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Turboprop conversions – built and unbuilt

riggerrob

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My interest in turbo-prop conversion is from a skydiver's perspective. I have jumped several of the conversions mentioned earlier. The best skydiving pilots run engines until scheduled overhauls, then many replace stock engines with more powerful, after-market, STCed engine conversions. As old radial engines wore out and spare parts got scarce, many jump-planes were converted to turboprops.

I have a few hundred jumps out of the (Beech 18 tail-dragger) Westwind Beech that worked at Hinckley, Illinois back during the early 1990s.

A Beech 18 conversion (Westwind 4?) sits behind the museum at Victoria International Airport (B.C. Canada). With PT-6A engines, tri-gear and a single rudder, it does look like a "poor man's King Air", but all that labout probably cost almost as much as a King Air ... similar to the Beechcraft Duke with PT6A engines.

On that note, the first Beechcraft King Airs were a batch of U-21s built for the US Army. They were un-pressurized (square windows) Queen Air airframes modified with a swept fin and PT-6A-20 engines. A few of those (non-certified military pattern) PT6A engines were installed in Murphy Moose kit planes. Mooses (plural ?) have been powered by a wide variety of engines: Lycoming and Continental flat 6s, Vedeneyev radials and turboprops.

The museum at Victoria Airport is only a short distance from where Viking builds new Twin Otter 400s. During August 2015, they had 4 shiny new Twin Otters in the final stages of fitting-out for customers. One sat on a huge set of Aerocet wheel-floats.

Twin Otter trivia: several skydiving centers brag about their "Super Otters" which are DHC-6-200 or -300 re-engine with PT6A-27 or -35 engines. Most of the conversions were done under one-time-only FAA 337 forms.

The first DHC-4 Cariboo conversion to PT6A engines was done in Gimli, Manitoba. It flew well, but the designer's son crashed the prototype when he forget to remove control locks (pretty scary video!). Pen bought the rights to the Turbo-Cariboo conversion. I also found the remains of a Saunders ST-27 or ST-28 (?) at Gimli in 1992.

Republic Seabee conversion C-GNVS sat idle at Pitt Meadows Airport (B.C. Canada) for a decade. Pilot Andrew Whyte (?) said that it flew great, but guzzled fuel like crazy! The regular belly fuel tank was supplemented by extra fuel tanks in both wing roots. With full fuel, it could only carry two pilots ... no cargo. With its pointy nose and plenty of extra fairings (aft end of cabin and tail surfaces) it barely looked like a Seabee. The turbo-Seabee was a test-bed for an un-built new amphibian.
At one point we had Seabees with 4 different engines at Pitt Meadows: the original Franklin, a Lycoming GO-480 conversion, a Corvette conversion and the Turbo-Seabee. Andrew Whyte described the Corvette as the best combination of power and fuel consumption.

Another trivia point is that the Soloy Conversion is the only version of the Cessna 207 that can fly on floats, because it is the only version with enough horsepower to lift off from lakes.
I have a few jumps from Soloy Cessna U206 conversion and love the cargo door. The Soloy 206 climbs like stink .... and it does stink of turbine exhaust! Soloy also modifies the wing when they install Allison of Rolls-Royce 250 engines. The Soloy U206 is my second-favorite Cessna jump-plane after the 208 Caravan.
Stock Caravans climb slowly with stock 600 or 675 horsepower engines. Cessna eventually certified an 848 (?) horsepower version of the PT6A-140 engine, but impatient a variety of conversion companies (Aero Twin, Blackhawk and Texas Turbines) obtained STCs to install more powerful engines. Texas Turbines has STCs to install Honeywell engines in Caravans.

My old friend Van Pray Junior is in the later stages of obtaining an FAA Supplementary Type Certificate to install a PT6A-20 engine in a Cessna U206 jump-plane. His conversion resembles the Golden Eagle (?) conversion for Cessna 210, but VP Jr. started from scratch.

Has anyone mentioned the Soloy conversions of Bell 47 and Hiller helicopters?

Also note that Pilatus Porters were built with at least three different turbo-prop engines: Astazou, PT6A and Garrett. Garrett TPE-331-1-101F engines were only installed in AU-23 Porters license-built by Fairchild Hiller and most of those flew missions for Air America/CIA in the jungles of Laos and Cambodia. After the war, they were sold to the Royal Thai Air Force, but during the 1990s, a few were re-imported to the USA, over-hauled and worked at sport parachute centers in Washington State. One of those Porters crashed in Chilliwack, B.C. when a pre-maturely deployed parachute tore the tail off. Fortunately, every one on board survived because they wore parachutes .... even the pilot!

Fairchild Porters competed directly with Helio Couriers and Helio Stallions for US Army and CIA contracts. The AU-24A Helio Stallion started as a turbo-conversion of the (piston) Twin Courier, but quickly evolved into a much larger airplane powered by a single PT6A engine. A single Helio Stallion hauled skydivers in the USA until it crashed at Perris Valley, California killing pilot Jim Lowe.

The Fletcher Air Parts FU-24 and Cresco agricultural airplanes evolved into the current-production Pacific Air Craft 750 with a PT6A engine and large-diameter fuselage. The PAC 750 has been marketed as the "first airplane designed specifically for skydivers" .. funny how the PAC 750 was updated at the same time that a lower-cost, but larger-volume fertilizer was introduced to New Zealand??????
Hah!
Hah!

On a historical note: I have never seen a PBY Catalina flying boat converted to turboprops.
The Catalina's replacement: Canadair CL-215 water-bomber was designed with radials because they were so inexpensive during the 1960s and 1970s, but as radial spare parts dried up, Canadair converted the production line to CL-415 turboprops.

On another historical note, Canadair built the Bristol Britannia airliners and air-freighters with stock turbo-props, but de-converted the airframe to Wright radials when they designed the CP-??? Argus. Back during the 1950s, radial engines offered better fuel economy. An Argus set a record by staying on patrol for something like 24 hours (before the RCAF adopted inflight refueling). Ironically, the Royal Canadian Air Force eventually (1980s) replaced their worn out Argus piston-pounders with Lockheed P-3 Orions powered by Allison turboprop engines. Fortunately, by the 1980s, turboprops had developed much better specific fuel consumption.
 

Apophenia

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Great stuff riggerrob ... and plenty of BC content ;D

riggerrob said:
Has anyone mentioned the Soloy conversions of Bell 47 and Hiller helicopters?
So far, we've stuck to fixed-wing conversions. But there's plenty of scope for a 'Turboshaft conversions – built and unbuilt' thread.

BTW: The CL-28 Argus Mk.2 (mentioned in our 'Turboprop to Piston' section) became the CP-107 in the post-1968 designation scheme.
 

riggerrob

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Has anyone mentioned the Russian-built Technavia SM-92?
It's airframe looks like a Brossard with a swept rudder stolen from a Turbo-Beaver. Finist competes directly with Beavers and Brossards and Porters.
Like the Sukhoi 26 conversion - that started this thread - the Finist started with a Vedeneyev radial engine but eventually acquired a Walter 601 turboprop.
Several agonists have worked as jump-planes on Europe. Most recently, a Turbo Finist crashed in Italy after its engine failed. Fortunately, good piloting skills and good seat belts limited injuries.
 

riggerrob

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Apophenia said:
Added: Vazar Aerospace's proposed Turbo Husky, a PT6A conversion of the Canadian Fairchild F-11 Husky bush aircraft.
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24965.html#msg24965
...

Sadly, Vazar's Turbo Husky never got beyond the "marketing survey" stage.
Pity!
Husky might have become a great bush plane.

Husky was one of earliest airplanes with a cargo ramp under the tail. The Husky's ramp was specifically sized for the cargo canoes favoured by trappers and traders and prospectors working across Northern Canada during the 1940s.
But there was plenty of room for improvement on the original Fairchild (of Canada) Husky. Only a dozen Huskies were made and only a couple remain in museums.
My buddy J.H. still smiles when he remembers the weekend (early 1980s) he spent skydiving from an original Fairchild Husky in Price Rupert, British Columbia, Canada. He loved the large cabin and canoe-sized hatch under the tail. The tail hatch allowed them to drop static-line students clear of the floats.
Sadly, the last Husky crashed in Prince Rupert harbour a few weeks later. It was trying to take-off ... rough water ... strong crosswind ... when it ran out of rudder.
Like many floatplanes, Fairchild's Husky barely had enough rudder to takeoff from land, but not nearly enough rudder when afloat.
Original Huskies had a cabin almost as big as a DeHavilland (single) Otter, but only a 550 Horsepower Alvis Leonides radial engine, which made for long take-off runs and "slow" climbs to cruising altitude.

In comparison, DHC-3 Otters only had 650 horsepower. Single Otters earned the nick-name "stone boat" for their ability to lift huge loads from lakes. Unfortunately, Otters' needed the rest of the afternoon to climb out of the mountain valley! On a good day, a single Otter climbed at only 850 feet per minute.
Hah!
Hah!

Vazar's illustrations show a slightly enlarged vertical tail and a greatly enlarged engine compartment housing a turboprop producing about 900 horsepower
 

riggerrob

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Skydivers eagerly await the certification of Gippsland/Mahindra's Airvan 10 utility airplane. About 300 of the original piston-pounding, Gippsland Airvan 8 are flying at dropzone a upgrading from piston-pounding Cessna's. Most skydivers marvel at the Airvan's taller and wider cabin and wax poetic about its 50 inch wide inflight door.
Airvan 8 pilots grumble that "it needs more power and more rudder."
Mahindra promises to silence those critics with a Rolls Royce 450 horsepower turboprop and stretched fuselage. The longer fuselage will increase the tail moment arm, improving yaw stability and control with existing components.
Sorry if this list sounds like and advertisement for Mahjndra/Gippsland. I only made one skydive from an Airvan 8 and rather enjoyed it. I think the Airvan 10 will make a perfect upgrade for Cessna DZs that are currently struggling with a trio of 182s and 206s and want a larger, faster airplane, but doubt that they will be able to keep a 14 place airplane (Beech King Air 90 series. Cessna Caravan, Quest Kodiak, etc) busy enough to hot-load. Hot-loading (and hot-refuelling) reduces (hot-cold) cycle costs while selling more jump tickets per (airframe) hour.
 

riggerrob

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Not sure where they fit ???? but several piston-pounding, US military airplanes were retrofitted with GE T34 jet engines to improve take-off performance.

US Forest Service Fairchild C-119 water-bombers were retrofitted with a single jet booster engine above the wing centre-section.

USAF Fairchild C-123 were retrofitted with a jet booster engine under each wing.

USN Lockheed P2 Neptunes were retrofitted with a jet booster engine under each wing.

North American OV-10 Broncos were retrofitted with jet booster engines over the wing centre-section. AFAIK this modification was only done to military-surplus Broncos towing targets for West German AAA.
 

Kiltonge

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Digging for more details, but Soloy flew a Navajo Chieftain in 1989 or earlier re-engined with a pair of the obscure Teledyne-Continental TP-500E turboprops of 510 shp each.

All I've found so far is the TCDS for the engine, FAA reference E6SO.

Update: and a nacelle photo from Flight in November 1988. Seems to have been displayed at the NBAA convention that year.

Update 2: Flying Magazine, June 1989

The TP-500 engine was a licensed development based on an original design by UK company Noel Penny Turbines ( see third attachment, extract from book The Nearly Engine ). Flicking through Jane's of the 1980s reveals that the engine was "first flown in a Cheyenne II on 29 September 1982" and Flight notes that it languished for another six years before certification due to market conditions. Also some references that Air Mod was planning a conversion of the Baron with a pair of TP-500s but the engine appears to have sunk into oblivion by the 1990s, possibly due to the collapse of the Penny company in the late 1980s.

Update 3: The airframe involved was PA-31-350 c/n 31-7852108 which at the time was N83CF. Subsequently de-converted back to piston-power and continues to fly in 2015 as N369KJ. Doesn't look like Soloy made it as far as an STC for the conversion.
 

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Kiltonge

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Vardax Hotter: DHC-3 Otter N9707B re-engined with a 750 shp PT6A-135 giving a 800 lb improvement in payload. The actual engineering was contracted to Serv-Aero of Salinas, CA.

Ah, disregard the above: Vardax of Bellingham, WA was a holding company of many interests who later formed the subsidiary Vazar Aero, who are listed above. I'll leave this as a reference in case anyone is searching under the alternative name.

President of Vardax at the time was Dara Wilder.
 

frank

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ISTR having seem a drawing of a PBY converted to RR Darts, for use in forest fire fighting.
 

robunos

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Is this connected to the 'Mississippi Marvel' program at all... ? ::)

cheers,
Robin.
 

Apophenia

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Thanks folks! The Cessna 336/337 and Piper Navajo section are now updated :D

frank said:
ISTR having seem a drawing of a PBY converted to RR Darts, for use in forest fire fighting.
Frank: All 'PBY' conversions efforts seem to have been about Canadian-built Cansos. There was the Trans-Caribbean Turbo Canso, another (possibly) from Field Aviation, and the proposed (but unbuilt) Avalon Turbo-Canso ... which was definitely to have been Dart-powered.
 

Apophenia

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Falcon 402 (South African Cessna 402 conversion to Walter M601D) and planned Consolidated B-32 turboprop project added.

Also Beech 60 Duke conversion to twin PT6A-21 powered Rocket Engineering Turbine P-Baron and to single-engined Falcon Duke
 

Sundog

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That TP O-2, especially the one in the painting, is very cool looking. As for the duct, it just looks like more weight and drag than it's worth. Of course, maybe being quiet was more important than performance for the Sandcrab?
 

weirc

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The following attachments are taken from 'Flight, March 5th, 1983'

With regard to the Mississippi Marvel, I believe a modified version was built to compete for the same requirement.

Colin
 

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Mark Nankivil

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Greetings All -

With thanks for the help from friend Mark Aldrich, here is a brochure artwork for a turboprop conversion of the Catalina proposed by Avalon Ltd. It was meant to extend the useful life of their fleet but nothing came of it.

Enjoy the Day! Mark
 

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Stargazer2006

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The article about the Cessna O-2ST "Sandcrab" seems to indicate funding by Saudi Arabia.
Another source online claims the type was developed for Iran...
Who's right? Who's wrong?
 

Apophenia

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Mark: Thanks for the Dart Canso pic ... do you have access to the actual Avalon brochure?
 

Mark Nankivil

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Sorry Apophenia, I don't.

Enjoy the Day! Mark
 

Apophenia

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Thanks Mark.

A range of unbuilt Grumman Albatross turboprop conversions have been added. Also a Consolidated Catalina turboprop conversion by Len Curreri (abandoned in favour of the new-built NNC ClipperSpirit - a projected turboprop Albatross re-imagined in carbon fibre).
 

Kadija_Man

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Apophenia said:
Thanks Mark.

A range of unbuilt Grumman Albatross turboprop conversions have been added. Also a Consolidated Catalina turboprop conversion by Len Curreri (abandoned in favour of the new-built NNC ClipperSpirit - a projected turboprop Albatross re-imagined in carbon fibre).
Where have they been "added"? You keep mentioning that you've "added" these aircraft somewhere. Where?
 

Apophenia

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Kadija_Man said:
Where have they been "added"? You keep mentioning that you've "added" these aircraft somewhere. Where?
Okay,

Albatross and Catalina conversion are under TRANSPORTS (CIVILIAN & MILITARY)...; Cessna 402 and Beech Duke conversions are under LIGHT AIRCRAFT...; and Consolidated B-32 turboprop project is under MILITARY PISTON-TO-TURBOPROP

Here are the links for all the separate listings:

PISTON/TURBOPROP TEST BEDS
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24962.html#msg24962

PISTON-TO-TURBOPROP -- AGRICULTURAL AIRCRAFT
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24966.html#msg24966

PISTON-TO-TURBOPROP -- TRANSPORTS (CIVILIAN & MILITARY), WATERBOMBERS, ETC.
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24965.html#msg24965

PISTON-TO-TURBOPROP -- DE HAVILLAND/DE HAVILLAND CANADA CONVERSIONS
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24969.html#msg24969

PISTON-TO-TURBOPROP -- CONVAIR 240 SERIES
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24967.html#msg24967

PISTON-TO-TURBOPROP -- DOUGLAS DC-3/C-47 (TURBO-DAK) CONVERSIONS
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24968.html#msg24968

PISTON-TO-TURBOPROP -- AGRICULTURAL AIRCRAFT
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24966.html#msg24966

LIGHT AIRCRAFT (INCL. MILITARY & EX-MILITARY TRAINERS)
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24963.html#msg24963

MILITARY PISTON-TO-TURBOPROP (other than dedicated Trainers)
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg24964.html#msg24964

JET TO TURBOPROP CONVERSIONS
http://www.secretprojects.co.uk/forum/index.php/topic,1070.msg23790.html#msg23790
 

Stargazer2006

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Apophenia said:
Here are the links for all the separate listings
Thanks for this, Apophenia. I for one wasn't even aware there was any rhyme or reason to this topic!
 

Apophenia

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Skyblazer said:
... I for one wasn't even aware there was any rhyme or reason to this topic!
I'm not sure there ever was, Skyblazer. But, like Topsy, it just 'grow'd' :D My subject heading are pretty arbitrary but hope the links help.
 

kaiserbill

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Isn't the Yak-152 powered by an aero-diesel engine rather than a turboprop?
It's also a new design.
 

GTX

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kaiserbill said:
Isn't the Yak-152 powered by an aero-diesel engine rather than a turboprop?
Correct:

http://eng.irkut.com/products/74/
http://www.ainonline.com/aviation-news/defense/2016-06-22/new-yak-152-trainer-will-come-alternate-powerplants
 

Grey Havoc

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http://www.janes.com/article/64580/basler-offers-bt-67-gunship-to-philippines
 

ZacYates

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Apophenia said:
PISTON-TO-TURBOPROP -- AGRICULTURAL AIRCRAFT

[Conv = conversion, Evol = design evolution]

UNBUILT

CAC CA-25 Winjeel trainer (R-985) [Evol] into agricultural derivative (PT6A) -- proposed follow-on to CAC CA-28 Ceres.
Where can more information on this proposal be found?
 

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In the Chinese press recently (http://www.chinadaily.com.cn/china/2017-01/09/content_27898575.htm) was the Xueying 601 Snow Eagle, which, according to the registration, is a Basler BT-67 turbo conversion of a Douglas DC-3.
 

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boxkite

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@Apophenia, cannot find this conversion in the lists - maybe a new entrant: PZL-104 with Walter M601 turboprop, now located in Kazakhstan. See http://www.airplanemart.com/aircraft-for-sale/Single-Engine-TurboProp/1986-PZL-104-Turbine-conv/13074/.
 

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Silencer1

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TsrJoe said:
Scottish Aviation turbo Pioneer
Thank you! Very interesting.
IMHO, this couldn't be threated as "turbo conversion", however.

It's not just a change of pistons fro turboprops, but entire wing, empennage, undercarriage.
Degree of similarity with Twin Pioneer is the same, as between Basler BT-67 and C-47 :cool:
 
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