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Ouch! Air taxis blast like a hurricane on take off and landing

By David Szondy
January 12, 2025
Ouch! Air taxis blast like a hurricane on take off and landing
eVTOLs have hurricane-force downwash
eVTOLs have hurricane-force downwash
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eVTOLs have hurricane-force downwash
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eVTOLs have hurricane-force downwash

If air taxi services ever take off, you might want to hold onto your hat very firmly. A new FAA report looking at various eVTOL prototypes shows that when they take off and land they have a downwash from rotors equivalent to hurricane-force wind.

Film buffs may remember the opening of the 1965 musical The Sound of Music where the camera swoops over the Austrian alps and zeros in on a distant Julie Andrews dancing in a mountain meadow. What was edited out was Miss Andrews getting knocked on her backside, thanks to the downwash from the camera helicopter.

These DownWash and OutWash (DWOW) effects are notorious for helicopters and are one of a number of reasons why helicopter air taxi services have never been very successful. Since eVTOLs are governed by the same laws of physics as helicopters, the US FAA is very interested in learning as much as possible about the DWOW effects of the new aircraft being developed for what is hoped will be the first truly successful air taxis.

For the new report, the agency tested three unnamed prototypes with a maximum take off weight of below 6,500 lb (2,950 kg) in various rotor configurations and blade numbers. Around these were placed sensors at different distances and heights to measure air pressure to help digital simulators reconstruct airflow patterns.

What they found was that the eVTOLs generated downwashes at speeds of up to 99.3 mph (159.8 km/h). That's a Beaufort wind force scale of 12 or equivalent to a hurricane. The pedestrian safety wind limit is 34.5 mph (55.5 km/h). According to the FAA, these effects exceed agency recommendations for safety areas at vertiports or heliports. Such winds could result in the lifting of unsecured objects off the ground, knocking people about in the vicinity like tenpins, and kicking up enough dust to cause brownout visibility.

None of this means air taxis are off the menu, but it will mean tweaking the regulations and making various recommendations about how and where large eVTOLs can operate. These include extended safety zones, setting up Downwash Caution Areas (DCA) with restricted access, and developing high-capacity computer analysis to better understand the safety issues.

How to deal with air taxis working in the vicinity of Austrian governesses frolicking in the Edelweiss has yet to be determined.

Source: FAA

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AircraftAir TaxisFAAeVTOLElectric VehiclesAviationFlight
26 comments
David Szondy
David Szondy
David Szondy is a playwright, author and journalist based in Seattle, Washington. A retired field archaeologist and university lecturer, he has a background in the history of science, technology, and medicine with a particular emphasis on aerospace, military, and cybernetic subjects. In addition, he is the author of four award-winning plays, a novel, reviews, and a plethora of scholarly works ranging from industrial archaeology to law. David has worked as a feature writer for many international magazines and has been a feature writer for New Atlas since 2011.

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26 comments
Techutante
So Large Safety Zone and no unattached objects in the Helipad area. Gotcha. Also never ride one of these in heavy winds because you're not going to live. Many downsides.
anthony88
The B-47 in the background!
vince
Whats really needed is antu gravuty drives which nullify the Earths pull on us fragile humans. Sort of a future like in the movies where you see cara driving without any apoarent blades such as in the 5th Element. Dont expect that anytime soon
-dphiBbydt
Landing and taking off on a grill-like surface with significant space underneath rather than a solid surface would make sense.
dan
eVTOLs produce stronger downwash than helicopters due to their smaller rotors, which catch less air and therefore require more rapid acceleration of that air. This issue could be managed with larger helipads, such as those the size of a football field. I am more concerned about safety during the first 1,000 feet of height, as eVTOLs lack systems for handling bird strikes or catastrophic failures. Unlike helicopters, eVTOLs cannot autorotate to a safe landing, which means an eVTOL could simply fall from the sky.
Towerman
And this is an issue how ? Simply make pedestal platforms for landing which has been the main idea all along. @Techutante Another Christopher sock ?
Fly these craft Especially in high wind ! Multicopters is superior in terms of handling wind the Electric motors react Instantly compared to a helicopter's massive disc where centrifugial forces are so high and the surface area so big where wind greatly affect its agility.coupled with an inefficient drive train and slow moving control surfaces.
Grow up grow wise google is your friend.
Because multicopter motors react instantly, it instantly reactx to the diverse kind if wind forces a craft can experience in flight.
Bodger
So someone expected the laws of physics to be repealed for this particular technology? The air must go down if the vehicle is going to go up. Full stop.
MrB
Really? People are JUST realising this? What did they expect, when you're trying to lift a several hundred kilo (minimum) object into the air? If you're developing 'last mile' or even 'port to port' transport, this should be a foremost consideration. Where, in a city, do people think you're just going to 'land' something like this? Or even urban/suburban areas? Toys for rich people, at the best, or 'air taxis' for the rest. Wait till 2 of these collide mid air - lawsuit, anyone?
dan
@ towerman: Helicopters and gyrocopters are among the most stable aircraft due to the high inertia of their large rotors, making them less affected by wind gusts. In contrast, all other aircraft designs, including eVTOLs, can become uncomfortable, shaky, or even unsafe in bumpy conditions.
Arcticshade

@Dan I am much more concerned with a helicopter having to autorotate during an emergency.
A multicopter have 1st of all indisputably a more reliable power train.
Electric Motors simply does not fail. +1 for Towerman on that.
In the very extreme rare event that a motor does fail, you have multiple redundant motors taking over in an instant where as for a manned helicopter you have to rely on a human to bring the heli down with no power and only get 1 shot at landing perfectly right. Only 1 shot. With 2 motors out a multicopter can choose its landing spot with multiple tries even a 10 year old can do it.
Meantime auto rotation on a helicopter A manouvre as proved again and again over the years is extremely risky lt has lead to 1000s upon 1000s of fatalaties. We have full NTSB records stipulating it in the most vivid detail.
No thanks as soon as EVTOLS take commercial flight i'll never jump in a heli again. EHANG is making Waves in China already !
Electrics is King wuth regards to safety, reliability and low maintance compared to any her power rrain in existance hands down !
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