Piston-to-turboshaft helicopter conversions


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Jens was first-up with a turboshaft conversion, the Sikorsky S-58T. Here's a tentative list of unbuilt and built piston-to-turboshaft conversions ...


Unbuilt Projects

Bölkow Bo 103 - (Project) Planned evolution to Bo 103B
- Bo 103B: 1 x 90 shp BMW turboshaft;* rotor diam. 6.66 m
-- Orig. Bo 103 powerplant was Agusta GA.70 V piston 4-cyl
-- * Presumably meaning the 90 shp BMW/MAN/MTU 6012
-- https://web.archive.org/web/20060109015354/https://www.gasturbine.pwp.blueyonder.co.uk/bmw.htm
-- https://web.archive.org/web/20080217053948/http://www.technologie-entwicklung.de/Gasturbines/MTU_6012/mtu_6012.html
-- https://web.archive.org/web/2007092...com/1024/en/eads/history/airhist/1960_1969/bo

Bölkow Bo 104 - (Project) Planned evolution to Bo 104(?)
- Bo 104: 2 x MAN 6022-A3s* (repl. NSU Wankel rotaries)
-- * BMW/MAN 6022-A3 was derived from APU for CH-53G

Bristol 171 Sycamore - (Project) Evol. into Bristol 203/214
-- Orig. 171 powerplant was 1 x 550 hp Alvis Leonides 173
- Bristol 203: 1 x DH (later B-S/R-R) Gnome turboshaft
- Bristol 214: 2 x DH (later B-S/R-R) Gnome turboshafts
-- http://www.secretprojects.co.uk/forum/index.php/topic,2298.15.html

Hiller UH-12E5 - (Project) Evolved into Hiller UH-12E5T (Turbine)
-- Orig. UH-12E5 powerplant was 1 x 305 hp Lycoming VO-540
- UH-12E5T: 1 x 420 shp Allison 250-C20B (as per Soloy conv'n)
- UH-12E5T: US Army New Training Helicopter submission

Kaman K-600 - Project 195(?) conv. to coupled-turbine K-300-4
-- Orig. K-600 powerplant was 1 x 600 hp P&W R-1340-28
- K-300-4: 1 x 980 shp Blackburn BnTC.1 Twin-Turmo*
-- * Coupled Turmo 600 turbines with common final-stage

Kamov Ka-26 - (Project) Evolved into Arriel-powered Ka-128
-- Orig. Ka-26 powerplant was 2 x 325 hp M-14V-26 radials
- Ka-128 : 1 x 732 shp Turboméca Arriel 1D1 turboshaft
- Ka-128 : Similar to built Ka-126 with Mars TV-O-100

Piasecki H-21 - (Project) French conv. to Turmo turboshafts
-- Orig. H-21 powerplant was 1 x 1,425 hp Wright R-1820-103
- H-21: 3 x 600 shp (max 750 shp) Turboméca Turmo IIIs-- Source: AFM N°10, 6/7 2006

Piasecki YH-16 - (Project) Evol. into YH-16B Turbotransporter
-- Orig. powerplant for YH-16 was 2 x 1,650 hp P&W R-2180 radials
- YH-16B Turbotransporter: 2 x 3700 shp Allison T56 turboshafts
- YH-16B: Cancelled after crash of turbine prototype YH-16A in 1956

Sikorsky S-52 - (Project) 1988 Orlando Helicopter conv.; no details (??)
-- Original S-52 powerplant was a 245 hp Franklin O-425 HO6
- OHA S-52T: Clipper; 1 x (??) shp (??) turboshaft

Sikorsky S-52 - (Project) Vertical Aviation Technology 260L turbine conv.
-- Orig. Hummingbird 260L engine was 265 hp Lycoming IVO-435
- Vertical 260T: 1 x 317 shp Allison 250-C18; only got to mockup stage
-- Sources: FRW 7/1988 p.32 and JAWA 1988-89 p.495

Sikorsky S-55 - (Project) 1988 Orlando Helicopter conv.; no details (??)
-- Orig. S-55 powerplant was a derated 700 hp Wright R-1300 Cyclone
-- OHA S-55T Phoenix; nose cockpit; 1 or 2 x turboshafts above

Sikorsky S-58 - (Project) 1988 Orlando Helicopter reconfig/turbine conv.
-- Orig. S-58 powerplant was 1,525 hp (T/O) Wright R-1820-84 radial
- OHA S-58T: completely rebuilt; cockpit in nose; turbines above cabin
- OHA S-58T: 2 x (??) shp P&WC PT6A (or possibly PT6T TwinPac?)

Sikorsky S-56 - (Project) Westland conv. to turbine-powered WS-56
-- Orig. S-56 powerplants were 2 x 2,100 hp P&W R-2800-54 radials
- WS-56 : 2 x (??) shp Napier Elands (ends of S-56 stub wings)

Yakovlev Yak-24 - (Project) Evolved into twin turboshaft Yak-24P
-- Orig. Yak-24 powerplant was 2 x 1,700 hp ASh-82V radials
- Yak-24P: 2 x 2,700 shp Ivchenko AI-24V turbishafts (abandoned)
-- http://www.aviastar.org/helicopters_eng/jak-24.php


Built Conversions

Agusta-Bell 47J - 1962 evolution into turbine Agusta A.115
- Orig. AB 47J powerplant: 270 hp Lycoming TVO-435-B1A
- A.115: 1 x 480 shp Turboméca Astazou II; I-AGUC

Bell 47G - 1954 evol. into turbine-powered XH-13F; x 1
- XH-13F: PoC for turbine-powered XH-40 Iroquois
- XH-13F: 1 x 425 shp Continental CAE XT51-T-3*
-- * Licensed Turboméca Artouste I turboshaft
-- XH-13F corporate designation was Bell Model 201
-- XH-13F/Model 201 was Bell's first turbine helicopter

Bell 47 - 1961 evol. into turbine-powered HUL-1M; x 2
- HUL-1M: Turboshaft evolution of the US Navy HUL-1
- HUL-1M: 1 x 250 shp Allison YT62-A-3 turboshaft*
-- * Mounted above fuselage, not in 47J engine bay
-- HUL-1M redesignated UH-13R in 1962 DOD system

Bell 47G - 197? Soloy Conversions Ltd Bell Turbine conv.
-- Orig. 47G powerplant was 1 x 225 hp Lycoming VO-435
- Bell Turbine 1 x 261-301 shp* Allison 250 C18 turboshaft
-- Derated engine output depends upon transmission fitted
-- Source: Aircraft (German magazine) # 27 753

Bell 47G - 1985 conv. Texas Helicopter M-79T Jet Wasp II
-- Orig. 47G powerplant was 1 x 225 hp Lycoming VO-435
- M-79T: 1 x derated 420 shp Soloy-Allison 250-C20S turbine
- M-79T: Turbine vers. of single-seat M-74S Jet Wasp II
- M-79T Hornet: Tandem-seat attack helo trainer version
-- NB: M-79Ts are airframe mods using std Soloy conv. kits

Bristol 173 - Evol. into Bristol 191 testbed & 192 Belvedere
-- Orig. 173 powerplant was 2 x Alvis Leonides Major radials
- Bristol 192: 2 x 1,465 shp Napier Gazelle N.Ga.2 turboshafts
-- http://www.secretprojects.co.uk/forum/index.php?topic=2872.msg23033

Enstrom F-28A - 1978 evol. into turbine-powered Spitfire Mk 1*
-- Orig. F-28A powerplant was 1 x 205 hp Lycoming O-360-C1A HO6
- Spitfire Mk 1: 1 x 420 shp Allison 250-C20B turboshaft**
-- * Developed by Spitfire Helicopter Company of Lynnfield, MA
-- ** Same as 5-seat Spitfire Mk 2; some sources say more

Enstrom 280FX - 1984 conv. to turbine-powered Enstrom 280FXT
-- Orig. 280FX powerplant was 225 hp Lycoming HIO-360-F1AD
- Enstrom 280FXT: 1 x 420 hp Allison 250-C20W; x 1 (N280FX)
-- Led to 1988 TH-28* for US Army's New Training Helicopter
-- * Internal designation; 'TH' stood for 'Turbine Helicopter'
-- 6 x TH-28 completed for unsuccessful trials for US Army NTH
-- TH-28 3-seater led to 4-seat civil/military Enstrom 480 series

Harbin Z-6 - 1969 evol. to turbine-powered Harbin/CHDRI Z-6
-- Orig. Z-5 powerplant: 1 x 1,680 hp Dongan HS-7 (ASh-82V)
- Z-6: 1 x 2,200 hp Dongan WZ-5 (WJ5 turboshaft derivative)

Harbin Z-5 - 1979 conv. to turbine-powered 'Z-6' []sic]; x 1
-- Orig. Z-5 powerplant: 1 x 1,680 hp Dongan HS-7 (ASh-82V)
- Z-5 (PT6T): 1 x (derated?) 1,875 shp P&WC PT6T-6 Twin Pac

Hiller UH-12E - 1975 Soloy conv. to turbine-powered UH-12E4T
-- Orig. UH-12E powerplant: 1 x 305 hp Lycoming VO-540-C2A
- UH-12E4T: 1 x derated* 301 shp Allison 250-C20B turboshaft
-- * The usual Allison 250-C-20B output rating was of 420 shp

Hiller UH-12E - Joint devel. to Soloy-Hiller UH-12E conv. kits*
-- Orig. UH-12E powerplant: 1 x 305 hp Lycoming VO-540-C2A
- Soloy-Hiller UH-12E: 1 x 301 shp Allison 250-C20B turboshaft
-- Alt. designations Soloy UH-12E3T; Soloy UH-12E4T; etc.

Kaman K-225 - Dec 1951 conv. to 1st-ever turbine helicopter
-- Orig. K-225 powerplant was 1 x 225 hp Lycoming O-435-A2
- K-225 (turbine): 1 x 225 shp** Boeing 502-2E (YT50-BO-2)*
-- * Conv. intended as turbine helo demonstrator for US Navy
-- ** Some YT50-BO-2 power outputs listed as 175 or 210 shp

Kaman K-240 - 1954 USN HTK-1 conv. to twin-turbine HTK-2
-- Orig. K-225 powerplant was 1 x 240 hp Lycoming O-435-4
- K-240/HTK-2: 2 x 225 shp* Boeing 502-2E (YT50-BO-2)
-- * Some YT50-BO-2 power outputs listed as 175-210 shp
-- K-240/HTK-2 was first even twin-turboshaft helicopter

Kaman K-600 - 1956 HOK-1 conv. to single turbine testbed
-- Orig. K-600 powerplant was 1 x 600 hp P&W R-1340-28
- K-200 (turbine): 1 x derated 825 hp Lycoming XT53

Kaman K-600-3 - 1959 HOK-1 evol. to turboshaft HH-43B
-- Orig. K-600 powerplant was 1 x 600 hp P&W R-1340-28
- K-200-3/HH-43B: 1 x 849 shp Lycoming T53-L-1B turbine

Kamov Ka-26 - 1988; evol. into turboshaft-powered Ka-126
-- Orig. Ka-26 powerplant was 2 x 325 hp M-14V-26 radials
- Ka-126 : 1 x 720 shp Mars TV-O-100 turboshaft engine
- Ka-126 : Soviet equiv. to later twin-engined Kamov Ka-226

Kamov Ka-26 - 1997; evol. into turboshaft-powered Ka-226
-- Orig. Ka-26 powerplant was 2 x 325 hp M-14V-26 radials
- Ka-226 : 2 x 450 shp Allison 250-C20R/2 turboshaft engines
- Ka-226T: 2 x 580 shp Turbomeca Arrius 2G1 turboshafts
-- Other engine options: Progress ZMKB AI-450; Klimov VK-800

Piasecki YH-16 - Evolution into prototype YH-16A Turbotransporter
-- Orig. powerplant for YH-16 was 2 x 1,650 hp P&W R-2180 radials
- YH-16A Turbotransporter: 2 x 1,800 shp Allison T38 turboshafts
- YH-16A: 1956 fatal crash of prototype led to cancelling of YH-16B
-- http://www.aero-web.org/specs/piasecki/yh-16a.htm

Piasecki H-21C - 1959 turboshaft conv. (c/n B-168) to XH-21D
-- Orig. H-21C powerplant: 1 x 1,425 hp Wright R-1820-103
- Model 71/XH-21D: Trial turbine conversion for the US Army
- Model 71/XH-21D: 1 x 1,024 shp General Electric T58s
-- Converted back to piston engines after trials were completed

Piasecki H-21C - 1959 trial turboshaft conversion (c/n B-167)
-- Orig. H-21D powerplant was 1 x 1,425 hp Wright R-1820-103
- Model (?)/XH-21(?): Trial turbine conversion for the US Army
- Model (??)/XH-21(?): 2 x 700 shp Lycoming YT53 turboshafts
-- Conf. as to whether s/n 53-4370 was re-converted to piston

Sikorsky S-52 - 1953 conv. into turbine-powered S-52-5 (DOD YH-18B)
- S-52-5: 1 x 400 shp Continental/Turbomeca Artouste II/XT51-T-3B
-- Orig. S-52 powerplant was 245 hp Franklin 6V6-245-B16F piston HO6
-- * DOD O-425-1 when US Army YH-18B (later conv. into S-59/XH-39)

Sikorsky S-55 - 1969* Aviation Specialties Inc.'s Helitech S-55T
-- Orig. S-55 powerplant was 1 x derated 700 hp Wright R-1300
- S-55T: 1 x derated 650 shp Garrett-Airesearch TSE-331-3U-303
-- * S-55T prototype N1255T flew 1969; FAA issued STC in 1971
-- https://www.heli-archive.ch/en/helicopters/in-depth-articles/helitech-sikorsky-s-55t

Sikorsky S-55 - 1999 evolution into the VAT S-55QT Whisper Jet
-- Orig. S-55 powerplant was 1 x derated 700 hp Wright R-1300
- S-55QT: 1 x 1,040 shp Honeywell/Garrett TSE331-10 turboshaft
-- Whisper Jet Inc./Vertical Aviation Technology* joint venture
-- * Florida-based VAT had purchased all of the assets of OHA
-- 5-bladed main rotor (from OHA S-55 as US Army 'aggressor')

Sikorsky S-58 - 1957 conversion to turbine HSS-1F Seabat testbed
-- Orig. S-58 powerplant was 1,525 hp (T/O) Wright R-1820-84 radial
- HSS-1F: 2 x 800 shp GE YT-58s; conv. c/n 58-264 (BuAer 141601)
-- Unsuccessful HSS-1F was demonstrator for planned prod'n HSS-2

Sikorsky S-58 - 1957 conv. into turbine Westland Wessex testbed
-- Orig. S-58 powerplant was 1,525 hp (T/O) Wright R-1820-84 radial
- S-58: Ex-USN 141602; G-17-1/XL722; 1 x Napier Gazelle NGa.11
-- Testbed conv. leads to 1958 prod'n variant - Wessex HAS.1

Sikorsky S-58 - 1964 French Sud Aviation conv. to Turbomeca Bi-Bastan
-- Orig. S-58 powerplant was 1,525 hp (T/O) Wright R-1820-84 radial
- S-58 (turbine): 1 x 1,900 shp Turbomeca Bi-Bastan turbine*
-- *Bi-Bastan was coupled turboshaft version of Bastan turboprop

Sikorsky S-58B/S-58E - 1970 conversion into turbine-powered S-58T
-- Orig. S-58 powerplant was 1,525 hp (T/O) Wright R-1820-84 radial
- S-58T: Joint Sikorsky/Orlando Helicopters project with Twin Pac*
- S-58T: 1 x derated 1,505 shp Pratt &Whitney Canada PT6T-3
-- * P&WC PT6T-3 (Apr 1971 STC SH71EA) or P&WC PT6T-6**
-- ** 1975 S-58T with PT6T-6 was 'Super T'; later S-58T Mark II
- S-58T Mark II: 1 x derated 1,625 shp P&WC PT6T-6 Twin Pac
-- https://www.heli-archive.ch/en/helicopters/in-depth-articles/sikorsky-s-58t

Westland WS-55 - 1959 conv. into turbine Whirlwind Series 3
-- Orig. srs 2 Whirlwind engine was Alvis Leonides Major 755
- WS-55 srs 3: 1959; 1 x powered by General Electric T58 turboshaft*
-- * Conv. srs 2 c/n WA241 (G-APDY); later B-S Gnome H.1000**
-- ** Gnome was Bristol Siddeley's licenced GE T58 turboshaft

Westland WS-55 - Trial conv.; Blackburn Turmo 600 coupled turbines
-- Orig. srs 2 Whirlwind engine was Alvis Leonides Major 755
- WS-55 Twin-Turmo: 1 x 980 shp Blackburn BnTC.1 Twin-Turmo
-- * Twin-Turmo = coupled Turmo 600s with common final-stage
-- Reconverted to Alvis Leonides Major after trials; delivered to RAF
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Just found when I browsed through the pityful few issues otf the Aviation Francais Magazine :
A planned conversion of the Piasecki H.21 with three Turboméca Turmo III engines.
Thanks Jens!

Does AFM give any other details? I entered it as "Turmo III" but I am wondering if we can assume 750-800 shp Turmo IIIBs (as per SE.3200 Frelon?). [750 shp max, 600 shp continuous.]

If Piasecki/Vertol wanted the option of safe running on two turbines, the combined power of the Turmo IIIBs would seem about right for replacing the 1425 hp Wright recip.
The article just speakes of "Turmo III"engines, giving power output as 750hp (max).
(3-view from AFM N°10, 6/7 2006)


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Thanks Jens! H-21 triturbine added.

I've also added the Piasecki YH-16A and YH-16B (thanks boxkite). http://www.piasecki.com/yh-16.htm
Could this '(work)horse with no name' be a YH-16 derivative ???

SOURCE: magazine Der Flieger 10/1952 (p201)


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Yes, I believe so.

From: http://www.aero-web.org/specs/piasecki/yh-16a.htm

Quoting from J.P.Spencer "Whirlybirds: A History of the U.S. Helicopter Pioneers", 1998

"This tragic accident caused the H-16 program to be scrapped, preempting the sixty-nine-passenger YH-16B Turbotransporter (a conversion of the YH-16 then in progress), which would have flown with two 3700shp Allison T56 engines. It also preempted Frank Piasecki's vision of interchangeable under-body pods for the rapid transport of differing loads such as field operating rooms, communications centers, and mobile repair centers. A tall stilt landing gear had already been designed to let the YH-16B accommodate such pods."
Another unbuilt helicopter that may qaulify for this thread is the Enstrom 280 Eagle which would have been the Model 280L powered by an Allison 250-C20B turboshaft.
Enstrom also built (in 1988) the Model 280FXT with Allison 250-C20W turbine. This prototype was a rebuilt of the first Model 280FX. It formed the basis for the Model 480 (TH-28)
Could someone put 'helicopter' in the subject since there's already a huge discussion on piston to turboprop conversions, mainly regarding airplanes?
How about the Kaman HOK-1 with the R-975 becoming the H-43 with a T-55?
Some belated updates (and corrections to this thread). Also two questions ...

Hood: "unbuilt" Enstrom Eagle. Wasn't Eagle the sole PoC 280FXT conversion?

Frank: I've listed the K-600/HOK-1 conversion with XT53. Was 'T-55' a typo or is this another variant we need to know about?
I've come across a reference to a Bristol 171 Turmo while digging through files at the National Archives.
It was mentioned on a Bristol graph showing the workload of the design department in 1955-56 (effects of cancelling the Type 191).

Sadly, I don't think anything else surfaced while I was looking at Scyamore files. I'm guessing that might have been what became the Type 203 with the Gnome.
Brief mention in Flight of 1959 of the Piasecki [X]H-21D having flown with a pair of T58s:

... and T58s have now flown in the Sikorsky S-62, Vertol H-21D,
Sikorsky HSS-1F (S-58) and in a Westland Whirlwind.


Plus earlier 1957 reference:
Another twin installation has been made in a Vertol H-21D, the Navy
having undertaken this on behalf of the Army who are the sponsors;
this aircraft should have flown last April but has not yet done so.


I believe there was also a twin-T53 H-21 project but can't determine if it ever made it to hardware stage. Oh, this site claims it was c/n B-167 that was converted back to piston after testing!


Likewise B-168 converted back after T58 testing:


One or other was used for stability augmentation testing in 1959:

Sud S-58 Bi-Bastan conversion, Flight 1964


Powered with the 1,900 h.p Turbomeca Bi-Bastan, a coupled version of the single-shaft turboprop, the conversion included lengthening the nose by 2ft 3in to maintain the c.g. position with the lighter engine.

As this is a shaft turbine, the exhaust is in the nose and the engines are reached by opening clamshell doors.

The aircraft underwent full flight trials, but there is no current information about its status.

Earlier 1962 reference notes that it was also intended for the H-21 ( sensibly, since the French also used that ) but no evidence it flew in that airframe:


Some searches of French web pages indicates that the S-58 re-engining was a contingency at a time of budget restrictions, when there was a risk that the SA.330 project would not proceed. When the contract for that type was finally issued in 1964, the S-58 project fell from priority and was relegated to a commercial package offered to S-58 operators.

Initially the SA.330 was sketched as using the same Bi-Bastan engine, so not all the engineering was wasted.


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Agusta A.115, 1962. License-built Bell 47J fitted with Astazou II, quite sporty with 480 shp on tap. Hovering ceiling OGE 3,500 metres! Only one conversion.

Apophenia said:
Westland WS-55 Whirlwind (R-1340-40, R-1300-3, Leonides Major) [Conv/Evol] into Whirlwind Mk3 (T58/RR Gnome)

Also one Whirlwind was fitted with the Blackburn Twin-Turmo ( BnTC.1 ) rated at 980 shp. Re-converted to Alvis Leonides engine after testing and delivered to the RAF as XJ466.

The Twin-Turmo was based around a pair of Blackburn-built Turmo 600s driving a common final-stage. Installation in the Whirlwind was at 35 degrees to integrate with the original gearbox. Description and diagram here:

Late in their lives, a few RAF Whirlwinds were retrofitted with Rolls Royce Gnome turbine engines.

Westland Wessex production started with Napier Gazzelle engines, but most production Wessex had a pair of RR Gnomes in the nose. Gnome was a T58 turbo shaft engine built under license from General Electric (USA). T58 was standard power for later S-61 Sea King helicopters.

Later, Sikorsky converted some military-surplus S-58s to S-58T configuration by installing Pratt & Whitney of Canada PT6A-3 Twin-Pacs. S-58T can be recognized by the twin, rectangular intakes on top of the nose. During the 1970s (?) some one suggested converting a fleet of SE Asian (Thai ?) military S-58s to S-58T configuration.
1,800 horsepower (combined) P&WC PT6A-3 Twin Pacs power Bell 212 Twin Huey's and a variety of other, twin-engined helicopters.
Soloy has retrofitted a bunch of Hiller UH-12E and Bell 47 helicopters with Allison/Rolls Royce 250-C20B turbine engines. Most of these conversions dust crops.
Soloy installs the same Allison/RR 250 engine as installed in Jet Ranger, Hughes 500, etc. factory-fresh airframes.

Robinson offers the (new production) R66 helicopter with an RR300 300 horsepower turbine. From a distance, the R66 resembles the earlier, piston-powered Robinson 44 with 4 seats, 2-bladed rotors, Lycoming O-540-F
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Here's one that didn't fly. Orlando Helicopter had various fanciful ideas for going beyond the basic S-58T re-engining, such as the Viking noted in the 1988-89 Jane's.

Much like Mil did to make the initial Mi-8 from the Mi-4...


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Sud S.58 turbine conversion model, International Helicopter Museum, Weston Super Mare, 2018


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Direct conversion of the Sikorsky S-56 by Westland, re-engined with Napier Elands, proposed August 1954 (ref. The Aeroplane July 11, 1958). Engines to be located fore-and-aft in more streamlined nacelles on the tips of the S56 stub wings.
In the lower left of this GE advert from Avweek there is a small but rare photo of the Sikorsky HSS-1 with twin T58 installation. First flew 30 January 1957.


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Brief mention in Flight of 1959 of the Piasecki [X]H-21D having flown with a pair of T58s:


Plus earlier 1957 reference:


I believe there was also a twin-T53 H-21 project but can't determine if it ever made it to hardware stage. Oh, this site claims it was c/n B-167 that was converted back to piston after testing!

Likewise B-168 converted back after T58 testing:

One or other was used for stability augmentation testing in 1959:

Are there any photographs of the converted Piasecki XH-21D turbine airframes ? (I'm curious as to intake/exhaust arrangement)

Cheers, Joe
Are there any photographs of the converted Piasecki XH-21D turbine airframes ? (I'm curious as to intake/exhaust arrangement)

AvWeek, 14 Oct 1957

New intake orifice aft of the main gear, and perhaps changes to the upper decking forward of the rear pylon?

Edit: plus two new exhausts, port-side aft. See next post.

Vertol H-21D Shawnee helicopter, fitted with two 1,024ehp. General Electric T58 gas turbines takes off from Philadelphia International Airport, Pa., on start of extensive flight test program under a BuAer contract for the U.S. Army. Contract totals $1.8 million, also involves ground-testing of a second turbine-powered Shawnee. T58-powered Shawnee is expected to show payload increase of 40%, speed increase of 50% and several thousand fee ceiling increase over standard H-21s powered by a single piston engine.


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The gubbins of the T58 installation, AvWeek 09 Dec 1957

Given the odd tandem arrangement, presumably the forward T58 breathed through the new orifice and the aft one breathed through the original "big hole". The two port-side exhausts are just discernable in the airborne photo.

The gearbox arrangement must have been curious.

Vertol Tests T58, T53

Vertol Aircraft Corp in-turbine-powered helicopters, offering a choice of General Electric's T58 (above) or Lycoming’s T53 (below) installations.

Either power package can be provided in a retrofit kit for Army or USAF use in the Vertol H-21. No commercial H-21s are in operation, but the company is offering its certificated version, the Vertol 44, to corporate and airline users.

T58 installation was made in an Army H-21D and developed under contract for the Army and Navy's Bureau of Aeronautics. It has been flying since September. The engines are in a tandem arrangement

Lycoming’s 53 was placed in a helicopter called the Vertol 105, with two engines located side-by-side, and flown
less than a month ago. The aircraft was developed by the company with the Army providing the engines.

Vertol says replacement of the H-21’s normal Wright R1820 reciprocating engine by two turbines results in a 40% increase in payload, plus a gain of 50 mph in additional speed.


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S-58T converted by Sikorsky to include a Pratt & Whitney PT6A-3 Twin PAC, similar to that installed in Bell 212 Twin Huey
Hey, Thanks. :)
For documentation purposes, here's it showing the company which used it, and most importantly its registration number which will help with tracking down where it came from,
although with that info being provided, it kinda looks like you already have.

(In 1970s we lived in Macon, Georgia, while Dad was at USN Recruiting Area 3 headquarters & even then people were calling Atlanta "Hotlanta" like on helo's side. I do not recall how the term came in to use.)

One of the two HUL-1Ms, Bell 47J with Allison 250 / T63.

BuNo 149838 and 149839

What remarkable is that four years later Westland started building the rattly, vibrating, piston-engined 47 for the British Army. So much missed potential for very little risk.


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