AB Dual Hyd failure describes as "Dimensioning failure"

[LUPA93]

Can someone help me fully understand what the A340 FCTM really means by the term "dimensioning failure" in the introduction text to DUAL HYD Failures :


Although this is an improbable double failure in operation, it is a "dimensioning" failure case for abnormal operation on Airbus aircraft because of the following consequences:
- It leads to the loss of AUTOPILOT
- It leads to Flight Control Degraded law (ALTN)
- It leads to land in Abnormal Configuration
- It leads to a thorough use of the ECAM, and QRH
- It leads to properly envisage different safety factors in Approach & Go Around

[NigelOnDraft]

Expect to do it in the Sim ;)

[MD80rookie]

Get used to many more french-english translations in Airbus material that is somewhat difficult to grasp.

They might mean that it is a failure with many dimensions (i.e. many things has to be considered).

[Mr Optimistic]

My guess is that it implies a bounding situation which invokes a wider range of consequences/fallbacks/degradations than other examples. Not a pilot but that would be my hunch.

[vilas]

Airbus uses important as appropriate and may be dimensioning is used for significant or serious.

[Mad (Flt) Scientist]

In design in English, we often use the term "sizing" to mean a critical case, as in "the mistrim takeoff is the sizing case for the elevator", when it's the design case from which the required size (or performance or capability) of something is determined.

Could they be somehow using "dimensioning" in that sense, as if it were "sizing" or determining the capability of the systems or crew to cope?

To be honest, we happily use "unstick" as a literal translation of the French term, without it making a lot of sense in English, so the language barrier IS bidirectional. (Never minding the transatlantic chasm ...)

[BuzzBox]

The introduction to Dual Hydraulic Failures in our 'anglicised' A330/A340 FCTM reads as follows:

Dual hydraulic failures however, although unlikely, are significant due to the following consequences:
• Loss of AP
• Flight control law degradation (F/CTL PROT)
• Landing in abnormal configuration
• Extensive ECAM procedures with associated workload and task-sharing considerations
• Significant considerations for approach, landing and go-around.

So yes, 'dimensioning' seems to imply 'significant'.

[compressor stall]

Surely the simplest way the think is that this type of failure has many dimensions.

Some failures are one dimensional, in that your thought and management for rectification need only consider that system. Your actions are one dimensional.

A dimensional failure affects multiple systems, simultaneously. Your actions might involve other systems prior to (or whilst) getting around to managing the failed system.

[vilas]

The word dimensional does not exist any more. So obviously it was a mistranslation. It is now correctly written as significant. So we should forget about it.

[LUPA93]

Thnks everybody for your "dimensioning" answers.
Abrazos,
LUPA