Pratt vs Wright

[kitplane01]

Did either engine maker have an advantage over the other?

Speaking of the late war large radial engines, my impression is that they gave similar service, at similar cost, with similar fuel and reliability. They had really reached about the maximum level of what's possible. Is this true?

P.S. Yes, I know about turbo compounding (power turbines), which is mostly after the war and mostly not great anyway.

 

[swampyankee]

Overall, probably not. Post-war, P&WA's leadership was willing to spend the money to move into the gas turbine era. C-W's wasn't.

 

[ThomasP]

Does anyone know the reason that CW did not do the same as P&W?

 

[GregP]

I'd say Pratt was better for the 2,000 HP-class engines. I'm thinking R-2800. The Wright R-2600 was decently reliable but wasn't in the 2,000 HP class; it was 1,500 - 1,850 HP or so. It was about a wash for the 1,000 - 1,350 HP class. The R-1820 and R-1830 were both reliable. The Pratt was somewhat smoother by virtue of being a 2-row radial with more power strokes per revolution, but both were good engines. The Wright was simpler and probably required less maintenance per flight hour, but neither were exactly prone to failure or other running issues. I left out the R-4360 because it wasn't used much during the war. It WAS used after the war and spawned the R-2180-E which was two rows of an R-4360.

The Wright R-3350 was a very temperamental engine, especially near the beginning of its operational lifespan, and gave a lot of trouble during the B-29 effort. The prototype caught fire (engine) andkilled the Boeing chief test pilot, Eddie Allen just as one example. Later, after the war, it seemed to be quite reliable when being operated by flight engineers commercially but still somewhat unreliable when operated by pilots alone. The big difference was that flight engineers tended to operate the throttles smoothly and by the book, while pilots tended to fly the airplanes first and operate the throttles as an afterthought to flying. Flight engineers were generally much smoother with throttle changes. Big radials like to operate at one rpm for extended periods and do NOT like changing rpm, especially when cold.

By "like," I mean that using smooth operating techniques, an operator will generally get longer engine / main bearing life than someone who throttle-jockeys the engines while taxiing on the ground in order to make turns. This from people who operate them today. There are definitely techniques that operators can use to help engine life. Military pilots do not pay for the engines, so they don't really care as long as it works for THIS flight. Private operators DO care since the money comes from their own pockets and they invest both time and money to learn the best ways to make their radials "happy." A happy radial costs you less money to own over the lifetime of the engine.

 

[swampyankee]

Does anyone know the reason that CW did not do the same as P&W?

The post-WW2 history of C-W is not entirely happy: it fell from what was probably the largest manufacturer in the aviation business to a bit player between 1945 and today. Certainly, there were some technical fails both during and after WW2, both on the engine and airframe side of the business, but many companies had a few of those, and were able to (at least temporarily) rebound (one example: Vought had two pups in a row, the F6U and the F7U, then produced the impressive, albeit flawed, F8U and the sterling A-7). C-W seemed to go from weakness to weakness, never badly enough to actually fold, but consistently losing chunks of market: airframes, then engines.

 

[kitplane01]

I It was about a wash for the 1,000 - 1,350 HP class. The R-1820 and R-1830 were both reliable. The Pratt was somewhat smoother by virtue of being a 2-row radial with more power strokes per revolution, but both were good engines. The Wright was simpler and probably required less maintenance per flight hour, but neither were exactly prone to failure or other running issues.

I find it strange that a 2 row, 14 cylinder engine, and a 1 row, 9 cylinder engine, were equivalent. I would have thought, given two different design choices, one would work better in practice.

Wikipedia tells me the one row engine 54", and the two row 48". The difference in frontal area is 54^2/48^2 = 26 percent. That's about 3.3 more square feet of nose area.

 

[P-39 Expert]

I find it strange that a 2 row, 14 cylinder engine, and a 1 row, 9 cylinder engine, were equivalent. I would have thought, given two different design choices, one would work better in practice.

Wikipedia tells me the one row engine 54", and the two row 48". The difference in frontal area is 54^2/48^2 = 26 percent. That's about 3.3 more square feet of nose area.

True, but the Wright 1820 could "hide" the oil cooler intakes between the cylinders meaning no extra nose area. The Pratt 1830 had to have the scoop for the oil cooler in the airstream increasing the frontal area probably offsetting the additional 3.3sqft.

 

[Shortround6]

Oil cooler is in the "scoop" under the wing visible over the landing gear. Other planes did use larger oil coolers for the same engine, depending on the speed and use of the airplane. Bombers tended to use larger oil coolers.

 

[Admiral Beez]

The post-WW2 history of C-W is not entirely happy: it fell from what was probably the largest manufacturer in the aviation business to a bit player between 1945 and today .

I wonder what happened in the back rooms of the Pentagon and Congress. We should recognize the potential influence of who knew who. If Defence firms, like P&W in the later postwar period can skate a little close to the rules, I'm sure they did the same back in the 1940s and 50s.

 

[Shortround6]

Maybe there was but there were other things going on. Both P&W and Wright had been kept out of turbojet development during the war leaving them to play catch up.

P&W bit the bullet and struck a deal with RR to licence RR jet engines, specifically the Nene/j42 and Tay/J48. Wright similarly struck a deal to licence Bristol jet engines, the Sapphire/J65 in 1950 but that 3 years after the P&W/RR deal for the J42 P&W had also done their own work on a turbo prop, the PT2/T34 starting in 1945.
P&W had a 3-5 year head start with turbine engines. P&W was working on a two spool turbojet in the late 40s, and in 1949 Luke Hobbs suggested to the engineering dept that they throw it out and start over. The result was the J57.
Wrights decision to "buy" the Sapphire shows they are behind the curve.

 

[swampyankee]

The reports I've read have said that Curtiss-Wright was far more loath to spend any money on R&D and product development than was P&WA; it got far enough behind the curve so there was no catching up.

 

[Admiral Beez]

The reports I've read have said that Curtiss-Wright was far more loath to spend any money on R&D and product development than was P&WA; it got far enough behind the curve so there was no catching up.

That could be the case. Their XF-87 Blackhawk looks sort of like an American Canberra, before the Martin B-57.

They're still in business today, with 45% of revenue from defence spending Curtiss-Wright Corporation - Home

 

[GregP]

Hi Kitplane01,

I find it odd, too, that the Wright and the Pratt are basically interchangeable, but they are. Not really, because they fit different engine mounts and connections, but practically, yes.

Case in point:
1) The Pratt R-1830-S1C-G: 1,200 HP @ 2,700 rpm, diameter 48", dry weight: 1,250 lbs. Generally the series is 800 to 1,350 HP. Most 1,000 - 1,350 HP.
2) Wright R-1820-G2: 1,000 HP @ 2,200 rpm, diameter: 54.25", dry weight: 1,184 lbs. Generally the series is 700 to 1,525 HP. Most 1,000 - 1,350 HP.

 

[fastmongrel]

I have noticed that Curtiss Wright bought working reliable jet engine designs then spent a lot of time and money tweaking and productionising the engines so they were heavier, took more man hours to build and were less reliable. If CW thought they needed so much work why buy the design.

Pratt and Whitney on the other hand bought a design learnt from it then used the knowledge to build their own engines.

 

[swampyankee]

That could be the case. Their XF-87 Blackhawk looks sort of like an American Canberra, before the Martin B-57.

They're still in business today, with 45% of revenue from defence spending Curtiss-Wright Corporation - Home

I certainly never said they weren't in business; I said they were a minor player in the aerospace world. From what I've read of their history (I'm certainly far from an expert!) they were consistently profitable and always paid a dividend; it's just that the company's executive leadership wasn't willing to spend enough to keep in the top tier. I think they're far from unique in that regard, even within the aerospace world, but they're the sort of poster child for short-term thinking that should be (but almost certainly isn't) a focus of study in business schools.

 

[BiffF15]

Hi Kitplane01,

I find it odd, too, that the Wright and the Pratt are basically interchangeable, but they are. Not really, because they fit different engine mounts and connections, but practically, yes.

Case in point:
1) The Pratt R-1830-S1C-G: 1,200 HP @ 2,700 rpm, diameter 48", dry weight: 1,250 lbs. Generally the series is 800 to 1,350 HP. Most 1,000 - 1,350 HP.
2) Wright R-1820-G2: 1,000 HP @ 2,200 rpm, diameter: 54.25", dry weight: 1,184 lbs. Generally the series is 700 to 1,525 HP. Most 1,000 - 1,350 HP.

Which types used those two engines and at what HP levels?

Cheers,
Biff

 

[Shortround6]

Which types used those two engines and at what HP levels?

Cheers,
Biff

Unfortunately the numbers are from wiki. The Pratt&Whitney R-1830-S1C-G was was really a phantom engine as P&W records list 2 specifications but none manufactured.
As a general rule of thumb the early R-1830s were 1250lbs or under but were under 1000 hp. The ones over 1000hp were generally 1400lbs or so. This is for single stage engines.
see: http://www.enginehistory.org/Piston/P&W/R-1830/R-1830Index.pdf
for a complete listing.

The R-1820 is even more complicated as it was in production for around 30 years with a number of diffrent models that only had the bore and stroke in common.

 

[BiffF15]

Unfortunately the numbers are from wiki. The Pratt&Whitney R-1830-S1C-G was was really a phantom engine as P&W records list 2 specifications but none manufactured.
As a general rule of thumb the early R-1830s were 1250lbs or under but were under 1000 hp. The ones over 1000hp were generally 1400lbs or so. This is for single stage engines.
see: http://www.enginehistory.org/Piston/P&W/R-1830/R-1830Index.pdf
for a complete listing.

The R-1820 is even more complicated as it was in production for around 30 years with a number of diffrent models that only had the bore and stroke in common.

SR6,

Are these the two different engines found in the F4F / FM-2?

Cheers,
Biff

 

[pinsog]

SR6,

Are these the two different engines found in the F4F / FM-2?

Cheers,
Biff

Yes. F4F and P36 (Hawk 75) used both engines

 

[Shortround6]

SR6,

Are these the two different engines found in the F4F / FM-2?

Cheers,
Biff

Yes but the F4F used a two stage supercharger version and the FM-2 used the first of the H series R-1820s, which while still using a singe stage two speed supercharger had next to no interchangeable parts with the R-1820 used in the SPD-5. The engines were around 1560lbs and 1330-1340lbs respectively.

The early versions of the engines were used in the commercial DC-3s according to customer preference. Lockheed Hudsons used both engines. You may find other planes that used both engines in different models.