FAA Invites Comments on Flightdeck Controls Draft AC

The FAA is accepting public comment through September 24 on a draft update to its human factors guidance for flightdeck system controls Advisory Circular, which would replace15-year-old AC 20-175. The draft, AC 20-175A, retains the original’s scope of cursor control devices, touchscreens, speech recognition, and dedicated switches and knobs, while adding guidance for aircraft designs and cockpit technologies that have emerged since 2011.

Proposed guidance applies broadly to aircraft certified under Parts 23, 25, 27, and 29, a scope that includes light and midsize business jets, larger business jets, and business and utility helicopters, as well as airliners and other aircraft categories. The most notable addition addresses “emerging aircraft,” including powered-lift and eVTOL designs. The FAA writes that these aircraft “often possess unique designs, flight, and handling characteristics” but that the human factors principles in the rest of the AC “are also applicable to the flightdeck controls” of these aircraft.

More Redundancy

The draft also adds a section on multimodal controls, which allow a pilot to access the same function through more than one input, such as a cursor device, touchscreen, and/or speech command. “A possible benefit of multimodal controls is redundancy,” according to the document, since a pilot retains alternate options if one input mode fails.

Guidance on permanently installed controls that are labeled but not functionally connected to a system is included, depending on the configuration of individual aircraft. “When installed, these non-customizable avionics may have control functions that are not integrated into the system but are still labeled with the intended function. If permanently installed controls in the flight deck are purposely non-functioning controls,” the draft stated.

It adds that labeling such a control “INOP” does not satisfy compliance. The document outlines three acceptable design remedies: removing the control from the type design, capping or blanking the control, or adding a mechanical stop that limits a knob to its functional range.

The draft also adds dedicated guidance on emergency controls, such as fuel shutoff or jettison controls, requiring that such controls be colored red or illuminate red when a condition requiring their use arises, and that they be “readily identifiable under all lighting conditions.”