ⓘ Rules of thumb ..

1 in 60 rule

In air navigation, the 1 in 60 rule is a rule of thumb which states that if a pilot has travelled sixty miles then an error in track of one mile is approximately a 1° error in heading, and proportionately more for larger errors. The rule is used by single pilots with many other tasks to perform, often in a basic aircraft without the aid of an autopilot, who need a simple process that can be performed in their heads. This rule is also used by air traffic controllers to quickly determine how much to turn an aircraft for separation purposes. The rule is based on the small-angle approximation, ...

1: 5: 200

In the construction industry, the 1:5:200 rule is a rule of thumb that states that: If the initial construction costs of a building is 1, then its maintenance and operating costs over the years is 5, and the business operating costs salary of people working in that building is 200.

18-electron rule

The 18-electron rule is a rule used primarily for predicting and rationalizing formulas for stable metal complexes, especially organometallic compounds. The rule is based on the fact that the valence shells of transition metals consist of nine valence orbitals, which collectively can accommodate 18 electrons as either bonding or nonbonding electron pairs. This means that the combination of these nine atomic orbitals with ligand orbitals creates nine molecular orbitals that are either metal-ligand bonding or non-bonding. When a metal complex has 18 valence electrons, it is said to have achi ...

68–95–99.7 rule

In statistics, the 68–95–99.7 rule, also known as the empirical rule, is a shorthand used to remember the percentage of values that lie within a band around the mean in a normal distribution with a width of two, four and six standard deviations, respectively; more accurately, 68.27%, 95.45% and 99.73% of the values lie within one, two and three standard deviations of the mean, respectively. In mathematical notation, these facts can be expressed as follows, where Χ is an observation from a normally distributed random variable, μ is the mean of the distribution, and σ is its standard deviati ...

Augustine's laws

Augustines laws were a series of tongue in cheek aphorisms put forth by Norman Ralph Augustine, an American aerospace businessman who served as Under Secretary of the Army from 1975 to 1977. In 1984 he published his laws. The book and several of the laws were the topic of an article in Sound and Vibration magazine in March 2012.