“Waddling around the deck” – Weighty Matters & the Tejas part 2.                                                         

 by Prof.Prodyut Das

In the 1950’s war classic “The Cruel Sea” by Nicholas Monserrat, the Australian Gunnery Officer of the Frigate HMS Saltash, apparently dissatisfied with the performance of the gun crews he was working up, is heard to yell “If you jokers are trying to break my heart by waddling round and round the deck like a bunch of old whores on a picnic- you have to try a long, long time! Get cracking!”. Reviewing the blundering process of the Tejas programme I am reminded of Lt. Allingham’s exasperation.

When I had mentioned in my blog “Weighty Matters” that the empty weight of the F 16 A Block 10 was 6615 kgs people either did not believe it or saw it as a yet another unjustified attack on a valiantly struggling project; very few saw the opportunity for the correction the criticism revealed.

The opportunity lies in the fact that if the substantially larger and more powerful F 16A could be designed to a basic empty weight 6615 kilos then it holds that the basic empty weight of the Tejas Mk1 should be somewhere between 5350 kilos and 5500 kilos. At those weights the Tejas could become quite a sizzling performer. 

We blame the import lobby but the culprit is ADA. The answer to the import  lobby is not complaints but performance. There never has a DRDO product that has been ready more or less on time, performed reasonably well, was competitive to produce and yet was passed over for imports. If there has been let us discuss them with facts so that the misdeeds can be exposed. Qui male agit odit Lucem! The evildoer hates the light!  

What are we comparing?

We are comparing the weights of the F 16A block 10 with the Tejas Mk 1/1A because they are equivalent LWF category of aircraft. The F 16A block 10 was the aircraft that was used by the Isr.A.F. on its famous daylight strike on the Iraqi Atomic reactor with such precision that initial belief is that the Israeli had used smart weapons. I make a mention of this to underline the equipment level was comprehensive for operational tasks. 

The equipment list for the F 16A bl.10 is Pulse Doppler AN/APG 66 Doppler radar, IR missiles, a Vulcan 20mm revolver canon, GEC Marconi HUD, Singer Kearfott INS, Sperry ADC, IFF, UHF, VHF, ILS, TACAN, Dalmo Victor AN/ALR 69 RWR, chaff & flare and side stick controller. I presume that being an American warplane a FR probe is a given though I do not see it being specifically mentioned.

About the equipment fit for the Tejas Mk1/1A the analyst is on less sure grounds. My problem is in getting a “hard" list. As an example - the Tejas has a SPJ but going by Govt. released information the fitment of the SPJ required the removal of thirteen (sic!) LRUs. So  if you ask “Is the Tejas fitted with a SPJ the answer is a “Yes” but if you were to ask “Is the Tejas operational with a SPJ?” the answer would be “No”. To cut through the confusion and delay. I am conceding in favour of the Tejas and assume that the equipment level on the Tejas is also sufficient to allow it to carry out  a similar- to -Osirak type daylight raids over enemy territory but keep in mind the windage allowances.

How do I say 5300 kgs for the Mk1?

If the F 16A , a bigger fighter with a heavier engine, bigger fuselage, a Vulcan gun ,negligible composites and a heavier radar can be designed to weigh 6615 kilos then it is logical that the smaller Tejas should be lighter. 

To establish how much lighter, we must get into a bit more detail. First, we must put down the direct weight savers in case of the Tejas.

Primary weight savers:

1 Due to lighter engine weight of Tejas                                                                320 kgs.

2 Due to shorter fuselage                                                                                                                                              200 kgs

3. Due to Vulcan Gun                                     150 kgs.*

4. Lighter radar                                                                                                                                                               25 kgs.

Total Primary weight savings as indicated by the above is 695 kilos vis a vis the F 16A

*The Tejas has the GSh 23 mm gun fitted weighing with installation about 60 kilos. However, given the gun firing test have not been cleared it is unlikely that the Tejas parked at Sulur are fitted with GSh 23 unless the IAF has a surfeit of 23 mm and does not know what to do with them.

If we now consider the secondary and tertiary reductions in the Tejas e.g. extensive use of composites (120 kgs) additional plumbing ( cables, pipelines, ducting etc ( 100 kilos) , lighter wheels and brakes ( 70 kilos)- this due to lower landing speeds and weights, stubbier undercarriage struts ( 30 kilos) we are close to a Tejas weight  1000kg lighter than the F 16A Block 10 as a first estimate which means that the empty weight of the Tejas Mk1/1A should really be in the region of 5300 to 5600 kilos.

 This brings up the pointed reminder that the original estimate of weight by the GAM Dassault Consultants who worked in Bangalore for a year was 5300 kgs. One may or may not agree whether the consultancy fees reportedly of  100 crores was justified or not but one must admit that they did professional job! An empty weight of around 5350kgs  is realistic and should be ADA's design aim.

 I had written about the cruciality of the weight issue on the performance of low AR tailless deltas in in one of my early reviews of the project in Vayu Aerospace “Wisdom & Courage” Vayu V/2010 and also in “The LCA -beloved aircraft or Lemon” (I/2015). This last is also available in my earlier blog  profprodyutdas https://profprodyutdas.blogspot.com.  The weight must be brought down to the figures arrived at i.e 5350 kg.

Those handling ADA are cautioned that whilst asking for funds if ADA claims that it can hold the empty weight of the Tejas Mk2 to 7000 kgs then logically ADA should also be able to demonstrate it on the Tejas Mk1 by achieving 5300 kg on the Mk1A. If on the other hand they can’t and it is 7800 kilos then, given ADA's design capabilities as shown by the numerous concessions, performance wise the Mk2 is probably going to be a very large Mk1!. 

Indeed I believe that ADA should be “tested” to reduce the weight of the Mk1 substantially before being entrusted with the Mk 2. The reason for this caution is we are dealing with an organization that has been long on promises and short on deliveries.  If the standard of engineering is identical to what they demonstrated in the Mk1 then we can expect an empty weight of the Mk2 to be around 8500 kilos in which case we will have a Medium weight Tejas LWF instead of a MWF. You have been cautioned! 

What will we get if we lighten to 5300 kgs?

What we will get is an extremely nippy fighter which combined with its small size will be quite effective in general combat. The following are some of my prognosis:

1.      A reduction in take off distance by about 20%.  

2.      A thrust to weight ratio of 1:1 immediately after take- off and well exceeding that in  half fuel clean combat condition. The a/c handling will improve even in hot & high conditions and the performance of the fighter-as a dog fighter- will be unique.

3.      The Touch down speed will come down to < 270 kmph from the present 308 kmph. The requirement is 248 kmph.

T The top speed at sea level currently at M 1.01 will improve slightly to about 1.03. The specification asks for 1.15 but this can be achieved only with a minimum fuselage plug of 0.5 mts or with much better build standards.

4.      Rate of climb and sustained turn rate and range will improve by about 15 to 20%. 

6.      Indeed I expect a substantial “bonus” increase- say further 15%- in range as the very low aspect ratio tailless delta is hypersensitive to weight. If I knew a few more small details about the rigging I would be more confident; my present feeling is that that ADA has overlooked this possibility. 

To further increase the STR a "cranked" wing obtained by tweaking the present delta as discussed in one of the earlier issues of Vayu may be useful.

What prevents us?

In the above section I used numbers and basic engineering. In this section I am making some conjectures . 

1.      The problem of getting the Tejas into an acceptable fighter is not seriously technical or funds but a large mess of small simple problems which would embarrass every one concerned if it became public knowledge. This is being avoided thus delaying correction.

1.1. The rectification of such elementary mistakes will cause  serious loss of face not just of ADA but the Raisina Hill babus who have blindly or in their ignorance of matters Aeronautical backed this project for so long without decisive management intervention. There could be other reasons because delays in this project are a great force multiplier to the invisible Import Lobby.  

2. 2. Making the corrections on the Tejas Mk 1 to achieve the performance indicated above may postpone the Tejas Mk2 funding because it will be less urgent; A rectified Mk1 would do the job well enough. Getting funding is a subject Scientists are quite sensitive about.

3.   The major culprit: It appears whilst reading a rather badly written government report that the load tests on the Tejas airframe have not been fully completed. If I believe what I have read it is a criminal bit of penny wise-ness or it is sabotage. The load test on an airframe have two purposes,

i) i) To prove that the airframe is strong enough to bear all the loads it is designed for.

iiii) to prove that the structure is not overdesigned and thereby overweight. The structure must break close to its design load. The HF 24 Marut' s airframe was extremely strong but it broke at < 1% over the design limit.

 I  It seems that this very crucial test may be pending. Without this test ADA designers do not yet know how much overdesigned i.e. overweight the airframe is. Therefore they cannot know how much they can reduce. 

TThe cause of this studied "negligence"  may be simple. In correcting it  the entire tooling for the airframe or very large parts of of it may have to be re-worked or scrapped and that would be a serious blow to the prestige as well as a bit of a public scandal. Ergo an attempt to do it quietly.   

Rectification

There is no need to discuss what needs to be done because what WAS done in 1983 in setting up , recruiting and running ADA was skittish as in College skits. Even simple steps like  an independent audit, purge and re-organization will give immediate results. The problems are not funding or Technology but very common human ones of management. ADA has a very substantial "vote bank" who depend on "Research Grants" from ADA. The Audit must be done by a broader base of auditors if we are to find an answer to the crucial question how to get the aircraft up to the full potential it has and to make it production worthy. One check needed is to see if we will get the promised number of aircraft in April 2024 is to see if all those promised are NOW in the Final Assembly hangar. If not then prepare to be "astonished " in April 2024.

Conclusions

The IAF needs to be a 50 squadron force for reasons I have repeated elsewhere. The Tejas can fulfil the role of "the maid of all work" or "Cooking" warplane very effectively, equipping perhaps half of those fifty squadrons. An efficient development and manufacturing programme can deliver the warplanes at prices one third to one fifth of international standards. As the recent sales tours have shown the markets for exports are also there. 

The inefficiencies - to the point of being "bungling"- has been the greatest aid to the import lobby. Had things gone as per plan- -Turkey and Korea has shown that that is no unattainable feat- the procurements and upgrades from Russia and France in this century would have been unnecessary. The Raisina Hill Babus must reflect and "do the needful"!