A VTOL airliner in 1970 with four RR Pegasus.

oldironside · Jun 16, 2014

This just popped into my head. I was watching a vid about the Dornier 31, which had two Pegasus, but was undone by politics and the dead weight of its extra lift engines.

Can anyone build a viable four jet VTOL airliner which could operate between the world's smaller airports?

Gunnarnz · Jun 16, 2014

In any environment where economics come into play (ie: not the military world), I suspect that any market that can be served by a VTOL aircraft can be served better by a STOL aircraft. The compromises required for a VTOL design cut heavily into payload, and while something like a V-22 might have some niche utility I can't think of any civilian jobs it could do that couldn't be done vastly cheaper by a DHC-6, for example.

Edit: I suppose that one niche where a VTOL aircraft might have utility is on 'feeder' lines, like a sort of aerial bus, taking passengers from small local airports to larger hubs. This is pretty much the same role that the Rotodyne was envisaged filling, although it had other applications too. Even that however seems a bit unlikely given the economics. Surely it'd be cheaper to buy a bit more land for the airport in the first place, and then just run STOL aircraft from it.

jsb · Jun 16, 2014

VTOL airliner don't work !

VTOL aircraft have big engines compared to weight. Big engines use lots of fuel/ cost a lot / weigh a lot.

VTOL aircraft with multiple engines can only land/take off vertically by balancing them (if one fails they will crash).

VTOL are really loud (due to big engines).

All bad for any aircraft let alone an airliner, only aircraft that have to (ie somebody has destroyed my airfield or I cant afford a CV) Use VTOL.

JSB

Mumbles · Jun 16, 2014

jsb said:
VTOL are really loud (due to big engines).

Yup. The Harrier GR.3 was the loudest single engine aircraft I think I have ever had the pleasure of hearing at close range.

Delta Force · Jun 16, 2014

If it's simply for smaller airports (I suppose you mean with short runways) instead of taking off and landing in city centers, STOL aircraft can cheaply and easily do the job. It's rare to have an airport with short runways serving a large city, so the lower capacity and range aren't really an issue. The STOL aircraft simply has to be able to fly over to the nearest large airport or hub for the airline and transfer passengers to the more capable aircraft.

MattII · Jun 17, 2014

Indeed, STOL aircraft will work well enough for like 90% of the situations, and for those it wouldn't, simply make a smaller STOL aircraft. Realistically though STOL airliners will be a limited niche since most STOL systems incur extra drag or weight over standard aircraft, so would be unlikely to be used on routes where there's a large airport on both ends.

nixonshead · Jun 17, 2014

The only application that comes to mind would be serving really remote oil rigs or maybe large supertankers, where you need the VTOL capability of a helicopter but perhaps would want the greater speed of a jet. Similarly medevac in remote locations, maybe a jungle, where time to hospital matters. Those roles of course assume you could get a decent range out of the aircraft, and even then the advantages over helicopters would probably be marginal.

MattII · Jun 17, 2014

Pretty much, especially given the kinds of performance you can get out of helicopters with coaxial rotors (the Sikorsky X-2 made over 280 mph), plus if it's over water, what's wrong with a seaplane such as the Beriev Be-200 on ShinMaywa US-2?

Gunnarnz · Jun 17, 2014

MattII said:
Pretty much, especially given the kinds of performance you can get out of helicopters with coaxial rotors (the Sikorsky X-2 made over 280 mph), plus if it's over water, what's wrong with a seaplane such as the Beriev Be-200 on ShinMaywa US-2?

Seaplanes can't really land on rough water, whereas a VTOL could drop onto a pad. Granted it would still be hard, but at least the surface isn't constantly changing dimensions. So there are situations where a VTOL capability is useful, but they tend to be edge cases like "get someone from an oilrig to a hospital, in bad weather, faster than a helicopter can do it". You have to get pretty specific before you encounter a case that can't be handled by either a conventional aircraft (a seaplane, in the example above) or a helicopter.

Grey Wolf · Jun 17, 2014

I remember a British Harrier that did a emergency landing on a container ship.

I could envisage the idea of VTOL liners in a world where heliports on top of buildings are common, and for long-distance it makes sense to land a jet liner there.

Could be quite a fun world to write...

Is that a passenger compartment on the edge of the wing?

Best Regards
Grey Wolf

oldironside · Jun 17, 2014

Grey Wolf said:
I remember a British Harrier that did a emergency landing on a container ship.

I could envisage the idea of VTOL liners in a world where heliports on top of buildings are common, and for long-distance it makes sense to land a jet liner there.

Could be quite a fun world to write...

Is that a passenger compartment on the edge of the wing?

Best Regards
Grey Wolf

Thanks for the replies, guys. It's all food for thought.

The housing on the wing tips is for the auxiliary lift engines. They were used for take off and hovering, but were dead weight during normal cruising flight and only served to cut the payload. My choice of four Pegasus was to avoid this. They could be used for VTOL, STOVL, hovering and normal cruising flight. You can see the doors to the lift engines in this picture more clearly.

The noise problem from the Pegasus must be a result of the lack of a low velocity by-pass flow around the engine that you would associate with "normal" turbofans. This could be a difficult problem to overcome.

I actually phrased the OP wrongly. What I had in my mind's eye was a sort of Bae 146 sized airliner operating from city centres without the need for runways. I may have seen an artist's impression of this somewhere in the dim and distant past.

Having read the above posts I can see the clear advantages of going for a STOVL system. It would also mean a great increase in the payload if you could use an RN style ski jump, although I'm not sure this would be possible with paying customers. A business man in first class could end up wearing his complementary meal.

Just Leo · Jun 17, 2014

This was brought up not that long ago. It is a niche with distinct and viable assets, for them with bags of money to pay for it. The road to Osprey was paved in gold with spatters of blood. Somebody wanted it bad.

sonofpegasus · Jun 17, 2014

If you can butterfly the Fairey Rotdyne into service in the late 50's early 60's then I can see a jet Vstol equivelent being developed to go further faster and extend the route network. The logic would be to do away with the need for the Mega airports that now dot the country side.

Michel Van · Jun 17, 2014

The Irony the Serial model of Dornier Do-31 would not use the Pegasus engine, but two normal Jet engine and rely on 8 lift engine !
the Pegasus was backup in Prototype used in case the Lift engine failed.

But there is VTOL design with 4 Pegasus engine: The Armstrong Whitworth AW 681

jsb said:
VTOL airliner don't work !

VTOL aircraft have big engines compared to weight. Big engines use lots of fuel/ cost a lot / weigh a lot.
VTOL aircraft with multiple engines can only land/take off vertically by balancing them (if one fails they will crash).
VTOL are really loud (due to big engines).
All bad for any aircraft let alone an airliner, only aircraft that have to (ie somebody has destroyed my airfield or I cant afford a CV) Use VTOL.

JSB

The Do-31 had to carry 36 NATO soldiers with there equipment in total 3,500 kg
it could fly likewise fly 36 passenger and there baggage.

i thinking that is market for VTOL , especial for place were is difficult to land like Islands, sea platform or places without infrastructure.
also with range 1,800 km ideal for the task.

oldironside · Jun 17, 2014

Michel Van said:
The Irony the Serial model of Dornier Do-31 would not use the Pegasus engine, but two normal Jet engine and rely on 8 lift engine !
the Pegasus was backup in Prototype used in case the Lift engine failed.

But there is VTOL design with 4 Pegasus engine: The Armstrong Whitworth AW 681

The Do-31 had to carry 36 NATO soldiers with there equipment in total 3,500 kg
it could fly likewise fly 36 passenger and there baggage.

i thinking that is market for VTOL , especial for place were is difficult to land like Islands, sea platform or places without infrastructure.
also with range 1,800 km ideal for the task.

Well, well, well, live and learn. I'd never heard of the AW 681.

This business with separate lift engines was never going to work. Aside from the weight penalty, there is the little matter of the pilot trying to monitor and adjust multiple engines simultaneously before the days of an electronic engine management system. The VJ101 could have been a contender as a VTOL tactial fighter if it hadn't been for the fact that a loss of power in any of the aircraft's six engines during hovering would cause the thing to flip over.

So, it's basically all Pegasus or nothing.

zoomar · Jun 17, 2014

For civilian applications at small airports it really comes down to fuel costs, and especially noise. VTOLs expend a lot of fuel and are much more noisy that modern turbofan-powered airliners. As noted, the one application that only a true VTOL can do would be urban point destinations (airport shuttles, etc). The Fairey Rotodyne is probably the closest we will even come to that, and it was extremely noisy and uneconomical. If you really wanted fairly high speed aerial transport from city centers to airports, the only approach that uses available technology that wouldn't fall afoul of all sorts of environmental, safety, and noise regulations would probably be small airships like the Zeppelin NT.

oldironside · Jun 17, 2014

zoomar said:
If you really wanted fairly high speed aerial transport from city centers to airports, the only approach that uses available technology that wouldn't fall afoul of all sorts of environmental, safety, and noise regulations would probably be small airships like the Zeppelin NT.

Yeah, but it's not as cool as a 4 Pegasus VTOL airliner.

Michel Van · Jun 17, 2014

the VJ101 concept show it not work,
VJ 101C X-1 crash as thrust control in hover mode failed. pilot survived it.

also Dassault Balzac and IIIV failed but here the pilots dies

back on Harrier
original was that the name for the Supersonic P.1154 VTOL fighter for RAF and RN

it had to use advance supersonic version of Pegasus: the Bristol Siddeley BS.100/9
but Labor government of Harold Wilson kill the program and feasibility prototype P.1134 Kerstel became Harrier…

by the way there is one complet Bristol Siddeley BS.100/9 in a british museum.

Mumbles · Jun 17, 2014

oldironside said:
It would also mean a great increase in the payload if you could use an RN style ski jump, although I'm not sure this would be possible with paying customers.

SOLD. I would pay for that experience as a passenger

Mumbles · Jun 17, 2014

oldironside said:
The VJ101 could have been a contender as a VTOL tactial fighter if it hadn't been for the fact that a loss of power in any of the aircraft's six engines during hovering would cause the thing to flip over.

Yup, slight drawback. I wonder if in service would have had an auto-ejection system like the Yak-36? If certain parameters were met while in the hover Forger pilots would be punched out with or without their consent, which probably did wonders for their concentration.