"Baby" Hawker Tempest I/Fury I with Merlin power

[BarnOwlLover]

I'm wondering what a fighter along the lines of the Tempest I or Fury I would've been like, but smaller and designed to use the Rolls-Royce Merlin instead of the Napier Sabre. I know that it'd be a good deal smaller to get similar performance specs, and all.

I'm bringing this up because of some of the performance specs I've read of various projects (XP-51F/G, A P-51B used by Rolls-Royce as a Merlin engine test bed, the proposed Merlin powered Mustang FTB, etc), as well as when I inquired about the Miles M23A interceptor, and that it was supposed to have wing mounted radiators similar to the Mosquito/Hornet, I instantly thought about a scaled down Tempest I or Fury I type fighter.

Anyone have any feelings or thoughts about this?

 

[Howard Gibson]

I'm wondering what a fighter along the lines of the Tempest I or Fury I would've been like, but smaller and designed to use the Rolls-Royce Merlin instead of the Napier Sabre. I know that it'd be a good deal smaller to get similar performance specs, and all.

I'm bringing this up because of some of the performance specs I've read of various projects (XP-51F/G, A P-51B used by Rolls-Royce as a Merlin engine test bed, the proposed Merlin powered Mustang FTB, etc), as well as when I inquired about the Miles M23A interceptor, and that it was supposed to have wing mounted radiators similar to the Mosquito/Hornet, I instantly thought about a scaled down Tempest I or Fury I type fighter.

Anyone have any feelings or thoughts about this?

By WWII standards, the Merlin was a small engine. It worked well in small single engined fighters like Spitfires and Mustangs. Hawker developed the Typhoons and Tornados as sucessors to the Spitfires and Hurricanes. It made sense to develop them to use the new 2000HP engines. With 2000HP, the new aircraft could be well protected and heavily armed, and they were. The continued success of Spitfires was due to the installation of the 37litre Griffon engines.

When did laminar flow wings come in? The Typhoon was under development during the late thirties.

 

[BarnOwlLover]

It should be noted that there were 2000 hp Merlins (though mostly R&D test engines) almost as soon as the two stage versions were becoming operational. Though the two stage superchargers required a fair amount of power to run properly (as did most mechanical superchargers), the move from single stage to two stage opened up more life for the Merlin and made more development possible. Same of course applied to the Griffon, though that was originally designed as a single stage engine that was originally rated for 1600 hp in early development, which the two stage Merlin was easily capable of making that from an engine that was almost 10 liters smaller in displacement, and weighed about the same as a single stage Griffon/350 lbs less than a two stage Griffon.

However, production 2000 hp Merlins (be it Rolls-Royce or Packard produced) didn't really appear until 1945, and even then both it and engines like the Griffon and Napier Sabre and Bristol Centaurus (and the US Pratt & Whitney R-2800, R-4360 and Wright R-3350) were on the verge of obsolescence due to the development potential of jet engines.

I'm also curious how a lightweight Mustang would look with leading edge wing radiators like the Mosquito/Hornet or the Tempest I/Fury I. It would take away from the work done on the ventral radiators, but I think it would be interesting to consider, as well as if Hawker made a follow on to the Hurricane that was Merlin powered alongside the Typhoon and Tempest/Fury, as well as a Merlin powered Spiteful (which Supermarine investigated in case the two stage Griffon ran into issues).

I should also note that the Miles M23A I mentioned was (though not dimensionally) not a small aircraft, with a 50 ft wing span and was longer than a Spitfire IX. However, it weighed less than 7500 lbs, which is comparable to the XP-51F/G Mustangs.

 

[Howard Gibson]

It should be noted that there were 2000 hp Merlins (though mostly R&D test engines) almost as soon as the two stage versions were becoming operational. Though the two stage superchargers required a fair amount of power to run properly (as did most mechanical superchargers), the move from single stage to two stage opened up more life for the Merlin and made more development possible. Same of course applied to the Griffon, though that was originally designed as a single stage engine that was originally rated for 1600 hp in early development, which the two stage Merlin was easily capable of making that from an engine that was almost 10 liters smaller in displacement, and weighed about the same as a single stage Griffon/350 lbs less than a two stage Griffon.

However, production 2000 hp Merlins (be it Rolls-Royce or Packard produced) didn't really appear until 1945, and even then both it and engines like the Griffon and Napier Sabre and Bristol Centaurus (and the US Pratt & Whitney R-2800, R-4360 and Wright R-3350) were on the verge of obsolescence due to the development potential of jet engines.

I'm also curious how a lightweight Mustang would look with leading edge wing radiators like the Mosquito/Hornet or the Tempest I/Fury I. It would take away from the work done on the ventral radiators, but I think it would be interesting to consider, as well as if Hawker made a follow on to the Hurricane that was Merlin powered alongside the Typhoon and Tempest/Fury, as well as a Merlin powered Spiteful (which Supermarine investigated in case the two stage Griffon ran into issues).

I should also note that the Miles M23A I mentioned was (though not dimensionally) not a small aircraft, with a 50 ft wing span and was longer than a Spitfire IX. However, it weighed less than 7500 lbs, which is comparable to the XP-51F/G Mustangs.

The 2000HP Merlins were running on 150 octane fuel. 150 octane makes Napier Sabres, Bristol Centauruses and P&W R2800s more powerful too. 2600HP Merlins were using water injection as well.

 

[Shortround6]

I would note that on many of these engines just quoting the power output without giving the altitude is rather misleading.

Merlin 130 using 25lbs boost (100/150 fuel) 2020hp at 1500ft, 1845hp at 14,250ft.
Griffon 66 using 25lbs boost (100/150 fuel) 2300hp at 500ft , 2060hp at 15,750ft.

 

[z42]

I'm also curious how a lightweight Mustang would look with leading edge wing radiators like the Mosquito/Hornet or the Tempest I/Fury I.

I suspect a LE radiator Mustang would have substantially higher drag than the historical one. E.g. comparing the various Tempest radiator installations in https://ww2aircraft.net/forum/attachments/napier-annular-pdf.674007/ the LE radiators were only barely less draggy than the Tempest V chin radiator.

 

[Deleted member 68059]

The 2000HP Merlins were running on 150 octane fuel. 150 octane makes Napier Sabres, Bristol Centauruses and P&W R2800s more powerful too. 2600HP Merlins were using water injection as well.

I have never seen a Sabre power rating document on 150 grade not even a Sabre VII (yes I know it was "cleared" for it, but you`ll note that the permitted
boost on 150 was no higher than for 130, probably because it was already at some mechanical limit, the "clearance" was in this case merely saying it was
safe to run on the fuel, which had a higher lead content).

The chart below suggests the same is true of the Centaurus, but somewhere I do have a rating for the Centaurus with 150 grade AND water
which was a boost increase.

 

[BarnOwlLover]

I suspect a LE radiator Mustang would have substantially higher drag than the historical one. E.g. comparing the various Tempest radiator installations in https://ww2aircraft.net/forum/attachments/napier-annular-pdf.674007/ the LE radiators were only barely less draggy than the Tempest V chin radiator.

To be honest, I thinking that the Hawker LE solution wasn't optimal. The Firefly and Mosquito/Hornet LE radiators probably better exploited the Meredith effect, though the radiator trunking was longer fore and aft (and probably did a better job of managing the airflow), which is an advantage of the ventral layout. Granted, on the Mosquito and Hornet, unless you wanted inward retracing landing gear (which would probably compromise wing fuel tank capacity), there wasn't a much better place to put the radiators. And on the Firefly, you have the rear cockpit, not to mention that the main fuel tank was between the front and rear cockpits.

Only big issue I'd have (and even that's probably overthinking/making too much of it) is fitting a downwards firing camera/vertical camera in say a XP-51F/G or P-51H arrangement due to how long the rear trunking fairing is. But then again, F-6/RP-/RF-51s didn't use vertical cameras, and Australian Mk 22 was a P-51D/K converted for PR/FR duties, and there was never a RF version of the P-51H.

 

[z42]

To be honest, I thinking that the Hawker LE solution wasn't optimal.

Well, if so, what makes you think Hawker would be able to design a substantially better LE radiator for the baby Tempest that is the topic of this thread?

The Firefly and Mosquito/Hornet LE radiators probably better exploited the Meredith effect, though the radiator trunking was longer fore and aft (and probably did a better job of managing the airflow), which is an advantage of the ventral layout. Granted, on the Mosquito and Hornet, unless you wanted inward retracing landing gear (which would probably compromise wing fuel tank capacity), there wasn't a much better place to put the radiators. And on the Firefly, you have the rear cockpit, not to mention that the main fuel tank was between the front and rear cockpits.

I think on a single engine fighter volume is pretty limited. In particular volume close to the CG is prime real estate for fuel tanks. The Mustang, as I'm sure we've all read, had serious CG issues due to the extra fuselage tank installed behind the pilot. If you'd switch to LE radiators, that would seriously eat into the wing tank capacity. Where would you store all that fuel? I don't think it would work to have an even bigger aft fuselage tank in place of the ventral radiator.

On a twin it's different, as the landing gear can conveniently be designed to retract into the engine nacelles behind the engines, and the guns and ammo will all be in the front. Leaving a lot more space in the wings for both LE radiators and fuel.

 

[Shortround6]

Mustang had issues because of the size of the tank. Adding 47% more fuel well aft of the CG caused problems. However adding 33% more fuel was easily manageable.

Every plane was different due to different choices. Even the Mustang, trying to stick even 60 gallons it the place where the Merlin Mustangs tried for 85 gallons in the older Allison Mustangs would have been a horror show.

The problem with leading edge radiators on single engine fighters is that while they reduce the frontal area compared to the chin/underwing radiators they are not going to give much Meredith effect. You need room, both volume and length to get it to work right.

You also need to balance the total drag which includes the drag of the air flowing both out sided the duct/s and inside the ducts. Building a large fuselage, locating the radiator/s inside and routing the air through nearly flush openings may look good but you have a lot of drag in the ducts.

 

[BarnOwlLover]

Not to mention a couple of packaging issues. One, the already mentioned ducting has to be a certain length to make the Meredith effect work right/have significant benefit, and two, if you're going for a LE radiator, the wing's front spar has to be fairly close to the LE. That restricts wing design, not to mention the landing gear has to be behind the front spar on a single engine fighter, which makes packaging large fuel tanks between spars difficult (why the Hawker Tempest had a lengthened front fuselage due to it's thinner wing vs the Typhoon).

Both of these are much easier to deal with on a twin engine aircraft.

Oddly, the XP-51F/G and the P-51H had a different CG than the B/C/D/K models. I did read that the P-51H for the Pacific was being looked at as running a fairly large rear fuselage fuel tank, which was calculated even when full to not have a huge impact on handling.

However, the main production Merlin Mustangs, let alone the Allison powered ones, though they had much greater range than the Spitfire or Hurricane or Typhoon (it wasn't until the Tempest that the RAF had a fighter that could match the Allison Mustangs on range on internal fuel), weren't designed as long range bomber escorts. It just turned out that adding a bit of fuel to them would give them the range, though some of it would have to burn off due to CG induced handling issues. The lightweight Mustangs/P-51H represented the whole "what would Schmund do?" scenario, as in knowing what you know now, what would you change.

And Sydney Camm was looking at running a Mustang-inspired radiator on the Hawker P.1027, a Rolls-Royce Eagle development of the Typhoon/Tempest line. That was until the P.1030 was developed from it, which used LE radiators. Camm and his aero guys really liked LE radiators, though the Hurricane did experiment with/incorporate a lot of Meredith's recommendations (though not all of them, due to redesign requirements), and the Rolls-Royce Vulture Henley test bed did use a radiator reminiscent of the Mustang and the P.1027.

 

[z42]

One, the already mentioned ducting has to be a certain length to make the Meredith effect work right/have significant benefit, and two, if you're going for a LE radiator, the wing's front spar has to be fairly close to the LE.

Wouldn't that be the other way around, you want the main spar relatively far back to the LE so you have space for the radiators and the ducting? If you look at the Mosquito, it seems that's what they did there, the radiators extend quite far ahead of what would be the "natural" LE if you follow the curve of the wings outboard of the engines.

Another way to get more space in front of the main spar would be to have some sweep on the LE instead of the traditional design of a straight perpendicular LE and all the tapering done with the RE?

Also for LE radiators, I wonder if there's some practical way to have something like a sliding exit opening, so you don't have to push the exit flap out into the slipstream?

And Sydney Camm was looking at running a Mustang-inspired radiator on the Hawker P.1027, a Rolls-Royce Eagle development of the Typhoon/Tempest line. That was until the P.1030 was developed from it, which used LE radiators. Camm and his aero guys really liked LE radiators, though the Hurricane did experiment with/incorporate a lot of Meredith's recommendations (though not all of them, due to redesign requirements), and the Rolls-Royce Vulture Henley test bed did use a radiator reminiscent of the Mustang and the P.1027.

Admittedly the P.1030 looks very sleek, but, the proof is in the pudding. I wouldn't want to stake my head on the drag of that installation, being an aerodynamics ignoramus.

 

[BarnOwlLover]

Actually, if you look at a Tempest cutaway, the front spar is fairly far forward:

http://www.airwar.ru/image/idop/fww2/tempest/tempest-4.gif

All World War II Hawker fighters had this trait.