The tray table that folds in half for stowage in the armrest of an airline seat is something I have long admired for its design ingenuity, but long cursed for its operational opaqueness and flimsiness. On domestic flights, tables of the kind I am describing are usually found in the first-class cabin and on seats facing a bulkhead. The more common rigid tray tables that swing down from the back of the seat in front of a passenger are obviously less costly to manufacture and install, and so are used wherever the seat pitch allows them.
But even before the more complex armrest table can be deployed into a (hopefully) flat and horizontal position, the airline passenger has to get the thing out of its underarm pocket. This can be more easily said than done, for there is no standard feature to grasp on the stowed table. Some models have a fabric loop, some a trigger-like hook, and some a corner hole. Since not all passengers are able to contort their bodies or squint their eyes sufficiently to see what aid might be lurking in the dark recess, they tend to feel around for a familiar shape and tug on it.
Once the table has been wrestled out of its hold, it can typically be rotated about an orthogonal axis to become a half table, often with a slight depression in its surface to keep drinks from walking off the edge during air turbulence or just under ambient vibration. It is in deploying this half table that passengers might first discover that the top can have a pronounced incline. On a recent flight from Chicago to Raleigh-Durham I found myself with such a table. As I waited for the flight attendant to bring me a drink, I almost put the table back into the armrest, since I would have had to hold the glass anyway.
The detailed design of the kinematically clever deployable armrest table understandably varies from airplane model to airplane model, but virtually all variations seem to depend for their operation on two primary mechanical principles: the hinge and the cantilever. Some also contain a slide or swivel feature, which enables the more corpulent user to push the tray forward or aside to gain some breathing room.
In one common form, the two halves of the table have their top edges connected through a pair of link hinges; the bottom edges of the two halves butt up against each other, providing reaction forces. Collectively, the forces maintain a cantilevered table top in a flat and horizontal position. One familiar form of tray table, when fully deployed, forms a bridge of sorts between a seat's armrests.
On my flight where the folded table sloped downward, the unfolded one would also have -- had it not been for the opposing armrest providing a support constraint. Thus, the fully opened table top formed not a flat plain but a shallow valley. The two halves inclined toward the center, creating a V into which everything from pencils to peanuts to plastic drink glasses would want to slide.
Yes, Henry, I agree that ticket price is paramount for air travel consumers -- including myself. And I can't imagine travelers choosing on airline over another based on anything but price. So I guess that says it all. No reason to improve comfort.
The airlines may be satisfied with the design of the interior elements of their planes, but of course that does not mean that there is not room for improvement. The main selling point for economy air travel seems to be ticket price. Passengers seem to give that much greater priority than amenities relating to seat comfort. My feeling is that until passengers in large numbers let it be known that they are not satisfied with what the flying experience is like, the airlines will not redesign it beyond changes that bring in more revenue, such as more leg room, etc.
Thanks Henry. Yes, I understand the economics of space for the back of the plane. And the space has grown smaller over my decades flying. The basic design of tray tables, arm rests, seatbelts, etc. has also been static for decades. I would guess the airlines are simply satisfied with these design elements.
Airlines seem to have put their seating R&D dollars into improving the business and first-class sections on international flights, where seats transform into beds of a sort. Econmony class seat design does seem to have been static for some time. There has been, however, some improvement in leg room for a price to the customer. With the increasing prominence of narrow-body regional jets, it seems unlikely that economy-class seats will get wider. There seem to be simply too many constraints from available space and revenue to allow for much improvement.
The maintenance story reminds me of an episode of the cartoon Animaniacs in which two of the characters are trapped in an elevator. They try to contact the maintenance department over the intercom, and overhear the supervisor telling one of his employees: "Hit it with the hammer, Big Ed. No, the hammer... that's a wrench, that long thingy's a hammer..."
Later, after being trapped in the elevator for ten hours, the characters try to contact the maintenance department again.
"Are you still in there?" the maintenance supervisor replies. "It was our indication that you got out."
"Really?" the character says. "What gave you that indication?"
"That's just an indication we had," says the supervisor.
I haven't seen significant design improvements in the seating area of airline jets since the mid-1970s. Am I missing something? If anything, the seating area has become more cramped.
The story of the mechanic pounding the broken table into submission is great! It shows how the human element can be the ultimate enemy of designs of all kinds. I wonder how long it took that tray table to finally be fixed so it could be both gotten out of and put back into the seat arm? Poor maintenance can be worse than no maintenance at all.
This article by Mr.Petroski is a guiding for the young engineer by showing how to clearly express the design functionality. Many a times innovators fail to express the "need" in their statements.
The cardboard tray wouldn't weight much more than the plastic plate sitting on it, and unlike the plate, the tray would normally be secured. Even if left unsecured the tray wouldn't be much of a projectile, but adding foam-rubber edging would limit the damage when kids play with the trays. In normal use the edging would also keep cups and plates from sliding off.
I had to check the date of this commentary - 2012, not 1965! In the '70s I worked in aircraft seating design. Those First Class seats were a wonder of engineering. Their weight-saving, weight-supporting design were worthy of awards. I'd think the present-day comments would have been unwarranted, even back then. Surely engineering has progressed since...or has it?
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