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[GRP] Understanding the difference between BLOCKS and LIMITS of stand definitions


Jonas Kuster (1158939)
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Jonas Kuster (1158939)

While looking into a detailed integration of the GRP, I came across some questions regarding the use and functionality of the commands BLOCKS and LIMITS for a stand definition. I'm looking therefore for some additional advise about best practice and experience of other users.

I've done various tests, but wasn't satisfied with the result (or didn't understand the exact meaning of the beforementioned commands).

The basic issue is that I have a combination of narrow body and wide body gates, as it is quite common at many airports. Some of the gates can be used for both types. And I wish to implement a logic that such a gate is restricted in its maximum wingspan if the neighbouring gate is used for a wide body aircraft. So think of the 3 gates W01, W02 and W03 (for wide bodies) share the width with a configuration of 5 narrow body gates N01 ... N05. W02 and N03 will be exactly in the middle and share the same lead-in line (and effectively use the same gate number). Once there is an assignment for either N02 or N04, N03 (=W02) can only be used for a narrow body aircraft. How do I need to prepare the configuration in such a case?

I've difficulties to understand what the exact difference between BLOCKS and LIMITS in this case will be.

Also, I cannot fully understand from the documentation how the LIMITS command exactly works. Could someone make an example using the terms from the developer guide?

Jonas Kuster Leader Operation - vACC Switzerland | www.vacc.ch

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Ricardo Sousa (1110850)

limits is used in maps, so that if that map is active, the limit becomes active. For example if you have a notam that restricts the critical aircraft temporarily you can setup a map with the notam dates in the active line.

Blocks is just if this stand is taken, these other stands aren't usable.

 

This sounds similar to what you are trying to achieve:

STAND:LPPT:411:N038.46.03.510:W009.08.12.720:15
CODE:C
BLOCKS:412
USE:AC
PRIORITY:0
CALLSIGN:RZO,TAP,TAX,MVA

STAND:LPPT:412:N038.46.04.290:W009.08.12.210:15
CODE:D:F
BLOCKS:411,413
USE:AC
PRIORITY:0
CALLSIGN:RZO,TAP,TAX,MVA

STAND:LPPT:413:N038.46.04.840:W009.08.13.080:15
CODE:C
BLOCKS:412
USE:AC
PRIORITY:0
CALLSIGN:RZO,TAP,TAX,MVA

image.png.87b44741de0d91b4995e1ddcc182cf38.png

Basically the narrow body stands take up to Code C aircraft, the wide one takes up to code F, but only from D onward. So you won't have an A320 on the wide one. The narrow stands block the wide and vice versa too.

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Jonas Kuster (1158939)

@Ricardo Sousa Not exactly. "Our stand 412" will also be used by narrow body aircraft, so it is not solely used for wide body aircraft.

From the documentation, I see that commands BLOCKS and LIMITS are available in both the Maps but also the Stands definitions, although with a slightly different syntax. So there IS a meaning in both setting files for them. I just can't yet understand how I need to use them to achive my goal.

Jonas Kuster Leader Operation - vACC Switzerland | www.vacc.ch

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Juha Holopainen

BLOCKS is basically just a special case of LIMITS - you can think of blocking being the same as limiting the target stand to zero wingspan and length (although it's not exactly the same in the code - BLOCKS skips the wingspan/length checks completely so it's much more efficient to use it when you want the target stand to be unavailable for any aircraft, and use LIMITS when you want the target stand to be available for some size aircraft). In the current release there is a bug in the LIMITS code - the "Length" and "LimitedLength" parameters must to be specified to make the restriction work properly (just set both to 999).

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Jonas Kuster (1158939)

Thanks @Juha Holopainen! I think the input regarding the bug explains part of the problem. But I've still an issue, and I'm not sure if I understand the documentation correctly, so I would appreciate your advice.

image.png.90a98892d777dcdd520c81f74763f4de.png

A04 is a code C gate and currently assigned to an A321. A48 can be used up to code E, but shall be limited to code C if A04 is used. I've therefore inserted the following line as part of the gate A04 definition: LIMITS:A48:C:C:999:999.

So in this case A48 should only be available for up to code C. However, when using the dropdown to assign a stand to an A332, A48 is still shown as a possible option. I would expect A48 to be indicated as not available for an A332 in this case. Is there another bug or did I mess up with the definitions?

 

 

STAND:LSZH:A04
CODE:C
USE:A
ENGINETYPE:J
PRIORITY:2
SCHENGEN
LIMITS:A48:C:C:999:999
BLOCKS:A46
COORD:47.453625:8.55828611111111
COORD:47.4530305555556:8.55819722222222
COORD:47.4530611111111:8.55775833333333
COORD:47.4536555555556:8.55784722222222

STAND:LSZH:A48:47.45337222222220:8.55753333333333:20.5
CODE:E
USE:A
ENGINETYPE:J
NOTATYP:A345,A346,A35*,B74*,B773,B77W,B78X
PRIORITY:-3
SCHENGEN
BLOCKS:A08,A04:C

 

Jonas Kuster Leader Operation - vACC Switzerland | www.vacc.ch

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Jonas Kuster (1158939)

@Ricardo Sousa You are not reading the details. Of course all the stands are available in the list. But some of them are shown in a different color, indicating that they are either already assigned or blocked. As Juha explained that BLOCKS is to be understood as a special case of LIMITS, I wonder why stands, which according their limitation are no longer available for a specific aircraft type, are not marked accordingly. The drop-down list suggests that they can be assigned for specific type, when they actually cannot due to the limitations defined.

Jonas Kuster Leader Operation - vACC Switzerland | www.vacc.ch

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Ricardo Sousa (1110850)

I'm not sure what you're talking about, is it this?

image.png.fc8d9094e14cf84da03a60800ff9cd01.png

This only shows which stands are already occupied or assigned, it doesn't take any limitations in account

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Juha Holopainen
On 12/12/2021 at 23:18, Jonas Kuster said:

A04 is a code C gate and currently assigned to an A321. A48 can be used up to code E, but shall be limited to code C if A04 is used. I've therefore inserted the following line as part of the gate A04 definition: LIMITS:A48:C:C:999:999.

So in this case A48 should only be available for up to code C. However, when using the dropdown to assign a stand to an A332, A48 is still shown as a possible option. I would expect A48 to be indicated as not available for an A332 in this case. Is there another bug or did I mess up with the definitions?

The manual stand assignment menu is intended to be a way to manually force a specific assignment regardless of any possible restrictions set in the data file. For that reason it only shows occupied, blocked and assigned stands in grey color, signifying that those stands are currently unavailable for any aircraft regardless of physical size, routing, etc.

Your LIMITS definition is also a bit wrong. That definition would limit A48 to code C only when an aircraft larger than code C is at A04 - which being a code C stand should never happen. The line should be "LIMITS:A48:0.1:C:999:999" - this would limit A48 to code C when an aircraft with wingspan greater than 0.1 meters is at or assigned to A04.

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Jonas Kuster (1158939)

Thanks for your reply, Juha. I think finally we are getting down to the bottom of this. And it might be a fundamental misunderstanding of the documentation regarding the concept of LIMITS. I have difficulties to correctly identify subject and object since ever, and don't really know which of the WingspanOrCode/LimitedWOC terms is referring to the stand the standlist, and which is referring to the "current" stand this limitation is added to.

May I suggest therefore some clarification on the documentation?

Causes the stand to limit the maximum aircraft dimensions of other standsStandList, if the current stand is assigned to or occupied by an aircraft that exceeds the WingspanOrCode value or, if used, the Length value. The stands from StandList will be limited in this case to aircraft with maximum dimensions according values LimitedWOC and, if used, LimitedLength. If only a limitation by length is desired, set -1 for WingspanOrCode and LimitedWOC. The wingspan values can be set also based on the aerodrome reference code letter.

Can you confirm this does also correctly describe the behaviour of LIMITS?

 

May I also propose for a future version of GRP to mark limited stands in grey as well? As you explained earlier that LIMITS is a special type of BLOCKS, I would also expect the same impact to the stand drop down list. Because in fact, for a specific "too large" aircraft exceeding LIMITS definitions, the stands in question are also unavailable. I think it would make sense to consider the physical characteristics in this case. Thanks for considering.

 

Jonas Kuster Leader Operation - vACC Switzerland | www.vacc.ch

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Juha Holopainen

LIMITS:StandList:WingspanOrCode:LimitedWOC:Length:LimitedLength

is interpreted in the code as follows:

When the stand in whose definition the line is is occupied by or assigned to an aircraft whose wingspan is greater than "WingspanOrCode" or whose length is greater than "Length", the maximum allowed wingspan and length of all stands listed in "StandList" are limited to "LimitedWOC" and "LimitedLength".

When a stand is subject to active limitations from more than one other stand, the most limiting values are used (for example if stand 1 is limited to max wingspan 40m by someone at stand 2 and to 36m by someone else at stand 3, the resulting limitation to stand 1 will be 36m).

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