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I was very surprised to see there's a seemingly underway project for a VTOL "business aircraft" that seats a few people.

http://xtiaircraft.com , https://www.startengine.com/xti-aircraft

enter image description here

They assert they've done a 65% scale test.

I realize historically there have been a couple military transport-sized VTOL aircraft, and there's one or two small ones today.

Is anyone contemplating a regional airliner or even full-size airliner VTOL concept?

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    $\begingroup$ The AugustaWestland AW609 tiltrotor is already in flight test and is being marketed for VIPs, search and rescue, and as a helicopter replacement for offshore oil rigs. $\endgroup$ – user71659 May 14 at 6:22
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    $\begingroup$ @user71659 - whoa ! $\endgroup$ – Fattie May 14 at 9:17
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    $\begingroup$ !! Now with BOUNTY !! $\endgroup$ – Fattie May 16 at 13:00
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    $\begingroup$ @user71659 the AW609 is definitely an answer to this post IMO, I encourage you to write an answer giving an overview of it, since no one else has done so yet. $\endgroup$ – zymhan May 16 at 13:33
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    $\begingroup$ @zymhan The question is asking for a regional or mainline transport, 9 seats on the AW609 is too small for a regional. It would be V-22 sized and above. Talk about commercializing the Bell V-280 (a tiltrotor halfway in between the AW609 and the V-22) would be a step in that direction, but AFAIK it's been just talk. $\endgroup$ – user71659 May 16 at 16:05
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US patent 9,475,585 describes a Tilt-Rotor Vertical-Lift Aircraft. This patent was awarded to Boeing on October 25, 2016. The subject aircraft may be anything from a personal aircraft to a regional commercial aircraft for at least 100 passengers.

The two tilt rotors (36) are powered by a number of turbine engines (40) which are fix mounted under the wings. The novelties claimed by this patent are about the transmission of power from the power plants (engines) to the rotors.

Figure 1 - in vertical mode: a/c vertical mode

Figure 2 - in horizontal mode: a/c horizontal mode Images source: United States Patent and Trademark Office, www.uspto.gov

Of course, the filing of a patent is an evidence that a company is spending at least some limited resources to the subject. However, this does not mean that Boeing is actually developing such an aircraft.

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    $\begingroup$ A fast browse of the claims suggests to me they won't be developing this to an actual aircraft. One of those things where I am not sure if it is insanely cool or just insane. Well worth a look, thanks. $\endgroup$ – Ville Niemi May 16 at 13:36
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    $\begingroup$ Great! A jet intake located right in the prop wash! What could possibly go wrong? $\endgroup$ – Peter Kämpf May 16 at 15:40
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    $\begingroup$ @PeterKämpf, from brief reading of the text it seems that all the engines (the text says at least two) are turboshafts, attached to common shaft that drives the rotors. And the picture does not necessarily indicate actual position of the engines, so they may be either close to the tilt-rotors so they behave mostly as any other turboprop, or close to the fuselage, outside of the prop wash. $\endgroup$ – Jan Hudec May 16 at 17:26
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    $\begingroup$ Whoa! I wanted an example project and you brought a patent! Unreal! $\endgroup$ – Fattie May 16 at 19:35
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    $\begingroup$ Really, I guess this is the closest thing to Are there any current projects/plans for a VTOL passenger airliner? ... thanks! $\endgroup$ – Fattie May 22 at 13:13
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VTOL airliners were looked at in the 1960s. The Hawker Siddeley HS.141, for example:

enter image description here

The idea was dismissed for several reasons that still hold today:

  • lots of engines which use lots of fuel and are costly to buy and maintain
  • massive loss of payload (because of all the engines that are dead weight during most of the flight)
  • jet-borne VTOL is very loud (e.g. the Harrier was one of the loudest aircraft ever), and VTOL only makes sense if you can land in population centers rather than out-of-the-way airfields. so you'd run into noise regulations.

Electric motors have one big advantage over the turbines used until now: turbines are inefficient when they run at low throttle settings, so if you use one engine for takeoff and cruise, it's running inefficiently for much of the flight. Electric motor efficiency is high throughout its power range.

Whether it's viable remains to be seen, XTI hasn't published full specifications.

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    $\begingroup$ Electric motors may help solve the noise issue, but weight/fuel considerations remain for longer flights. $\endgroup$ – Robert DiGiovanni May 13 at 13:00
  • $\begingroup$ Does it essentially cost "much more fuel to take of VTOL than to take off conventionally" ... ? Is that about right? Is this still true with the electric motor notion? $\endgroup$ – Fattie May 13 at 14:09
  • $\begingroup$ .. and how come it's suddenly viable (unless it's BS) for a 6 seater? $\endgroup$ – Fattie May 13 at 14:09
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    $\begingroup$ @Fattie start-ups and concept designs are under no obligation to be viable. $\endgroup$ – AEhere supports Monica May 13 at 15:10
  • $\begingroup$ how true, @AEhere ! $\endgroup$ – Fattie May 13 at 16:26
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There probably won't be because of simple economics. (Even I can understand them, must be simple and obvious.)

Basically even a regional air liner transports a significant amount of people on a regular basis. It is not designed for single transports of single groups, it is designed to serve sustained needs. This means there must be sustained ground transport infrastructure in place at the end points for those groups of people to travel to, gather, embark, disembark, scatter and travel to their destinations.

In other words you need an airport with infrastructure to handle passenger traffic. If you have an airport, you might as well build a runway. It is basically a specialized road for aircraft and you need to build roads anyway.

If you have a runway, conventional take off and landing will be much more economical than a vertical one. That is without the extra mass of the VTOL hardware factored in. Thus the kinds of places it makes sense to use VTOL passenger craft and the kinds of places it makes sense to use air liners, even regional ones, are mutually exclusive.

The amount of traffic is either too low for service by airliners or too high for not building a proper runway that makes VTOL unnecessary waste to make sense.

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  • $\begingroup$ Heliports are a thing. Aircraft that can transport more passengers via existing helipads should conceivably increase demand. Helicopter ferry service from Pan Am's Manhattan office tower to their airport terminal existed for a short while before an accident put a stop to the concept: en.wikipedia.org/wiki/MetLife_Building#Helicopter_service $\endgroup$ – zymhan May 16 at 13:39
  • $\begingroup$ @zymhan Absolutely, I am not arguing about VTOL passenger traffic just whether it makes sense to scale it to a point where you could legitimately talk about a regional airliner. $\endgroup$ – Ville Niemi May 16 at 13:43
  • $\begingroup$ Ville, thanks for this but - I'm looking for examples of work in progress, on this question. BTW notice there are two other questions about reasons-for VTOL (see under the question here). $\endgroup$ – Fattie May 16 at 19:36
  • $\begingroup$ Smaller airports (basically "tiny" viz a viz today) would be an tremendously major economic change, I think. But points well made! $\endgroup$ – Fattie May 16 at 20:50

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