# Development of a Drone's Vibration, Shock, and Atmospheric Profiles
## 1 Introduction  
Technological advances in unmanned aerial vehicles (UAV) have made it possible to operate drone deliveries of packaged products. Since 2011, the drone firm Matternet has used drones to deliver medical supplies and specimens to countries around the world, including Switzerland, Haiti, and the Dominican Republic [1]. In 2017, Matternet and Mercedes-Benz collaborated and used vans as rolling distribution hubs (drone-van combos) for a three-week aerial package delivery to deliver goods for local e-tailer Siroop in a Swiss city [2]. JD.com in China plans to build 185 drone ports in China's mountainous southwest region to cut logistical costs [3]. The logistics affiliate of e-commerce titan Alibaba, Cainiao, recently used drones to deliver tea leaves from mountain slopes directly to processing centers below, shortening the time to market [4]. The Icelandic company, Aha, which launched a limited trial with Israeli company Flytrex in 2019, will phase in further drones over the next two years [5]. UPS and DHL also conducted trial runs for residential delivery [6]. Similar to other transport means, the drone and its payload experience vibration, shock, and atmospheric hazards during the take-off, in-flight, and landing [7]. The vibration and shock to the drones are usually associated with two sources. The first is the structural vibration and shock resulting from periodic excitation from drone motors and propeller blades [8]. Throttling up or down can increase or reduce the periodic excitationfrequency. The second is the interaction between the drone quadcopter/propellers and the airflow, which is also variable as it depends on air turbulence and weather patterns. The atmospheric hazards are due to the atmospheric environment acting upon the goods without shielding. Understanding these input vibrations as well as the generated shock and atmospheric conditions will help packaging engineers better understand these hazards and provide sufficient protective design for various goods delivered by the drone. In contrast to the numerous measurements on the truck [9; 10; 11] and rail [12; 13] environment garnered within the last 30 years, only a few major research studies have been conducted in the field of aircraft environment to better characterize its vibration, shock and atmospheric profile. The Forest Products Laboratory's (FPL) General Technical Report 22 is an early report conducted on aircraft vibration during taxi, takeoff/landing, and cruise mode [14]. The study indicated that the excitation frequencies are highly dependent on the type of aircraft engines such as turbojet and turboprop whereas the amplitudes are more dependent on the flight modes (takeoff, climb, cruise, and landing). For example, the engine of turboprop had an excitation frequency of 68 Hz for C-130 aircraft and 48 Hz for C-133 aircraft. However, the data included in the FPL report did not indicate overall \(\mathrm{G}_{\mathrm{rms}}\) (overall energy of random vibration) levels for the different aircraft types. In 1988, Trost conducted a research study to measure an aircraft's acceleration, involving mechanical stresses during air cargo shipment [15]. The recording device was mounted on the pallet in the air cargo. The measured maximum G-level ranged from 0.05 G to 0.16 G during cruising of the flight and 0.20 G to 0.42 G during the taxiing, takeoff, touchdown, descent and landing. The Amgen Air PSD profile was developed by mounting the data recorder to the floor of a unit load device (ULD) inside of a jet engine aircraft [16]. The resulting PSD published had an overall \(\mathrm{G}_{\mathrm{rms}}\) level of 0.017 \(\mathrm{G}_{\mathrm{rms}}\) level. The collected vibration was not measured directly from air cargo but from the ULD. In order to develop a vibration profile as direct input, [PERSON] and [PERSON] [17] mounted the recorder in the cargo area next to the wing of the aircraft and recorded the in-flight vibrations of a turbo propeller aircraft.