Thames Radar

[Dimensional]

This Saturday (7th September) I ws hoping to take a C152 through the City CTR between Lea Valley reserviors and Crystal Palace (truth be told, I'll have "she who must be obeyed" on board, and as it's her first flight in anything light and single-enginedlike I thought that a quick hop across London would be good, through the western side of said Class D).

And so, two questions:

a) Is this even going to be feasable or will I be turned away before hitting the airspace? Will the choice of R/W10 or 28 affect the decision? I'm happy with the R/T, although admittedly in 6 months of having the PPL this will be my first controlled airspace crossing outside of the R/T practical :)

b) Is there anything I can do to make both mine and your lives easier? I know I have to file a flight plan but would you prefer a filed one or an abbreviated one on the R/T? Ideally I'd like as high as possible, ie.: above 2000'... is this going to be possible or will I have to be at 1500', bearing in mind the "glide clear" rule this should be just about OK but I'd be happier at 2000' or so.

Any thoughts?

-D

[ATCO Two]

Hi Dimensional,

I will be working Thames Radar on Saturday morming. The only complication is that there is a calibration of the 28 ILS on Saturday. I suggest you plan your flight for early afternoon when City Airport is closed for the best chance of a zone clearance.

Runway 10 in use is marginally easier for transits. Coming from the South you might be held outside the zone North of Crystal Palace or alternatively at the Southern tip of the Isle of Dogs. Coming from the North you might be held at the "Southernmost Lake in the Lea Valley" so get hold of a map and be prepared for these eventualities. You do not have to file a flight plan - we just need basic details of your flight (which I am sure you have covered during your RTF training). It helps if you carry a transponder. If you are told to standby and the frequency sounds quiet, wait until we get back to you and do not enter the zone without a clearance. There is an awful lot of telephone co-ordination on Thames which will be transparent to pilots. I try to give a "not above" VFR clearance which is usually 2000 ft, but will vary between 1500 ft and 2400 ft depending on traffic. Be sure to comply with the controller's instructions which may be to pass East/West/Overhead City Airport, and watch out for the plethora of other traffic - pleasure flying helicopters, police helicopters, Helimed, Capital Radio, Classic Wings Rapide, the pesky "Dome Watchers" etc. etc.

I hope this answers your questions - if not e-mail me.

[evenflow]

Blimey. Do you still wanna do it, dimensional?

[bookworm]

I don't see how you can 'glide clear' in a C152 from anything less than about FL80 on that route. And in case there's any doubt, that's entirely your problem, Dimensional, not ATCO Two's.

I even worry about the 1500 ft rule in a twin. Under VFR, requiring 1500 ft above the highest object within 600 m means that transit of London at less than about 1900 ft is somewhat dubious.

ATCO Two, how easy is it for Thames to grant SVFR in perfect weather for the purpose of avoiding that problem? Seems daft to require ATC separation to avoid the low flying rules but...

[ATCO Two]

Hi Bookworm,

As you know, a SVFR clearance is only available in a Class D Zone in IMC or at night, and ATC are required to provide standard separation of 1000ft vertically or 3nm horizontally between SVFR flights, IFR flights, and SVFR and IFR flights. It is difficult enough to mix VFR and IFR in the City Zone on a fine day, with airspace constraints, base of the LTMA at 2400ft, the Specified Area, heliroute H4 etc., without having to apply standard separation between SVFR and IFR. This requirement would effectively close the Zone to non IFR movements, unless City Airport was closed or very quiet, so I am afraid that your suggestion, although solving the Rule 5 problem, would cause more problems than it would solve. And changing the type of clearance would have no impact on what would happen in the event of failure of a power unit anyway! With singles as you know, the transit route is via the Lea Valley which takes aircraft clear of the Specified Area (built up area of Central London for those not in the know). Although not ideal, there are some lesser populated areas at which a pilot might land if he lost a donk - Wanstead Flats, Hackney Marshes and even City Airport in an emergency - but don't use the PAPIs! Unfortunately there is no satisfactory solution to the problem which is caused purely by the geographical situation of the City Zone.

[Dimensional]

Hey all.

My use of the words "glide clear" may have confused matters -- what I was referring to was being able to glide to the nearest suitable field -- as ATCO Two said, while these aren't exactly plentiful they are there.

(I know it's all my problem, but that doesn't stop me asking for help, does it?)

I've got the plane booked for the afternoon (about three pm) anyways, so that's good news. The traffic thing, well, that can't be helped. What you've been saying is pretty much common sense (don't wander into Controlled Airspace without a clearance :) -- although people do do it, I suppose!) I know the area pretty well so the reservoirs are familiar to me, as well as most of that part of the world north of the Thames.

Anything else? :):confused:

-D

[bookworm]

Thanks for the prompt and full response, ATCO Two.

As you know, a SVFR clearance is only available in a Class D Zone in IMC or at night, and ATC are required to provide standard separation of 1000ft vertically or 3nm horizontally between SVFR flights, IFR flights, and SVFR and IFR flights.

I didn't know that. Is that from MATS Pt1? Being devious, if there's a little low cloud around it's not hard to accelerate past 140 KIAS and enter IMC :)

but of course that doesn't mitigate your difficulties in accommodating it.

And changing the type of clearance would have no impact on what would happen in the event of failure of a power unit anyway!

Quite. So it's daft that it changes the low flying rules too!

With singles as you know, the transit route is via the Lea Valley which takes aircraft clear of the Specified Area (built up area of Central London for those not in the know).

Well the Specified Area only relates to helicopters and doesn't, by a long stretch, constitute the limits of the "congested areas" of London, which a fixed wing has to glide clear of after a power plant failure.

even City Airport in an emergency - but don't use the PAPIs!

I would have thought they'd be pretty close to a light aircraft glide angle. Aren't they 6 degrees?

[ATCO Two]

Hi Bookworm,

VFR/SVFR criteria are available in the AIP and also in MATS Part 1 1-5 to 1-7. Yes, technically speaking if you fly at greater than 140kts you are required to be 1500m horizontally and 1000ft vertically clear of cloud in Class D to remain VMC, but the visibility criteria remains 5km. When the visibility drops to 5km or less at City Airport, we ask pilots whether they require SVFR or VFR clearances.

Since the Specified Area was established many years ago (at least 30), the congested area of Central London has expanded considerably with no change to the dimensions of the Specifed Area. I agree according to the ANO that it applies nominally to single engined helicopters, but the CAA Legal Branch seem to see things slightly differently, taking a view that there is no way a fixed wing single flying SVFR at 1500ft over Central London could alight clear in the event of failure of a power unit. Folklore has it that one day a "legal eagle" happened to spot such an aircraft from the window of Aviation House, took tracing action and prosecuted the pilot! Although I am unable to refuse a SVFR clearance over the specified area to a fixed wing single, I would STRONGLY discourage a pilot from requesting such a clearance as it puts myself and my colleagues in a very difficult position. It is a grey area indeed and one probably best avoided.

The PAPIs at City Airport are set at 5.5 degrees. What I meant to infer is that pilots will not get the glidepath information they are used to if they rely on the City PAPIs.

[bookworm]

Since the Specified Area was established many years ago (at least 30), the congested area of Central London has expanded considerably with no change to the dimensions of the Specifed Area. I agree according to the ANO that it applies nominally to single engined helicopters, but the CAA Legal Branch seem to see things slightly differently, taking a view that there is no way a fixed wing single flying SVFR at 1500ft over Central London could alight clear in the event of failure of a power unit. Folklore has it that one day a "legal eagle" happened to spot such an aircraft from the window of Aviation House, took tracing action and prosecuted the pilot!

In case I'm misunderstood, let me just clarify. I think the area which a fixed wing single must be able to glide clear of is substantially greater than the Specified Area, i.e. that the rules are much stricter for fixed wing than helicopters.

Rule 5 says in general that:
helicopters shall not fly below such height as would enable it to alight without danger to persons or property on the surface, in the event of failure of a power unit;

but:
an aircraft other than a helicopter shall not fly over any congested area of a city, town or settlement below_such height as would enable the aircraft to alight clear of the area and without danger to persons or property on the surface, in the event of failure of a power unit

So generally, while a helicopter flying over a congested area only has to be able to find somewhere in the congested area to put down safely, a fixed wing aircraft must be able to clear the congested area entirely.

(The exception for the helicopter is the Specified Area of London, which it must be able to alight clear of in its entirety.)

Since a congested area "in relation to a city, town or settlement, means any area which is substantially used for residential, industrial, commercial or recreational purposes" it seems unlikely that there is a much wider area of the city (including, but not limited to, the Specified Area) over which a fixed wing at 1500 ft is not going to be able to glide to a site completely clear of the "congested area".

[alphaalpha]

Hi Dimensional:

I see you are a new PPL and your girlfriend has not flown in a light single before.

You are proposing to fly in a high-stress environment -- your first controlled airspace crossing and a particularly difficult one. I think most SEP pilots would not consider your Crystal Palace-Lea Valley route even if they knew every possible forced landing place like the back of their hand. Your workload will be high, navigating from field to field, and ATCO2's restrictions may compromise your ability to land clear.

For your girlfriend's first flight, why don't you chose a quiet route where you will have spare brain-power to explain to her what's going on, reassure her as neccessary, and make the flight a gentle, fun experience that she will want to repeat

Sorry if I sound a bit of a kill-joy, but I would really think again.

[ATCO Two]

Bookworm, agree with you entirely on all counts. The 1500 ft part of Rule 5 should be the overriding consideration. The complication is that the Specified Area overlaps both the London Control Zone where the the 1500ft Rule doesn't apply (to aircraft on SVFR clearances), and the London City Control Zone where the Rule does apply to aircraft on VFR clearances. Having said that, fixed wing and helicopter twins are instructed to fly AT 1500ft SVFR in the sector 020 degrees to 140 degrees true from Heathrow Airport (somewhat wider than the Specifed Area). This I suppose gives them a "fighting chance" of alighting clear in the event of power failure. If twin helicopters are unable to maintain 1500ft they are unable to route direct and must use the heliroutes. Single helicopters are catered for by the network of helicopter routes which end up following the River Thames when they reach the Specifed Area.

[2 sheds]

ATCO 2

Don't you mean "less than 5 km"?

[Dimensional]

Alpha Alpha...

You're quite right, it is a high stress environment, but it's one I feel I would be able to handle (I'm worried about sounding like an overconfident accident-statistic-waiting-for-a-place-to-happen but I can't help it :) ). I have carried passengers before, and as it happens the passenger in question (:D) does know a lot about aeroplanes (so I'm not worried about her being on board at all) ...

I understand the problems about the gliding clear rule, and appreciate the relative lack of fields should anything untoward occur... however it is something I've wanted to do for as long as I can remember, and something I think I could handle -- navigating from suitable landing field to suitable landing field would however be a significant task as you say....

The route in question would've involved quite a bit of flying before the CTR crossing -- which I was going to use to do all the usual patter, finishing the flight with a quick hop over london to do some sighteeing. I've been over the route from south to north (Biggin Hill -> Elstree) as pax before now...

Or am I being a total muppet? :D

-D

[ATCO Two]

Hi 2 Sheds,

Well yes, and no! 5km visibility is the minumum for VFR flight in Class D, therefore in less than 5km we would be issuing SVFR clearances. In deteriorating visibility I would expect to be asking pilots what sort of clearance they required when the visibility was indicating 5km, in order that we were using the right form of separation criteria when the visibility actually dropped below 5km. It takes a fair bit of pre-planning when changing from traffic information only to full blown standard separation in a restricted piece of airspace.

[alphaalpha]

Hi again Dimensional:

I do understand your need to expand your experience. Everybody has been there; some PPLs stop pushing themselves and never fly beyond their airfield's locality (or even stop flying), others expand their flying horizons steadily and safely. Clearly, you want to be the latter.

So a three part suggestion:

1. From the legality point of view, consider what Atco Two and Bookworm have said about landing clear; check the ANO (or Trevor Thom or Jeremy Pratt or whatever book you used for Air Law). You can maybe ignore their 'private discsussion' about SVFR separation & helicopters, since you will only want to fly your 152 in good weather.

2. Consider the airmanship aspects of your plan.

3. If you are happy about both the above, talk through the plan with the CFI of the club hiring you the a/c on the day. He can help you weigh up all aspects, including your own experience, aptitude, weather of the day, a/c servicability, traffic density etc.

4. Think now about an alternative plan in case you decide 'no' based on 1, 2, or 3. If a key objective is to gain experience if a class D transit, consider Luton who have a VFR lane through their CTR which routes through the overhead.

Have fun, safely

[Hooligan Bill]

ATCO Two

VFR/SVFR criteria are available in the AIP and also in MATS Part 1 1-5 to 1-7. Yes, technically speaking if you fly at greater than 140kts you are required to be 1500m horizontally and 1000ft vertically clear of cloud in Class D to remain VMC, but the visibility criteria remains 5km. When the visibility drops to 5km or less at City Airport, we ask pilots whether they require SVFR or VFR clearances.

This scenario actually cropped up on a LCE board I once had. Visibility is 15km, cloud sct 1400, why would somebody request a SVFR clearance and would you grant it?

The answer is you would grant it subject to traffic and the reason is because of the position of the sct 1400, the pilot would not be able to comply with the visual flight rules and the 1500ft rule.:rolleyes:

[ATCO Two]

Hi HB,

Nice one! Sounds like the sort of devious question I used to ask as a rating examiner at Bailbrook and CATC.