The idea of parachutes for electric urban air mobility (UAM) is a double-edged sword in aviation. Electric vertical takeoff & landing (eVTOL) multi-rotor aircraft are inherently safe by design, but they are in the air nonetheless, so extra safety precautions must be taken. However, conventional parachutes can only work at certain altitudes. Aviation Safety Resources (ASR) — a leading parachute safety company that won one of Revolution.Aero’scompetitions earlier this year — says it has a parachute system that will work with eVTOL aircraft, even at low altitudes.
I recently spoke with Larry Williams, CEO of ASR, on how the company’s parachute technology works, its application for eVTOL aircraft, and public perception.
With a mission to disrupt the market for existing aircraft recovery systems and safety solutions for the next generation of manned and unmanned flight, ASR wants to make urban air mobility (UAM) even safer. Williams says standard recovery systems can’t work for eVTOL aircraft in the critical “vertical” stage (without forward velocity). Most canopies only work with fixed-wings airplanes and depend on forward speed to inflate the canopy. This is why helicopters don’t have recovery parachutes. They can contra-rotate if down in time at the right altitude and can land themselves as safely as possible.
When it comes to fixed-wing aircraft, parachutes when deployed in flight first slow down the aircraft — they inflate and then slow the descent to provide a touchdown condition. With the success of whole aircraft recovery systems, saving over 500 lives worldwide to date, we are starting to see parachutes appear as more “standard.” Pipistrel uses one located at the top of its cockpit, right where the wings attach to the fuselage.
The problem with conventional parachutes is that it takes time to inflate them. They need enough altitude and airspeed to serve their purpose. Even the use of rockets to quickly extract the canopy won’t inflate it in time if low to the ground. For example, the Cirrus needs to be 920 ft in the air for its canopy to fully inflate, which is not an option with an eVTOL at 500 ft taking off or landing in a populated area. If an aircraft is going 122 mph and falling at a rate of 179 ft/second, it takes 5.5 seconds to inflate. ASR worked around this limitation with an innovative patented solution that takes half a second to extract its canopy and another 2 seconds to inflate it. ASR’s recovery parachute works at 100 ft or less than in 2.5 seconds even in a VTOL operation.
Williams says it’s a tethered retro rocket that shoots up and slows down the descent of the aircraft while multiple small parachutes are extracted with track rockets, inflating during the extraction to not depend on altitude loss. This results in a retarded descent below 30 feet per second, providing a safe and survivable landing. It’s a passive safety system installed in the design of the UAM vehicle, similar to an airbag for automobiles.
Williams told me there needs to be a fresh look at recovery technology for tomorrow’s UAM needs, with a specific design approach to eVTOL. ASR designed a new line of next-generation recovery products that are lighter weight with less volume that offer longer repack cycles than any similar products on the market today. Williams spent the first half of his career working on airplane crashes and came to the conclusion: “We may not be able to prevent a complete failure, but we can prevent many fatalities.”
Public perception is important for the adoption of modern electric UAM. The University of Michigan came out with a study that showed 80% of those asked said they would require a parachute when flying an eVTOL. There is also a marketing aspect to the notion of a recovery system such as a parachute. Williams feels public perception is ready for parachutes and says ASR has worked in the aviation safety industry for decades to help it add an extra layer of safety to already impressive electric reliability. The weight of the ASR parachute in a 4,500 lb aircraft is only 100 lb — consider that a 100 lb parachute could save 6 lives.
But what about rotorcraft, such as helicopters and gyrocopters? Williams told me his system could be deployed out from the side of the aircraft and not necessarily out from the top of the main lift rotor. ASR’s system wouldn’t get tangled and snapped by rotor prop strike with its reinforced kevlar technology that can withstand a prop strike.
ASR wants to revitalize and reinvent the aviation safety industry with a series of new products aimed at sport/experimental aircraft, light sport aircraft (LSA), general aviation (GA) aircraft, and VTOL and eVTOL aircraft. These systems will include unmanned aerial systems (UAS) and vehicles (UAV). Williams told me ASR wants to be first to meet the safety needs of the emerging UAM market.
I walked away feeling I knew more about something that seemingly seems so simple as a parachute but is much more than it appears at first glance.
Using a rocket-powered parachute that powers the canopy high enough to fully open does exist. Although all eVTOL and electric fixed-wing projects put the bulk of their research on safety, they wouldn’t suffer from this one extra layer of security.
For the full article, visit https://cleantechnica.com/2020/01/04/asr-says-it-has-a-parachute-for-every-evtol-aircraft/