One of the ‘outputs’ of the Critical Review process is that current design weaknesses or flaws in the current operation may be ‘added’ to list of design objectives or used to refine the design objectives. In the example used above, the possibility of designing a discrete SID for use during the summer months by heavy aircraft has arisen and as such, it may be appropriate opportune to add this to the design objectives.
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Although the Reference (or ‘Psuedo’ Reference) Scenario serves, at a later stage, as the yard-stick against which the success of the new or modified design is measured, it may be considered logically inconsistent to seek comparisons between the Reference Scenario and new Scenarios based upon different assumptions or enablers (or constraints). The diagram below presents this apparent dilemma.
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SCENARIO 1
Airspace Configuration Assumptions/Enablers: Performance**
(as per Qualiitative and Quantitative Analysis, see Part D)
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RNAV SIDs/STARs P-RNAV
Capacity per sector per hour = 27
(open)
ILS to RWY xx CAT I
IAPs as per Runway Capacity (Normal Operations) = 44Terminal Area Radar
Reference
.....
FDP/RDP fully integrated
Single Runway Operation
.....
Runway Capacity (LVP) = 22
No level busts on new NE SID
Poor ILS capture from SW ?
AIRSPACE ASSUMPTIONS (RESULTANT)
SCENARIO 1 CONFIGURATION ENABLERS PERFORMANCE
CONSTRAINTS
. ...
Holds as per
Reference
Constraints:
Structures (n/a)
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Min. Alt. Fl100 over city;
Geographic Sectors
COMPARABLE AIRSPACE ASSUMPTIONS (RESULTANT)
CONFIGURATION ENABLERS PERFORMANCE

B REFERENCE
CONSTRAINTS
SCENARIO
REFERENCE SCENARIO
REFERENCE AIRSPACEA SCENARIO
ASSUMPTIONS (RESULTANT)ENABLERS PERFORMANCE
Airspace Configuration Assumptions/Enablers: Performance
CONFIGURATION
(as per Critical Review* and Quantitative Analysis)
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Conventional
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Conventional Navigation
CONSTRAINTS
.....
Capacity per sector per hour = 22
Runway Capacity (Normal Operations) = 42
Runway Capacity (LVP) = 22
Frequent level busts on NE SID
Too many missed approaches when RWY YY in
SIDs/STARs
ILS to RWY xx CAT I
Terminal Area Radar
FDP/RDP fully integrated
Single Runway Operation
....
IAPs
Holds
Structures
Functional Sectors
Constraints:
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Min. Alt. Fl100 over city;
Figure 2- 2: Scenario Comparison
In the above diagram -
A= the Reference Scenario with its particular Assumptions, Enablers and Constraints and its resultant Performance.
C= the new Scenario 1, with, for example, a new set of SIDs/STARs based on a different assumptions (e.g. Navigation means = P-RNAV) and its resultant Performance.
In comparing the Performance of Terminal Airspace C (Scenario 1) with that produced by A (Reference Scenario), it could be argued that A and C are not comparable because the assumptions are different (e.g. navigation) and that the changes made to the SIDs and STARs are therefore substantial. Furthermore, a different sectorisation method has been used. Logically, this argument is correct, and if followed through one would need A to be based on C’s assumptions to obtain performance B and that B should then be compared to C so that the comparison is meaningful.
　
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