The following analysis relates to the airplane lavatory door-closing technique experiment, as conducted by the research team of Chang & Chapman, on Northwest flight 341 from Detroit to San Francisco, October 4th, 2000.


Hypothesis/Experiment Premise:


The data collected in this experiment is intended to be an objective look at human behavior as it is expressed in the act of operating a typical spring-loaded, airplane lavatory door-latch mechanism, of the type found in Boeing aircraft; in this case, the Boeing 757. The door-latch is operated by twisting a semi-recessed, horizontal metal bar approximately 75 degrees CCW; allowing a spring-loaded striker-tab to clear a striker-plate retaining cut-away, mounted in the door-jam. The door is then free to be pulled toward the operator upon entering and conversely, pushed outward in the case of departure from the lavatory. It is an assumption that the design intention in door operation was such that the only force required for operation, is that required to twist the horizontal bar, approximately 10 foot-pounds. Therefore the "proper technique", if there was one described (not in evidence) would include only the movement of the described bar (the door handle) and not include any pushing or forcing of the door into the door-jam. The design does have accommodation for the operator forcing the door closed without actually operating the door-latch mechanism, however this feature is considered by the experimenters to be a back-up default, incorporated to accommodate emergency or operators who care not to operate the latch mechanism. These assumptions do contribute to the test's relevance to the extent that although the longevity and integrity of the door latch mechanism is effected by the techniques employed by its operators, it is a secondary concern - superseded by the primary, the illustration of the degree to which individuals impose their auditory pollution upon their neighbors and the degree to which such individuals are aware of such imposition.


No other personal attributes were considered in the test, such as age, height, weight, mobility, etc. The length of time spent in the lavatory was not noted in the test, nor was any judgment made as to the nature of the activities inside the lavatory.


Test Parameters:


The operators of the lavatory door-latch mechanism were unnecessarily categorized as either Male or Female, Caucasian, Asian, Latin, or African-American. It is fair to say that the ethnic demographic is inherently atypical as a microcosm of American society at large, due to the economic pre-dispositions of airborne consumers. The test was conducted anonymously; the experimenters, their employees and their family members were excluded from the experiment. There was no compensation for which passengers chose the test lavatory and which passengers opted for a lavatory elsewhere in the airplane. Nor was there an experimental system for dealing with the post-meal lavatory rush, which resulted in a number of botched operations or forced individuals to abort their attempts at operating the lavatory door-latch mechanism. There also was no compensation for individuals who employed the lavatory features without selecting the occupied position of the lavatory status indication system, which in at least one case, caused a perhaps erroneous entry test state when another individual attempted to enter, assuming the unit vacant.


The operators were given a notation for primarily their technique in closely the lavatory door via the door-latch mechanism upon the conclusion of their lavatory visits, with a secondary influential point or minus point for their technique in operating the device upon entry. This secondary tabulation was used only to push an individual's overall score off a threshold between ratings, in the event of ambiguity in the minds of the two judges or if the indication on a Sound Pressure Level meter was on the border between levels. The secondary rating system was used in less than 5% of the test cases.


The operators' technique was rated (X) for Flawless or Perfect (essentially silent) operation.


The operators' technique was rated (P) for Push - generally described as the approach wherein the door is moved to the point which the Striker-tab rests on the exterior of the striker-plate, and then applying pressure on the door itself until the resistance of the striker-tab spring is overcome and the door moves into and hits the jam. This approach was considered to produce a sound pressure amplitude to 75dBspl.


The operators' technique was rated (S) for Slam - generally described as the approach wherein enough force is applied to the open door itself to a ramp velocity ensuring that when it contacts the door-jam and the striker plate exterior, full door closure and final latch status is guaranteed. This approach was considered to produce a sound pressure amplitude beyond 75dBspl.




During the course of the 5 hour flight, 39 test cases were reported, of these 36 were unique users and 33 considered valid. It is interesting to note that the repeat operators were entirely consistent in their technique. 6 cases were considered invalid, abortions (N/C) due to queue, rush or isle blockage, etc.


11 Slams (S) - 5 Caucasian males, 6 Caucasian females

17 Pushes (P) - 6 Caucasian males, 5 Caucasian females,

        2 Asian males, 2 Asian females, 2 Latin females

5 Flawless (X) - 2 African American male, 1 Asian male,

        1 Caucasian male, 1 Caucasian female

6 Abortions (N/C)


It is interesting to note that no person of color slammed the door, but the experiment design is not such that one could draw accurately from this result. Also, it is interesting that the individual seated closest to the lavatory in test, slammed the door upon exiting.






g. chapman 10/2000