Operational Risk Analysis and Hazard Assessment for the Release of Meteorological Dropsondes

Abstract

The flight experiments facility at the German Aerospace Center e.V. (DLR) in Oberpfaffenhofen operates four aircraft for atmospheric research and earth observation. Two of them have a modification to release dropsondes, Gulfstream G550 “HALO” (High Altitude LOngrange) and Dassault Falcon 20 E5. These probes descend with a parachute after release from the aircraft to measure in situ pressure, temperature, humidity and position. The measured data is transmitted in real time to a receiver in the aircraft. The collision probability and impact severity of such a dropsonde to aircraft flying below or to people on ground and on water are investigated for the most critical normal and failure cases. One failure e.g. is a parachute failing to open, causing the dropsonde to tumble downwards with higher kinetic energy. While an operating parachute reduces the impact energy on ground, it increases the risk of a collision with a flying object, because the time in the air is longer. The flight experiments facility at the German Aerospace Center e.V. (DLR) in Oberpfaffenhofen operates four aircraft for atmospheric research and earth observation. Two of them have a modification to release dropsondes, Gulfstream G550 “HALO” (High Altitude LOngrange) and Dassault Falcon 20 E5. These probes descend with a parachute after release from the aircraft to measure in situ pressure, temperature, humidity and position. The measured data is transmitted in real time to a receiver in the aircraft. The collision probability and impact severity of such a dropsonde to aircraft flying below or to people on ground and on water are investigated for the most critical normal and failure cases. One failure e.g. is a parachute failing to open, causing the dropsonde to tumble downwards with higher kinetic energy. While an operating parachute reduces the impact energy on ground, it increases the risk of a collision with a flying object, because the time in the air is longer. Thereby, data on residential density and traffic density worldwide will be analysed and an adequate factor determined for the probability calculation. The results will be checked against existing aviation regulations like the certification requirements for bird strike. By means of the Ground Risk Class (GRC) and Air Risk Class (ARC), the Specific Assurance and Integrity Level (SAIL) I – VI, which applies to Unmanned Aircraft Systems (UAS`s), will be determined to compare the threat level. Finally, the impact energy of a dropsonde is compared to the Specific Operations Risk Assessment (SORA) in accordance with EASA Air Ops SPO.OP.230. A Project Standard Operating Procedure (PSOP) will summarize the result acting as future guideline for dropping operations.