LHR Director - Descent to 7000 ft?

[flying finn]

Hi - over the last week (with both high and low QNHs) we've received occasional descent clearances to 7000ft from Director. Is this a new procedure or something, as I'm pretty sure I've not heard of it before during the past five years?

I may have this completely the wrong way round, but e.g. today with a QNH of 995mb, and a published trans alt of 6000ft, the lowest available FL should be FL80. Following a descent to 7000ft you've only got ca. 500 ft clearance from FL80 (although I suppose you're 1000ft above the outbounds, which might help in some scenarios)....

Just to satisfy my curiosity, under what circumstances do you folks descend people to 7000ft once they've left the holds?

[Scuzi]

I can't speak for Heathrow but in the TMA we occasionally do the exact same thing. There are a multitude of reasons for doing so but the main one is to prevent the aircraft from leveling off at FL80 whilst still keeping it separated from the outbounds at 6000ft. For example, the pressure is 1012mb and you might only have 1 mile horizontal separation form an outbound at 6000ft so you can't descend through it but the inbound aircraft is approaching FL80 and you want to give it continuous descent. Simple, use 7000ft! The aircraft continues descending almost another 1000ft and by the time it approaches 7000, you have horizontal separation with the outbound and can descend further.

It just keeps things moving.

[Defruiter]

As Scuzi has said - Avoids you levelling off at 80 when you could get further descent shortly. Usually done if there is an outbound under you at 6A and we need to get you going down for a CDA. Sometimes also happens when you're on the trombone from LAM - If we turn you round the corner downwind and we're turning you within spitting distance of another inbound who is just out of 6A, dropping you to 7A gets you going down. (You should then be cleared further before levelling off). It isn't seperated from 80, so obviously isn't used if you're near anything at 80.

It can be used in lots of different situations, but those are the main 2 I have used it for (the few times I have).

Hope this helps.

[flying finn]

Thanks very much for the info - solves that riddle then. As I said, hadn't seen it before this week (only ever been descended to 6000ft, with 4000ft being the norm) hence the question. Much appreciated

[Days of Future Past]

Incidentally, the practice was banned by SRG circa 8 years ago after a couple of incidents. Let's be careful out there.

DoFP

[Naked Ape]

I have no recollection of this being 'banned', but I can see how it would be undesirable as the difference between FL80 and 7000' alt could only be a couple of hundred feet with a low QNH. I prefer to use the 'non-existent' FL70 as an intermediary level providing of course that the preceding is out of FL70 and is descending to 5000' or lower.

[Jumbo Driver]

Originally Posted by Days of Future Past

Incidentally, the practice was banned by SRG circa 8 years ago after a couple of incidents. Let's be careful out there.

Perhaps someone can shed light on the SRG opinion/ruling, to which DoFP refers ...?

Personally, I cannot see how the use of intermediate Levels or Altitudes within the Transition Layer can be good practice. In my opinion, it should be discouraged, if not actually banned, as there is clear scope for ambiguity, confusion and misunderstanding.


JD

[anotherthing]

ATCOs are trained and paid to seperate aircraft. If they include the use of FL70 when the min stack is FL80, or 7000' against something at 6000' then so what?

As long as the ATCO understands what he/she is doing, there is nothing wrong with the practice.

Any ATCO that is unable to work out the relationship between the levels on any given day, should not IMHO, be valid.

Altimetry is not hard, and we are talking about a very basic understanding to know what is going on in the above circumstances.

[TopBunk]

Wouldn't it just be easier if we adopted the US system with the transition altitude of 18000ft?

[Scuzi]

Originally Posted by anotherthing

ATCOs are trained and paid to seperate aircraft. If they include the use of FL70 when the min stack is FL80, or 7000' against something at 6000' then so what?

As long as the ATCO understands what he/she is doing, there is nothing wrong with the practice.

Any ATCO that is unable to work out the relationship between the levels on any given day, should not IMHO, be valid.

Altimetry is not hard, and we are talking about a very basic understanding to know what is going on in the above circumstances.

I agree entirely. If an ATCO chooses to implement this technique and fully understands what he/she is doing then what is the problem? Is it the old fogies afraid of doing anything which requires thinking outside of the box?

And what's this about SRG banning the practice? First I heard of it. I used this particular technique on my validation board and there wasn't a peep about it.

There's a lot of traffic nowadays, especially in the LTMA and efficient use of the airspace is necessary to keep the tin flowing. Getting bogged down and caught in a rut with routine and rigid techniques is not necessarily the best path to take, especially when it is taken as far as wanting to ban perfectly safe practice.

[Cartman's Twin]

Agree with the majority. I've used this technique on a few occasions to help keep things moving both in the climb and descent.

I certainly wouldn't condone it's use as 'the norm' but imho it's a perfectly safe and valid tool to have at your disposal.

[Jumbo Driver]

Originally Posted by Cartman's Twin

I certainly wouldn't condone it's use as 'the norm' but imho it's a perfectly safe and valid tool to have at your disposal.

An interesting comment, CT - I am intrigued as to why you wouldn't condone it as "the norm" but at the same time defend it as "perfectly safe".

Surely, if it is "perfectly safe" it could/should be adopted as "the norm"?

It seems you have some reservations about the practice, which you are not voicing ... ?


JD

[Lookatthesky]

It's perfectly safe if you understand its use.

For instance, if the pressure is low and you decide to use FL70 against an inbound at Fl80 that's perfectly safe providing you don't then stick an a/c at 6000ft underneath the one at FL70!!

Separating a/c is what we're paid to do at the end of the day it's all about flexibility. As Scuzi has said, it keeps things moving

[Jumbo Driver]

Originally Posted by anotherthing

As long as the ATCO understands what he/she is doing, there is nothing wrong with the practice.

I can't agree - actions need to to be clearly understood by all involved, and not just by one individual at his end of the speaking tube.

Originally Posted by Scuzi

If an ATCO chooses to implement this technique and fully understands what he/she is doing then what is the problem? Is it the old fogies afraid of doing anything which requires thinking outside of the box?

The same answer applies. Also, convention is not about stuffiness or being an old fogie - it is about both sides of the professional relationship understanding what each other is doing. If one side is unclear what the other side is up to, then several holes in your swiss cheese are already lined up.

Originally Posted by Lookatthesky

For instance, if the pressure is low and you decide to use FL70 against an inbound at Fl80 that's perfectly safe providing you don't then stick an a/c at 6000ft underneath the one at FL70!!

So why not climb your outbound to 6000', which is still safe - but much more conventional - then everyone (including pilots and your less "adventurous" ATCO colleagues) will be clear about what is happening?


Overall, I really can't see that much is to be gained by this technique, other than (on average) about 500' of intermediate climb or descent, and then only for a very short while. Against this, I believe there is a genuine danger of causing confusion by issuing a clearance unconventionally to an altitude/level which is within the Transition Layer.

Safety must be foremost ...


JD

[PPRuNe Radar]

It shouldn't require the pilot to work anything out or have to think too much about things. If cleared to a Flight Level, you do so on the standard pressure setting. If cleared to an altitude, you do so on the QNH given. Nice and simple.

The vertical position of your aircraft in relation to the Transition Layer, Transition Level, or whatever, is nice to know but since you are letting ATC provide the vertical separation, then trust them to provide you with a safe clearance based on the datum of their choice.

If you take the non standard 'danger' thing too far, where do you stop ?? Should we ban opposite direction levels, for example in the Upper Airspace and out on Oceanic tracks, thereby reducing capacity by a large amount ?? Or do we let professionals on both sides of the mike have trust in the overall system providing a safe and conflict free flight path, as we always have ?