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CORBY "STARLET", CJ 1
This aircraft is an all wood, ply and fabric covered, single seat low wing cantilever monoplane.
The layout of the 'Starlet' is designed to allow maximum detail variation with little or no change to basic structure. For example: Most existing V.W. powerplants up to 75 h.p., 160 lb. max., may be fitted without basic structure change. Design is drawn around prototype Rollason Ardem V.W. 1600 conversion. Production aircraft engines are not recommended for Starlet due to size and weight limitations.
Basic hardware and materials are to U.S. specifications with alternate British material specs. given where appropriate.
The design has established a reputation for exceptional performance/horsepower capability, being both a very practical cross country machine and a first class aerobatic type.
A. GENERAL HANDLING COMMENTS
In general, the Starlet has typically ultra light characteristics light, responsive controls with seemingly no hesitation between control input and aircraft response. Light and precise, pilot feel is probably more significant than outright experience, and a two fingered approach to flying will ensure the quickest transition to Starlet proficiency. As in all tail wheel aircraft, high speed ground handling should never be taken for granted, though care and respect should ensure no problems as ample directional control is available.
While being responsive, stability is good and all controls have positive and progressive feel.
An important point to be emphasized is that the aircraft is accurately stressed in the semi‑aerobatic (4.5g proof, 6.75 ultimate) category. Any loading over 4.5g must be considered likely to damage the airframe (depending on actual material strengths above minimum specification figures, loading combinations etc.) A 'g' meter is strongly recommended if aerobatics are intended:
Spins are not approved on the aircraft at this time. Recovery from inadvertent spin entry, however, is conventional and should be readily accomplished in 1/3 to 1/4 turn (approximately 200 ft. max.)
Comprehensive testing has indicated all approved maneuvers can be comfortably flown under '3g' maximum loading. Stick force/g ranges from 2.7 lb/g to 4.5 Ib/g over the typical C.G. range (aft. C.G. lower stick force/g). The stick force provides good feel for aerobatics but certainly calls for intelligent respect and restraint to ensure airframe limits are not exceeded.
The current drawing set comprises 17 drawings and 30 pages of builders' notes. The set has been steadily expanded and updated since first flight of prototype in 1966 to include all significant developments in design, engines, equipment, materials and methods.
The Wing, of optional one or two piece construction, is a single spar, 'D' Nose type. The wing main spar is solid spruce built up with 'h" laminations, and varying in both depth and total width from root to tip. Provision is made for center section spar joint fittings which allow wing to be dismantled into two halves of 9ft Sin semi-span.
Wing torsion and for and aft bending loads are reacted by the ply covered 'D' nose structure and transferred at the root section through main spar and leading edge attach. points.
Wing/Aileron sub spars are also of solid spruce, of constant width and tapering in depth. Ribs are of the conventional built up girder type. The wing is fabric covered aft of the main spar with fabric doped on to capstripped ribs no rib stitching employed.
TAIL SURFACES are similar 'to the wing in being of single solid spar design, with ply covered horiz. stabiliser and fin and fabric covered rudder and elevator.
THE FUSELAGE structure consists of built up frame of spruce, completely covered with ply. The fuel tank is mounted between the firewall and instrument panel and beneath forward fuselage decking. Provision is made for shoulder harness installation, and a luggage locker is built into the bulkhead behind the pilot.
MAIN LANDING GEAR consists of spring steel leaf type shock absorbing leg attaching directly to fuselage via a solid spruce/ash beam which also serves as the wing leading edge attach member.
Wheels and brakes are of optional type and size, within limits specified on drawing. A similar steel leaf design is used for the tail skid with or without optional tail wheel. Steel used is a commercially available high grade spring steel.
CONTROL SYSTEM COMPONENTS have been minimized by the use of cables from control column and pedals through to surface control horns. Features of this system are: (a) Elimination of bell cranks, push-pull rods and mount brackets with resultant simplicity and weight saving. (b) Complete freedom from control circuit slack due to accumulation of fitting tolerances and/or wear.
The Starlet design .is type approved in the semi aerobatic category under the requirements of Department of Civil Aviation A.N.O. 101.28. These requirements include full design analysis and comprehensive flight testing. An extensive development program has also been carried out on the aircraft to explore and optimize handling and performance characteristics.
There is no best single seat design for amateur builders, and final choice depends largely on time and money available for project, background and experience for building and flying, and most desired flying characteristics. The Starlet, however, is one of the best and most modern of those available and offers a distinctive combination of building and flying features which is well worth comparison and consideration.
STARLET SPECIFIC CHARACTERISTICS
These remarks are written to provide new Starlet pilots with an idea of the specific characteristics and handling of the aircraft. Assuming the pilot has done a walk around check, and is familiar with the general lay out, physical details, control and instrument positions and limits, notes on a typical check flight follow:
STARTING: Start and run up to suit the particular engine installation. Since hand starting is relatively uncommon these days, it is important to clearly brief helpers if any. Procedure on the prototype when solo starting is to chock aircraft securely and load horizontal tailplane with a sand bag of 25-30 lb. to ensure tail cannot raise after start up, especially if throttle setting is a little on the fast side. A single assistant is preferred to the sand bag to stand just in front of L.H. stabiliser to prevent forward and upward movement, and adjust throttle if required.
GROUND HANDLING: Sturmey Archer brakes are not extremely powerful, but are O.K. for say 2000 R.P.M. magneto check and quite adequate for taxiing. Brakes are not intended for high speed directional control or for high powered braking after touch down. In the first case, rudder power is adequate for control after opening up for take off and in the second, a straight run out using rudder and tailwheel steering only, until speed has dropped to around 15-20 M.P.H. is recommended.
Taxiing is straightforward, with straight ahead vision good, and no need for 'weaving' technique. Braking supplements tailwheel steering for tightest turns. Otherwise, pedals provide direct and light control. Cross winds over 20 M.P.H. have been handled without any problems, though tendency to weathercock becomes noticeable above these speeds. The Starlet, probably because of its compact layout, seems to handle cross winds more easily than many of its contemporaries, and has shown little tendency to raise a wing or the tail in variable ground handling situations.
TAKE OFF: After line up for take off and final control check, aircraft accelerates rapidly on opening throttle. There is a slight tendency to swing which requires minor rudder correction only. The rudder on this aircraft is powerful and best approach is to aim to hold rudder neutral with minor correction of ±5°. An into wind, or calm weather take off is recommended for first flights.
Forward stick may be used to lift tail into flying position, though tail rises almost as quickly with neutral elevator and the aircraft will generally 'fly itself off' with minimum elevator assistance. Acceleration to climb speed (50 KTS. nominal) is rapid and take off and rotate to climb attitude is usually accomplished smoothly with negligible pause for acceleration.
CLIMB: Climb speeds from 45 KT. to 60 KT. I.A.S. may be chosen with little variation in rate of climb. (See Operating Manual for additional notes). Forward visibility is good in all climb attitudes. From 100 ‑ 300 ft. after take off, decelerating main wheels may produce a transient airframe vibration for 3-5 seconds. Degree of unbalance, and any slackness in M.L.G. leg clamping can affect this vibration which may be prevented or stopped by a light touch of brake. Since there is appreciable position error at low I.A.S., 45 KT. is minimum recommended climb speed with 50 KT. normal recommended figure.
CRUISE: The Starlet cruises in a markedly nose down attitude with excellent forward visibility. Once trimmed for owner/pilot weight, by shimming under stabiliser, the aircraft should fly hands off readily, requiring only light rudder as necessary to correct wing low deviations.
Maximum level speed with an optimum prop/typical V.W. 1600 combination may take 1‑2 minutes to reach as engine speed climbs slowly over the top 200 R.P.M.
STALLS: Stall speeds of 30 KTS. I.A.S. (41 KTS. T.A.S.) power off, and 28 KTS. I.A.S. power on are typical. Stall behaviour is excellent with negligible wing drop and 50-100 ft. altitude loss. If wing drop is experienced, it will probably be due to asymmetry either stall entry with some rudder applied, or wing rigging slightly asymmetric.
Stalls out of turns should result in a drop back to level flight with negligible height loss and power on stalls produce a very high nose up attitude with, if anything, less height loss than power off condition.
There is very little natural buffet warning in all stall configurations; aileron control system remains effective under all conditions.
TURNS: Turns in the Starlet, as expected from such a compact layout, can be accomplished in extremely small airspace. Ailerons are very light and powerful, with little adverse yaw at any speed and co-ordinated turns require very little rudder.
APPROACH AND LANDING:
Since the propeller is approximately 25% of span and provides a high percentage of approach drag, rate of descent can be very accurately controlled by throttle position. (Fast idle setting will noticeably decrease maximum rate of descent, e.g. 100-150 ft. per minute.) Typical rate of descent, power off, is 600-700 ft./min. at 55-60 K T S. The aircraft sideslips readily if additional rate of descent is required.
An approach speed of 55 KTS. minimum is recommended and my own preference is 60 KTS. approach, 55 KTS. over the boundary, round out 45-50 KTS., and hold in three point attitude approximately one foot off the ground until aircraft decelerates and touches down on tailwheel 4"-6" ahead of main wheels. Roll out straight ahead with rudder and very direct tailwheel steering no brakes until down to 15-20 M.P.H.
Because of short coupling and large control surfaces both rudder and elevator are immediately effective once power is applied. This characteristic, with familiarity, provides exceptional control and precision in gusty takeoff and go around manoeuvres. Maximum approved cross wind component is 15 Knots.
PRINCIPAL DIMENSIONS AND DETAILS SUMMARY DRAWINGS SUMMARY
Fuselage: Overall Length 14' 9" No. 1 Three view
Maximum Height 4' 10" 2 Perspective cut away and Design summary
Maximum Width 21'/." 3 Fuselage Frame Assembly
Wing: Span 18' 6" 4 Fuselage Bulkheads and Formers
Area 68.5 sq. ft. 5 Fuselage General Assembly
Section NACA 43012A 6 Control System
MAC. 45" 7 Powerplant Installation. Misc. Details
Incidence 21/2° - 1° Tip 7a Powerplant Installation. Misc. Details
Aileron Deflection +12° - 12° 8 Wing General Assembly
Horizontal 9 Wing Aileron Ribs
Tailplane: Span 6' 6" 10 Two Piece Wing Spars, Leading Edge
Area 13.75 sq. ft. 11 Aileron Construction, Controls.
Elevator Deflection +30° - 20° 12 Horizontal Tailplane
Vertical 13 Vertical Tailplane
Tailplane: Area 7.4 sq. ft. 14 Main Landing Gear Leading Edge Attach.
Rudder Deflection 25° 15 Tailwheel, M.L.G. Support Structure
Power Plant: (45‑75) H.P. (130‑160) lb. wt. 16 One Piece Wing Spar
17 Fuel Tank, Canopy Assy. Misc. Detail
Spar Type Item Utility Normal Ref. Arm
Category Category from Firewall
One Piece Aircraft Empty 465 465‑480
July '93 Pilot + Baggage 180 215‑220 40"/55"
or MOD Fuel 50 65 12"
M91‑700 Oil 5 5
MAX. A. U. W. 700 750
Two Piece Aircraft Empty 435‑450 450‑465
or Pilot + Baggage 185‑170 180‑170
Pre July '93 Fuel 40 65‑80
One Piece Oil 5 5
MAX. A.U.W. 665 700
STARLET PERFORMANCE SPECIFICATIONS USING VW 1910cc 70HP ENGINE
MPH KNOTS KM/Hr
MAX. LEVEL SPEED 160 139 257 IAS 3300 RPM
MAX. CRUISE 130 113 209 IAS 3000 RPM
STALL SPEED (power off) 35 30 56 IAS
48 42 78 TAS
TYPICAL RATE OF CLIMB 1100 ‑ 1200 ft.per minute
SERVICE CEILING 14,500 ft.
DISTANCE TO CLEAR 50' 1000' ‑ 1100' TAKE OFF AND LANDING
These specifications are based on information provided by Starlet builders here in the USA who are now flying their aircraft and getting these results or better.
Performance of individual Starlets will vary, depending on the accuracy of construction alignment; A.U.W.; Engine Horsepower, etc;
Since the prototype, Starlets have been fitted with larger capacity VW engines ....1835cc, 2100cc increasing their performance.
Some Starlets can and do, Cruise Straight and Level at Red Line speed, Climb at 1900 ft per minute and flown to 15,000!
The prototype Starlet using a 49hp VW 1600cc engine had a Max. Level Speed of 135mph; Cruise 123mph; Rate of Climb 850fpm. and won the 1973 "A" Grade Australian Aerobatic Championship.
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