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Kitty Hawk reveals Heaviside, its latest flying vehicle

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Marc Zeitlin

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... Do you know if they've done tests at full MTOW yet?
I don't. I was involved with a design review of the plane about a year ago, but haven't heard much since. We were reviewing structure, and saw the planes and the video of the flights, but we didn't get into all the parameters of the test flights.

One of the issues I've had with a lot of these new "air mobility" companies is that they fly their vehicles almost exclusively by remote and, as near as I can tell, without simulating a full payload.
Can't comment on that - don't know anything in that area.

I'm not actively doubting whether this company is doing that - in fact, given the location of the pilot in the design, I rather suspect that they must have some ballast in the cockpit to keep the CG in-range - but simply wondering if you have any information about testing at full gross.
Nope.

Of course, since the definition of "MGW" is determined by the company, as is the maximum "G" loading required, it's not clear what it would mean to say that "yes, they've tested to MGW". What if they were only going to attempt certification to 2.5G? Or 3.8G? Or 4.4G? Or 6G? MGW means something different at each one... A bit nitpicky, but still...
 

Topaz

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... Of course, since the definition of "MGW" is determined by the company, as is the maximum "G" loading required, it's not clear what it would mean to say that "yes, they've tested to MGW". What if they were only going to attempt certification to 2.5G? Or 3.8G? Or 4.4G? Or 6G? MGW means something different at each one... A bit nitpicky, but still...
Thanks, Marc.

By MGW/MTOW, I mean 1g maximum design weight at takeoff. Empty weight + "fuel" (weightless electrons in this case) + maximum payload. Just curious. In this case, with the payload in the nose, it would seem like they'd need to have some ballast in the vehicle to keep it in the normal CG range.
 

Mad MAC

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It should be pointed out that unlike fixed wing, the critical gust load case for rotor-craft is in hover (& if anyone knows a simple way to calculate it like there is for FAR23, I would love to know). So these vertol aircraft actually have two different critical gust load cases.

With all those engines that pitch on command, I would guess that in forward flight the CG envolpe is highly tailorible by adjusting engine pitch.
 

Topaz

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The really critical case for VTOL aircraft is gust conditions during transition from hover to horizontal flight. Maximum power and control authority required, more than all other cases.
 

Andy_RR

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I think gust loading will be actively managed since the flight controller will be doing most of the actual flying. You just need enough hover power to avoid loss of lift but you can also weathervane and head towards the gust direction and work in ground effect to generate airspeed before climbing.

I like Heaviside because it kind of vindicates many of my ideas on eVTOL which I've been playing about with in CAD and X-Plane and hacked versions of Ardupilot SITL. I just don't have the moolah to make it reality yet.

 

Sunbird

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These machines move a relatively small mass of air down fast and will kick up a lot of dust and dirt in outback landings. Hopefully the landing can be fully automated by a last minute button to be pushed when committed to the landing (just before going IF) in order to avoid vertigo. Messy, but luckily no air breathing engines.
 

BBerson

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I don't know what the disc loading is, but must be relatively low if so quiet. The props are so close to the ground, so yes they kick up dust. The RC drones do automatic landings easily. They even return to within 12" of launch site.
My RC VTOL drone/airplane transitions and handles wind gusts. It just doesn't have any significant payload.
 

Topaz

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Even though they test out in the woods and fields, every single use-case scenario I've seen for these "urban mobility" vehicles really is "urban." The goal seems to be intra-city and suburban-to-city travel. As such, kicking up some dust is less of a design concern.
 

Mad MAC

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I don't know what the disc loading is, but must be relatively low if so quiet.
Disc load think wing loading for helicopters (mass / sweeped area).

Am I right in think that a higher disc loading results in a requirement for greater seperation from buildings etc to prevent re-circulation.
 

BBerson

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Am I right in think that a higher disc loading results in a requirement for greater seperation from buildings etc to prevent re-circulation.
I don't know if high or low disc loading matters that much for recirculating. When my little indoor Quadrotor is descending near the couch it gets sucked into the couch. Best to avoid buildings.
 

Andy_RR

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Vortex ring state is real for these things too. You can't fly in your own downwash else hover power goes to infinity or at least way more than you've got
 

BBerson

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I tried to get it into vortex ring state but was unable. Could be the four rings intermix or something.
 

Andy_RR

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I suspect that the higher the hover efficiency (Figure of Merit) the more susceptible it will be to VRS for two reasons - firstly high hover efficiency implies low hover power so there's probably not huge amounts available spare, and secondly, high velocity, concentrated jet efflux doesn't generate a generalized downwash volume that you can fly into during descent in the same way as a low disc loading device might.
 
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