ADA Tejas (LCA) News and Discussions

[Kunal Biswas]

Manufacturing And Certification Of Composite Structures - Issues And Challenges [Aero India 2013]



uploaded by Luptonga.

 

[ersakthivel]

 

[myana]

In very layman terms if i want to make a prototype of a shoe i will hand cut leather,glue the leather by hand and also polish the shoe by hand.

If the prototype model is accepted and requested in large quantities i would setup a large automated systems with lot of money to mass produce the shoe. This will make manufacturing faster and error proof.

Now if the quantity to too low why would i invest such large amount of money in setting up the all cnc machines for manufacturing and make my product expensive.

Now HAL is ready to setup this system but wants a large firm order for its users(IAF) in order to make the automation feasible and practical.

Dassault are making composite structures through automated process because they have a firm order of 286 plane from their own air force so it is feasible and practical for them.

On the otherhand how many planes in IAF manufactured by HAL require carbon composites "None" now carbon composites are being used in Tejas and there are proposed plans to use them SU 30 MKI(cannards and skin not sure how far ahead they are with those proposal i think they were part of super sukhoi programme). What ever Tejas are built so far are prototype and LSPs all are hand made. If HAL has firm large order it is practical to make the manufacturing automated and in turn to place order for subsystems.

 

[myana]

Adding to above comment
Aircraft Division Bangalore
the above link talks about the manufacturing of hawk trainers manufactured at bangalore Hal(brief history section) and look at all the cnc machines and tools used(facilities section) they had setup all these because they had a firm order of 66+57

 

[ersakthivel]

http://ftp.rta.nato.int/public//PubFulltext/RTO/EN/RTO-EN-004///$EN-004-19.pdf
"for wing sweep angles above 60 deg the flow features are dominant concentrated vortical flows at low speeds, and swept shocks with vortex separation at high speeds."


" A dominant increase in drag at supersonic speed is due to wave drag component consisting of lifting surfaces, fuselage, interference drag(collectively know as drag due to volume),.

At lifting conditions ,Lift dependent wave drag produces further contributions. At subsonic and trans sonic speeds the lift dependent drag varies inversely with the square of the wing span. So maximizing wing span is desirable for manoeuvrability of the fighter.


At super sonic speeds the lift dependent drag varies with longitudinal area of distribution

Typically the wing contribution to zero lift wave drag is 25 percent .
.

So the wing area contributes only 25 percent to wave drag, (which is zero lift in nature).

So the component of zero lift wave drag that is going to vary for high wing loading and low wing loading fighter is just 25 percent variation only.

While high wing loading (low wing area fighter) have less than twenty five percent drag at the maximum , it will suffer more in losing the lift component of low wing loading fighter which is directly dependent on wing area.

in other words as far as wave drag is concerned the higher wing area imposes less of a penalty on low wing loading fighters compared to the lift component it gives.

http://www.smtp.brendakulfan.com/docs/sfp2.pdf

 

[ersakthivel]

An Error Occurred Setting Your User Cookie
http://www.dept.aoe.vt.edu/~mason/Mason_f/ABMSThes.pdf
https://www.google.co.in/search?q=w...=RsMSVeekIciTuATdq4KAAQ&ved=0CAUQ_AUoAA&dpr=1

 

[Kunal Biswas]

Composite Components in MK1

 

[Kunal Biswas]

Chindits: India's BVR Air-to-Air Missile 'ASTRA' Successfully Test Fired

[tweet]578521265515823105[/tweet]

[tweet]578522557894164481[/tweet]

 

[akshay m]

nileshjr of bharathrakshak said this,, i copied it from there

I am looking through NAL archieves and there seems to be a trail of papers related to delta wing configuration studies right from early 70's or so. Pity the material is not accessible for mango people. (

This one for example, seems to be connected to the study of effect of Canards with LCA wing. For the said configuration at least its seen that Canards are more detrimental than helpful.

Narayan, KY (1988) Effect of Canard on the Characteristics of a 65° Delta Wing-A Preliminary Analysis of Experimental Data. Project Report. National Aerospace Laboratories, Bangalore.

The experimental data available on a 65° swept-back, cropped delta wing with a canard has been analysed to study the effects of canard. Two sets of results are available : the first set is with a wing having sharp leading edges and the second set with a wing having rounded' leading edges. The tests were carried out at Mach numbers of 0.4 and 0.85 (Reynolds - number of 9.106 based on wing root chore) for the first set and at 0.5, 0.7, 0.85 and 1.2 (Reynolds number of 4.5.10^6 based on wing root chord) for the second set. The main effect of the canard is to delay leading edge separation in the forward part of the rounded leading edge wing. In the case of the sharp leading edge wing, although earlier measurements have shown that the canard is able to suppress leading edge separation, there is no direct evidence of this in the present measurements. However, the results do show a significant weakening of the wing vortex in the presence of the canard.

nileshjr

And finally I found something which talks about the lower-swept in-board part of Compound delta wing, though I can find only the abstract.

Sajeer, Ahmed and Sudhakar, S (2010) Experimental Study on Pitch up Problem Associated with Compound Delta Wings of Combat Aircraft Configurations. Project Report. National Aerospace Laboratories, Bangalore.

Experiments were carried out on two compound delta wing configuration with first sweep angle of 50°& 55° and a second sweep of 60° in the 0.3m Trisonic wind tunnel for a Mach number range of 0.5 to 0.85 in the angle of incidence range 0° to 20°. Data was also generated for a baseline delta wing configuration with sweep angle of 60°. The results were analyzed to understand the effect of variation in first sweep and Mach number for the existence of pitch up. Oil flow visualization has been carried out for the limited case to infer the flow field associated with the pitch up. Analysis of the aerodynamic data showed the presence of pitch up in all the three configuration tested. Decrease in first sweep has shown an increase in the magnitudes of the pitching moment and occurrence of pitch up shifting to lower incidence angles. Increase in Mach number has shown similar variation and no pitch up was observed at Mach number of 0.85 for the configuration having compound sweep of 50°/60°. Surface flow patterns supplements the force data and indicates the flow pattern over the wing is affected by first sweep and is predominantly dominated by a vortex from the first sweep and considerable difference in flow pattern is observed over the area covered by the first sweep compared to single 60° delta configuration.

 

[ersakthivel]

Thats one of the reason ADA never considered canards on tejas. The aim of their lower swept inboard , notched Wing leading edge was generating a huge vortex flow that extends outwards on the whole wing area in lower AOA there by energizing the air flow over entire part of wing, with pitch up movement provided as well.

there are no complex interplay of canard-wing vortices at different AOAs and no canard wash affecting air flow over wing.In this configuration,there is no problem of vortex flipping over wings across non lift generating fuselage in high AOAs . because the notch in lower swept delta wing leading edge drives the vortices out wards towards the middle and outer part of the wing.(but canard and LREX vortex passes close to the fuselage and may some time flip over to the fuselage instead of upper wing in high AOAs, there by the potential lift inducing vortex benefits getting lost at very high AOAs.)

Also the tejas wings are not mid fuselage mounted like that of canard deltas. The wings in tejas attach almost to the top of the fuselage with much smoother wing upper fuselage blending. SO I don't think ther is enough vertical gap available for canard positioning on tejas. In gripen , rafale and EF wings attach to mid fuselage.

the aim of canards is also vortex generation and pitch up movement .

So the aim of tejas lesser swept notched inboard wing leading edge is to spread the vortex outwards and avoid it flipping over the wings onto fuselage (all lift benefits are lost ) in high AOA. this is the main advantage of vortex generated by tejas wing over the LREX or smaller canards .

In LREX the vortex is closer to fuselage and may flip over the wings onto fuselage at higher AOAs. In tejas this problem does not arises.

http://ftp.rta.nato.int/public//PubFulltext/RTO/EN/RTO-EN-004///$EN-004-19.pdf

for wing sweep angles above 60 deg the flow features are dominant concentrated vortical flows at low speeds, and swept shocks with vortex separation at high speeds."

So this statement from the technical paper also attest to the fact of strong concentrated vortical flows even in low speeds for the highly swept (60 deg plus) outboard wing leading edge of tejas, which gets reinforced by the vortices from lower swept notched inboard lesser swept wing leading edge of tejas 's compound delta planform.

this image clearly shows the notch in lesser swept wing leading edge spreading the voritcal flows to out wards towards the whole wing area opposed to canards and LREX where vortex leans towards the fuselage,

 

[akshay m]

 

[ersakthivel]

http://s19.postimg.org/leivya75f/LCASAERODYANAMICS1.jpg
View image: LCASSENSORSUITE1
View image: LCASSTRUCTUREMATERIALWEIGHTREDUCTIONSTEALTH1

 

[akshay m]

Thats one of the reason ADA never considered canards on tejas. The aim of their lower swept inboard , notched Wing leading edge was generating a huge vortex flow that extends outwards on the whole wing area in lower AOA there by energizing the air flow over entire part of wing, with pitch up movement provided as well.

..................................................................

SO much for prasun sengupta and his front wheel driving

now he is proved to be nothing but a bag of gas


again the problem in tis country is that those who should speak are silent and those who shouldn't ,shreik

 

[ersakthivel]

Approach to High Angle of Attack Testing of Light Combat Aircraft [LCA] Tejas

The lesser swept wing leading edge angle is 50 deg for tejas,

It consists of a pure double delta configuration with leading edge angles of 50 deg and 62.5 deg and a trailing edge forward sweep angle of 4 deg . The CG lies about 33.5% of MACand the wing area is 38.5 sq meter.

In F-16 Xl also the leading edge wing sweep angle was 50 deg as per the following link.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.51.2771&rep=rep1&type=pdf

The derivative configuration showed the potential for increased sustained-g maneuvering capability in relation to the F-16C model because of the
improved lift/drag; the derivative configuration also maintained comparable lateral-directional stability.

The F-16C configuration has a higher lift-curve slope and a lower lift-dependent drag coefficient (i.e., CD CDmin) mainly because of its lower wing sweep
and higher aspect ratio. Minimum drag coefficient for the baseline configuration is lower than for the F-16C model, osetting the lower lift and higher liftdependent
drag coeffecients to give the baseline configuration a substantially higher lift-drag ratio than the F-16C model for CL < 0:4. As mentioned previously,each set of data was referenced on its own wing reference area. The F-16C model has other lifting surfaces (i.e., horizontal tails, fore body, and shelf areas) that are not included in the reference area. If the data were reduced about a weighted planform area reference for each conguration, the magnitudes of lift-curve slope and drag dierences discussed above would likely be smaller characteristics.

what is being referred here as baseline configuration is F-16 XL

The data reduced with the common reference geometry show that the F-16C configuration now has a lower lift curve slope and higher lift-dependent drag coecient
(i.e., CD CDmin) relative to the baseline configuration.Although the baseline conguration has a higher minimum drag coeffecient than that of the F-16C because of skin friction associated with the larger wing and shelf area, it generates greater lift and L=D than the F-16C for CL > 0:15 for M = 1:60



The lift, pitching moment, and lift-dependent drag characteristics of the two congurations at the tested Mach numbers are compared in gure 35. A translation of
lift curves is evident there, as well as a zero-lift pitching-moment shift between the two models that is likely attributable to the wing twist and body
camber dierences.

The baseline conguration exhibits slightly higher lift-curve slopes and slightly more stable pitching-moment characteristics than does the generic wing model. The lift-dependent drag curves show little difference between the congurations at M = 1:60; however, at higher Mach numbers the baseline conguration shows lower untrimmed lift-dependent drag than the generic wing model.


Trimmed comparisons. The trimmed aerodynamic characteristics for the baseline conguration and the generic wing model are shown in gure 36.
The baseline conguration exhibited higher trimmed lift-dependent drag because of the larger pitching moment increment required to trim at a given lift
condition. A larger trailing-edge ap de ection was required for the baseline conguration not only to counter the larger pitching moment, but also to compensate
for the baseline model having a 10-percent smaller ratio of trailing-edge ap area to wing area than the other model

http://www.scribd.com/doc/78345390/...ing-of-Light-Combat-Aircraft-LCA-Tejas#scribd

The Tejas LCA has been designed to be aerodynamically unstable in the longitudinal axis to obtain improved maneuverability and agility over the entire flight envelope and hence, has to be stabilized artificially by the use of active control technology.

The region from 0.5M to 0.7M and from 3Km to 8 Km is the zone of the highest instability with time to double amplitude dropping to 200 milli secs. This implies that an ydisturbance in pitch would cause an increase in amplitude by 32 times in a sec.

Does this mean tejas is unstable even in supersonic flight?

All other fighters like typhoon return to stable flight profile in supersonic flight.

Cl max continues to improve till 35 deg AOA.

directional characteristics indicated the proverbial 'cliff' with a sudden drop in Cnp ,, CRM (Coefficient of Rolling Moment) and CYM (Coefficient of Yawing Moment) at approx 25 deg AoA as shown at fig-4 and 5. These phenomena require the High AoA trials to be limited to 24 deg (as shown in dotted line) until directional stability is bolstered and augmented by rudder control up to an expected 26 deg . Currently the Tejas is flying to AoA limits of 20 deg and 22 deg never exceed. Fortunately as shown in fig-6, the LCA hassignificant rudder authority (CYM-Del R) even up to 30
exceeded(now it has gone higher than 26 deg.)

Fortunately as shown in fig-6, the LCA has significant rudder authority (CYM-Del R) even up to 30 deg AoA that will allow artificial stabilization in yaw at high AoA
AoA

 

[Khagesh]

A few self explanatory notes on the effect of wing sweeps in compound deltas, from designers and pilots:

https://www.scribd.com/doc/206943112/Harry-Hillaker-Father-of-the-F16

https://www.scribd . com/doc/206943112/Harry-Hillaker-Father-of-the-F16

Boyd and Sprey would later admonish you for not sticking to the fighter mafia's original intent summed up by the group's motto "make it simple." They fault the aircraft for getting heavy and overloaded with gadgetry. What is your response?

If we had stayed with the original lightweight fighter concept, that is, a simple day fighter, we would have produced only 300 F-16s, the same number of F-104s that were built. This is not to say that their complaints are unreasonable. When you load up an F-16 with external fuel tanks, bombs, and an electronic countermeasures pod on the centerline, you've doubled its drag. For someone who's worked all his life to achieve minimum drag, that's sacrilegious. Nonetheless, it speaks well for the airplane. The F -16 has far exceeded my expectations. However, if I had realized at the time that the airplane would have been used as a multimission, primarily an air-to-surface airplane as it is used now, I would have designed it differently.



Is this difference represented by the F-16XL?

Yes. The F-16XL had a better balance of air-to-air and air-to-ground capability. In fact, when I first started going to the Air Force with plans for the F-16XL, some of the Air Force people were so enthusiastic about it that they accused me of holding the design back so that we could sell the airplane twice. If you know anything about the history of the lightweight fighter, you know that this was not the case.

With the F-16XL, we reduced the drag of the weapon carriage by sixty-three percent. The drag of the XL with the same fuel and twice as many bombs is a little over thirty percent less than today's F-16 when you load it up. This points up a fallacy that has existed for thirty years, and I'm concerned that it may still exist. Our designs assume clean airplanes. Bombs and all the other crap are added on as an afterthought. These add-ons not only increase drag but they also ruin the handling qualities. They should be considered from the beginning. We ought to start with the weapon. That's really the final product.

We ought to determine what the weapon is and what it will take to deliver it and then do the airplane. Now, we design the airplane and smash the weapon on it.

 

[salute]

 

[ersakthivel]

India's Combat Aircraft Programmes: Learnings From Past | Swarajya
Aeronautics - The four forces of flight (AIRSPEED, CAMBER, AND LIFT) - Level 2

 

[sgarg]

India's Combat Aircraft Programmes: Learnings From Past | Swarajya
Aeronautics - The four forces of flight (AIRSPEED, CAMBER, AND LIFT) - Level 2

Great job @ersakthivel. The only way to dispel ignorance is to shine a light.

 

[Pulkit]

Great job @ersakthivel. The only way to dispel ignorance is to shine a light.

India's Combat Aircraft Programmes: Learnings From Past | Swarajya
Aeronautics - The four forces of flight (AIRSPEED, CAMBER, AND LIFT) - Level 2

guys I went through these articles twice but did not understand.
can any one of u dumb it down for me to understand.
Layman plz

 

[sjmaverick]

Of all the images i have seen for this mean machine i find this to be most close to its name...its protected by the publisher and i am not able to post the link. Found another way out to still put it here:

.photoyogi.com/Aviation-Photography/Tejas-LCA-1/i-qrDR8jw/X3