PLANS FOR THE MACDONALD S-21 AND S-22 AMATEUR-BUILT AIRPLANES
Plans are offered - for free - for the MacDonald S-21 and S-22 amateur-built airplanes.
- Complete MacDonald S-21 plans (44 MB download)
- MacDonald S-22 plans, eight sheet addendum to the S-21 plans (11 MB download)
The light-weight S-21 has an open cockpit, an uncowled engine, and a battery-powered radio. It is constructed entirely of aluminum except for the fuselage structure from the firewall to one bay aft of the seatback where chrome-moly tubing is used. First flight was in 1972.
The S-22 is the result of a major rebuild in 2009-10 that incorporated many new features. A sliding canopy that can be opened in flight was installed, as was an electrical system and starter, a cowled engine, and an avionics package. Because of the many changes, the model designation was rolled from S-21 to S-22.
The two aircraft are compared:
| Aircraft | S-21 | S-22 |
|---|---|---|
| Wingspan | 25' | 25' |
| Length | 18' 6" | 18' 6" |
| Seats | 1 | 1 |
| Engine | VW | VW |
| Displacement, Power | 1500cc, 53 hp | 1915cc 65 hp |
| Vstall | 38 mph | 45 mph |
| Vcruise | 90 mph at 3300 rpm | 100 mph at 3000 rpm |
| Vmax | 115 mph | 125 mph |
| Vne (never exceed speed) | 162 mph | 162 mph |
| Rate of climb | 850 ft/min | 850 ft/min |
| Fuel Usage | 3.5gal/hr | 3/0 gal/hr |
| Empty Weight | 462 lbs | 573 lbs |
| Fuel,10 gal @ 6 lbs/gl | 60 lbs | 6o lbs |
| Pilot | 180 lbs | 180 lbs |
| Baggage | 18 lbs | 21 lbs |
| Gross Weight | 720 lbs | 834 lbs |
| Limit Load Factor @ Gross Weight | 4.4 gs | 3.8 gs |
| Ultimate Load Factor @ Gross Weight | 6.6 gs | 5.7 gs |
MacDonald S-21. Photo courtesy of Downey and Associates.
MacDonald S-22. Photo courtesy Steve Berg.
S-21 plans consist of 29 24" by 36" sheets organized as follows:
| Drawing Group | Component |
|---|---|
| 00 | General Arrangement and Specifications |
| 10 | Forward Fuselage |
| 20 | Wing Center Section |
| 30 | Aft Fuselage |
| 40 | Tail |
| 50 | Wing Panels |
| 60 | Landing Gear |
S-22 plans incorporate the S-21 plans and add 8 new sheets:
| Drawing Group | Component |
|---|---|
| 80 | General Arrangement and Specifications |
| 81 | Canopy |
| 83 | Engine Installation and Cowling |
| 83 | Lifting Surface Tips, Wheel/Strut Fairings |
The S-21 appears in an article in the February 1973 issue of EAA's Sport Aviation magazine.
The S-22 is described in an article in the August 2015 issue of Sport Aviation.
The S-22 is currently owned by the Port Townsend Aero Museum, 105 Airport Road, Port Townsend WA 98368. The phone number is 360-379-5244 and the web address is www.ptaeromuseum.com.
The aircraft is maintained in airworthy condition by the Museum staff and is on display there.
- Robert A. MacDonald, designer and builder, September 16, 2021