Model history

The Development of the the SA102.5 Cavalier & Other Cavalier Models

The first article here is by Simon Bugg, and farther down is text by Stan Mcleod with more on the 105, 103, 104.

The original inspiration for the SA102.5 Cavalier was the GY-20 Minicab.

The GY-20 Minicab is a small side by side, two seat monoplane originally conceived in France by Yves Gardan. It is constructed of wood with a fabric skin originally powered by a 65HP Continental engine. The prototype first flew in 1949. Eventually, the plans were translated from French to English and made available for amateur builders.
Cavalier SA102.5

The SA102.5 Cavalier is a much modified and refined development of the GY-20 Minicab. It is in the same French tradition, as the Jodels, the Emeraudes, and other fine wooden aircraft from Europe, but designed in Western Canada by Stan McLeod. The first flight of the prototype SA 102 was made in 1964 and subsequent development (such as the addition of tip tanks) lead to the first flight of the SA 102.5 in February 1971.

Basically, a SA102.5 Cavalier is a two-seat (side by side) cantilever low-wing monoplane. The wing section is a NACA 23015 at the root and NACA 23012 at the tip. The wing structure consists of a single wooden box spar, plywood leading edge, and an auxiliary rear spar to carry the flaps and ailerons. The centre section and leading edge of the wing is plywood covered, the remainder covered with fabric. The fuselage is a wooden truss type structure of spruce and birch ply construction. The cockpit doors and canopy are of fibreglass. The rear decking is fabric covered as are the control surfaces. The standard aircraft has a fixed tricycle under-carriage with spring steel gear legs. Fuel is carried in wing tip tanks of up to 22 Imperial gallons capacity. Engine options range from 85 hp to 135 hp.
The Cavalier was designed to:
- be buildable by amatuer builders
- be affordable to build and operate
- be servicable and easliy maintained
- be a reasonable performer on 100 to 135 hp
- to operate well off 2500 ft grass strips
- to operate safely from high density altitude airports
- be safe for the "low time" pilot who has not flown for 10 years
- be an overall attractive and safe aircraft
...the Cavalier is not a race plane and was never intended to be.
Specifications with a 125 hp Lycoming O-290 engine : 
Span    27' 4"
Length    22' 0"
Wing Area    118 sq.ft
Weight empty    1,050 lb
Weight loaded    1,650 lb
Wing loading    12.7 lb/sq.ft
Max. speed    150 mph
Cruise speed    130 mph
Stall speed    50 mph
Climb    1,000 fpm
Range    715 miles
Some Notes from the Designer - Mr Stan McLeod (April 2004)

SA102, SA102.5, SA 103, SA104 Cavaliers and SA105 Super Cavalier
The Cavalier started life as the SA102 Cavalier and the prototype; built by Forest Fenton of Calgary, flew with 135 hp Lyc in 1963. This was a fairly basic machine by present day standards but was the aircraft that proved the "Rod Nose Gear" could be made to work (others had tried and failed). The original prototype just plain wore out, was rebuilt and I believe still exists. Could use engines from 85 to 135hp, could be built as tri gear or tail dragger and was easily convertible from one to the other.
NOTE: the tail dragger turned out to be around 15 mph SLOWER than the tri gear and didn't handle rough fields any better than the tri gear; however both offered excellent handling on the ground. Some builders demanded retractable gear for the Cavalier and this was not practical so I spent some 4-5000 hrs designing a new airplane with retractable gear - the SA105 Super Cavalier.

SA105 Super Cavalier (1968)
This airplane follows the same basic construction pattern as the SA102.5 but is beefed up to;
1) take larger engines and variable pitch props from 125 to 200 hp, including auto conversions
2) withstand the higher gross weights necessary
3) withstand the higher stresses of the higher cruising speeds
4) enlarged cockpit
    a) to house two people comfortably for long cross country flying
    b) more radios and instruments for x country and IFR flying
    c) provide room for the retracted nose wheel and pilots/pass, legs
    d) added baggage space necessary for x country travel
5) fuselage is 4" wider and 4" taller than the 102.5 and 7" longer
6) wing structure is beefed and modified to accept retractable gear and mechanism
7) tricycle landing gear is all spring steel and manually retracted similar to the early Mooneys. hydraulic retraction can be adapted quite easily
8) streamlined fibreglass tip tanks are added to remove all fuel from the cockpit and increase the aspect ratio and wing area (these tanks produce lift and reduce drag).

SA102.5 Cavalier "1/2- SA102 and 1/2- SA105" (1969-70)
I purchased an almost complete SA102 (which incidently was mostly built in the basement of an hotel in Banff Alberta, by Merton Eldridge who was the accountant in the hotel) and produced the

The SA102 is restyled to incorporate;
1) the Tip Tanks from the SA105
2) windows behind the seat
3) various simplifications and construction improvements
4) elimination of the tail dragger option (due to low speed and no better ground handling, or rough field capability)

Styling Revisions (1972);
1) revised landing gear mounting to eliminate/simplify fittings and make legs easier to make
2) revised nose gear mount to allow the aircraft to be moved on it's gear with the engine removed and to simplify the engine mount

Major Styling Revisions (1988);
1) restyled tip tanks
2) flaps changed from split to "simple" type 15,30,45,60 deg.down and -8 to -12 deg. reflex capability for up to 15% higher cruise
3) restyled stabilisor and fin tips
4) "Fighter Canopy" - all new, front hinged, lift up canopy with fibreglass frame - 2 styles to choose from

SA103 & SA104 Cavaliers (1988)
SA103 is a "Fixed, spring steel gear Tail Dragger", aircraft, based on the SA105 airframe
SA104 is a fixed spring steel Tri Gear aircraft based on the SA105 airframe
The SA103 and SA104 can use aircraft or automotive engines from 125 to 200 hp.
All four Cavalier aircraft "appear" very similar and are hard to tell apart visually.

A second Cavalier history time line:

Started in 1963 as a Tri Gear or Tail Dragger "Interchangable". Fairly primitive: 19 sheets of plans.

Larger - longer, more powerful - Tri retractable spring steel gear and tip tanks: wider deeper fuselage for more comfort, room for nose gear (retracted) and NAV. equipment for 2000 mph + X country  travel 150 - 200 hp (Javelin Ford OK).

1968 - SA102.5 - 1/2 SA102 AND 1/2 SA105
Adapted rear windows of SA105 and tip tanks of SA105. First flew my SA102.5 Cavalier in 1970, no TT. Flew with TT in 1970 * see old N# letters (with plans) for comparison.

1972 - SA102.5
Simplified main gear mounting and changed nose gear. Mount to f'wall (was on engine mount - hard to build mount, aligning engine
gear etc. Also, gear came off with engine mount, so it was harder to move a/c w/o nose gear - new mount corrects this. In 1972, all AFT fuselage reinforcement for tail wheel mounting and stresses were removed from SA102.5 . The tail dragger SA102.5 is 15 mph slower than the tri gear, but does handle exceptionally well on the ground - no bad habits as long as wheels are aligned properly (towed out 2 - 4 ) I've flown several. Tri gear handles as rough or rougher fields, because main gear is near C of G and nose wheel can be - must be - shall be - "is" held "up" to about 30 mph. The nose wheel is for taxing on (0-30-30-0 mph). "Keep the stick/wheel back until the a/c is parked". I've flown a couple of tail draggers and no complaints except the reduced cruise caused by: High drag tail wheel vs low drag nose gear which is tucked in turbulence air right behind the prop, which reduces extra drag of fat legs and wheels farther AFT in other types of aircraft.

Tri gear - main wheels should have zero tow in/tow out normal gross WT with wheel sitting on a greased plate.

New main gear Eliminates top bend in gear leg and simplifies gear mount and eliminates welds - rib "A" is tipped INBD at the top so gear leg and fittings bolt flat against, it.

1978 -
Clarified man/ details and Re: Dew many Dwgs - Dwg #2 became 2-2A, 2B, 2C, 2D all 24 x 36"; all this was ONE 24 x 36"! • originally.

1988 -
New Flaps + 12 50 45 (mine to 60), simpler flap system. New wing mounting' eliminates 4 fittings - bolts, nuts, weight and welding. Sew style T.T. , new fin cap. , many detailed improvements - nearly every drawing had some change. New STAB tips. NOTE: DWG SA102.5-2578 means it was modified in 1978. SA102.5-48? was modified in 1987 etc.etc..

- will be a fixed gear tail dragger. SA105 air frame with SA102.5 TYPE legs.

SA104 - CAVALIER - Fixed Tri Gear SA105 airframe.

SA103 & SA104 plans will eliminate details necessary. for SA105 RET gear.

Some want them - stick suits a/c better.
CESSNA: 120 - 140 - 150 - 152 systems fit - main tube (vertical)
is shortened approximately 4", other Cessna systems can probably be
GRUMAN - Controls reportedly fit without modification.
Cessna or Gruman rudder pedals fit with little or no modification.

The first of this series of aircraft is the SA105 Super Cavalier. This aircraft was designed due to the demand. For retractable gear in the SA102 Cavalier. In order to fit retractable gear AND people, plus radios and instrumentation appropriate to faster, long range flying, THE COCKPIT HAS ENLARGED. To accommodate higher horsepower engines and C/S props, which make retractable gear with while in performance, the fuselage structure was beefed up and lengthened, rear windows and a hat rack were also incorporated. In order to accommodate retracted wheels in the wing, spars were rearranged and strengthened. To strengthen the wing by better load distribution, as well as added safety of removing fuel from the cockpit area, TTP tanks were added - these tanks added wing area, lift, reduced drag and higher aspect ratio and thus added to the rate of climb, the cruise speed and lowered the stalling speed. Next came a larger fin and rudder.
The landing gear design itself took several hundred hours of work - seven different gears and systems were investigated, the seventh and first combined to become the gear system chosen - this is shown on 10 - 24 x 36" drawings with all parts drawn full size - the gear - a 3/4" spring is sht»e>n clearly in the accompanying 3 view and is operated A La Mooney, with a mechanical system - hydraulics can a have been used by builders and an electric system of retraction extension could also be easily used. The nose wheel is free castering allowing very easy maneuvering, with steering by differential brake. The nose gear is mounted at the fwd bottom of the firewall and retracts AFT on the center?4?'?''^into a box between the firewall and front of the seat. The main wheels retract inboard between the spars and just outboard of the fuselage, the gear is locked down by over center locks - wheels and tires are (3) 500 X 5 with hydraulic, toe operated disc brakes. Doors cover the retracted legs and wheels. All of these modifications led to a new airplane "The SA105 Super Cavalier" . The tip tanks rear windows and hat rack etc. were retro fitted to the SA102 making it the SA102.5 Cavalier (1/2 102 & 1/2 105).

NOW- 1996
To accommodate larger folks, more available larger engines and more powerful automotive conversions and to offer builders more options, I have completed the SA103 and 104 conversion of the SA105 airframe. The SA103 Cavalier is a fixed tail wheel version of the  SA105 airframe. The original design of the SA105 dates to 1968.

The SA103, 104 Cavaliers and SA105 Super Cavaliers are basically all wood aircraft, using sitka spruce for the basic structure, some hardwood (ash) for reinforcing blocks, and various thickness"s of birch plywood for gussets and skins. The structure is then covered with 2.7 oz. to 3.8 oz. Dacron fabric and one of the many new paint systems (mostly polyurethane). Compound items such as cowls/ spinner, canopy, fin fairings, tip tanks, wing tanks, gear doors are composite construction flaps maybe constructed with
wood/plywood or composite construction. The major components are joined with relatively simple fittings and bolts. The engine, gear, wing, tail etc. , can be quickly dismantled or re-assembled.

The fuselage is a simple four longeron box, with interior of the cockpit lined with plywood . Basic materials are 25mm x 25mm (l"sq.) and 3/32" 5 ply birch plywood. The fuselage sides are made in a jig and then joined together by
means of bulkheads and diagonal members. The basic rectangular fuselage box is built upside down and when completed, set right side up and the fin and upper fuselage section added. The front section is all ply covered inside, and the turtledeck, aft of the
cockpit one bay, is ply covered and reinforced to provide passenger protection in case of a roll over - the remainder of the turtledeck is fabric faired by stringers. Rear windows are let into the _ turtledeck for two bays behind the seat, this lets in lots of light and allows excellent rearward visibility - you can look back and see the stabilizer.

The fin is a swept, two spar, ply covered structure built integral with the fuselage. The fin rear spar forms the rear bulkhead of the fuselage and provides mounting for the rudder. The graceful fin leading edge is simply formed with a 2mm (3/32") plywood center core, and 2" polyurethane foam blocks glued each side and sanded to shape. Two layers of 6 oz. fiberglass provide the necessary protection for the urethane foam. We suspect this is the granddaddy of all the composite aircraft. The stabilizer is mounted in a slot below the fin, the bolts directly to reinforced top longerons by four bolts, (no metal fittings are required). The rudder cap houses the strobe and white tail light - the rudder cap and stab tips are faired (foam and glass) for appearance and drag reduction. The wing likewise fits into a slot in the bottom of the fuselage and bolts to bulkheads at front and rear by 4 bolts, the wing is easily removable.

Two options are offered - a lift up "Fighter Type" as shown in the side view and a "Double Door" version as shown in the top view. Both types are constructed using moldless composite construction. Both are air and water tight - step by step mold and construction instructions are in the plans manual. The door style consists of 2 composite doors molded as part of the canopy and cut out later (ensuring a perfect fit). The doors are cut inboard almost to the center line making entry and exit easier - doors are hinged at the front and operate like a car door. The "Fighter Type" canopy is all one piece and is hinged by two hinges, reinforced structure just behind the firewall. The canopy laps over the top longerons and seat back to make a water and airtight seal. The canopy is lifted by a handle between the seats at the seat back - lifting this handle lifts the canopy to a near vertical open position. The handle now locks over center to hold the canopy open for easy entry/egress. The canopy is lowered by pulling the handle full down to an over center down lock position. An exterior handle and lock are also shown.

The wing, 25'8" span, is basically a mono spar wing with a built up box spar and plywood leading edges, forming a very strong "D" nose section. A light rear spar serves to carry aileron and flap loads. A diagonal drag spar of "I" construction runs between front and rear spar and carries drag loads. The entire center section of the wing is plywood covered and contoured to serve as the seat. The wing ribs are routed or sawn from Marine grade fir plywood and are thus simple and inexpensive. All ribs, formers, etc, are shown full size on the plans.
Ailerons are ample area and are of the slotted Frieze type offering light positive aileron control at all speeds including right into the stall. Five flap positions are used, 15, 30, 45 and 60 degrees, and 8 to 12 degrees "up" flap, these are mainly effective in lowering the approach and landing speeds, the up or negative flap gives 10 - 15% more cruise speed. Flaps are of the simple type and of composite construction.Flaps have inboard and outboard fences to prevent air spillage at the root and aileron, especially in neg. flap cruise mode.
Flaps operated by convenient handle between the seats and a simple torque tube system. A composite flap shroud covers the sing - flap - gap in all flap positions H- 12 degrees to 60 degrees.

SA105 Super Cavalier - Tri-spring steel mechanically retractable gear as shown on the 3 view. The SA104 Cavalier is unusual in that it is much faster (10-15mph) than the SA103 tail dragger (equivalent power, etc.) and will handle rough fields equally well. The SA104 Cavalier has fixed tri-cycle gear spring steel, main gear using 5/8 x 5 (tapered) flat spring steel legs of 6150, 5160 or 4440 truck spring material and can be manufactured by any truck spring shop. The nose gear is a 1" diamater spring rod of the same material - with a simple free pivoting fork and 500 x5 flat faced tire. Steering is poy differential brakes, much quicker, more positive, smaller turning radius's are possible with this gear. Main wheels maybe 500 x 5 or 600 x 6 with low profile tires and disc brakes the SA103 Cavalier - is a fixed tail dragger - this a/c uses the SAME, main gear legs as the SA104 Cavalier but mounted on brackets to the front of the main spar, placing the axle/wheel center line 8" ahead of the balance point, 600 x 6 wheels with low profile tires and disc brakes.
The tail wheel is mounted to the reinforced AFT fuselage and uses Taylor-craft, piper or other light aircraft tail wheel springs and an 8" inflated Scott or Maule tail wheel. The main gear attaches to a heavy rib on the AFT face of the front spar with simple 4130 brackets and bolts. The nose gear mounts to the front bottom of the firewall and remains attached even if the engine is removed. ???

The nose gear mounts directly to the firewall and bottom forward fuselage by a simple fitting. The gear leg slips into a socket and is secured by two bolts. The engine and mounts can be removed without affecting the nose gear or vice versa. This type of nose gear produces little drag due to being directly behind the prop and in fairly turbulent air and also being of relatively small frontal area. This nose gear handles rough fields by being able to flex fore and aft, up and down side to side and the nose wheel can also swivel. Notice more and more designers are adapting this nose gear which we perfected on the prototype Cavalier in 1963. As well as the nose gear being tough and flexible we help it out by keeping the main gear just 8" behind the center of gravity - this does two things.
1. Reduces the weight on the nose gear
2. Allows the stick/wheel to be held back on landing and thus keeps the nose wheel up longer and less weight on it.

The nose wheel can be lifted quickly on take off and held off to 25-30 mph on landing. Wheel parts can be added for aesthetics and 5-6 rnph for a well fitted set.

The stabilizer and elevator are of conventional construction with "I" spars and plywood ribs. The entire stab, is covered with 1/16 birch plywood and the stab, and elev. are both finished with a covering of dacron. An ample, simple, adjustable trim tab is set into the elevator trailing edge to make adjustments for load changes and power changes in flight. This trim tab is operated by the light weight economical Menzimer (a Cavalier owner) "MAC S4 Trim Servo".

The major assemblies of the aircraft are joined by bolts and steel fittings, all bolts and hardware used are "AN" and available at any aircraft supply house. Fittings are made of standard sizes of 4130 stell with a minimum of frills, bends or welds, keeping the limited shop facilities of the homebuilder in mind. There are now several shops who will manufacture Cavalier fittings on order at reasonable prices.

The SA103, 104 and 105 Cavaliers carry all fuel (38 gals.) in fiberglass tip tanks, mounted via bolts to the wing tips. Each tank holds 19 gallons and is fed to the engine 1.) via gravity 2.) tanks are ram pressurized in flight. 3.) an electric pump and or 4.) engine driven pump. Baffles in the tanks prevent sloshing. If the builder wishes, approx. 10 gal. tanks maybe installed between ribs Y and-10. Tanks maybe selected left, right, both or off by a 4 position selector mounted in the center console just ahead of the spar. Tip tanks eliminate all fuel from the fuselage, leaving more space ahead of the instrument panel for radio and instrument installation and more space behind the rear seat for baggage or a jump seat (max 200 Igs.). Full size dwgs. for the tip tanks are included.

The SA103, 104 and 105 aircraft can accommodate a large range of engines from 150 to 200 hp. , 4 cyl. aircraft or small automotive V-6's, Suburu's etc. The SA103 and 104 will give good economical performance with 150 - 180 hp. The SA105 is best suited to 180 - 200 hp.

Wing span
Wing area incl. tanks
Aileron Area
Flap Type

Flap area
Wing Airfoil- Root
Washout 2.30 Rib
27' 4"
117 sq.ft.
9.36 sq. ft
simple reflex
15,30,45,60 degrees DN, 12 up
10.8 sq. ft.
NACA 23115
NACA 23010
0 to 5
6 degrees
23' 9 1/2" (varies w/ engine weight)
Length - along top of seat
Leg room
Height at seat back
Width inside
SA103 - 104


Stick or wheel (Dual)
Dual wheel
Dual pedals and toe brakes
Conventional - throttle, pitch, mix, carb. heat.
Simple manual (Electric or Hyd. opt.)
SA1Q3 - 104





Use interchangeable main gearLegs - 5/8 x 5" tapered spring steel
1" dia. spring steel
500 x 5 free swiveling
3/4" x 3" tapered spring steel
1" dia. nose gear
500 x 5 wheels
600 x 6 c/w Lo profile tires
8" inflated tail wheel
500 x 5 opt. 600 x 6 Lo profile
500 x 5 nose wheel
Rudder Area
Rudder Travel
Elevator Area
Elevator Travel
Trim Tab
Stabilizer Area
  7.15 sq.ft.
20 degrees L & R
 9.06 sq.ft.
20 degrees DN 27 1/2 degees up
39sq." Travel + 15 degrees
10.36 sq.ft.
SA103 - Empty Weight
SA103 - Gross Weight
SA104 - Empty Weight
SA104 - Gross Weight
3A105 - Empty Weigh
SA105 - Gross Weight

* The weights will vary slightly with engine and propellor options

Tip tanks only 34 Gallons
Aux. tanks (rib-7-10) 22 Gallons


* At full gross with 56 Gallons or fuel

1050 Ibs.*
1850 Ibs.
1100 Ibs.*
1850 Ibs.
1175 Ibs.*
1850 Ibs.

204 Ibs.
132 Ibs.
336 Ibs.

340 Ibs.

130 Ibs.*
80 Ibs.*
0 Ibs.*
Performance @ 1850 Ibs. @ Sea level

Take Off Distance
Initial Climb
Cruise @75%
Max Diving Speed

Take Off Distance
Initial Climb
Cruise @ 75%
Max. Diving Speed

Take Off Distance
Initial Climb
Cruise @78%
Max. Diving Speed

Stall Speed - No Flap
Stall Speed - 45-60 Degrees Flap
Take Off Speed
Take Off Speed 15 Degrees Flap


  125hp  150hp  180hp 
  1000ft.  800ft.  600ft. 
  6-700 900-1000  12600  FPM
 140-145  150 160
  240  240  TAS

 1000ft.  800ft.  600ft. 
  6-700 900-1000 12-1300  FPM
 150-155  160  165  TAS
  240  240  240  TAS

  150  180  200 
  800ft.  600ft.  600ft. 
 900-1000 12-1300 12-1300  FPM
  175-180 190-200 190-200  TAS
  240  240  240  TAS
60-63 IAS
55-68 IAS
60-63 IAS
55-58 IAS