PT-20 (oz12013)

About this Plan

PT-20. Radio control trainer model for .20 engines.

Discontinued kit from Great Planes.

Originally published in RCM, the Stu Richmond designed PT-20 (oz8014) trainer first appeared in September 1985, RCM. This here is the PT-20 design as later kitted by Great Planes.

Note this here is the original Great Planes PT-20 plan, the PT-20 Mk I, so to speak. The later Mk II version has substantially different construction (interlocking I-beam style wing, no turbulators, etc).

Scan from PGregory, cleanup by Circlip.

Direct submission to Outerzone.

Update 09/08/2018: Added kit review from RCM August 1987, thanks to RFJ.

Quote: "RCM Product Review: Great Planes PT-20.

The PT-20 (Perfect Trainer 20) is one of the most recent kits produced by Great Planes Model Mfg Co. The designer's objective was to create an ideal model for the person with little or no experience in building or flying R/C models.

The most prominent construction features are illustrated by photos on the sturdy, colorful, box. All wood parts are neatly packed in the box to prevent damage, and all hardware and small wood parts are in plastic bags. A complete parts list is on the back of the instruction book.

Construction: Okay, now let's get to work! The first step, of course, will be to thoroughly review the plans and instruction book, as well as the contents of the kit. The 41 page instruction book is certainly one of the outstanding features of this kit. It contains 116 photographs, plus many drawings, to illustrate each step of the construction. Sections on covering, radio installation and operation, flying and troubleshooting, a list of tools and additional items needed to complete the plane, and even a glossary, are included. In short, it is an excellent book for beginners.

The detailed 55 x 34 in plan sheet has full size drawings of the fuselage, wing, and tail, as well as three different engine installations and two different radio servo tray installations. Since radio and engine installation will vary slightly according to the brand selected, these items should be on hand before starting construction.

The quality of all wood parts, as well as their accuracy and proper fit, receive an excellent rating. All balsa parts are sawed and sanded to proper outline and the wing leading and trailing edges are preshaped and notched for the ribs.

Cyanoacrylate (CA) glues are recommended except for joints which take extra time for proper alignment. Here epoxy glue is suggested. If eye or lung irritation is encountered while using CA glue, white glue such as Elmers or Titebond may be substituted. Strength will not be sacrificed, though building time will be slightly increased.

The fuselage is of typical box construction with 1/8 plywood doublers at high stress areas, ie forward fuselage, top of fuselage below wing, main landing gear area, and tail area. The fuselage bottom, forward of the main gear, is 1/8 plywood. The result is a very strong, yet light, fuselage.

Before starting wing construction you must decide whether or not ailerons will be incorporated. The only difference in basic wing construction is the dihedral angle. All parts and detailed instructions are included for either version. If the wing without ailerons is selected, you may incorporate ailerons later, since that change is also included in the instructions. Wing construction is quick and easy, thanks to the shaped and notched leading and trailing edges.

Tail surfaces are 3/16 sheet. Simply glue the parts together per the instructions.

Covering: The covering material suggested in the instructions is Super MonoKote, so we selected white and metallic charcoal for our model. Covering instructions are provided in the instruction book as well as with each roll of MonoKote.

Engine: The engine selected for this review model is the new K & B Sportster .20 R/C, No.5600. This engine is very quiet and powerful, with excellent throttling capabilities. It also has the unique feature of a radial 'spider' mount which accommodates nosewheel steering. A special nose gear to fit this engine may be ordered from Great Planes for $2.00. A Sullivan SS 4 ounce tank fits easily in the tank compartment, with access provided by a hatch on top of the compartment.

Radio: A Futaba J Series radio, using three channels, provides the control for rudder, elevator and throttle. With servos installed at the forward end of the radio compartment, per the plans, the receiver and battery pack must be placed below the pushrods. This may be difficult, depending on the amount of padding used. By placing the servos .aft, there is plenty of unobstructed room in the forward part of the compartment, and the CG location will hardly be affected.

Flying: The CG was at the proper location with no balance weight necessary. Control surface throw was set per the instruction book. After a brief taxi, to check steering sensitivity, it was time for the flight test. Three flights were made in quick succession with no problems whatsoever encountered. No snap roll tendencies were noted during stalls or steep turns, even with full up elevator. Take-offs and landings are the easiest we've made in quite a while, thanks to the PT-20's stability. With a slight increase in control throw, loops and barrel rolls are simple. The engine performed flawlessly throughout these flights, though we ran out of fuel once and found out that the PT-20 also has an excellent 'dead stick' glide.

Conclusion: The PT-20, with its construction features, instruction book, and excellent flying characteristics, may be as close to a perfect trainer as it is possible to buy in its size and price range. It certainly qualifies as an excellent choice for a first R/C airplane."

Update 13/05/2020: Added kit review from MAN December 1986, thanks to RFJ.

Supplementary file notes

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