P-40 with Griffon engine

[Elvis]

Seems like there was a post there and now it's gone ....?

Yes there was.

If the question was "if it was so easy to put in a two stage Merlin, why didn't they do it?" - I would say the main issue was just a matter of the availability of the engines, and their preference for the P-51. For some reason the first production run of Packard Merlins was the single stage, two speed Merlin XX. That is what they used in the P-40 F and L (and also squandered in some other aircraft that weren't used or were re-engined before use, in part because the British seemed to have an aversion to the Packard built Merlins, at least initially).

By the time Packard was making the 60 series Merlins, or V-1650-3, the military brass far preferred the P-51 due to it's superior range and very high speed. No doubt a P-40 with a two-stage Merlin would have broken 400 mph, if only because peak engine power would be achieved at higher altitude and in the thinner air, but it would not have been as fast as a P-51B. The P-51A series was ~40 mph faster than a P-40 with the same Allison engine. That was the advantage of all that streamlining.

The P-40 was probably a bit better in terms of manueverability and resistance to damage, but USAAF was really interested in speed above all other qualities. Even range, which ultimately seemed to matter more, took a back seat.

I assume the reason they didn't use the two-stage Allison V-117 type that was used in the Kingcobra was because it was much more bulky..?

Basically, yes, but after I posted my question, I went back and re-read Greg's post and realized he'd already answered that question, so I deleted it.
Sorry, must've fallen asleep towards the end of his post. I didn't recall reading that when I asked my question.
...maybe we should include a post delete button (I believe we used to have one) in the next upgrade of the site.

...anyway...

A lot of posts about increasing engine power, in order to increase overall performance (one of mine, included), but wouldn't an increase in engine power simply mean you can drive a prop that creates more thrust?
Whether its a larger diameter, or an extra blade or two is added, its the increased thrust that will yield greater overall performance.
Same prop with more powerful engine would only seem to increase acceleration, because a more powerful engine could swing the same prop with less effort.
So if we move to a propeller of greater thrust, then that increases axial forces against the airplane, so now were looking at longer wings and/or longer vertical and horizontal stabilizers, which would increase drag and make the plane less agile.
If you include the extra weight the two-speed/two-stage supercharger would create, along with balance issues and the weight differences of using a heavier engine (both Merlin and Griffon are heavier than the Allison), are we really going to realize that much of a performance increase over the "stock" application?
It seems the biggest thing we might notice is the plane's ability to perform at a higher altitude, but more performance overall?
....I don't know.

Elvis

 

[Schweik]

The P-40 went from around 800-900 hp in the P-36, to up to ~1400 (P-40F/L) to 1500 hp in the P-40K, so that was a fairly major jump. This did cause some stability problems especially when changing speed rapidly, requiring a lot of trim adjustment pilots found to be a nuisance. The fix was relatively simple though, it was just to extend the tail 20 and then 30". This did not add much weight and seemed to have little effect on drag either.

The issue of how more power gets converted to faster speed is admittedly a little murky to me, but that is true for any aircraft. I gather it does sometimes mean a bigger prop with more blades or wider blades, it can also (from what I understand, I could be wrong) equate to flying at higher RPM and / or different pitch settings. It can also just mean that maximum power is available for a longer time and (in the case of two speed and especially two stage engines) at higher altitude. 1,200 hp at Sea Level will give you a much lower speed than the same 1,200 hp at 25,000 ft.

 

[Schweik]

Another issue with higher power ratings was torque which could make it much harder to roll one way than the other while at full power. Many aircraft were designed to address this either by offsetting the rudder slightly or by making one wing slightly shorter than the other (as on the Macchi MC 202)

 

[maxmwill]

Do it as they did on the latest XP-40Q, that have had two radiators relocated in the wings. Shaves drag, and counter-balances the longer & heavier engine.

Why not an annular radiator, as on the Shackleton? As you stated earlier, the Griffon was similar in size to the Merlin, hence the installation. As the Allison engine has similar dimensions to the Merlin, a Griffon installation wouldn't require extensive shoehorning.

 

[tomo pauk]

Why not an annular radiator, as on the Shackleton? As you stated earlier, the Griffon was similar in size to the Merlin, hence the installation. As the Allison engine has similar dimensions to the Merlin, a Griffon installation wouldn't require extensive shoehorning.

Aircraft should go prettier, not uglier. Plus, the aircraft will become too nose-heavy due to the heavier engine coupled with heavier cooling system.
I don't recall stating in no uncertain words that Griffon was of similar size to the Merlin, care to post a link?
The 1-stage V-1710s and Merlins were quite a bit shorter and lighter than than 2-stage versions, that has implications on CoG for the designer team.

BTW - the Avro Shackleton Griffons didn't have a 'pure' annular layout like it was the case for many German engines and the trial Sabre instalation as tested on the Tempest.

 

[Elvis]

The P-40 went from around 800-900 hp in the P-36, to up to ~1400 (P-40F/L) to 1500 hp in the P-40K, so that was a fairly major jump.

Yes, that is a fairly major jump, however, didn't the propeller always stay the same?
That is; a 3 bladed prop, 9.5' in diameter.
This is my point. You can put a million HP powerplant in the plane, but if the propeller stays the same size and configuration, the plane will always handle it.
It's like that thread from many eons ago, where someone asked if the prop and engine off a P-51D were put on a P-40, wouldn't it have better performance, since the P-40 was a lighter aircraft to begin with?
There was a very long discussion about how planes and props are matched to each other, and while there is some "wiggle room", you can't go too overboard with the size of the prop (or the engine), or else the plane will be almost impossible to handle (too much to be of any practical use, anyway).
We're kind of getting into the same discussion here, but from a different angle.
Maybe what you're quoting is the fact that the prop proved efficient through those power ranges, but to try to pull more thrust by utilizing a more powerful engine and a larger prop and you're going to start incurring handling issues which might be more easily remedied by designing a whole new plane....possibly designed around (or including, as an element) the new larger prop.
I still like the idea of the bored out Allison with the single stage two speed supercharger (maybe using the bigger 12.18" impeller) and sticking with the stock prop.
Would pretty much match F/L variants, power-wise, and it would happen in a lighter and more well balanced package.
...JMHO.

 

[Dash119]

I said what i said about Race 2332 because the amount of fuselage in front of the wing leading edge seems to be longer than for a stock Sea Fury. That's my eye talking, not a tape measure.

I'm not seeing the same stretch on this that you are... I don't have the exact dimensions of the Centaurus vs. R-3350, but we are swapping one twin row radial for another. In addition there is a complete rework of the fuselage and cowling on 232, including what seems to be a ram air scoop at the top of the cowling. There may be some difference in the weight, but I would guess the length difference between the two motors to be somewhat insignificant in terms of overall fuselage length.

Now if you want to talk about Dreadnought and the R-4360 swap we are on the same page...

 

[wuzak]

Why not an annular radiator, as on the Shackleton? As you stated earlier, the Griffon was similar in size to the Merlin, hence the installation. As the Allison engine has similar dimensions to the Merlin, a Griffon installation wouldn't require extensive shoehorning.

The Griffon was roughly the same width as the Merlin.

But it was longer and taller. And heavier.

To go from the single stage V-1710 to the two stage Griffon you are looking at 700lb+ extra weight, possibly 1,000lb+ when a bigger prop and radiators are included.

If all that weight is in front of the CoG you have to add extra weight behind the CoG. Depending where that weight is added, that could be another 500lb+ added to the weight of the aircraft.

 

[wuzak]

Because from what I've read, many of the Packard-engined aircraft (largely made in Canada) that were sent to Britain were subsequently re-engined with British made Merlins. Many were also kept in Canada as a kind of tertiary level of defense where they never did much. If you had doubled the number of P-40 F / L in the Med in say 1943 and 1944 that would have helped. I think the Soviets could have used them too.

So you think the British, having negotiated for an American supply and giving away their technological secrets (radar, jet engines) in order to access American manufacturers, would just swap out the Packards for UK built Merlins?

This makes little sense, since if they had enough Merlins to do that they didn't need Packard Merlins at all.

 

[wuzak]

Wasn't talking about the XP_60, particularly the radial versions. Was talking about a revised P-40. The XP-60A or XP-60B kght be close, but still not what I ws talking about.

I wasn't talking about the radial versions, or the XP-60A or XP-60B either.

The XP-60D was the XP-60 re-engined with the Merlin 61. And the XP-60 was a P-40D with new wings.

The XP-60D proves your point about fitting the 2 stage Merlin in the P-40 airframe. Because it was a P-40 airframe, apart from the wings.

 

[Shortround6]

For some reason the first production run of Packard Merlins was the single stage, two speed Merlin XX.

The reason was that the deal with Packard was signed in Sept of 1940, about the same month that Hawker started delivering Hurricanes powered by the Merlin XX engine.
Please remember that if took months for Packard to redo all the drawings for the Merlin (not tolerances., but to go from either 1st order projection to 3rd order or vice versa, I forget at the moment.) So Packard signed a deal for the latest, most up to date Merlin the British had in production.
Your other option for Packard at the the time was a single stage/single speed Merlin.

A viable Griffon engine is even further away than the a two stage Merlin in timing.

 

[gjs238]

Maybe focusing on a P-40 with a R-2800 would be more realistic.

It seems that this could have been achieved at a relatively early date had not the USAAC dragged Curtiss down the paths of the Continental XIV-1430-3 inverted vee engine, British-built Merlin 28, Allison V-1710-75 engine and a General Electric B-14 turbo-supercharger, Allison V-1710-75 engine and a Wright SU-504-1 turbo-supercharger, Chrysler XIV-2220 sixteen cylinder inverted vee engine, Merlin 61, contra-rotating propellers...not sure what else I missed.

 

[Shortround6]

Maybe focusing on a P-40 with a R-2800 would be more realistic.

It seems that this could have been achieved at a relatively early date had not the USAAC dragged Curtiss down the paths of the Continental XIV-1430-3 inverted vee engine, British-built Merlin 28, Allison V-1710-75 engine and a General Electric B-14 turbo-supercharger, Allison V-1710-75 engine and a Wright SU-504-1 turbo-supercharger, Chrysler XIV-2220 sixteen cylinder inverted vee engine, Merlin 61, contra-rotating propellers...not sure what else I missed.

OK, take Hawk 75 with a 1200lb experimental radial engine and replace it with a 2270lb radial (engine used in the B-26, two speed, single stage) that needed a huge propeller

While the P-60 series did wind up with R-2800 engines they also got new wings and new landing gear and by the time the R-2800s were stuffed in how much remained of the P-40 fuselage is debatable.

 

[NevadaK]

At what point do all of these proposed changes to accommodate a new engine, whether Griffon or some other power plant, really just result in an entirely new airplane? It seems to me that the point of re-engining a given airframe during a critical time period would be to seek a substantive performance increases for the least amount of disruption to the production stream. As this thread has gone on there have been ever greater proposals to redesigning the P-40 to the extant that its no longer the original plane and no longer buildable with the existing assembly jigs and so forth. Just my opinion.

 

[gjs238]

OK, take Hawk 75 with a 1200lb experimental radial engine and replace it with a 2270lb radial (engine used in the B-26, two speed, single stage) that needed a huge propeller

While the P-60 series did wind up with R-2800 engines they also got new wings and new landing gear and by the time the R-2800s were stuffed in how much remained of the P-40 fuselage is debatable.

Well, yeah.
What would they have gotten had the XIV-1430-3 or XIV-2220 versions been successful?

Regardless, they were looking for a successor to the P-40.
With the benefit of hindsight, it seems safe to say that a R-2800 powered successor (as opposed to a XIV-1430-3 or XIV-2220 powered one) could have/should have been a less risky endeavor.

 

[gjs238]

At what point do all of these proposed changes to accommodate a new engine, whether Griffon or some other power plant, really just result in an entirely new airplane? It seems to me that the point of re-engining a given airframe during a critical time period would be to seek a substantive performance increases for the least amount of disruption to the production stream. As this thread has gone on there have been ever greater proposals to redesigning the P-40 to the extant that its no longer the original plane and no longer buildable with the existing assembly jigs and so forth. Just my opinion.

USAAC was seeking a successor to the P-40.
The changes you mention don't seem to have been the issue, the issues were the dead-end paths I mentioned previously.

 

[wuzak]

Maybe focusing on a P-40 with a R-2800 would be more realistic.

It seems that this could have been achieved at a relatively early date had not the USAAC dragged Curtiss down the paths of the Continental XIV-1430-3 inverted vee engine, British-built Merlin 28, Allison V-1710-75 engine and a General Electric B-14 turbo-supercharger, Allison V-1710-75 engine and a Wright SU-504-1 turbo-supercharger, Chrysler XIV-2220 sixteen cylinder inverted vee engine, Merlin 61, contra-rotating propellers...not sure what else I missed.

The list of engines you mention were for the XP-53 and XP-60, not the P-40.

The British built Merlin 28 was used only on the prototype XP-60 and prototype P-40F because the Packard built engine was not yet available.

The reason the P-40 got the V-1650-1 was that the P-40 needed improved performance and the USAAF had 3,000 V-1650-1s to put somewhere (a stipulation in the production contract that 1/3 would be for US use).

 

[Shortround6]

For those who think the US (and Packard) got a bad deal by signing up for the Merlin XX in the summer of 1940 please look at what Allison was doing at the same time.
Allison was recalling and rebuilding ALL of the early production -33 engines in the early P-40s in order to meet the Guaranteed power output and service life. This recall program carried on until the spring of 1941. Until rebuilt existing engines were limited to 2770 rpm instead of 3000rpm and a corresponding reduction in manifold pressure.
Allison was fooling around with the -39 prototype engines.

The Merlin XX might have been viewed as manna from heaven

 

[gjs238]

The list of engines you mention were for the XP-53 and XP-60, not the P-40.

The British built Merlin 28 was used only on the prototype XP-60 and prototype P-40F because the Packard built engine was not yet available.

The reason the P-40 got the V-1650-1 was that the P-40 needed improved performance and the USAAF had 3,000 V-1650-1s to put somewhere (a stipulation in the production contract that 1/3 would be for US use).

Again, regardless, a lot of dead-ends were pursued for a potential successor to the P-40.
Designations changed.
Would a Griffon powered P-40 have ended up being designated a P-40?

 

[gjs238]