Operators of Embraer 170 and 190 regional jets are being instructed to modify control yokes to prevent horizontal stabiliser trim switches being inadvertently wrongly installed.

Brazil’s national civil aviation regulator, ANAC, has advised of “occurrences” in which the pitch-trim switches on the yokes have been fitted with poles inverted.

This would result in “opposite commands” for the horizontal stabiliser when the switches are activated, says the regulator in an airworthiness directive.

“It is necessary an action [is ordered] that prevents the incorrect installation [switches],” it adds.

Operators of several variants of E170 and E190, with particular yoke assembly part numbers, are being told to fit a “support” on the yoke to avert misfitting of the switch.

ANAC’s directive, effective from 26 May, states that the modification should be carried out within 18 months.