Northrop P-61 Ideas and Inspiration

[Kerick]

Thanks for the suggestions! I was thinking of late to post Vietnam so late sixties into the seventies. Markings could be US or South Vietnam or whatever shows up in the decal stash. Perhaps the aircraft get given to the Philipine government after Vietnam. Sort of like the A/B-26 story but with turbo prop upgrades. Numerous weapons choices.

[GTX_Admin]

My first preference would be to go the RR Dart path using something such as a pair of the Heritage Aviation Models Cavalier Turbo Mustang III conversions:




The S-2T conversion with TPE331s or PT6s would also be a good option, though I am not aware of a conversion kit for either (there was/is a 1/72 conversion though)



Another option might be to use a set up similar to the PT6 powered BT-67 Turbo Dak and using something like a Red Bear Conversion if you can find one (i have one in my stash but you're not getting that ):

[kitnut617]

If you go the Dart route, you could go this route too

[Kerick]

The Dart installation from the Cavalier Turbo Mustang III looks pretty good. Extra parts for carrying weapons too.
My one other thought was using regular Mustang Merlin noses and add a scoop to make it look like the PT6.

[elmayerle]

Unfortunately, Heritage Aviation Models is no more.  I think one of the antipodean specialist firms (Kiwi Resins?) do a conversion, or did a conversion.  I know Red Roo does/did a kit to model the Australian Dart-Mustang in 1/72 but I don't know if they do/did it in 1/48.

[kitnut617]

Heritage Aviation is now called Kits for Cash and Ian does have some resin conversions he didn't sell. They're under the Simian Stuff link on their website.

https://www.kitsforcash.com/

IIRC, in his latest news page, he said he sold all his other moulds to AlleyCat.

[GTX_Admin]

Unfortunately, Heritage Aviation Models is no more.  I think one of the antipodean specialist firms (Kiwi Resins?) do a conversion, or did a conversion.  I know Red Roo does/did a kit to model the Australian Dart-Mustang in 1/72 but I don't know if they do/did it in 1/48.

You can still occasionally find some Heritage Aviation conversions around the place such as eBay.
Kiwi Resins or Kiwi Models is out of business too.  Regardless, their conversion was not for the turboprop version:

The Red Roo one is 1/72 only.

[GTX_Admin]

Looking at the options and looking just at engine power (not factoring in weight or other dimensions):

P-61	RR Dart Conversion based upon Cavalier Mustang	S-2T based conversion	Conair Firecat based conversion	Convair CV-580 style conversion	Basler BT-67 style conversion
P&W R2800 Radial Piston	RR Dart Mk.510 (RDa.6) Turboprop	Honeywell TPE-331-15AW Turboprop	PT6A-67AF Turboprop	Allison 501/T56 Turboprop	PT6A-67R Turboprop
2000hp - 2800hp ea depending upon model fitted	1535 - 1,670 shp ea	1,645 shp ea	1,220 shp ea	3,750 shp ea	1,281 shp ea

From this quick analysis one can see that the power rating for most turboprop versions is much less than that for the original R2800s, though this is offset significantly by the reduced weight, with all turboprops listed being lighter than the R2800s, some significantly so such as the PT6 and TPE331 which come in at around 15 - 20% of the weight of the radial.

That said, given the powers/weights and moreso, for modelling purposes, the availability of kits/conversions, maybe using the Allison 501/T56 as the basis might be the way to go.  As indicated above, you could use the Convair CV-580 as the basis for this conversion.  This started off as the Convair CV-340 (see below) with two R-2800 CB-17 engines each rated at 2,500 hp (1,890 kW) and with three-blade propellers, thus giving commonality with the original P-61.



The CV-580 added (amongst other changes) two Allison 501 D13D/H turboprop engines with four-blade propellers, each rated at 3,750 eshp (2,800 kW).



Therefore, the conversions are very comparable.  Most importantly, from the model building perspective, you should be able to get parts by Lone Star Models - see https://www.lonestarmodels.com/store/p_109399/lsm-40469-p-3-cowlings-props:



Not only is this realistic based upon the real world, it is doable from a modelling perspective (though with still quite a bit of work to blend the engines in, especially given the P-61 has the twin booms) and also will look really different since I doubt anyone has done a T56 conversion of a WWII aircraft before.

[elmayerle]

I like the T56 suggestion.  Going with the Orion nacelles sounds like the best approach and I would suggest that the exhausts be angled to the outside of the booms and upward.  *chuckle* If you really want to disturb people further, also purchase and use aftermarket C-130J propellers.

[Kerick]

Or the Hamilton Sundstrand NP2000 propellers from the E-2 Hawkeye/C-2 Greyhound.

A huge thank you to GTX_Admin for that research. I thought about the T-56 but considered to to be too much for a direct replacement. This might just be the ticket. Now I'll have to look up the prop diameters but that will be easy. Maybe a story about the P-61 that found its way to Vietnam and sprouted two "lost" C-130 engines. Crazy things happen in a war zone. Hmmm, CIA, Air America needed an armed escort for its cargo planes.......?

[elmayerle]

Perhaps the CIA, via its predecessor organizations, had more in its classified "boneyard" than most would suspect?  I wonder how that nose would fit the A-6's avionics fit for night/all-weather action?

[kitnut617]

I wonder how that nose would fit the A-6's avionics fit for night/all-weather action?

Interesting comment that Evan  --- just last night I was reading an article about Gulfstream 1's in the very latest Air-Britain Aviation World (Summer 2019 addition) which arrived Thursday. There's some photos of USN Gulfstreams with A-6 noses attached to them. The article says the Gulfstream was a competitor of the Convair.

[Kerick]

And looks like RR Dart engines too.
How about the low light TV or IR systems from back in the day?

[elmayerle]

Yeah, the TC-4C Academe; all nine of them trained legions of A-6 bombardier-navigators.  From what I understand, it was considered a very good aircraft for its role (must have been pretty-much "right-on", records show only one was lost).

You might have a bit of a challenge blending an A-6 nose on to the nose of a P-61, but the TC-4C certainly shows it can be done cleanly.

[GTX_Admin]

Or the Hamilton Sundstrand NP2000 propellers from the E-2 Hawkeye/C-2 Greyhound.

Depends upon what era you are looking at the build being from.  The NP2000 only started being used around 2000.  It is actually a military derivative of the commercial, six-bladed 568F propeller which has been in service since 1995.  If used on a P-61, the airframe would be in excess of 50 yrs old be then so maybe pushing it.  As it was, in the real world the P-61s were effectively retired from service in 1950.  That said, a stretch into the 50s or even 60's might be doable though to the 2000s...well maybe a step too far (depending upon the degree of realism in your build).

For comparison, the CV-580 conversions thatI used as the basis of my recommendation took place starting in 1960.  Before that an experimental installation of Allison T56 engines (actually the earlier T38) into a CV-240 in 1950 was quite successful and the military YC-131C conversion first flew on June 19 1954 as well.  Therefore a T56 powered P-61 is not totally out of the question with the airframes only needing to be kept in service for another decade or so rather than half a century.

Now I'll have to look up the prop diameters but that will be easy.

P-3 Orion propeller diameter: 13 ft 6 in (4.11 m)
P-61 Black Widow propeller diameter: 146 in (3.72 m)

Therefore, the P-3 ones I mentioned earlier should work.

Maybe a story about the P-61 that found its way to Vietnam and sprouted two "lost" C-130 engines. Crazy things happen in a war zone. Hmmm, CIA, Air America needed an armed escort for its cargo planes.......?

Another option might be simply to say that for commonality purposes (with C-130s etc) the R2800s were replaced.  Moreover, the advantages of turbine power included less maintenance, lighter weight, and better performance which would also be a big plus.  For example, the conversion of a CV-340 to CV-580 increased the cruising speed from 284 mph to 342 mph, and the range from 2,000 to 2800 miles.

[GTX_Admin]

And looks like RR Dart engines too.
How about the low light TV or IR systems from back in the day?

You might consider the Tropic Moon III B-57G as a basis for something:




In fact, going back to my last post, maybe have the Turboprop P-61 operating alongside AC-130s in the Operation Commando Hunt aerial interdiction campaign.  In the real world AC-130s flew under F-4 Phantom II escort (to protect the gunship against heavy and concentrated AAA fire) but maybe in the alternate world, something a bit slower than the F-4 was sought hence the P-61.  This would also give reason for the T56 change so as to increase engine commonality and thus reduce maintenance burden.  If given a B-57G style undergoes fit out, the extra power might also come in use.

[elmayerle]

I like the idea of incorporating the Tropic Moon III gear, it makes a lot of sense and the P-61 would have the room for the electronics.   I could definitely see some pulled from storage and modified for this purpose.

[GTX_Admin]

Another option you might consider is swapping the engines/nacelles from a OV-1 Mohawk (though personally, I still like the T56 idea).  This would give you a pair of T53 turboprops at 1,400 hp (1044 kW) ea.  Less that the R2800s but again, lighter at about a third of the weight and commonality with UH-1s in Vietnam.  Moreover, you might put the R2800s back on the OV-1 to create a second whiff...

[tankmodeler]

The Dart installation from the Cavalier Turbo Mustang III looks pretty good. Extra parts for carrying weapons too.
My one other thought was using regular Mustang Merlin noses and add a scoop to make it look like the PT6.

PT-6s of the time period were relatively small, in the 450-750 hp range. 1700 hp engines, the larger PT-6 series, didn't come about until the early 70s through 80s and none of them hit the 2250 HP of the R-2800s. A late 60s PT-6 engined Black Widow will be a pig, from a performance p.o.v.

Just sayin'.

I used to work as a design engineer at P&WC on PW100s, 200s, 300s and 500s and the JT-15D.

[kitnut617]

An engine which would fit in your time frame is a RR Tyne. They were initially designed for the 2500hp range but when tested was producing over 4000hp. And I've found that the Tynes on an Atlantique have nacelles about the right diameter for R-2800's. I've been looking at putting a set on a DC-6 but it looks like Aircraft in Miniature are going to be doing a DC-7 conversion so I think I'll put them on a DC-7 instead.

[tankmodeler]

T-56s are a great choice. Same with Tynes, depending on the operator. Even if massively over-powered compared to the R-2800s, they would provide additional peacetime safety by allowing a max-weight engine out without risking the aircraft plowing into the woods at the end of the runway. WW2 era multi-engined aircraft were noticeably underpowered with one engine out and virtually suicidal if they lost an engine at max weight on take-off. The extra power from a T56 or Tyne would provide sufficient thrust to get you safely airborne to allow a controlled landing as needed.

[GTX_Admin]

An engine which would fit in your time frame is a RR Tyne. They were initially designed for the 2500hp range but when tested was producing over 4000hp. And I've found that the Tynes on an Atlantique have nacelles about the right diameter for R-2800's. I've been looking at putting a set on a DC-6 but it looks like Aircraft in Miniature are going to be doing a DC-7 conversion so I think I'll put them on a DC-7 instead.

The RR Tyne would be an option except I don't know of any available in 1/48 which is the scale build being looked at here.

[kitnut617]

Ah! right, forgot it was in that funny scale   

[jcf]

P-61 nacelles are round at the firewall and cylindrical for much of their length.
Many Dart installations are basically a cylinder, use a tube of appropriate size with a
tapered nose, glue a smaller tube, or tubes depending on desired  intake size and sand
the end into the desired shape.

Why muck about trying to fit non-cylindrical cowlings off of some other kit?, which
would also cost more.
 

[Kerick]

So much great info here! Thanks so much. Now I will have a lot to consider. Maybe in time for the "out of retirement" GB.