Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2004. 220 leaves single printed pages ,preliminary pages i-xiv and numberd pages 1-188.Includes bibliography.list of figures and used a Hp Scanjet 8250 Scanner to pdf format (OCR), / ENGLISH ABSTRACT: This thesis describes the process followed to determine the short-term control and stability derivatives of an ASK-13 glider (ZS-GHB). The short-term control and stability derivatives are obtained by parameter estimation done using data recorded in flight. The algorithm used is the MMLE3 implementation of a maximum likelihood estimator. To collect the flight data sensors were installed in the ZS-GHB. Sensors measuring the control surface deflections, translation acceleration, angular rates and the dynamic and static pressure are needed to provide enough data for the estimation. To estimate accurate derivatives specific manoeuvres were flown by the pilot, to ensure that all the modes of the glider were stimulated. The results reveal that the control and stability derivatives estimated from the flight data are not very accurate but are still suitable to be used in simulating the glider's motion. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die proses wat gebruik is om die kort periode beheer en stabiliteit afgeleides van 'n ASK-13 sweeftuig vas te stel. Die kort periode beheer en stabiliteit afgeleides is verkry deur parameter afskatting op data wat gedurend vlugte van die sweeftuig opgeneem is. Die algoritme wat gebruik is om die parameters af te skat is die MMLE3 voorstelling van 'n maksimale moontlikheid afskatter. Om vlug data te versamel sensore moes in die sweeftuig geinstalleer word. Die sensore meet beheer oppervlak hoeke, versnellings, hoeksnellhede en die dinamies en statiese lugdruk om te verseker dat daar genoeg data is vir die afskatting. Om die afgeskatte parameters akkuraad te kry moet die loods spesefieke manoeuvres vlieg om seker te maak dat al die moduse van die sweeftuig is gestimuleer. Die resultate wat gelewer is 'n stel kort periode beheer en stabiliteit afgeleides wat nie akkuraad is nie, maar wat weI goed genoeg is or ie bewegings van die sweeftuig te simuleer.