A group of Southampton University engineering students are set to start assembly of a human-powered aircraft they hope will bag them a pair of Royal Aeronautical Society Kremer prizes, worth £100,000 ($161,000) to develop an aircraft for sporting competition in typical British weather, and £50,000 for flying a marathon distance in less than an hour.
Their aircraft, called SUHPA – Southampton University Human Powered Aircraft – is inspired by the mid-1980s Musculair project, which won several Kremer speed prizes and managed the significant feat of flying with a passenger. SUHPA is not radical – "a little stiffer, a little lighter" than Musculair 2, says Dr Alex Forrester, project team leader – but the team is working with a big advantage: an autopilot.
CONTROL MATTERS
Southampton’s control system features an autopilot developed by a former student and now successful as a UAV component. Battery-powered servers, allowed by Kremer rules, will control the two ailerons and vertical and horizontal stabilisers, so the pilot will only need to provide basic right and left steering and control altitude by the pedal rate.
A standard radio-control unit operated from the ground could take control, if needed, for safety.
The high wing design, typical of HPAs, was chosen for lateral stability and allows fore-aft adjustment. Unusual for such machines, though, is the drive train, which is a standard road racing bicycle bolted in by the axles.
Forrester, seen here testing the drive unit, with propeller and shaft connected by a normal bicycle chain to the cycle’s freewheel, says the configuration was chosen for two reasons – use of a standard bicycle fits the spirit of the Kremer rules, which emphasise practicality, and a modern carbonfibre bicycle frame is hard to beat as a rigid, reliable, lightweight drive system. The bicycle wheels double as the landing gear and the pilot will also be able to shift gears in flight.
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Forrester’s students have calculated that SUHPA will require about 0.3kW for cruising flight, although Forrester thinks they may have been optimistic about gains in ground effect and expects demand to be more like 0.36kW. To fly the triangular course dictated by the Kremer sporting prize will demand upward of 0.4kW, and more at take-off.
Such a power output is within the reach of club cyclists. For first test flights, hopefully around the end of August, Forrester himself will fly, although his brother is being trained to make a sporting prize attempt in November. Noting that few cyclists can actually ride 42km (26mi) on the road in an hour, however, Forrester expects the marathon challenge to be more difficult, probably not achievable by a pilot weighing more than 70kg (154lb).
The sporting challenge is thus more suitable for a university project, although he reckons a single aircraft could, with such modifications as a change of propeller, meet both tests. Wind tunnel tests conducted in July used a 7.5 revolutions per second propeller that has featured on other British HPAs. The SUHPA team is developing a faster propeller.
STORIED FOOTSTEPS
In shooting to claim the remaining RAeS Kremer prizes, the Southampton team is following in some storied footsteps.
The first, £50,000, Kremer prize was claimed in 1977 by the late AeroVironment founder Paul Macready, with the first-ever sustained and well-controlled human-powered flight, of Gossamer Condor. Two years later, Macready went on to win another £100,000 for the famous Gossamer Albatross flight across the English Channel.
In some ways, Forrester and his students have set themselves a tougher challenge. While they have much work to build on – Macready’s efforts sparked more than a decade of international attention on human-powered flight, lessons from which have proved significant in the development of low-powered unmanned systems, and Southampton University first built an HPA 50 years ago – the Kremer sporting challenge looks daunting.
To date, human-powered aircraft have been delicate machines only flyable in virtually still air. However, the sporting challenge demands a robust, practical design that can be easily assembled and disassembled and transported in an 8m (26ft) road trailer.
Going one better, SUHPA is designed in 4m segments. Forrester is optimistic but keenly aware of the scale of the challenge: "Presumably we’ll find hurdles on the way, which explains why the prizes are still there."
Meanwhile, his students face logistical challenges that would be recognised by the biggest companies in aerospace.
The project started in September 2010 and while all the parts have been designed and ordered, there is, as yet, no complete aircraft so an August first flight and November prize attempt is itself a challenge. Forrester readily admits that "no end of manufacturing delays" may be lurking.
But unlike big aerospace companies, which measure scheduling success or failure in millions of dollars, the SUHPA project has modest financial issues.
A Kremer prize would be used to pay back £20,000 provided by the university to build the aircraft, and possibly to provide a small prize for students who have worked on the project.
The remainder, Forrester says, would be used to fund similar projects, such as adding an electric motor and photovoltaic cells to make a hybrid aircraft.
Source: Flight International
