P51 with Griffon engine?

The Mustang with the Allison engine was a decent aircraft hat was made into an excellent aircraft when fitted with the Merlin.

Would it have accepted a Griffon engine and if so would it have been worth the effort to install it?

I ask because obviously the Spitfire was able to step from the Merlin to the Griffon and it made a difference to performance that was worth the effort involved to fit the new engine.

How much engineering effort was required to upgrade the Spitfire and would the Mustang have been harder? easier? the same? and would it have gained the same level of improvement in performance?

Thoughts?

Yes - it 'Could Have' and one of the Reno Unlimited racers has a Griffon with a contra rotating prop.

That said, Schmued wanted to stay on the Merlin track for the Mustang - and already achieved 495mph in the XP-51G with the 14 S.M. engine with combat load of internal fuel

The Spitfire was a short range absolute high performance machine, fitting the Griffon engine kept it at the front in performance. For the P51, it relied on the low fuel consumption of the Merlin while cruising to rendezvous point and on station as an escort plus the trip home coupled with its prodigious performance on max boost in combat. I suspect that the Griffon would have made it slightly faster with a slightly better rate of climb but it would have used much more fuel while cruising due to increased swept volume and increased drag due to weight and frontal area. A Griffon powered P51 would outperform a Merlin engined one in almost every area except the one that made the P51 a game changer and that is its range.

The answer to the question lies in the fuel consumption of the Griffon v the Merlin while in cruise mode.

As I recall the changes to fit the Griffon engine into a D model Mustang and then repositioning other components to restore center of gravity are fairly significant. Could that change even have been made on a airplane that needed to remain combat capable???

Instead of fitting a Griffon to a Mustang, just build the CA-15

Jets were on the way!

Jim

Modifying the Spitfire with the Griffon didn't take much change at all; the first aircraft was Mk.IV airframe DP845, which, fitted with the Griffon IIB became the prototype of the Spitfire XII and was test pilot Jeffrey Quill's favourite aircraft. This was the machine Quill provided for the infamous 'fly-off' at Farnborough, in which Arnim Faber's Fw 190, a Hawker Typhoon and a Spitfire were to be put in the air against each other. The Spit was to be just an ordinary production machine to demonstrate the other two aircraft's superiority to it, but Quill took DP845 and caned the pair of them, causing dignitaries present to sit up in alarm; it got the Griffon engine Spit into production. Read Quill's excellent book Spitfire, A Test Pilot's Story for more.

The Spitfire XIV, fitted with a Griffon 65, the two-speed, two-stage Griffon was based on the Spitfire Mk.VIII airframe, so modification of standard production aircraft was initially carried out, as it had been with the Merlin 45 installation in the Spit II to produce the V and the Merlin 61 in the Spit V to produce the IX; the first production Spitfire XIIs were actually Mk.V airframes.

There were proposals to install a Griffon in the Mustang, but it was to be an almost entirely new aircraft; it was a Rolls-Royce proposal named (unimaginatively) the Flying Test Bed and the engine was to be mounted above the wing and aft of the cockpit, which was repositioned forward of the wing. A full scale mock up was constructed using Mustang I AM148's wings and rear fuselage. Info here from the War Thunder gaming site, but it gives images and a line drawing:

FTB Mustang - Suggestions

Building a few would be no great trick, building hundreds is a great trick. AND the questions include when in addition to how many.

First production MK XII Spitfires show up in the fall of 1942, but the Griffon II engine they use is a single stage engine and while the power down low is very good power at altitude is not so hot being only a bit better than a Single stage Merlin.
What is going on at this point in time is that the experiments with the two stage Merlin in the Mustang which offers about the same power thousands of feet higher are starting, orders are being placed before testing is done and Packard is just starting production of two stage Merlins.
Now as an indication of timing Jeffery Quill flew a Prototype Spitfire with two stage Griffon on 20 January 1943 but it took until October 1943 for the first production machine to fly and until Dec 1943 for it to enter squadron service.
At this point Packard is building 450-689 two stage Melrins per month (and will build over 1200 in March-44) and North American in building 284-332 Mustangs per month and will build 482 in March-44.
There is NO Griffon production line in the US (or Canada), it will take around a year or more to set one up and it will take another 6 months to get production up to triple digits.
Shipping engines from England to the US is pretty much a non-starter. Griffon production is very low and the shipping time is measured in weeks if not months. Best case for Griffon Mustang production is the Dallas Plant (maybe, it only built 3 types of aircraft although in huge numbers) as it is only a few hundred miles from the port of Houston.
Now are the performance advantages of a Griffon Mustang going to outweigh the production disruption of introducing it and can it be introduced in service soon enough to have any real effect on the progress of the war?

As an unknown in planning you have the progression in fuel which allowed both the Merlin and Griffon to go from 12lbs boost to 15/16lbs then 18lbs and then to 21 and 25lbs boost which allowed the Merlin to keep increasing in power to "match" the Griffon if allowed to use 3-4lbs more boost.
In other words if the Fuel had not improved and boost had been limited to say 12-15lbs more effort might have been made to build and introduce the Griffon engine to more types of aircraft. But the increased boost levels allowed increases in performance with little or no disruption in production.

Stick the water-injection kit on the 2-stage Packard Merlin already in late 1943/early 1944, and the Mustang goes 470+ mph?

Why not just install the Merlin 130 from the Hornet. You get over 2000 hp and installation would be pretty straightforward

Timing??
Merlin 130/131s don't show up until some point in 1945.

Stick to the Merlin. Mrs Florence Edgar doesn't wanna be retrained on the Griffon. Just wants the war to end and go home.

Shortround6 said:

Timing??
Merlin 130/131s don't show up until some point in 1945.

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The prototype Hornet was flying from around mid 1944 so its not as silly an idea as it first seems. Of course its behind the Griffon in the development cycle, but not by as much as most people think. The significant changes to the P51 to fit the Griffon would probably take longer to design, test and implement.
The biggest problem would be the change to the production priorities of Rolls Royce at a time when the RAF didn't need better aircraft as the jet was clearly the way ahead.

There were quite a few changes to the 100 series engines compared to the under 100 MK numbers. Stronger crankcase, the new end oiling system for the crankshaft, overhung 1st stage in supercharger, stronger valve springs in addition to minor stuff like relocated accessories, the new down draft intake system and SU fuel injection system.
They might very well have been flying prototype engines in 1944 but production engines had to wait for 1945.

No one is trying to pretend that there no or few changes needed to install the Merlin 130 into a P51. All I am saying is that the changes would be a heck of a lot less than trying to fit the much bigger and heavier Griffin.
As for timescales I stand by my view that had there been an urgent need for the Hornet the Merlin 130 would have been available sooner, plus the time needed to alter the P51 to cater for the Griffin would be substantial.

Graeme said:

Stick to the Merlin. Mrs Florence Edgar doesn't wanna be retrained on the Griffon. Just wants the war to end and go home.

View attachment 345247

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I wouldn't bet on that. A lot of women thrived on the money, freedom, friends and independence that war work gave them

Now are the performance advantages of a Griffon Mustang going to outweigh the production disruption of introducing it and can it be introduced in service soon enough to have any real effect on the progress of the war?

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I think this is the most important issue. Production of Griffon engines was never that high, and replacing the Merlin would have caused a huge disruption. It took quite a time to supply Spitfire Mk XIV in good numbers to RAF.

Glider said:

Why not just install the Merlin 130 from the Hornet. You get over 2000 hp and installation would be pretty straightforward

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Shortround6 said:

Timing??
Merlin 130/131s don't show up until some point in 1945.

Click to expand...

Glider said:

The prototype Hornet was flying from around mid 1944 so its not as silly an idea as it first seems. Of course its behind the Griffon in the development cycle, but not by as much as most people think. The significant changes to the P51 to fit the Griffon would probably take longer to design, test and implement.
The biggest problem would be the change to the production priorities of Rolls Royce at a time when the RAF didn't need better aircraft as the jet was clearly the way ahead.

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I think the V-1650-9 in the P-51H was basically the same as the Merlin 130/131 in the Hornet.

alejandro_ said:

I think this is the most important issue. Production of Griffon engines was never that high, and replacing the Merlin would have caused a huge disruption. It took quite a time to supply Spitfire Mk XIV in good numbers to RAF.

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Indeed, production was king.And Griffon production was barely getting started.

So you have to pick and choose where you use the motors.

As to how the Mustang could have received Griffons, one of the suggestions for the Mustang X program could have been adopted - bring the airframe over to the UK and have Rolls-Royce fit the Griffon at a modification depot.