New guidance on unknown traffic in Class D [Archive]

2 sheds

20th Nov 2004, 21:49

If your Class D airspace is a CTR, then by definition it extends upwards from the surface. Therefore, any radar return (not a "contact", please) within the lateral limits that cannot be associated with known traffic must be within the airspace (or the airspace above it) and therefore must be considered to be lost or making an unauthorised penetration.

In the case of a Class D CTA, in the absence of other information, unknown traffic would be assumed to be obeying the law and be flying below the CAS. However, if it were squawking on mode C and the level readout, albeit unverified and possibly corrupt, would put it inside the CAS, I would suggest that, again, that constituted evidence to suggest lost or unauthorised penetration.

Standard Noise

20th Nov 2004, 22:00

Yep, pretty much agree with 2 sheds. However, I always tell the inbounds about the traffic's position and add "no mode charlie but believed to be below the base of CAS." I'm afraid the ATSIN won't change me there.
Saves the poor sod upstairs from having a pink fit when his inbound at 5.5D tells him a tiddler has just passed in front of him at a similar level. (Our CTR extends 5 miles out from the field with a stub E&W from 1500' upwards)

Chilli Monster

20th Nov 2004, 22:01

Turn It Off

21st Nov 2004, 05:17

I think that any airspace which has a latarel confine, an pper or lower limit, that, any primary return is to be assumed to be either above or below.

However, if it were squawking on mode C and the level readout, albeit unverified and possibly corrupt, would put it inside the CAS, I would suggest that, again, that constituted evidence to suggest lost or unauthorised penetration.

Agree totally, if its got Mode C use it, just lob in the unverified bit with the traffic avoidance.

TIO

HEATHROW DIRECTOR

21st Nov 2004, 07:32

<<Now it's no traffic info or avoidance unless you know there's an aircraft lost, infringed your airspace or had radio fail. But who's going to take that risk?>>

That's always been the rule with Class A airspace so what's the problem?

DFC

21st Nov 2004, 09:05

So if I don't bother to call for clearance to transit a zone, have a perfectly good radio and to avoid snoopy radar, I turn off the mode A and C, I will have to keep a bloody good lookout because the ATC will not try to keep pesky jets out of my way. I am not lost and I don't have a radio failure.....I just can't be bothered! :E

Better still, if the zone has calss G above, I can leave the mode C on and when the heavies call, tell them that the mode C was discovered to be U/S after the flight and is now fixed!

Seriously, I can't think of an occasion where ATC would intentionally point an aircraft at a radar return which could be within their airspace without atleast warning the pilot.

If the UK had the ICAO VMC minima for Class D airspace i.e. aircraft would have to be 1000ft vertically and 1500m laterally from cloud then I would probably find it easier to accept the situation............most zone infringements are by flights under VFR. The reason being that as I exit the base of a cloud the closest VFR aircraft would be 1000ft below. However, in the UK Class D, the VFR flight could be hugging the base of the cloud!

When in Class G we operate above 3000ft i.e. in the FLs for as much as possible when IFR for the very reason that VMC flights have to keep well away from clouds at those levels.

Regards,

DFC

DFC

22nd Nov 2004, 20:14

This post has got me thinking.

Can any ATS person tell me.......if the ICAO VMC minima for Class D were set because VFR are not separated from IFR i.e. is the intention to keep VFRs well away from cloud so that the IFRs can spot them after popping out of the cloud at 250Kt..........or is there another reason why the minima are such?

Regards,

DFC

Tower Ranger

22nd Nov 2004, 21:51

I`d suggest that if you still work in the dark ages of primary only as we have you surrounded by D,E and G airspace then your gonna pass traffic info and make sure th blips don`t merge. Regardless of whether you think its one of the lighties you`re talking too you`d be a bit daft to assume the ident.
Is the definition of " known traffic " still the same?

Turn It Off

23rd Nov 2004, 05:36

DFC,

This doesn't really answer your question fully but it might help a little.

For a pilot to maintain VMC they must be 1000ft below cloud, 1500ft horizontally from cloud. Whether or not this is to help people gain visual reference with eachother when an IFR a/c breaks cloud I don't know.

However, the spanner in the works,

Below ALt. 3000, an aircraft with a TAS of 140kts or less only has to remain Clear of Cloud and In Sight of Surface, which means that VFRs can get out in very very low cloud, which would give IFR a/c little chance of spotting something, especially if traffic info hasn't been passed.

I'm at a unit based in Class D and we try and provide, where possible at Least standard seperation between VFR and IFR. Generally (Not always) we will aplly a procedural seperation ( VFR not above 1500ft, IFR descending to 2500ft), in order to provide maximum protection to all a/c involved.

Hope that helps a little

TIO

[edited 15:54 23/11/2004]

The above 'caveat' to the rules does not exempt a pilot from 5, and the met vis must be 5000m, below that a Special VFR clearance would be issued.

DFC

23rd Nov 2004, 14:35

TIO,

Taking your Class D as an example.

The ICAO VMC requirement is for an aircraft to be 1500m horizontally and 1000ft vertically from cloud regardless of height.

This means that to fly VFR at 1500ft, the cloud would have to be 2500ft or above.............unless a special VFR clearance is given.

Thus under ICAO rules, there is a provision made for the IFR guy just inside the base of the cloud (unable to see the VFR guy) to be 1000ft above them.........unless the VFR flight gets a Special VFR but then they will be ATC separated.

Since ICAO specify a minimum height of 500ft above the surface, it is impossible to get VFR when the cloud is below 1500ft.....a well defined cut-off!

Taking the UK position a VFR pilot can hug the base of the cloud literally feet away from the IFR traffic just above........all within the UK rules.

Thus as I see the position, the UK CAA has taken away an inherent safety measure included in the Class D ICAO airspace without making any requirement........other than relying on ATCOs to operate in accordance with some moral code (if they choose). This in turn makes the VFR pilots complain of unnecessary restrictions because after all ATC are not required to separate them from other traffic in class D.

Under ICAO the clear of cloud in sight of the surface only applies in class G.

Classic case of passing the safety buck?

Regards,

DFC

HEATHROW DIRECTOR

23rd Nov 2004, 14:59

<<other than relying on ATCOs to operate in accordance with some moral code (if they choose).>>

You can't operate under a "moral code" in busy airspace - it just isn't possible. When unknown traffic appeared in side the London Control Zone we used to take avoiding action - after checking with adjacent ATC units, etc. However, unidentified traffic in the London TMA was totally ignored and assumed to be below the level of our traffic.

If you ever get the chance to watch an ATC radar on a sunny Bank Holiday you'll understand the problem. Approaches into Heathrow pass over, or close to, half a dozen or more light aircraft fields and blips merge - known in Class A versus unknown outside CAS - hundreds of times a day.

If traffic info or avoiding action had to be given the system would collapse.

PPRuNe Radar

23rd Nov 2004, 16:15

I don't see your point DFC.

In Class D in the UK, the ATCO would almost without exception pass information on the VFR (he has to be in contact and obey ATC instructions after all) to the IFR. Almost without exception, they would probably build in some form of separation too (although not formally required).

In Class G under ICAO (as well as the UK), neither aircraft need be in contact with one another and the IFR can blissfully pop out of cloud unannounced straight in to the VFR hugging the cloud.

So are you are saying that a Class G collision under ICAO doesn't really matter and is just one of those things, whereas a collision of the same geometry in UK Class D does and it must be the CAAs fault ?? :confused: Both would end up with dead people.

Far from removing a safety measure, UK Class D actually adds safety compared to Class G surely ??

NorthSouth

23rd Nov 2004, 21:26

DFC:I can't think of an occasion where ATC would intentionally point an aircraft at a radar return which could be within their airspace without atleast warning the pilotAnd yet that's just what the CAA is telling controllers in Class D to do in the latest 'correction' of MATS Part 1.

bookworm

24th Nov 2004, 07:58

So are you are saying that a Class G collision under ICAO doesn't really matter and is just one of those things, whereas a collision of the same geometry in UK Class D does and it must be the CAAs fault ?? Both would end up with dead people.

The point of controlled airspace is that it is placed where it is justified by traffic density and ATS needs. In the ICAO scheme, class G would not be used in areas where such a collision was likely. The very existence of class D implies that there is increased likelihood of collision if other measures aren't taken. One of those measures is to require VFR traffic to operate with minimum separation from cloud, another is to require them to be in touch with ATC.

The current UK exemption for class D takes away the former. While traffic information is useful when it gives the IFR traffic an opportunity to see and avoid the VFR (and vice versa), there is, in the UK scheme, not guaranteed that the aircraft will have the opportunity to see each other before the moment of collision.

In essence, I agree with DFC. The modification to the class C/D/E minima was introduced without much consideration for the consequences after someone realised that the minima as originally drafted (http://www.hmso.gov.uk/si/si1991/uksi_19912437_en_2.htm) as Rule 25(b) made it operationally impossible to fly circuits at 1000 ft in class D with the cloud base below 2000 ft.

DFC

24th Nov 2004, 18:57

Radar,

Bookworm has hit the nail on the head.

I would also add that the clear of cloud bit only applies at/below 3000ft in class G. Thus taking ICAO airspace, an IFR flight in IMC operating at a level equivalent to 4000ft AMSL or more and then entering a zone for the instrument approach can be satisfied that they are atleast 1000ft vertically and/or 1500m horizontally from all VFR flights up until they become visual........and then they have time to spot the traffic..........which is why the visibility requirement is 5Km in D every height and G above 3000ft and we are limited to 250Kt..............all to give us a chance to operate the see and avoid.

Bookworm,

It is perfectly possible to fly circuits when the cloud base is 1500ft and the circuit height 1000ft under ICAO...........operate special VFR and the tower use reduced separation in the vicinity.

Regards,

DFC

bookworm

24th Nov 2004, 20:16

It is perfectly possible to fly circuits when the cloud base is 1500ft and the circuit height 1000ft under ICAO...........operate special VFR and the tower use reduced separation in the vicinity.

Yes, in the simplest case, it's clearly possible to fly SVFR if you're the only aircraft around. But if there are more than one, doesn't even "reduced separation" between SVFR flights place a rather heavier operational burden on ATC than simple VFR in the circuit?

PPRuNe Radar

24th Nov 2004, 21:56

Nope, you still have me lost.

It's 'OK' for you not to have 'separation' from traffic in Class G - the flawed big sky theory I suppose. But in Class D where traffic is KNOWN and given to you, hence at least providing you with information on something you can't see and so can adapt your profile if you so wish, then it's NOT OK ?? :confused: You seem to infer that Class D is less safe than Class G.

Class G can be just as busy and concentrated, if not busier, than many bits of Class D. But of course without the need for anyone to be in contact or their intentions known.

The argument about the below 3000' bit (as if it doesn't matter in Class G) is also a red herring as it is very applicable to many instrument approaches (South of the Lakes and outside Wales anyway), so you could still encounter a VFR as you pop out of cloud there quite legally below 3000' whilst following the chart.

Still, at 250Kts, you might get his number as you plough into the side of him ??

If anything, I would have expected pilots to be more worried about fighting to raise the limits for flight in Class G, rather than slating reduced limits in airspace where there is some modicum of 'control' and information.

:ugh: :\

DFC

26th Nov 2004, 22:06

Radar,

According to the rules, we get the same separation from VFRs in Class D,E,F and G............None!

Ideally we would never complete an instrument approach in anything worse than class E.

Unfortunately, in the UK we have to from time to time complete an instrument approach or for a period of time fly IFR below 3000ft in Class G..........in those cases we require a minimum of RIS..........and the CAA for it's part asks VFR pilots to avoid the let down areas marked on the chart. Thus a mid-air in Class G would be most likely with a pilot who ignored CAA advice to avoid the published let down area of an approach permitted to be made in class G airspace where class E would be far safer.

But the VFRs in Class G are not the real danger - the real danger comes from other IFRs who can be in the same cloud and not talking or squalking!

I believe that places like Filton and Farnborough, Southend, Oxford, Coventry etc etc should all have Class E airspace and appropriate VMC requirements.

The way that I see the current situation is that the CAA has reduced safety by not keeping the ICAO VMC requirement in Class D and at the same time placed an extra burden on the ATC units which causes extra workload and reduces IFR capacity a little but greatly reducing VFR capacity. This causes frustration to the average VFR pilot because they don't understand why in the UK thay are refused entry to airspace where they are not separated from anything else.

If we were to create a fuss or make a point, we would request avoidance of every VFR flight mentioned in UK class D because the reduced VMC minima makes visual avoidance more difficult that ICAO say it should be.

-----

Bookworm,

Yes, it could create extra workload for ATC because afer all they then have to separate the Special VFR flights from the IFR Arrivals/departures..........but isn't that the whole idea.....to separate aircraft who would be a collision risk in cases where visual avoidance is unlikely.

In the current situation, a controller can legally allow a VFR PA28 to join final approach just under the cloud base and 1nm ahead of a B737 on final and meet all the requirements by issuing traffic information to both aircraft. That may be legal but there isn't a sane person that will stand up and say that operating in accordance with UK procedures for VFR in class D is safe..............If it isn't safe then the CAA are required to take action before an accident happens.

OK requiring that same PA28 to be 1500m further away from the cloud or 1000ft below it probably won't make a perfect situation..........but it gives us a fighting chance to see and avoid....which after all is what we must do in class D.

A quick search will find a long thred about orbiting VFR flights downwind...........a case of ATC trying to separate aircraft where no separation is required. AOPA and GASCO are up on their high horses about the whole orbiting thing but have ignored or failed to spot the whole VMC issue.

----

When delaing with Special VFR, most UK pilots think that is operates purely on visibility basis - because that is what they learn at school. But they fail to understand that special VFR may be required because of proximity to cloud even if there is 50K visibility.

Regards,

DFC

PPRuNe Radar

26th Nov 2004, 22:25

Thanks DFC. Like most airspace issues, it's a bag of worms :}

2 sheds

28th Nov 2004, 09:21

Bookworm

You say:

"Yes, in the simplest case, it's clearly possible to fly SVFR if you're the only aircraft around. But if there are more than one, doesn't even "reduced separation" between SVFR flights place a rather heavier operational burden on ATC than simple VFR in the circuit?"

Quite correct - although I would phrase it as "more responsibility". However, an alternative is to place the responsibility for maintaining "own" separation on the pilot(s) - another form of "reduced separation int he vicinity...". That ploy will often reduce the circuit activity to an appropriate level!

DFC

30th Nov 2004, 17:48

Of course just to make it all even more confusing, the ability to accept a VFR clearance in Class D when flying just below the cloud is limited to UK pilots.

A visiting pilot who is only legally permitted to fly in VMC as per the ICAO rules could not accept such a VFR clearance unless they were 1000ft below the cloud.

So the argument about making it easier for VFR flights only applies to some of the flights......unless the airspace is restricted to UK pilots only!

It's like the UK pilots who have to be in sight of the surface at all times not being able to fly VFR on top in France despite the fact that French pilots with the same licence (JAA) can do so.

So perhaps the tower controller needs to not simply say "the visibility is XXX do you request IFR of Special VFR........but also to visiting aircraft......the ceiling is XXX do you request IFR or special VFR.

Makes for a very simple system indeed. :yuk:

Regards,

DFC

bookworm

30th Nov 2004, 18:56

Of course just to make it all even more confusing, the ability to accept a VFR clearance in Class D when flying just below the cloud is limited to UK pilots.

Now you're beginning to strain credulity DFC!

The Chicago Convention provides for aircraft to obey the Rules of the Air of the state whose airspace they are in, not the state of registration, nor the state of licence issue/validation of the crew (which will usually be the state of registration).

The rather screwy extraterritorial provision of the Rules of the Air Regulations need to be taken with a pinch of salt and a liberal dose of Art 84(3)(b). Its intention is to provide some framework for behaviour over the high seas.

safetyisourtoppriority

30th Nov 2004, 19:12

Just out of interest, to get back to the original points regarding avoiding unknown contacts in Class D control zones from surface upward - any slow moving primary only contact is almost definitely an aircraft (especially if no class G above).

Can anyone supply me with the old rules applying to Special rules zones etc that were in effect in late 80s before the new classifications came in - especially with regard to avoiding unknown contacts.

Final theoretical question - if you as an approach controller saw a slow-moving primary return in your class D control zone (no class G above), would you avoid it? I know the rules say you can, but would you? I'm thinking zone infringers etc.

DFC

2nd Dec 2004, 20:19

Bookworm,

Pilots are required to comply with the rules of the country over which they are flying or the rules of the country where the aircraft is registered whichever is the most restrictive

By following that requirement, a pilot ensures that none of the rules of any country are infringed at any time.

As I said, the perfect example is the UK pilot flying outside the UK.

The ICAO VMC criteria permit VFR flight above an overcast. The basic UK PPL is prevented from flying as such by UK law. Thus in that case even if the pilot is Flying in France, it is UK law that is the most restrictive and what limits the pilot.

Simply by not flying above an overcast, the pilot will comply with both French and UK law so there is no problem.

Going back to the Class D issue. If a French pilot for example refuses to accept a VFR clearance unless they can be 1000ft vertically from cloud in Class D then they are not breaking any UK law.....and also they are not breaking any French requirement.....or any ICAO requirement because OCAI clearly requires such a separation unless a special VFR clearance is obtained.

Thus they are limited by the most restrictive requirement which in this case is from outside the UK system.

Thus, the UK local operation of a sub ICAO airspace VMC requirement is only good for UK pilots and pilots of other countries that have the same VMC requirements..............Does anyone know of any other countries in Europe that have Class D VMC criteria below the ICAO requirements?

Regards,

DFC

spekesoftly

2nd Dec 2004, 23:58

Can anyone supply me with the old rules applying to Special rules zones etc that were in effect in late 80s before the new classifications came in - especially with regard to avoiding unknown contacts.

The 'old' rules for ATC action regarding Unknown Aircraft in UK Special Rules Zones were, as I recall, essentially the same as those now detailed in ATSIN No. 56. ("Neither Traffic Information nor Avoiding action shall be given unless ......." etc) - published in the MATS Part 1 and AIP of that time.

The confusion arose after the UK adopted ICAO Airspace classifications, in 1991? The rules subsequently published in MATS Part 1, regarding the avoidance of unknown aircraft in re-classified Class D Control Zones (old Rule 36 SRZs) were mistakenly changed, but remained the same, according to the UK AIP!

Some time after the Airspace changes, ATC Units were invited to submit comments on any problems or discrepancies to the CAA. (It was hoped that the 'new' airspace classifications would have little impact on procedures then current).

Yours truly, and others, did point out the discrepancy at the time.

Some 13 years later, somebody has finally taken note, and MATS Part 1 once again accords with the AIP!

NorthSouth

3rd Dec 2004, 09:47

SIOTP:in Class D control zones from surface upward - any slow moving primary only contact is almost definitely an aircraftReally? I can think of several Class D zones where your statement would be true only if you put a 'not' between 'definitely' and 'an'.if you as an approach controller saw a slow-moving primary return in your class D control zone (no class G above), would you avoid it? I know the rules say you canI presume you meant to say "ignore" rather than "avoid"? The rules don't say "you can avoid it"; they say "you will not give traffic info or avoiding action unless..."

spekesoftly:somebody has finally taken note, and MATS Part 1 once again accords with the AIPNot quite I'm afraid! The AIP text says:
"Traffic information and avoiding action will not be given unless information has been received which indicates that a radar echo may be a particular aircraft which is lost or experiencing radio failure."

The MATS Part 1 text now says:
"Neither avoiding action nor traffic information shall be passed unless radar derived or other information indicates that an aircraft is lost, has experienced a radio failure, or has made an unauthorised penetration of the airspace."

The eagle-eyed among you will spot that the AIP text (which I presume comes from ICAO Doc 4444 - don't have a copy here to consult) says nothing about unauthorised penetrations of the airspace, while MATS says nothing about "particular aircraft". If the AIP text is followed, then controllers could legitimately ignore a primary-only return which appears from nowhere and is not associated with the previous returns from an aircraft which they have been monitoring or which they have been told is an aircraft which is lost or had a radio failure. But the MATS text could, arguably, justify a controller treating any unidentified primary-only return appearing anywhere on the screen as something that requires the giving of traffic information and/or avoiding action.

I see the UK differences from ICAO Doc 4444 are currently under review. Presumably this is one of those differences - although it wasn't previously noted as one.

spekesoftly

3rd Dec 2004, 10:22

NorthSouth,

Glad to see you were paying attention! ;)

As you may also have noticed, the layout and format of the rules regarding 'ATC action with regard to Unknown Aircraft' differs between MATS Pt1 and the UK AIP, which makes comparison of the detail unnecessarily tedious.

Cheers.

bookworm

3rd Dec 2004, 12:37

Pilots are required to comply with the rules of the country over which they are flying or the rules of the country where the aircraft is registered whichever is the most restrictive

Not so.

Chicago Convention 1944
Article 12
Rules of the air

__________ Each contracting State undertakes to adopt measures to insure that every aircraft flying over or maneuvering within its territory and that every aircraft carrying its nationality mark, wherever such aircraft may be, shall comply with the rules and regulations relating to the flight and maneuver of aircraft there in force. Each contracting State undertakes to keep its own regulations in these respects uniform, to the greatest possible extent, with those established from time to time under this Convention. Over the high seas, the rules in force shall be those established under this Convention. Each contracting State undertakes to insure the prosecution of all persons violating the regulations applicable.

NorthSouth

3rd Dec 2004, 16:43

Liverpoolquietly:makes comparison of the detail unnecessarily tediousI agree it probably wasn't necessary for it to be so tedious but are you suggesting comparison isn't worthwhile? The difference between telling controllers they must vector traffic around every swan or rain shower that pops up out of nowhere, and telling them that they only need give traffic info when they see that light aircraft with the radio failure hang a left and go straight towards the CTR boundary, is huge.

NS

DFC

3rd Dec 2004, 21:29

Bookworm,

If every country had the exact same requirements then those requirements would be equally restrictive.

That is the whole idea...but then the UK comes along and dreams up it's own version which from a pillot's point of view reduces the safeguards built in by ICAO.

Isn't the teritorial limits of the ANO put somewhere in there....i.e. it applies to all flights over the UK and to UK aircraft where everthey may be? or something like that.

You can be sure that France has similar requirements in it's law.

As for the high seas! :}

Regards,

DFC

safetyisourtoppriority

3rd Dec 2004, 23:36

OK......but if the slow moving contact resembles the returns that you would, from your experience, consider may be a microlight or light aircraft, you would presumably avoid it - especially if your zone was regularly infringed by such aircraft?

The only way that you can deduce whether an unknown contact may be an aircraft that has infringed the zone is from your primary radar (unless it is squawking and then it is fairly obvious).

What about windfarms which often produce a series of primary returns that are identical to light aircraft? Would you take the chance that it is just the usual returns from a windfarm that you see all the time or would you consider the possibility that it is a light aircraft that has infringed the zone? Mats Pt 1 leaves that decision to you.

One day it will be a light aircraft!

Surely that is one reason for the requirement to have primary radar otherwise we would all be operating SSR only.

bookworm

4th Dec 2004, 08:48

Isn't the teritorial limits of the ANO put somewhere in there....i.e. it applies to all flights over the UK and to UK aircraft where everthey may be? or something like that.

Yes. The ANO has to have extraterritorial effect because the state of registration is, under the Chicago Convention, responsible for airworthiness and flight crew licensing of its aircraft wherever they may be.

The UK makes even its Rules of the Air extraterritorial, with an exemption:

84(3) It shall be lawful for the Rules of the Air to be departed from to the extent necessary:
(b) for complying with the law of any country other than the United Kingdom within which the aircraft then is;

On the face of it, it looks like it's exactly what you suggest: that the more restrictive rule might apply. But practically speaking, you have to interpret to the extent necessary quite liberally. It is never necessary to make (or continue) a flight, and thus one can always say that it is never necessary to break any rule from either state.

If I'm cruising on a NEly track outside controlled airspace in France, I'm supposed to be at odd thousand levels according to the UK Rules of the Air, odd + 500 according to the French Rules of the Air. A literal interpretation of 84(3) would simply be that I am unable to fly VFR on that track -- choose IFR instead. (Can't fly IFR? Tough!) In practice, you ignore the UK rule and adopt the local French practice. It would be quite impractical to do otherwise.

I think the same applies where VFR minima are varied. You could argue that a French pilot should reject a VFR clearance with a "not below 1500 ft" restriction into Birmingham class D with cloud at 2000 ft. Never mind that the guy before and the guy after did just that in a G-reg. The only practical option for the French pilot to avoid screwing up UK ATC with an apparently odd request is to ignore the French rule and adopt the local practice.

I believe that that is the way ICAO intends Rules of the Air to be applied. Annex 2 uses slightly but significantly different terminology, and requires that Rules of Air of a state apply to aircraft registered in that state to the extent that they do not conflict with the [local rules].

If every aircraft adopts local Rules of the Air, it provides for consistent behaviour and minimises risk.

(Sorry to have hijacked the thread for a legal debate.)

NorthSouth

4th Dec 2004, 14:38

siotp:What about windfarms which often produce a series of primary returns that are identical to light aircraft? Would you take the chance that it is just the usual returns from a windfarm that you see all the time or would you consider the possibility that it is a light aircraft that has infringed the zone?I guess that would depend on where the windfarm is in relation to your zone bdy and how good your primary cover is around it. If it's comfortably inside the zone and you know your radar's coverage is good in the areas between it and the boundary I'd guess you'd be more likely to disregard any pop-up primary return in the area of the windfarm that hadn't shown up previously.

There are similar problems with, for example, hang gliding, paragliding etc on LoAs inside Class D. You might get fleeting returns from these but how do you know that fleeting return is a hang glider operating under the terms of the LoA, or a zone infringer?

DFC

7th Dec 2004, 10:56

Bookworm,

"You could argue that a French pilot should reject a VFR clearance with a "not below 1500 ft" restriction into Birmingham class D with cloud at 2000 ft. Never mind that the guy before and the guy after did just that in a G-reg. The only practical option for the French pilot to avoid screwing up UK ATC with an apparently odd request is to ignore the French rule and adopt the local practice"

Are you saying that the same pilot faced with a wind out of personal limits should not anoy ATC by holding and requesting info on suitable alternate airfields but should try to land because after all the G reg pilot previously and the following G reg pilot both say there is no problem with the wind and they are flying the same aircraft type?

Are you also saying that certain flights are "screwing up UK ATC" by insisting on IFR clearances in Class D when there is CAVOK weather for 100nm?

As a pilot, I can make the decision that I will require a special VFR clearance every time the vis reported in the zone is less than 8Km..........that is higher than UK requirements however nobody can say that it is unsafe.

No pilot should let peer pressure including pressure from official sources cause them to operate in conditions which are below what is considdered safe.

Isn't your statement that a pilot sticking to international standards that are more restrictive than the UK would be "screwing up UK ATC" doing just that?

Regards,

DFC