Yaw Critical Speed


Overview: Computes the Yaw - Critical Speed of Curve from Friction and Chord / Middle Ordinate or Radius information.


Entry into Module:


This module of the program is normally entered by clicking on the REC-TEC block in the upper left of the REC-TEC Window causing the drop-down menu to appear. Place the cursor on the Yaw Critical Speed block and click on Yaw Critical Speed on the sub-menu to initiate this module.


Under certain circumstances, the user may choose to use the Files block instead of the drop-down menu approach. Selecting any file with a .YAW extension in the Dialog box accessed from either the Open Single File or Open Multiple Files block opens this module.


Selecting AutoLoad [ON] from either the Setup Menu or the AutoLoad Icon on the upper right side (third line) of the REC-TEC Window automatically loads the scenario that was on the screen when the module was closed, either individually, or when the program was closed. With AutoLoad [OFF] on the main REC-TEC Window, modules will start without loading a file.


Data Entry:


This module contains the following data entry blocks within the leftmost frame:


Critical Speed


             Radius Radius of Curve




             Chord Required with Middle Ordinate

             Middle Ordinate Required with Chord




             Mu Surface Friction




             Superelevation Tangent of Angle (Adjustment in direction of Striation Marks)

             Vehicle Track Optional


Entry of required information in the data boxes is sufficient to generate a solution and causes output information to appear in the Output frame. As the input data is changed, the output data is automatically updated without the need to tell the program to update the output.




The output from this module consists of the repeated input variables plus all of the unknowns that were not entered into the left Input frame expressed in the primary and secondary configurations.


             Chord: Chord as measured

             Middle Ordinate: Middle Ordinate as measured


             Vehicle Track: Optional


             Radius: Measured or computed

             Radius (Adj.): Radius adjusted for Vehicle Track

             Angle: Subtended Angle (Chord/Middle Ordinate)


             Mu: Surface Friction (Curve or along Critical Speed Scuff)

             Superelevation: Adjustment in direction of Striation Marks


             Friction Factor: Friction value for maneuver in direction of Striation Marks


             Rate: Rate of Friction Factor Acceleration (Primary)

             Rate: Rate of Friction Factor Acceleration (Secondary)


             Time (Sc): Time of Maneuver at Constant Speed

             Distance (Sc): Distance on Curve


             Speed: - Speed of Vault (at optimum/take-off angle - Primary)

             Speed: - Speed of Vault (at optimum/take-off angle - Secondary)




Several Command Buttons appear in a frame located at the lower right corner of the module Window. The Command Buttons allow the user to engage options including the option to Open and Save the data required to generate the scenario shown on the screen at the time the file was saved.


             Open .YAW File Calls up a Dialog box, which Opens any pre-existing .YAW file and displays the output results.


             Save .YAW File Calls up a Dialog box, which Saves data on the screen to files with any user-selectable filenames. This is independent of the automatic saving as LastFile.YAW of the data at the close of this module or the close of the program.


             Formulae Opens a word processor (set by the user in Setup) with a file showing the basic formulae used in this module of the program. While the user may add to or modify the information in this file, it does not change the formulae imbedded into the program.


             Formulae* Toggles a frame displaying the formulae for computing the unknowns in this module. In addition to the basic formulae, the frame shows intermediate steps with the actual input data shown in the computation.


             Graphics The display shows the Circle and Chord/Middle Ordinate with the Angle. [Esc] to Exit


             N This button toggles a graphical number pad on the screen that can be used to enter data into the input boxes without using your keyboard number pad. This may be useful for presentations as data entry can be accomplished using a wired/wireless mouse.


             Tables / FDA Calls up a frame that permits the user to input the minimum and maximum values for selected input variables along with the interval for Iteration. If Finite Difference Analysis (FDA) is selected, the resulting analysis computes the uncertainty level for the specified range of the input variables.


For a more in-depth description of Finite Difference Analysis, see the Finite Difference Analysis Section of this Manual Press [F2] from any Active module of the program.