A320 Mode Reversions

Today we take a look at A320 mode reversions. What are reversions you may ask? Reversions are automatic mode changes that take place when unexpected or unreasonable demands are asked of the aircraft ensuring consistent, coherent AP, FD and ATHR operations.

We will take a look at them in the following order:
00:20 Reversion due to a change of the FCU selected altitude.
02:25 Reversion due to the loss of NAV mode (Manual or Automatic).
02:50 Speed protection when FD orders are not followed by the flight crew (AP not engaged).
03:40 Speed protection due to excessive V/S.

Acronyms used in this video:
AP – Autopilot, ATHR - Auto thrust, FD – Flight Director, V/S – Vertical Speed, SID – Standard Instrument Departure, STAR – Standard Arrival Route, VMAX - Maximum Allowable Speed, VLS - Lowest Selectable Speed

Trivia:
- When a mode reversion occurs, it is accompanied by a triple click aural warning.
- Airbus defines mode reversions as 'mode changes that unexpectedly occur', but anyone in regular line flying will be familiar with at least the reversions due to FCU altitude changes and the loss of navigation mode associated with a lateral discontinuity.
- A mode reversion also features towards the end our video 'Airbus Holding - The Basics' as the aircraft leaves the holding fix at DAYNE.    • Airbus Holding - The Basics  

Interesting Stuff / Further Reading:
- Manual Reference - A320/1 FCOM/Aircraft Systems/Auto Flight – Flight Guidance/Mode Reversions (22 30-75).
- There is a further reversion as such, not covered in this video, for aircraft fitted with TCAS mode (automatic TCAS). The aircraft will follow the TCAS RA vertical speed target, even if it is excessive, at the expense of speed. Once VLS or VMAX is reached the vertical speed is automatically adjusted to maintain VLS or VMAX as appropriate. The TCAS mode remains engaged, and no triple click is heard.

Note:
This video is published for familiarisation purposes with our simulator only and any views expressed within this video are our own. Some calls and checks have been omitted for brevity. Always refer to your company documentation or appropriate flight crew manual as the primary reference.

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