What about this scenario.

BAW 123 clear to join overhead SAM climbing to maintain FL160.

Seems fine

I want to build a bit in so I say BAW123 cross SAM level FL100. I've changed a bit of the clearance but does that cancel the original clearance to FL160 ? Maybe .........

Then I feel bold and say BAW123 cross SAM FL130 or above. Have I cancelled the original clearance or just added a bit ?

Or in another case BAW123 route direct XXX. I have cancelled the original clearance, full route to destination ? No I have just changed an intermediate bit and the rest of the route after XXX remains as previously cleared.

My view is that take off to touchdown ATC is a series of interacting instructions not simple clearances. You comply with them all unless told to ignore or if you think they are incompatible i.e keep your speed up .... then expedite descent !!! :D We know that one is popular.

Someone could write a book of rules round this lot and still not capture all the possible scenarios. :confused:

Findo
Theres a difference between a clearance and a restriction.
A clearance is not changed by adding a restriction, so by telling a pilot to cross XYZ FL100 does not change his clearance to FL160.

Similarly a route clearance Flight planned route to destination is not altered by a DCT, all this does is puts the a/c on his FPR at a later stage whereby he will continue as per his route clearance.

I do agree though there is no rule book to cover all possible scenarios, which brings us back to the old mantra

If in doubt.........ask!!

fourthreethree where is that written ?

They did and it didn't.:D

Findo
First you implore the use of common sense and then you want to know where it is written that a clearance and a restriction are two different things, or that a DCT is not a new clearance limit. Make your mind up old chap:O

When you say that a clearance is not the same as a restriction, that all depends on what country you are in... A clearance and a restriction are one in the same in the US. We consider a restriction a clearance...

For findo, if we are going to add a restriction to an aircraft then we must add the rest of what we want the aircraft to fly. In your case is would be cross SAM at or above one three thousand, climb and maintain one six thousand, in our venacular. I am sure that with your own phraseology in the MATS part one it would be very much the same... It is unambiguous and the pilots would understand it. It would also ensure separation.

regards

Scott

Findo, if you clear me via SAM climbing to FL160 and subsequently tell me to cross SAM at FL100, I will take FL100 as my climb limit until I am recleared otherwise. If you tell me to cross SAM 'at or above FL130', having previously cleared me to FL160, I will assume that FL160 is still my climb limit. In your other scenarios, if you change a lateral clearance by re-routing me then I will obey any earlier altitude clearance unless you tell me otherwise.

In the descent clearances scenario, I will always assume that a 'decend FLXXX by...' clearance stands through controller changes unless I am told otherwise. Equally, if, after a controller change, I decide I can't make the restriction imposed by the earlier controller, I will tell the current ATCO of the problem. Sometimes circumstantial evidence (TCAS, other clearances) will suggest that the restriction may no longer be necessary, but I'll still check!