The Saras Flies!

geeth · Post by **geeth** » 08 Jun 2004 17:24

>>>most probably the structual skeleton was kept
very strong until all the stress and flight tests
are done.

I don't think the overweight was deliberate. Because, they have identified it as a problem few years before itself, and were looking for solutions.

ragupta · Post by **ragupta** » 08 Jun 2004 17:29

Can the overweight problem be taken care by more powerful engine?, now that the prototype is flying.

Given that the more powerful engine will add weight of its own, would it be a sound choice?.

Maybe a more powerful propeller will increase the cost or is not available or may not be advisable or not possible due to increase fan blade size. In that case can a turbofan be attached?.

Even in its failure, such project provide tons of learning experience, so in that case a great achivement nevertheless.

Now the question is how can this technological success can be turned into a commercial success?. Accepting the fact that there is going to be lot of naysayer, finger pointing, hesitation in providing further funding

, etc.

geeth · Post by **geeth** » 08 Jun 2004 17:31

>>>Could it be described as poor engineering if the weight of every nut, rivet and spar is not taken into consideration for an aircraft at the design stage itself?

Ofcourse, it is a must to do that. Then only you can calculate the C.G of the aircraft, after that the centre of lift >> location of wings on the fuselage >> movement of the C.G >>> dynamic stability of the craft - you can see weight calculation is the most fundamental thing to do, because lot of other things depend on that.

shiv · Post by **shiv** » 08 Jun 2004 18:21

The CG is easy to balance - whether you make the plane out of lead or out of Balsa wood you can make the CG come in the right place. The question is when you decide to use a combination of steel/Titanium/aluminium/composites to acheive particular degree of strength, should one not also calculate the weight of the components and whether the weight would exceed specifications for engine, payload and planned range.

As someone said "overweight planes" are common. But chipping down weight in a plane (as per my general reading) means sahvingof 5% weight from component x, 3% from component y, 15% from component z etx until you get the planned weight.

A plane is a basic framework of fuselage and wings designed to bear loads - and I think the highest load bearing parts have to be the strongest - usually of metals or mtal alloys. . Typically the wings (main spar) has to bear stress as well as teh undercarriage and engine attachment. The longitudinal framework of the fuselage has to resist bending and torsion to an extent, and the rings that shape the fuselage have to help in resisting the expansion/compression of pressurization and altitude flight.

What is the main wing spar made of? Dose it have heavy steel? Or is it Aluminium? Can it be made lighter and slimmer using some other materials? What about each ring and each rod that run the length of the fuselage? Can they be made lighter and yet equally strong? Can they be made to last 30,000 hours in their "newer, thinner, lighter" state or will they require scrapping along with the airframe itself at 15,000 hours? Is the newer lighter part replaceable - so it can be replaced without scrapping the whole a/c?

What is the undercarriage made of? Can it be made lighter?

What are the main engine supports made of? Steel? Aluminium?

If each structural pipe/rod weighs 15 Kg on average and there are 200 such parts - a reduction of 10% in the weight of each of these will result in a 300 Kg weight saving. Can this be done without compromising safety/performance? Can it be as simple as cutting strategic holes in the metal to remove a chunk of weight.

Can composites be used for the skin of the plane?

Too many questions, No answers

Surya · Post by **Surya** » 08 Jun 2004 18:57

Shiv:

A week or two ago there was an article in WSJ on how Airbus is struggling to decrease the weight on the A380. Lots of info on how changes in one area have to be compensated in another.

If Airbus can achieve its promised goals for th A380 a lot canbe learnt.

Umrao · Post by **Umrao** » 08 Jun 2004 19:12

Its not big deal. We have proven that it can take to air.

Just put the design staff on
weight watchers and
Dr. Atkins

It will slim down to the most appealing curves ever known even the gandharvas.

daulat · Post by **daulat** » 08 Jun 2004 19:24

steel is generally a no-no on a/c due to weight
for most purposes alu is good, particularly new al-li or al-mg alloys. v high speed a/c use titanium alloys. generally pure metals are never used, always in alloy form.

the strongest part is generally the wingbox which is usually somewhere around the point where all teh forces are acting on the a/c as a whole - these are typically machined out of a single al alloy block, ideally a single crystal. the CNC machines required for this are high funda, coupled with the mettalurgical skills required to create a single crystal large block of metal

the wings themselves carry most of the load but are also quite flexible - very noticable on large a/c, which are designed so that the lift moves the wing into the right shape instead of being rigid and therefore extremely heavy. you just have to look at the wings of a B747 on the ground to see how much they droop at the tips, compared to how much raised they are in the air.

probably parts of the saras can be shaved of metal, or some parts replaced with composites, then the c.of.g will need to be balanced by adding weight elsewhere or ballast... some a/c have unusable fuel due to the need to preserve c.of.g within limits as part of the design

p.s. savings made on individual components tend to be miniscule, but it all adds up, e.g. 0.025% here, 0.003% there... etc., as it is the components are designed with saftey factors of 1.1 or 1.2 instead of bridges etc., which are 20 or 100 in some cases.

Surya · Post by **Surya** » 08 Jun 2004 19:29

http://www.designnews.com/article/CA239990?stt=001&pubdate=09%2F09%2F02

one example

google for A380 weight reduction and you will get a lot of articles

Umrao · Post by **Umrao** » 08 Jun 2004 19:45

the wings themselves carry most of the load but are also quite flexible - very noticable on large a/c, which are designed so that the lift moves the wing into the right shape instead of being rigid and therefore extremely heavy. you just have to look at the wings of a B747 on the ground to see how much they droop at the tips, compared to how much raised they are in the air.

also notice how the wing of 747/ airbus swings while landing and take off when the wheels hit the joints of concrete slabs of the 'Landing Strip'

. they really swing and notice thet are canti lever members. Its just amazing sight.

Arun_S · Post by **Arun_S** » 09 Jun 2004 00:24

Originally posted by Daulat:
p.s. savings made on individual components tend to be miniscule, but it all adds up, e.g. 0.025% here, 0.003% there... etc., as it is the components are designed with saftey factors of 1.1 or 1.2 instead of bridges etc., which are 20 or 100 in some cases.

On medium/heavy planes every Kg of unwanted weight require 80 kg of MTOW weight (meachanical parts(wings,landing gear, fuselage etc) and fuel). On smaller plane like Saras this ratio will be more extream. Thus every Kg at design specification and syatems integration counts.

As for lighter parts, only excellence in manufacturing (& maintenence) allow optimaizing on safety margin to mechanical specs. I.e. quality & performance go together & vice versa. Throwing expensive workarounds like Titanium or composite to cover for bad design or engineering is pis$ing against the wind, it just keeping coming back.

Umrao · Post by **Umrao** » 09 Jun 2004 01:11

As for lighter parts, only excellence in manufacturing (& maintenence) allow optimaizing on safety margin to mechanical specs. I.e. quality & performance go together & vice versa. Throwing expensive workarounds like Titanium or composite to cover for bad design or engineering is pis$ing against the wind, it just keeping coming back.

Ah does anybody remember running a program or system on 640k memory? Or a mainframe job of 128k

The compactness of the software is gone with availability of hardware.

Thats what is being pointed out by arun guru.

we need good ITIs and accurate machining traditions. Till such time Kaveri will be distant mirages. Ofcourse materials technology and material composition (alloys) consistency is also a pre requiste.

shiv · Post by **shiv** » 09 Jun 2004 06:08

Originally posted by John Umrao:

we need good ITIs and accurate machining traditions..

If I may add my mantra here - we also need to understand that engineers and machinists are not caste based reserved professions with one not having to get his hands on the other's job.

I had one of my usual experiences of this yeaterday when I was walking up a staricase with a briefcase when a hospital electrician obsequiously bent forward to try and take the briefcase from my hand and carry it up because "big doctor saar" should not have to carry his own briefcase.

Umrao · Post by **Umrao** » 09 Jun 2004 06:30

If may add to Shivs message,

One of my best friend and gully (cricket mate) was a brahmin who could not efford to go to PUC after passing SSLC in state rank, he opted for ITI actually CITI ( Central institute of Industrial training opposite to Sivam near OU campus) because it offered him stipend of Rs 150 per month (in 1973 74) and stood all India first in his trade (Machinist) got presidents award , joined HMT Hyderabad in SPM division, did his LME part time, finished his BE Mech. to become shop manager (when contact was lost).

Yes, we need excellence at all walks of life however small the job may be.

ITI does not flow from the feet of Vishnu
Nor does a PH D flow from the face of Vishnu.

Should be our new Purusha sookhtam.

abhishek · Post by **abhishek** » 09 Jun 2004 06:36

HAL's new machining center

Just a n00b here, but I have been following these discussions for a few months.

I think there is no dearth of machinists, I have seen some of the best machinists in GTTC Banagalore. Since the modern 5-axis machines can machine a part of almost any measure of complexity, the problem is more of availability of these machines and less about skills.
***************
Changed handle from stranger>>>abhishek

Umrao · Post by **Umrao** » 09 Jun 2004 06:38

stranger>> please change your handle AKA name otherwise the Admins will be estranged.

***
Added later.
Then the problem of Saras is very simple. Buy more of those machines or get the same accuracy with inhouse expertise.

If you are obliquely suggesting the problem lies elsewhere then we can't solve it being a stranger to it.

SaiK · Post by **SaiK** » 09 Jun 2004 09:12

could it be TAAL's problem.. they are doing the
==
http://www.cmmacs.ernet.in/nal/pages/dr00.pdf
==
The center fuselage assembly (See Figure3) of the major modules, horizontal and vertical tail, and forward, centre and rear fuselage sections ..

Manne · Post by **Manne** » 09 Jun 2004 10:06

Better machines can help but only to an extent in proto phase. Skilled technicians using correct equipment with proper QA are required. The more accurate you are first time the better the results from an overall PoV. It is very easy to increase the weight by min. 50 grams for every weld seam if one is not careful.

Tracking weight is essential from the start and much more so in case of anything that flies and still more so for civil aviation. Given the learning curve, some slack can be cut but we should expect a lesser degree of "fat" for the next such project. While 900 kg can be reduced, it will be indeed a feat if they bring it within design specs now. Controlling the manufacturing to adhere to the drawing is an easier task than controlling the drawing to adhere to design targets. Worse yet, we may not be having sufficient data bank for fixing the design targets as we are only toddlers at the moment.

This case and future developments need to be studied by all young engineers in colleges now.

Sribabu · Post by **Sribabu** » 09 Jun 2004 14:03

Ways to reduce the weight.

a. Reduce the weight of individual components. This could be achieved by
change of material, such as replacing metalic components with lighter and stronger composites
method of manufacture, such that the manufacturing process will result in a stronger component but lighter (couldn't think of an example)
Quality control, a more stringent QC, using larger sample sizes, if not every component, will also ensure that the components are not outside the required parameters.

b. Reduce the number of components themselves. This is possible only with some experience and testing. For example, if you use 20 rivets per meter, but after testing prove that the requirements can be satisfied by using 10 rivets per meter, you have achieved reduction in weight. This is more of production engineering than design engineering.

By combing both the techniques, you need to look at sub-assemblies, integration processes etc. and change the way the production process is done.

To achieve this, there are infrastructure requirements too.
a. Automation of production to ensure the quality of the components are consistent and reduce wastage.
b. Discipline in Quality Control. The inspectors need to understand why they need the quality control. Otherwise they will only just do their job (which can lead to complacency or corruption).
c. Experience of managing the production process.

ragupta · Post by **ragupta** » 09 Jun 2004 16:10

Got this from an authoritative source who refused to be named.

This access weight is a deliberate feature during the testing phase to evaluate the stability and performance of the aircraft under these conditions.

This feature was required due to constraint of limited seating capacity in the plane, as standing passenger will need to be accomodation during feeder service to remote areas.

daulat · Post by **daulat** » 09 Jun 2004 19:15

computer stress modelling also allows components to be designed with more shavings and holes built in than before, the forces do not flow through the whole of the shape, allowing quite a bit to be cut out. now days quite complex shapes can be machined or cast at a reasonable price, unlike the old days when tooling up required quite standard parts to be produced

also, not much welding on an aircraft, aluminium has to be cast, bolted and riveted and sometimes bonded

abhishek · Post by **abhishek** » 09 Jun 2004 19:33

A link showing an example of multi-part assembly converted into a single part. It may be old for you guys...

High Speed Machining of Aerospace parts

SaiK · Post by **SaiK** » 09 Jun 2004 21:49

look how doctors are moving away from stainless steel to cobalt chromium alloys [It is the combination of cobalt, chromium and tungsten that imparts the additional strength not normally seen in stainless steel.
] for stents.. and this reports says, its 76% more stronger and much reduced thickness & halve the weight.

Will it be possible for aerospace applications too for cobalt chromium as steel replacement?

Umrao · Post by **Umrao** » 09 Jun 2004 22:13

Originally posted by pamali:
A link showing an example of multi-part assembly converted into a single part. It may be old for you guys...

High Speed Machining of Aerospace parts

That process may reduce the intermediate machining steps therby cost savings, time saving and even increase the reliability, but nowhere does it indicate weight reduction.

However one minus point in such design is field maintenance is difficult and the part cant be salvaged if its damaged (usually).

Umrao · Post by **Umrao** » 09 Jun 2004 22:18

further more

http://adg.stanford.edu/aa241/structures/structuraldesign.html

Surya · Post by **Surya** » 09 Jun 2004 22:25

John:

Tsk Tsk

Go a little deeper in the link. There is an example of weight reduction.

Machining this arch in one piece cut down its weight. The previous version of the part was assembled from as many as 20 components. The monolithic version weighs 80% less than that assembly. The arch is part of a support structure for a plane’s overhead storages bins.

Guest · Post by **Guest** » 09 Jun 2004 22:34

sweet pic of SARAS with Kiran chase-plane. (from getty images, posted by victor on afm)

http://forum.airforces.info/attachment.php?attachmentid=27014&stc=1

Umrao · Post by **Umrao** » 09 Jun 2004 22:46

Surya>> No need for tsk tsk.

It is always known even in the days Workshop Technology by Chapman or (Hajraj Chowdary) that machining a complex component from a single stock would reduce the weight and increase the relaibility.
****
In the page referred to there is no mention of weight reduction. The later pages refer to weight reduction in comparision to assmebly of components.

Surya · Post by **Surya** » 09 Jun 2004 22:53

Then maybe you should not have posted this line

"That process may reduce the intermediate machining steps therby cost savings, time saving and even increase the reliability, but nowhere does it indicate weight reduction. "

SaiK · Post by **SaiK** » 09 Jun 2004 22:54

http://www.cmmacs.ernet.in/nal/picts/divar01/cadar01.htm

- flap tracks made of maraging steel

Guest · Post by **Guest** » 09 Jun 2004 23:36

SARAS- many more flaps bfore real take-off

SARAS, the hatchling of Indian civilian aircraft industry, has tested its wings twice. Those involved with it say the indigenous light transport aircraft has many more miles and milestones to fly before it can pass the ultimate flight muster.

A high-profile official inaugural flight is said to be round the corner later this month or in early July. Until then, the entire National Aerospace Labs team led by Director, Dr B. Ramachandra Pai, is on a code of silence on anything related to the yellow twin-engine turbo-prop `bird.'

A second prototype will follow and the craft has to totally undergo a few hundred hours of flight before it can be posed to the Directorate-General of Civil Aviation for an FAR 25 (Federal Aviation Regulation) air-worthiness tag, informed sources said. "It's a 2-3-year programme," they told Business Line. It has so far done a 20-minute flight each on May 29 and June 7.
.
.
.

Sridhar · Post by **Sridhar** » 14 Jun 2004 10:25

Some routine googling led me to this article about the Saras and guess where, in People's Democracy

http://pd.cpim.org/2004/0613/06132004_snd.htm

Hold your nose while you read this article. There are errors and there is the usual praise of the Russis (or rather the Soviets), but it is still better than I thought it would be when I first saw the source of the article.

He mentions Embraer as a success story but (deliberately) keeps out the fact that it became a success story only after it was privatized.

Bhrigu · Post by **Bhrigu** » 15 Jun 2004 01:33

A very moving first person a/c of the SARAS take off

**************

From: "Srinivas Bhogle"

SARAS is a 14-seater civilian aircraft that my lab,NAL, has been working on for a long time now.

SARAS is for a 'feeder' role; i.e. 'feed' traffic for the bigger planes that take off from bigger cities. Take SARAS from Aurangabad to Mumbai, or from Coimbatore to Chennai.

SARAS can also assume other roles: air ambulance, border surveillance, cargo carrier etc.

What's hot about SARAS? We don't know yet, except that it is Indian. Well, sort of. It's got Canadian P&W engines, it's got a lot of avionics components from the US.

Many people run down such Indian efforts by saying rather cruel things like: "it's assembled", or "the Russians built such a plane 25 years ago, the Brazilians did it 10 years ago ..".

These are dumb statements. They don't understand how technology evolves. They don't understand that technology assimilation happens incrementally. Start with US LRU's today. Convert to India LRU's tomorrow (LRU = line replaceable unit).

They also don't understand that future wars will not be for fair maidens or a piece of land. But for technology. For technological strength.

The SARAS programme taught all of us at NAL to work together. Far too many R&D labs in India are lonely islands. Even though everyone realises that tomorrow's breakthroughs will not be inside domains ... but at the bridge where two domains meet.

SARAS has been very cheap to design and produce. In India we develop technologies at a fraction of the West's costs. It's our legacy to innovate with meagre resources and still cook up something very useful. For example, electronic voting machines. For example, cheap telephone exchanges where our late lamented Kuldip played no small part.

I've watched the SARAS programme evolve over 15 years. Till 1998, successive governments simply wouldn't buy this idea (till very recently, civil aviation was considered a consumer of national wealth; it only now that we recognise that it will actually create wealth).

Then Dr Murli Manohar Joshi came along with his swadeshi bias. We finally managed to sell SARAS as a swadeshi plane. We finally got Rs 135 crores in September 1999 to really start work.
Sadly the money came at the wrong time. After the nuclear tests, the US decided that NAL should come under the sanctions list (really because we support the country's missile programme).
All our foreign purchases were blocked. And rather well ... we couldn't even smuggle stuff in by subterfuge.

But NAL worked and struggled resolutely. The SARAS programme became that wonderful binding force between aerodynamics, structures, materials, flight mechanics, propulsion, composites, control .. A third of NAL's employees worked voluntarily every Saturday with a compensation package of only rava idlis or bisi bele baath. This has gone on for five years now.

We involved the local private manufacturing industry, we borrowed expertise from retired aircraft designers, we roped in the Indian Air Force for flight testing, we endured barbs and snide remarks from the media. Our chief designer's tablet intake crossed 20 a day. But we didn't give up.

When the SARAS 'rolled out' last year we exulted (rolling out merely involves towing the fully-assembled aircraft out of its hangar for the first time -- no big deal actually). When the SARAS low speed taxi trials started in March 2004, the excitement grew. April-May 2004 involved high speed taxi trials (attaining speeds up to 90 knots; SARAS can take off at 105 knots -- 1 knot is approx 2.2 km) terminating with the exciting 'nose up' manoeuvre.

Suddenly on 26 May, the Chief of Air Staff announced at a press conference that the SARAS would fly on 28 May at 8.10 in the morning. This was jumping the gun in a big way and we weren't amused. No one makes public announcements of what should be hush-hush first flights! But there wasn't much we could do. Especially because the Chief also promised to buy six SARAS aircraft for the IAF! (that was great of him, who promises to buy a plane that still hasn't flown?)

Bad weather -- remember the monsoon has set in early this year? -- meant that 28 May was no go. But 29 May seemed on.

On 28 May, I walked into an IAF committee room for the pilot's final briefing. I was enthralled by Sqn Ldr K K Venugopal's presentation. For one hour he laid out bare the first flight plan. Every contingency was discussed (including "a/c becomes u/s" which means the aircraft goes unserviceable, the mission fails -- and Venugopal probably dies!). My admiration for the young dashing pilot grew phenomenally. I also felt personally very small. This kid was probably born when I was in B1. How -- and why -- was my life going on without any comparable achievement?

Finally it was 29 May. Today could be the big day!
During my morning walk I decided that the clouds looked rather menacing. All this only added to the anxiety. "No breakfast till the SARAS flies", I told my wife as I drove off at 6.35 a.m. to witness the first flight (she seemed quite happy to hear this!).

At the tarmac, there was an icy silence. The sun was weakly peeping through the clouds as Sqn Ldr Venugopal and his co-pilot Wg Cdr R S Makker (a Sardar) did the preliminary checks on the control surfaces. All of us were pretending to be relaxed but the tension was palpable. It didn't help that a heavy wind was building up on our backs.
"High cross winds not good", the other watching IAF pilots muttered. As the pilots boarded the aircraft for the final cockpit checks, I joined my colleagues on the terrace of the telemetry tower. We saw the two 'chase' aircraft taxiing out, we saw and heard the SARAS engines roar alive and soon the SARAS itself began to taxi out.

The airport went out of bounds for civil aircraft at 8.00. At 8.10 the first chase aircraft took off noisily (to also clear the airspace of birds) and the second chase aircraft followed two minutes later.
Far away to the right we began to see the SARAS rolling. "Rolling now", I heard Venugopal saying on the radio. A rapidly accelerating SARAS was now sweeping into view. The nose was lifted .. and seconds later, our beautiful bird was airborne!
I can't describe my most satisfying sense of elation. I started clapping, everyone else was clapping .. as the SARAS climbed higher, our clapping attained a new crescendo. This was the sound of a new, proud and shining India. We built our plane and, look, we're bloody well flying it!

As the SARAS disappeared into the clouds, I climbed down back to the tarmac to await its landing. On the way down, I sneaked into the command nerve centre where the flight director was viewing digital displays and advising the pilots on radio. An IAF orderly signalled that I mustn't enter and disturb. I had no intention of doing so. I just wanted to check the body language to bere-assured that all was well.

At 8.44, the two chase aircraft became visible. A single speck of light was visible between these two aircraft. This was SARAS coming in to land. At 8.45, SARAS landed safely to a tumultuous ovation.

All of us lined up on the runway to cheer the pilots. A Tricolour appeared from nowhere and was lustily waved. Sqn Ldr Venugopal's Commandant Air Commodore Chopra was waiting to greet his brave pilot.
Venu saluted his Commandant smartly before receiving a hug.

It was wonderfully euphoric. Everyone was shouting, cheering and hugging. An IAF waiter emerged with two bottles of champagne. As the corks popped out, Venu said: "we seem to have a great flying machine.
I am not worried about our competition; I think our competition must worry about us now!".

I kept marvelling at Venu. Is this chap human, I wondered. Till I saw a tall and pretty young lady walk up to him and hand over a brat of a kid. This was Venugopal's two-year old in tears -- probably crying because he had been denied his appa. But then I saw the appa's eyes, and they were moist too. The SARAS wasn't going to separate the father from his dear son after all!

Rudra · Post by **Rudra** » 15 Jun 2004 01:39

A third of NAL's employees worked voluntarily every Saturday with a compensation package of only rava idlis or bisi bele baath. This has gone on for five years now.

> ususual to find under govt sector. hope NAL, HAL, ADA, DRDO get put under separate payscales like iit-profs.

Umrao · Post by **Umrao** » 15 Jun 2004 01:47

simply goose bumps.

Great work.

Ashutosh · Post by **Ashutosh** » 15 Jun 2004 01:53

Good job. However they need to find out that they've missed the bus. They need to cannabilize the project and distribute the money amongst the CPIM politburo members who will eventually distribute it amongst the bhadralok. Time we all woke up and started reading people's democracy by the communist party.

abhishek · Post by **abhishek** » 15 Jun 2004 02:23

hope NAL, HAL, ADA, DRDO get put under separate payscales like iit-profs

I totally agree with this, I also assume you mean to include numerous other research organizations like Plasma research institute, ISI, TIFR etc etc.

For other second grade institutes the Ministry of HR should provide some cash award for every technical paper published in an international reputed journal.

shiv · Post by **shiv** » 15 Jun 2004 05:59

Originally posted by Harish:

We built our plane and, look, we're bloody well flying it!

manju · Post by **manju** » 15 Jun 2004 09:21

SELF DELETED AS IT WAS POSTED BY HARISH

Manne · Post by **Manne** » 15 Jun 2004 09:41

Harish,

Thank you for sharing that with us. Indeeed very moving and motivating.

Good show NAL and others.

JTull · Post by **JTull** » 15 Jun 2004 10:38

Great account of the effort. NAL has been quite open and it's webpage is also more professional than, say ADA. It is interesting that M M Joshi was the one to get this project going.