05 April 2024

Dear Fighter Pilots, Partners and Friends,

The initial set of answers from the 15th Anniversary Q&A, presented by Matt “Wags” Wagner is now available for your enjoyment here! We hope that this video gives you a better understanding of our plans and goals regarding game performance in 2024 and beyond. Answers on additional topics will release steadily over the coming months. Thanks again to all of you who took the time to participate, we are truly grateful.

We are thrilled to share our latest development on the DCS: F-16C Viper’s complex INS and GPS improvements. It is important to note that not all features have been added and more enhancements and bug fixes will be coming soon. 

Fox3 Managed Solutions group is running a DCS tournament in support of the K9sforWarriors charity. We encourage you to participate in the event as all proceeds will go to the cause. Please check out the details below.

Thank you for your passion and support.

Yours sincerely,

Eagle Dynamics

15th Anniversary Q&A Videos



We hope that our approach to packaging your questions works well and that you will enjoy Matt’s performance. Over the coming months we will be providing further videos covering your 2000+ questions. As you can imagine, quite a few of the issues raised have similarities and hence we have categorised them in subject matter blocks published on Youtube and on our Forums. Enjoy!

Check out the first video on Performance questions.

Written and additional answers can be found on the Forum here. Thank you for your patience and all your support!

F-16C Viper

Development Report

F-16C Viper

F-16C INS+GPS System Overview

The navigation system on the DCS: F-16C Viper is a complicated mixture of technical solutions that are intended to supply the avionics with coordinates, velocity, and angles,  that are characterised by precision, availability, integrity and autonomy. This is achieved by the cooperative work of the Inertial Navigation System (INS) and Global Positioning System (GPS) whose navigation inputs are processed through a Kalman filter in the Modular Mission Computer (MMC). Let’s discuss each of the components in detail.


The Inertial Navigation System is an autonomous device that performs dead reckoning of aircraft coordinates by measuring the accelerations and then integrating them twice whilst taking into account the aircraft’s orientation in space. The latter is obtained from the F-16 ring-laser gyros. This type of INS is termed “strapdown” as there are no rotating parts. Basically, INS consists of three accelerometers, each for one orthogonal axis, and three  gyros.

The main features of INS improvements are:

  • Autonomy, as it doesn’t require any external signals to do dead reckoning.
  • Stability in a short period of time (5-10 minutes).
  • Noticeable error accumulation over longer periods of time based on the physics of dead reckoning. Together with the integration of accelerations (to update speed) and integration of position (to update coordinates), the small errors at the level of accelerations that are introduced by accelerometer noises and imperfect alignment are integrated twice as well. 

Furthermore, the larger those errors are, the faster they accumulate due to the so-called integral correction of INS, which updates the local Earth gravitational force vector with the coordinates and adds them into the relative angles of the G vector.

Another distinctive feature of INS is the Schuler Oscillation with a period of 84.4 minutes. Due to the integral correction algorithm mentioned above, the INS behaves like a pendulum. In ideal circumstances, it stays in equilibrium while the aircraft moves along the Earth. When coordinate errors appear, it displaces the pendulum from the resting point and it starts oscillating. The larger the errors are, the larger the amplitude of the introduced oscillations. That’s why one may notice that INS errors get smaller at a rate of 84.4 minutes once airborne.


Global positioning system measures the aircraft position by measuring the signal propagation delay from GPS satellites to the receiver. Satellite orbits are precisely known, the exact positions of the satellites are computed according to an almanack that is transmitted in the same GPS radio signals. That’s why GPS needs a couple of minutes after the cold to start obtaining the almanack. The moments of the signal transmission are also known and are defined by a very precise atomic clock on board the satellite. Thus, in an ideal case, if the GPS signals are propagated through space with the constant speed of light, as they do in a vacuum, the receiver could precisely determine its position by intersecting the surfaces of equidistant radio signal delays from the satellites. You may think of it as spheres with centres located at the satellite’s positions, although it’s a bit more complicated in real life. However, there are two significant factors that prevent us from obtaining the ideal point of the surface intersections; the ionospheric delay and multipath. Both add unknown time to the actual signal propagation time. Multipath happens when the receiver is placed relatively near the ground and the signal may be reflected from ground objects that results in the signal's edges degrading; this is similar to an echo in the mountains where it’s too hard to tell one word from another. When such delays are unexpectedly added by the receiver, the precise navigation solution gets lost and the output

coordinate gets noisy. That’s where military GPS signals help to get a better signal resolution by the use of so-called P-codes, and the usage of dual frequency helps to eliminate the unknown ionospheric delay. 

Integrated solution. Kalman filtering

To summarise the above: we have two navigation systems, both of which have flaws: INS accumulates errors over time, GPS is noisy and prone to interference due to natural factors like multipath and ionospheric delay and to enemy jamming and spoofing. Here is the good news! There is a way to avoid these flaws with the Kalman filter. It takes GPS and INS coordinates together with speeds as its input. The Kalman filter is a great algorithm that is able to get the maximum precision even out of measurements far from ideal, and it takes the best aspects from both systems: the stability and autonomy of INS and the precision of GPS to obtain an integrated navigation solution that is both stable and precise.

Furthermore, the Kalman filter knows, in terms of mathematical equations, the dynamic properties of the aircraft that is moving through space. If the aircraft is moving, it predicts where the aircraft will be on the next filter step. That’s why it is called recursive and the filter won’t let erroneous GPS signals decrease the precision of the output navigation solution. Moreover, it is able to dynamically change its measurements vs. prediction weights to adjust to a degraded navigation precision of any input.

Fox3 Solutions

Charity Tournament

This April, Fox3 is thrilled to announce a heart-pounding, adrenaline-fueled DCS tournament that's not just about showcasing your skills, but also about rallying our incredible community to a great cause; supporting the heroes at K9sForWarriors. Learn more about the K9sForWarriors mission.

Mark Your Calendars! The battlefield opens from the 19th of April to the 21st, 2024. Prepare for three days of intense aerial challenges, camaraderie, and epic battles that will test your mettle. Please note that this is a charity event with paid attendance and fantastic prizes: Fox3's Ultimate DCS Skills Showdown is Here!

Thank you again for your passion and support,

Yours sincerely,

Eagle Dynamics