Leland Snow Aircraft Designations

[Apophenia]

Leland Snow Aircraft Designations

I've been trying to sort out the Leland Snow (31 May 1930 - 20 Feb 2011) aircraft designs and their designations. Much of the confusion stems from Snow's S-2 design being built and developed by so many different companies under their own designation variations and names -- Ag Commander, Thrush Commander, Thrush, Bull Thrush, Vigilante, etc.

Immediately below is a timeline of Snow type certificate transfers. Following that will be aircraft designation listings for Snow Aeronautical, Aero Commander, Commander Aircraft, Ayres Corp, Thrush Aircraft, and, finally, Air Tractor.

_______________________________


Leland Snow Model S-2/S2 Type Certificate Transfers

18 Feb 1970 - Snow Aeronautical Company to North American Rockwell Corporation

03 April 1973 - North American Rockwell Corporation to Rockwell International, Albany Aircraft Division

27 July 1973 - Rockwell International, Albany Aircraft Division to Rockwell International, Commander Aircraft Division

28 Nov 1977 - Rockwell International, Commander Aircraft Division to Ayres Corporation

26 Nov 2001 - Ayres Corporation to Quality Aerospace Inc*
-- * Quality Aerospace parent company of Ayres Corp ??

09 July 2003 - Quality Aerospace Inc to Thrush Aircraft, Inc

_______________________________

 

[Apophenia]

Leland Snow Aircraft Designs

Leland Snow - Personal Designs

Texas A&M Ag-1 - 1950 low-wing monoplane, high cockpit, span 12 m, x 1
- Ag-1: Fred Weick's design formed basis for Snow's 1951 S-1

Model S-1 - 1953 low-wing monoplane, fwd cockpit, span ? m, x 1
- S-1: Prototype N4977C, wood structure, aka Snow-1
-- http://www.queenbeeair.com/media/gallery/2008/01/10/snowS1_t_w550_h550.jpg

________________________________

Snow Aeronautical Company - 1958

The Snow Aeronautical designation style followed the style (and numerical sequence) of the original Snow Model S-1 design.

Model S-2 - 1956, all-metal vers. of Model S-1, span 13.58 m
- S-2 : Pre-production version, x 3
-- S-2 prototype lost wings in structural tests, Oct 1957
- S-2A: 1959 prod'n, 1 x 220 hp Continental W670-6A, x 73
-- S-2A retained S-1's fwd-placed cockpit + roll-over bar
-- http://www.pimaair.org/aircraft-by-name/item/snow-s-2a
- S-2B: 1 x 450 hp P&W R-985 Wasp Junior, x 19 built
-- S-2B had rear-placed open cocpit + roll-over bar
- S-2C: Refined prod'n vers. of S-2B, x 214 built
-- http://aviadejavu.ru/Images6/JS/Janes66/2/306-1.jpg
-- S-2C-600: S-2C re-engined with 600 hp P&W Wasp radial
-- Serv-Aero Engineering conv. to 1,200 hp Wright R-1820-71
-- 1973 Marsh S-2C conv. to 575 shp Garrett TPE-331 turbine
- S-2D: Higher MTOW, 1 x 600 hp P&W R-1340-AN1, x 105
-- 1965: S-2D rights sold to Aero Commander Inc (below)

________________________________


Aero Commander (div. of Rockwell-Standard) - 1965

Note that the initial rebranding was as the somewhat over-complicated 'Rockwell 600 S-2D Snow Commander' indicating the horsepower, model number, designer's name, and appropriate Rockwell division. This style was quickly simplified for marketing purposes.

All Aero Commander brandings added 'Commander' names. For unknown reasons, the original designation style shows 'S-2D' as an Ag Commander suffix. For the revised Thrush Commander models, the 'S-2R' designations is applied as a prefix.


Model S-2 - Continued production/development, 1965-1977
- Rockwell 600 S-2D Snow Commander: Initial 1965 desig.
- Ag Commander S-2D: Aero Commander vers. of S-2D
-- Ag Commander S-2D production remained at Olney, TX
-- Turbo Ag Commander S-2D(T): Conv. to PT6A turbine
- S-2R Thrush Commander: 1970 encl. cockpit, P&W Wasp
- S-2R Thrush Commander: 1974 option, Wright R-1300-1B
-- S-2R Thrush Commander production line at Albany, GA

________________________________


Commander Aircraft Division (Rockwell-Standard) - 1973

The revised branding corresponds with the transfer of the S-2R type certificate to Rockwell. The revised designations incorporate horsepower ratings into the popular name.

Thrush Commander series - 1976 Rockwell rebranding of S-2R
- Thrush Commander 600 - 1 x 600 hp P&W Wasp, enlarged hopper
- Thrush Commander 800 - 1 x 800 hp Wright R-1300-1B Cyclone 7
-- S2R-T Turbo Thrush: Marsh conv. to 750 shp TPE331-1-101
- Rockwell MS-2 (M for Mielec-built 600 hp PZL-3* engine)
-- 7-cyl Mielec PZL-3S or PZL-3SR (licensed Ivchenko AI-26V)

___________________________

Ayres Corporation - 1997-2003

Ayres added engine designators to hyphen-less S2R designations. So, the S-2R-1340 was Wasp-powered; S2R-1820 was Cyclone-powered, S2R-T34 was PT6A-34-powered, etc. Although the PT6A suffixes were slightly odd, an even stranger garbling occurred with the S2R-RS3 which was powered by a Polish PZL-3SR.

In Turbo-Thrush designations, the designation precedes the name. However, in popular use, that designation can follow the name which is presented with or without a hyphen. Ayres also introduced c/n 'DC' suffixes (note that DC is for Dual Cockpit, not necessarily for 'dual control'). A 'slash' suffix is also sometime added for hopper size, eg: S2R-T11/400.

Near the end of Ayres, the designation style changed. The S2R-T660 Turbo Thrush was also known simple as the Model 660. In this case, the designation numerals referred to the hopper size in US gallons (a style which Thrush Aircraft formalized). That also applies to the enlarged, Soloy Dual Pac-powered Turbo-Thrush 700 project. However, this Model 700 seems never to have been referred to as a 'S2R-T700'.


Thrush series - Ayres developments of Thrush Commander

Ayres piston engined-powered Thrush models

- S-2R-1340: Ayres vers. of Thrush Commander 600
-- S-2R-1340: 1 x 600 hp P&W R-1340 Wasp
- S2R-R3S : Pezetel Thrush, 1 x 600 hp PZL-3S radial
-- S2R-R3S: Ayres vers. of Rockwell MS-2 Thrush (above)
- S-2R-1820: Bull Thrush, 1 x 1,200 hp Wright R-1820-97*
-- * Along with Cyclone, S-2R 1820 got 500 US gal hopper

Ayres PT6A-powered Turbo-Thrush variants
S-2R-T - Pratt & Whitney Canada-powered Thrushes

- S-2R-T11 Turbo-Thrush: 500 shp PT6A-11*
-- Late S-2R-T11 had 680 shp PT6A-27 fitted
- S-2R-T15 Turbo-Thrush: 680 shp PT6A-15AG
- S-2R-T34 Turbo-Thrush: 750 shp PT6A-34
-- 1977 conv. S-2R-T34 to diesel fuel-approved PT6A-34AG
- S-2RHG-T34 Turbo-Thrush: [?? HG suffix = heavy gear ??]
- S-2R-T41 Turbo-Thrush: 700 shp; PT6A-41
- S-2R-T45 Turbo-Thrush: 1,173 shp PT6A-45
- S2R-T65 Turbo-Thrush: 2-seat drug enforc't a/c, 1,050 shp
-- S2R-T65: Colombian Policia Nacional + fire-fighting*
-- * 8 x S2R-T65s built, aka S2R-T65 NEDS (below)
- S2R-T65 NEDS Turbo-Thrush: 1,375 shp PT6A-65AG, 2-seater
-- NEDS = 1983 2-seat Narcotics Eradication Delivery System
- S2R-T660 Turbo Thrush: 2000, 1,050 hp PT6A-60AG engine**
-- S2R-T660 later becomes Thrush Model 660
-- ** Variant with 1,230 shp PT6A-65AG becomes Thrush 710
- Turbo-Thrush 700: [Project] 1995 enlarged Turbo-Thrush*
-- Turbo-Thrush 700: 1 x Soloy Dual Pac (combined PT6As)**
-- * For "government spraying and fire fighting", 2,650 L
-- ** An off-shoot of early Ayres LM200 Loadmaster devel.

Ayres TPE331-powered Turbo-Thrush variants
S-2R-G - Garrett/AlliedSignal/Honeywell-powered Thrushes

- S2R-G6 Turbo-Thrush : 665 shp Garrett TPE331-1
- S2R-G6 Turbo-Thrush : 750 shp Garrett TPE331-6
- S2R-G10 Turbo-Thrush: 940 shp Garrett TPE331-10
- V-1-A Vigilante: Armoured NEDS for armed strike role*
-- V-1-A Vigilante powered by 1,760 shp TPE331-14-GR
-- * V-1-A (or 'V-1') fitted with 4 x wing pylons

Other Thrush/Turbo-Thrush Conversions

- S-2R-T: Marsh Turbo Thrush conv., 1 x PWC PT6A
- S2R-T : Cascade Aircraft Conversions, Walter M-601*
-- * 751 shp Walter M601 E-11 with Avia 3-blade prop
-- Eg: JAS Ultra Thrush; Johnson Airspray conv., etc.
-- http://cascadeaircraftconversions.com/thrush.html
- S-2R ; Serv-Aero Engineering conv., [engine type unknown]*
-- ICAO desig. SS2T (Serv-Aero S-2R piston conv. is SS2P)
- SS2T Turbo Sea Thrush: Terr-Mar Aviation Scooper waterbomber
-- SS2T: Conv. by Terr-Mar Aviation Corporation, Vancouver, BC


________________________________

 

[Apophenia]

Thrush Aircraft, Inc - 2003-Present

Thrush Aircraft, Inc continued Ayres' post-2000 style of designation based on hopper tank size (in US gallons). So, the Thrush S2R-R1340 Thrush 400 (quickly simplified to Thrush Model 400) featured a 400 US gal hopper. This Thrush designation style has continue to this day.

Thrush Model 400 - Thrush-built Model S2R-R1340
- NB: 400 Thrush refers to Ayres S2R-T34-Turbo

Thrush Model 510 series

Thrush Model 510 - span 14.47 m, 1,930 L hopper
- 510P : Flat-rated 750 shp PT6A-34AG
-- aka 'Thrush 510-34' or 'Thrush PT6-34'
- 510G : 800 shp GE Aviation H80 turboprop*
-- * GE H80 is a Walter M601 development

Thrush Model 550 - span 14.47 m, 2,080 L hopper
- 550P: 1 x shp PT6A-60AG

Thrush S2RHG-T65 Thrush 550

Thrush Model 660 - 2-seater aka S-2RHG-T34

Thrush Model 710 - span 16.46 m, 2,687 L hopper
- 710P : 1 x shp PT6A-65AG

700 Turbo-Thrush, based at the Turbo-Thrush S2R, was intended to fight the fire

________________________________

Air Tractor Inc. - 1972-Present

Air Tractor designations follow the hopper size model ... but only roughly. Sub-variants are number in sequence with no reference to tank size (other than being in the general neighbourhood) - eg: the AT-300 has a 320 US gallon hopper, while an AT-301B holds 350 and the AT-302A holds 385 US gallons, etc.

The Air Tractor designation style explains why there appears to be gap between the AT-802 (820 US gallons) and the AT-1002A (1,060 US gallons). Harder to explain is why these two designations don't begin with 'AT-800' and 'AT-1000' variants. Perhaps these and the 'AT-801' and 'AT-1001' were unbuilt design studies?

Both AT-802A and AT-1002A are the first model - there are no plain 'AT-802' or 'AT-1002'. Perhaps, in this, Air Tractor anticipated future changes to the USAF designation system

AT-300 - 1972-73, 1 x 450 hp R-985-AN1 Wasp Junior, 1,200 L hopper
- AT-300: 1973 pre-series vers., shorter vertical tail/rudder

AT-301 - 1974 Air Tractor, 1 x 600 hp P&W R-1340, 1,200 L hopper
- AT-301 : 1976 series prod'n model, P&W Wasp radial
-- Conv'd to 600 hp Trace OE 600 liquid-cooled V-8 engine
- AT-301A: Released in 1978, minor changes.
- AT-301B: AT-301 with enlarged, 1,320 L hopper

AT-302 - 1977 turboprop vers., 1 x 600-650 shp Lycoming LTP101
- AT-302 : 1977, 620 shp LTP101-600A, some conv. to Trace OE 600
- AT-302A: AT-302 with 385 US gal (1,460 L) hopper
-- Variations in exhaust pipes - straight or upturned

AT-400 series Air Tractors, AT-301 deriv. with PWC PT6A turboprop

AT-400 - 1979, 1 x 680 shp PWC PT6A-15G, 1,510 L hopper
- AT-400A: , 1 x 550 shp PWC PT6A-20, span 14.97 m

AT-401 series Air Tractors, low-wing ag a/c with R-1340 engine

AT-401 - 1986, hybrid of AT-301 powerplant and AT-400 structure
- AT-401 : 1986 Air Tractor, 1 x 600 hp P&W R-1340, 1,510 L hopper
-- Conv'd to 600 hp Trace OE 600 liquid-cooled V-8 engine
- AT-401A: 1991 vers. with 500 hp PZL-3S (licensed Ivchenko AI-26)
- AT-401B: Current, long-winged produc'n vers'n, 1 x P&W R-1340
- AT-402 : 198? vers, 1 x 680 shp PWC PT6A-15AG turboprop engine
-- Conv'd to 600 hp Trace OE 600 liquid-cooled V-8 engine
- AT-402A: 1988 vers, 1 x 550 shp PWC PT6A-11AG* turboprop
-- * Some sources say PT-6A-20
- AT-402B: Higher power, longer wing alt, 1 x 680 hp PT6A-15AG**
-- ** Some sources say PT-6A-20

AT-500 - 1986 AT-400 devel, larger fuselage & hopper, span 15.2 m
- AT-500 : Prototype.
- AT-501 : Production vers., 1 x 600 hp P&W R-1340 Wasp radial
- AT-502 : 1987 single-seat prod'n vers., 1 x PT6A
- AT-502A: [??]
- AT-502B: 1987, 1 x 750 shp PWC PT6A-34AG, span 15.84 m
- AT-503 : 2-seat vers. of AT-502, 1 x 1,100 shp PWC PT6A-45R
- AT-503A: Dual-control AT-503 vers. 14.97 m span AT-401 wings
- AT-503T: Dual-control AT-503 vers. 14.97 m span AT-401 wings
- AT-504 : 19??, 1 x 750 shp PWC PT6A-34AG, span 15.84 m

AT-602 - 1995 AT-503 devel., larger hopper & greater wingspan
- AT-602: hopper 2 385 L, 1,050 shp PT6A-60AG, span 17.06 m

AT-802 - 1990 AT-503 firefighting devel., larger hopper, more wingspan
- AT-802A : hopper 3,028L, 1,295 shp PWC PT6A-65AG, span 18.04 m
-- AT-802A aka 'Air Tractor 802-65' (unofficially)
- AT-802AF: 'Air Tractor Computerized Firegate', span 18.04 m
-- AT-802AF: Hopper 3,104L, 1 x 1,350 shp PWC PT6A-67AG
- AT-802F : Firefighter with Wipaire Fire Boss amphib. floats
- AT-802U : 2-seat surveillance/military operations adaptation
-- AT-802U: 1,424 shp PT6A-67F, armoured engine/cockpit/glass
-- 3,629 kg payload,* opt'l retractable L3 Wescam MX-15Di E/O
-- * 2 x GAU-19/A, 2 x M260 launchers, bombs on 9-15 hard points

AT-1002 - 2009 AT-802 devel., larger fuel & retardant tanks (4,012 L)
- AT-1002A: First flown 25 Nov 2009, 1,600 shp PWC PT6A-67F

________________________________________________________

S Designations - New Leland Snow Designs for Air Tractor

Around 2000, Leland Snow began design of a new range of transports - single-, twin-, and three-engined aircraft. The single-engined S-22 Surveyor high-winged amphibious floatplane seems to have progress the furthest. I've found no details about the twin-engine or trimotor concepts.

In Aug 2001, Leland Snow announced that the US Department of the Interior's Office of Aircraft Services (DOI OAS) had ordered the first S-22. Prof Jan Roskam, now at DARcorporation, says this was "a prototype construction contract". Air Tractor's communications director Kristin Snow (Leland's daughter) confirmed the order, with a then-projected delivery of mid-2004 and a potential total DOI OAS order for 15 Snow S-22 Surveyors.

Kristin Snow -- http://www.ainonline.com/aviation-news/2007-10-17/air-tractor-s-22

Air Tractor contracted "DARcorporation to carry out preliminary design analyses for a range of new, single, twin and three-engined airplanes. With one of these airplanes, the S-22 high wing, Air Tractor won a prototype construction contract from the Department of the Interior. DAR also performed analyses of various other new airplane designs for Air Tractor."

Roskam's Airplane War Stories, Jan Roskam, DARcorporation, Lawrence, KS, 2002, pp 219-220

DARcorporation, a spin-off from the University of Kansas' Department of Aerospace Engineering, develops 'Advanced Aircraft Analysis' software. DARcorporation performed the load analysis for the S-22 Surveyor.

Snow S-22 Surveyor

S-22 - [Project] 2000-2004 10-pax amphibious floatplane transport
- S-22 Surveyor: High-wing config., amphibious floats, 1 x PWC PT6A
-- Some S-22 components completed, potential x 15 DOI OAS order
-- http://www.ainonline.com/aviation-news/aviation-international-news/2008-05-15/works-air-tractor-s-22-surveyor
-- http://www.ainonline.com/aviation-news/general-aviation/2008-06-11/ten-pax-t-prop-works

_________________

 

[hesham]

Amazing work as usual my dear Apophenia,

and I can add for Air Tractor,the S-22;

http://www.ainonline.com/aviation-news/2007-10-17/air-tractor-s-22

 

[Apophenia]

Thanks Hesham ... I'd totally forgotten the S-22 Surveyor! (Now added)

The S-22 creates a new designation style puzzle. While the 'S-xx' form fits Leland Snow's original designation style, this design was being worked on by Air Tractor staff. So, why wasn't the Surveyor given an 'AT-xxx" designation?

And, since three new Snow designs were initially put forward around 2000 ... might we go out on a limb and suggest that a twin-engined 'S-23' and three-engined 'S-24' designations existed as well? ;D