Transport Canada - Emergency Airworthiness Directive for the C Series

[zerograv]

EAD for the C Series, also known as A220.

AD Number: CF-2022-64, Effective 18.Nov.2022

Limitation - AUTOPILOT ENGAGEMENTWARNINGAutopilot engagement during takeoff roll can result in premature rotation, possibly leading to tail-strike, inability to climb or loss of control. Immediate crew intervention is required.

[Splat]

Why would anyone want to do that?

[zerograv]

Why would anyone want to do that?

The comment that I made, and then deleted, probably caused a incorrect interpretation. Sorry for that !

It seems that the crew might unintentionally or inadvertently engage the AP during the takeoff roll.

[Lonewolf_50]

Nothing is idiot proof.
If you make something 'idiot proof' the world will inevitably provide you with bigger idiot. :p

[Asturias56]

Barnes Wallis "the problem with making something fool-proof is that the fools are so clever"

[Australopithecus]

On which aircraft can you in fact safely engage the autopilot during take-off? This caveat seems completely obvious akin to publishing an AD requiring gear down landings, unless the A/P is particularly easy to unwittingly engage.

Can any A220 pilots comment?

[Semreh]

SLF here: Would there be any benefit in a general autopilot engagement lockout for a suitable length of time after weight-on-wheels transitions from showing weight to showing airborne? I don't know if this type has WoW.

[Equivocal]

Kinda makes me wonder about the system design and safety analyses.....and the regulator that accepted them.

[WingNut60]

Is there a prelude to this, along the lines of "Following an incident where .................."

[Clandestino]

Turns out folks were trying to re-engage athr during takeoff run and inadvertently engaged the AP.

Single AP button on A220 is the same shape, size and colour as ATHR button and situated immediately above it.

[aeromech3]

Always imagined this was inhibited by weight on at least on aircraft I had worked with!
Certainly for auto land checks, as the pitot and mast heater CB's needed pulling before air mode.

[vickers vanguard]

Incident: Air France B773 at Lagos on Jan 12th 2010, rejected takeoff (http://avherald.com/h?article=428c9bdd/0000.......similar) incident happened to an AF 777

[FLX/MCT]

A/T disconnects during TO roll are rather common on the CSeries during (gusty) crosswind conditions. This is due to the A/T application only using a single airspeed source whereas the monitoring function uses a consolidated value. If they disagree too much, it will disconnect.
As already mentioned the buttons look and feel the same and are positioned just next to each other on the flight control panel. There were several cases (obviously in different companies) where crews tried to reengage the A/T, few of them pushed the AP button, which will eventually command up to full up elevator deflection.
For me these events are a combination of poor system design (IMHO the A/T generally is a mess on this plane) and pilot training (why should one attempt some button pushing on the FCP during takeoff roll?! there are thrust levers for a reason...), but I am quite surprised the authorities are only picking up now on these incidents, being familiar myself with them since more than 2.5 years.