Fms Autoflight Flows

✈️ How FMS, Autoflight, Modes & Panels Work Together

Big Picture (one sentence)

The FMS plans the flight, the panels select authority, the autoflight flies the airplane, and autoland is the fully automatic end-state of that cooperation.

1. FMS (FMC / FMGS) — Planner

• Stores route, constraints, performance
• Computes LNAV / VNAV / speed targets
• Sends guidance commands to autoflight
• Does not move control surfaces itself

👉 FMS = brain

2. Panels (MCP / FCU) — Authority Selector

• Pilot interface between FMS and autoflight

• Determines who is in control:

  • Boeing MCP: pilot sets targets (windows rule)
  • Airbus FCU: pilot chooses managed vs selected

• Mode changes happen only via the panel

👉 Panels = permission gate

3. Modes (LNAV, VNAV, CLB, DES, FLCH, etc.) — Rules

• Modes define how the aircraft flies:

  • lateral
  • vertical
  • speed

• Displayed on FMA

• If a mode is not on the FMA, it is not active

👉 Modes = rules of flight

4. Autoflight (AP / FD / A-T or A-THR) — Executor

• Takes commands from:

  • FMS (managed), or
  • Panel selections (selected)

• Moves:

  • control surfaces (pitch/roll)
  • thrust (speed/path control)

• FD shows what AP is commanding

👉 Autoflight = muscles

5. Autoland — Full Automation Outcome

• Special case where:

  • FMS guidance
  • ILS data
  • Multiple autopilots
  • Autothrust all work together automatically

• Modes progress:

  • APP → LAND → FLARE → ROLLOUT

• Pilot monitors system integrity (AH, status)

👉 Autoland = autoflight at maximum authority

End-to-End Flow (exam perfect)

FMS plans path
   ↓
Panel selects authority (managed / selected)
   ↓
Modes define how to fly
   ↓
Autoflight executes pitch, roll, thrust
   ↓
Autoland = full automatic landing using same logic

One-Line Exam Answer

The FMS plans the flight path, the MCP/FCU selects authority and modes, the autoflight system executes the commands, and autoland is the fully automated landing using the same systems at maximum redundancy.

✈️ PF / PM Operational Flow (Short & Clear)

1. Departure (Take-off & Climb)

Pilot Flying (PF)

• Flies manually or monitors autopilot
• Follows FD guidance
• Requests mode changes as needed
• Maintains aircraft control at all times

Pilot Monitoring (PM)

• Sets modes on MCP / FCU

• Verifies:

  • FMS route active
  • Correct thrust, LNAV/NAV, VNAV/CLB

• Calls out FMA mode changes

• Monitors flight path, speed, altitude

System Flow

FMS → computes SID & climb profile
Panel → modes selected (LNAV/NAV, VNAV/CLB)
Autoflight → flies pitch, roll, thrust

2. En-Route (Brief Context)

• PF: monitors automation, manages flight path
• PM: monitors modes, handles radios & systems
• Both verify FMA after any clearance or change

3. Approach & Landing

Pilot Flying (PF)

• Flies manually or supervises autopilot
• Ensures stable approach
• Takes over if required

Pilot Monitoring (PM)

• Arms APP mode

• Confirms:

  • LOC / GS capture
  • Autoland status (if used)

• Calls out:

  • modes
  • deviations
  • minima

System Flow

FMS → provides approach data
ILS → provides LOC / GS
Panel → APP selected
Autoflight → LOC, GS, FLARE, ROLLOUT

4. Autoland (If Used)

• PF: monitors, ready to take over
• PM: monitors system status (LAND 3 / CAT 3)
• Both monitor Alert Height / DH logic

Key Exam Lines (Memorise)

• PF flies or supervises
• PM manages modes and monitors FMA
• Every mode change is verified on the FMA
• Autoflight flies — pilots decide

One-Line Exam Answer

During departure and approach, the PF flies or supervises the aircraft while the PM manages modes and monitors automation, with the FMS planning the path and the autoflight system executing it.

✈️ Panels, Mode Selectors & Annunciators

(FMS – Autopilot – Autoland)

1. FMS (Flight Management System)

Panels / Interfaces

• Boeing: CDU (Control Display Unit)
• Airbus: MCDU (Multi-function CDU)

What they do

• Enter route, SID/STAR, performance
• Modify flight plan
• Monitor predictions (fuel, ETA)

Annunciators / Displays

• ND – route, waypoints, constraints
• PFD (FMA) – shows if FMS guidance is being used (LNAV/VNAV, NAV/CLB/DES)

2. Autopilot / Autoflight

Panels (Mode Selection)

Boeing

• MCP (Mode Control Panel)

  • ALT window
  • SPD window
  • HDG window
  • Buttons: LNAV, VNAV, FLCH, V/S, APP
  • AP engagement: CMD A / CMD B
  • A/T ARM switch

Airbus

• FCU (Flight Control Unit)

  • ALT, SPD, HDG knobs
  • Push = managed
  • Pull = selected
  • AP buttons: AP1 / AP2
  • A/THR button

Annunciators (Both — Critical)

• FMA (Flight Mode Annunciator) on PFD Shows:

  • Lateral mode (LNAV / NAV / LOC)
  • Vertical mode (VNAV / CLB / DES / GS)
  • Speed/thrust mode
  • Armed modes

👉 If it’s not on the FMA, it’s not active

3. Autoland

Panels Used

• Same panels as autopilot:

  • MCP / FCU

• APP mode selector

• Dual autopilot engagement

  • Boeing: CMD A + CMD B
  • Airbus: AP1 + AP2

Annunciators (Autoland Status)

Boeing (PFD)

• LAND 3 → Fail-operational
• LAND 2 → Fail-passive
• NO AUTOLAND

Airbus (FMA)

• CAT 3 DUAL → Fail-operational
• CAT 3 SINGLE → Fail-passive
• CAT 2

Autoland Mode Sequence (FMA)

• APP armed
• LOC / GS
• LAND
• FLARE
• ROLLOUT

4. Quick Exam Table

One-Line Exam Answer

The CDU/MCDU programs the FMS, the MCP/FCU selects modes and authority, the FMA announces what the aircraft is doing, and autoland uses the same panels with dual autopilots and dedicated LAND/CAT annunciations.