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HOLD for the Classic

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made a little HOLD script for the classic.


Still a bit rough around the edges, but it works. Teardrops and all.

All courses are corrected for wind and magnetic variation, but it has not been tested in very extreme situations. A flight with 80kn wind worked.

Things that influence the size (and shape) of the pattern, bank angle, height (TAS!), speed, wind. (TAS influences the turning radius, not IAS)
Things that may confuse my program, large changes in aircraft configuration during holding. Its only a little smart.


PPOS is a hold pattern at present position, a simplified version of the PPOS of a Boeing FMS. Enter the desired inbound course, leg lenght, speed and altitude, and click HOLD.
The aircraft will enter a holding pattern and will adjust speed and altitude. When the hold is active, you can adjust speed and altitude if needed, the program will anticipate the changes.
There is no luxury option like in the real aircraft to enter quadrants and arm an exit. If you are cleared to leave the holding, to have to find the best position to leave the pattern and continue with LNAV / VNAV. The PPOS hold is terminated when you click the button, or when you deselect HDG SEL. The program anticipates wind, but with strong winds the pattern will start to look pear shaped, because turn radius will be influenced by wind. Other factors that will influence the hold pattern are speed and altitude. A speed of about 220kn is quite good for a holding. The bank angle the program uses is 30deg. If you change the bank angle during the hold, the program will adapt. Small bank angles will create a large pattern however. If you choose a inbound course that is very much different from the course the pattern will look a bit odd in the beginning. Best is to choose a course with as much upwind as possible.


This will allow you to search for navaid in your area, and use this as the FIX for the holding pattern. If you have the navigraph files (you dont need them for this option), an attempt is made to link a hold record with the navaid you chose. Beware to check the result of your search, especially the distance, this may give an idea if you found the right one. Some searches may find navaids very far from your location. HOLDING AT searches for waypoints,VOR and NDB navaids, near you. When you are satisfied with your choice, click hold, and the aircraft flies to the FIX and enters the pattern according the general rules. This may look a bit strange at first, but its just a teardrop or parallel entry. It can do nice teardrops :)


This uses the Navigraph data to find a HOLDING, and tries to link this to a waypoint or navaid. This works well in general, especially if you use the Navigraph (moving) maps / charts with it. Otherwise it works as HOLDING AT, some data from HOLD records may be added for you to accept or override. Some holdings you can find by their name, and some by their FIX name. Beware, the searches may find results thousands of miles form your location. And yes, it will try to fly there :)

From the test range:





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That's pretty cool.  For the record, I am finally back to working in the FMS, including adding the holds.  I'm in the process of porting over to the ARINC 424 / XP1100 nav-data format, which should make things go much smoother for holds...accurate routes / entry....just about everything route related.  But thanks for this script...it will be a bit before the holds features get distributed!


Edited by tkyler
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