Rolls Royce Viper/ Bristol Siddeley Orpheus

What was the most powerful version of the Viper to see service? Was it the Viper Mk 680-43 rated at 4400 lbs (19,57kN) as used in the MB-339?

Yugoslavia and Roumania also developed the SOKO/IAR Orao featuring 2 afterburning Viper Mk 633-47, featuring 4000lbs ( 17,79kN) dry thrust, and 5000lbs ( 22,24kN) in afterburning.

Was there any move to have an increased dry thrust Viper at any stage? I seem to recall Bill Gunston mentioning a Viper with increased thrust. Did Rolls Royce test any more powerful versions?

Were Yugoslavia and Roumania intending to develope the engines in the Orao any further?

What was the comparison like between the Viper and the Bristol Siddeley Orpheus? The Orpheus was the later engine to run by about 6 years, had more thrust (the Orpeus 803 had 5000lbs thrust).
It had fewer turbine and compressor stages, thus was simpler.
Was there a reason the Viper was in production for a much longer time? What were the specifications for the Viper 680 vs the Orpheus 803?

This might help:


http://www.secretprojects.co.uk/forum/index.php/topic,769.msg98808.html#msg98808


BS seems to have poured intellectual resources into engines of limited return, BS.53/100 and later supersonic Olympus derivatives (which were almost killed before birth in the 50s) to the detriment of more commercially viable engines such as the BS.75, BS.123 and later Viper variants- but then MoS was paying for VSTOL.


See also: http://www.secretprojects.co.uk/forum/index.php?topic=11633.0

Thanks Sealord. I'll have a read through that now.

The Viper and Orpheus originated in different 'stables' and at different times... the Viper aerodynamics came from the Adder which was a turbojet based on the Mamba, so was an engine of 1940's origin. Orpheus was not started until the early 50's and was designed at a higher thrust point which makes it a little larger than the Viper. Viper was a lightweight engine that evolved into primarily a business jet and military trainer engine with other spin off applications. The Viper 600 series engines were a Bristol Siddeley development so incorporated the thinking of Bristol's designers.
The cutaways at the same scale show how the ASV. 3 of 1,640 lbt evolved into the 600 series of 4,000lbt with perhaps an inch extra on diameter. The ASV.3 had 7 st compressor ann combustion chamber and single stage turbine and weighed 375 lb; beefed up for conventional (non target drone) applications the ASV.5 weight went up by 90lb for same thrust.
The 600 series is really a new engine (see cutaways) and is 4,000lbt for a weight of 784 lb in the civil version; 8-stage compressor and 2 stage turbine and a much shorter combustion chamber are features of the redesign.
The Viper ASV.10 is a typical uprated first generation long-life engine.

Thanks Tartle, very interesting.

Kaiserbill... useful to get feedback...
I've now found time to scan in some more of my Viper 'stuff'. The attached pics show the evolution of the Viper 11 into the 600. Inspection of the drawings should reveal how the technology deployed was updated over the years.

The first Viper to run, was a Viper 2, in April 1951, design having commenced in 1948. It was for the Jindivik target drone which was intended to have a 15 min sortie at 40,000ft. It passed a special 10 hr type test later in the year at a rating of 1640 lbt. A modified Viper 3 managed to pass a 150 hr type test in June 1953. As a result the Ministry ordered the Viper 5 for the Jet Provost... the same aerodynamics but strengthened components and a new fuel system, oil system that was self-contained and a remote drive for accessories.
The Orpheus design did not commence until the end of 1953 and came out of a Saturn engine project, 1950-52, intended to be a lightweight engine for the Folland Gnat. In the event the ministry did not support the Saturn and anyway resources were being sucked into the Proteus development programme which was not going smoothly. The Folland lightweight fighter therefore became the Midge and flew with a Viper 5 engine; it went supersonic in November 1954. The Viper programme now concentrated on improving life and performance. Raising the rpm meant increased mass flow and hence thrust. Also component development allowed higher t.e.t. so pushing thrust up. Tweaking the compressor blades allowed better chics (characteristics) and so performance improved again. These modifications in aggregate produced the Viper 8 which had a thrust of 1750lb; type tested in Aug, 1958. By 1962 450 Viper 8 engines accumulated 110,000 hrs running and service lives on critical sub-assemblies were very respectable.. 2,000 hrs on combustion chambers, for instance. Increasing the tet over this period resulted in the Viper 9 variant with a thrust of 1900 lb. More performance could only be achieved on the existing engine by reducing service life so thoughts turned to a redesign.
The Viper 10 was run, with much improved aerodynamics and improved construction. This engine delivered 2,000 lbt in Dec, 1956. An uprated version the Viper 11 delivered 2,500 lbt.
As a private venture Bristol looked at future civil/military applications and decided there was a market for a an engine of 3,000 lbt with scope to be grown for future aircraft versions. This led to the development of the Viper 20 (mil) /520 (civil), which had a transonic zero stage on compressor, raising mass flow by 20% and also increasing pressure ratio. The tet was reduced by 30 deg to 1070 deg K. to enable growth potential and greater civil service life. (In material terms a change in metal temperature on the turbine blades of 10 degC approx will halve or double creep life).
The Viper 600 was the ultimate development of this very successful engine. The Italian MB 339 had the ultimate version .. the Viper 680 that had a thrust of 4,300 lb.
... so on to the Orpheus........ which finally ended up as part of the Pegasus!

That is fantastic feedback indeed, Tartle.

Very much appreciated. The Orpheus powered the Gnat/Ajeet, Fuji trainer and the Fiat G91. Not a bad total I suppose, but not nearly the production run enjoyed by the Viper.

Onto the Orpheus.. I am writing about a 1909 engine so I will do this with a tbc note on it if I break off!
The Orpheus originated from project work in Bristol's design office on the Saturn. Saturn started off as an idea for a lightweight expendable engine for a stand-off bomb or guided missile. The thinking at that time was that a subsonic speed coupled with very high altitude and reasonable range would 'do the job'. Scheming on the first configurations, known as the B.E.17, started in 1950 and was supported by a Ministry contract. The project was led by Frank Owner in design and Fred Whitehead in production. They led the team to investigate ways of creating a very light low life engine (Rolls-Royce were doing similar with the RB 82) . It was essential that manufacturing were involved from the start as lightweight engines are designed to benefit from non-conventional approaches to the fabrication of the necessary structures. The project ended with the creation of a brochure that detailed the engine layout and manufacturing methods to be used to help achieve light structures and details of the factory necessary to produce them economically. At this point the project ceased and the B.E.17 - a 3,000lbt, 500 lb weight and £500 cost (if produced in batches of thousands!) was never produced as hardware.
Meanwhile Folland had started a design investigation, under the leadership of William Petter, their new boss (he had moved from English Electric after acting as chief designer for the Canberra and P.1) into a lightweight fighter... he talked with Bristol who suggested a more robust version of the B. E. 17 would philosophically be a match for his Gnat ambitions. January 1952 saw Bristol start the design of the B.E.22 for the Gnat. Both firms starting their projects as private ventures. The lighter than conventional engine design was named Saturn and was designed to deliver 3,750 lbt for a weight with accessories of 730 lb. The single shaft engine cofiguration was:
8-stage axial compressor, cannular combustion chamber, 2-stage turbine.
At the end of 1952, the Ministry of Supply said it could not support either project and with Bristol's full committment to the challenges of the Proteus meant Saturn was shelved.
As we saw previously, the Gnat became a Midge and the Viper took Saturn's place.
As yet I have not found a scheme or other drawing of Saturn.

But all was not lost....
The end of 1953 saw a NATO Ground Support competition NMBR-1 begin; Saturn was revived to serve as a powerplant in the British entrants to the competition. This is a list of entrants:

France Breguet Br.1001 Taon
France Dassault Etandard XXVI
Italy FIAT G.91
France SIPA S.800
UK Avro 727
UK Folland F.O.41 Gnat

Since the Saturn had not progressed beyond the initial design phase Bristol's design team, under Stanley Hooker's leadership, decided to speed the process up, and keep costs lower, by redesigning the engine to use the existing low pressure compressor system of the Orion turboprop. and the engine was renamed Orpheus. The Orpheus 1 made it to the test beds and first ran on 17th Dec 1954, at a thrust of 3,000 lb and completed its 150 hr type test in May 1955 at 3,285 lbt.

The Orpheus became a recipient of funding under the Mutual Weapons Development Programme agreement that involved the Gnat (1st flew 18th July 1955), Etandard VI (1st flew March 1957), Fiat G91 (1st flew Aug 1956) and the Taon (1st flew July 1957). The Orpheus powered all these aircraft. The Gnat was modified to accommodate the larger diameter tailpipe, dictated by the switch from Saturn.
The Taon turned out to be a fast aircraft; powered by an Orpheus 3, it twice set up a 1,000km closed circuit record... the second occasion, July 23rd 1958, was at an average of 608 mph at 20,000 ft.
The development of the Orpheus financed by the Americans as the only suitable engine available for the Programme proceeded apace; The BOr1 was type tested in Jan 1956 at 4050 lbt. Development of the Orpheus soon resulted in the BOr2 type tested at 4250 lbt in Nov 1956. Fitted with a larger accessory wheelcase it went into production as the BOr3 or Mk801 after passing a type test at 4850lbt in May 1957, primarily for the G91, which won the NATO competition. For trainer use the engine was derated by reducing tet and rpm to yield the 4230 lbt BOr4.
The 801 was uprated to 5,000 lbt and as the 803 passed type test in February 1959. The Mk 803 was made at Bristol and also by Fiat and KHD.
Talks with the Indians had resulted in the selection of the Gnat for the IAF, to be manufactured in India at a new factory in Bangalore. So Hindustan Aircraft Limited came into being, where the Orpheus was produced and overhauled under licence, signed 15th Sept 1956. The first engine came off the production line in Nov 1960, the first Indian Gnats were powered by Bristol-built engines which entered service in Jan 1958. Later the engine also powered the HAL HF 24 Marut fighter.
Originally the Marut was to have an afterburning version of the Orpheus 12. This engine was a major uprated version with an extra transonic zero-stage to increase mass flow. The turbine became a 2-stage design. The design rating was 6810 lbt and this was achieved in a simulated type test in March 1959. A year later the official tt was achieved. With full reheat the engine achieved 8650 lbt and a simplified reheat gave 8170 lbt.
The Marut did not proceed with this aprated engine and Nato uprated aircraft also did not proceed with th Orpheus 12 engine.

The Orpheus engine was selected to power the prototype Lockheed Jetstar as suitable American engines were not available. The picture shows the first prototype fitted with two 4,850 lb (2,200 KG) s.t Bristol Orpheus 1/5 turbojets. It first flew September 4, 1957. The production aircraft were fitted with four 3,000 lb (1,361 kg) s.t Pratt & Whitney JT12A-6 turbojets. This was because of engine out performance requirements.
Other highlights of the Orpheus development programme are shown on a graph published in Flight 13 Feb 1959.

In 1956, a French aircraft designer named Michel Wibault, well-known for his pre-WW II designs, proposed a VTOL aircraft named the "Gyroptere". He was interested in building a combat aircraft that would be able to operate independently of airfields, which were clearly vulnerable to immediate destruction by Soviet nuclear strikes on the event of a general European war.
The Gyroptere was to be fitted with a British Bristol "BE.25 Orion" turboshaft engine, with 8,000 horsepower, fitted the rear fuselage to drive four blower units, two on each side of the aircraft and arranged around the center of gravity. Each blower would be in a moveable snail-shaped casing that could be rotated to provide vertical or horizontal thrust.
Wibault tried to promote the Gyroptere with both the French and American air forces and got nowhere. Finally, he approached the Paris-based "Mutual Weapons Development Program (MWDP)", an American-funded NATO office that promoted technologies useful for European defense. The MWDP's chief, US Air Force Colonel John Driscoll, found the concept interesting, and passed it back to the NATO "Advisory Group For Aeronautical Research & Development (AGARD)" for comment.
AGARD's chairman was Theodore von Karman of the California Institute of Technology, and one of the most prestigious figures in aerospace. Von Karman was very intrigued by the idea. Encouraged, Colonel Driscoll then passed the concept on to Bristol Aero Engines back in the UK.
Bristol's technical director, Sir Stanley Hooker, found Wibault's lash-up clumsy and inefficient, but he liked the basic idea of using a single engine for both vertical lift and forward flight. Other VTOL experiments at the time had separate sets of engines for the two purposes. Hooker assigned a small research team consisting of Gordon Lewis, Pierre Young, and Neville Quinn to investigate the idea.
The research team quickly concluded that Wibault's idea could be greatly improved by using the using the airflow of the engine itself, directed through swivelling exhausts, instead of a set of external blowers. They then gradually refined the idea
Their first design concept, designated the "BE.48", was described to Hooker in a memo dated 2 August 1956. The BE.48 simply extended the Orion's shaft forward to drive a large compressor turbine at the front of the engine, something like that of a modern high-bypass turbofan engine, to drive airflow through a pair of elbow-joint swivelling exhausts immediately behind that.
The memo suggested that the first two compressor stages of the Olympus BO1.21 could be used for the forward fan. The turboshaft's rear exhaust remained unchanged, with the airflow straight out the back.

This concept was quickly changed to the "BE.52", in which the Orion was replaced by a modified version of the smaller and simpler "Orpheus" engine, and the large compressor fan was more tightly integrated with the rest of the engine. The scheme provided just as much thrust, maybe even a little more, than the Orion-based concept. Versions with straight or swiveling exhausts fitted to the rear of the engine were considered.

The next concept, the "BE.53", was similar, but the large compressor fan was changed so that it rotated in the opposite direction from the main compressor spool, eliminating gyroscopic effects that could be a nuisance in a VTOL aircraft. The BE.53 was described in the initial patent for the new type of engine, dated 12 January 1957. The GB patent 881663 was applied for by Michel Wibault and Gordon Lewis on January 29th 1957,. It was published on 8th Nov 1961....tbc

At this stage Bristol had an engine but no aircraft to put it in! Stanley Hooker went to Paris to show the BE.53 concept to Driscoll and von Karman, who were both enthusiastic. Driscoll left the MWDP soon after Hooker's visit, but his successor, USAF Colonel Willis "Bill" Chapman, was just as enthusiastic.... but still no application was apparent.
In early 1957, Hawker Aircraft's chief designer, Sir Sydney Camm was attending the Paris Air Show. There, he chatted with the Hawker representative in France, Gerry Morel,Camm mentioned that he was unimpressed with most of the "lift-engine" VTOL schemes being put forward at the time, and Morel told him about Hooker and Bristol's schemes. As Camm was concerned about Hawker's future, Camm reasoned, a VTOL combat aircraft might stimulate their interest.
A few days later, Bristol's Hooker got a letter from Camm that read: -- and a few days later Camm got back an envelope containing the BE.53 technical brochure. He passed it on to his engineering staff, and in due time got back a preliminary sketch of a VTOL aircraft. Some time later, in early March 1957, Camm then gave Hooker a call who reported that the conversation went: "When the devil are you coming to see me?" Camm said.
"As soon as you like of course. But what is the subject?" Hooker replied.
"It's vertical take off! I've got an aircraft for your BE.53!"

Hooker and members of his team turned up in Kingston the next day, where Camm showed them the first drawings of the P.1127.
So 1958 saw the start of the detail design of the BE.53 and P.1127 supported by a 75% funding agreement with MWDP. The respective boards of Bristol and Hawker Sideley agreed, in the absence of Ministry interest, to fund the other 25%.
Hooker has described how they basically took an Orpheus and put a shaft through the engine to link the two stage lp compressor with the two-stage lp turbine.
Camm remeberd the Sea Hawk bifurcated exhaust and realised if the engine had this instead of nozzles at the end of the jetpipe then all thrust would be as close to the aircraft's CoG as practicable and so the configuration was born that we recognise today.
The engine was sized to give around 11,000lbt and it was thought a commercial version with conventional exhausts would be interesting... thus the BE.58 was born... it turned out to sit just where RR P&W etc had engines already under development so there were no potential customers for it and it died.
As more power was required for the P.1127 as it was detail designed and weight estimates crept up., Hooker went for a zero-stage on the lp compressor... to make it easier to fit he designed it as an overhanging transonic fan with no inlet guide vanes, which eliminated the need for anti-icing of the vanes, so increasing air through the engine with consequent thrust and/or tet benefits. Also the rotation of lp compressor was reversed to reduce gyroscopic effects on the aircraft. The overhanging fan is common on all fan engines today.
The MWDP liked what they saw and so the Pegasus powered Kestrel was borne. [I have attached a low-res scan of my cutaway as it shows the overhung fan more clearly than Flightglobal's cutaway -also attached]

Excellent Tartle!

That Orpheus 12 sounds interesting.

About Michel Wibault and the Gyropter, you can have a look here, too :
http://www.secretprojects.co.uk/forum/index.php/topic,2118.msg118929.html#msg118929

kaiserbill,
The Orpheus 12 and its reheat version sound fascinating... I know where there is more data but I am engaged on writing material for Maurice Egerton's 1909-1914 aeroplanes mainly with a Gnome rotary engine to be used in an exhibition from 24th March to end April at Tatton Park's mansion... then I'll devil the data to complete the Orpheus story.
Jemiba,
Thanks for thread... Wibault died before the BE.53 ran and Kestrel flew .. so he never saw what a great aircraft he inspired... even if it was a mile away from his sketches, but I wonder what he would have made of this?
In summary the design iterations that Wibault was involved with after Bristol picked up the idea and ran with it are (hopefully this ties in with what I have already written!):
The BE48 replaced the centrifugal compressors with the axial Olympus l.p. compressor, using it as a fan;
The BE52 replaced the Orion and its gearbox with the Orpheus, but retained the separate intakes for the core engine;
The BE53 did away with the separate intake and used the fan to supercharge the core, giving more power;
The BE53/2, the first Pegasus, introduced contra-rotation and confirmed the use of four nozzles rather than three.

sealordlawrence... you suggested we compare a Viper and an Orpheus... well here goes


Engine mark Viper 600 Orpheus 803

configuration single-stage single-stage
compressor stages 8 7
combustor annular cannular- 7 tubes
turbine two-stage single-stage
T/O thrust lbt 3,750 5,000
Air mass flow lb/sec 58.4 84
Pressure ratio 5.8:1 4.14:1
length in 85.0 96.1
diam in 24.5 32.4
weight lb 790 975
t/w 4.75 5.13

It is not easy to deduce which engine had the earlier birth as redesign and incorporation of new technologies has proceeded apace on both engines. Also the duty is different so optimisation happens around different parameter points. However, as always, t/w ratio is an indicator. The most fundemental difference between the configurations is the bearing arrangement: 3 bearing arrangement on the Viper but only 2 on the Orpheus. This was really the first engine in Stanley Hooker's career that presented him with a clean sheet of paper... so he decided on a two-bearing arrangement as a way to achieve lower weight and then designed other components to achieve a stiff enough rotor assembly to avoid resonance issues. He obviously succeeded!

Viper engine production ended in 1996, but refurbished engines were being supplied as recently as 2009 for newly-built Macchi MB-339CD trainers for the Malaysian Air Force. Production in Britain by what were successively Armstrong Siddeley, Bristol Siddeley and Rolls-Royce exceeded 5,600.

In 2008 Flight ran a 100 greatest forum and the Viper was proposed for the list. I reproduce one of the comments received here:
"
It was with some interest that I read your comment about the Rolls Royce Viper engine, which was designed and initially developed by Armstrong-Siddeley Aircraft Gas Turbines, of Parkside Coventry.
As a young graduate engineer in the design and evelopment department of Armstrong-Siddeley's from 1949 to 1951 I had been engaged in the development of the Armstrong-Siddeley Mamba turbo-jet and its sister engine the Armstrong-Siddeley Adder pure-jet engine. Both of those were excellent engines with a small frontal area profile and individual combustion cans. However they both suffered to some extent from problems of matching the turbines to the axial compressors.
The Viper was a new design to a Ministry specification for an expendable jet engine to power the Jindivik target towing aircraft being developed for use at the target range at Woomera in Australia. Having had the experience of working on the Adder, it fell to me to arrange and carry out the very first-ever test on the first prototype Viper, which, if I can recall correctly was in April 1951. John Marlow was the Chief Development Engineer and he was present during that test. The main functions initially being recorded were thrust and fuel consumption. After going through the preliminary run-up procedures, we put some power on to the engine and on calculating the specific fuel consumption, Johnnie Marlow thought I'd got something wrong, so would I do it again. I repeated the calculations with Johnnie looking over my shoulder and, agreeing with what I did, He was totally astounded at the result and performance and was immediately and joyously telling all around that at last Siddeley's had matched a turbine and a compressor.
The prototype was quite remarkable. The first few rows of the axial compressor had plastic blades, the oil pumps for the shaft bearings were simple plunger pumps which were bought from the local motor cycle makers. However, part of the real success was annular combustion chamber with its inherent simplicity. Siddeley's had already had extensive experience of annular combustion chambers with their Sapphire engine, which in fact was used by the US Army to power their fleet of Canberra bombers which they built under licence, although I believe that the original annular combustion chambers were inherited from Metrovickers whose designs had been sold to Rover cars before being transferred to Siddeley's.
Eventually Siddeley's were merged with Bristol Engines to form Bristol Siddeley, which eventually was absorbed by Rolls Royce who continued and advanced the Viper design to what is indeed the longest production aircraft engine in the business. I believe it is from that merger that most Rolls engines have the pre-fix RB.
Shortly after running the Viper test, I left Coventry to take up an academic lecturing post in Aberdeen, where I eventually became Associate Head of the School of Mechanical and Offshore Engineering in what is now the Robert Gordon University. But I look back on those days at Parkside and the testing bays at Ansty with fond memories and some pride.

Regards,
Bert Hosie, BSc,CEng, FIMechE, Fellow of RGU, Inverurie, Aberdeenshire."

Tartle, thank you very much for the very informative replies.

Extremely interesting.

One wonders why the Orpheus, particularly the Orpheus 12, never found an application. The Fiat G91 seems to have been a tailor made platform, particularly when one considers that it eventually ended up with 2 re-heated turbojets. Probably a time scale issue?

kaiserbill... it is interesting that the thrust of 2 J-85 = Orpheus 12... I wonder if the reason to switch was that newer rival aircraft had two engines and a reason for that was greater chance of surviving battle damage in a close support role? Also America might give more political support to Italy's foreign sales if at least the USA got the engine orders?

tartle said:

kaiserbill... it is interesting that the thrust of 2 J-85 = Orpheus 12... I wonder if the reason to switch was that newer rival aircraft had two engines and a reason for that was greater chance of surviving battle damage in a close support role? Also America might give more political support to Italy's foreign sales if at least the USA got the engine orders?

Click to expand...

Would also have been an obvious candidate for the later Gnat variants but that design moved towards RR RB153's, supposedly because of delays in the Orpheus programme.

tartle said:

kaiserbill... it is interesting that the thrust of 2 J-85 = Orpheus 12... I wonder if the reason to switch was that newer rival aircraft had two engines and a reason for that was greater chance of surviving battle damage in a close support role? Also America might give more political support to Italy's foreign sales if at least the USA got the engine orders?

Click to expand...

Indeed, the J-85 powered G-91Y was what I had in mind.
And the US connection to the G-91, particularly the initial US funding, is what crossed my mind too re afterburning engine choice.

Interestingly, I seem to recall Northrop entered their N-156 into the original competition that was won subsequently by the G-91.
So, full circle engine wise, perhaps?

The Orpheus 12R version of the 703 engine was offered to NATO for the upgrades of their European fighters and was rejected. However the Indian Gas Turbine Research Establishment in Bangalore worked presumably in cooperation with Bristol to develop over the period 1959-61:
-Design and development of a "1700K reheat system" for the Orpheus 703 engine to boost its power. The redesigned system was certified in 1973.
-Successful upgrade of the reheat system of the Orpheus 703 to 2000K.
-Improvement of the Orpheus 703 engine by replacing "the front subsonic compressor stage" with a "transonic compressor stage" to increase the "basic dry thrust " of the engine.

The last item looks like the civil upratings at Bristol so one wonders who developed what especially in light of the subsequent slow development of an Indian 'indigenous' engine.

There is a 703 in the Deutches Museum in Munich according to a Flickr photoposter
His photo is below [ a very high res is on his Flickr site]:

On a consortium of Indian Websites I found this intriguing comment:
"HF 24, an aerodynamically clean aircraft, capable of super sonic performance, was designed around an engine yet to be developed. Bristol Siddeley offered the BOR 12, a reheat variant of the Orpheus 703 as a power plant for HF 24 to us, as well as the NATO countries. When the NATO countries rejected the offer, Bristol Siddeley proposed its development at a cost of Rs 5 crores to Krishna Menon then Defence Minister who rejected it. It was a fatal error of judgment- in that HF24 never achieved its design performance. Its development violated a basic principle in aircraft design during those days: Proven engine and a new airframe. Never a new engine and a new airframe." ref

It seems that plenty of Defence Ministries, then as now, learn the lessons. As someone said it wasn't Deja Vu but Vu Deja.. you enter a familiar situation and treat it as though you've never been there before!

Had forgotten about the Marut, Tartle.

I remember now that it's performance was limited by it's engines, and that expected engine developments ensured that its performance remained pedestrian to what was initially envisaged and designed by Kurt Tank. It was designed as an aircraft with speeds of around Mach 2.

The Marut story has been told here. The relevant bit to our engine rambles is:
Continued Development
With the completion of Kurt Tank's tenure in 1967, responsibility for Marut development had passed to S.C. Das and an all-Indian team which produced the Mk.1T tandem two-seat trainer. The two prototypes of the trainer (BD 888 and 889) were the 46th and 47th Marut airframes, and the first of these was flown on 30 April 1970 by the then chief test pilot, Wg. Cdr. R.D. Sahni.
The essential difference between the single and two-seat versions of the Marut was the removal of the MATRA rocket pack featured in the former to provide space for the second cockpit. The minimal airframe changes required for the Mk.1T resulted in low development costs and almost total spares interchangeability. The second prototype Mk.1T was flown in March 1971, and the first of these entered squadron service in early 1975.
The search for a suitable engine continued even after the Maruts went full ops. In September 1966, the MoD announced that flight testing had begun on the third pre-production aircraft (as HF-005) designated Mk.1A with an afterburning Orpheus 703 with an 18% greater boost than the original at 5,720 lb. (2 595 kg). By 1970, two more Maruts, designated Mk.1R, were brought into the afterburner development trials. Unfortunately, the programme suffered a severe setback when, on 10 January 1970, the first of two Mk.1R prototypes (HF-032) being flown by Gp. Cpt. Suranjan Das crashed just after take-off.
India's foremost test pilot was the unfortunate victim of this crash. At the time it was rumored that one of the engines had completely failed and that there may have been a partial failure of the second engine. However, the official inquiry attributed the accident to malfunction of the canopy locking system. The Mk.1R prototype had been fitted with a hinged clamshell-type canopy in place of the earlier sliding canopy, and the failure of the locks and the sudden opening of the canopy, resulting in rapid decay of speed at a critical stage, proved fatal.
This set the programme so back, that the final stages of the flight test programme, using the second Mk.1R (BD 884), were achieved only in 1973. This airframe had a modified wider aft fuselage. The Orpheus 703 afterburning system had progressed to provide a 27% boost, giving 6160 lbs. (2 794 kg) of thrust, but the performance increment that it provided the Marut was insufficient to result in a production order for the Mk 1R. By the late 1970s, HAL entered into discussion with Rolls-Royce about using the Turbomeca Adour twin-spool after burning turbofan to power the Marut. The projected Adour-powered fighter was designated as the Marut Mk 2.
The Rolls-Royce RB.153 was considered for a while, but Hindustan Aeronautics was neither able to accept the terms of the proposed contract nor, at the time, was ready to consider the major redesign of the fuselage that adoption of the RB.153 would have entailed. In the event that by the early 1980s, the Air Staff requirements for a TASA (Tactical Attack and Strike Aircraft) and a DPSA (Deep Penetration and Strike Aircraft) were fulfilled by foreign aircraft, the need for a upgraded Maruts became somewhat superfluous. And by the mid-1980s enough Jaguars and MiG-23BN/27s were joining the IAF, that the Marut programme no longer remained viable.
No.10 Squadron gave up its Maruts in August 1980 and by the following year enough MiG-23BNs were available to allow No.220 Squadron to begin conversion. The last unit to give up its Maruts was No.31 Sqn, whose aircraft were finally withdrawn in mid-1990. And so ended the saga of India's first, and until the LCA flies, India's only home- grown fighter programme. In retrospect, despite its audacity, the Marut progamme helped lay the infrastructure for an Indian aviation industry.


A pilot commented:
The Marut was the brain child of Dr.Kurt Tank a German designer, who had been hired by the Indian Government to design a Mach 2 fighter bomber.
The Marut was a versatile fighter bomber, but it was underpowered and thus achieved speeds of Mach 1.1 at the maximum. But in two wars with Pakistan not a single Marut was lost in air combat. The Marut was twin engined and seated a crew of two.No 10 squadron was equipped with the Marut. Many attempts were made to get a more powerful power plant for the Marut, including an Egyptian engine. But they were not a success and the Western powers were reluctent to give a power plant. But despite these limitations the Marut gave excellent service to the IAF
Pilot_micha's photostream on Flickr photographed the Marut and also the Spanish Ha 300, which also used the Orpheus 703. I append 2 below but there are more pics available

A question on the Orpheus 101:
I remember as an apprentice, in 1972, measuring some 2nd stage compressor stator tip clearances from superX? linac? pictures for the full running range (used a microdensitometer).
This was in connection with some compressor failures.
Does anyone have any recollection on what planes would likely have prompted the investigation?
eg say 3 accidents in 1971.

That Orpheus 12 with afterburning actually sounds like quite a missed opportunity.

I can actually think of quite a few aircraft that may have benefitted from an engine in that class.

Any idea what it's physical dimensions were?

I don't have the dimensions to hand for the BOr12 but this might help:
The Aerfer Leone was being built with a BOr12 engine; it had a wingspan of 6.93m; length 10.6m; height 3.32m.
The cross-section below has the engine shown so we ought to be able to scale it!

kaiserbill said:

That Orpheus 12 with afterburning actually sounds like quite a missed opportunity.

I can actually think of quite a few aircraft that may have benefitted from an engine in that class.

Any idea what it's physical dimensions were?

Click to expand...

It certainly would have been an interesting engine, as would a militarised supersonic version of the BS.75, in particular the various proposed Gnat derivatives could have benefited: http://www.secretprojects.co.uk/forum/index.php/topic,769.msg98808.html#msg98808

The BS 75 diameter was 34.4 vs 32.4 inches for Orpheus 3 or 4; length 89 vs 75.5 or 77.5 for Orpheus 3 or 4.

On some research unrelated to the Pegasus jet engine (about the wartime development of Merlin) I have been reading 'Sydney Camm and the Hurricane' which has a chapter or two on later developments after piston engines. There is some interesting 'stuff' on early P1127 design development and below is a page with some GA's of what the aircraft looked like before they trousered the hot exhaust!

Just stumbled across the thread. Thanks a lot Tartle for the very informative posts about the Viper and Orpheus.

kaiserbill said:

That Orpheus 12 with afterburning actually sounds like quite a missed opportunity. ... Any idea what it's physical dimensions were?

Click to expand...

I know kaiserbill's request was a long time ago, but Flight did publish the Orpheus 12's dimensions ...

Bristol Siddeley Orpheus BOr.12 Single-shaft turbojet. Multi-stage compressor, can-annular combustion chamber and single-stage turbine. Overall diameter, 32.4 in; length, 98.325 in; dry weight, 1,100 lb: max rating. 6,810 lb dry. The BO.12SR gives 8,170 lb thrust with simple reheat.

Orpheus BOr.3 Mk 803 (not illustrated). Overall diameter, 32 4 in; length, 7S.45 in; weight, 825 lb; max rating, 5,000 lb at 10,000 r.p.m. (s.f.c., 1.06); max mass flow and pressure ratio, 84tb/sec and 4.4:1.

The BOr.12SR has a reheat system of a special simplified pattern, intended principally to provide increased thrust for operations from poor airfields. Aircraft designed to use it are in various stages of development in France, India and Spain. There is also a non-reheat commercial variant, fitted with a two-position nozzle which in the closed position permits the take-off rating to be raised to 7,200 lb and at full area lowers the cruising consumption. Weight would be some 1,220 lb with full airline equipment.

Click to expand...

Flight 18 March 1960, page 369
https://www.flightglobal.com/FlightPDFArchive/1960/1960%20-%200369.PDF

Thanks Apophenia!