the Pilots in bad weather as they do not have to be visual with the runway throughout the Approach, there will be set minimums at which the Pilot needs to become visual with the Runway to complete the Approach, but as it’s not as precise as a PAR approach using dedicated Radar for this purpose a pilot needs to become visual further out and higher up than a PAR or ILS approach.


Secondary Surveillance Radar. A signal sent out from a Radar Head to interrogate an aircrafts Transponder and illicit an automated reply


UK lingo for a Preset Channel Number


NATO Brevity Codeword signifying a System is working correctly or data link information has been received


Tactical Air Designators, Frequencies for the tactical control of air assets. In the UK TAD’s are managed by the CRC’s and allocated to Taskings. They are generally assigned three digit numbers, such as “TAD 140” to avoid having to give the actual frequency over the air.


A UHF Radio Navigation Beacon providing distance and bearing information for Navigation. TACAN is a military system for Radio Navigation accepted as being more accurate than its civil equivalent. The Beacons are mainly located at Airfields as Static beacons however they can also be located on Ships or Aircraft.


Pre determined lines for Navigation based around TACAN Beacons


Terminal Area Forecast. A weather forecast electronically published by an Airfield. It is published in a form of abbreviation/shorthand that is difficult to understand however most apps and websites will “decode” the information to make it easier to interpret.


Visual Contact


Air refuelling Aircraft. The RAF use Callsigns MADRAS/TARTAN Number Should be Day of Week then Sortie Number.


NATO brevity codeword for the Link 16 Data Link System.


Time on Target



Transition Level

A level at which aircraft set their altimeter to 1013.2hpa and fly at Flight Levels, See Flight Levels


Is a device in the cockpit that automatically replies electronically to interrogation with certain information, depending what it is asked for and what modes it is equipped with (See Modes 1 to 5) now “extended squitter” Transponders are becoming cable of sending information without even being asked.


Ultra High Frequency: Technically any frequency between 300MHz & 3GHz. However when we talk about UHF Airband we mean the 225MHz to 399.95MHz (Yes I’m aware a chunk of that is technically VHF and above 380MHz you will get a lot of non Airband signals) Aircraft that use UHF Airband are generally Military however some Civil Airfields and Aircraft may be fitted with UHF Radios. When discussing UHF on the Radio it may be referred to as “Uniform” in questions such as “Can you confirm that you are Uniform equipped?”


UK Low Fly System (Military) The UK is divided into Low Fly Areas, See Charts


UK Night Low Fly System (Military) The UK is divided into Low Fly Areas, See Charts


Visual Flight Rules. A set of rules of the air that allow you to fly and navigate by visual clues in better weather (See VMC) essentially the Golden Rule is to see other aircraft and avoid them, rather than allowing on Rules, instruments and Air Traffic Controllers to keep you out of trouble. Crucially you are not allowed to fly in certain classes of controlled airspace to VFR. VFR are the basics of flying and allow Pilots to qualify as a Pilots but be restricted to these rules in better weather.


A magnetic heading


Very High Frequency: Technically any frequency between 30MHz & 300MHz. However when we talk about VHF Airband we generally mean just the Airband portion of this which is 118MHz to 136.975 MHz. This can also be called Civil Airband as it’s Mostly Civil Aircraft that use it although Military Airfields and Aircraft will use VHF Frequencies too. When discussing a VHF radio on Airband, they may refer to VHF frequencies as “Victor” Frequencies. There is also a VHF Low Band which is far less commonly used which is probably around 30MHz to 87.975MHz.


Visual Meteorological Conditions (Also referred to as “Victor Mike”)


A common type of Primary Radar System the RAF use


WILL-COm -ply


Aircraft is out of Ordnance


Directive or Interrogative regarding further information or directives pertinent to the mission


Air to Air TACAN


A suspect track


Time in GMT