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Answering another query on the Dhruv helicopter, the Minister said the service ceiling of the chopper has been laid down as 6000 meters which has been achieved by it.
The Comptroller and Auditor General (CAG) had said recently that the HAL-built indigenous chopper was not upto the mark and overweight for replacing the Cheetah/Chetak helicopter fleet of the armed forces.
I agree with you on this. A lot is discussed about the CAG criticism by BRFites (includes me), but let us give due credit to HAL because it looks like all these performance issues were basically due to a weak engine.Marten wrote:^^^ This holds true only for the earlier version (currently delivered and serving). For the latest version with the Shakti engines (yet to be certified per CAG), the CAG report said it met all parameters. Relevant sections from my post on the previous page:Marten wrote:Oh, and how come everyone that said the ALH did not meet the specifications conveniently forgot to read the paragraph where it says the new Shakti engine has helped overcome all of those issues?
The Management stated (December 2009) that despite the deep background and experience of helicopters by MBB, the collaborator could not achieve the guaranteed parameter of BEW which is still an open point. Shakti engine (higher-powered engine) adequately meets the requisite payload with margins as demonstrated during the hot and high trials in August 2009.
Gentlemen,indranilroy wrote:Hazarding another guess. Notice that the mounting is actually almost in the same direction as the compression. If you draw a line through the length of the absorber, it will almost pass through the welding with the body of the mount. This is unlike most cases where the shock absorbers is almost perpendicular to the chassis. So the shock will actually travel through the length of the absorber, through the absorber mount and the body mount into the body. It would not be shear stress (trying to tear away from the weld) but to compressive stress (press against it). I believe that the part behind the joint (weld) must be fortified to take that shock.karthik wrote: I hope so but i think i get the theory behind the mounting now, its deliberately kept independent from the cockpit frame because any serious landing would not stress the structure and instead the mounting will either bend or crumble hence absorbing the shock without harming the frame and can be replaced later separately! I think thats the rational behind it.
Thanks Kartik.
Also the mount is in the shape of a downward "V". So in the case of a hard landing, the sides of this V will be subjected to compressive stress. And compressive strength of a metal is generally much higher than tensile/shear strength. So it should hold good.
Will wait for somebody else to answer if he/she knows the exact answer! Also as always, we all are waiting for the final version to show us the real LCH
By the way: was reading that an illustrated photographer called it a crocodile. What a compliment to the aesthetics of a mean machine! If I were the designer, I would have blushed up all red
Hari Nair wrote:@ Craig Alpert -Re -The ceiling of the ALH
Actually its cleared to 6400 m for the older TM-2222B2 engine (although at a lower weight)
and its now cleared to 6500 m for the new Shakti engine version at a fairly high All-Up-Weight
I'm not sure how CAG got its figure of 5000 m - the 6400 m ceiling is clearly specified in the helicopter's Flight Manual (older engine version) and is also practically achievable.
please check this is exactly apposite...concrete is made for compression and steel is used inside it to take tension...guess why...in any building...so property of being metal doesn't change if it's used in flying object, does it?And compressive strength of a metal is generally much higher than tensile/shear strength. So it should hold good.
Compressive and tensile loading was performed on a modified universal testing apparatus. Ti-Core and Flexi-Flow cem with titanium were measured to have compressive strengths of 41,132 and 41,876 psi and tensile strengths of 5219 and 4930 psi, respectively.
Thank you sir. It's an honour to have your following.Hari Nair wrote: Gentlemen,
The LCH undercarriage is a two-stage crashworthy design, designed and tested to attenuate impact forces at 10 metres/sec vertical velocity - that translated from 85% survivability. Its indeed a very specialised design.
LinkThe Indian Air Force will soon order an additional 59 Russian Mil Mi-17 helicopters on top of the 80 ordered earlier, the IAF chief said on Thursday.
The first deliveries of the 80 Mi-17 helicopters, ordered in 2008, will begin later this year, Air Chief Marshal Pradeep Vasant Naik said in an interview with India Strategic
i was trying to explain common sense in construction thats all. Steel is more or less a linear elastic material. Unlike concrete, which ismuch weaker in tension than in compression.Unidirectional fibers may be excellent in tension, but due to their small cross section, they have very little inertia and cannot take much compression. They will escape the load by bucking away.How can you use this as a measure between the compressive strength, tensile strength and shear strength of steel.
and you start bending it, where do you think it will give way, on the side or outside? Remember strain is on the outside, and compression is on the inside!
The US Army compiled statistics of crashes of their helicopters during the Vietnam war and they came with the US MIL STD 1290 for crashworthiness, which essentially charts out a percentile survivability in the event the helicopter is able to absorb specified impact loads in the vertical, longitudinal and lateral directions. As per Mil Std 1290, the highest (practical) percentile survivabile crashworthy helicopter is in which the helcopter impacts at 12.8 m/s in the vertical and the impact loads are progressively attenuated by the undercarriage (wheels & oleos), crush sections of the lower fuselage, fuel tanks and finally by the crashworthy seat that is mounted on two rails and strokes down-wards. At the end of it all, the aircrew should experience a maximum vertical deceleration of 14.5 G (tolerance of the spine). Such a design is expected to be 95% survivable - which means that for a helicopter designed to the standard, the crew should be able to survive 95% of foreseen crash conditions (with minor injuries - perhaps a broken bone)indranilroy wrote:Would you know what are the two-stages? Also how do we calculate the percentage of survivability. Are there cases of how the helicopter can crash land and with this tolerance we can overcome 85% of those cases? Of the 15% of the rest of cases may be coming down on its side, top, tail, etc.
Can a helicopter with freely rotating blades come down much faster than 10 m/sec?
Well, the LCH shares the same rotors of the ALH, however has a different fuselage and certain other different systems. The engines are the 'Shakti', used in the latest ALH version.naird wrote:Also please do tell us about LCH...hows your feeling...hows the handling...anything and everything would be highly appreciated.....
Yes, you will see changes to the LCH - essentially pertaining to the tail-plane, the wings, outer-fins, addition of some streamlining (including a ventral fin incorporating the tail-wheel) and some other details.Kartik wrote:There has been a lot of speculation about whether the design of the LCH is going to be modified later on or not. As in whether the outer mould line is frozen or not and whether or not it will be further streamlined. Regarding the LCH's canopy, it offers more visibility and less protection to the pilots than a few other gunships, so will this be modified or is this the final canopy design?
We already know that weight reduction is a stated goal of the program, so which are the possible areas where weight can be reduced ? What is your opinion on this? Also, there is speculation that the LCH already reached its highest speed during trials. Is this true ? What have been your impressions of the LCH so far ?
Well, the tandem seat and tail-wheel layout appears to be the right way to go for the dedicated role LCH.naird wrote:Also please do tell us about LCH...hows your feeling...hows the handling...anything and everything would be highly appreciated.....
Hari Nair wrote:
Weight reduction - the AUW issue is a 'close tolerance' thing (!) because of our high altitude requirements. Unlike the US and Russian helicopters that are primarily designed for lower altitudes, our operational requirements are far,far more demanding to cater for the Leh-Siachen-Kargil sectors. At those altitudes and at those stated conditions, everything (aerodynamics, engine performance, control margins, handling and stability) tapers off into a point, usually well short of the target for most helicopters.
We have at present, one prototype LCH -Technology Demonstrator (TD)-1. Two more TDs are planned. Each TD (as is typical in Flight Testing) has its design objectives. Through the ALH program, we have adequate in-house capability for flight testing the LCH. Also, other project teams, although working under different groups/divisions/agencies (the IJT, LCA, etc) are not exactly in water-tight compartments and when required, obviously do share their know-how. However, integration of specialised systems & weapons requires involvement of their respective reps - nothing unusual about that & its the norm worldwide.naird wrote:Excellent ...excellent......Thanks Hari Sir...How many prototypes of LCH has HAL developed so far ? Also are we roping in International partners for testing guidance/direction or will it be a sole HAL effort with inputs gained from ALH program? And as rakall pointed out ..any updates on the weight reduction program ?
Sir -- since you are placed in a area what we call "Core of Indian aviation"...please be kind enough to share inputs on other programes such as LCA , ALH , etc ..in the respective threads (whatever information you can/allowed to)... We often are left wondering and fear the worst when no news comes out .....
Thanks once again...waiting for more posts !!!!!
Welcome to BRF, sir. And if you can manage the above feat, aapke muh mein ghee shakkar.Hari Nair wrote:re- The LCA, IJT and others- I will try and persuade my Fixed Wing Test Pilot colleagues to log in!
Well, Shiv as we had discussed during the inaugural flight ceremony, the LCH has a few low altitude roles also. The Apache & Mi-28 are the big fellas on the block at 9-10 tonnes AUW class, compared to the LCH's 5-6 tonnes. The Mi-28 is heavily armoured-check out pics of its cockpit transparency -even all its cockpit glasses are resistant to 20 mm calibre cannon fire! It also packs a heavy duty 30 mm 2A40 cannon that's a straight lift from the Army's BMP-2 IFV! However, in my opinion, the D-model Apache scores over the Mi-28 mainly due to its hyper-tech Longbow fire control radar and networked systems. Also, the Apache is no delicate helicopter - you would have seen it up close and you know what I mean. And now I guess we are chummy enough with Uncle Sam for all avionics and systems to be given to us.shiv wrote:Looks like the LCH will be optimized for high altitude and fly where others cannot fly. But that would probably explain why the IAF is looking for dedicated attack helos in the plains which will not be used at high altitude. I am guessing that this is where the competition between the Apache and Ka 50 or Mi 28 or whatever will be.
I would like to address your last paragraph. There must be some compelling reasons for the selection of heavy weight gunship like Apache over already available LCH. There is a tones of difference between operating way of both Apache and LCH. Apache and its version are highly optimized for getting Pinpoint targetting and positive target identification. Despite Apache's multirole applications of avionics, still some of its avinioncs like Longbow radar which enable it to engage the target from stand off range doesn't allow its Co-Pilot to have positive target identification and for that matter Apache Pilot need to get closer to the target to get visual identification which make it vulnerable for Surface to Air missiles and Anti Aircraft fire.Rahul M wrote:Hari sir, a couple of questions about LCH,
> what is the status of the DIRCM project for LCH ? has it been decided which version shall be used ?
> are there any plans for a radar equipped version in the future ?
> will the HeliNa be ready by the time LCH enters service ? if not, is the LCH team looking at any alternate ATGM's ?
and one of WSI dhruv,
> how far has its testing progressed and when is it expected in service ?
this question is not exactly about the LCH project and I'll understand if you don't want to answer it.
> what is the role envisaged for the currently ongoing attack helicopter competition (the one in which apache etc are participating) in light of the fact that LCH can do most if not all of the functions that can be carried out by those platforms ? is it a stop-gap measure to cater for the gap between the hinds getting long in the tooth and LCH induction or for a separate role altogether ?
thanks in advance.
Well, I never done any speculation rather I am putting my words based on well informed sources. If you chose to trust me then I can assure you that there is nothing pointless in my argument. Major issue is always been regarding Positive Target identification and this particuler thing itself determine the performance of attack gunship. My post was in particuler directed towards your comments of LCH fulfilling part of the operating performance as Apache.Rahul M wrote:bihanga, I think most people here can present the arguments for and against that view quite well.
there is however a difference between speculation (even educated speculation) and actually knowing. hope you got my point.
That would be great - the last time we had someone from that side was BB Misra - before the first flight of the LCA.Hari Nair wrote:
re- The LCA, IJT and others- I will try and persuade my Fixed Wing Test Pilot colleagues to log in!
Sir,Raja Bose wrote:Welcome to BRF, sir. And if you can manage the above feat, aapke muh mein ghee shakkar.Hari Nair wrote:re- The LCA, IJT and others- I will try and persuade my Fixed Wing Test Pilot colleagues to log in!