Flying fast and close to other aircraft is sometimes scary but always fun — and ‘ordinary’ pilots can try it too
There’s flying fast and then there’s just pure speed
Anew world record was set a short time ago, which I don’t think has gained the publicity it deserves. On 28 August 2017, at Clarks Field, Idaho, USA, the Absolute Propeller-driven Piston-powered speed record was broken by Steve Hinton Jr. His modified P-51D Mustang, Voodoo achieved an average speed of 531.53mph, with the fastest of four laps of the Fai-defined 3km circuit reaching 554.69mph. Oh, and adding to the thrills, the record was set at 70ft agl!
When I describe Hinton’s Mustang as ‘modified’, I think that’s a bit of an understatement. Like many of its kind in unlimited air racing (where Voodoo won the legendary Reno ‘Gold’ award in 2012, 2013, 2014 and 2016), the former USAF and Royal Canadian Air Force Mustang features radical changes to boost its performance. For a start the wingspan is around six feet shorter than standard and the laminar flow wing section is also altered as well as its planform, giving a wider wing-root and more tapered wingtip.
On Voodoo this isn’t just about dragreduction, but also about shockwave and pressure management as the aircraft gets close to supersonic speed. In fact, on some of its test flights the aircraft was surrounded by the air vapour ‘halo’ that normally accompanies transonic flight!
Then there’s the engine. Typically, in military service, a late model Rolls-royce Merlin could just about develop 2,000 horsepower. A typical unlimited racing engine develops 3,500 or more, using pressurised mechanical fuel injection and a supercharger running at around 150 inches of mercury, or five bar of boost pressure. Turbochargers aren’t used because the engine compartment and structure can’t dispose of the extra heat. Turbocharging would also mean extra cooling for the lubrication oil, adding to both weight and drag.
In addition to running a special brew of 140-plus octane fuel, anti-detonation injection (ADI) prevents charge detonation due to the high manifold pressures. On the record flight Voodoo probably consumed around sixty gallons of an ADI mixture — 50% water and 50% methanol — injected direct into the cylinders. In addition, to help keep the overworked engine cool, a spray-bar throws up to 45 gallons of water onto the front of the radiator. This not only cools the engine by the latent heat effect of converting water into steam, it also contributes a little extra performance. The aircraft’s forward speed forces the expanding steam through a nozzle in the fuselage, generating thrust in what is called the Meredith effect.
Ultimately the limiting factor for the speed of these aircraft is the loss of efficiency as the propeller tips break the sound barrier. Revised reduction gears in the Merlin engine are used to reduce propeller speed and the Voodoo team uses a relatively small diameter four-bladed propeller with wide ‘paddle’ blades to maximise thrust at maximum rpm. However, if you’ve ever heard the chainsaw transonic rasp of a Harvard propeller on a cold morning, just imagine the noise Voodoo made, with prop tips supersonic at low level at 550mph!
Of course, the piloting of such an aircraft requires special skills. One laconic unlimited racer commented, “well, it’s still just an aeroplane, but when you take six feet off the wingspan and double the power, things get a little more squirrely”. And that’s before you factor in classic taildragger handling, combined with limited visibility through a minuscule drag-reduction canopy and an approach speed of not much under 200mph! All I can say of Steve Hinton Junior and his contemporaries is; respect!
Now I know that there’s as much chance of you or I getting our hands on an unlimited air racer like Voodoo as we have of strapping ourselves into Lewis Hamilton’s Mercedes Formula One racing car, but if you were to fancy air racing, there are some options open to us. First, the Royal Aero Club’s ‘3Rs’ (Records, Racing & Rally Association) runs a training event and organises annual air races around the UK and in Europe. So long as you have 100 hours P1 and your aircraft can reach a continuous 100mph in level flight, you could participate in handicap races including such prestigious events as the King’s Cup or the Schneider Trophy. Check out http://www. royalaeroclubrrra.co.uk/
If you fancy even more thrilling, wingtip to wingtip racing around a tighter course in purpose-built racing aircraft, then the recent resurgence of Formula One air racing in the UK, France and Spain might just be for you. The sport has been around since the late 1940s, when the ‘formula’ was created in America to offer a lower-cost alternative to the ‘unlimited’ warbirds. The concept has proved a success ever since, with the diminutive racers, powered by tuned Continental 0-200 engines providing close racing at speeds up to 250mph at events across the USA.
For a number of years, in the late 1960s and early 1970s, there was a thriving racing scene in Europe, but it then went into abeyance. The aircraft remained though, ranging from the functional and fast Cassutt, to the breathtakingly beautiful Cosmic Wind and Midget Mustang, and British designs including the Taylor Titch and Rollason Beta. Now, as part of the Air Race 1 World Series, some of these aircraft are back in active competition once again.
In mid-november, three British pilots are travelling to Thailand to uphold national honours in the next round of the series. Trevor Jarvis (see October’s Pilot), Des Hart and Yves Clarke will be waving the flag for the UK, against pilots from the USA and Europe. The races are set to be broadcast live on the internet and I, for one, will be watching and cheering ‘our lads’ on!
Describing Hinton’s Mustang as ‘modified’ is an understatement
The recent resurgence of F1 air racing might just be for you