Monthly Archives: February 2018

Prepar3D V4 Nephi 100 Km triangle glider speed challenge

 

This flight adventure was my attempt, using Prepar3D V4, to emulate a real-world gliding speed challenge.  My P3D flight was inspired by one of Bruno Vassel’s excellent YouTube videos (see links below).  In that video, Bruno broke the Utah 100 km triangle speed record of 95.2 mph set back in 2003 by flying an average 100.23 mph (162 km/h) in a Schleicher ASW 27b glider on the 5th August 2017 at Nephi, Utah (u14).

Link to Bruno’s speed challenge flight video:  https://youtu.be/pIsUk0c8Sck
Link to Bruno’s YouTube channel (highly recommended):  http://phoebus.vassel.com

My YouTube flight:

To emulate Bruno Vassel’s real-world speed challenge in a somewhat convincing way, I undertook the following actions and configuration settings:

Task replication: I replicated Bruno’s flight task by extracting the waypoint data from the IGC logfile captured on Bruno’s flight, and then converted the data to an FSX flight plan using a Python script that I had developed.

This is the resultant flight plan in Little Navmap:

Flight Plan

 

Choice of glider model: The choice of glider model was easy.  I used the ASW27b model from Wolfgang Piper’s collection of freeware gliders for FSX and P3D. This matches up nicely with Bruno’s glider, although there are likely some differences due to limitations in the simulator flight modelling.

Link to Wolfgang Pipers website: https://www.fsglider.de/

 

Payload and ballast settings: To maximise my cruise speed performance, I set the payload and ballast in P3D to give the maximum take-off payload of 500 kg.  I also set the pilot weight and ballast to bring the centre of gravity slightly forward of default to improve high speed trimming as shown in the following snapshot:

Payload

 

Weather settings: To approximate the weather conditions of Bruno’s flight, I initially explored the possibility of using Active Sky 2016 (AS16) to inject historical weather directly into the sim. The problem with that approach was that the AS16 add-on chose stratus clouds when the historical meta data left the lower cloud layer type unspecified and the soaring environment add-on (CumulusX!) will not produce thermals when stratus clouds are present in the lowest cloud layer.

To get around that problem, I tried using a snapshot of the historical weather in manual mode and then changed the cloud type to cumulus but then I ran into other problems.  Firstly the upper level wind layers had enough wind shear to make thermalling in the simulator almost impossible. Also AS16 seemed to generate too many clouds for the specified cloud coverage, which did not look anything like the real-world conditions seen in Bruno’s video. Moreover, the extra clouds exacerbated performance issues that I have been experiencing lately in my simulator.

In the end, I decided to use the historical data from AS16 as a guide for manually creating a weather scenario using the advanced weather settings in Prepar3D. I tried to copy the AS16 reported weather conditions as closely as possible but I did modify the upper wind layers a little to reduce the wind shear to more modest levels.  I also reduced the reported visibility to better match the cloud haze visible in Bruno’s video because this visibility issue had not been reported in the AS16 historical weather data. Plus I elliminated the lower level cloud layer completely, relying instead on clouds generated by the CumulusX! add-on in ‘Unblue’ mode. I added a high-level cirrus cloud layer for purely cosmetic reasons.

weather01

weather02

weather03

weather04weather05weather06weather07

 

Soaring environment configuration: To create a convincing soaring environment (thermals) consistent with the conditions evident in Bruno’s flight video, I configured CumulusX! as shown in the following snapshot. Note also, that I was using ‘blue’ thermals (i.e. no cumulus cloud layer in P3D) and I had the ’Unblue’ option in the CumulusX! Help menu ticked. This was done, partly because my P3D installation did not seem to represent a 2/8 or less cloud coverage accurately, and also because reducing the cloud coverage helped with some performance issues that I have been experiencing lately.  Unfortunately, the CumulusX! cloud textures looked awful.

Link to CumulusX! competition soaring environment add-on:

http://luerkens.homepage.t-online.de/peter/

 

CONCLUSIONS

While I fell well short of the Utah 100 km speed record (only 95.88 mph as against 100.23 mph) in my attempt, I nevertheless enjoyed this speed challenge immensely.  I felt pressured all the way around the set course, trying to balance minimum arrival height against the need to achieve a task average speed greater than 100 mph.  I am convinced that a speed challenge, such as this, can be equally entertaining as any race against other gliders in a multiplayer event.

 

TASK RESULTS AND FLIGHT PATH

My task result in SeeYou:

Result

My flight path in Little Navmap:

Flight path