Es/FlightGear Newsletter December 2013: Difference between revisions

=== Updated aircraft ===

The JSBSim [[P-51D]] is undergoing some significant improvements. The most interesting of these is the fully functional K-14A lead computing gun sight. The screen shot below shows the gun sight in action with the aircraft rolled over and pulling about 5G. You can see that there are two reticles. The small cross in the upper center of the reflector glass is the center cross of the fixed reticle and it's sight line corresponds with where the guns would shoot in straight and level flight (IE. slightly below the bore line of the guns). The fixed reticle has been masked so that only the center cross is visible. The reticle consisting of a center dot and six surrounding diamonds is the reticle that is controlled by the gyroscope which is what gives this sight it's lead computing functionality. In the screen shot on the left, the gyro reticle is displaced a significant distance from the fixed reticle and this distance is known as the deflection. Note also that the tracers from the guns are converging near the center of the gyro reticle giving an indication of how effective the new gun sight is when doing deflection shots.

The screen shot on the right is of a ground attack mission using HVAR rockets. In this case the gyro reticle is turned off and the fixed reticle is unmasked. You can see the center cross along with the 70 mil outer circle and the so called rocket ladder in the lower center of the outer circle. This attack missed the target high and to the right mostly because I was distracted by taking the screen shot. But you can see that the flight path traced out by the rockets smoke is right where they should have been relative to the rocket ladder.  

gunsight1.png|Screen shot of the K-14A in action showing the gyroscopic reticle rolled over pulling G. Note how the tracers are converging near the center of the gyro reticle. In addition, the fixed reticle is masked and only the center cross is visible. The fixed reticle center cross is the bore sight line.

rocketladder.png|Screen of a rocket attack on a fishing boat. The reticle being used is the fixed reticle with the 70 mil circle and the rocket ladder unmasked.

The following screen shot on the left is a ground view of the aircraft with the new drop tanks, bomb racks and propeller. In addition you can see the back of the gun sight in the cockpit. The pink area on the back of the gun sight is the silica gel pack that keeps the internals of the gun sight dry.

tanks&prop.png|Screen shot showing new droop tanks, bomb racks, propeller and part of the K-14A gun sight.

Rockets.png|The new HVAR rockets and the new rocket mounts.

The bomb ranks and rocket wing mounts were modeled using the factory blue prints and are accurate to within perhaps 0.1mm. The propeller and drop tanks were modeled based on published measurements and have similar levels of accuracy. The gun sight 3D models are based on drawings and dimensions from the USAAF K-14A maintenance manual.

There are other improvements to the FDM and other areas that have been pushed to fgdata. To try out the new features you will need the Aircraft/p51d and Aircraft/Instruments-3d/computing-gun-sights directories. I tested these updates with FG 2.12.1 but it should be OK with any version from 2.4 on.  

fgdata also has the new check list functionality that was setup by Stuart Buchanan. I made some additions to the check lists to reflect changes in the FDM that affected the start up procedure. From that experience I know that Stuart spent a significant amount of time getting this in place. Thank you Stuart.

The plan going forward is to continue to improve the external 3D model based on the factory blue prints. So over the next few months you can expect to see things get even better.

Please feel free to give this a try and provide constructive feedback on the FlightGear forum.