Sign in to follow this  
RickB1293

Reset transition altitude on transcontinental flight

Recommended Posts

When flying between the U.S. and Europe the transition altitude changes from 18,000 MSL in the US to 6,000 MSL in Europe. At what point in the flows is this supposed to be done? As far as the procedure goes, I set the TA from the CDU VNAV Climb page during the preflight when entering the flightplan. How do you make the change prior to the descent phase?

 

Is there a publication that lists the transition altitude for each region?

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

The FMC differentiates between TA for climb and descent. This allows you to enter different altitudes for the departure and destination airports. In each case you normally use the TA for the country of the airport, as it assumed that the transition will occur within the airspace of that country. Cruising usually occurs far above TA, so it isn't really relevant for this part of the flight.

Share this post


Link to post
Share on other sites

 

 


Is there a publication that lists the transition altitude for each region?

 

I always get the TA off of charts, usually easy to find by just using google with ICAO code, e.g., "YSSY charts."  Even within Eurocontrol, each country still seems to have it's own TA although references on line indicate they have a "task force" to study the situation.

Share this post


Link to post
Share on other sites

Hi, Rick,

 

Not sure if this is what you are asking, but the descent transition is entered in VNAV>Descent>Forecast page.  It asks for the Transition Level, which is the lowest altitude to which you will be cleared while still using standard altimeter, and usually varies w/ the barometric pressure.  I usually set it to 1000 ft above Transition Altitude (which is always fixed for the particular airport, AFAIK).  I never quite understood why it doesn't take Transition Altitude instead of Transition Level (as does the entry for the climb phase).

 

Mike

Share this post


Link to post
Share on other sites

 

 


I never quite understood why it doesn't take Transition Altitude instead of Transition Level (as does the entry for the climb phase)

 

Because you're referencing altitude until you climb above TA, and Flight level until you descend below TL.   

Share this post


Link to post
Share on other sites

Perfict diagram above explains it all.

 

Transition altitude is found on the Departures charts if they are fixed.

If the Transition Altitude varies (depends on barometric pressure) then it will be broadcasted on ATIS/by ATC.

1013/29.92 It is set when passing throught that specified altitude.

 

Transition Level is on Arrival charts if they are fixed.

If the Transition Level varies (depends on barometric pressure) then it will be broadcasted on ATIS. Like sometimes Vienna LOWW has TL60....other times (very low QNH TL70 is used).

TL can be set once cleared to descend to below the transition level (according our SOPs).

So flying at FL100 in Vienna with TL60....if you get cleared to descend to 4000ft then you dial in 4000ft, set the altimeter to local QNH and do the Approach checklist.

 

If for any reason you have to level of above the TL unexpectedly (reclearance/a problem/etc) for instance in FL80.....then you must not forget to put 1013/29.92 in your altimeter again!

Share this post


Link to post
Share on other sites

1013/29.92 It is set when passing throught that specified altitude.

I believe the 1013/29.92 is set when cleared by ATC to climb above the TA. Example KJFK TA is 18000. If cleared to FL230 when currently at 12000, 29.92 would be set then and not at 18000. Makes no sense to me but that is what I have been told by other Forum members.

Share this post


Link to post
Share on other sites

 


How do you make the change prior to the descent phase?

 

The VNAV descent forecast page allows you to preselect the transition level for the destination even prior to departure, if it's what you prefer.

 

 

 


Makes no sense to me but that is what I have been told by other Forum members.

 

This is correct.

 

The reasoning:

  1. As a pilot, it is of utmost importance to minimize future workload by acting upon items with immediacy where possible. After cleaning up post-departure, there isn't too high of a workload, but the practice should be consistent throughout all phases of flight: eliminate items as early as possible in order to mitigate the possibility of future task saturation. As there is little to no operational benefit to waiting, and future task saturation cannot be guaranteed, do it now.

    Alternate example: departure frequencies are often preselected prior to the takeoff roll to ensure that, once airborne, the frequency can be selected with minimal effort and distraction. I could certainly wait to do so, but the post-departure work load is much higher than the pre-departure workload. Do it now.
     
  2. As a pilot, it is of utmost importance to minimize future memory lapses by acting items with immediacy where possible. This one is pretty self-explanatory. As memory items age, their likelihood of being remembered decreases. Being cleared above/below the TA/TL (respectively) is a prompt for said memory item. A controller will not ("should not" might be better) clear a flight from one altitude to another without ensuring the path is clear. If there is a restriction, the controller will initially clear you to the restriction, and usually further as soon as the restriction has passed. It is usually very rare that a controller will do the opposite by issuing a more restrictive instruction after the initial instruction, such as "descend and maintain 15,000," and then issue a correction that is more restrictive, as "descend and maintain FL190." I say this to point out that you have a reasonable assumption that, once cleared above/below the TA/TL (respectively), you can set the altimeter setting of the destination area (in this case, the "destination" is referring to the area of standard or local pressure) without having to set it back due to an altitude reassignment.

    Alternate example: one rolls the altitude higher in the altitude window as soon as cleared, and not just prior to reaching that altitude. It may seem dissimilar, but it really isn't. The action is being executed immediately after being prompted, and not being withheld until the "restriction." Similar to the altimeter issue, the assumption here is that the controller usually does not restrict the climb regressively, so the cleared altitude is set immediately after being cleared. In other words, if I'm climbing through 6,000 for 12,000 and the controller clears me to FL220, I will set FL220 immediately after it's given. While there is a chance that the controller may come back and restrict the climb to some lower value, that risk is rather small, while the risk of forgetting to reset the altitude while approaching 12,000 is higher. This minor delay in continuing your climb could put your aircraft and other aircraft in conflict. Whose fault would that be? Sure, the controller might have cut the climb instruction a little close if a minor level off at 12,000 caused a conflict, but where is that letter likely going? To you. And if "in conflict" (this is the ATC term for setting off the conflict alert alarm when aircraft get too close on the scope) was so close that it resulted in a collision, there's such a concept as "dead right." Even if the controller climbed you in such a narrow window that a minor level off resulted in a conflict, and he or she was blamed, being dead right is usually not preferable.

Lastly, what is the reason for waiting?

  1. ...the assumption that there is some matter regarding the precision of setting standard precisely at the transition altitude, or local at transition level? There is zero operational benefit to doing this, and no achievements are unlocked in the process. Go shalt not be passed, and $200 shalt not be collected.
  2. ...the assumption that the climb or descent may be halted by the controller when still in the former setting's area? See above, item 2.

We fudge altimeter settings all over the place. When descending to an airfield, the arrival airfield pressure is usually what is passed to the pilot. For west arrivals to KIAD, the first relevant altimeter setting (where aircraft are below TL) is clear out towards KOKV. Would it not be easier to just provide that altimeter setting? No, in fact it would not be. While it is likely more correct for that area, it is easier for the controllers if everyone is working off of the same reference pressure (the whole reason we use standard for the flight levels). Offering the destination field altimeter allows controllers to have aircraft at common altitudes, while still allowing reasonably accurate altitude indications for terrain clearance.

Share this post


Link to post
Share on other sites

This is correct.

I am glad you got in on this topic since I have a question. Some SIDs at PANC, KLAS, KDEN have a final or maintain altitude higher than 18000 feet. If the SID clears you above the TA of 18000 feet why not just the STD altimeter prior to takeoff?

Share this post


Link to post
Share on other sites

I am glad you got in on this topic since I have a question. Some SIDs at PANC, KLAS, KDEN have a final or maintain altitude higher than 18000 feet. If the SID clears you above the TA of 18000 feet why not just the STD altimeter prior to takeoff?

 

SIDs and STARs are somewhat tough, and I had a feeling I was going to have to go partially against what I said earlier, because the SID/STAR procedures have specific FAA guidance. The FAA guidance is that, for profile SIDs and STARs (those with various altitudes published without "expect" next to them), the next higher altitude is selected until you get closer to that restriction, unless the altitude constraints are closely spaced (and then select the one on the far end of that segment). To that end, I'd change from local to standard as soon as I selected FL180 or above on the MCP. I can't find the FAA document on it at the moment, but if I do find it, I'll post it here. I only glanced at it quickly as I'm hanging out with the fam after my dad just got back from a few months in Malaysia. Saw the email that you'd responded, so I figured I'd write something up quickly, though.

 

With a profile SID/STAR, it's a different animal because you're the one prompting the MCP altitude changes, so you're essentially taking on the role of the controller providing the descent instructions.

Share this post


Link to post
Share on other sites

I believe the 1013/29.92 is set when cleared by ATC to climb above the TA. Example KJFK TA is 18000. If cleared to FL230 when currently at 12000, 29.92 would be set then and not at 18000. Makes no sense to me but that is what I have been told by other Forum members.

I just checked the Boeing SOPs that came with the PMDG777.

 

FCOMv1.PDF page NP21.40 and NP21.42.

 

They have you set TA and TL upon passing it.

Since I like consistancy I like that.

 

It all does not make much of a difference to select 1013/29.92 immediately once cleared to a FL (like FL230) or not untill actually passing the TA (18.000ft in USA).....as long as you dont have to level off again due to a revised clearance. Same for descent.

Share this post


Link to post
Share on other sites

I usually use ATC to prompt. 

 

If the clearance from ATC included the word "Flight Level" the QNH/Altimeter is set 1013/29.92.

 

If the ATC clearance includes the words "feet, QNH xxxx" then you set the QNH they just told you right after you start the climb/descent.

 

Obviously with the glass cockpit airliners you have the standby QNH setting, (and the yellow reminder on the PFD if you forget to change it from/to STD once a certain altitude above/below the pre-set transition altitude/level), so that's another nice piece of cheese covering a hole.

 

I always set the standby (white) QNH setting as soon as I get it (even before top of descent from the ATIS!) and then it's just a simple press of the STD button to switch to it when you get cleared below transition level, are nearing the transition level, at the transition level, or get the PFD altimeter showing up yellow if you forgot to.

 

Technically you should then set the Standby altimeter, and then cross check the altitudes are showing the same altitude within tolerance, Left, Right, Standby instrument.

 

You will notice that the PFD will NOT show yellow if you switch to the airport QNH well before the transition level as long as the MCP altitude is set below transition. (At least, that's the case on the 777).

Share this post


Link to post
Share on other sites

When flying between the U.S. and Europe the transition altitude changes from 18,000 MSL in the US to 6,000 MSL in Europe. At what point in the flows is this supposed to be done? As far as the procedure goes, I set the TA from the CDU VNAV Climb page during the preflight when entering the flightplan. How do you make the change prior to the descent phase?

 

Is there a publication that lists the transition altitude for each region?

Personally, at 100nm before the T/D, in preparation for the descent, among all the others things (calculations for vref, autobrakes, radio aids etc..) I set the Transition LEVEL in the DES/FORECAST page in the FMC, adding 1000 feet at the Transition ALTITUDE published on the destination airport charts. (e.g. approachin' LIMC, with a TA of 6000', i put 070 as TL).

Obviously, I wait the final call from the ATC about it, 'couse the TL could be even 1500' higher than the TA due to a change in barometric pressure.

Diego.

Share this post


Link to post
Share on other sites

Thanks for all the help. My procedures are okay I just couldn't remember how to set TL from the CDU - for some reason I completely blanked on the CDU VNAV/Descent/Forecast page item LK1.

  • Does setting TRANS LVL (CDU LK1) do anything besides trigger the PFD reminder?

 

I use EFB for selecting STARS and Approaches where it lists TA/TL in the upper right corner of the arrival and approach pages. For OMDB for instance, TA is 13000 ft and TL is FL150. 

  • Is TA for departure and TL for arrivals?
  • Does anyone know which RW chart actually shows TA/TL for the major airports such as EGLL, OMDB, WSSS, YSSY, my most popular hubs? 

 

Thanks Again,

Rick

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this