Sikorsky models and designations

[boxkite]

Sikorsky seems to be a special case among the US companies: Besides the S-… series and military designations not any project/design number of a ‘paper helicopter’ is known to me. At least three unbuilt projects got S-… numbers

- S-57 as a XV-1 and XV-3 competitor,
- the Cheyenne rival S-66, and
- the US Army funded AARV S-68.

Otherwise they gave them abbreviations of the programs (ACA, LHX, ABC -> see attachment from “Air Progress” June 1968 “Army squad carrier proposed by Sikorsky calls for contra-rotating, twin-rotor rigid units on a common axis. Designated "ABC" for advancing blade concept”), but these couldn’t compare with type designations used by other aircraft manufacturers. Btw, I don’t know any special book about Sikorsky helicopters (e. g. there is no Putnam publication). WHY?

Scott and Evan, do you see a chance to wake up Sikorsky’s archivists?

 

[lark]

The same illustration appeared in Aviation Week & Space Technology
of January 19,1968 with the caption : (UTTAS) squad - carrier heli.

Confusing indeed...

 

[Skybolt]

Add the S-63 from 1957/58 (no more details chez moi) and the S-71 (AAH competion)
When Sikorsky was part of Vought they used the VS-XXX designation type. Some early helos have a double designation, VS- and S-

 

[boxkite]

Skybolt, thank you for filling the gaps in the S-... designation list. I missed S-63 and S-71 in my own hierarchy. Can you give some additional information on Sikorsky's AAH design to the AAH competition thread (drawings, artworks, etc.)?

Is anybody amongst the US readers able to detect a contact to Sikorsky and its archive to get an answer regarding a possible project designation system besides the built and 'nearly-built' S... helos (S-57, S-66, S-68, and S-71)?

 

[overscan (PaulMM)]

Sikorsky S-73 :

Not built, was the Sikorsky entry for the HLH program. The model chosen was the Boeing XCH-62

http://www.helis.com/timeline/sikorsky4.php

 

[Skybolt]

Oh, so this is the S-73? Funny, they used an out of sequence number.
http://www.secretprojects.co.uk/forum/index.php?topic=565.msg4296#msg4296

S-71. A line drawing. It looks like a Agusta A-129 Mangusta on steroids..
Everythinh I know of the S-71 can be summarized in: it used the dynamic parts (engine, rotor, tail-rotor, etc) of the S-70 (UTTAS wiining contender). The nose was very similar to the S-76 Blackhawk, a little shortened. Gun was a 30 mm, but this is in the AAH specification.

 

[Skybolt]

Funny things happen when you start dig in a topic. We all seem to know that the AARV was the S-68, but here http://aerofiles.com/_sik.html
they say that the S-68 was an unbuilt Super S-58T, and that the S-73 was the AARV, and no trace of the HLH... All in all, the state of the Sikorsky projects list is quite derelict... I bet that S-68 was the AARV. Moreover S-73 being the AARV is out of question (too many numbers in advance) and there was no reason the assign the 73 designation (at least the HLH would have first flown in 1973)

 

[boxkite]

See http://www.secretprojects.co.uk/forum/index.php?topic=244.0

The Russian book "Krylya Sikorskogo" by Katyshev & Mikheyev (ISBN 5203014688, Moscow, 1992) is the one and only source, where I've found a connection between the AARV programme and the S-68 designation.

 

[Skybolt]

Ah, Ah, No. It is listed as S-68 in the 1973 book "Elicotteri" by Nico Sgarlato, Ermanno Albertelli Editore, Parma - Italy, at page 170 (partial list of Sikorsky type numbers). Book loooooong out of print. It was one of my first serious books on aviation topics bought with my precious money... Good and bad of being 47...

 

[hesham]

I saw a design to Sikorsky for helicopter can fold its rotor and tail when it stores (beleaved S-90 because it precede S-92) in arabic magazine.

 

[snurg]

Sikorsky seems to be a special case among the US companies: Besides the S-… series and military designations not any project/design number of a ‘paper helicopter’ is known to me. At least three unbuilt projects got S-… numbers

- S-57 as a XV-1 and XV-3 competitor,
- the Cheyenne rival S-66, and
- the US Army funded AARV S-68.

Otherwise they gave them abbreviations of the programs (ACA, LHX, ABC -> see attachment from “Air Progress” June 1968 “Army squad carrier proposed by Sikorsky calls for contra-rotating, twin-rotor rigid units on a common axis. Designated "ABC" for advancing blade concept”), but these couldn’t compare with type designations used by other aircraft manufacturers. Btw, I don’t know any special book about Sikorsky helicopters (e. g. there is no Putnam publication). WHY?


Scott and Evan, do you see a chance to wake up Sikorsky’s archivists?

I've not worked at Sikorsky for quite a few years.

You could look at the Sikorsky web site's history entry: http://www.sikorsky.com/details/0,,cli1_div69_eti683,00+en-uss_0fsbc.html

Sikorsky's numbers were contiguous up to the S-70; I believe the S-71 was an attack derivative of the S-70. The designation for the S-76 was deliberately out of sequence. I believe the S-92 was also deliberately out of sequence.

I believe the Sikorsky designation for the ABC aircraft (XH-59) was S-69. The S-70 is called the H-60 in US service.

Sikorsky's archivist will probably respond to emails about historical models. I would suggest you try to contact them via Sikorsky's public relations people (see http://www.sikorsky.com/details/0,9602,CLI1_DIV69_ETI529,00.html).

You could also try contacting the Igor I. Sikorsky Historical Archives ( iisha@snet.net ).

 

[boxkite]

Another Sikorsky design without type number, named UTV = Universal Tactical Vehicle.

SOURCE: "aero" 3/1961 (page 54)

 

[Stargazer]

Sikorsky, like Curtiss, is one of my favorite research subjects in the pre-war period.

Allow me to share some of the info I have here, in the hope it will help a bit.

First of all, Sikorsky's design history is unique in that the numbering system he used after settling in the US took over where his Russian designs had left off.

- The first US design was the S-29, a cheap biplane passenger transport.
- The S-30 was a large biplane for 10 passengers.
- The S-31 was a 4-place trainer and camera-carrying biplane with a 200hp Whirlwind engine.
- The S-32 was a 4-seat biplane with 2 cabins for Andean National Corp.
- The S-33 MESSENGER was a biplane racer with a 60hp Wright Gale engine for NY races.
- The S-34 was a 6-passenger twin-engine, twin-boom flying-boat, his first such aircraft.
- The S-35 "Ville de Paris" was a 2-3 engine biplane with tanks for André Fonck's 1926 NYC-Paris transatlantic attempt.
All these early designs were built in only one example.

- The S-36 was an 8-passenger, twin-engine amphibian built in 5 examples, one of which went to Pan American in 1929.
- The S-37 "Southern Star" was similar to the S-35 with 6400 kms range. A bomber version, the VS-37B GUARDIAN, was evaluated as XP-496 by the USAAC and rejected.
- The S-38 AMPHIBION was a development of the S-36 with Wright J-5 engines, and the first commercially successful Sikorsky design, being produced in over 100 examples, for civilian airlines but also for the Army (as the C-6/-6A) and the Navy (as the RS-/PS- series).
- The S-39 SPORT AMPHIBION was a 4-5-seat high-wing flying-boat with a single 300hp Wasp Jr. engine. It also enjoyed commercial success, in smaller numbers though.
- The S-40 CLIPPER was a 4-engine 44-seat transport flying-boat developed for Pan American.
- The S-41 AMPHIBION was a 15-seat high-wing monoplane, an enlarged S-38 with two 575hp R-1690 engines. The Navy used it as the RS-1 and RS-5.
- The S-42 CLIPPER was a 32-passenger flying-boat with four 700hp Hornet S5D1G radial engines, again for Pan American.
- The S-43 AMPHIBION (better known as the "BABY CLIPPER") was a 16-25-seat amphibian transport for Pan American.
- The S-44 designation covers several large flying boats, the first of which was the Navy's XPBS-1 patrol bomber prototype dubbed the "FLYING DREADNOUGHT", followed by the JR2S-1 transports which were subsequently reconditioned as the "FLYING ACES" civilian airliners : "Excalibur", "Excambian", "Exeter".
- The S-45 was the "FUTURE TRANS-OCEANIC" transatlantic clipper project for Pan American (project N°M5-35). The largest of all Sikorsky flying-boat designs, it was cancelled when it became obvious that the golden age of the "clippers" was over.

Out of sequence were a handful of aircraft :
- The SN-1, a parasol-winged Standard J-1 conversion.
- The G-S-1 (UN-4), a modified Curtiss JN-4D fuselage with a Sikorsky-Gluhareff high-lift parasol wing (at least two were made).
- A non-designated re-winged Travel Air Model B.
- The Navy's XP2S-1, a flying-boat with a tandem R-1340-88 pusher/tractor in an interwing nacelle.
- The Navy's XSS-1/XSS-2, an experimental scout-observation flying-boat experiment for carrier duty.
- The XBLR-3, a cancelled long-range bomber project.

This marks the end of Sikorsky's first American period.


More on Sikorsky helicopters later... ;-)

 

[Stargazer]

American SIKORSKY Basic Model Numbers 29-92

designation description [military designation and/or ATC]

S-29 cheap biplane passenger transport
S-30 large biplane for 10 passengers
S-31 4-place trainer/photo biplane with 200hp Whirlwind
S-32 4-seat biplane with 2 cabins for Andean National Corp.
S-33/A MESSENGER biplane racer with 60hp Wright Gale for NY races
S-34 6-passenger twin-engine, twin-boom flying-boat
S-35 2-3 engine biplane with tanks for André Fonck's 1926 NY-Paris TransAtlantic Attempt
S-36 8-passenger, twin-engine amphibian, one to Pan American in 1929
SN-1 parasol-winged Standard J-1 conversion
G-S-1 (UN-4) modified Curtiss JN-4D fuselage with a Sikorsky-Gluhareff high-lift parasol wing [2-23]
no designation re-winged Travel Air Model B
S-37 / VS-37B GUARDIAN similar to S-35 with 6400 kms range; also bomber version (= Consolidated Model 11) [2-170, XP-496]
S-38 AMPHIBION development of S-36; first US military order and biggestt-selling pre-helo Sikorsky [PS, RS, C-6, ATC-60,-126…]
S-39 SPORT AMPHIBION 4-5-seat high-wing flying-boat with single engine [C-28, ATC-340,-375…]
S-40 CLIPPER 4-engine 44-seat transport flying-boat for Pan American [ATC-454,-562]
S-41 AMPHIBION 15-seat high-wing monoplane, a variant of S-38 with Hornet engines [RS, ATC-418, 2-286]
no designation US Navy flying-boat with tandem R-1340-88 pusher/tractor in interwing nacelle [P2S]
no designation US Navy experimental scout-observation flying-boat experiment for carrier duty [SS]
S-42 CLIPPER 32-passenger flying-boat with four Hornet engines for Pan Am [ATC-544,-592]
S-43 AMPHIBION 16-25-seat amphibian transport for Pan Am, better known as the 'BABY CLIPPER' [OA-8,-11, ATC-593,-623]
S-44 FLYING DREADNOUGHT / VS-44A development of S-36 as large patrol-boat, and civilian transport [PBS, JR2S, ATC-752]
S-45 FUTURE TRANS-OCEANIC transatlantic clipper project for Pan American (project N°M5-35); cancelled
no designation cancelled long-range bomber project for USAAF [BLR-3]
DS-160 first large transport helicopter project with original rotor configuration; not built
S-46 / VS-300 first successful US helicopter; 1931 single-rotor design, 18 major modifications
S-46 / VS-300A set helicopter endurance record and perfected two-rotor, cyclical-pitch control system
VS-310 KINGFISHER not a Sikorsky design; Vought project allocated a VS- designation circa 1941 [OS2U]
VS-315 "SKIMMER", "FLAPJACK" not a Sikorsky design; Vought project allocated a VS- designation circa 1941 [F5U]
S-47 / VS-316A (HOVERFLY I) 1st production helo; development of VS-300A with Warner Super Scarab engine [R-4, HNS]
VS-317 CORSAIR not a Sikorsky design; Vought project allocated a VS- designation circa 1941 [F4U]
VS-326 high-altitude test planes to test R-4360 Wasp Major fitted with turbosuperchargers
S-48 / VS-327 transport development of R-4 design with longer fuselage and Wasp Jr. Engine [R-5, H-5]
S-49 / VS-316B (HOVERFLY II) refined development of R-4 with Lycoming or Nash-Kelvinator engine [R-6, R-7, HOS]
S-50 abandoned small helicopter project, wooden mock-up only
S-51 DRAGONFLY / WS-51 WIDGEON II refinement of S-50, some license-built by Westland [H-5, HO3S]
S-52 two-seat, later four-seat experimental helicopter [H-18, HO5S
S-53 experimental helo with tricycle gear, small tail rotor pylon, tailplane, metal folding rotor blades [HJS]
S-54 R-4B bought back by Sikorsky and modified to the "sesqui-tandem" configuration
S-55 CHICASAW / WHIRLWIND military transport and civilian variants, some built under license by Westland [H-19, HO4S, HRS]
S-56 *MOJAVE / °WESTMINSTER US Marines large ASW helicopter and *transport Army variant, also built by Westland° [HR2S]
S-57 RETRACTABLE ROTOR experimental design competing with the Bell and McDonnell convertiplanes; not built [XV-2]
S-58 CHOCKTAW/SEABAT/SEAHORSE / WS-58 WESSEX utility/transport/ASW, multi-service, some by Westland [H-34, HSS, HUS]
S-59 H-18 modified with Artouste turbine for tests [H-39]
S-60 SKYCRANE flying-crane prototype pre-dating the S-64 series
S-61 SEA KING / JOLLY GREEN GIANT / PELICAN search and rescue / transport multi-service helicopter [H-3, CH-124, HSS-2]
S-62 SEA GUARD search and rescue helicopter developed specifically for US Coast Guard [H-52, HU2S]
S-63 initial designation of the S-62B
S-64 SKYCRANE / *TARHE flying crane used both in Army* and civilian service [H-54]
S-65 STALLION / SEA STALLION / SUPER JOLLY heavy transport and/or armed helicopter for US Marines and USAF [H-53]
S-66 AAFSS proposal, competing with Lockheed's YAH-56 Cheyenne; mock-up only
S-67 BLACKHAWK gunship demonstrator; crashed
S-68 AARV (Aerial Armoured Reconnaissance Vehicle) helicopter project
S-69 ABC Advanced Blade Concept demonstrator with counter-rotating rotors on top of one another [H-59]
S-70 BLACK HAWK / SEAHAWK / JAYHAWK… multipurpose helicopter used by the Armed Forces over the world [H-60]
S-71 AAH (Advanced Attack Helicopter) competitor of YAH-63 and YAH-64
S-72 'X-WING' RSRA (Rotor Systems Research Aircraft)
S-73 HLH (Heavy Lift Helicopter), competitor of XCH-62
S-74 no details
S-75 ACAP (Advanced Composite Airframe Program)
S-76 SPIRIT / H-76 SHADOW / EAGLE (NOTE: "H-76" not a DoD designation)

S-2000 EAGLE 'FANTAIL' also called H-76B (not a DoD designation)

S-78 alternate designation of S-70C-20

S-80 SEA DRAGON / SUPER STALLION designation of certain variants of the H-53

COMANCHE LHX program winner with Boeing; production canceled [H-66]

S-92 HELIBUS / SUPERHAWK / *CYCLONE [*CH-148]

CYPHER / CYPHER II / MARINER family of ring-shaped UAVs

SPEEDHAWK Piasecki modified H-60 to demonstrate the X2 technology [X-49]

S-97 RAIDER future candidate for H-60 replacement using X2 technology




NOTE: Designations in red indicate additions and modifications from the initial list.
The designations S-46, S-47, S-48 and S-50 were differently allocated in earlier and less reliable sources.
The new allocations correspond to publications emanating from the Sikorsky Archives.

 

[Maveric]

Hi,

a big step back. Please tell me the Sikorsky S-numbers for his russian designs "Russkii Vityaz" and "Ilya Muromets".
I have also gaps from S.13 to S.15 and S.XX to S.29 :-\

 

[Stargazer]

Hi! The S-20, a fighter, entered service in 1917, and is said to be the last Russian Sikorsky-design.

This being said, the earlier Ilya Muromets series is given as S-22 to S-27, which are later designations... I have no explanation for this, nor can I verify from authentic sources as I'm not fluent in Russian!

S-22? Ilya Murometz A: 1913, 1 built, unarmed trainer
S-23 Ilya Murometz B: 4-engined, 7 built; in service 8/14, original armament 1x3,7 and 1x0,8MG
S-24 Ilya Murometz V: 4-engined bomber 1915
S-25 Ilya Murometz G-1: 4-engined bomber 1915
S-25 Ilya Murometz G-2: 4-engined bomber, 170 kg Bomben; 5 MG
S-25 Ilya Murometz G-3: 4-engined bomber, 190 kg Bomben; 6 MG
S-26 Ilya Murometz D: 1916/not built?
S-27 Ilya Murometz E (Ye): bomber 1917

Source: http://www.geocities.com/flugzeugfiles/aircraft/sikorsky.html

 

[AM]

Hi all

early Sikorsky aircraft:

S-1 experimental helicopter (1909)
S-2 experimental helicopter (1911)
S-3 training aircraft (1910). Based on BIS No.2 aircraft
S-4 sport aircraft (1910). Based on S-3
S-5 reconnaissance aircraft (1911)
S-6 two-seat biplane (1911)
S-7 two-seat biplane (1912)
S-8 training aircraft (1912)
S-9 light aircraft (1913)
S-10 reconnaissance aircraft (1913)
S-11 reconnaissance aircraft (1913)
S-12 reconnaissance and training aircraft (1913)
S-15 escort fighter (1915)
S-16 fighter (1915)
S-17 reconnaissance aircraft (1915)
S-18 heavy fighter (1916)
S-19 ground attack aircraft (1916)
S-20 fighter (1916)
S-21 "Russky Vityaz' " ("Grand") experimental heavy aircraft (1913)
S-22 "Ilya Murometz" B Srs. heavy bomber (1913). 7 built
S-23 "Ilya Murometz" V Srs. heavy bomber (1914). 17 built
S-24 "Ilya Murometz" G Srs. heavy bomber (1915). 56 built
S-25 "Ilya Murometz" D Srs. heavy bomber (1916). 3 built
S-26 "Ilya Murometz" E Srs. heavy bomber (1916). 2 built

 

[hesham]

Hi,

S-13 recce aircraft,not sure.

 

[Jos Heyman]

Over the years I have collected a few different versions:
S-3 and S-4 were also helicopters based on the S-2
S-9: was known as Le Grand and this four engined aircraft made 53 flights after its first flights on 13 May 1913
S-46: VS-300
S-47: VS316
S-48: VS-327
S-74: Original designation of S-76.
My guess is that some of these designations were made up at a later date and that several persons have attmepted to do that with different results.
It would be interested to know why Sikorsky started his American run with S-29.

 

[Stargazer]

The Sikorsky helicopters designations you are quoting are not quite right.
Here is the correct allocation of the early US helicopters:

S-46: VS-300
S-47: VS-300A
S-48: VS-316A = R-4
S-49: VS-316B = R-6
S-50: VS-327 = R-5 to R-5E and HO2S
S-51: H-5F to H-5H and HO3S
S-52: H-18 and HO5S
S-53: XHJS-1
S-54: R-4 modified in sesqui-tandem configuration

 

[Maveric]

For the early design numbers we need only the S.14 ??? ??? ???

 

[Stargazer]

Confirmation of the correct Ilya Muromets designations comes from a book written by Sikorsky's son himself using the official Sikorsky archives. It can't get better than that!

 

[hesham]

Hi,

I found in NASA report that,the Sikorsky S-72 was called (design number
No.233),and I think it means DS-233,unfortunately I don't remember
this report now.

 

[Stargazer]

Good piece of info, Hesham, it makes sense. Unfortunately the DS- list has never been seen anywhere to the best of my knowledge, and we only know a handful of them...

 

[Maveric]

...could this be the wanted S.28... ??? ??? ???

from: "French aircraft of the First World War" page465

Sikorsky Bomber
Igor Sikorsky arrived in France in 1917 after the Russian Revolution had begun...
...He was asked to use his talent for producing large aircraft (BN class)...
...Five aircraft were ordered but the Armistice ended the urgent need for a night bomber.
The project was terminated before a single aircraft could be completed, and Sikorsky left
for the United States a few months later.

Maveric

 

[Stargazer]

Wow! Great find. Some new element to add to the Sikorsky story... and quite possibly the answer to the S.28 mystery indeed. Thanks for sharing!

 

[borovik]

For the early design numbers we need only the S.14 ??? ??? ???

...could this be the wanted S.28 ??? ??? ???

S.-13; S.-14 (1915) - light, single-seater, but, owing to their engines are not built. (Source did not mention was that recce aircraft or fighters)
S.-27 / IS-27 "Atlas" (1918, August), France, bomber capable of carrying a bomb in 1000kg., Designed by two motors "Liberty", later the customer suggested the use of four engine, Hispano-Suiza.
S.-28 first (1919, June), U.S. Heavy bomber for the White army of Kolchak.
Sikorski with A.Prokof'ev-Seversky creates "Hannevig-Sikorsky Aircraft Compani". To shorten the time to be used as studies for french project with capacity of up to five tons. The political situation has been changing rapidly and the company was short-lived.
S.-28-second (1919, November) Multiseater , biplane (span-40m) with three engines 700hp. There were two versions of the project.
Option "A" - two engines placed on the lower wing, the third in the nose or the back of the nacelle fuselage.
Option "B" - two engines placed on the lower wing, third on the upper wing, tailplane had a different form of fastening.

Sources: G.Katyshev, V.Mikheev "Wings Sikorsky", 1992
V.Mikheev "Unknown Sikorsky", 2010

 

[Maveric]

Many Thanks borovik. Very interesting informations... THANKS.

 

[saturncanuck]

Was XBLR-3 ever assinged a number?

 

[Stargazer]

Was XBLR-3 ever assinged a number?

Perhaps a design number (DS-), but certainly not an S-** model number.

 

[saturncanuck]

Was XBLR-3 ever assinged a number?

Perhaps a design number (DS-), but certainly not an S-** model number.

Why do you say that? The XBLR-2 was Douglas, the XBLR-3 was Sikorsky.

 

[Stargazer]

Was XBLR-3 ever assinged a number?

Perhaps a design number (DS-), but certainly not an S-** model number.

Why do you say that? The XBLR-2 was Douglas, the XBLR-3 was Sikorsky.

I believe what he meant by "number" was a Sikorsky model number, like S-43, S-44, etc. The XBLR-3 project never received any of these. In my post, "DS-" does not refer to Douglas El Segundo models, but to Sikorsky design numbers (such as DS-103, DS-160...)!

 

[saturncanuck]

Thanks for clearing this up.

My bad.

 

[Stargazer]

With the purchase of Schweizer by Sikorsky, new designations have popped up. Here is one : S-434.

• Sikorsky® Schweizer™ S‑434™ Helicopter

 

[Jos Heyman]

We now have the S-97 but what were the S-93 to S-96. Also what were the S-77, S-79 and S-81 to S-91?

 

[redstar72]

S-7 two-seat biplane (1912)
...
S-15 escort fighter (1915)

S-7 was monoplane: http://www.airwar.ru/enc/law1/s7.html
S-15 was not escort fighter, probably you confused with S-16 (or with S-17 which was considered to be an escort fighter). S-15 was recon floatplane, modified S-10-Hydro with more powerful version of Argus engine.

S-9: was known as Le Grand and this four engined aircraft made 53 flights after its first flights on 13 May 1913

You are the second person known to me who consider Le Grand to be S-9 - but I can't understand why... The Le Grand / Russian Knight never was S-9, it was S-21. The S-9 was 3-seat monoplane with monocoque fuselage design, dubbed Kruglyi (Round one) for its fuselage cross-section: http://www.airwar.ru/enc/law1/s9.html.

 

[Stargazer]

You are the second person known to me who consider Le Grand to be S-9 - but I can't understand why... The Le Grand / Russian Knight never was S-9, it was S-21. The S-9 was 3-seat monoplane with monocoque fuselage design, dubbed Kruglyi (Round one) for its fuselage cross-section: http://www.airwar.ru/enc/law1/s9.html.

One thing is for sure: there has always been a lot of confusion regarding the Sikorsky designations of the Russian era. And yes, S-9 is one of the designations that varies according to the sources. It makes me wonder if there could have been a renumbering decision by Sikorsky at some point to clarify things... Or perhaps a mistake or two in period publications that were subsequently repeated by all later research works...

 

[redstar72]

I think the "S" numbers of Sikorsky's Russian era heavy aircraft were given retrospectively. Most probably they were defined only by their names and type letters (Ilya Muromets family) at their recent time. I have read some Russian aviation periodics from years 1913-14, and of course there were publications about Le Grand - but any "S" number wasn't mentioned. Also there are no "S" numbers for them in Shavrov's bible, nor in the book History of Aeronautics & Aviation in Russia, July 1914 to October 1917 by Pyotr Duz', as well as in "Ilya Muromets" monograph by Marat Hairullin.

 

[Stargazer]

I think the "S" numbers of Sikorsky's Russian era heavy aircraft were given retrospectively. Most probably they were defined only by their names and type letters (Ilya Muromets family) at their recent time. I have read some Russian aviation periodics from years 1913-14, and of course there were publications about Le Grand - but any "S" number wasn't mentioned. Also there are no "S" numbers for them in Shavrov's bible, nor in the book History of Aeronautics & Aviation in Russia, July 1914 to October 1917 by Pyotr Duz', as well as in "Ilya Muromets" monograph by Marat Hairullin.

Interesting. You are confirming my impressions here. Until relatively recently I had never come across the designations S.21 to S.26 and was under the impression that they had been assigned retrospectively by historians trying to fill the gap between S.16 and S.29. So maybe this was so...

 

[Maveric]

Hi all,
the Sikorsky S.63!