The AMCA – a review 2022/4                                                                                               Prof. Prodyut Das

Introduction

If the way the DRDO is going about the development of the Flight Refueller program is not a flash in the pan then it is cause for cautious optimism. By utilizing Covid surplus airframes and hiring consultants where required DRDO is displaying precisely the “mend and make do” enterprise that is needed for successful programmes. It is unfortunate that ADA, another DRDO organization, has consistently lacked the same kind of spirit. This does not augur well for the AMCA programme.

Given the closer Government monitoring and the fact that the Customer has been taken on board means that there will not be any of the major blunders that was seen in the Tejas programme-blunders that required long and painful correction and even now the product is not “production worthy”. This is a sharp contrast to its later contemporary, the ALH programme which is now well set to be the most produced aircraft of Indian Design in our Aviation History. Indeed, and one says this with considerable chagrin, ADA efforts over forty years has only ensured that the Combat aircraft market in India remains firmly with the import lobby! The number of imports, proposed and continuing, twenty-two years after first flight of the Tejas, is witness to this unpalatable truth. The genesis of ADA was from a spate of Departmental Rivalries in the ‘80s.  It is not Tejas so much as ADA that requires care and attention. Indeed, the question that needs discussion is whether ADA should become a PSU, be restructured like OFB or privatized like Air India.

 As things stand closer monitoring will ensure that the 2025 dateline for first flight will probably not seriously overrun. Whether the programme will meet its technical objectives is something that cannot be sanguinely confirmed. That or the extent of “correction” needed will only be clear when the prototype starts to fly. Of course, by then, it will be too late to avoid significant delays if things need serious mending.

This misgiving is from the fact that even by the scant evidence available and despite ADA’s assurances it seems ADA has not learnt its fundamental lessons. Despite the Tejas experience ADA is once again going to use new technologies critical to the AMCA that it has not yet fully mastered to the stage of confident incorporation in a design- stealth, DSI intakes, and the design of the weapons release system in the stealth mode. to name but a few. Mending mistakes on the prototype, labelled as “Technology Demonstrators” -is – as currently seen in the Tejas-going to be time consuming.  

The other question is that the IAF DCAS Plans has issued a very challenging specification. The specifications are very good but may end up in delays precisely because of the overreach; there may be much cheaper and quicker ways of doing the job.

We are set to repeat history because we do not have a parallel alternate insurance AMCA programme to run until the proposed AMCA takes off and initial flight trials show sufficient promise and reassurance which optimistically should be round 2025. Insurance programmes e.g., the YF 23 to the F 22 and the Boeing YF 31 to the XF 35 is the standard procedure for getting hardware on time for those who mean business about development. The Indian Aerospace design man power, a total of some 4200 according to official figures, is there and all of it cannot be needed for the AMCA programme. Over this is the resources of the Private Sector. If all of it is indeed needed it would indicate inefficiencies and a good project team need not be more than perhaps thirty people. 

The marginal cost of the second alternative development is not much; it is either closed down after a few years-when expenditures are not high-the AMCA itself used tranches of 10 plus 90 crores over a seven-year period and efficient management can slash that figure too- or the funds from the original programme is available for use in case of shut down of the original project. 

Timelines of the AMCA

The AMCA program’s details are available on the Net and the following is a brief summary.

The project studies were started in 2007 with a funding of 10 crores and the ASR was issued in 2010. Further funding of 90 crores was given in 2009. The Project definition phase PDP was completed in 2013 though it is not very clear how many alternatives layouts were examined during this six- year period. It should have run into several tens but no details are known except that a finless design was at one time examined which was, perhaps mercifully, not proceeded with it being as ugly as sin.

 The layout finally chosen -a shoulder mounted rhomboidal wing design with a “chined” fuselage, twin engines with a matching rhomboidal tail and twin fins has a general resemblance to this genre of aircraft e.g., the Raptor/ FC 31. The final configuration selected was refined through studies 3B01 to 3B09 between November 2013 to December 2014 but these studies were related not to the checking out of area ruling, weapons bay details and similar detail design work rather than examining radical alternatives which should have been done. It was finally round 2019 that the AMCA began to emerge as a reasonably competent looking aircraft.

I will mention that the corresponding “delays” for the equivalent programme of the US i.e., the ATF programme ran like this: One year (September 1985 to September 1986) for Request for Information from six companies, funding for two prototypes from the winning project and the insurance project in 1986 and first flight of both competing types within five years from RFI. It is clear that the Government is too slow a mover to succeed in the Aerospace Business. The biggest resistance to our development is in the warrens of Raisina Hill! We have to move faster.

Funding

Circa 2018 i. e. eleven years as compared to one year as above after the start of project studies the design was approved for Detailed Design Phase (DDP) with a funding of Rs. 400 crores in 2018/2019. This kind of delay makes one seriously wonder if there is a clerk in North Block whose sole duty is to make projects obsolete before they are even approved. Having funded project studies in 2008 the DDP should have been funded by 2010 at the very latest- or the project studies should not have been funded at all. The aircraft cleared its customer design review CDR in November 2021. One presumes that the view of the reviewers was respected unlike last time when reportedly the then Chairman evidently bypassed the objections by declaring the unsatisfactory design as a “Technology Demonstrator”- a administratively “clever” move - but a fatal misstep that has been responsible for the subsequent delays.  

A funding of 15,000 crores with an aim to produce 7 squadrons worth of AMCAs has been released, 2 squadrons with the F 414 and 5 with a yet to be developed homegrown engine of 121 kNs each. This engine will give the aircraft super cruise capability and is to be developed with collaboration of the French.

Technical Features

The aircraft proposed by ADA is similar in concept to aircraft developed by China and the USA. The AMCA has fifth generation features and is to be used as an air supremacy, strike, SEAD, EW roles and is viewed as a replacement for the SU30MKI. The later versions will be having sixth generation features. One caution is that brilliant specification features on paper is as wonderful and useful as the license for a gun when there be tigers about.

Some of the features of the AMCA are: Stealth, 3D thrust vectoring, AESA radar, OBOGS, Internal weapons bays with the capability to house to two missiles and two (presumably) SDRAMs, AESA radar, DSI air intakes with low RCS “snake” engine inlet trunking and the latest trends in a Glass cockpit with all the usual concepts in terms of displays-MFDs, touch screens, voice inputs sensor fusion coupled to MAWS, EW suite etc.

Structurally the aircraft uses a greater degree of composites reflecting a greater confidence in the use of the new material. It is to note that the front fuselage from the intake lip to the wing attachment points extensively use composites and even the fuselage formers in this region are composites- possibly to increase stealth in the frontal lobe. An interesting feature is the intake ducts are labelled “stressed”. Whether the duct is stressed to withstand the routine ram pressure recovery or for giving rigidity is not known. If for structural reasons it will make the structure quite rigid- two skins with supporting webs makes for a rigid “box” but why this is needed is not known. Obviously, the weight penalty associated with a” structural” duct has been considered and found acceptable. The centre fuselage wisely stays away from too much composites particularly for the areas of point loads- wing and undercarriage and I presume air brake attachments. The use of metals and steels in this area is mentioned. Titanium is used in the region of the engines.

Weight and CG control or more correctly the utter lack of it was the hubris and nemesis of the Tejas. Guarding against this will apply equally to the AMCA. The empty weight is given as 12000 kgs. My estimates indicate that the airframe weight has to be held within 4500kgs if the project is to succeed. If we add another 3000kgs for the two engines and its fuel systems and perhaps 700 kilos for the U/C the team has about 3200 kilos for all the rest of the systems- hydraulics, avionics. Seat and safety etc. Not a lot but care and diligence will pay off.

Air Marshal Nambiar mentioned in a recent Blue Skies Podcast that there was a shortage of fuel tankage in the Tejas. This is somewhat surprising because one of the few advantages of the Plain Delta is fuel volume availability. The Tejas prototype I had the good fortune to examine in 1996 somewhat surprisingly did not use wet wings and  the AMCA details as released also shows no wing tankages. The AMCA fuel is carried in a series of relatively thin (about 300mm) rectangular tanks running along the length of the centre fuselage arranged around the inlet trunking. By my estimates the AMCA will be able to carry about 5600 kilos of fuel as against 6500 kilos declared by ADA but a lot depends on the type of the tank used. In any case the wing has a potential fuel storage volume of around 2 cu. Mts (1600 kgs) so there should be no lack for storage volume if the wings volume can be brought in to play. Unlike swept wings the trapezoidal wing is more amenable to wing tanks as far as CG considerations are concerned; The Raptor reportedly uses wet wings but there must be some technical reason why the wing is not “wet” in the AMCA; Ideally one would cram as much into the wings as possible and work hard to release the fuselage space for equipment and reduce the cross section.       

The physical details of the aircraft and its equivalents are placed in the Table 1 and some comments are included.

Prospects

That the aircraft, if it meets the specifications, it will meet the threat is obvious; the specifications were issued by people who have grown old on the job of air dominance and defence. Indeed, it is my case that the aircraft is over specified and over capable and there may be simpler alternatives but that is for another piece!   However, taking the specifications as a given, what are the cautionary signs about timely induction into service?

It is obvious after the lessons learnt from the Tejas there should  be none of what journalists very politely called “overdesign”. Structural weights, systems performance, inlet trunking design - but not possibly the blow in and blow off “shuttering”, space for various items, weight and CG control and a host of niggling problems that the Tejas suffered because of a bungled preliminary design made worse by unwillingness to listen to the critics during PDR and the absence of any “Chief Designer-ship” will presumably not recur.

 Presuming that ADA has had a fruitful and constructive discussion with the IAF and the Government and has accepted the recommendations the project is set fair. Given the start of metal cutting a few months ago and the greater monitoring by the “owner” i.e., the Government, a prototype roll- out circa 2025 should be possible. However, a prototype roll out must necessarily be followed by a rapid development induction into service according to agreed timetables. We have eaten away all the fat that the 42 squadron Airforce afforded to the Tejas project’s delays. Similar delay with the AMCA will be doom for the IAF.  However, for this reviewer at least,  there is a sense of unease about the programme, particularly in the “post first flight “stage.

Given this tight rope situation regarding re-equipment one cannot put a finger on the sense of unease about the “subsequent to roll out” phase of the project but my personal concerns are:

The ADA has not shown the kind of “on the top of the Job” expertise that one would have liked to see. Open-source information are scant but I mention three details as disturbing symptoms:

i)                  The initial models even as late as 2014 were showing a fin so “agricultural aircraft” that it could not have been stealthy. How could the project team even think of it- never mind if the Koreans had a somewhat similar fin.?

ii)                The models displayed until fairly recently showed air intakes with diverters when stealth is supposed to be a feature. DSI (Diverter less Supersonic Intakes) technology- sometimes called “Ferri” (after its inventor) intakes- was known in the early sixties e.g., Chance Vought F8U Crusader 3 and declassified in the 1970s. It was not used then because everyone wanted Mach 2 speed and flow control and intake pressure recovery were important considerations; some form of variable geometry for the intake was de rigeur. With the F 16 the Mach 2 speed requirement became passe and the DSI became both feasible and superior being lighter, simpler and stealthier. By the time of the start of the AMCA project i.e., 2007 the DSI intake was common knowledge and a slew of fighters including the F 35 and the JF 17 were featuring it. The AMCA project studies did not. 

  Had it been of the requisite calibre the AMCA project team should have shown this even in the early studies, The point I am making is it is not enough that the DSI was incorporated finally. The point is without a “wide awake” project studies team we have uncertainties about the quality of the leadership during the Project studies and thereby on the subsequent quality of the design itself. The Tejas project suffered due to this problem of obvious neglect and the repetition of the same symptoms is unsettling. Perhaps my disquiet is a case of the homely saying “A Singed Cow will start at the sight of vermillion-coloured clouds". Though possibly it is already too late to correct past mistakes, extra close monitoring by the Government and the IAF is now needed if painful history of delay is not to be repeated.

iii)               Whilst ADA claims that it has learnt lessons from the Tejas project-presumably the lessons should include the fact that new technology requires caution and respect, I find it bemusing that it has no effort to convert or rig up one Tejas prototype to prove the DSI concept and generate hard design data. That way ADA would have cleared away potential DSI performance issues as one more mine swept away from the minefield of aircraft development. The conversion of a Tejas airframe to take DSI is quite easy and simple and did not require major effort; it needed initiative, love and interest-caritas to put it in one word. Calculations are fine but nothing beats the assurance of hard proven facts. ADA has failed to take this precaution

iv)              It is troubling to note that the full- scale testing of the radar cross section is yet to commence -the full-scale model is expected to be transported to Chennai sometime in August. If results are not right it will affect schedules. There are some problems which have to be tackled in detail before being integrated into the whole and this was one of them.

v)                The design of the internal stowage systems of weapons is a key feature of the 5^th generation aircraft. There has been no news so far on a prototype of this feature being flown.

 To put it in short: Worry is the Designer’s best friend and it appears that ADA has not worried enough. If things go wrong- and they will in the most inconvenient manner -we may be in for a repeat of lengthy delays due to avoidable “corrections”. Correcting mistakes on a prototype is time consuming and more so if it is attempted to be done surreptitiously something we have seen in the Tejas programme. I again repeat there was a need for real “Technology Demonstrators” and we have, perhaps, missed the bus.  The prototype may fly on time but development will be protracted because we have already courted some very avoidable risks. Now ADA needs to be very lucky or extra ordinarily smart in redesigning and remanufacturing  prototypes.

Engines

The AMCA will be flown with the GE 414 but the desired engine will be a yet to be conceived engine of 125kN. This again is of a pattern with the HF 24 and the Tejas and we know where they led to which is why I wondered about that clerk in the South Block! As a rough estimate the AMCA will need about 85kN dry thrust from each engine to super cruise which is, at present, well above the “stretch” of the Kaveri. The AMCA therefore must rely on the successful development of the new engine with foreign collaboration which is an ominous portend.

 By knocking off the super cruise from the specifications we may be able to make do with much lower power and a development of the Kaveri can then become a contender. The AMCA, thanks to its need for internal stowage of disposable load in stealth configuration, has a much larger cross section and supersonic drag is a direct relation to the aircraft cross section. The physical explanation is simple. Above M.0.8 the wing and the fuselage cross section begins to act as a “piston” compressing the air ahead of it and gives rise to the so called “supersonic drag rise” when in addition to the usual drags- profile, induced, skin friction etc we get “wave drag” something to the tune of double even between Mach 1 and Mach 1.3. Figure 2 compares the cross- sectional areas of the HF 24 with that of the AMCA and we see that the area is a reason why, though the HF 24 could go supersonic on 20kN engines the AMCA will need 85 kN engines to super cruise. Since internal stowage is a must for the AMCA “super cruise” may be discarded to allow the Kaveri as a contender.  

Comparing the figures in the table shows that the aircraft as specified is a very reasonable one with no major alarms or "obvious even to a school boy" shortcomings. The only doubtful item is perhaps the empty weight is “optimistic” by about a ton, more so if super cruise engines are fitted.. This is a red flag to be seen with caution. The lower specific fuel availability is commensurate with our defensive posture and smaller distances. Should it come to a “dogfight” at high or low altitudes the AMCA should actually be slightly superior to the F 35 and the J 20. The greater length -some 4 mts.-of the J 20 is noteworthy and the significantly greater fuel capacity indicates that the Chinese probably see the J 20 as a stealth “weapons carrier” intruder rather than a “dog fighter” which as a design approach is astute-even if it is Chinese! The “dog fight” ability of the J 20 at high altitude would be quite poor with the inertia of that long fuselage make TVC an imperative necessity. Talk about of making a necessity out of a supposed virtue! Incidentally the “radar signature” of the J 20 has come in for some derision but jubilation is unwarranted. Putting radar reflectors on the J 20s being observed by the IAF is exactly what Sun Tzu would do! Incidentally during their airshows in pre-covid times the Chinese ensured that the radar/IR and EM signatures were masked to the extent possible.

Re- examining the specifications

Do we really need the AMCA specifications? The Chinese and the US have those “specns” because they “need” that aggressive scenario and they have the Technology. At this point we have neither the technology nor the need.  To examine the question, we need to look at the genesis of the requirements of the Raptor and how it is suited or not to the Indian scenario.

It is the Americans who, regrettably for the nations involved, require a capability to be able to institute “Regime Changes “all over the Globe- apparently for Democracy. There have been numerous (Iraq, Serbia, Libya, Afghanistan etc.) such changes and attempts to change since the 1980s. Another political requirement has been to achieve this capability without incurring too many casualties. It is in this context alone that the Raptor makes sense.  It also endorses my view that it is the Government that should spell out our political war aims along with time scales and only then will the Services release the weapons specifications.

The Americans have a Global Strike Task Force (GSTF) comprising at one time around of 48 F 22As, 19 B2A Spirit and 56 B 52 bombers with necessary E3A surveillance aircraft along with associated tankers etc i.e., an aerial equivalent of the US Navy’s Carrier Group. The scenario in which the Raptor is supposed to operate is in the opening phases of the war when flying at extreme altitudes about 16,000mts. i.e., well beyond the capabilities of SAMs (many types of which lose KE and become sluggish at high altitudes) and knock out the opposition’s command and control centres. Once this air superiority is achieved the legacy weaponry and UAVs can the move in and destroy in detail.

The need to escort and protect the B2s and the B 52 explains the dog fighting element in the Raptor’s capability. Some of this capability is specified simply because the American Industry is capable of such tremendous abilities -never mind that their solutions are never cost effective. Such capabilities of course come at horrendous cost and the planned procurement of Raptors declined from 750 to 560 to 322to 280 to finally in 2005 to 189 aircraft. I have given the figures to underline that the cutbacks were hard fought; The USAF surely wanted them but the aircraft was unaffordable -and quite possibly not quite so “developable”- even for the formidable US Industry. So where do we stand with our program?

The Raptor development programme is worth recounting if only to calibrate our expectations. The USAF issued a Request for Information for a Advanced Tactical Fighter (ATF) in September 1985. Starting from an initial submission of six proposal from six vendors the YF 22 and YF 23 (pl. note TWO contenders) were funded for full scale development in September 1986. The first flight took place five years later on September 1991. In an excellent example of how the specifications should reflect the political situation- “war aims” if you like-the collapse of the USSR saw a revision of the specifications. High altitude ceiling, field length restriction and most significantly Mach 2.5 top speed were waived all of which significantly reduced the challenges of engineering development. 90% of the testing was completed within a year when the first crash occurred in 1992 due to a software problem. The subsequent problems of developing of the Raptor’s systems are well known. To rub it in, if this class of aircraft is so difficult to develop and so expensive to afford, what will be our own prospects, specially, as of now we are having just this one programme in the fire and there is no back up - and the Air Force is in bad need of numbers.  

The F 22s specifications make sense only in context of an aggressive political capability but it is an expensive capability. It also does not make sense as a” stand alone” design. It must exist as a part of   well- equipped and balanced force of attack bombers, Inflight Refueller , AWACS et.al. 

Our more pacific war aims- of defending territory- requires us to neutralize the Raptor and the J 20 but not necessarily by dogfighting them. The Russians revived the massive MiG 25 with new radars etc to have the MiG 31 as an improvised  solution to tackle the Raptor. We do not have the MiG 25 but we can make the use of increase in the intelligence" of AAMs to design a small high altitude subsonic/transonic "sensor rich" platform based on 3X HTFE 2500/40 as a "sniper". This can be supplemented a series of transportable low-cost ground-based systems. An aircraft much smaller and simpler than the AMCA but more feasible and developable is better than unfulfilled promises based on yet to exist engines. Despite its "lower" specifications" it is  better than a perfect solution that is uncertain..        

Table 1   

SL.No.	Item	AMCA	J20	Raptor	F 35
1	Crew	1	1	1	1
2	Span	11.3	13.1	13.56	11
3	Length	17.6	21.2	18.90	15.7
4	Height	4.5	4.69	5.08	4.4
5	Wing Area	55	73	78.09	43
6	Weight We	12,000	18,000	19,000	13,290
7	Normal Weight	18,000	30,000	29140	22,471
8	MTO	25,000	35,000	38,000	37,151
9	Thrust	GE F 414 2x57.8 /97.9 2x ??/121kN	Chengdu 2x106/161	P&W F 119 116/156	P&W F135 1x128/191
10	Int. Fuel	6500	12,000	8,200	8278
11	Fuel fraction (kg/ kN dry max thrust)	28.11	56.6	35.34	64.67
12	Aspect Ratio	2.32	2.35	2.354	2.81
13	Weapons bay (Length x Width X nos.) depth is suitable for 400 mm di munitions	2240x4000 (Ventral)	6354x2363 (Ventral)+2x 3634x560 (side)

 

Notes:  

1.      The lighter weight of the AMCA vis a vis the smaller (smaller wing area, shorter single “engine” fuselage) of the F 35 is noteworthy. A possible partial explanation could be that the US aircraft is multi role/Multi service with higher standards of equipment. Compared to the J20 and the Raptor empty weights the AMCA empty weight at 12,000 is at least about 1000kg “optimistic” and possible infeasible for the heavier 125kN engines..