If the bag fits...

Having just returned from a harrowing cross-country trip involving four airports and numerous delays, I'd like to make some observations regarding the lack of a coherent design for airline carry-on baggage. The only limit currently enforced appears to be, "If you can lift it, you can carry it on." During my recent sojourn, I was witness to some highly unusual carry-on items.

One woman was travelling with her pet wiener-dog, and she simply had to have the dog in her lap for the flight. The problem was that the square-shaped pooch-carrier wouldn't fit into the curved overhead compartment. I believe one lucky stewardess got to travel with the carrier on her lap. Another traveler, obviously returning from the Middle East, had an ornate, 4-1/2-foot-tall hashish pipe. He managed to maneuver it into the overhead bin, but I can't believe he was able to get it past Skippy, the customs drug-sniffing dog. Yet another traveler was wrestling on-board an item that bore a suspicious resemblance to a kitchen sink.

The reason I've cited these examples is that none of the items possibly could have fit into the handy test bin located by ticket counters, which allows travelers to determine whether they'll be able to cram their belongings into the plane's overhead bins.

It really makes me wonder just what type of design guide (if any) exists that the airline companies use when they're designing the overhead compartments. With more and more passengers choosing to travel and carry more belongings onto limited-space airplanes, something clearly needs to be done.

As with more typical engineering problems, the first step is to identify our options: either the bags are too large for the space, or the space is too small for the baggage. Alternatively, there is simply too much "stuff" being carted across the country. If we agree that it is a basic human right to be able to carry aboard as much as we'd like, then our options are limited to either providing more space or designing smaller carry-on bags.

One of the design constraints for existing aircraft deals with the overhead compartment space. By using the arbitrary "tube" design for the plane's fuselage, there is simply no alternative to the rounded shape. Unfortunately all alternative bin geometries have been rejected by the airline companies. They keep citing something about aerodynamics.

It would appear that the plane and the overhead compartment are going to retain their tube shape characteristics for the foreseeable future. This conclusion limits us to improving the design characteristics of carry-on bags. In order to make maximum use of the available space, all bags need to be flexible in shape, enabling the traveler to use only a slight force to reshape the bag so it becomes a conformal fit with the available space.

As for the bag we all really need-one that is bigger on the inside than the outside-that's another engineering challenge altogether.

This report is one of a series of occasional columns exploring the not-altogether-serious side of engineering by Ken Foote, a mechanical engineer at GDLS. You can reach Ken at footes@chartermi. net or e-mail your comments to us at [email protected].

HEAD WORK

A bag having a mass of 20 kg flies out of an overhead bin with horizontal velocity v _o = 6 m/sec from a height H above the flight attendant's cart, on which it lands. The cart is originally at rest, has a mass of 40 kg, and has negligible rolling friction. The final velocity of the cart in meters per second (after the package has stopped moving with respect to it) is most nearly:

A) 1

B) 2

C) 3

D) 4

E) Cannot be determined without knowing H

See answer below.

Adapted from the Fundamentals of Engineering Examination, Eugene L. Boronow, Prentice Hall Press, 1986. Answer: B