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The Sherwood Ranger

By Paul Hendry-Smith, paulgy80@g-tlac.com

Sherwood Ranger

The Sherwood Ranger was designed by Russ Light during the late 1980s and early 1990s and was the second aircraft design from his pen. Unfortunately Russ did not see the fruits of his labor as he passed away soon after his demonstrator first flew. Following Russ’ passing, the business changed hands but met with little success. Two years ago (2007) The Light Aircraft Company Ltd. (TLAC), based at Little Snoring Airfield in North Norfolk, United Kingdom, took ownership and completely overhauled the drawings, converting them into a usable computer aided design format while revising the part numbering system. But most importantly, the installation of a computer aided manufacturing system and computer numerically controlled (CNC) machining center to produce many of the components has reduced the kit production times by approximately 250 hours.

Sherwood Ranger

Design
The design criteria for the Sherwood Ranger called for an aircraft that did not cost an arm and a leg to own and operate; it had to be easy build, and it had to have the timeless classic lines of a British aircraft. It needed to fly with consummate ease while incorporating a folding wing with trailering capability. But the most important design feature that couldn’t be compromised was to ensure that the pilot have a permanent smile while beating up a few clouds or shooting down that imaginary intruder.
 
Construction
The Sherwood Ranger was designed to be built in a smaller location, such as a single car garage, although a little more elbowroom is undoubtedly beneficial. It can be assembled using readily available portable power and hand tools, although a small drill press and bench-top band saw could make life a lot easier.

Sherwood Ranger

Construction generally begins with building the wings, closely followed by the fuselage, undercarriage, and tail feathers. The kit includes composite items such as the turtledeck, wingtips, fuel tank, cowlings, etc., and whilst to the purist those parts should be made from aluminum or similar, TLAC offers the builder a route to a great-looking aircraft without the need to contract out specialist fabrication companies.

Sherwood Ranger

The wing structure is based around tubular main and drag spars with GL1 (aircraft grade) plywood ribs with capstrips. A new full-wrap leading edge has been employed, speeding up the build process while adding to the appearance, and to the strength of the wing.

Sherwood Ranger

Sherwood Ranger

The airframe structure is made up of aircraft grade aluminum. Round and rectangular tubing and channels are CNC machined for accurate fit. Gusset plates join most of the tubing intersections with AN hardware and aluminum extrusions where loads are concentrated—the framework is self-jigging with the use of Clecos since 99 percent of the holes are already aligned and drilled.
 
The Sherwood Ranger is available in two formats: the 26-foot wingspan version in Europe, classed as a microlight, and the 23-foot clipped-wing version that is a Category A (under 90 knots) or Experimental version. Both models have four half-span Frise ailerons. Although not approved at this time for aerobatics in the United Kingdom, the Sherwood Ranger has an ultimate structural strength of +9g/-4g.
 
Finish
Our demonstrator (G-TLAC) is covered with the Oratex UL600 system. This covering system saved 12 to 14 kilograms (26 to 31 pounds) from the empty weight. Fitted with the Rotax 582 and ready to fly, G-TLAC weighed in at 213 kilograms (468 pounds) with a max takeoff of 450 kilograms (990 pounds), making the Sherwood Ranger capable of lifting more than its empty weight! The Oratex UL600 is a patented covering system containing unique water-based adhesive. The heat-shrinkable covering itself comes with UV protection and color already incorporated, saving massively on not only weight but also the cost of paints and sprayers, the environmental impact of solvents, and the time it takes to cover the aircraft. In fact, the G-TLAC took two weeks to completely cover on a part-time basis.

Sherwood Ranger
Four-cylinder four-cycle air-cooled Jabiru 2200 cc engine.

Engine
Engine options at this time include but are not limited to the Rotax 582, Rotax 912, Jabiru 2200, and some Hirth two-strokes. There are many other potentially viable engine options yet to be explored, and TLAC is always keen to assist builders with their choice.

Kit production is up and running with a lead time of three to four weeks, and at this time we are seeking dealers in North America.

Sherwood Ranger

Performance (interpreted from the company brochure)
The control surface dimensions were designed bearing in mind the requirements for aerobatic operation. The airframe is strong enough to meet aerobatic category requirements at reduced operating weights, that is, single-seat operation; however, certification of a microlight aircraft for aerobatic operation is not legal in the United Kingdom.

During the first 50 hours of flight-testing, the performance of the prototype continued to improve as the engine gradually bedded in and developed more power. Every few hours it was necessary to slightly increase the pitch of the ground-adjustable propeller to prevent exceeding the maximum rpm during full throttle operation. This resulted in a significant increase in climb rate and cruise speed over the initial results obtained during the early stages of testing. The typical performance figures shown below have been based on these results. Where a range is shown the figures relate to minimum and maximum operating weights. More detailed information is shown in the appropriate pilot’s operating handbook supplied with each aircraft kit.

The designer was naturally interested in comparing the Sherwood Ranger’s performance with aircraft of similar weight and engine size, as no doubt will prospective builders. This was by no means easy; obtaining accurate data from manufacturers’ published information proved to be extremely difficult.

Naturally, manufacturers will supply data obtained under the most favorable conditions; however, some of the claims seem to be most unrealistic, a fact borne out by talking to operators of several small kit-built aircraft. In many cases, their aircraft did not appear to perform anywhere near as well as the advertised data suggested. Therefore, when comparing figures for this class of airplane, it would be wise to consider the following points:

  • Treat all advertised data with suspicion. At best they will have been obtained under ideal conditions, on an airplane and engine in peak condition, by a pilot who can fly the airplane to its limit.
  • Ensure that relevant information applies to an airplane operating at maximum all-up weight.
  • Talk to a pilot who actually operates a particular airplane to obtain more realistic information.

As with all performance data, it must be treated with caution as there are many factors that may prevent replication of the original test data.

Comparing speeds quoted as indicated airspeed readings is meaningless unless the position and instrument errors are known. It is easy to position the static source such that the airspeed indicator over-reads by 20 percent in the cruise, and under-reads by 20 percent at the stall.

The figures below are usually quoted as indicated unless otherwise stated, but the static source on the Sherwood Ranger is located such that the position error is negligible at all practical operating speeds.

Performance figures are invariably those obtained under International Standard Atmosphere sea level conditions. Climb performance in particular decreases significantly with altitude and increased temperature.

Takeoff and landing distance should include the distance to clear a 50-foot obstacle, not just the ground roll, and should be obtained using the recommended climb or approach speeds at maximum all up weight. The figures shown below for takeoff and landing distances were obtained in this configuration by an average pilot. These figures can be improved considerably by using short-field techniques.

Although conventional biplanes are usually less efficient than an equivalent monoplane, due mainly to interference effects between upper and lower mainplanes, the overall performance of the Sherwood Ranger is at least as good as, if not better than most airplanes in this weight category, including monoplanes. Ian Barr, an experienced pilot and instructor who has flown a large variety of modern lightweight airplanes, confirmed this fact. He commented, “This is certainly the nicest airplane I’ve flown, and far more efficient than I had expected.”

Further improvements are possible by simple modifications to reduce drag. These will be in the form of small lightweight fairings fitted to various areas and will be retrofittable to all aircraft.

The interesting numbers are:

External dimensions and areas

Wingspan

7.92 meters, 26 feet

Length

6.1 meters, 20 feet

Height

2.24 meters, 7.3 feet

Constant chord

1.0 meter, 3.3 feet

Dihedral

3 degrees (lower wing only)

Sweepback

3.8 degrees

Total wing area

15.6 meters², 168 feet²

Aspect ratio

7.92-to-1

Wheel track

1.34 meters, 4.40 feet

Wheel base

3.65 meters, 12 feet

Main wheels diameter

Overall 33 centimeters, 13 inches

Tail wheel diameter

Overall 20 centimeters, 8 inches

 

 

Powerplant options

Rotax 582

65 hp two-stroke

Jabiru 2200

85 hp four-stroke

BMW R100

70 hp four-stroke

Rotax 912 (under investigation)

80 hp four-stroke

Fuel capacity

43 liters, 9.5 Imperial gallons, 11.3 U.S. gallons

 

 

Weights and loadings

Empty weight

182 kilograms, 400 pounds

Max takeoff weight

450 kilograms, 992 pounds

Payload

268 kilograms, 590 pounds

Load factors

+6, -4 ultimate

 

 

Performance

Max level speed

80 mph

Never exceed speed

100 mph

Economic cruise speed

55 - 80 mph

Stall speed

41 mph

Max climb rate at sea level

800 feet/minute (engine dependant)

Service ceiling

N/A

Range at average cruising speed

200 miles

For more information visit www.G-TLAC.com.

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