Aircraft slim seats – how low can you go?

In the cost-driven, commoditised economy-class space, airlines have been moving quickly to cut seat weight and add extra passenger space by installing new slimline seating.

The incentives are hard to pass up – slim seats mean lower weight and thus operating costs, more flexibility to generate ancillary revenue charges for extra-legroom seats, and potential turnaround time improvements.

But what’s the passenger reaction to slim seats? What tradeoffs are acceptable, and when? How far can airlines go?

SLIMLINE SEATS ARE ABOUT DEPTH

Slimline seats are not necessarily made for skinnier passengers. Instead, they’re about reducing structural weight and using novel engineering to claw back the “wasted room” in seat pitch between one passenger’s knees and the back of the passenger in front.

Over the length of an aircraft, an inch saved per seat can create an entire extra row every thirty rows or so. That’s obviously a win for airlines even before you start calculating weight savings.

So, how do you slim down a seat?

Swap a rigid backplate to a semi-rigid version, usually out of a lightweight but robust plastic, to separate passengers’ knees from the back in front of them.

Slim down the table, too – reduce it in size, and balance the supporting structure’s strength with reduced weight.

Consider removing the seatback pocket entirely, although this concurrently reduces the opportunity for ancillary sales from the “flipping through the magazine” crowd. [You can always move the literature pocket up and away from knees if you don't plan to offer seat-back IFE.]

Choose lightweight, thin foam for the seat. Slimline seats are generally designed for shorter sectors, so you can get away with less generous padding.

Cover the seat with leather or similar synthetics, going for weight, sturdiness and the “wipe-down” quotient.

But keep an eye on passenger-to-crew ratios, which vary by labour agreement and regulator: adding more passengers is not necessarily an automatic net positive.

ONE FOR ME, ONE FOR YOU…

Some airlines are snapping up all the benefit of the reduced pitch for their bottom line, maintaining (or even reducing) the amount of knee-to-back space that passengers had with older seats.

Other airlines, perhaps more concerned with passengers’ perception of being squeezed, are splitting the difference with passengers: an inch for you, an inch for me, and everyone’s happy.

As a general rule, the passenger experience on airlines that split the difference is more positive.

SEAT PAN DEPTH PERCEPTION

A frequent criticism of slimline seats is that the seat pan is shallower than passengers are used to in older seats.

Reduced depth is undertaken partly for weight reasons, and partly to make the pitch seem greater. Passengers’ perception is influenced by the distance between the seat-back in front and the front of the seat pan.

Some passengers are happy to take the trade-off of an extra inch of pitch in exchange for a shorter seat pan, while others would prefer to have more of their hamstring area supported.

As sector time increases, passengers perceive a lack of seat pan depth more: the airborne equivalent of sitting on a bench rather than a dining chair.

SEAT WIDTH IS UNDER-PERCEIVED

It’s interesting that seat pitch – a measurement that completely misses the advantages for airlines and passengers of slimline seats – is such a common metric, yet seat width is not.

Standard seat width on an Airbus A320 narrowbody is roughly 18″, compared with 17″ on Boeing 737 competitors, thanks to the greater cabin diameter of the slightly larger Airbus – unless airlines choose narrower 17″ seats and a slightly wider aisle to speed boarding and deplaning.

Airlines could use seat width to position themselves as premium carriers offering more space, even while using slimline seating.

SLIMMER SLIMLINE SEATS: IS THE SKY THE LIMIT?

Simple human leg geometry means that femur length – with a bit of padding on the backside – is the main factor limiting how closely an airline can pack seats in.

Taller passengers will be less receptive to reducing this space, and vice versa. This provides opportunities for airlines in regions where the populace is generally shorter to gain a competitive advantage among those markets.

But designers can play around with the geometry too. What happens if the seat pan is elevated so that the formerly horizontal femur starts taking on a downward angle from hip to knee?

The oft-rumoured, never-certified “saddle-style” or “standing-room only” mock-ups are the extreme of this geometry game, and despite continual discounting they keep popping back up.

But “elevated seat pan” seats are an opportunity to explore the possibilities of geometry in a less obvious way.

Shifting the geometry to the diagonal – having seats angled inwards towards the aisle or outwards towards the window – could also be an opportunity. With seat width at 17-18 inches and seat pitch between 28-34 inches, a slight shift of angle could create extra space at the same time as accommodating plumper passengers.