While cursing my bad luck, I noticed that the passenger one row up and across the aisle had an equally deformed tray table. The flight attendant saw immediately upon setting down his drink that it would not stay in place on the slope. She returned to the galley and came back with the aluminum tab she had broken off a pop-top can, and she used it to shim up the cantilevered tray at its main hinge. When she came with my drink I asked for the same mechanical assistance, and she obliged. The fix was just right, and the table was perfectly flat and horizontal even when fully opened across the seat. Thank goodness for shims, and for mechanically inclined flight attendants.
The folding tray table was obviously designed to satisfy a considerable number of constraints, which it does. Thus, it is relatively lightweight, as well as compactable and deployable. These latter two qualities mean it has moving parts that are capable of getting out of kilter. Armrest tray tables clearly have not been designed to take the forces imposed by infrequent fliers wrestling with the puzzle of how the thing deploys and stows, or by frequent fliers who use the table as a crutch for rising out of their seat. Such overloads naturally can and do throw the mechanism out of alignment. All designs have limitations, but not every user respects them.
The case of the airline tray table points out one of the asymmetries of the designer/user interrelationship. The failure of an armrest tray table to deploy into a flat and level surface, perhaps leading to a drink spilling into a passenger's lap, might result in a product-liability lawsuit, with possible career-altering implications for the table's designer. But a passenger who engages in heavy-handed misuse of the table, causing it to be permanently off level when in its deployed position and thus setting the stage for a drink spilling into some future passenger's lap, can simply walk off the plane when it reaches its destination. Neither life nor design is always fair.
Ann, Beth, Dave & Prof. P., I write this as you Professor wrote your article on arm chair design....with toung in cheek. The story starts with me being the only person, other than crew, left on a plane durind a short layover. A AL Mechanic arrived and went to work on one of the tables you all described. He almost instantly recived a loud message over his 2way "you have 5 minutes". He started to work very delicatly and expertly for the next 10 minutes when he received a VERY loud call "you need to pack it in we have to load."
Being a company man (I determined by his appearence) he reached down to his tool belt, holstered his Phillips Head screw driver swept his hand dirrectly to the hammer loop, grabbed it , pounded the table into the midseat container, flipped the cover closed and annouced towards the Captain "All fixed sir she's ready to go have a good flight" while exiting the aircraft.
THIS ALL HAPPENED FASTER THAN THE TIME IT TOOK ME TO WRITE THIS. It sticks in my mind to this day because I am also a Pilot.
The nice thing about the tray tables that Professor Petroski describes is that they are not attached to the seat back. Anything is better than that. If I put my laptop on one of those, the person in front of me glances back over his/her shoulder to let me know I'm bothering them. Worse, when the person in front leans back, the tray table is suddenly so close that there's no room to work.
It's been years, but I remember a flight with, I swear, that same tray table "design," which made it completely unusable when deployed. And that was so obviously the case that I could not understand how the design ever got accepted and the tray table installed, in thousands of planes. I was not so fortunate as Professor Petroski, however, in my flight attendants. This all makes me think less of the legal issues than of the designers/users and use case issues.
Professor Petroski's final point in this article alludes to the fact that product liability law requires a product to be safe not only in its reasonably expected use, but also any reasonably expected misuse. Engineers are often horrified to learn that the law requires us to take potential misuse of a product into account. Ironically, although we bristle at the idea of other people misusing our products, we also excel at coming up with creative new ways to "use" products others have designed. Some of the new uses which particularly creative engineers find for things may not fall into the "reasonably expected" category.
Entertaining musing on the give and take of good design. What's the greater takeaway for engineers, though? Don't factor use case into your efforts for fear of legal repercussions? That seems like a cop-out to me. After all, not every flight enjoys the benefit of having mechanically-inclined flight attendents on board.
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The word “smart” is becoming the dumbest word around. It has been applied to almost every device and system in our homes. In addition to smartphones and smart meters, we now hear about smart clothing and smart shoes, smart lights, smart homes, smart buildings, and every trendy city today has its smart city project. Just because it has a computer inside and is connected to the Web, does not mean it is smart.
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