# Presentation: 697079

## Multi-Fix GDP Status

- February 7, 2002
- Metron Aviation, Inc.

## Objective of Multi-fix GDP

- Current FSM GDP algorithms model arrival flow as a single queue
- Can only control flights into the airport as a whole
- Many times bad weather (or other constraints) reduce capacity only in certain directions
- Multi-fix GDPs allow for control of only those flows that have restrictions imposed on them
- Better control
- Less unnecessary delay

- 10/17/2001

## Approach to Multi-fix GDPs

- Retain current concept of allocating arrival slots via RBS
- Minimal technical risk
- Approach is understood and accepted by all parties
- Supports independent specification of an AAR profile for the airport and a separate one for each fix
- AARs for each fix default to that for the airport if not changed by the specialist

- 10/17/2001

## RBS Algorithm for Multi-fix GDPs

- Create arrival slots for the airport and for each fix based on respective AARs
- Fix slots are modeled as time intervals rather than points in time
- Create three sorted flight queues as in current FSM
- For each flight in each queuefind first feasible open airport slotfind corresponding fix slotif fix slot is open, 	assign flight to airport slot and mark both slots usedotherwise, find next open airport slot

- 10/17/2001

## RBS Example

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- In example, AAR for each fix 1⁄2 that for airport.
- Fix arrival slots extend over a time interval.

- Colored by slot

- 10/17/2001

## RBS Not Considering Fixes

- Flights are assigned airport slots in schedule order creating overload at Fix B

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- 10/17/2001

## RBS Considering Fix Constraints

- Flights are assigned airport slots in schedule order as long as there is a free slot at the arrival fix.

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- 10/17/2001

## Compression for Multi-fix GDPs

- Issues remain about the best way to do compression
- Several options are possible
- Allow compression only within fixes
- Can lead to inefficiencies
- Allow compression across fixes
- Can lead to over-saturation of constrained fixes
- Use smart compression

- 10/17/2001

## Compression

- A flight over Fix A is cancelled.

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- 10/17/2001

## Compression Within Fixes

- Flights can only be compressed with flights in the same fix.

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- Moves active flight before its scheduled arrival time.
-     No compression possible – inefficient.

- 10/17/2001

## Compression Across Fixes

- Allow compression between flights over different fixes.

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- Moves flight over B into arrival slot that is already filled.

- 10/17/2001

## Smart Compression

- Allow exchanges across fixes if AARs are not exceeded (if there are open slots at each fix)
- Efficient and maintains program integrity
- Works well for initial post-RBS compression
- Slots and slot assignments are available
- More complicated for mid-program compressions
- Must regenerate slots and slot assignments
- Non-FSM slots (through pop-ups, EDCT updates) disrupt the logic

- 10/17/2001

## Compression with Knowledge of Fix Constraints

- Flight over Fix B cannot be moved into filled slot.

- AP slots

- Fix A

- Fix B

- Fix C

- Schedule

- Flight over Fix C can.

- 10/17/2001

## Substitution for Multi-fix GPDs

- Airport GDPs allowed simple substitutions
- Each airline given a set of slots for its flights
- Multi-fix substitution creates issues similar to compression
- Substitutions across fixes can create overload
- Substitution only within fixes can create inefficiencies
- Smart substitution requires knowledge of fix constraints and of other airlines’ flights

- 10/17/2001

## Transition into Enroute Rationing

- Including the arrival fix as a control element provides a bridge between FSM and the airspace
- Will encourage airlines to route around congested fixes
- Explore procedures and issues regarding FAA moving flights between fixes
- Hope to further extend multi-fix concept deeper into the enroute domain

- 10/17/2001

## Example - ORD 1900Z

- Thunderstorms approaching from west*AAR at Krena and Plano at 15 / hour from 1800 to 1900*

- 10/17/2001

## Example - ORD 2000Z

- Thunderstorms continue from west*AAR at Krena and Plano at 10 / hour from 1900 to 2000*

- 10/17/2001

## Example - ORD 2100Z

- Thunderstorms pass over ORD*AAR at Krena and Plano at 0 from 2000 to 2100**AAR at Kobbs and Bearz at 0 from 2100 to 2200*

- 10/17/2001

## Example - ORD 2200Z

- Thunderstorms move East*AAR at Kobbs and Bearz at 10 / hour from 2200 to 2300*

- 10/17/2001

## Example - ORD 2300Z

- Thunderstorms leaving are to the East*AAR at Kobbs and Bearz at 15 / hour from 2200 to 2300*

- 10/17/2001