Structural safety factor for small unmanned aircraft

소형 무인기 구조 안전계수

  • Received : 2017.04.28
  • Accepted : 2017.06.25
  • Published : 2017.06.30


Manned aircraft structural design is based on structural safety factor of 1.5, and this safety factor is equivalent to a probability of failure of between 10-2 and 10-3. The target failure probability of FARs is between 10-6 and 10-9 per flight according to aircraft type. NATO released STANAG 4703 to established the airworthiness requirements for small UAV which is less than 150kg. STANAG 4703 requires the Target Level of Safety according to MTOW. The requirements of failure probability for small UAV is between 10-4 and 10-5. In this paper, requirements of airworthiness certification for small UAV were investigated and the relationship of safety factors to the probability of structural failure is analyzed to reduce measure of safety factor and structural weight of unmanned aircraft.


Grant : 경량구조 및 구조안전성 향상기술 연구

Supported by : 기초기술연구회


  1. J. Lim, Y. Kim, B. Choi and J. Ko, "Analysis for unmanned aerial airthiness certification criteria," Journal of the korean society for aviation and aeronautics, Vol. 22, No. 4, 2014, pp. 65-74
  2. N. Lee, B. Jeon and Y. Chang, "Target level of safety analysis in airworthiness certification for military UAV," Journal of the korean society for aeronautical and space science, Vol. 41, No. 10, 2013, pp. 840-848
  3. F. R. Shanley, "Historical note on the 1.5 factor of safety for aircraft structures", Journal of the aerospace sciences, Vol. 29, No. 2 (1962), pp. 243-244
  4. FAR Part-25, Airworthiness standards: Transport category airplanes
  5. E. M. George and C. J. Schmid, " Factor of safety - USAF design practice " Techanical Report AFFDL-TR-78-8, April 1978
  6. Joint service specification guide, Aircraft structures, 2006
  7. AC 23.1309-1E, System safety analysis and assessment for PART 23 airplanes, 2011
  8. STANAG 4671, Unmanned aerial v ehicles airworthiness requirements, 2009
  9. STANAG 4703, Light Unmanned aircraft system airworthiness requirements, 2011
  10. M. N. George, "The aircraft structural factor of safety", North Atlantic Treaty Organization, Report 154, 1957
  11. I. Elishakoff, "Interrelation between safety factor and reliability", NASA, CR 2001-211309, 2001