Murphy's Law was first cast by Joe Chase, Editor of the Flight Safety Foundation's mechanics Bulletin in early 1955. It grew out of the pre- cept developed and published by the foundation in its design notes that "Procedures for adequate maintenance and operation practices est- ablished by designers should be consistent with average human effort, ability and attitude". The law coined reads: "If an aircraft part can be installed incorrectly, someone will install it that way." Corollaries to Murphy's Law have sprung from all over the industry. Here we present some examples: - If anything can go wrong, it will. - It is impossible to make anything foolproof because fools are so ingenious. - An experiment may be considered succesful if no more than 50 % of the data obtained must be discarded to get a result which satisfies the theory to be proved. - No experiment is a complete failure. It can always serve as a bad example. - When all else fails, read the directions. - Specified environmental conditions will always be exceeded. - Any error that can creep in, will. It will be in the direction that will do the most damage. - All constants are variable. - In a complex calculation, one factor from the numerator will always move into the denominator. - In any given computation, the figure that is most obviously correct will be the source of error. - In any given miscalculation, the fault will never be placed if more than one person is involved. - Dimensions will always be expressed in the least usable terms. - Interchangeable parts won't. - Any wire or tube cut to length will be too short. - Identical units tested under identical conditions will not be identi- cal in the field. - Availability of a part is inversely proportional to the need for the part. - The easiest way to find something you lost is to buy a replacement. - Don't force it. Get a bigger hammer. - If you don't understand a particular word in a technical article, ignore it. The text usually makes perfect sence without it. (With the exception of Maskinelement books, of course.) - Make three consecutive correct guesses and you will establish your- self as an expert. - A man who can smile when things go wrong has thought of someone he can blame it on. - A dropped tool will land where it can do the most damage. (Also known as the law of selective gravitation.) - The accessibility of a part which falls from the workbench varies directly with the size of the part and inversely with the import- ance of the part in completing the job. - Tolerance will accumulate unidirectionally toward maximum diffi- culty of assembly. - Hermetic seals will leak. - After an instrument has been fully assembled, extra components will be found on the bench. - After the last 16 mounting screws are removed from an access plate, it will be discovered that the wrong access plate has been removed. - Any safety factor set as a result of practical experience will al- ways be exceeded. - Components that must not and cannot be assembled improperly will be. - The probability of a dimension being omitted from a drawing is dir- ectly proportional to its importance. - The most logical way to assemble components will be the wrong way. - The more innocuous a design change appears, the further its influence will extend. - The necessity for making a major design change increases as the job nears completion. - A part will be made exactly as specified in a drawing only when the drawing has an error. - After all, there is a Murphy in every crowd. Finagle's constant: That quantity which when: multiplied by, divided into, added to, subtracted from, or taken to the power of: the answer you have given the answer you need.