This is an interesting, if doubtful, subject and I thought it deserved its own topic.
The tentative goal is to discuss actual research projects and their associated design philosophies and feasibility. The focus is on insertion platforms that incorporate a fixed wing component but a near vertical delivery (and a more limited coverage of equivalent ESTOL or pure rotary winged aircraft).
The only fixed wing gas turbine VSTOL transport aircraft I am aware of was an application for the Bristol Siddeley/Rolls Royce Pegasus.The engin in its four-nozzle form was developed specifically for the Harrier, but it did find its way into another, very different, aircraft. This was the Dornier 31 VSTOL transport. It had a Pegasus under each wing supplemented by four Rolls Royce RB 162 lift engines at each wingtip. To lift off into the hover therefore, a total of ten engines were running and the noise was appalling. The control system explored most of the possibilities. Pitch control was by jets at nose and tail carrying bleed air from the Pegasus. Roll control was by differential throttling of the lift engines and yaw control involved tilting the lift engines in opposition.
Controlling ten engines manually at near maximum thrust in stationary hover was probably impossible for routine operation so there was a three-lane automatic system giving smooth movement in pitch, roll and yaw. For development though, it was necessary to test fly the aircraft manually and, in addition, to flight develop the auto-system. At the time (ca 1968) it was said, in Bristol, that Dornier had ‘a crazy American pilot’ who was doing all this. This was Drury Wood, formerly a major in the United States Marine Corps and a veteran of combat in World War II and Korea, and of test flying for the USMC. (In appearance he bore a strong resemblance to the film star Robin Williams). Wood had lifted the aircraft into the hover for the first time and made the first transition from the hover into wing-borne flight. He had hovered it manually and flown it backwards. In forward flight he had even performed barrel-rolls. In 1969 Drury Wood brought the Do.31 to the Paris Airshow.
Three Do.31s were built. E1 had no lift engines and was used for conventional wing-borne flight development only. E2 did not fly, being a bare airframe for structural test. E3 was the full VSTOL aeroplane, flown so impressively by Drury Wood. There seemed at that time to be some feeling that the odds in favour of Drury Wood reaching old age were perhaps a little unattractive. Happily, he died peacefully at his woodland home in Grant’s Passage, Oregon in 2019 at the age of 96.
Dornier 31, E3 in flight.
It can be said with confidence that Drury Wood is the pilot
here because he was the only pilot who ever flew it.
The tentative goal is to discuss actual research projects and their associated design philosophies and feasibility. The focus is on insertion platforms that incorporate a fixed wing component but a near vertical delivery (and a more limited coverage of equivalent ESTOL or pure rotary winged aircraft).
On the Do 31, DGLR-Bericht 2000-01, "Die deutschen Senkrechtstart-Flugzeuge", provides a payload-over-range diagram on p. 211.
The characteristics points are (eyeballed from the diagram, so not perfectly exact):
VTO departure: 2350 kg payload - 170 km --> 0 kg payload - 900 km
STO departure: 4900 kg payload - 430 km --> 1300 kg payload - 1300 km
CTO departure: 5000 kg payload - 570 km --> 1700 kg payload - 1400 km
For STO and CTO, the data points are valid for maximum landing weight (21800 kg) resp. maximum internal fuel (6030 kg).
I've added the data points to a diagram showing V-22 figures, but as that stemmed from a US Army page, it's not for standard day conditions but for hot & high operations, so the V-22 is actually a bit more capable relative to the Do 31 than indicated (as the Do 31 data most likely is for standard day conditions, otherwise I'd expect it would have been pointed out alongside the data).
In addition to the extreme noise, airfield erosion was another serious problem that required special heat-resistant concrete surfaces on airfields. Operation from unprepared surfaces included a certain risk of ingestion of loose lumps of soil thrown into the air by the jet exhaust. Though Dornier thought that this would not present a serious risk, it was actually never tested systematically.
Dornier also projected a Do 131 and a Do 231 that would use high-bypass ratio jets to reduce exhaust temperature and improve efficiency, but of course, these were paper projects only.
For the flight control, Dornier started their own development program of analog/digital Hybrid computers. Analog computers were very well suited for that task, because they tended to be much faster and failure resistant than digital computers.
There are a couple of intresting videos about analog computing by Prf. Bernd Ulmann (all in German).
I was going to quote the OP with some examples of various bad ideas from over the years (e.g. Bristol-Siddeley Pig)... then I noticed that the OP was me... just much younger
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