Aviation safety issues and actions

No consideration of dual control inputs on aircraft response in the design standard

Issue number: AO-2014-032-SI-06
Who it affects: All operators of ATR 42 and ATR 72 aircraft
Issue owner: European Aviation Safety Agency (EASA)
Transport function: Aviation: Air transport
Background: Investigation Report AO-2014-032
Issue release date: 24 May 2019
Current issue status: Safety action pending

Safety issue description

Although the design standard for the aircraft (JAR-25) required the control system to be of sufficient strength to withstand dual control inputs, it did not require consideration of the effect that dual control inputs may have on control of the aircraft. Similarly, the current design standard (CS-25) does not address this issue.

In September 2018, EASA advised the ATSB that:

…before anticipating any possible review of the CS-25 regarding the dual control input, the EASA Upset Prevention and Recovery Training (UPRT) should ensure that abrupt and large alternating inputs as well as dual opposite inputs are limited especially in abnormal, high stress situation.

It can be made reference to the EASA opinion No. 06/2017 on 29 June 2017. For the time being, 8 April 2019 is envisaged as the day from which the new regulatory framework on UPRT will apply.

ATSB comment/action in response

The ATSB notes EASA’s efforts in respect to the operational aspects of aircraft Upset Prevention and Recovery Training and acknowledges that it is likely to improve flight crew’s responses to abnormal situations. However, dual control inputs are likely to continue to occur for a range of reasons, as previously identified by Airbus, and operational training does not address the potential vulnerability of aircraft design to the effects of dual control inputs. Thus, the ATSB makes the following safety recommendation:


Action number: AO-2014-032 SR-054
Action organisation: European Aviation Safety Agency (EASA)
Action status: Released

The ATSB recommends that EASA take further action to review the current design standard (CS-25) in consideration of effect that dual control inputs may have on control of aircraft.

Last update 24 May 2019