The Arnold AR-5
In August 1992, an ex film-maker from Northern California set the normally studious world of aerodynamics ablaze.
It wasn’t just that Mike Arnold had designed and built his own plane in a cramped former restaurant, or that he’d set an official world speed record for aircraft under 300kg (FAI Sub-class C-1a/0) of 343.08 km/h over a 3km straight course.
It wasn’t even that he’d clocked 213.18 mph with fixed landing gear and a Rotax 582 two-stroke engine rated at only 65HP. (Think about that for a minute…)
What really had the NASA scientists and aviation media beating a path to Pinole, CA was that Mike had broken the fabled one square foot drag barrier, and he’d done it without any formal training or qualifications.
It was a unique sequence of triumphs for homebuilding.
That square foot barrier
In aerodynamic circles, building a man (or woman)-carrying airplane with less than one square foot of drag area had been the equivalent of the 4-minute mile to 1930s athletes and the sound barrier to 1940s test pilots.
The AR-5 had smashed that ‘impossible’ mark with a flat plate drag area equivalent to just 0.88 square feet.
Up until that point the benchmark for slipperiness, certainly among propeller driven aircraft, had been the P-51 Mustang.
Drawing on a wealth of brilliant engineering, aerodynamic expertise and exhaustive wind tunnel analysis, the P-51 team achieved a drag coefficient of 0.004 with the Meredith Effect doghouse negating cooling drag and the landing gear neatly retracted.
By comparison, the home-made AR-5 had a drag co-efficient of just 0.0038 – legs to the wind.
But when the experts turned up at Mike Arnold’s workshop there were no wind tunnels or sophisticated computer analyses in sight (or even in the same county, for that matter).
And when they pored over the AR-5 with their slide rules and crazy-long equations, all they found was good design and the meticulous craftsmanship of an artist.
A work of art
When he was ready, Arnold shared his ‘mystery ship’ with a number of pilots from leading aviation magazines. They all agreed that the little speedster was also a sweet-handling machine, with beautifully harmonised controls and plenty of room for the pilot.
It sounded like an impossible combination – but there it was.
Dave Martin, Editor of Kitplanes magazine (in 1999) went so far as to say it had the most nicely harmonised controls of any aircraft he’d flown; placing it on a par with the Stelio Frati-designed Sequoia Falco. Another homebuilt, you’ll notice.
Watch and learn
I won’t kid you – this is a film, not a clip, and it will take over an hour of your time. But if you have an interest in aircraft design generally, or aerodynamics in particular, you’ll be richly rewarded.
It’s not heavy-going either. Thanks to his film-making experience, Mike Arnold is a gifted story-teller and his World Speed Record gives Why it goes so fast a genuinely entertaining plot and structure. Plus, Arnold’s gravelled voice and homely style makes it all feel like an aerodynamics adventure starring Jimmy Stewart.
Once you’ve watched this film you’ll have an enriched understanding of airflows, aerodynamics and drag reduction. You’ll be able to look at any aircraft and know why the designers did what they did – and where they made compromises.
Aviation film festival
Arnold had originally planned to sell plans for the AR-5 but, while he was satisfied with the design, he decided to wait and see how the gathering storm of product liability suits would play out. Well, we all know how that went – and our loss is some law firm’s gain.
Instead, Arnold fell back on his first craft, producing a series of movies about his beloved plane and selling video copies to homebuilders and aviation enthusiasts. The full set of films is:
• Why It Goes So Fast
• How It’s Made
• Moldless, Low-Drag Wheel Pants
• The AR-5 In Action
• Making Fibreglass Molds
• Making A Molded Fuselage – Shaping The AR-6
There is no CGI or even a pretty diagram in any of them. There is a load of heart though, and each documentary offers an engaging story as well as plenty of information.
Thank you for your genius
The AR-6 ‘Endeavour’ of that last film is the curvaceous crimson Formula One racer, designed and built by Mike for owner/pilot Dave Hoover. It would go on to win the Reno Gold Championship Races in 2007 and 2008.
It is now owned by Steve Senegal and is still racing at Reno, although Lady Luck is yet to smile on the partnership.
Meanwhile, the AR-5 was donated to the Hiller Aviation Museum in San Carlos, CA, where it is currently on display.
Mike Arnold died just over a year ago – October 6th, 2015. He considered his aviation films his legacy and, after his passing, the Arnold family generously shared all six on YouTube.
It’s hard to think of a more appropriate way to remember this quiet genius of homebuilding, composite construction and amateur (in the truest sense of the word) aerodynamics.
You can read more at The Arnold Company website. (The ‘Tapes’ link will take you to all six movies on YouTube.)