Piston Airliners Converted to Turbine Power

The Viscount hit the spot before the jets really became viable, and they sold 445 of them, a respectable figure for those days, to over 70 operators.

The Vanguard was probably too late and most were taken by BEA, as many of us who buzzed between Edinburgh and London fondly remember.

(Was Argus the only case of turboprop (conversion…well, variant) to piston?)

Possibly in a production sense, but Athena and Balliol also went from turbo-prop designs to piston engined production machines.

Other piston to turbine conversions was the Hermes V (Bristol Theseus), and the Miles M.69/Handley Page HPR.2 Marathon 2 ( AS Mamba).

I would think that the lack of success of early turbo-prop conversions is almost the opposite to post#2, in that it was still far cheaper for airliners to buy and operate piston engines, not just for fuel burn reasons, but also for number of ex war-time engines (many unused) kicking about, more general know how on maintaining and certifying them, and longer life cycles etc. Also many flying and ground crews available with piston experience.
This is especially the case for the second-line operators that were still using piston types right into the late 1960s.

(not a conversion but a variant: ) On 22 April,1947 MoS brought to Cabinet a request for $ for a Bristol licence for L-649/Centaurus to lead in to L-849/Theseus. UK was fast burning its 15/7/46 $ Reconstruction Loan, such that £ collapsed 14/7/47, so Cabinet declined. That, for me, is the core what if of modern UK Aero.

About same time a French DC-6 licence collapsed.

(Was Argus the only case of turboprop (conversion…well, variant) to piston?)

Having flown CV-580 about 6,000+ hrs, Carstadt (mod Dove) and a few flight in Volpar Beech 18. Reliability of the engine, Mechanics trained in jet engine work, availability of fuel, more power. I can tell you when I lost an engine in the 580 was no big deal. Which happened on more than a few occasions

Chris

I too enjoyed many enjoyable hours in all three, but I was not sure if they were “commercially successful”.

Having spent many hours flying in all three of those, I’d say they were sound commercial aircraft, the Viscount in particular a worldwide success.

Great aircraft to fly in – spacious, smooth and with REAL windows to look out of !

To put in perspective the commercial viability of converted types, were the Britannia, Viscount and Vanguard actually perceived as being commercially successful at the time?

My Constellation book (M J Hardy, David and Charles, 1972) has it that Lockheed wanted to go ahead with a turbine-powered L-1449 in 1953/4 but were held up by delays in the PT2F engine, a civil version of the T-34.
A number of alternatives were looked at including the Tyne and Bristol Orion from the UK and civil versions of the T-52 and the T-56.
The two British engines were in their early stages and the T52 never saw production, so it came down to the T-56, or more accurately the civil 501.
By this time the 501-powered Electra was taking shape and the jets were coming. Lockheed pulled the plug on the turbine Constellation in early 1955 and instead went ahead with the piston-powered L-1649, which had the new wing originally designed for the L-1449.
Strictly-speaking we’ve drifted off-topic here: the L-1449 was a turbine version of a Constellation, but it was not a conversion of an existing airframe.
Boeing did re-engine a few C-97s, btw, as the YC-97J with T-34s.
As far as later conversions are concerned, like the Basler DC-3, another driving factor is the more limited availability of avgas in remote areas as opposed to jet fuel.

Not to mention turbine conversions of Goose (Geese?), Mallards and Albatrosses.

This question prompted me to break out my Lockheed book from Putnams to see what it said.
There wasn’t one clear reason why a turbine Constallation wasn’t produced with, or converted to turbine power (though the US military and Lockheed operated test beds).

Perhaps the wings weren’t efficient enough to take full advantage of the conversion? (Possible, but I’m not sure their wings were any less efficeient than those used by other straight-wing turbines.).
Or more likely, money.
The large airlines were spending money on jets, and the Lockheed probably thought its R&D budget would be better spent on the Electra and Douglas probably thought likewise in favor of the DC-8.
There weren’t enough Stratocruisers in operation to give Boeing the option of re-engining the fleet.

The Convair conversion is interesting.
They were mainly used on regional routes by smaller carriers (North Central, Lake Central, Frontier, etc.). For those short routes, I’d assume speed would be less a factor than operating economics.
In fact, crusie speed only went from 299 mph for the piston 440 to 325 for the Allison-powered 580 and 306 mph for the Dart-equipped 600 aircraft.

Turbines cost – a lot! So does the paperwork. Also presumably the range is reduced i.e. turbines have a higher fuel burn p/h but the fuel tank size remains the same.

Beech 18 Volpair turbo conversions come to mind, and going smaller the De Havilland Canada Beaver and Otter

Quite a few Herons were converted (and enlarged) to turboprops.

Roger Smith.

Only 13 of 149 – it was the Saunders ST-27

Quite a few Herons were converted (and enlarged) to turboprops.

Roger Smith.

Please alter the thread title, doesn’t sound bad actually but visually it disturbs! 😉

Don’t forget the Basler DC-3 conversions….a modest ongoing success!
Lockheed flew Super Connies with the Electra engine and the even bigger T-34 turboprop so they had real data to evaluate them….they looked great anyway!

[QUOTE= ruling out unpressurised types such as Dakotas.
I’ve always felt that a turboprop Constellation might just have been a goer, but as a new-build rather than a conversion.
Don’t forget, too, that the Boeing 367-80 was flying by then and Lockheed could possibly see the writing on the wall for propeller-engined long-haulers.[/QUOTE]

Dart Herald – another fine example of a piston design converted (and subsequently manufatured) with Turboprop power…

Fuel burn and conversion costs as suggested, plus the fact that to make the best use of turbine power, an airliner needs to fly high, ruling out unpressurised types such as Dakotas.
I’ve always felt that a turboprop Constellation might just have been a goer, but as a new-build rather than a conversion. It would have needed the right engine at the right time and the necessary investment in the mid-1950s, though, at a time when Lockheed’s thoughts on big turboprops were on the C-130 and, a little bit later, the Electra.
Don’t forget, too, that the Boeing 367-80 was flying by then and Lockheed could possibly see the writing on the wall for propeller-engined long-haulers.

I am only guessing but one factor may have been cost. In most cases it was probably more cost effective for an airline to buy new / newer aircraft already fitted with turboprops and woith lower flying hours than it was to convert their existing already well used piston engined fleet.
Don’t forget that conversion of an existing fleet would involve considerable “down time” for each airframe and this would have to be covered by purchasing or leasing a replacement aircraft adding even more to the costs of each conversion.