Bharat Rakshak

Consortium of Indian Defence Websites
It is currently 29 Aug 2014 08:16

All times are UTC + 5:30 hours




Post new topic This topic is locked, you cannot edit posts or make further replies.  [ 4018 posts ]  Go to page Previous  1 ... 73, 74, 75, 76, 77, 78, 79 ... 101  Next
Author Message
PostPosted: 16 Feb 2012 02:35 
Offline
BRFite

Joined: 06 Mar 2001 12:31
Posts: 216
Location: Niyar kampootar onlee
indranilroy wrote:
Raghu,

I had a long pending question about the LCA. I would be very grateful if you or your ex-roommate could answer it. Obviously avoid replying if the answer is classified in any manner.

Observation:
While there is beautiful blending of the wing with the fuselage on the upper side, the lower side of the wing is completely at right angles to the body. The MK II models displayed at AI-11 did not show any lower-wing-body blending.

The advantages of the wing body blending with respect to lower drag and RCS is well known. Also the wing body blending should provide space for the main landing gear and hence free up more internal space.

Question:
Is the lower wing body blending being avoided in order to stick to timelines or is there some aerodynamic/structural reason(s)?


indranilroy,

First, In all wings, flow over the upper surface is much more critical than the lower surface. This is the reason why you can suspend pylons, weapons, fuel tanks, engine mounts, etc. on the bottom of the wings and yet not affect the essential lift capability of the wing. The wing-body blending on the upper surface essentially creates a larger upper wing surface for lift to act. This is not critical on the lower surface.

Second, while blending in the lower surface may marginally reduce interference drag it will either (a) increase the cross-sectional area in the fuselage section where cross sectional area is very critical (i.e., wing-fuselage junction) thereby increasing wave drag and hampering trans/supersonic performance, or (b) if the fuselage is tapered to maintain the same cross sectional area, reduce the volume available in the fuselage, which is a critical commodity in a small aircraft.

My guess is that the designers concluded that the tradeoff wasn't worth it.


Top
 Profile  
 
PostPosted: 16 Feb 2012 04:28 
Offline
Forum Moderator

Joined: 02 Apr 2010 01:21
Posts: 2842
I like your answer :). My answers inline (in blue).
Raman wrote:
indranilroy wrote:
Raghu,

I had a long pending question about the LCA. I would be very grateful if you or your ex-roommate could answer it. Obviously avoid replying if the answer is classified in any manner.

Observation:
While there is beautiful blending of the wing with the fuselage on the upper side, the lower side of the wing is completely at right angles to the body. The MK II models displayed at AI-11 did not show any lower-wing-body blending.

The advantages of the wing body blending with respect to lower drag and RCS is well known. Also the wing body blending should provide space for the main landing gear and hence free up more internal space.

Question:
Is the lower wing body blending being avoided in order to stick to timelines or is there some aerodynamic/structural reason(s)?


indranilroy,

First, In all wings, flow over the upper surface is much more critical than the lower surface. This is the reason why you can suspend pylons, weapons, fuel tanks, engine mounts, etc. on the bottom of the wings and yet not affect the essential lift capability of the wing. The wing-body blending on the upper surface essentially creates a larger upper wing surface for lift to act. This is not critical on the lower surface.
This is beyond the point. On the question of lift coefficient of the wing, I can simply ask the question. Does adding a smoothening adversely affect lift coefficient? For most aircrafts it doesn't. However for LCA it is interesting as the wing root itself has a huge twist. after making this observation, one might say, why not a symmetrically twisted smoothening?


Second, while blending in the lower surface may marginally reduce interference drag it will either (a) increase the cross-sectional area in the fuselage section where cross sectional area is very critical (i.e., wing-fuselage junction) thereby increasing wave drag and hampering trans/supersonic performance, or (b) if the fuselage is tapered to maintain the same cross sectional area, reduce the volume available in the fuselage, which is a critical commodity in a small aircraft.

My guess is that the designers concluded that the tradeoff wasn't worth it.
You mean that the critical mach number for the plane would be lowered. But by how much? The wing body blend is essentially very smooth! By carefully choosing the wing body blend one could maintain a very smooth curve for the area curve, thus minimizing wave drag. There is no need of narrowing the fuselage. I had seen area curve of LCA, it is very smooth along the chord of the wing. There are steep rises before the wing and after the wing, which they are working on smoothening.

Also correct me if I am wrong here. the tradeoff between interference drag and wave drag has been well settled in favour of having a blended wing? This is the basis of the all blended wing designs from the Junkers G.38 to the X-48 and Be-2500 etc. and fourth generation planes except EF



Anyways, it is nice discussion. As an aerodynamics enthusiast, I would love to know why certain choices were made. Probably that would not happen in public space. Will have to befriend some LCA guys or get employed there! Problem is why would they hire me :|


Top
 Profile  
 
PostPosted: 16 Feb 2012 23:08 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
Flight test update

LCA-Tejas has completed 1778 Test Flights successfully. (14-Feb-2012).
(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-67,LSP2-198,PV5-36,LSP3-46,LSP4-44,LSP5-65)

from

LCA-Tejas has completed 1777 Test Flights successfully. (10-Feb-2012).
(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-67,LSP2-198,PV5-36,LSP3-46,LSP4-44,LSP5-64)


Top
 Profile  
 
PostPosted: 17 Feb 2012 00:38 
Offline
BRFite

Joined: 06 Mar 2001 12:31
Posts: 216
Location: Niyar kampootar onlee
indranilroy,

Quote:
Does adding a smoothening adversely affect lift coefficient? For most aircrafts it doesn't. However for LCA it is interesting as the wing root itself has a huge twist. after making this observation, one might say, why not a symmetrically twisted smoothening?


I think you are talking about different things in the same breath.

First: Does "smoothening" the lower surface affect lift coefficient? Yes, anything that affects the airfoil profile will affect the lift coefficient. Second: Does it *adversely* affect lift coefficient? Probably. You are essentially tending towards a symmetric airfoil, which have lower lift coefficients than cambered airfoils for a given angle-of-attack.
Third: LCA wing has a huge "twist" at the root. Yes. This is for two reasons: first to ensure that the entire wing doesn't stall at once. Second, a lot of that "twist" at the root is to control the oblique shocks for the inlet to operate at supersonic speeds.

The issue I was trying to highlight in my first statement is that there are good reasons to wing-body blend the upper surface; not so for the lower surface.

Quote:
You mean that the critical mach number for the plane would be lowered. But by how much? The wing body blend is essentially very smooth! By carefully choosing the wing body blend one could maintain a very smooth curve for the area curve, thus minimizing wave drag. There is no need of narrowing the fuselage. I had seen area curve of LCA, it is very smooth along the chord of the wing. There are steep rises before the wing and after the wing, which they are working on smoothening.

Also correct me if I am wrong here. the tradeoff between interference drag and wave drag has been well settled in favour of having a blended wing? This is the basis of the all blended wing designs from the Junkers G.38 to the X-48 and Be-2500 etc. and fourth generation planes except EF


I was not referring to critical mach at all. The point is blending the lower surface will increase the cross sectional area of the airplane. Increasing/decreasing the cross sectional area smoothly is not enough. I think this is the point you are missing. The CS area distribution must match the Sears-Haack distribution closely to minimize wave drag. Just blending without paying attention to the Sears-Haack distribution will increase wave drag unless the fuselage volume is correspondingly reduced, which we cannot do for reasons of packaging/estate management.


Top
 Profile  
 
PostPosted: 17 Feb 2012 03:28 
Offline
Forum Moderator

Joined: 02 Apr 2010 01:21
Posts: 2842
Raman sir, probably you are right!

You are right ... if we have to retain the sharp edge of the leading edge of the wing and trailing edge of the supersonic wing, then the smoothening will be a bulge and that will lower the camber and hence the CL. That is a good point.

I remember the wonderful discussion of the LCA wing a couple of years back. So I do understand the basics and reasons behinds its shape. I was very interested to know ... I thought some of the posts there should have been made sticky :D.

Coming now to the tradeoff between the wave drag and the interference drag. I will try to dig up the area curve of LCA Tejas (Kartik could you help me find the pdf which discussed the planned refinements in LCA) ... may be we can do some back of the envelop calculations for increase in wave drag ... Alas we can't do anything to find the approximate decrease in interference drag.

Once again it was a good discussion for me :)


Top
 Profile  
 
PostPosted: 17 Feb 2012 04:03 
Offline
Forum Moderator

Joined: 02 Apr 2010 01:21
Posts: 2842
Okay found the paper which had the area curve: http://www.drdo.gov.in/drdo/pub/dss/200 ... EMILAC.pdf (pg. 9).

Question is whether it is acceptable to increase the area between stations 6 to 11 or so?

Most probably they would have done CFD analysis and found that it is not! Ah, but the itch to know ...


Top
 Profile  
 
PostPosted: 17 Feb 2012 10:20 
Offline
BRFite -Trainee

Joined: 16 Feb 2012 18:40
Posts: 6
Hi All,
This is my first post although I have been lurking on BR for almost 11 years.
Am SDRE IT guy from Bangalore.

Yesterday around 2 pm show LCA with IFR probe. Are there any of them LSP or PV flying with IFR attached? Or was it LSP 6/7


Top
 Profile  
 
PostPosted: 17 Feb 2012 10:28 
Offline
BRF Oldie

Joined: 05 Apr 2006 16:25
Posts: 6648
Flight Test News


LCA-Tejas has completed 1779 Test Flights successfully. (16-Feb-2012).

(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-67,LSP2-198,PV5-36,LSP3-46,LSP4-45,LSP5-65)


LCA-Tejas has completed 1778 Test Flights successfully. (14-Feb-2012).

(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-67,LSP2-198,PV5-36,LSP3-46,LSP4-44,LSP5-65)

Based on ADA website no LSP6/7 in the Air, only 1 flight in the last 2 days.


Last edited by Aditya_V on 17 Feb 2012 11:26, edited 1 time in total.

Top
 Profile  
 
PostPosted: 17 Feb 2012 10:52 
Offline
BRF Oldie

Joined: 01 Jan 2010 21:41
Posts: 7251
AV, would be nicer for the sake of continuity to use suryag's last post. His update was for Feb 14?


Top
 Profile  
 
PostPosted: 17 Feb 2012 11:24 
Offline
BRF Oldie

Joined: 05 Apr 2006 16:25
Posts: 6648
Ok, Sorry copy posted from ADA website. Corrected my post, continuing from Suryag's post


Top
 Profile  
 
PostPosted: 18 Feb 2012 02:05 
Offline
BRFite

Joined: 26 Jun 2005 10:26
Posts: 1360
Location: Atop Orthanc, cursing, "Damn it where are those backfires??"
ketan.sojitra wrote:
Hi All,
This is my first post although I have been lurking on BR for almost 11 years.
Am SDRE IT guy from Bangalore.

Yesterday around 2 pm show LCA with IFR probe. Are there any of them LSP or PV flying with IFR attached? Or was it LSP 6/7


Very, very interesting Ketan, welcome to the board - you come bearing good/interesting news. Can any jingos with inside clearances to sensitive areas such as golf courses or roof tops confirm this development?

CM


Top
 Profile  
 
PostPosted: 18 Feb 2012 02:41 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
[wetdreams] was it PV2?, it seems to have flown after a long time (after two months)[/wetdreams]


Top
 Profile  
 
PostPosted: 18 Feb 2012 02:48 
Offline
BRF Oldie

Joined: 02 Dec 2008 10:49
Posts: 4789
ketan.sojitra wrote:
Yesterday around 2 pm show LCA with IFR probe. Are there any of them LSP or PV flying with IFR attached? Or was it LSP 6/7

Are you sure it was an LCA? Some fighter jets are difficult to distinguish from afar. A M2000 for e.g. can easily be confused with an LCA if you catch only a quick glimpse or if it's too far away. A M2000 would be a rare sight in BLR though.


Top
 Profile  
 
PostPosted: 18 Feb 2012 08:31 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
SBTF update from tarmak

Quote:
While the SBTF work is probably ahead of the schedule, sources say that the eagerly-awaited first flight of NLCA (Naval Prototype NP-1) is on course. The platform is said to have undergone a trial for nose-wheel checks (70 km) on Valentine’s Day, while a LSTT (low-speed taxi trial) at a possible max speed of 140 km/hour is scheduled for February 18. This would be followed by a HSTT (high-speed taxi trial) at a maximum speed of 200-200 km/hour and then the subsequent first flight.


Top
 Profile  
 
PostPosted: 18 Feb 2012 09:06 
Offline
Forum Moderator

Joined: 13 Aug 2004 19:42
Posts: 32598
Location: Col of the regiment, ORR JTF unit
in 7 yrs the only time I have never seen M2K in HAL. did see MKI few times flying into HAL for events like AI09.


Top
 Profile  
 
PostPosted: 18 Feb 2012 10:31 
Offline
BRF Oldie

Joined: 01 Jan 1970 05:30
Posts: 2059
Location: NullPointerException
So lets see what is the sequence of events for an LCA new bird to fly

1. Fabrication
2. Roll out
3. SCT, vibration and other tests
4. Engine Ground Run (EGR)
5. Nose wheel checks (at 70 kmph per above report)
6. Low speed taxi trials (at 140 kmph per above report)
7. High speed taxi trials (at 200-220 kmph per above report)
8. Rotation tests?
9. First flight


Top
 Profile  
 
PostPosted: 18 Feb 2012 10:44 
Offline
BRFite

Joined: 01 Jan 1970 05:30
Posts: 312
Singha wrote:
in 7 yrs the only time I have never seen M2K in HAL............


"They" don't fly, they are for some sort of "research purposes" onlee.


Top
 Profile  
 
PostPosted: 18 Feb 2012 11:55 
Offline
BRF Oldie

Joined: 01 Jan 2010 21:41
Posts: 7251
George J wrote:
Singha wrote:
in 7 yrs the only time I have never seen M2K in HAL............


"They" don't fly, they are for some sort of "research purposes" onlee.


Had earlier posted about seeing a pilot from Sq 1 (Tigers) during AI. Don't recollect seeing M2Ks flying then tho.


Top
 Profile  
 
PostPosted: 18 Feb 2012 12:59 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
Flight test update

LCA-Tejas has completed 1780 Test Flights successfully. (17-Feb-2012).
(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-68,LSP2-198,PV5-36,LSP3-46,LSP4-45,LSP5-65)

from

LCA-Tejas has completed 1779 Test Flights successfully. (16-Feb-2012).
(TD1-233,TD2-305,PV1-242,PV2-212,PV3-330,LSP1-67,LSP2-198,PV5-36,LSP3-46,LSP4-45,LSP5-65)

Someday i would like to know what group of aircraft was used for what kind of flight testing


Top
 Profile  
 
PostPosted: 18 Feb 2012 14:44 
Offline
BRFite -Trainee

Joined: 12 May 2010 02:23
Posts: 74
So Boeing is planning to make about 10 Dreamliners a month by Q4 2013, scaling up from its current 2.5 a month . Meanwhile, HAL is going to make about 10 a year ramping up from Zero all of last year.... just saying.

http://online.wsj.com/article/BT-CO-201 ... 01263.html


Top
 Profile  
 
PostPosted: 18 Feb 2012 14:54 
Offline
BRFite

Joined: 12 Jun 2010 23:06
Posts: 240
Location: look behind you
Quote:
So Boeing is planning to make about 10 Dreamliners a month by Q4 2013, scaling up from its current 2.5 a month . Meanwhile, HAL is going to make about 10 a year ramping up from Zero all of last year.... just saying.

http://online.wsj.com/article/BT-CO-201 ... 01263.html


you shouldn't have :)


Top
 Profile  
 
PostPosted: 18 Feb 2012 15:19 
Offline
BRFite -Trainee

Joined: 16 Feb 2012 18:40
Posts: 6
Cain Marko wrote:

Very, very interesting Ketan, welcome to the board - you come bearing good/interesting news. Can any jingos with inside clearances to sensitive areas such as golf courses or roof tops confirm this development?

CM


Thanks CM

nachiket wrote:
Are you sure it was an LCA? Some fighter jets are difficult to distinguish from afar. A M2000 for e.g. can easily be confused with an LCA if you catch only a quick glimpse or if it's too far away. A M2000 would be a rare sight in BLR though.


I don't think it was M2000, thought i could only get a gimps of it while riding. I ride home for the lunch as it is just about a KM from working place.

As for the LCA? or what i show was coming in to landing from Marthahalli end. May be they have upgraded one of the LSP which are flying.


Top
 Profile  
 
PostPosted: 18 Feb 2012 16:40 
Offline
BRFite

Joined: 20 Feb 2011 18:41
Posts: 598
Cain Marko wrote:
ketan.sojitra wrote:
Hi All,
This is my first post although I have been lurking on BR for almost 11 years.
Am SDRE IT guy from Bangalore.

Yesterday around 2 pm show LCA with IFR probe. Are there any of them LSP or PV flying with IFR attached? Or was it LSP 6/7


Very, very interesting Ketan, welcome to the board - you come bearing good/interesting news. Can any jingos with inside clearances to sensitive areas such as golf courses or roof tops confirm this development?

CM


CM

Kakarat's photo of a scan of tejas booklet from AEROINDIA 2011 did show the IFR probe. i won't doubt if it has been carried to it's logical conclusion. so what ketan is saying may actually be true!! :mrgreen:

FWIW take a look at this -

http://www.bharat-rakshak.com/media/Aer ... 1.jpg.html


Top
 Profile  
 
PostPosted: 18 Feb 2012 16:59 
Offline
BRFite

Joined: 23 Jan 2012 20:46
Posts: 131
Location: Aerospace capital of India
It was an M2K and not an IFR equipped LCA, the M2Ks are overhauled in HAL overhaul division, so finding one shouldn't be problem at all.


Top
 Profile  
 
PostPosted: 18 Feb 2012 18:52 
Offline
BRF Oldie

Joined: 01 Jan 1970 05:30
Posts: 2059
Location: NullPointerException
raghuk wrote:
It was an M2K and not an IFR equipped LCA, the M2Ks are overhauled in HAL overhaul division, so finding one shouldn't be problem at all.


An easy way to distinguish an M2K from an LCA is the massive size of the LCA wing compared to its fuselage. M2K's wing does not look as oversized.


Top
 Profile  
 
PostPosted: 18 Feb 2012 23:21 
Offline
BRF Oldie

Joined: 04 Feb 2004 12:31
Posts: 2487
Vikram W wrote:
So Boeing is planning to make about 10 Dreamliners a month by Q4 2013, scaling up from its current 2.5 a month . Meanwhile, HAL is going to make about 10 a year ramping up from Zero all of last year.... just saying.

http://online.wsj.com/article/BT-CO-201 ... 01263.html


Just saying what? Any idea how many firm orders Boeing has for the 787 as compared to the LCA? If Boeing didn't make that many a month, they'd lose a whole bunch of new customers to Airbus' A350, since those customers will not be willing to wait till they get their 787s after 10+ years or so. Boeing replaced the anaemic 767 line with the 787 line since there were almost no orders for the 767 anymore..and then set up another one at its Everett plant just because it has so many orders for the 787..and then it went on to set up another entire 787 factory in South Carolina because even that wasn't enough.

Why would HAL set up a larger assembly line unless they can get firm orders from their one and only customer? If IAF only intends to place orders for 40 Tejas Mk1, HAL will only set up an assembly line for 10.


Top
 Profile  
 
PostPosted: 19 Feb 2012 02:58 
Offline
BRFite

Joined: 08 May 2006 13:44
Posts: 1133
Location: mumbai
Kartik wrote:
Why would HAL set up a larger assembly line unless they can get firm orders from their one and only customer? If IAF only intends to place orders for 40 Tejas Mk1, HAL will only set up an assembly line for 10.
Orders cannot be given until the design meets basic performance parameters.

In DRDO's own words http://www.drdo.gov.in/drdo/pub/dss/200 ... EMILAC.pdf
Quote:
It is seen that most of the performance parameters are deviating from the requirements.


Quote:
The Air brakes in Tejas provided at the rear spinal part of the fuselage to decelerate aircraft at higher speeds. Due to this rear location in addition to the deceleration it gives an uncommanded pitch up and directional stability reduction. Various improvement methods like perforated airbrake, updation of aero data set and fine tuning of control law gains were tried. Still the problem is not rectified completely.


Tejas airbrakes http://www.bharat-rakshak.com/media/Aer ... e.jpg.html Sukhoi airbrakes http://www.flickr.com/photos/vishwak/5436297107/ mounted close to CoG, so no such moment arm acting on the aircraft. Mirage 2000 airbrakes are mounted on wing http://rafaleair.free.fr/photo2/mirage%202000-5%20F.jpg close to CoG.

Common sense dictates such parts be close to CoG to minimize uncommanded movements. However, for reasons best known to designers, they didn’t. Simulation/Testing should have revealed this during design, but again, this went ahead.

F-16 has rear brakes, but they split open equalizing the force unlike the upward-only Tejas http://pafwallpapers.com/blog/wp-conten ... arrows.jpg

Solution
Quote:
A study taken up to utilize the main landing gear follow up door as an airbrake.
So we’ll see a plane that’ll keep opening its MLG doors in flight.

Quote:
One of the major out come of sea level trial of Tejas is that the drag of the aircraft is high such that the aircraft could not reach the supersonic Mach number at sea level.
Solution
Quote:
Nose cone extension using a Plug.
In Mk2

Quote:
Trailing Edge Extension (TEC)
Now this is interesting. Many BR members on seeing the abrupt training edge had commented that it would be draggy. http://imageshack.us/photo/my-images/88 ... 01is2.jpg/
Common Sense that airflow split at wing root leading edge should be enabled to rejoin at the wing root trailing edge.

Quote:
From the Fig. 12 it is seen that there is a sudden variation in cross sectional area at the rear end of the fuselage also. This can be minimized by the modification in the trailing edge using TEC. Fig. 15 and Fig. 16 shows the rear fuselage before and after modification.
Again, why didn’t this come up during initial design/testing.

Quote:
The fighter variant of Tejas is not meeting the STR requirement of ASR.
Atleast until 2009, there was no solution in place.
Quote:
A detailed study to implement Levcon in fighter and identification of other design constraints is under progress.


IAF has valid reasons to describe Tejas as a deformed Cheetah. Despite that 40 planes have been ordered, that is 5.5% of its authorized fighter force. FWIW, I doubt IAF will ever deploy Mk 1 in air to air combat, risking the lives of the pilot without performance requirements being met. Also, with further design changes, manufacturing will be impacted.


Top
 Profile  
 
PostPosted: 19 Feb 2012 03:10 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
Tsarkarji we have done this so many times. Supporters of the forces insist everything should be fine before they are inducted, supporters of the tejas say, the forces inducted far inferior equipment in the past. I am not even an aviation noob, but high landing speed of MIG21 was/is considered hazardous, so why didnt the famed MIG bureau consider this while designing ? This aspect of MIG21 is taken as a characteristic of the aircraft and tactics built around it. Similarly there was something with the JAG

In similar vein cant the IAF accept it and make it better rather than coming up with newtonian statements like "it is a deformed cheetah" ? Why wasnt the IAF involved in providing design inputs during the 1990-93 timeframe ? I am sure they have a wealth of experience in operating aircraft a simple thing(the CoG thing) that could strike you(no offence intended) would have struck any iaf pilot Why didnt they communicate it then? Both sides are to be blamed hope AMCA charts a different course


Top
 Profile  
 
PostPosted: 19 Feb 2012 04:52 
Offline
BRFite

Joined: 23 Jul 2011 16:05
Posts: 246
Location: On the sofa.
Tsarkarji, thank you for the informative post.

The linked DRDO article was very interesting. By any chance, if you have more links to any other similar articles on LCA/HJT-36/Dhurv could you please share them? I would like to go through them.

Thanks.


Top
 Profile  
 
PostPosted: 19 Feb 2012 06:27 
Offline
BRF Oldie

Joined: 04 Feb 2004 12:31
Posts: 2487
tsarkar wrote:
Orders cannot be given until the design meets basic performance parameters.

In DRDO's own words http://www.drdo.gov.in/drdo/pub/dss/200 ... EMILAC.pdf
Quote:
It is seen that most of the performance parameters are deviating from the requirements.


Quote:
The Air brakes in Tejas provided at the rear spinal part of the fuselage to decelerate aircraft at higher speeds. Due to this rear location in addition to the deceleration it gives an uncommanded pitch up and directional stability reduction. Various improvement methods like perforated airbrake, updation of aero data set and fine tuning of control law gains were tried. Still the problem is not rectified completely.


I was talking about if from HAL's point of view. They won't be able to set up a larger assembly line without a larger order. As for whether or not the IAF can or cannot place a larger order for the Tejas, I don't subscribe to the theory that a few teething troubles should mean that they show dampened enthusiasm for the aircraft itself.

The pitch up issue is not a make or break type issue. The Typhoon had a major transonic pitch-up issue as late as 2002 that was solved with a major FCS update. Typhoon transonic pitch-up issue. And yet, did that mean that the Eurofighter nations said, hey lets just order a token 40 odd Eurofighter's each?


Quote:
IAF has valid reasons to describe Tejas as a deformed Cheetah. Despite that 40 planes have been ordered, that is 5.5% of its authorized fighter force. FWIW, I doubt IAF will ever deploy Mk 1 in air to air combat, risking the lives of the pilot without performance requirements being met. Also, with further design changes, manufacturing will be impacted.


Yes, why deploy a Tejas Mk1, when you have MiG-21s with even worse aerodynamic flaws that an inattentive pilot would push over the limit in the blink of an eye.


Last edited by Kartik on 19 Feb 2012 13:41, edited 1 time in total.

Top
 Profile  
 
PostPosted: 19 Feb 2012 12:22 
Offline
BRFite -Trainee

Joined: 12 May 2010 02:23
Posts: 74
Kartik, I was juxtaposing HAL manufacturing speeds vis-a-vis other companies ( making a much larger and complex plane). HAL bosses claimed they would be rolling out one fighter a month starting September 2010. So far all we have had is missed deadlines. You can all jump in and tell me that IAF has not given firm orders , but as the poster above mentioned, it's more of a chicken and egg story. IAF has committed to higher numbers, but ASRs are still not met and delivery deadlines have slipped to a point that not a single new plane flew in 2011.


Top
 Profile  
 
PostPosted: 19 Feb 2012 12:34 
Offline
BRF Oldie

Joined: 11 Jan 2009 00:14
Posts: 2490
Vikram W ji you havent visited the raffy thread i suppose(link posted by kartik ji)
rafale flight test

From the above link
Quote:
To date, about 70 Rafales have been delivered, with a current production rate of 12 a year.

so either rafale is not as complex as tejas or Dassault is as inept as HAL


Top
 Profile  
 
PostPosted: 19 Feb 2012 23:21 
Offline
BRFite

Joined: 27 Nov 2008 11:25
Posts: 377
Regardless of how the IAF characterizes the LCA, if India pursues her own strategic goals - not in consonance with the hyper power blocks, the deformed Cheetah may be the only cat in Indian service with any claws and fangs! Others may simply be grounded!


Top
 Profile  
 
PostPosted: 20 Feb 2012 01:41 
Offline
BRF Oldie

Joined: 29 Oct 2003 12:31
Posts: 24523
Location: NowHere
Relying on french technology against russian one, does not lead to independence rather only transferring dependence to another country. The problem is DRDO's failure and GoI support to all indigenous efforts for Kaveri, which is core for any dependency relationship. No matter, how successful LCA is, if Kaveri-snecma is all it gets, then we are totally dependent on french for executions. All it takes is sarkozy or a future fr president making a statement.

Kaveri++ standing by itself.. charting its own life time and establishing for our services is vital for LCA's long term goals. This $2b deal with fr needs to be reviewed by strategists, and work with already dependent nations to reduce dependency on long term basis. The short term dependency is manageable, for us, but not long term. Fr is our next gen russia!


Top
 Profile  
 
PostPosted: 20 Feb 2012 03:27 
Offline
BRF Oldie

Joined: 04 Feb 2004 12:31
Posts: 2487
tsarkar wrote:
Quote:
The Air brakes in Tejas provided at the rear spinal part of the fuselage to decelerate aircraft at higher speeds. Due to this rear location in addition to the deceleration it gives an uncommanded pitch up and directional stability reduction. Various improvement methods like perforated airbrake, updation of aero data set and fine tuning of control law gains were tried. Still the problem is not rectified completely.


Tejas airbrakes http://www.bharat-rakshak.com/media/Aer ... e.jpg.html Sukhoi airbrakes http://www.flickr.com/photos/vishwak/5436297107/ mounted close to CoG, so no such moment arm acting on the aircraft. Mirage 2000 airbrakes are mounted on wing http://rafaleair.free.fr/photo2/mirage%202000-5%20F.jpg close to CoG.

Common sense dictates such parts be close to CoG to minimize uncommanded movements. However, for reasons best known to designers, they didn’t. Simulation/Testing should have revealed this during design, but again, this went ahead.

F-16 has rear brakes, but they split open equalizing the force unlike the upward-only Tejas http://pafwallpapers.com/blog/wp-conten ... arrows.jpg


Even the Hawk had a single airbrake that was located in front of its ventral fins. Lack of common sense on the part of Hawker Siddeley perhaps?

Image

Image

Even the Tornado's airbrakes are located right at the end, just under the fin

Image

And look at where the F/A-18's airbrakes are located..
Image


Top
 Profile  
 
PostPosted: 20 Feb 2012 06:51 
Offline
BRFite -Trainee

Joined: 30 Apr 2008 15:06
Posts: 54
Kartik wrote:
Even the Hawk had a single airbrake that was located in front of its ventral fins. Lack of common sense on the part of Hawker Siddeley perhaps?

Even the Tornado's airbrakes are located right at the end, just under the fin

And look at where the F/A-18's airbrakes are located..

I am no aero expert.
Is the problem with uncommanded pitch-up in LCA is because of delta wing?
I ask because, all other aircraft examples Kartik took can compensate for pitch up by the elevators. Since LCA's air-breaks appear to be dang on delta wing Aileron are they more of a problem?


Top
 Profile  
 
PostPosted: 20 Feb 2012 07:32 
Offline
BRFite

Joined: 06 Mar 2001 12:31
Posts: 216
Location: Niyar kampootar onlee
IIRC, even the Gnat used the MLG doors as airbrakes. I always thought it was a very clever idea and wonder why more aircraft don't use this technique - probably saves weight as well.


Top
 Profile  
 
PostPosted: 20 Feb 2012 08:59 
Offline
Forum Moderator

Joined: 02 Apr 2010 01:21
Posts: 2842
Raman wrote:
IIRC, even the Gnat used the MLG doors as airbrakes. I always thought it was a very clever idea and wonder why more aircraft don't use this technique - probably saves weight as well.

That is exactly my thought!

The only reason I could think of is that while coming in to land the aircraft has lower decelerating power without dedicated airbrakes.


Top
 Profile  
 
PostPosted: 20 Feb 2012 09:01 
Offline
Forum Moderator

Joined: 02 Apr 2010 01:21
Posts: 2842
Reddy wrote:
Kartik wrote:
Even the Hawk had a single airbrake that was located in front of its ventral fins. Lack of common sense on the part of Hawker Siddeley perhaps?

Even the Tornado's airbrakes are located right at the end, just under the fin

And look at where the F/A-18's airbrakes are located..

I am no aero expert.
Is the problem with uncommanded pitch-up in LCA is because of delta wing?
I ask because, all other aircraft examples Kartik took can compensate for pitch up by the elevators. Since LCA's air-breaks appear to be dang on delta wing Aileron are they more of a problem?

No it is just simple physics ... if you apply a force not passing through CG, it would provide a moment, delta wing or not.


Top
 Profile  
 
PostPosted: 20 Feb 2012 10:52 
Offline
BRFite

Joined: 05 Dec 2008 22:23
Posts: 254
the gear box of India’s Light Combat Aircraft (LCA), Tejas, was tested in the CATH chambers.The building contains Combined Altitude, Temperature and Humidity (CATH) chambers, thermal shock chambers, dust chambers, corrosion chambers, and so on, where the various parts of radars are tested thoroughly before the systems are deployed in the field. The thermal shock chamber has three compartments. In the “cold” compartment, the temperature ranges from -700 Celsius to +800 C and in the hot cell, it ranges from 00 C to 2000 C. The third compartment has ambient temperature. The airborne radar systems are tested in these temperatures because when an aircraft climbs to an altitude of 40,000 feet (12,000 metres), the transition time from the ambient temperature to freezing cold is only 10 minutes. The airborne radar systems should withstand these thermal shocks. :)
Combined Altitude, Temperature and Humidity (CATH) chambers


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic This topic is locked, you cannot edit posts or make further replies.  [ 4018 posts ]  Go to page Previous  1 ... 73, 74, 75, 76, 77, 78, 79 ... 101  Next

All times are UTC + 5:30 hours


Who is online

Users browsing this forum: Google [Bot], Google Feedfetcher, Prem Kumar, Srivastav and 13 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group