Flying at the Transition Level

[76mike]

During our arrival into Frankfurt-Hahn airport (EDFH), the ATIS announced "Transition Level is six zero."

ATC cleared us to descend and maintain "Six thousand feet." Was this an error on their part?

We were subsequently given a lower altitude, and didn't have a chance to ask the controller.

I was prepared to enter the local altimeter setting in our altimeter, since he said "6000 feet." My F/O did not agree, and wanted to keep 1013.

Thanks in advance. Mike

[MarkerInbound]

Hahn is "TL by ATC." Normally they give you the altitude in feet followed by "on QNH xxxx. That is my cue.

[Glamdring]

I'm assuming that the Transition Altitude is 6000'. In this case there is no problem in using that level. Aircraft above will be dropped to the first separated FL above the Transition Level, in this case FL70. As you were given a descent to an "Altitude" you should've set the local QNH. Bit of an ambiguous call by ATC though, they should have said "Descend to Altitude 6000 feet"

[NotMeMate]

Both Glam and Marker are correct. :ok:
First altitude involving a change from a FL should be
"Descend to ALTITUDE xxxxfeet, QNH xxxx"
Belt and braces to change.
Reedback would also include both. :O

[throw a dyce]

I have seen a few loses of separation with people using 6000 ft altitude and FL70 when the pressure is low.I preferred 5000ft altitude and FL70 or FL80 if the pressure was very low.I don't believe saying altitude is a requirement in Doc4444.

[Spitoon]

Was it an error? All depends on the pressure....and whether both 6000ft and FL60 existed. I've never been any good at these altimetry questions - I'm sure you know if it's high or low pressure that will give you the right conditions for both FL60 and 6A to exist.

There's a second issue that varies between States of whether the Transition Layer is a minimum of 1000ft 'thick'. Some States have procedures that ensure any altitude allocated below the Transition Level will be separated from any FL that is allocated above - others do not.

I think the 'must say altitude' thing, although good practise, is a bit of a UK thing.

[Tom!]

@Glam, Transition altitude is 5000ft in Hahn. If QNH is 1013 or higher TL is FL60, if QNH is below 1013 TL is FL70.

I've had a few times Langen say explicitly "maintain altitude 6000ft I say again altitude 6000 due traffic descending above" on the departure or the other way around with maintaining a FL.

[Glamdring]

In that case I wouldn't expect Altitude 6000 feet to be used as a matter of course. I can see situations where it might be used tactically though.

I've used Flight Levels myself below the TA when I can't be bothered doing the altimetry maths :ok: (Obviously terrain safe FLs I might add ;) )

[vaschandi]

Transition altitude is 5000ft in Hahn. If QNH is 1013 or higher TL is FL60, if QNH is below 1013 TL is FL70


This is applicable for hall german airspace. You will not find an altitude
of 6000 ft on any ARR, DEP or APP chart. The TRANSITION layer is minimum 1000 ft.
Generally altitute 6000 ft is not flown in Germany. So I would say if Hahn ATC cleared you to that altitude without further explanation, it was simply a mistake.

[zoneman]

Bit of an ambiguous call by ATC though, they should have said "Descend to Altitude 6000 feet"

I don't think so...4444 do not say so either.
"6000 ft" is just enough of information. Pilot should obey ATC's instructions in such case, confirmation is an option though. The reason for clearing to altitude instead of TL is unknown, but I wouldn't say it's a legal option.

[ILS 119.5]

Transition level is the first available Flight Level above the TA. So if it is 6000' the TL could be FL65, 70, 75 etc depending on the QNH. However tho does not mean that an a/c cannot fly at 6000', 7000', 8000' etc. I' sure most of you guys understand altimetry but separation using QNH altitudes and Flight Levels is not difficult. As long as it's 1000' or greater. I've used altitudes well above the TA just to get the a/c in.

[Spitoon]

Transition level is the first available Flight Level above the TA.As I said before, the question sometimes is what available means. Is it the first FL that exists above the TA or it it the first one that is at least 1000ft above the TA??

Different countries apply different 'rules'. From Tom! and vaschandi's posts it seems that Germany use the latter interpretation. When I controlled in the UK years ago there was no 'rule' and even different units did it differently - one place I worked I would be in line for a real rollocking if I didn't keep 1000ft between alts and flight levels and at another all I had to do was keep the aeroplanes apart vertically by 1000ft. Like ILS, I occasionally used altitudes above the TA (along with a quick explanation to the crew) if it helped to sort out the traffic.

There's a third option that I have seen where TA is, say 10A and TL is FL120 and no-one needs to worry about about working out what FL can be used unless the pressure is unusually extreme. Personally, I don't much like that system because most of the time you unnecessarily lose at least one level and because people don't usually have to worry about what the pressure is, they can easily not remember to do so when it is necessary.

[hvogt]

Mike,

I think you were right and your F/O was wrong. As you say, ATC cleared you to an altitude of 6000 feet. I did my instrument flight training in northern Germany and we were regularly cleared to altitudes, even when above the transition altitude. I hope I can help by quoting the relevant rules below.

If the level of an aircraft is reported in relation to the standard atmospheric pressure 1013.2 hPa, the words FLIGHT LEVEL shall precede the level value. If the level of the aircraft is reported in relation to QNH / QFE, the level value shall be followed by the word FEET. (AIP Germany, GEN 3.4-11)

IFR flights shall be conducted in compliance with semi-circular cruising levels (Attachment 3), unless in climb or descent, at the flight level or altitude corresponding to the magnetic track. The [...] air navigation service provider may grant exemptions in individual cases [...]. (Section 37, Paragraph 3 of the German Aviation Regulation, published in AIP Germany, ENR 1.1-24. Italics added.)

[ILS 119.5]

If the TA is 5000' then the first available level is FL55 but could be FL60, but dependent on pressure. It would be unlikely for an atco to use 55 because after that it will be 65, 75, etc. and then to get back to normal levels you would have to use 90, 100 etc, so somewhere you will lose 500'. So std operating would be TA 5000' QNH 1000 hpa or below lowest FL70, QNH above 1000 hpa, lowest FL60. Technically if all a/c are on the same pressure setting either QFE, QNH, 1013, then separation would be easier unfortunately we have to use different pressure settings due aerodrome elevation (QFE, for GA and RAF), terrain and obstacle clearance (QNH) and FL for everyone who is safe from terrain. So wherever you are there are calculations to be done. (normally by the computer)

76mike, what was the qnh at the time. If the atco said 6000' i would question it, as the first descent to an altitude you must be given the qnh, its in the book. Also where were you at the time the descent was given, as I remember all the departure SID's go to FL60, and if you were on the transition downwind abeam the field FL70 is adequate for a 3 deg glide path descent profile (continuous, or as near as)

[zoneman]

ILS119.5 , wouln'd you put 1012hPa instead of 1000hPa in:
"So std operating would be TA 5000' QNH 1000 hpa or below lowest FL70, QNH above 1000 hpa, lowest FL60."
We just need to gain 1000ft above TA for separation purposes, and it is 1000ft when QNH is 1013. If it drops below we need to use higher FL, if it's above 1013 we get some extra ft.
Mixed use of alt and FL could be treated as a serious safety issue...with all respect to UK guys.

[FantomZorbin]

IIRC I was taught to never fly at either the TL or TA as the separation between the two was never more than 500' ... but that was well before we went hectopascalling.

[2control]

TA is set by the CAA in the country and it´s fixed, e.g. 5.0ft.
TL fluctuates with the air pressure and temperature. In some countries there is a built in separation between TA and TL and in other countries it's not.
In the US there is another solution. 18.0ft is TA and F200 is TL just to make it easier. By doing the US solution you lose a level.

In countries where there is no built-in separation the controllers have to think by themselves where there is separation. To make it simple and safe you regard the TA and the TL as the same level for separation purposes e.g. TA 5.0ft and TL55. That means that 5.0ft is the same as level F55. Then you descend the arriving aircraft to F70. You could descend to F65 but you select a level that ends with a 0, just to make it more simple.

I hope this makes it perfectly clear to all and everyone.

[HEATHROW DIRECTOR]

Doesn't make much sense to me 2control....

"TA is set by the CAA in the country and it´s fixed, e.g. 5.0ft."

I think you mean "e.g. 5000 ft". "5.0ft" is just five feet.

And FantomZorbin.... hectopascals are precisely the same as millibars so have no bearing on the current discussion.

[Spitoon]

2control...wow! How could I have gone through life for so long without understanding such a simple thing the way that you do?

And having the the gift to explain it so simply.

Oh, hang on a minute, um....so, let me get this right.....TA and the TL as the same level for separation purposes.....

I must have done it wrong every working day for 20+ years!

[ILS 119.5]

I can't remember but doesn't 50 indicate fl50 and 5.0 or A5.0 indicate 5000' altitude on the strips. To be truthful I not bothered if flying on qnh at an altitude above the ta providing I'm 1000' vertically separated from any other a/c, or 3/5 miles laterally and I don't mean three fifths.
Technically you could fly at a FL below the TA and still be above the MSA within the MRVA, I know this is never done but theoretically it could be.
H.D. You are correct in what you state by saying that the TA is set by the CAA for that country and "fixed", but only fixed for a certain area of the country and can vary from area to area. Whereas the USA and Canada it is fixed for all of the states at the same value of 18000'.
Confusing things more:-
UK TMA Controller:- "USA XXX descend altitude 5000' QNH 1015"
"Err London, USA XXX can we have that in inches"
"Affirm USA XXX descend altitude 60000 inches QNH 1015" :)

[rad_app_twr]

Hi Mike (probably bored by all these different answers ? ;))
OK, then you get here one more!! hahaha

First of all we can deduce from this thread that altimeter setting is not an easy topic ;)
Even APProach controllers, who are the ones supposed to deal with it continously, and I can tell u as I am one of them, and have discussed it a few times.

Reading all the previous answers (Spitoon is not very kind with 2control who says it quite properly, maybe because of the 20 years doing wrong??, probably not, but you declared first " I've never been any good at these altimetry questions ")
and trying to put all this together:

1) The main and very important point for ATC is to SEPARATE (if only vertically) a/c with at least 1.000ft

2) The Transition Altitude (for each aerodrome), 5.000ft in EDFH, never changes, so it is quite clear you con fly at 5.000ft QNHXXXX any time, around that airport.

3) The Transition Level (also for this aerodrome area) is used precisely for the same reason as in (1), so as to allow 1.000ft separation,
at least, between TA and TL (the zone in between is the famous Transition Layer, let's say dangerous for vertical separation purposes).

=> The way to calculate the TL is depending on the local pressure, of course. So, as we suppose the ATIS was correct saying TL60, that meant the QNH at that time was above 1013,2 which is the reference.

MY CONCLUSION: the ATCO at that time did wrong, as he shouldn't be clearing you to an altitude in the middle of the Transition Level.

Why not? Because in that case he has to start thinking if you are at that point separated from lower aircraft and higher aircraft (that is the concern, in that case).
What happens many times? You don't stay long at that WRONG LEVEL and as you said they cleared you to a lower altitude, 5.000ft or below, which is not a problem anymore.

The best way to do it? Use the TA as the maximum altitude, ant TL as the minimum Flight Level. That's what they are for, to avoid thinking.

TL=60 means you should have been cleared to FL60 which is separated from altitudes 5.000ft/QNH or below (and of course from FL70 and above).
As a pilot you should have asked for confirmation, as it was a confusing clearance.

More opinions are welcome. You know, two ATC's, at least three opinions :rolleyes:

[Spitoon]

Reading all the previous answers (Spitoon is not very kind with 2control who says it quite properly, maybe because of the 20 years doing wrong??, probably not, but you declared first " I've never been any good at these altimetry questions ") and trying to put all this together:Yup, I admit it - I can never remember what happens to the Transition Layer when the pressure goes up or down. I need to sit down with a pencil and paper to work it out from first principles......which I assure you I can do.

BUT at every approach unit that I worked at there was some sort of system that clearly showed what levels were 'separated' from the TA by at least 1000ft. So I didn't need to resort to the pencil; and paper. The last place I worked approach there was a nice simple display - right next to the met report - which showed not just the first flight level (ending in a 0 or 5) that existed above the TA and also the first flight level (again ending in a 0 or 5) that was at least 1000ft above the TA....so I didn't need to think about anything!

[2 sheds]

There seem to be so many red herrings being introduced! (I hope that translates!).

ICAO Definition:
Transition altitude. The altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes.

Therefore, if the transition altitude at Hahn is still 5000ft, the convention should be that altitudes are only assigned at or below that level. Otherwise, it can create confusion amongst aircrew - which it obviously did.

2 s

[2control]

You have received a lot of answers to your question. But, you haven't replied to anyone of them. Could it be that you still haven't received a simple and clear explanation?
I'll try again:
If TA is set to 5000ft then nobody should use an altitude above 5000ft. My only guess why you were given 6000ft is that the controller had another aircraft at 5000ft and wanted you to use the same altimeter setting to have a safe separation between to two of you.
Your headline was: flying at the Transition Level. You could fly at that level if the country you fly in has a built-in separation between TA and TL.
As soon as you get a clearance to descend below the TL you should always use the current QNH.

As a rule of thumb: the lower the QNH is the higher the TL is and the higher the QNH is the lower the TL is.
So, for example: QNH around 1050hPa, TA 5000ft, then TL is F040. Which means that you could climb a departure to 5000ft, descend an arrival to F050 and still have 1000ft separation!
No wonder pilots and controllers are discussing altimeter settings now and then...