Fly On Track


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Addtional information

Did you know, a large commercial aircraft delayed by an infringement can cost £100 per minute in direct costs alone?

Radar Replays

Airprox Report (radar derived diagrams)

This Airprox Report illustrates it is not just infringements of controlled airspace that matter, this Airprox was after an infringement of an ATZ.

1. Radar Heathrow CTR – Commercials Vectored Away

This whole sequence is a classic example of standard safety measures in action because an ‘G.A. Infringer’ enters into Heathrow Class ‘A’ Airspace. When you play the radar replay, (click on the link below), you will see the DISRUPTION caused by an unknown aircraft entering the Heathrow CTR from the North.

You may need to replay the sequence more than once, there is so much happening. To help you identify him, the infringer will be highlighted with a white circle. Note he is squawking 7000, the general conspicuity code, but he is not revealing his altitude which should be shown where the three dashes  are. To understand the data on the commercial aircraft, pause the replay and look at any green ‘*’ which represents a aircraft approaching or leaving Heathrow. The ones on the last stages of their descent inbound will have a green number, representing the altitude in HUNDREDS of feet (so ’43’ represents 4300′),and a green ‘LL’ representing Heathrow (ICAO code EGLL). The orange/brown number trailing some flights is the altitude that the aircraft is descending to at this stage. So a ’43’ with an orange/brown ’40’ trailing it shows the aircraft passing 4300′ on the way to 4000′.

Heathrow CTR will be highlighted as the incident progresses. Commercial aircraft can be seen as they are aligned up for landing on runway 09L at Heathrow, the actual threshold being where that designator 09L is seen. The checkpoints on final approach are at 2 mile intervals. Keep your eye on squawk 6645 as it descends on the ILS, it is the first to be broken off. The 7000 squawks in the White Waltham circuit and the low level 7037 SVFR transit can be ignored. Each commercial under Heathrow control will have a unique 4 digit green squawk number. The green ‘*’ on some of the departing ones will be seen to blink, as they are asked to squawk ‘ident’.

As the infringer moves South towards the well spaced commercial traffic lined up for landing on 09L at Heathrow, the controller, unable to contact the infringer, has no option but to break off two aircraft from final approach to a runway… That’s why controllers are there… they enforce safety by taking action.That’s why controlled airspace is there… to give a defined ‘known environment’ to protect commercial flights. If anything ‘unknown’ enters that environment, then set procedures ENSURE that safety is not compromised, and the casualties are ‘time’ and ‘cost’ (and perhaps patience if you were a passenger on board with a tight transfer, or a train to catch, or just wanting to get home after a long day). If you are interested in direct costs, think of each minute of extra flight time suffered by the aircraft broken off approach and re-sequenced into such as busy stream as being in the order of £100 per minute and you won’t be far wrong.

Whilst the real incident shown here was not a ‘safety’ problem due to the diligence of the controllers and their processes, the most likely incident that could lead to safety problems would be an infringer without ‘Mode C’ breaking into controlled airspace from below or above – for example climbing into the LTMA from below either not transponding, or simply forgetting to turn the transponder to ‘ALT’. Always use Mode C if you have it. What do you do if you suddenly realise you are in Controlled Airspace? Call the controller as quickly as possible, as you can then quickly become ‘known traffic’ and other flights might not need to be diverted once you are identified and the situation is being resolved. If you do not know who to call, don’t wait for things to get worse, use 121.5 Mhz, tell them your problem, and the situation will start to improve for everyone.

To see the Heathrow CTR bust click here G.A. Bust of Heathrow CTR (3.2 Megabytes)

2. Radar Compton VOR

This replay shows an aircraft not noticing the levels of controlled airspace and is infringing throughout. The airspace lowers further ahead near Compton VOR. One aircraft out of Luton is re-routed when the infringer is noticed, and there is loss of separation against a Heathrow departure. The clip is well annotated.  If you don’t understand the way the squawk data such as flight levels are shown on the replay, the description of the Heathrow CTR ‘bust’ (below) explains it, but the ‘7000’ squawker is initially annotated as being at 9100′ (see the ’91’ under the squawk) and eventually ends up at 8300′ by the very end of the clip. NMS means ‘no mode S’.

Radar video clip for Compton VOR  (2.5 Megabytes)

3. Radar Stansted CTA – No Mode Charlie!

This replay shows an incursion and incident when a pilot, ‘temporarily unsure of position’, is actually in  Stansted CTA. The lack of Mode C from the transponder is the main problem here. Play the radar replay once to see what happens, then play it again pausing where necessary, knowing that the aircraft was at around 3000′, give or take. Note because the infringing aircraft could be clear of the airspace if below 1500′, the controller has to assume it is down there, and has no idea that the 7000 radar return is so high. The squawk on the Stansted “inbound” shows its altitude in hundreds of feet. You will see two fields with ‘2 digits’ on the squawk – the one in green is the current altitude in hundreds of feet, the other (usually lower in value) is the altitude it is currently intending to reach – so ’41’ and ’30’ in the two 2-digit fields would be at 4100′ descending down to 3000′. If you are wondering why they want a TMZ under the Stansted CTA, look no further than this:

View the replay of Stansted CTA without Mode C (1.8 Megabytes)

4. Radar Gatwick/LTMA

This radar replay.shows disruption caused by a short infringement into a layer of the LTMA over Sussex, eventually descending to the correct altitude but not early enough. The altitude of the aircraft is shown as two digits on the radar replay. For example, at the very start of the clip, the aircraft that will infringe is squawking ‘7000’ with the Mode C showing ’30’ meaing 3000′. You can watch that altitude decrease too late. Once the aircraft has infringed, the controller has to assume he does not know what he is doing, and is ‘unpredictable’ in both heading and altitude changes. For that reason, any traffic nearby has to be vectored away.

Descending in time does matter, it’s no good saying you only went in by a short distance, as soon as you cross that line, the controller has to move traffic as the assumption has to be that you are lost and your track is unpredictable – why else would you have crossed that line at all?

Gatwick LTMA Radar Replay video (2.5 MB)

5. Radar Luton CTR

This replay shows a student lost and crossing the Luton CTR and extended runway centre line. Note that when the student realises (shortly before the runway) and he is given a Luton squawk, he doesn’t use Mode C, which he should!

View the radar replay for Luton CTR

6. Radar Stansted CTR

This replay shows a small aircraft slowly transiting Stansted CTR. It is annotated as the clip plays. The worrying thing is that because he is slow and in a very light non-reflective aircraft, he was never seen until he realised what he’d done, just at the very end of the ‘film’ when call called the controller. You see the radar blip much clearer as it is speeded up and therefore not intermittent.

Stansted Intrusion Slow Moving  (5.4 Megabytes)

7. Radar Manchester CTR

You’ll see an aircraft (in fact more than one) leaving the Manchester Low Level Route into the CTR. The clip is annotated to explain the disruption that results.

The radar replay shows the south western section of the Manchester Control Zone. Manchester Airport is using its north easterly runways (landing runway 05R and departing runway 05L). At the start of the replay Manchester Airport, the 10 mile range ring from the airport and the final approach track for runway 05R are all highlighted. At the time of this incident traffic levels were high, notice there is a continuous sequence of inbound aircraft that are being vectored for approximately 4miles spacing on final approach also out of picturethere are several aircraft at the 3 Manchester holding stacks waiting for their turn to make an approach.

The infringing aircraft was traced by tracking it on radar and actually turned out to be 3 aircraft that were flying in loose formation (only one was squawking but if you watch the replay again you can make out the primary radar returns from the other 2 aircraft). The 4 aircraft broken off approach were all delayed by 8 minutes but also 10 aircraft that were already in the holding stacks were also delayed 8 minutes. This gives a total delay for all aircraft of 2 hours and if you consider the average size of the delayed aircraft involved was a Boeing 737 (which burns around 2.5 tonnes of fuel an hour while holding) it’s a costly business.

OK, so the controllers did pretty well, keeping the impact to just time and money, not lives, but here’s another learning point; If the 7000 squawk has been simply listening in to Manchester Approach on 118.575 Mhz and displaying the Manchester ‘listening in’ squawk of 7366, it could have been contacted as soon as it left the corridor

Now watch the clip: Radar video clip for Manchester LLR (5.9 Megabytes)

8. Radar- Luton. See “CAIT”! How it should be…

This is how it should be… an aircraft accidentally infringes ‘vertically upwards’. The pilot has previously decided not to talk to anyone but wear a listening squawk. It’s all over with no fuss after about 30 seconds.To understand the readings from the transponder, see the explanation that goes with the first radar replay, Heathrow CTR, below.

The pilot is squawking a ‘listening squawk’ 0013 to show he is monitoring the Luton Approach frequency without speaking. Not only is he showing a ‘listening squawk’, he’s using Mode Charlie (‘Alt’) to transmit level. Note the infringement is vertical, a climb into the CTA.

The new LTMA software ‘CAIT’ is in use, which monitors squawks and “Mode Charlies” turning a radar return ‘purple’ if it believes there is an infringement happening. (Normally the controller would have to notice which would happen but not as quickly as if a ‘return’ turns purple.) We cannot broadcast the sound track, but we overlay the radar replay with what is going on between the controller and the pilot.

When the sequence starts, the purple 0013 squawk is obvious, the pilot is climbing. At the time it shows ’38’, i.e. the aircraft has reached 3800′. Unfortunately the sector of CTA shown here around the Henton NDB has a base of 3500′. (NB: the text on the radar replay says this is the Luton CTR, it isn’t, it’s the Luton CTA so traffic is allowed underneath it in Class G.)

Without the ‘Mode C’, the infringement would not have been noticed as the controller and CAIT would have deemed the aircraft to be below the CTA, and an airprox or worse could result. Without Mode C, if the aircraft had been spotted visually by a commercial and reported, the deliberate non-use of ‘Mode C’ when it was available could influence whether the pilot ended up in court or not, as it would appear that the airmanship was lacking. But, so much for ‘ifs’, this pilot was using Mode C, and as you’ll see, through CAIT instantly highlighting the problem, and the ‘listening squawk’ showing the controller that the pilot is quietly monitoring the frequency, it’s all sorted out in what? About 30 seconds? No danger, no fuss. Nowadays, as we need to understand the detail behind infringements, the pilot would be asked to volunteet to fill in a standard survey format, which of course leads to the sort of analysis over time that appears on the ‘Statistics’ page here.

And yet, in my experience, you will still find pilots who deliberately avoid using Mode Charlie when they have it! Don’t risk lives or needless follow up – if you have Mode C, use it!

Now click here to see the radar replay: CAIT and A Listening Squawk Save the Day (3.2 Megabytes)

9. Radar Birmingham. Controller worked hard.

At sometime in the past year or so, have you been a passenger on a commercial flight coming into a UK airport with a CTR? What do you feel like when you have tight travel connections to make, everything looks good. and you suddenly realise at the last minute that the aircraft is not going to land on time? Even if you haven’t travel connections, it’s bad enough, you just want to land and get home.

What you don’t need is controllers working at an unnecessarily high (unplanned) workload sequencing your flight inbound – they can work like that if they have to, that’s in the training and skill, but because your safety is the priority in such situations, it all translates to ‘delays’ for you. The same applies to departures – and of course, it’s not just you and the numbers on your flight, if your aircraft is on short-haul routes, its utilisation that day will be high. The people on its last flight of the day might have an unexpected extra night away due to the ‘knock on’ effects. And I haven’t mentioned extra fuel wastage and costs.

Just think, if the pilot on this infringement had been using a Birmingham ‘listening squawk’ of 0010 and listening out on 118.050 MHz, then this incident would have been over in the first few seconds of the clip, (although the clip would never have been needed), saving all the trouble, follow up, etc. but instead, we’ve got one light aircraft, one CTR infringement – it’s no disaster movie in the conventional sense, but for 100s of passengers, it was, but thanks to controller skill, but only in a ‘delay’ sense.

Delays in Birmingham CTR  (5.1 megabytes)

10. Radar -Fifteen Minutes of Disruption in Stansted CTR

‘Seeing is Believing’ – This is the radar replay referred to in ‘Clued-Up’ 2011.

An aircraft sets off from Earl’s Colne airfield to Rochester via the Stapleford overhead. Due to misidentification of towns, the aircraft finally arrives near North Weald after a 15 minute occupation of the Stansted CTR which seriously disrupts operations.

The mystery and problem is finally solved when the pilot calls Farnborough North. The (student) pilot has had the transponder off up to that point, and you can see how the radar contact is not obvious at times as others with transponders working – and the controllers have no idea of ‘level’. The video is annotated to show each mistake in mis-identifying visual clues. If you see any fast moving ‘dot-contacts’ without squawks, these are filtered-out high level aircraft. Here’s the link, but if you are on limited downloads, be warned this is a lot of data – some 18 meg playing time just over 4 minutes, (speeded up 4 times).

Fifteen Minutes in the Stansted CTR

11. Graphical Radar. 2 Infringements causing major disruption at Stansted and Heathrow

This video, created from two radar traces of two separate incidents, is here to show the disruption to commercial traffic – remember the videos are speeded up considerably. Click here to see them