Home Engineering Small Unmanned Fixed-Wing Aircraft Design. A Practical Approach
Flight Control Software
Flight Control Software is split into that on the airframe and that on the GCS. It will consist of firmware that is rarely changed and is largely independent of the aircraft, and operator-set software that may be readily edited and is aircraft-specific. Maintenance of firmware mainly consists of ensuring that the set in use is up to date as confirmed from the manufacturers’ Web sites. If such software is updated, great caution should be taken when next flying the aircraft, just in case some unexpected glitch or feature change has been introduced. For systems that are subject to regulatory approvals, such a change may well require a reapplication for permission to fly with suitable justification for the change and evidence that it has been suitably tested.
User-programmable software is generally configured into the GCS before the beginning of each flight session and uploaded to the airframe when the avionics are first powered up. Assuming that the links between the GCS and airframe are functioning as designed, maintenance essentially involves ensuring that the correct set of software is being used and that no unauthorized changes have been made to this since it was last used. An essential part of the first test flights of any new aircraft will be the adjustment of the pilot’s hand-held transmitter settings to match the characteristics of the airframe. A good deal of this will be carried out during ground tests, and a safety run through these setting will be needed before every flight to ensure that the main flight control surfaces and propulsion system behave as expected. It is good practice to then keep back-ups and records of these settings so that at the start of flying the transmitter software is in a known condition.
A similar set of parameters will also be need to be established for any autopilot fitted to the airframes. This will primarily involve the controller gain settings but also calibration of pitot tubes and the on-board magnetometer if fitted. Again, once a safe set of parameters has been established, these should be backed up and recorded so that known conditions are established before flying. In all cases, adjustments to transmitter or autopilot settings should be made only by experienced and authorized members of the flight team.
Maintenance Record Keeping
It will be clear from what has already been set out in this chapter that good record keeping is of vital importance to the safe operations of any UAS. This is just as important with regard to maintenance logs as it is to flight logs. The operating team simply has to be sure of the condition of the hardware and software in use to be able to have confidence in it. Such logs should be neat and tidy, readily to hand, and updated after each flight or at the very least after each flight day. Each UAS should have its own dedicated set of logs, and these should be backed up with paper hard copies that are available on the flying field.
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