Terms and Definitions

Actual

Actual data is the same as measured data. It is the real values as derived by the measuring system.

Airfoil

An object roughly shaped like a fan blade. It has a curved geometry which when drawn through air, creates lift on one side of the blade. This moves air, which can be directed for thrust, compression, or other purposes.

Axial

Typically describes a direction parallel to the direction of airflow.

Axis

A straight line about which a body or a geometric figure rotates or may be supposed to rotate.

Bestfit

The translation and rotation of an actual spline versus a nominal spline to effectively make the two match each other as much as possible.

Bit Logic

Uses values for each parameter that added up specify an option. If you want to turn options 1, 2, and 4 on, then add 1+2+8. The sequence for bit logic is: 1, 2, 4, 8, 16, 32, 64, 128, etc...

BladeRunner

The BladeRunner airfoil measurement software manages the execution of your PC-DMIS Blade measurement routine in PC-DMIS. This measurement routine should be installed with the PC-DMIS Blade package in PC-DMIS installations. For proper operation of the Blade Turnkey System, see the BladeRunner documentation.

BladeRunner automatically creates a report file (*.rpt) that passes to the PC-DMIS Blade Analysis tool when the execution of the measurement routine is complete.

Camber

The "curl" of a blade. If the concave side of a blade section is laid on a flat surface, the more area under the blade, the more camber it has.

Chord Line

Most often: A line between the nose and tail point.

Also: A line that is tangential to the concave side of a blade section.

CONCAVE

REPORT Method

The CONCAVE side of the airfoil is used in the calculation (typically, an arc intersection with the spline).

CONVEX and CONCAVE tell which side to use for the LE_DIST, LE_TE, and STACK methods.

This method is available for the following calculations:

Contour

An outline, especially of a curving or irregular figure. Also, the line representing this outline.

Convex

The side of an airfoil that curves outward, or rocks when placed on a flat surface.

Datum

A reference or starting point.

A place that is referenced as the "zero" point for all other calculations.

A coordinate systems origin point.

Inscribed

The object is internal to a set of data. None of the data is contained within the object; the object is fully contained in the data.

Iteration

The act of repeating a procedure whose inputs are the outputs of the previous run of the procedure. This refines the results.

Leading Edge

The leading edge of an airfoil is the edge that cuts or hits the air the airfoil passes through. The leading edge is the opposite of the trailing edge.

Least Squares

A type of mathematical minimization that attempts to reduce the square root of the sum of the squares of the deviations. It is the most common type of best fit in metrology.

Nose Point

The nose point of a section is a point where the MCL pierces the leading edge.

NOSETAIL

REFERENCE Method

The chord length is reported as the shortest distance between the nose and tail points. NOSETAIL is also the default method for CHDANG; in this case, the angle of the line determined by the nose and tail points.

This method is available for the following calculations:

Section

Typically a planar slice through an airfoil at a given distance from the datum of the blade. It is often split into four sections called the convex and concave sides, and leading and trailing edges.

Spec Limit

A tolerance that is specified in absolute terms. An upper or lower limit of a value, as opposed to a nominal value plus or minus a value.

Spline

A curve that is described by mathematical functions. It is created through sets of points.

Stacking Line

A line that passes through all of the origin points of each section. (Actual or nominal). It is also referred to as the centerline of twist.

Stack Point

The origin point of a section (Actual or Nominal).

Tail Point

The tail point of a section is a point where the mean camber line (MCL) pierces the trailing edge.

Tolerance

A value, which when added or subtracted with a nominal value, gives the upper or lower limit (specification limit) for a certain characteristic.

Trailing Edge

The trailing edge of an airfoil is the opposite of the leading edge. It is the edge on the airfoil where the air that is separated by the airfoil meets. The tail point is a point on the trailing edge of the airfoil.