Reggiane RE-2007 - What if?

[Twitch]

I put up a pic of this plane before http://www.ww2aircraft.net/forum/aviation/italian-bombers-3022-4.html?highlight=Re-2007 and cheddar cheese said it was never a design concept. How come not saying so now?

Here's the background I gave on it. BTW it was to use a PAIR of 004Bs

REGGIANE
Early Italian jet experimentation with indigenous power plants, such as the Caproni-Campini N.1 that used a 900 HP Isotta-Fraschini piston engine and ducts to produce jet thrust, were lackluster but Italy almost had a potent jet. The 1943 Reggaine Re-2007 was to use the Junker Jumo 004B with 1,980 lbs. thrust.

The open exchange of ideas and material between Germany and Italy saw interesting applications in the aviation field such as using Daimler-Benz piston engines on Italian prototypes. When the Jumo was seen as a possible source of power Reggaine laid out a small fighter design. For the time, right before Italy's capitulation, the craft looked quite a lot like contemporary Reggaine piston engine fighters, which makes sense. Even the classic Reggaine tail was present on the horizontally oval-shaped 29.5-foot fuselage. Though the tail was non-swept the wings spanning 31.1 feet did have a slight sweep.
A certain Hauptmann (Captain) Bohm, was the Luftwaffe's senior engineer at the Reggiane plant, but even he was unable to obtain a positive decision concerning the supply of the two Junkers Jumo 004B's which had been promised by the Berlin. On January 7, 1944, Reggaine engineer Roberto Longhi wrote to Count Caproni, requesting that he intervene with the Germans as design work had diminished. Much of the rear fuselage, wing spars, ribs, undercarriage and the cockpit were already built but because of the inability to obtain adequately detailed dimensional specifications about the engine work once again halted.
In October 1944 the finished components were transported to the Caproni plant at Taliedo, where they remained until the end of the war. They were ultimately shipped to the US. The two Jumo 004B engines were sent to Italy, but were allegedly sold for scrap in Milan immediately after the withdrawal of German forces in Italy.

Keeping with the Italian lust for compact planes of high maneuverability the Re-2007 was that weighing just 7,788 lbs. loaded compared to around 14,000 lbs. for the Me 262. Its pair of 004Bs was buried in the fuselage for a very post-war look. The pilot's bubble canopy sat adjacent to the leading edge of the wings.

Maximum speed was estimated to be about 630 MPH while a range of 931 miles was estimated. Four 20 mm MG 151 cannon were to be the armament.

This jet was quite standard in every way and specifications seem legitimate.

 

[Twitch]

I put up a pic of this plane before http://www.ww2aircraft.net/forum/aviation/italian-bombers-3022-4.html?highlight=Re-2007 and cheddar cheese said it was never a design concept. How come not saying so now?

Here's the background I gave on it. BTW it was to use a PAIR of 004Bs

REGGIANE
Early Italian jet experimentation with indigenous power plants, such as the Caproni-Campini N.1 that used a 900 HP Isotta-Fraschini piston engine and ducts to produce jet thrust, were lackluster but Italy almost had a potent jet. The 1943 Reggaine Re-2007 was to use the Junker Jumo 004B with 1,980 lbs. thrust.

The open exchange of ideas and material between Germany and Italy saw interesting applications in the aviation field such as using Daimler-Benz piston engines on Italian prototypes. When the Jumo was seen as a possible source of power Reggaine laid out a small fighter design. For the time, right before Italy's capitulation, the craft looked quite a lot like contemporary Reggaine piston engine fighters, which makes sense. Even the classic Reggaine tail was present on the horizontally oval-shaped 29.5-foot fuselage. Though the tail was non-swept the wings spanning 31.1 feet did have a slight sweep.

A certain Hauptmann (Captain) Bohm, was the Luftwaffe's senior engineer at the Reggiane plant, but even he was unable to obtain a positive decision concerning the supply of the two Junkers Jumo 004B's which had been promised by the Berlin. On January 7, 1944, Reggaine engineer Roberto Longhi wrote to Count Caproni, requesting that he intervene with the Germans as design work had diminished. Much of the rear fuselage, wing spars, ribs, undercarriage and the cockpit were already built but because of the inability to obtain adequately detailed dimensional specifications about the engine work once again halted.

In October 1944 the finished components were transported to the Caproni plant at Taliedo, and stayed there until the end of the war. They were ultimately shipped to the US. The two Jumo 004B engines were sent to Italy, but were allegedly sold for scrap in Milan immediately after the withdrawal of German forces in Italy.

Keeping with the Italian lust for compact planes of high maneuverability the Re-2007 was that weighing just 7,788 lbs. loaded compared to around 14,000 lbs. for the Me 262. Its pair of 004Bs was buried in the fuselage for a very post-war look. This layout was proposed by Yokosuka for the R2Y2 Keiun jet bomber. The pilot's bubble canopy sat adjacent to the leading edge of the wings.

Maximum speed was estimated to be about 630 MPH while a range of 931 miles was estimated. Four 20 mm MG 151 cannon were to be the armament.

 

[delcyros]

Now, let´s assume two Jumo-004 B4would give enough thrust to accelerate the plane to 630 mp/h (I don´t know but let´s believe for the moment):

weight for
two Jumo-004B4 (dry):
3.268 lbs. (1.484 Kg)
additional necessary engine equipment (including lubes, controll and others):
473 lbs. (215 Kg) -extrapolated from He-162 engines (BMW003 is LIGHTER than Jumo 004)
weight 4 MG 151/20:
370 lbs. (168 Kg)
ammo (100 rpg -which is comparably low):
220 lbs. (100 Kg)
fuel for 20 min. full powered flight at low level*:
1.881 lbs. (854.4 Kg)
fuel for engine test, taxiing, take off and accelerating:
462 lbs (210 Kg)
equipment and pilot:
266 lbs. (121 Kg, again taken from He-162)
---------------------------------------------
loadings:
6.942 lbs (3.152 Kg)

loaden weight RE 2007:
7.788 lbs. (3.537 Kg)

TOTAL WEIGHT AIRFRAME RE-2007:
---- 848 lbs. or 385 Kg----
For comparison: airframe weight for He-162A1(originally without structural enforcements): 1836.5 lbs (834 Kg)


I conclude that the airframe strength is insufficiant to carry these loads.
The range with the given loaden weight of the airframe would rather indicate a severe design failure. With two Jumo-004 B I would expect the loaden weight for a twin engined RE-2007 to be at least 10.000 - 12.000 lbs.
The drag factor necessary to achieve 630 mp/h with two Jumo-004 B is ~ 0.82, which is a lot better than anything in it´s timeframe (esspecially for twin engined jets). However, I cannot exclude for sure that such a speed could be achieved with this specific powerplant but I do vote for the variant with higher probability; ~600 mp/h (+-15 mp/h) for a featherweighted, twin jet engined design such as a RE-2007.


*equals 170-210 miles range at 100% and sea level or at best ~500 miles range at 60% and very high altitude (fuel for take off, accelerating and climb to altitude not included)

 

[SM79Sparviero]

According to most of the historical sources Re-2007 was a post-war design ( 1947-1949).
It is quite strange, anyway, that acording to Anthony Kay 's "German jet engines and gas turbine development", pag 85 , ""Italy was interested inusing Jumo 109-004 B to power her first jet fighter, Caproni-Reggiane Re-2007".

It is not strange, on the contrary, that most of historical papers about italian industrial production during the war not only aeronautical but also about armored vehicle is lost, and that industrial leaders , technicians but also workmen frequently deny the existence of a particular industrial project:if you had worked to an aeronautical project during the fascist period in particular during 1943-43 it was commonly interpreted as an ACTIVE COLLABORATION with na nazi-fascist regime. This was sufficient to get a bullet while you were coming home by bike, as happened to Engineer Gobbato who had managed the construction of Db-601 engines on licence in Alfa Romeo.

Here is the letter "riservatissimo-personale"= "personal, top secret" from Eng. Bobbato to Count Caproni , with the request of two jumo engines. If someone wants, I can translate it.

 

[Dogwalker]

The Re.2007 (assuming the existance of the project during the war) was not a twin engined aircraft, but a single engined one, as you can see in the famous post-war cutaway ( http://tanks45.tripod.com/Jets45/Histories/Re2007/Re2007.htm ).
It's projected prestations were greately inflated. In the mid fifties, Sergio Stefanutti's AERFER Sagittario II, had the same weight and prestations of those projected for the Re.2007 (2500 kg, 1050 km/h), but to achieve them, he used a RR Derwent engine, with 1600 kg thrust (179% that of a Jumo 004 B). Wiewing at the very clean line of this aircraft, I don't believe Longhi could do something so better in the forties.

Some of Max Cappone's objections to te existance of the project during the war (as the words of Commander De Prato, or the "impossibility" to use parts of the fuselage of Re.2006 to fit a jet engine) seems specious to me but, at the best, they never hope to wiew one Re.2007 fly first of the end of the war.
The major part, if not all, of the italian's aircraft projects started after 8 september 1943 (not those started first, but not yet ready at the day of the armistice) had, as principal objective of the ingeneers, that of not being deported to Germany and, as principal objective of the owners, that of having something ready for the post-war era. Producing usable aircrafts, was not really an objective. Re.2007 is not an exception.

 

[Twitch]

The problem with neophytes and armchair engineers deciding what performance is or is not possible ascribed to blueprints done by experienced aero designers is worthless. As we all know the process of ANY aircraft reaching combat flight status from an initial design concept is a multi-faceted one. Every plane design is reworked and improved before metal is cut. Flight testing then brings out other modifications desired and prototypes evolve accordingly.

For anyone on forums like these to decide whether a design concept is valid simply is wrong and flawed as the final product will be different. And to pass judgement on preliminary designs from aero engineers with sucessful, proven in combat aircraft experience is sheer folly. We must be aware that basic design concepts and air ministry requirements from any country do not reflect final products.

 

[Dogwalker]

We must be aware that basic design concepts and air ministry requirements from any country do not reflect final products.

That's sure and, surely, Re.2007 (if existant) could be a great aircraft even reaching "only" 900 or 950 km/h instead 1050, or weighting 3000 kg instead 2500. A lot of good aircrafts gained some weight passing from the paper to the production, or achieved prestations that are not the expected ones.

 

[red admiral]

Power = Force * Velocity

Drag ~ constant * Velocity^2

Force = mass * acceleration

At maximum speed there is acceleration so sum of forces = 0

Total Force = 0

(Power / Velocity) - (Constant * Velocity^2) = 0

Power / Velocity = Constant * Velocity^2

Power = Constant * Velocity^3

Power^1/3 * Constant, k = Velocity

The constant value, k varies from aircraft to aircraft and is a measure of how aerodynamic the airframe is.

Me 262, 870kph with 2x900kg 004B engines
k = 870 / 1800^1/3 = 71.5
He 162, 890kph with 1x910kg BMW engine
k = 890 / 910^1/3 = 91.8
For 1050kph with the Re 2007 with 1x004B engine
k = 1050 / 900^1/3 = 108.8

Its not that unreasonable considering the similar size to He162, the incorporation of the engine inside the fuselage and the swept wing. Now if only they'd use the afterburner from the CC.2....

 

[delcyros]

That´s it. I think, despite some arguable points we do all agree that the RE 2007
cannot be a twin engined jet because of weight considerations. A single engined RE 2007 could fit the weights well. It´s performance do remain unknown but the figures are suspicious because of several reasons. Things are not that easy (the rapid drag increase at Mach 0.75 and higher is a serious problem) but the drag difference between Me-262 and He-162 (the latter beeing a lighter but otherwise comparable plane to the RE 2007) is 20.3 according to Red Admiral, while the diference between He-162 and RE 2007 is 17. Such an improvement is suspicious, both planes are ultralightweighted (weight does also play a role, a lightly loaden plane is faster than with heavier loadings), the RE 2007 beeing heavier by 20%! Swept wing may cause a significant drag reduction but do more have an effect on critical Mach numbers (they do not delete drag, they do only shift drag to another speed region). The He-162 already has a very high critical Mach number (thanks to it´s thin airfoils), we don´t know much about the crit Mach figure of the RE 2007. But what else is important for a fighterplane?
Beside of speed it is thrust to weight ratio.
With a single Jumo 004B the RE 2007 as proposed will have a ratio of 0.25. That´s significant lower than any ww2 fighter jets:

Me-262: 0.275
P-80: 0.28
Meteor MK III: 0.28
He-162: 0.3
Bell P 59: 0.44 (with 2 x GE Ia)

Acceleration, climb, take off distance would suffer.
(Only the Ar-234B fully loaden with bombs has a lower thrust to weight ratio)

 

[delcyros]

The problem I see with the drag figures posted are the altitudes. I again checked my books for this. The performance of the Jumo drops in altitude, 890 Kp thrust are at sea level only. The drag also is dependend on air density and Mach fraction. Both are neglected.

I found only one plane to have similar layout, weights and thrust ratios: It never flew. The BV P 211.01 project was a proposal for the Volksjäger competition which in the end was won by the He-162. For a number of weeks the BV P 211.01 was acknowledged as the better plane but it lost in the end.
A comparison with the RE 2007 is enlighting:

Both planes weight around 3.500 Kg
Both planes are driven by a single, low performance jet engine (BMW 003 or Jumo-004)
Both planes have a swept back, low wing configuration.
The BV P 211.01 is 32Kg lighter, has a 90 Kp inferior engine, has 750 Kg fuel and a 30 degrees swept back wing (armament 2 x 30mm MK 108).
Both planes have a long air intake (which results in 6-8% thrust loss according to tests with Jumo-004 B and Me-262 with intake pipes) but only the RE 2007 also has a long exhaust pipe (resulting in additional 5-7% loss in thrust). Odds are that both planes would fare comparably, how is the claculated speed for the BV P 211.01?
Can tell You: 860 Km/h @ 8.000 m. (~540 mp/h). Wind tunnel tests proved that the swept back wing did not made a big difference with the single Jumo-004B powerplant. I cannot imagine how the RE 2007 could reach 600 mp/h. 550 +-15 mp/h is more plausible, 600 mp/h might be achievable with a 1.200 Kp Jumo 004 E powerplant.

 

[DAVIDICUS]

Civettone, I think you may be right. A myth.

 

[Civettone]

I love Italian WW2 aircraft and especially appreciate the Reggiane 200* family.

But the Re 2007 story can be put together with the Ju 390 mission to the US or the 16 Hellcats shot down by a Japanese Ki-100. Great stories that catch and feed our imagination...

One element from the link I quoted stands out: The drawings and technical description were done after the war. The technical description, dated January 7th 1944, is written on Reggiane official paper but it's the type of paper used by Reggiane in the post war years. The drawings were done by Mr. Cometti and, as stated by Mr. Cometti himself, they have done immediately after the end of the war in Europe (May 45).

In any case, it's one thing to draw a jet fighter, it's another thing to actually develop and build one. Longhi didn't have the know-how nor the resources to continue with the Re 2007. Especially the given performance stats (speed, range) combined with the heavy armament and the unnecessary swept-back wing make it clear that Longhi didn't have sufficient knowledge of jet aircraft technology.


Final considerations
1st. If built the RE 2007 could be considered the best jet fighter not only of WWII but also of the late 40s and good enough in the early 50s.
2nd. Having a quick look to the know cross section it's easy to understand that it was impossible to use a RE 2006 frame in order to build the RE 2007. The wing is different, due to the arrowed and sweeped profile, and the fuselage is designed to fit a turbojet engine, quite different from a piston engine. So the opinion that the 2006 second prototype frame was used for the 2007 prototype is a fable written by someone for sure not expert of aeronautical things.
3rd. Com. De Prato says a quite interesting thing about the non existence of RE 2007. In the relatively little Reggiane environment it would been have impossible to hide such an important project and no designer or technician or test pilot remember anything about that. For sure we can exclude that such an operation could be done just by Ing. Longhi all alone.
Kris

 

[bigZ]

From what I have read the Re 2007 was a post war myth that was published in some magazine. If I can remember whereiread this I will copy the the quote and list source.

 

[Parmigiano]

Well, this may put another seal on the topic.

The site is dedicated to Reggiane, and for those who does not understand a word of Italian the summary is: there is NO minimal evidence that something like the RE2007 ever existed, as a prototype or project.

The whole topic is an after-war myth

http://www.geocities.com/CapeCanaveral/Launchpad/2569/RE2007.html