Weighty matters; The weight of the Tejas & the F 16  

Part 1                            

Prof Prodyut Das

Yesterday (15/03/2022) there was shock and annoyance when I mentioned that the weight of the F 16A -and not the YF 16 as some suggested- started at 6360 kgs. This ire is probably because the ADA Tejas , the smallest fighter in the world, weighs somewhere around 6700-7000 kgs depending on the wrk. number. Reactions varied.

Since the topic has direct relevance to the state of engineering of the glacially progressing  Tejas I followed up the exchange; let me put down first the figures.

The empty weight of the F 16A as given by the late –and much lamented- William Green in his Observer’s Book of Aircraft 1985 etc as 6613 kgs. This was ofcourse for the F 16 Block 5 and block 10 aircraft of which about 300 were made. Mr. Green needs no vouching among the cognoscenti but just how accurate his work was I had a first-hand experience of. Since it is no direct relation to the topic on hand you can read it later in the Anecdote 1 at the end.

The F 16A was designed to be the ultimate dog fighter of course- “not a pound for the ground” being the guiding philosophy expressed in lingua Yankee. However being American it was –by standards circa 1970's - quite comprehensively equipped. 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.

 No mention is made of FR. Being an American fighter I presume FR was a given- they have to cross the ocean to fight! The equipment suite was sufficiently comprehensive for the F16 A Block 10s of the Isr. AF to fly to the Osirak Iraqi Nuclear Reactor near Baghdad on 7/06/1980 in broad daylight and destroy it with Mk 84. Indeed so accurate was the attack it was initially thought “smart weapons” had been used by the Israelis. 

The point is that at 6600kg empty weight teh F 16A bl.10 had better equipment levels than the Tejas Mk1 which weighs 7200 kilos. They are parked at Sulur because , by my assessment, if a significantly bigger fighter using heavier materials and equipment, is lighter than the  Tejas , it speaks of the possibly very bad quality of engineering leadership of the aircraft.

So the tweet, and I quote:

That F16 was museum era ,"widow maker" junk , rushed into service with bare bone after F4 phantom's Vietnam fiasco. It was "so advanced" ,that it's test pilot had to risk his life to go fr "unannounced" lift off, bcos it jumped like a frog on taxi trial. #TejasMk1 #TejasMk1A  

You see the kind of argument one has to put up with!. Ah! Me!

The blocks 5 and 10 set about rectifying the usual teething problems” –water & accumulation drainage and such like. 97 Block 1 & 194 Block 5s were made between mid 1978 and 1981 the American IOC being completely professional and the aircraft was quite serviceable for combat e.g. the Osirak Reactor bombing above. Later all F 16s of these blocks were upgraded to at least Bl.15 standards.

The first major F 16 A upgrade introduced in 1982 was the block 15 introduced which introduced 2 additional stores pylons (100 kilos increase inn wt) bringing total to 7 stations, an upgraded Radar (+30 kilos more) , a larger fin with 25% more area (+30 kilos) to improve stability after addition of the two pylons forward of what old aero modeller' s would call the CLA and the introduction of the AIM 7 Sparrow missiles. 

The Tejas “fanboys” who claim that the request for replacement of the R 60 by  R 73 - twenty years after the start-was an Air Force iniquity if not direct perfidy  and a  major cause of delay will please note for future reference- the provision of AIM 7 and the increase in load capacity of the pylons was done as a matter of routine. In addition there was additional chaff and flare dispenser Tracor AN/ALE-40 and provision for AN/ALQ 131 external ECM /Jammer. A later up grade introduced better displays, capabilities of newer missiles such as the AMRAAM, Penguin and Maverick. Depending on the upgrade the empty weight went up to 7300 kilos .

The F 16 C /D ,whose engine was a good 800 Kgs heavier than the F 404 have an empty weight of 8716 kilos  but it is in another class and in addition to the above it has NVG, advanced radar, internal SPJ bigger radar, conformal tanks etc to an standard that cannot be achieved by the LCA Mk 1/1 A if only because the Tejas air frame is too small to have both the equipment and fuel needed to match the range payload of the F 16.The Tejas Mk 2 with more space and power can take advantage of later i.e. lighter less power demanding  avionics but I feel the Tejas Mk 2 air frame has not been properly handled. I have discussed this in my earlier posts.

As of the moment it is reasonable to say that the projected Mk 1 A will probably compare with the F 16 A Block 15 in equipment fit though I doubt if the Tejas Mk 1 A will then have the range payload of the F 16 A. 

Table 1 Weights of the F 16 and the Tejas compared

1		2	3	4	5	5	6	7=5-6
Sl.No	Type	Length	Span	Ht	Wing Area (m2)	Empty Wt (kg)	Engine type& Wt (kg)	Equipped airframe weight(5-6)
1	F 16A Bl.10	14.52	9.45	5.01	27.87	6615	F 100-PW-200 (1467 )	5148
2	F16A Bl. 15					7300	F 100-PW-200 (1467)	5833 kilos*.(5683) see note below
4	ADA Tejas Mk1A/Mk1	13.2	8,2	4.4	38.4	6600-7200	984	5616/ 6200

 

Note The F 16 has a smaller wing area it has the weight penalty of a stabilizer which would be about 150 kilos in the case of a F16A Bl.15 whereas the Tejas is tail-less.

*I should have also subtracted the weight of the radar (150-200 kilos) depending on the model but the differences were small the F 16A radar being about 25 kilos heavier than the Tejas. Another difference is the gun installation. The Vulcan gun (125 kilos) along with the mounting and ammunition tank say about 25 kilos so we are looking at a further reduction of 150 kilos. The Tejas gun system will weigh about 75 kilos when fitted. The ejection seat I have not considered because the the Martin Baker 16 ad the ACES are comparable in weight because the figures even as given is sufficient to make my point clear.

Remembering we are comparing an aircraft which is yet to enter service with something that has been there and done that; the conclusions- it will be depressing- I will give in the II part. The F 16 C/D Bl.50 plus is another beast altogether. I give below ,only for the record.

3.

F 16Cbl.50

8437

F 110-GE-129 (1789)

6648

 

Anecdote  1

This piece began with a mention of William Green’s Observer’s Book of Aircraft . For the cognoscenti William Green requires no vouching. His accuracy and exactitude was well accepted without any second thought but just how accurate The Observer’s book of Aircraft was I found out personally.

Somewhere in 2004 the IAF finally got around to retiring- with regret- the Canberra. Someone had “retired it earlier but the old Girl fought back and was re-instated (another  typically Indian story!) ,went to war in Kargil, one of the aircraft came back with a Stinger hit in one engine but this time it was final. She had to go because maintaining her was no longer possible.

I wrote to Air HQ saying perhaps the air frame could be reconditioned and re-equipped with Russian engines and accessories if that was the only problem and incredible as it sounds the Air HQ allowed me to visit the Canberra base at Agra ( Raja ki Mandi ). Photography was not allowed so I spent a day making sketches for the engine installation and the other parts of the structure that I needed to make a presentation. I could not help marvelling at the sheer intelligence and simplicity of the structure though the numbers I give are from memory.. As an example of "Concurrent Engineering"-before the Term became Conference worthy-the main spar was two bars of aluminium about 50mm square sandwiched and riveted at the top and bottom of  two webs about 6mm thick ( just like perhaps the Fokker D7 wing spars but in metal. The webs were punched with large ,flanged, lightening holes. The material was used exactly and only where needed and yet it was so utterly simple to make.

I must get off the horse! The point I wanted to make was about the accuracy of information. The MiG 21bis' R 25 w/o reheat was of course lighter and more powerful than the Avon 200 srs of the B(I) 58 and the B.Mk 66 and would have made a considerable difference to the range payload of the Canberra and I wanted to examine that aspect so needed the diameter of the fuselage at teh bomb bay. Lacking no immediate source I checked up from the Obs.Bk. of A/c 1961 ( it had been a birthday present, once!) which I had on the handy rack and estimated the fuselage diameter from the usual 3 view drawing of Dennis Punnett and it came to 1970 mm. When I measured it on the actual thing – an ex New Zealand B 66 with a Tusker emblem AFAICR – the dimension was 1940 mm. Take an awed bow M/s Green & Punnett! 

Post Script 

After my visit to the Canberras at Raja Ki Mnadi ( Agra) I went to AF HQ to meet the "customer" presenting to them the expected increase in range payload performance on which I  focussed   because increase in speed would be endangering the venerable air frame to not much avail. My proposal was quite feasible but only justifiable in case of pressing need which fortunately there was none.What I was surprised at was the genuine affection and concern the young air crews and their commanders had for their aging Aunt of an aeroplane. If THEY had been the arbiter we would have got the job!