What really happens to a 45 kg piece of checked luggage when it travels by air? Members of the Art in Transit Research Program decided to find out, with the help of an electronic data logger.

CCI has recently acquired two electronic data loggers that will be used to obtain a dearer picture of shipping events and hazards as part of the Art in Transit Research Program. Each logger contains electronic circuitry capable of measuring shocks that exceed a pre-determined level. An internal dock records the date and tune of each shock event. This information is stored electronically for later downloading to a computer. When the data is downloaded, the direction of impact is calculated and a summary is produced in which the shock and impact events from all sources (e.g., drops, kicks) are expressed in terms of an equivalent drop height.

In order to become more familiar with these devices, one was placed inside a 45 kg packing case that contained demonstration material and fragile electronic equipment. This case was shipped to a series of Art in Transit workshops that were presented by CCI in collaboration with the Smithsonian Institution and the National Gallery of Art in Washington, D.C.

A total of 17 flights were monitored, covering a total distance of 20,000 km to venues in Vancouver, B.C.; Los Angeles, California; Chicago, Illinois; and Washington, D.C. An additional flight to Regina, Saskatchewan, was also monitored. For all of these flights, the case was sent through the usual luggage stream as ordinary checked baggage with "Fragile" and "This End Up" stickers attached.

During the 17 flights, the packing case and its fragile contents were subjected to 34 rounds of airport baggage handling personnel and equipment. Here is what happened,

The case experienced a total of 843 impact events. All of the recorded events occurred during handling operations at the 34 transfer points. An impact summary, expressed as equivalent drop heights, follows.

Figure 1.The packing case used to transport demonstration equipment to a series of Art in Transit workshops. The case measures 80 cm x 42 cm and weighs 45 kg.

Figure 2.The electronic data logger inside the packing case prior to shipment.

Figure 3. The data logger measures 11 cm x 11 cm x 6 cm. It can record the time and date of the occurrence of hundreds of shocks over extended periods of time.

The data recorded during the 17 flights revealed that the packages received many drops from lower heights and few drops from higher heights. This is consistent with generalizations found in the packing literature. The three largest impacts (equal to drops higher than 45 cm) each occurred on separate journeys.

Of the 843 impact events that were recorded, 68% were impacts against a flat side of the case, 26% were impacts along an edge, and 6% were impacts against the comers of the case. This also agrees with generalizations found in the literature: as package size increases, the probability of edge and comer drops decreases.

Of 571 flat drops, 285 were against the bottom of the case. The other flat surfaces of the case received between 12 and 105 impacts. The surface that received 105 impacts was the back of the case (opposite the front handle). This illustrates the effect that the orientation and placement of the handles can have on how a package is manipulated. The large number of drops to the bottom of the case also indicated that it was frequently handled and moved with the "This Side Up" stickers in the correct direction. it is worth noting, however, that trying to lift the case with the handles upside down is quite painful, which may have had a greater effect than the labels for maintaining the correct orientation of the case!

The highest impact recorded during the 17 flights was equivalent to an 84 cm drop. This impact occurred on the third of the five trips.

The four most severe drops ranged from 44 cm to 84 cm. Two of these drops occurred at Canadian airports during handling operations for flights with two different Canadian-based carriers, and two occurred at U.S. airports during handling operations for flights on two different U.S.-based carriers.

So, what happened to the fragile equipment? Nothing, because the cushioning inside the case had been selected to keep the transmitted shock levels well below levels that would damage the equipment for a 75 cm. drop. As a result, the highest shock level transmitted to the equipment inside the case during the greatest (84 cm drop equivalent) impact was only 36 G, and the equipment can withstand shocks of up to 70 G.

In order to avoid shipping damage, one should benefit from the observations and experience of others to arrive at reasonable estimates of handling risks. Learn the methods frequently used by commercial package designers, which involve relating package characteristics such as size or weight to the most likely handling methods, in order to estimate the height from which a package may be accidentally dropped. The reasoning behind this approach is that as packages become larger and/or heavier, the height to which they are lifted, and from which they are likely to be dropped, is generally expected to decrease.

A summary of probable drop heights based on different handling methods is provided in Table I. When shipping highly valuable or fragile items, design packages to a higher-than-anticipated drop height. For example, a drop height of either 60 cm or 75 cm could have been used to design the cushioning for the case described in this article. In. light of the value and fragility of the contents, the cushioning was designed for a maximum drop height of 75 cm. When trucks are used to transport fragile or valuable items, it is also common to anticipate an accidental drop from the tailgate. In this situation, a 75 cm drop height can be used regardless of package weight.

The results of this empirical study show a good agreement between the 75 cm. design drop height obtained from probable drop height tables and the actual airport handling data for a 45 kg package. The data also illustrates that the design of a cushioning system should predict a reasonable worst case scenario even if it has a relatively low frequency of occurrence. And, finally, the results show that the worst case scenario will eventually happen!

Note: For light packages shipped by parcel post, the drop height can be up to 3 m.

CCI has developed a Cushion Design Calculator and PadCAD, a computer program for cushion design, to assist packers with cushion design problems. For further information on either of these products, please contact the Extension Services Division at CCI..

Figure 1. The packing case used to transport demonstration equipment to a series of Art in Transit workshops. The case measures 80 cm x 40 cm x 42 cm and weighs 45 kg. Inset: The electronic data logger inside the packing case prior to shipment.

Table I
Probable Drop Heights

Note: For light packages shipped by parcel post, the drop height can be up to 3 m.