Polar Exchange Format (PEF)


Purpose of PEF-Files

The Polar Exchange Format (PEF) has been designed about 20 years ago as a means to exchange airfoil data between different applications. While it was not intended primarily as an efficient storage or data base format, it can be used to store and access airfoil and aircraft polars from performance calculation and flight mechanics computer programs. The data is organized in polars, which contain values for a range of angle of attack values. A PEF file can contain several polars, e.g. for different Reynolds numbers, which may be grouped in data sets, e.g. from different sources like wind tunnel and calculation. One PEF file usually contains data for one airfoil geometry. (PEF files can be imported and exported e.g. by the commercial software WINPROF from Wiechers, Puchheim, Germany).

Note: Today, you should use the XML format for this purpose. PEF is only described here for downward compatibility.

Structure of a PEF-File

A PEF file is written in a simple, but case dependent ASCII format. It contains several blocks of information, whose sequence is free. Each block is identified by a heading, which is enclosed in square brackets ([]). Inside each block several key-value pairs are specified by the key word, followed by an equal sign, followed by the value(s). The sequence of these key-value pairs is arbitrary, so that readers should seek from the start of a block to locate a key. Comment lines, with a ';' character in the first column, can be inserted.

Based on this block structure, a PEF reader can lookup any desired information from the file, when he has read the [Airfoil] block and the [Setn] blocks described below.

Description1=briefly identifies the airfoil or the geometry {MANDATORY}
NumberSets=the number of data sets to follow {MANDATORY}

[Setn] n: number of data set, counting from '1'
Origin=source of this data set
Description1=description of the data set
NumberPolars=number of polars in this data set {MANDATORY}

[Setn-Polarm] n: number of data set, m: number of polar, counting from '1'
ReynoldsNumber=the Reynolds number of the first polar
MachNumber=the Mach number of the first polar
Description1=may contain a description of this specific polar
NumberPoints=number of data points in this polar {MANDATORY}
Values=Alpha Cl Cd Cm xtu xtl (recommended default sequence of values)
Value01= the values for the first data point {MANDATORY}
Value02= the values for the second data point {MANDATORY}
Value...= the values for the next data points {MANDATORY}

Sample Readers and Tools

This PEFParser can be compiled with a C-compiler.Download a sample C-source file (size: 5 kB), which parses a PEF file.

This PEFParser can be compiled with a FORTRAN-77-compiler.
Download a sample FORTRAN-source file (size: 12 kB), which parses a PEF file.

This converter can be compiled with a C-compiler. It converts .drg polar files from the UIUC wind tunnel campaign to PEF files.
Download a self extracting LZH archive (size: 37 kB), including C source and an executable for Microsoft Windows 3.1.


V 2.1

This utility program for Windows 9x and Windows NT/2000/XP has been developed from PEFbrowser. It can read, display, print and convert various airfoil polar file formats. It reads XML, PEF, POL and DRG files, writes XML, PEF, POL and EPP files and can be used to sort and combine different polar sets. The program has been written in VisualBasic 6.0. The program can now also handle UNIX style PEF files, with lines terminated by a line feed character (ASCII 10) only, instead of the DOS/Windows CR/LF (ASCII 10/13) pair.
Download the following Microsoft Installer files and right click or run the .msi file to install.

polarbrowser.msi (1696 kB)

File Format

PEF see this page
POL XFoil 5.4 polars
DRG UIUC and Princeton experiments
EPP Eppler input file (export only, to plot polars with Epplers airfoil program)


Modellwindkanal University of Stuttgart (of local interest only)


Extensible Markup Language (this should be used as a standard format)

Example of a PEF-File

Description1=MH 60

Origin=Calculation: X-Foil
Description1=Part of 'Profile für Nurflügelmodelle'

Description1=Copyright © 1995-1996 Martin Hepperle
Values=Alpha Cl Cd Cm xtu xtl
Value01= -3.50 -0.382 0.02217 -0.0036 0.8026 0.0534
Value02= -3.00 -0.312 0.01917 -0.0060 0.8001 0.2709
Value03= -1.50 0.118 0.01675 -0.0488 0.8040 0.8507
Origin=Experiment, Stuttgart
Description1=Part of 'Profile für Nurflügelmodelle'


Last modification of this page: 21.05.18

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