Flight report  on Streak Shadow

by Bob Grimstead
from World Airnews
Test flying the record-breaking unconventional Streak Shadow
 
In the course of evaluating aircraft for World Airnews, Bob Grimstead has flown a wide variety of machines ranging from the Boeing 747-400, through corporate jets, homebuilts, jet fighters and even hot air. balloons. This month, he tries his hand at flying a microlight.....

After a quick six-minute assembly, the bright red aerolane's nose-wheel gently nodded to the ground as designer David Cook eased his weight into its cockpit. The four-bladed propeller swung into life and the aircraft turned and briskly taxied to the far side of the tiny (150 by 190 meter) local cricket pitch, swiveled
 
 
The Streak Shadow climbing like a homesick angel.
 
The author (front cockpit) and designer, David Cook, taxi out for the test flight.
 
into wind, accelerated like a sports car (0 to 60 in 3,7 seconds) and was airborne in perhaps ten paces, and climbing like a homesick angel.
By the upwind fence, the Streak Shadow was 'hundreds of feet high, still climbing, strongly, and at an apparently impossible angle.'
A spirited show followed: tight turns, slow orbits, swift high speed swoops, an Airbus-rivaling flaps-down pass under complete control at below walking-pace, glide approaches and zoom climbs.

The eventual landing might have been called short, had it not been undersize for that category; the machine's nose briefly seeming to bury itself in the greensward as it stopped so sharply. But, before we onlookers had time to gasp in amazement, with a quiet howl of power, the nose-wheel lifted back off the ground and the unconventional aircraft was airborne again, in a performance begging re-definition of the term "STOL".

At 50 feet, a wing dipped and this brilliantly agile aero plane completed a circuit barely beyond the boundaries of the small fenced square of grass, to land and turn in less time than it takes to read the words.
 
Five minutes from starting up the nimble little Streak Shadow bobbed and wobbled back across the country cricket pitch, slewed to a halt by its trailer/ chrysalis and chuntered into silence.

The sprightly Streak and its microlight forbear, the Shadow, are stars of a worldwide success story. Their parent company, CFM Metal-Fax, has sold well over 300 of these remarkable machines in 36 countries from Canada to Korea, New Zealand and Australia. License production is now under way in both South Africa and the USA, and they operate on floats in Norway, the Philippines and France.
 
The Shadow is still the only legally approved microlight in Denmark, and it was the first foreign ultralight to be certified in Victoria, Australia. Shadows and Streaks are now employed on such diverse tasks as spotting rhino poachers in Zimbabwe, supporting the World Wildlife Fund in Kenya, cropspraying in Hungary and covert intelligence gathering for NATO in Turkey. THE DESIGNER David Cook, designer of the Shadow family, is a singularly capable man who does not meekly follow convention.
 
His combination of qualifications (pilot, airframe fitter, draughtsman and design engineer) ideally suit him to his job, although he admits he does not have much flight time on propeller aero planes. "In the 1960s RAF, all our training was done in jets," he said. On leaving the Air Force, Cook set about combining his knowledge, experience and desires to produce what he termed "the perfect, maximum pleasure, minimum weight aircraft" In 1981 microlights were simply "funny little single-seat things that fluttered around the field". Drawing on his experience of building and flying a Volmer Swing-wing and VJ24 (in which he made the first micro-light crossing of the English Channel), and excited by the potential of modern, high technology materials, Cook was not content with the rudimentary lawn-mower-engine- and deckchair fly-abouts his contemporaries were fiddling with. He wanted a proper, super efficient, ultra-lightweight two-seat aircraft with conventional controls and speeds of 20 to 100 mph. In his words: "It had to be better than any existing aeroplane or it wasn't worth attempting." He chose tandem seating for his Shadow because this gives good pilot visibility, reduces drag and avoids CoflG problems. The aircraft's unusual ventral fin allows its tail to settle safely when the pilot gets out. To save weight, the crew's seats are part of the structure. He used a side stick and the fuel cock obstructs the big throttle when turned off. Since he was producing an aircraft for anybody to fly, his safety-minded approach included deliberately increasing aileron forces and limiting the original roll rate (which can be restored by a simple modification if Cook thinks the owner with be able to cope). The flap handle is also intentionally made hard to move when above the limit speed. At first Cook was seduced by the promises of Ciba Geigy's Fibrelam, using it for most of his prototype's primary structure.
 
FIRST FLIGHT-JUST
 
In late 1981 Shadow 001 flew-just. Cook recalls the occasion sardonically: "It handled like a rubber band." The experience reinforced his belief that "very few people in this world really know what they are talking about." After demonstrating the airframe's elasticity to CIBA Geigy's "experts", he started Shadow 002 which flew (this time very successfully) a year later. He now derides those who preach the exclusive use of any particular structural medium. Having always been fascinated by materials, Cook insists on the most appropriate one for each application. His Shadow family has components of aluminum, steel, stainless steel, ply-pine, Fibrelam, fibreglass, nylon, expanded polystyrene and polycarbonate. He uses unorthodox off-the-shelf components wherever possible, including flagpole "pulltrusions" for the undercarriage legs, hospital trolley tires and ordinary tea strainers for fuel fillers. Since that first flexible prototype, all airframes have had a main spar of 1,2 mm ply with riveted and bonded top hat section aluminum caps. This slender member is braced by its styrofoam ribs to yield a near-impossible 87:1 strength-to-weight ratio, but none has ever failed. Cook asserts: "Plywood out-performs all modern composites for stiffness to weight at a quarter to a tenth of the price, while the extruded channel was made for truck bodywork so it's dirt cheap. Keeping the thin ply vertical with the ribs is what gives the spar its strength. As an ex-Lotus driver, I know lightness is the key to high performance and good efficiency at minimum cost." The Shadow is the result of a dedicated man's quest for ultimate lightness with strength, maneuverability and exceptional visibility. British Civil Airworthiness Requirements (BCAR) Section S (microlight) rules stipulate a maximum empty weight of 150 kg, but simultaneously demand a strength of + 6 and -3g. "This was a hell of a requirement," Cook said. His was one of very few two seaters to meet the specification, and it has since coped with 7,2g. In comparison, post-war American two-seaters weigh more than twice as much, with lower +4.4/-3.8 g-limits. In 1984, the Shadow was ready for mass production.
 
The type first hit the headlines by exceeding its class FAI World speed and distance records by a full 50 percent. Having won a Mobil design award, Cook teamed with CIBA Geigy's David Southwell to win the 1986 Dawn to Dusk competition. Then Eve Jackson's magnificent UK to Sydney flight gained her the Seagrave Trophy for the most outstanding act of transportation by land, sea or air. At its presentation, Prince Philip said of David Cook: "Behind every great woman there is obviously a great man." In 1987 the Shadow received another award for design excellence. In 1990 Cook broke the UK microlight altitude record at 23 000 feet. More recently, CFM made a special hands-off Shadow for famous paraplegic helicopter pilot, Trevor Jones.
 
STREAK SHADOW
 
The developed Streak Shadow is a higher powered, clipped-wing, Shadow-based kit-built "proper" PPL (A) light aircraft with a thinner wing. It has a 100 mph cruise, a 31 mph stall, and a 30 metre takeoff and landing roll. The company quotes a build time of 500 hours but people do it in 300 and a disabled German built one from his wheelchair. Having climbed a standard Streak to 8 250 metres (27 000 feet), Cook maintains it is the only aircraft to hold records in speed, distance and altitude concurrently. In 1994, also in an unmodified Streak, with an admittedly lightweight 38 kg passenger (an employee), he broke the world class time to climb record to 3 000 metres (9 800 feet) in eight minutes, 55 seconds. He claims no other Rotax powered aircraft will touch a Streak Shadow in any aspect of performance, and delights in accepting head to head challenges to prove it.
 
CARE-FREE AIRCRAFT
 
When I sampled the well-used Streak Shadow prototype, I thought it the most safe and usable of the 150-odd types I have flown. I had never before experienced such a care-free aircraft. It was simple to fly, had excellent visibility, and one could ignore both the ASI and any stalling worries. You just point it where you want to go. Even the CAA's test pilot was unable to stall or spin it, despite making a real effort. Indeed, for me Cook demonstrated a complete circuit with the stick held hard against the back stop4 We took off in around 100 metres and climbed steeply to 1 000 feet, where he throttled back so we flew level (but nose high) around the circuit Then he throttled back further to descend on final to a safe touchdown and a short landing roll. No drama, no fuss. Try that in any other aircraft. (On second thoughts, whatever you do, do not try that in any other aircraft!) I flew the Streak both dual and solo. The cockpit is comfortably snug, with a semi-reclined seating position under a side hinging unbreakable polycarbonate canopy. You soon get used to easing the nose to the ground with your weight as you step aboard. The side-stick and throttle fall neatly to hand. The engine is simple to start and the aircraft is easy to taxi, using the castoring nose wheel and excellent brakes, making it nicely maneuverable.
 
EASY TO FLY
 
The Streak has a maximum 25-knot crosswind component and I flew with a steady 15 knots directly across the runway, without any problems. With a buzz of power it accelerated briskly, leaping oft the ground with a positive rotation at 50 mph after a very short run of perhaps 100 metres. Then you quickly remove the back pressure to establish the climb. The aeroplane climbs eagerly at around 1 100 ft/min dual and over 1 500 ft/min solo at 60 mph. Visibility is truly excellent, completely panoramic in all directions, and rivalling a glider's. The aircraft is stable in the cruise, flying hands off at from 75 to 100 mph without any inputs, thanks to the electric elevator trim. Top speed is 120 mph, and 5 500 rpm gave me 85 mph at 1 500 feet for a consumption of perhaps 12 litres per hour, giving a 375 mile range or 4,5 hours safe endurance. The control forces are reasonable, although the ailerons could be lighter, especially at higher speeds. The roll-rate is OK, but, at four to five seconds to reverse a 45-degree bank, it could also be a little better. With no real definable stall, the minimum possible flying speed (with power) is around 35 mph, with the nose tilted impossibly skywards. Having so little inertia, it does not accelerate much when you head downhill, and so will go where you point it. I experimented with both high and low glide approaches and had little difficulty simply aiming where I wanted to go. The Streak's flaps are hardly necessary, and the handle is perhaps a little more awkward to reach than ideal, but they do usefully increase the descent angle, which can be further steepened by a side-slip. The Streak is tolerant to a variety of speeds on final; glide approaches being just as easy as powered ones. In view of the wind, I flew at 60 mph, but speeds down to 40 are quite feasible. Landing is very simple, with plenty of control authority to push off the drift and hold off the nose wheel for a good, slow touchdown. Roll-out without brakes is perhaps a couple of hundred meters, and half that with them. Touch and goes are a cinch, with near immediate lift-off after applying power. My final verdict of "Extreme ease of control, with a great feeling of safety and most importantly, immense fun" was underlined by Cook's need to send Karen, my wife, out on to the runway, waving her arms to make me land. I could happily have gone on and on all day. The rear seater will find it slightly more difficult to board. He has rather less room, a restricted upward view and a somewhat higher noise level, but Karen enjoyed her 20 minute flight with Cook, saying that, after eight years of getting airborne with me in other light 'planes, "This is what flying should really be like."
 
LIGHTWEIGHT GLIDER
 
Hearing of a US need for an inexpensive two-seat training glider, Cook produced a super-lightweight engine-less Shadow, painted bright pink with yellow stars for maximum visibility. This weighs an incredible 113 kg. "I thought it the most safe and usable of the 150-odd types I have flown. I had never before experienced such a care-free aircraft...." He says that although its lift/drag ratio is not record-breaking, its efficient wing gives it a very low sink rate. His Star Streak project had a 60 hp engine, a single seat and an even shorter span than the Streak. It was highly maneuverable and performed spectacularly but, while his earlier designs were benign, this one required some pilot input so he did not put it into production. An active Shadow Owners Club organizes well attended fly-ins in the UK, and Cook is full of praise for his owners, saying: "Microlight pilots are some of the finest in the world, because they have a better appreciation of the air around them." He points out that CFM Metal-Fax is producing light aircraft in a CAA-approved category to the same high standard demanded of microlights (rather tougher than that required for competing homebuilts since each component has been proof loaded to its ultimate strength). As he said: "Consequently, even with a fleet amassed time of 30 000 hours, there has never been an in-flight structural failure and nobody has even been hurt in a Shadow or Streak". Cook employs 13 people in his British factory for a 25 to 40 aircraft annual output. Much component manufacture is subcontracted and the company could build up to 50 units per year provided only eight to ten of those were fully finished.
 
THE IMAGE SPORTS' PLANE
 
Cook's team are emphatically all engineers rather than pilots, although he has taken them all flying at some time. CFM Metal-Fax's current activity gives Cook little time to progress with his most futuristic project, the matt black Image prototype quietly gathering dust in the corner of the final assembly building. Continuing his crusade for absolute maximum efficiency and performance, this personal sports 'plane has a military power-to-weight ratio. Inspired by photographs of the 1948 Chance Vought F7U Cutlass naval fighter-bomber, Cook chose a similar tail-less configuration for minimum size, weight and drag. Although having a fixed undercarriage for initial trials, he has developed a simple retractable gear. Cook and test pilot Peter Troy-Davies confirm its high acceleration (0 to 90 in four seconds) and great maneuverability, but with a few handling quirks. Nevertheless, Cook hopes that, when refined, the machine will suit retired or would-be fighter pilots. With stability and flutter analyses complete, and a confirmed Vne of 200 mph, he envisages a 100 hp Mid-West rotary or German Zok diesel as its eventual engine, and would like to make a double sized version with a turbocharged Cosworth ex-Formula One racing-car engine to "beat the pants of the Yanks at Reno." Cook's latest project is a side-by-side version of the Shadow. Butthis is currently delayed by the UK authority's refusal to accept it as a modification of the original, insisting on calling it a new design, and requiring all the attendant certification nausea and expense. I predict that if he is able to complete this aircraft to his own exacting standards, it will turn out to be even more popular than its progenitor. The result should be a winner, and I would genuinely consider building one in retirement.
 
Born of a South African father, David Cook still has close ties with the country. His Shadow and Streak are now available there from Shadow Lite cc at Hillcrest, in Kwazulu-Natal. Although unconventional in appearance, his designs are definitely in a class of their own, and some of the most exciting I have encountered. If you get a chance, fly one.