Lessons
from the Tejas, ALH, HJT 36 Prof.
Prodyut Das
Iss3 . Dated 29/05/2024 - with a new photograph and further comments comments about spinning of the HJT 36 and the untidy job we have got and ways to improve it.
The first
flight of the Tejas Mk1A was fortunately a muted affair. Someone had the good
sense not to have the usual hoop-la; For all our self- congratulation on X the
Aeronautical World will look at the flight differently; to them it will be that
40 years after the first release of funds the Indians have finally got a
fighter which -to use the homely Bengali phrase- “paat-ey deya jaai” i.e.
can be put on the dinner plate. My using the phrase is no endorsement of the Mk1a.
It means that the Mk1a is perhaps worth allotting hardened shelters at a few of
the quieter-front line airbases so that further trials prior to induction can
go on. (Note 1).
The Mk1A still needs more “improvements” dictated by service experience and of course weight reduction to <5900 kgs which will make the Tejas Mk1B quite formidable. We have also the production rate to maintain. How our young gentlemen-and ladies- abuse the Tejas and discover the weakness that must still remain in the aircraft is another caution. The mature caution of the Duke of Wellington, presented, after Waterloo, (Note 2) with his portrait inscribed “The Invincible Wellington” returned it with a “Don’t halloo till you are out of the woods” is applicable.
The Mk1a is what we should have got in 1990. That possibility was scrubbed by the way we set up ADA. It has taken forty years to do something (Mk1a) that could have been done in seven. If we do not admit that the development of the Tejas has been most unsatisfactory, if we do not purge and reorganize the Aviation Industry then the AMCA and any other project is doomed.
It is usual
to hear that all our failures to develop the Tejas is due to the Import Lobby,
the IAF’s preference for “foreign goods”, lack of technology, first time we did
an aircraft, funding and even those who criticize the programme’s delays. The
blame for delays depends only on the structure from ADA HQ upwards.
If we
examine the fates of the three aircraft projects initiated during the period
1984 to 1997 i.e. the Tejas, the Dhruv Light Helicopter and the HJT 36 it raises the question as to why under the same system and constraints
the results were so different. The answer will indicate what correction is
needed. The complete answer cannot be without access to South Block record. Below
a thumbnail sketch of each project.
Advanced Light Helicopter
This is the
most successful programme of Indian Aerospace in almost a century of Indian
Aeronautics. This started a little before the Tejas, the specifications very
demanding as helicopters go because of the unique high- altitude capabilities
required and the configuration was changed from a single engine to twin engine
six years into the programme. It used many new technologies- rigid rotors,
composites, glass cockpit, conformal Novikov gears et al. It ran 2-3 yrs late
but it was in service by 2000 and today over 300 have been produced which have
clocked 300,000 hrs under some very arduous service conditions. There were some
exports which was probably sabotaged by alarmed rivals. As with any successful
project it has spawned several derivatives (nota bene derivatives
not development) of the basic design- Rudram, LAH, Prachand etc and has given
the team confidence to take on the Mil 17 replacement. There has been the same
delay in ensuring continuity of project sanction so the original team (as with
the HDW submarines) wasted out but the success of this project is truly
remarkable.
The HJT
36
This
project got off to a brilliant start, better than even the ALH above. Flown
within 3 years of go ahead showed the programme management was faultless and
ran like clockwork. It was obviously well engineered, witness the trouble-free production
and the flying hours during the test programme. It is noteworthy that the HJT
36 programme at Rs 750 crores cost one twentieth of the LCA airframe development
programme.
Just when
one thought the HJT 36 was going to repeat the success of the ALH progamme and
was out of the woods it went- literally- in to a flat spin circa 2007.
Spinning troubles with trainers is common enough to suspect there is an ISO
on it. (Note 3). Why it should have taken seven years up to 2014 to
begin to correct the spin problem is a question only Raisina can answer.
The sequence
of this unacceptable delay was:
1. The HJT 36 had a series of accidents
including the canopy coming off during Take Off. (Note 4) and a
mysterious firing of the ejection seat whilst the aircraft was under assembly. One presumes that as is usual elsewhere the
prototypes were kept under CCTV surveillance as items of considerable
commercial potential. Our prototype security has not been conspicuous by its
presence e.g. Saras crash, complaint of Arjun gearbox being sabotaged,
Howitzers barrel bursts etc. Will we ever learn?
2. The engine thrust was deemed
marginal by the customer and a decision was taken to switch from the Larzac to
the Saturn AL 55.
3. The Saturn was about 60 kgs heavier
and so NPO Saturn was asked to reduce the weight to avoid CG shift. This was a debatable
decision. About 3-5 kg ballast should have done the trick so that the tests-
which would expose the other corrections required- could continue instead of
waiting for three years to get the new reduced weight engine.
4. Any modification e.g. weight reduction to an
existing product will attract massive “development charges” apart from the
delay. It should be interesting to know- if only to evolve SOPs- what group
pushed for this engine change and engine weight reduction. It added
seven years to the programme.
5. After 7 years, circa 2014, the project
was resumed, a foreign consultant- in my view completely unnecessarily (again,
note 3)- brought in and the trials were completed in 2019. Going by the
pictures a simple but untidy solution has been given.
The ALH Dhruv: During the period under discussion,
it was impossible to bring in the competent and dynamic Private sector the ALH
showed that very good success could be possible despite the bottlenecks of the
system. That the ALH was successful is not an endorsement of Marxist
Industrial policies which are fundamentally flawed. It is noted that the success
rate of the system was one in three in the sample considered. This has been
about the success rate of all Defence Development projects of this period also.
The more valuable lesson is that the usual excuses have less effect than is
projected and the fault or credit lies with the Design Leadership.
The
Tejas: The quick
summary of the Tejas programme (see Note 4 for a somewhat more detailed
exposition) can be put in two phases i.e. 1983- 2008 when problems were allowed
to be created & concretized and the period 2014 onwards when the
problems are being rectified but the effort constrained because it is
difficult to rectify a mistake once created into hardware.
The HJT
36 Sitara: This is the project that is the most interesting. The engineering effort was competent. The programme
management was probably better than the ALH’s. Funding and its control was
exceptional with the project costing one twentieth (1/20th) of the
Tejas, its scheduling exceptional the technology involved was within the
capability. Indeed, as of 2007 the project was heading to become a bench mark rivalling
the ALH and yet the programme stopped dead in its track in 2007 ejection seat
firing during prototype assembly etc. There was a spate of accidents from 2007-
canopy flying off during TO (note 5), a crash during testing, reviving somewhat
in 2014 and then taking five years to solve the simple problem of a spin even
after unwarrantedly calling in a foreign consultant. A thorough
investigation of the process by which these unhappy decisions were taken may
show up the reefs on which our project flounder.
Conclusions
1. Under the present command and
control structure about one in three make it to active service on time and in
acceptable condition. This ratio is noticed also in other projects
2. Delays and cost over runs are caused
by making elementary mistakes during project\studies and then trying to rectify then after they have been put
on to a prototype. This sequence is
completely avoidable. The HJT 36 spin, the TAPAS problems were failures in the ability to visualize basic, common airflow and control problems.
3. The above occurs because even in
teams that have competent management and technology abilities there is a lack
of “soft engineering” skills.
4. The expectations that a thing will work
“off the drawing board” is a direct product of 3. above and leads to hiding of
problems.
Note 1
The Mk1 is
useless. It is 2300 kgs over the weight recommended ( Informantion given by
ADA/HAL to CAG) and it lacks blow in or
suction doors of adequate size as witnessed on the improved Mk1A. Badly
overweight, with an engine not feeding properly and Indian runway temperatures
hitting 50+ degrees its performance cannot be good. It’s being in service at
Sulur, de facto an “inter factory WIP transfer” between two PSUs- the IAF and HAL,
is an indication of its worth to the IAF. The MiG21s are not retiring
from Sulur.
Note 2
Cannot help
mentioning that Wellington, the Iron Duke of Waterloo, thought the Battle of
Assaye, against the Marhattas, amongst his most difficult and hardest fought of
all his battles.
Note 3
The
Designing of aircraft for spin and recovery is aviation folklore ranging from
the aircraft being “un-spinnable” (CAC Winjeel), to requiring drastic redesign (SOCATA
Epsilon (rear fuselage, strake, and fin or HT-2 where the rudder had to be reshaped)
to the almost un-recoverable e.g. The Phantom II where the drill was to
eject if recovery was not achieved at 10,000 feet. Yet most aircraft go through
the spin test easily enough. This is because there are enough “totka”(
potion) or “jadu tona”( magic spells) or “old wives’ tales” available in aviation folklore to keep the
problem withing manageable proportions i.e. even if it fails at first it can be
made to work. HAL did not have access to the history of spin and its recovery
or else they would not have made the mistakes they did in the layout or brought
in a foreign consultant to rectify it.
It is an old wives’ tale that a tandem two
seat trainer will have too much side area ahead of the CG and this must be provided
for along with the greater inertia in the yaw and pitch axes. The solution is
to provide sufficient fin “volume” and be vigilant about weight. There are very
simple methods to find the CLA (Centre of lateral area) /CG but an experienced
designer can do it “by the eye”. Both the side area and the Cd of that area to
cross flows are involved. The ability to approximately visualize the flow, -a “CFD
in the mind”- is needed. It is then a simple matter to provide for it at the
time of making the layout. If you look at the HJT 36 you will notice that the
CLA is too close to the CG and the sides of the cockpit are as vertical
as the Great Wall. The spin trouble subsequently faced chould have been
expected and nipped in the bud at the project studies stage without doing a
single calculation.
The second
oversight in the HJT36 was the location of the air intakes. It copied the HJT
36 but it was the wrong thing to copy because the HJT 16’s position is unique-
I do not know why Raj Mahindra selected that position ( did he do it to
avoid looking too much like the Jet Provost?) - but if you look around you
will see all low wing jet trainers (Jet Provost, Macchi MB 326,MB 339,
SOKO Galeb etc have the inlets low,
slightly ahead of the root and blended smoothly merging with the fuselage.
No one has it sticking out like elephant ears in a mid- position as in the
HJT 16. My guess is that at the
stall (the first step in setting up a spin) the “Jet Provost” type inlet has
the engine sucking relatively undisturbed air -there was some report of engine
flame out in spin and the inlet is throwing up much less disturbed air to
the fin thus improving fin authority -the old wives’ advice- simplificate
and add lightness . Pl. carefully see the Jet Provost (both the early Mks and
the later Strikemaster inlets & compare with the HJT 16 or HJT 36- and then
compare their fin sizes. Time permitting the re-location of the intake
ducts of the HJT 36 a la Jet Provost and radius-ing the forward fuselage bottom
may improve stall spin behaviour significantly.
Note 4
I have for
long years written about the problems of the Tejas so I will ask you to read
them for details in my blog Prof.ProdyutDas2. The Tejas programme can be
summarized by imagining a situation where a very experienced group of Designers
were asked the question: What needs to be done to set back Indian Fighter
development by decades wasting money and importantly time so that in teh end they HAVE to import? Their
recommendation would have been:
Shut down the existing Design bureau and prevent it from bidding for the new project
1. Set up a new organization with no
previous experience.
2. Introduce FBW as a must have feature
and make no effort to develop in parallel that unknown technology on an
existing airframe e.g. Hunter or Marut or even in a Biz Jet.
3. Choose the most difficult most
“sensitive” configuration to develop – the tail less FBW controlled Ultra Low
Aspect ratio (>2) Delta- as the basic configuration.
4. To further reduce chances of success,
shut out everyone including the customer and his painstaking inputs when
designing the prototype.
5. Go in for a 65% (by surface area) use
of carbon- carbon composites right at the beginning. Composites are more
difficult to effect changes in. It will be remembered there was no
carbon- carbon fabrication facility in India at that time. This decision was probably
on the basis that one of the sister organizations had built a Rutan Design
homebuilt using foam and s- Glass composites.
6. Keep reinforcing failures. The first
flight date of April 1990 is missed. Instead of making management changes the
then DRDO Leadership strongly supported the failure and its continuity.
7. When the first funds (equivalent to
about 70 tons of gold) are run through the programme is massively re- funded.
8. Problems are kept within the
“mafia”. Everyone else is effectively out.
9. It is only around 2011, when the mistakes
have been cast into stone that the IAF and others are brought in to rectify the
mess.
10. Maintain a sustained media campaign
to Rewrite History about shortage of funds, lack of facilities, state of
development of the Indian Industry, lack of co-operation from everybody and even
the date of start of the project. Given the lack of interest and knowledge in
aerospace matters it helps to a great extent in distorting responsibilities
Note 5
Curiously the canopy malfunctions- the canopy
opening but not flying off- seem to be an HAL specialty- the HF 24 IT crash (7
Jan 1970) was also due to the canopy opening but remaining attached thus acting
as an airbrake and preventing the seat from firing. Gp. Capt. S. Das had
no chance. I here also record for posterity that the TP of the HJT 36 canopy
accident died under abnormal circumstances.
In this picture see how the intake is set low and ahead of the wing LE so at spin entry the engine feeds clear flow undisturbed by the fuselage bottom and wing LE. Note also the smaller fin size of teh provost because the blended intake does not throw up disturbed air to blanket the fin.
The location of the intake wrt the fin in the HJT 16 shows that at the entry to the spin much of the fin will be blanketed by the vortices shed by "stick out" ear intakes. Compare relative size of HJT 16 fin with Jet Provosts fin.
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