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ALB Flow and EAT Operations Guide

Will be available in 0.2.11 or 0.2.12

This guide explains how EAT works in ALB from a controller point of view: what you see in the UI, what the buttons do, and how collaboration works between an FMR (digital coordinator) and peers.

Current baseline: EAT:AR (arrival‑rate based). A future “EAT to landing slot” mode (EAT:Landing / EAT:Threshold) will be documented later.

Abbreviations

  • EAT — Estimated Approach Time (ALB’s scheduling time reference)
  • FMR — Flow Management Responsible (coordinating authority for the plan)
  • TXE — Transmit EAT requests (FMR toggle: request peers publish holding-list EAT)
  • HLW — Hold‑List Write accept (peer opt‑in: allow ALB to publish holding-list EAT for aircraft you control)
  • HLS — Holding‑List Sync / override ingestion (treat holding-list EAT as a constraint in the plan)
  • EATLOOP — (will be renamed) Drift correction / cascade correction of downstream timing
  • SWAP — Swap two aircraft in the sequence
  • PLR — Planned Landing Rate (used by EAT:Landing later)

1) EAT modes: EAT:AR vs EAT:Landing (future)

EAT:AR (current baseline)

EAT:AR maintains spacing using arrival‑rate assumptions per stream/via‑fix. It is robust and simple, but can become crude when: - traffic distribution across STARs changes over time - heavy vectoring makes route‑based prediction unreliable - winds/groundspeed changes distort timing

EAT:Landing / EAT:Threshold (future)

EAT:Landing aims to schedule aircraft to landing slots (FAF/threshold) in order to achieve a target PLR at the airport (not runway). In that mode: - the schedule is driven by slot availability, not by stream arrival rates - spacing may not be uniform across streams - manual constraints and SWAP remain the primary controller tools

2) What EAT means in ALB (today)

ALB maintains two “views” of EAT:

  • Auto EAT (ALB plan)
    The time ALB currently predicts/targets for an aircraft (today: EAT:AR). This drives sequencing and spacing.

  • Holding‑list EAT (controller-visible)
    The EAT shown in the TopSky holding list / holding UI. Controllers can set this manually and monitor it.

ALB can optionally help publish holding‑list EAT values, but only if the responsible controller opts in (HLW).

3) Roles and authority

FMR (digital coordinator)

When FMR is active, the FMR’s ALB instance is the authority for the master plan (order and target spacing). FMR can request that peers publish holding‑list EAT values for aircraft they control.

Peer / responsible controller

The responsible controller always retains authority: - you can set a manual holding‑list EAT at any time; - you can reorder aircraft using SWAP; - you can opt in/out of ALB publishing holding‑list EAT on your behalf.

4) Coordination when nobody manually claims FMR (Auto‑FMR)

If no controller explicitly claims FMR, ALB can run Auto‑FMR:

  • Multiple ALB clients may be online for the same destination.
  • One client is auto‑selected as FMR using a negotiation method (based on factors like visibility and number of aircraft viewed).
  • If a controller manually claims FMR, that manual claim overrides the auto selection.
  • The current FMR status is visible via ALB’s peer/legend displays.

Operational implication: - Auto‑FMR provides “a coordinator by default” so the system can keep a coherent plan even without a dedicated human FMR.

5) Buttons and indicators

TXE (FMR)

TXE controls whether the FMR will request holding‑list EAT publication.

  • TXE ON: FMR issues publication requests (rate‑limited and change‑thresholded).
  • TXE OFF: FMR does not request holding‑list publication.

Use TXE when you want ALB to actively drive holding‑list values to keep everyone aligned.

HLW (peer opt‑in)

HLW is your opt‑in switch that allows ALB to publish holding‑list EAT values for aircraft you control when requested by FMR.

  • HLW ON: ALB may apply coordinator requests for aircraft you are responsible for.
  • HLW OFF: ALB will not change holding‑list EAT for your aircraft.

Attention highlight:
If an FMR has TXE enabled and your HLW is OFF, HLW is highlighted (light yellow background) to prompt you that the coordinator is requesting opt‑in.

HLS (holding list sync / overrides)

HLS controls whether ALB treats a holding‑list EAT as an override input.

  • HLS ON: a manually set holding‑list EAT is treated as a constraint and influences planning.
  • HLS OFF: holding‑list EAT is displayed/monitored, but does not override the plan.

This is most important at the FMR, so the master plan honors real controller constraints.

EATLOOP

EATLOOP is ALB’s “drift correction” mechanism: it keeps the plan coherent over long sessions by re‑aligning downstream timing when reality diverges from the plan.

Operationally, EATLOOP is intended to be safe and generally enabled.

SWAP

Swapping two aircraft in a specific STAR flow is done in the TimelineView by double-right clicking the aircraft you want to move forward in the flow. SWAP is the “cheap tool” to fix ordering:

  • Use SWAP when the schedule is correct in principle but two aircraft need to trade places.
  • A SWAP changes both the local and global sequence so everyone stays aligned.

Peer dropdown table

The peers dropdown shows, per connected peer, their current state: - HLW on/off - HLS on/off - (optionally) TXE / other preference flags

Use this to see who has opted in to coordinator publishing.

Manual marker in the timeline: m

A small 1‑character indicator field is available:

  • m = holding‑list EAT is manual/controller-set
  • empty = holding‑list EAT is automatic / ALB‑applied

Where it appears: the m is shown in ALB’s timeline view, using the gain/lose (gain/loose) column/field (not in the TopSky holding list).

6) Normal workflows

6.1 FMR workflow (digital coordinator)

1) Claim/act as FMR (or rely on Auto‑FMR if nobody claims). 2) Enable TXE if you want ALB to request holding‑list publication. 3) Monitor the peers dropdown: - peers with HLW OFF may not apply requests. 4) Use SWAP to correct ordering when needed. 5) If controllers set manual holding‑list EAT values, keep HLS ON so the plan respects those constraints.

6.2 Peer workflow (responsible controller)

1) Decide if you want to opt in to coordinator requests: - enable HLW if you accept ALB publishing holding‑list EAT for your aircraft. 2) If the plan needs correction: - set a manual holding‑list EAT (it will show m in the timeline) - use SWAP to adjust ordering 3) If you want your manual entry to influence planning: - enable HLS (especially useful if you are coordinating a stream locally)

7) Common situations and expected behavior

“I set a manual holding‑list EAT”

  • The timeline shows m next to that aircraft (in the gain/lose field).
  • If HLS is ON (at the FMR), the manual EAT acts as a constraint and will influence spacing behind it.

“FMR is requesting but my HLW is OFF”

  • HLW button is highlighted.
  • You will not see holding‑list EAT values being changed automatically for your aircraft until you enable HLW.

“FMR resigns or disappears”

  • Coordinator requests stop.
  • Controllers continue with local planning and manual holding‑list control.

8) What changes with EAT:Landing later

EAT:AR keeps approximate spacing using arrival‑rate assumptions. EAT:Landing will instead target landing slots to meet PLR at the airport level. Manual overrides and SWAP remain central tools in both modes.