Transition Altitude

[Superpilot]

Could someone define 'Transition Altitude'. What is it? It's purpose etc etc.

Thankos Muchos

[Piltdown Man]

There has to be a point where you have to change over from referencing your altitude to the height above sea level at the point of your departure to a standard setting. This is the Transition Altitude. In the UK, it varies between 3,000 and 6,000 feet but it's precise level for where you are is published. However, there are various exceptions and rules associated with this.

[Rainboe]

You know, if you Google it, you will be bowled over by responses, and that is without even researching Pprune Search!
Quite simply and in a nutshell, it is a way of ensuring everyone in the cruise is flying to the same altimeter setting. Once above safety altitude, it is more important to not bump into other people coming the other way than know exactly how high you are above terrain.

Now this will take at least 25 responses totally dissecting the above. I'm giving it to you simple- the web has all the answers you need.

[Sven Sixtoo]

It's the altitude above which flights under IFR must be conducted with reference to Flight Levels (ie with 1013 / 29.92 set on your altimeter).

So, passing TA in the climb, you set 1013mb on the altimeter subscale and apply quadrantal rules etc to the resulting indication on the altimeter.

On the way down, the corresponding figure is the Transition Level, which is the first available Flight Level above the TA.

The purpose is to ensure that everybody in the same chunk of airspace is using the same datum for height.

In the UK, outside controlled airspace, TA is 3000 ft. TL varies with the atmospheric pressure of the day.

TA in a Control Zone or Control Area is usually higher. Frequently altitude rather than Flight Level is used up to the top of the Control Zone / Area, so that people aren't changing altimeter settings halfway down the descent to land.

Overseas, where they have bigger hills, TA is often higher - Altitude is an indication of terrain clearance, whereas Flight Level may not be, so you want to be using altitude whenever you are operating within a sensible margin (1000, 2000 or 4000 ft depending on how big the mountains are) of the highest ground.

A quick scan of the geography of the UK will show that the 3000 ft TA does not comply with this requirement. There is, I believe, ongoing consideration of raising TA to 6000 ft in UK airspace.

As a helo pilot I rarely get above TA (nosebleed country!), so feel free to correct if you know better!

Sven

[Engineer]

Definition of Transition Altitude can be found here (http://en.wikipedia.org/wiki/Transition_Altitude)

[RYR-738-JOCKEY]

Okidoki, where to start...? Sven I just have to say in advance, it is much easier to pick on somebody elses work so don't take it personal...
;)

It's the altitude above which flights under IFR must be conducted with reference to Flight Levels (ie with 1013 / 29.92 set on your altimeter).
VFR flights included.



So, passing TA in the climb, you set 1013mb on the altimeter subscale and apply quadrantal rules etc to the resulting indication on the altimeter.
Never heard of...However you should select a cruising level/alt based on 0-180 degrees or 180-360 and VFR or IFR...mainly for planning purposes.

On the way down, the corresponding figure is the Transition Level, which is the first available Flight Level above the TA Wrong. TL is the first available flight level and at least 1000 feet above the TA.

Altitude is an indication of terrain clearance, whereas Flight Level may not be, so you want to be using altitude whenever you are operating within a sensible margin (1000, 2000 or 4000 ft depending on how big the mountains are) of the highest ground. Firstly, altitude is by no means an indication of terrain clearance. It is closer to be the opposite of this. I.e. you will HIT terrain if you think that it IS your terrain clearance. When you set local QNH, the indication will be feet above mean sea level. And then you mention different margins. 1000 is minimum terrain claerance for IFR flights with terrain upto 6000', 2000 applies to terrain above 6000'. And finally 4000' doesn't apply to anything.

so feel free to correct if you know better
I just had to.
By the way, THANK GOD IT'S FRIDAY.:}

Engineer: Just chrecked out the link. I like Wikipedia, but we have to remember it is written by you and me.
It says: It is the highest altitude at which an aircraft in normal operation should use an altimeter pressure setting indicating height above mean sea level QNH.
This is wrong. What about when you descend through FL200 , and you get cleared to an altitude. Then you set QNH. Indicating 20000 feet.:8

[bookworm]

Okidoki, where to start...? Sven I just have to say in advance, it is much easier to pick on somebody elses work so don't take it personal...

Isn't it just?! Note that Superpilot comes from the UK.

VFR flights included.

Not in the UK. VFR flights are free to choose their level on any altimeter setting.

However you should select a cruising level/alt based on 0-180 degrees or 180-360 and VFR or IFR...mainly for planning purposes.


Not in the UK. Quadrantal levels are compulsory for IFR flights, advised for VFR flights, above the TA.

Wrong. TL is the first available flight level and at least 1000 feet above the TA.

Not in the UK. There's considerable international difference over whether the TL is the first FL above the TA or the first one that provides standard separation from the TA. In the UK, it is the former.

[Engineer]

RYR-738-JOCKEY

Depends on company policy when you set the QNH. Setting the QNH approx 2000' above the TA is reasonable because the chances of ATC altering your clearance level to a FL are slim. But if in Europe you set the QNH at 20000' and an intermediate FL is assigned you would have to reset the Altimeter baro :( However in the USA 20000' is OK:ok:

[RYR-738-JOCKEY]

Well, I asked for it, didn't I?

But I have some more:

VFR flights are free to choose their level on any altimeter setting.

Exsqueese me? This cannot be. How can a controller provide separation between traffic which are not on the same reference.
If an aircraft on VFR enters a TMA above the TA, he shall report FL, so that the controller can keep him clear of other traffic above TA.
Or how about a Piper Malibu cruising at FL180 through congested airspace, don't think he will be flying long if he reports altitude.


Wrong. TL is the first available flight level and at least 1000 feet above the TA.
--------------------------------------------------------------------------------

Not in the UK. There's considerable international difference over whether the TL is the first FL above the TA or the first one that provides standard separation from the TA. In the UK, it is the former.

I really doubt the first part, but the last proves my point..because the standard separation between VFR/IFR or IFR/IFR is...
Correct, 1000'. So an aircraft below the TA will always be at least 1000' below any traffic above TL. :}

Keep it coming, I have all night:E

Engineer: This has nothing to do with company policy. If you look it up in the JAR-OPS you\'ll find that whenever you pass the TL or you\'re CLEARED to an altitude you set QNH. So it\'s basically up to the controller. He will not do this if there\'s a lot of traffic, but in Scandinavia you will get those from time to time.

[Engineer]

R7J

For future reference the relevant Subpart of JAROPS 1 pertaining to setting QNH is?

Thanks in advance :ok:

[Chilli Monster]

RYR-738
Exsqueese me? This cannot be. How can a controller provide separation between traffic which are not on the same reference.

Depends on the airspace. There is no requirement to fly flight levels if VFR in class 'G', 'F' or 'E'. Class 'D' airways it would be a good idea above transition altitude, though again there is no requirement to separate VFR v IFR unles the IFR requests it.

I would say what you have said is only fully valid in class 'C' or 'B', where VFR and IFR traffic must be separated from each other.

So - in a way both you and Bookworm are correct - but for different classes of airspace ;)

[bookworm]

Exsqueese me? This cannot be. How can a controller provide separation between traffic which are not on the same reference.

You're simply taking it out of context. Controlled flights, VFR or IFR, obviously fly at whatever level ATC assigns. Uncontrolled VFR flights (in classes E to G) are free to choose their level on any altimeter setting. Uncontrolled IFR flights must select a quadrantal Flight Level.

I really doubt the first part

MATS Pt 1 (http://www.caa.co.uk/docs/33/CAP493PART1.PDF) Appendix A is available for your perusal.

[RYR-738-JOCKEY]

Engineer wrote:
For future reference the relevant Subpart of JAROPS 1 pertaining to setting QNH is?

:ouch:

I was just checking if you were paying attention:)

Bookworm wrote:
You're simply taking it out of context. Controlled flights, VFR or IFR, obviously fly at whatever level ATC assigns. Uncontrolled VFR flights (in classes E to G) are free to choose their level on any altimeter setting

Out of context??? The uncontrolled flights you mention are the ones who squeese in just on top of a CTR or TIZ, where there is no TMA/TIA, no other traffic and nobody to talk to on ground.
Whenever you report your Alt/FL, you must adhere to the acknowlegded procedures regarding TA/TL. :p

[Chilli Monster]

R738J

Out of context??? The uncontrolled flights you mention are the ones who squeese in just on top of a CTR or TIZ, where there is no TMA/TIA, no other traffic and nobody to talk to on ground.

And so, by definition, are not concerned about how they report their levels as they're not in a form of airspace that requires that - that airspace being unregulated and therefore their only concern being that they stay outside regulated airspace.

Whenever you report your Alt/FL, you must adhere to the acknowlegded procedures regarding TA/TL.

May I suggest a better understanding of ALL airspace classifications, not just C - A, and the requirements of such will stop you getting hot under the collar in this thread. As someone who's name suggests they fly an aircraft that possibly operates to airports outside CAS then that may be a good place to start ;)

[Engineer]

I was just checking if you were paying attention Well good to see that I am right and you are wrong :E Now where is my fishing rod and pilot bait :)

[DFC]

Chilli,

there is no requirement to separate VFR v IFR unles the IFR requests it

Class D does not ever provide for separation for an IFR flight from a VFR flight even if the pilot requests it. What it does say is that "Traffic Avoidance" will be provided on request after traffic information. Traffic avoidance is not the same as separation.

Could not have the crusty BA Captain turning up in some French TMA and stating that he required separation from all VFR flights now could we? :)

While the UK has a flexible attitude to altimeter setting in class G and in doing so reduces the safety margins, most other countries are not so flexible.

For example, airspace base levels are normally set to a VFR cruising level. Why? - ensures that IFR traffic inside will be 1000ft above IFR traffic cruising outside. Some countries ATCs set the minimum level to be assigned IFR inside controlled airspace at 1000ft above the base when the base is defined as an altitude or 500ft above base level when defined as a flight level - All about the requirement for all flights to cruise at appropriate level and thus in both cases the flight inside will be 1000ft above a flight at the correct cruising level outside. Does not allow for the guy climbing up to the base for a quick 3 turn spin though ;)

The overall point is that if one operates to French or Dutch or Irish or any other European countries' altimeter setting procedures - one will be legal in the UK VFR. Do it the other way round and one will be illegal.

When IFR the UK quadrantial in class F and G is the only difference.

Regards,

DFC

[Chilli Monster]

What it does say is that "Traffic Avoidance" will be provided on request after traffic information. Traffic avoidance is not the same as separation.

Separating is the opposite of putting together. If you give traffic avoidance you must, by definition, be separating because you're not putting the two closer together ;)