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Adaptation Process

1.   UAVN uses the term 'Adaptation' to describe the process by which the autopilot gains are tuned to work on the Customer's UAV so that it can fly safely within the flight envelope. During the process a specific gains file is generated.

2.   Gains File.   The gains file is valid only for a given aircraft configuration. If the configuration changes significantly, then a different gains file must be generated and used. Examples include:

  • Different flight envelope (e.g. higher, faster).

  • Different engine.

  • Aerodynamic changes (e.g. control surfaces, different blades, other additions).

  • MTOW.

  • Changes in inertia or Centre of Gravity.

  • Different payload causing variation in the physical /aerodynamic characteristics.

3.   If necessary, during the Adaptation process different gains files can be generated for different configurations.

4.   The client will be required to sign an 'Aircraft Configuration and Gains File Compatibility' report which UAV Navigation Flight Control engineers will prepare after Adaptation. This ensures that only an approved aircraft configuration is flown with a given gains file.

5.   IMPORTANT! Attempting to fly a UAV with the wrong gains or config files may result in unexpected behaviour and/or loss of the UAV.


6.  UAVN employs two approaches to Adaptation:

  • Simple Adaptation: suitable for UAVs where the full physical/aerodynamic characteristics (including stability derivatives) are not available and flight trials can be conducted safely during development of the config files.

  • Complex Adaptation: geared to more complex and high-value projects. A complete set of gains and config files must therefore be developed by a deep study of the platform and advanced simulation techniques. This process leads to a more accurate gains file.





Approx Duration


Working from the physical characteristics of the platform, UAVN's engineers derive a basic configuration preset for the autopilot based on a reduced set of calculations, drawing on experience with similar aircraft which have been adapted before. This process consists of modelling and preparation in the office.

1 day to 1 week


With the basic configuration, UAVN then conducts initial flight tests with the assistance of an External Pilot (aka 'UAV Remote Pilot'). The aim is to tune the control loops in real time, including SAS and CAS, and Guidance loops.

  • The inner loops include:

    • Pitch/Roll control with pitch/roll and pitch/roll rate feedback.

    • Yaw damper.

    • Turn coordination with lateral acceleration.

  • The outer loops include:

    • Altitude and airspeed control by energy.

    • Stall protection mode where the plane maintains airspeed using pitch.

    • Roll steering. Cross-track and cross-track velocity feeds roll command.

  • For fixed wing runway take-off UAVs, side acceleration with cross-track and cross-track velocity is fed back during the take-off run.

  • The flare maneouvre is an exponential, with a user defined time constant. We use either DGPS, radar altimeter or laser altimeter.

  • By commanding pulses and doublets the engineers are able to excite the UAV closed loop dynamic modes. Gains settings are changed in real time and in a couple of flights it is usually possible to obtain a reasonable set of gains. Step 2 may be achieved in a little as a day (for simple platforms), or longer for more complex platforms.

1 to 2 weeks


Back in the office,  UAV Navigation engineers will create a report describing the adjustments done during the adaptation process.

1 to 2 days





Approx Duration


Before going to fly, a complete 6DOF model is derived from information about the platform obtained directly from the manufacturer of the aircraft (NB: UAVN treats the aircraft as a rigid body only - aeroelastic effects are not taken into account).

2 to 4 weeks


(optional) The platform's performance may be measured during a 'Passenger Flight', whereby the autopilot is flown passively within the aircraft, recording all flight parameters to a log file in a datalogger.

1 week


Modelling and simulator refinement.

2 weeks


Once a comprehensive 6DOF model has been developed, actual flight trials can take place with the assurance that the autopilot will be able to control the aircraft safely from take-off. If necessary, minor changes may be made to the gains settings - although this is usually not necessary.

3 sessions of 1 week each