Quadrantal Rule
 

Can u fly at the transition altitude. Ie fl30 when using quadrantal rule?

I was told no but think u can?

Also, why is the answer to this question FL50? And not FL30?

An aircraft is flying on a magnetic track of 075 degrees. The QNH is 1010. What is the lowest available flight level to fly in accordance with the quadrantsl rule?

thanks!

The transition altitude is an altitude (based on QNH) but the transition level is a Flight Level (based on 1013.25 mb).

Yes you can fly at the Transition Level whilst complying with the Quadrantal Rule. (Equally you can flt at the Transition Altitude but this would not be in accordance with the Quadrantal Rule because the latter is based on 1013.25 and magnetic track).

Assuming the Transition Altitude in this case is 3,000 ft amsl then the Transition Level would be FL 35. Since we are in the first quadrant an ODD flight level is appropriate so in this case Flight Level 50 would be appropriate.

Hope this helps!

The answer depends on the interpretation of "quadrantal rule". An aircraft may fly at FL30 on a magnetic track of 075 degrees with the QNH at any value without breaching Rule 34, known as the "Quadrantal rule and semi-circular rule".

The tranistion altitude is not always 3000ft although is most commonly used. So if we take 3000 ft as the tranistion altitude then FL30 is the lowest possible FL.

OK....FL are based on 1013mb.

A heading of 075 is an odd heading so levels that we can fly are FL30, FL50, FL70 etc.

Now lets take your QNH of 1010mb Thisis 3mb lower than the 1013mb. lets remember that 1mb=30ft (actualy 27ft to be accurate). So 3mb multiplied by 30ft = 90ft.

3000ft - 90ft = 2010ft Therefore FL30 is not available so you would need to fly the next available FL for you altitude whcih is FL50.

Does that help?

You can cruise at the transition altitude if you want. The quadrantal or semicircular rules only apply above the transition altitude.

The transition level in the UK is the first flight level above the transition altitude.

Note that while the transition level is above the transition altitude it is not separated from it i.e. the transition level may be 1ft above the transition altitude.

If the QNH is 1013.2 then the flight levels will co-incide with altitudes i.e. an aircraft cruising at FL30 will be 3000ft AMSL.

In this case since FL30 is not above the transition altitude then of course the transition level will be FL35 and you can see that by chance an aircraft at FL35 will be 500ft above an aircraft at 3000ft QNH.

As the pressure reduces below 1013.2, the flight levels move closer to the surface. Thus you can see that with reducing pressure FL35 will get closer to 3000 AMSL and eventually be under 3000ft AMSL.

Similarly, as pressure increases above 1013.2 the flight levels move up. Thus with a QNH of 1014, FL30 is actually 24ft above 3000ft AMSL and is therefore the transition level.

You can in this case cruise at FL30 in the appropriate direction however you need to be aware that while you will have 500ft separaton from the closest traffic above cruising at FL35, you will only have 24ft separation from traffic cruising at the transition altitude.

If the pressure increases enough, FL25 and then FL20 will eventually be above 3000ft AMSL and thus they will in turn become the transition level. Get your calculator out to work out when :)

Since the quadrantal rule applies to flight above 3000ft AMSL (or the transition altitude if higher), you can never fly at a flight level that causes you to be below the transition altitude.

Thus in the example given, FL50 is the first available level for that direction which is above the transition altitude.

Note that in other countries, the transition level may be the lowest flight level that provides a minimum of 1000ft separation from the transition altitude.

From a practical point of view you will not care much about the transition level, you will be more interested in a flight level that provides a minimum of 500ft separation from the transition altitude.

Regards,

DFC

The lowest usable flight level is the transition level of FL40.

How?

1013.2 - 1010 = 3.2 Mb

3.2 * 30 = 96ft

The position of FL30 is 96ft below (pressure is lower) 3000ft AMSL.

Therefore, FL35 is sitting at 3404ft AMSL and is thus 404ft above the transition altitude.

Thus FL35 is the transition level and is the lowest useable flight level.

However, remember that cruising at FL35 will only provide 404ft vertical separation from flights cruising at 3000ft QNH.

Regards,

DFC

The question was not on the lowest useable FL. It was for the lowest available FL for a heading of 075 with a QNH of 1010

FL35 is the lowest useable FL based on QNH 1010.

Yes.

That is why if you read my first post you will see;

The second post was a response to the one above it which is an erroneous statement.

Regards,

DFC

Say again :p

Oops

3000 - 90 = 2910

And that was a perfect example of how people kill themselves!!!

Don't forget of course that for VFR the quadrantal rule is only advisory, not compulsory.

DFC

All I was saying is that FL40 is the lowest cruising level. I'm well aware that it is not valid on 075(M). FL35 is NOT valid as a cruising level. 3000ft amsl is the point at which you reset the altimeter, i.e. transition altitude, but the transition level in the U.K. is FL40 with the gap in between being the transition layer. This exists purely to give separation based on variations between the QNH and the QNE. You normally reset the QNH when it is passed by ATC when IFR or passing FL40 if VFR and flying levels.

Oooops, time to get those books out again, I think! I'd suggest ENR 1.7 of the UK AIP as a starting point.

Islander2

I've had a quick look through the AIP but I can't see anything that contradicts what I said previously. If anyone knows better, or if I've missed something in the AIP, I will happily stand corrected but, to the best of my knowledge, FL40 is the nominal transition level in this country. Most plates say that transition level is as given by ATC but that is for IFR and is what I meant when I said you normally reset the QNH when it is passed to you.

Rubbish! The transition level varies depending on the QNH and the Transition Altitude!

As I've said before, there is a distinct possibility that I may be wrong about FL40. There was just something stuck in my head about that number.

What I am sure of is that the transition level is the lowest usable flight level and as such must be above the transition altitude, hence the transition layer. If you're IFR this is irrelevant as ATC will, in effect, tell you when to reset your altimeter by passing the QNH.

What you said in the above quote is 100% correct.

However, in the example - Transition Altitude 3000ft QNH 1010, the lowest usable flight level in the UK according to the Quadrantal rule is FL35 and the transition layer is 404ft thick.

If the QNH was 1045 Milibars then FL25 would find itself some 3460ft AMSL and thus would be the transition level in the UK and would give a transition layer of 460ft.

As was said previously, the transition level varies depending on both the transition altitude and the QNH.

Regards,

DFC

Quite so, DFC ...... except in those parts of the country where the transition altitude is 4,000ft .... or 5,000ft ..... or 6,000ft!

DFC, I know you understand that, but pilotincommand is in serious need of some more bookwork before he adopts his nom de plume in anger.

I can't find the book definitions on the net at the moment but perhaps we need to remind ourselves that:-

Transition altitude is the altitude (in the "vicinity" of an aerodrome) at or below which the vertical position of the a/c will be expressed (to ATC) in terms of an altitude based on QNH.

Transition level is the Flight Level at or above which the vertical position of an a/c will be expressed in terms of a Flight Level (based on 1013.25 mb)

The bit between the Transition Altitude and the Transition Level is the Transition Layer. When flying in the Transition Layer the vertical position of the aircraft is expressed in terms of a Flight Level when climbing or an Altitude when descending.

The way I teach the computation of the Transition Level is to imagine you climb (with QNH set) and level off at the Transition Altitude (although fixed for a particular aerodrome it does vary across the UK - eg 3,000 ft for aerodromes outside controlled airspace, 4000 ft at EMA/BHX.....etc as published). Whilst flying level you then set 1013.25 mb. If you wind on the pressure the altimeter indication will increase, if you wind off the pressure it will decrease (by approx 30 ft per mb). Lets say the altimeter now reads 3,400 - the TL will then be FL 35 (ie the next 500 ft level above your current "level"). Alternatively lets say the altimeter now reads 2,300 - the TL would then be FL 25.

I hope this helps.

Transition Level is defined by ICAO in PANS-ATM as:

Transition level. The lowest flight level available for use above the transition altitude.

Unfortunately "available for use" is subject to interpretation. Different states use different conventions. In the UK, if you're a VFR flight with a QNh of 1012, FL31 is "available for use". If you're an IFR flight, different levels are the lowest "available for use" depending on direction, though most (including MATS Pt 1) would interpret transition level as the lowest multiple of 5 i.e. FL35 in those circumstances. Other states make it the lowest multiple of 10 above the transition altitude, because only those levels are used for IFR, and still others make it lowest multiple of 10 at least 1000 ft above the transition altitude. Again according to ICAO, the transition level must be above the minimum IFR fight altitude for a control area.

As such, transition level doesn't have much use to pilots. The transition altitude is the phrase used in Rule 34, and neither is used in level selection rules in ICAO Annex 2.

And yet the ATIS at my home field (military) always quotes the transition level!

Saves me working it out, at least.

Tim

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OK - I understand that the transition altitude is 3000ft amsl - but if the transition altitude is 3000ft AMSL why is the transition level FL35 and the answer FL50? It needs explaining in basic terms! I'm probably just not seeing something I should be and haven't got access to my books at the moment!

Mind you that said you have to question how effective the Quadrantal rule is which I believe is only notified for the UK.

There was a theory that if you let aircraft fly around at random levels there would be less risk of collision! (Bear in mind that the Quadrantal Rule is for use outside controlled airspace).

Other States seem to manage quite well with the SemiCircular Rule!

Islander2

I completely understand that the actual depth of the layer will vary on the QNH. I simply had it in my head that there was an absolute minimum of FL40. It may be that this is a figure I have heard abroad.

Personally, I would question the wisdom switching to levels for cruising at 3000ft in a country where the spot heights extend to over 4400ft. If the pressure drops you could find yourself rather closer to the ground than you were expecting. It is much easier to reset the QNH periodically than constantly trying to calculate your actual altitude whenever there is a change in the QNH. It is fine if you're flying in places like East Anglia or the South East but I prefer to stay on the Regional QNH for VFR. Bear in mind that the higher levels are rarely an option around the higher ground in the U.K. if you want to remain VFR.

Just to add to that Bob, the way I teach is is to to tell the student to imagine we have parked the aircraft on a shelf at 3000 feet. we open the window lean through and observe 3000 feet on the altimeter, we than set 1013, now what is the altimeter reading without any aircraft climb or descent? From their pre-flight altimeter checks they should at this stage know, pressure up = altitude up and vicky versa. I find taking the CLIMB element out and parking the aircraft simplifies understanding

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Sam

Put the aircraft on the shelf at 3000ft with QNH 1010.

Now the aircraft is on a shelf it cannot climb or descend agreed.

Put you hand through the window and wind on 1013 (Pressure up = height/alt up).

Altimeter is now reading FLIGHT LEVEL(S) at approx FL3.1 so FL 30 IS NOT AVAILABLE--The next available FL is FL3.5 but on the mag track given in your question it would be FL50 (first quadrant = ODD)

So basically you are saying that you can never fly at FL30? Always FL35 and above?

In the case given no, but if the QNH was 1013 or HIGHER ,yes

or more simply you can fly at FL030 if the QNH is 1013 or higher( if trans alt is 3000 feet)


1. do you understand 'put the aircraft on the 3000ft shelf''?

2. do you understand--subscale up = alt up--subcale down = alt down?

as on pre flight instrument checks

AH I UNDERSTAND! Amazing.

God that was ridiculous. I'm just really tired.

THANKS Ilanfairpg!! Much appreciated.

Dont worry most pilots forget it and it still ties many up in knots. In practice for pilots its not thought about to much on a day to day basis but you need to apply 'exam logic' to it. So put your a/c on the shelf and twiddle that altimeter!

llanfairpg, that's a brilliant way of teaching it - thanks for sharing that with us!

Bookworm,

FL31 will never come into it because it is not a flight level used in the table of crusing levels.

The 500ft vertical separation between levels is universal. The only difference being that the UK has a "quadrantal" use for it while other places reserve the intermediate 500ft levels for VFR flights and the whole thousands for IFR flights.

In accordance with ICAO altimeter setting procedures which every PPL should have been taught as it is part of the JAR-FCL sylabus, the transition level is defined as the lowest flight level available for use above the transition altitude.

ICAO leaves two options for countries when choosing this level. Countries can require vertical separation between an aircraft at the transition level and the transition altitude and thus the transition layer will be a minimum of 1000ft. With this system you can indeed have a transition level of FL45 (i.e. an intermediate 500ft) however, in such a situation, ATC will often use a whole FL as the minimum crusing or holding level. Otherwise with the requirement to provide 1000ft vertical between IFR flights, the 500ft gets pushed up and up the stack and the posibility of an error.

The other option wjich the UK uses is to not provide any vertical separation between the TL and the TA and simply require the TL to be above the TA. The UK then uses minimum stack levels or minimum cruise levels to provide vertical separation when required.

Overall as I said previously, the TL is meaningless for most pilots. If you are climbing to a flight level then you set the altimeter to standard setting when cleared so that you do not forget and when cleared to descend to an altitude you set the QNH again so that you do not forget. The exceptions being when asked to report passsing an altitude in the climb or flight level in the descent.

Whoever has a problem with a 3000ft transition altitude when the higest obstacle is over 4000ft needs to remember the following;

1. There is a UK AIC with a Terrain Clearance table that you can print off.

2. You also have to factor in wind effects and temperature corrections as appropriate thus even using the QNH for minimum safe vertivcal separation from such an obstacle is not simply a case to making the altimeter set to an appropriate QNH read more than the altitude of the obstacle!

There is a graph in the UK AIP that you can enter with the QNH and altitude you want to fly at to find the minimum flight level that satisfies that requirement. You can use it to find the level that is 500ft above the transition altitude or to find the level that is 2000ft above your local Munroe.

I recomend that all IFR fliers in the UK have the terrain clearance table from the AIC avaiable in flight.

Regards,

DFC

DFC

A good post and I think you've summarised this debate perfectly. The only thing I would add is that when I mentioned the terrain issue, I was thinking of VFR and that going up 2000ft to the next FL for your track in a situation of falling pressure in order to maintain terrain clearance is frequently not possible.

Just a slip of the keyboard I'm sure, but the level to be flown in accordance with the quadrantal and semi-circular rules is determined by the magnetic track - not heading.

Yes that can be a problem not just for VFR flights but in the case of IFR flights operating in IMC, the position of the freezing level and icing layers can prevent flight 2000ft higher.

The UK only recomends that VFR flights follow the quadrantal and it is very good advice.

In other countries where VFR flights cruise according to the ICAO semicircular table of flight levels for VFR flights then one will often find that such a requrement only applies when more than a specified height above the terrain. 3000ft in some cases or in others "3000ft AMSL or 1000ft AGL whichever is the higher".

The ENR section of the appropriate AIP is the best place to start looking.

Regards,

DFC

Only if the guy coming the other way is like minded!

Never mind that. even the quadrantal system can have the guy attacking your left wing tip at the same level.......not to mention the faster aircraft behind!!!

Semicircular and Quadrantal rules do not provide any form of separation. They are simply the start in the creation of an orderly system rather than a safe system.

Regards,

DFC

You can listen to the ATIS at Baden (EDSB) on +49 72 29 66 23 32. The transition altitude from the AIP is 5000 ft. Here's the METAR.

METAR EDSB 162020Z 21008KT 8000 -RA SCT038 BKN044 08/04 Q1005=

The transition level is clearly stated on the ATIS as "FL70". If multiples of 500 ft were used, the transition level would be FL65, as this provides 1000 ft separation from 5000 ft.

I have never in 15 years of flying in Germany (or anywhere else I recall hearing the TL on ATIS) heard a transition level of anything other than a multiple of 1000 ft.

Since we're agreed that TL is essentially meaningless, it's of academic interest.

Bookworm,

In the case of Germany you are correct - For IFR flights the altitude at and below which the pilot shall set the altimeter to the QNH value transmitted by the competent ATC unit and above which he shall use the standard altimeter setting is established at 5000 ft MSL (transition altitude). For flights above the transition altitude, an altitude is established which, taking into account the valid QNH value, corresponds to the flight level for IFR, at least 1000 ft above the transition altitude (transition level).

Thus in Germany the transition level is always an IFR level. That is not the case everywhere.

Every country is different.

For example in Poland - the trasnition altitude is 6500ft AMSL and the transition Level is FL80 unless the QNH is 995 or less when it is FL90.

ENR 1.7 of the AIP for whatever country you want to fly in will let you know what the requirements are.

Regards,

DFC