Ryan PT-21

The Ryan PT-21 was a monoplane Primary Trainer with seating for an instructor and trainee in inline open air cockpits.  It was fitted with a small radial engine and had fixed landing gear.  It was part of a long line of trainers built by Ryan also including the PT-16, PT-20, and PT-22 for the USAAC, the NR-1 for the US Navy, and the commercial ST series.  Per Reference [8] the base PT-21 was based on the commerical Sport Trainer 3 (or ST-3).   Per reference [8] a 100 of this type were procured by the USAAC.  In addition, the US Navy procured 100 similar NR-1's.

As shown in the images below distinguishing features of this aircraft including;

• small radial engine
  
• inline open air cockpits for the instructor and trainee 
• low-mounted externally-braced wing
• fixed landing gear
  

[Image Sources: Public Domain via Ref [8] - as annotated by this site]

        [Source: Ref [14a] - US Government/Public Domain]

In order to try and better develop weight estimating relationships an effort has been made to estimate the length of the fuselage aft of the firewall, and the length of the engine section forward of the firewall based off scaled drawings.  Together these two distances add to a term called the "structural length" and do not consider any portion of the engine or propeller shaft the extend foward of the fuselage/cowling, or any empennage that extends aft of the fuselage structure.  The drawing below shows the current best estimate of these dimensions obtained from available drawings of the airplane and will be updated with any real world data that becomes available.  For any aircraft with an inclined firewall, an attempt has been made to locate an approximate center of this location.


                                                            Source References [2] [3] & [16]

In the above images, dimensions in Black come from the source material while dimesions in Red have been approximated from the data available.

The table below summarizes the current data collected on this type aircraft, identifying sources for the data

		PT-21	Secondary Sources	Notes
Primary Source		2
No of Crew		2
Engine:
Qty		1
Model		R-440-3
Displacement	(cu in)	440
Power
Military	(HP)
War Emergency	(HP)
Normal	(HP)
Take Off	(HP)	132
Eng Dims
Length	(ft)
Width/Dia	(ft)
Height	(ft)
Base Engine Wt	(lb)
Propeller
# Blades		2
Dia	(ft)	7.58
Manufacturer
Type
Wing
Span	(ft)
Root Thickness	(%)
	(in)
Total Area	(sq ft)	124
Wing (less Ailerons & Flaps)	(sq ft)
Ailerons	(sq ft)
Flaps	(sq ft)
Tail Area	(sq ft)
V Tail Area	(sq ft)
Fin	(sq ft)
Rudder	(sq ft)
H Tail Area	(sq ft)
Stabilizer	(sq ft)
Elevator	(sq ft)
Total Control Surf Area	(sq ft)
Length
Overall	(ft)
Fuselage	(ft)	22.5
Body	(ft)
Body Depth	(ft)
Body Width	(ft)
Fuel Tank Volume	(gal)
Wing Tanks	(gal)
FuselageTanks	(gal)
Oil Tank Volume	(gal)
Water Injection Fluid Tank Volume	(gal)
Wetted Area (sqf)	(sq ft)
Pwr Ldng	(lb/HP)	13.90
Wing Ldng	(lb/sq ft)	14.80
Struct. Des. GW	(lb)	1825
Ultimate Load Factor	(G's)
Design Speed	(mph)
Not to Exceed Speed	(mph)
Total Struct Weight		695
Total Wing		292
Wing
Ailerons
Flaps
Fuselage Carry-Through
Tail		37
H Tail		27
Stabilizer
Elevator
V Tail		10
Fin
Rudder
Body + Eng Section + LG
Body + LG		366
Body		220
Fuselage
Engine Section
Landing Gear		146
Mn Landing Gr		126
Tail/Nose Aux LG		20
Tail Hook
Booms
Nacelles
Total Propulsion Weight		451
Engine w/ Accessories		349
Engine(s) as Installed		330
Accessories		19
Turbocharger(s)
Controls		10
Propeller(s)		46
2-Blade		46
3-Blade
4-Blade
Starting System		10
Water Injection System
Tanks
Piping Etc
Cooling System
Lube System		8
Tanks
Piping Etc
Fuel System		28
Tanks
Piping Etc
Total Sys. & Eqpmt.		122
Instruments		18
Surface Controls		55
Hydraulics
Electrical Equip		3
Electronics (Purple means incl in Furn/Gray in Useful Ld)
Arm Prov/Equipment & Armor
Furnishings		46
Anti-Ice (If not in Furn)
Other /Misc
Hoisting Gear
Floatation Gear
Armor Plate
Empty Wt		1268
Basic Mission Useful Load		567
Crew		400
Equipment
Oil		23
Fuel		144
Fuel & Oil Trapped in Systems
Water Solution for Engine Injection
Bombs/Torp Etc
Radio (if Not Included in Empty Wt)
Nav Equipment
Oxygen System
Armament
Guns & Ammo
Guns
Ammo
Pyrotechnics
Camera
Other
Other Useful Load
Basic Mission GW		1835

Notes: This website has been developed with a number of low cost or free programs including Hot Metal Pro, KompoZer, MicroSoft Designer and Da Button Factory.com

Rev 4-12-26

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