Indian Military Helicopters

vasu raya · Post by **vasu raya** » 03 Jan 2015 21:03

shiv, you are right about the change in AoA at 180 degree rotation, the advancing blade has some AoA, but the receding blade will have slightly higher AoA to compensate for the reduced air flow speed otherwise we will be seeing asymmetric lift. The change of AoA every 90 degrees seems iffy which is why they might be limiting the wing area of the stub wings. if the downwash on the much larger fuselage isn't significant, can they go for larger wings? so most of the cruise phase of the flight is less fuel intensive

Nik, to increase altitude the base AoA is increased but the cyclic stays, in the case of the hybrid design they seem to be relying on tail-prop than the tilt of the rotor to move forward

watch the rotor tilt:

deejay · Post by **deejay** » 03 Jan 2015 21:47

^^^vasu raya ji, your undersstanding that the rotor disc has an advancing side and a retreating side, is correct. AoA interpretation is also correct. The downwash of the Main Rotor Blade is very significant and any stub wing reduces hover performance, where in hover the helicopter is at the max power regime for any given weight / configuration.

The winged helicopter idea has resulted in the V 22 where the technological challenges were immense. I think given the problems with the V 22, innovations are still being looked at.

Another fact, the helicopter rotor disc in rotation acts like a gyroscope. A gyroscope has two properties: Rigidity and Precision. Leaving aside Rigidity for now, in a gyroscope, a force applied on pt. A will Preces through 90 degrees and act. (If you ever tried rolling a hollowed tyre, you would have applied forces to change directions of the rolling tyre. Try corelating from there.). So one needs to take in to account these forces while looking at where the change of angle will be required for an effect at the right place.

To increase helicopter speeds with similar configuration of engine and aircraft design interesting experiments with Main Rotor blade designs were conducted. One successful experiment was the British Experimental Rotor Profile (BERP). This design has been used on some machines in US and Europe.

The essential challenge to helicopter forward max speed or efficient forward flight is the fact that the Main Rotor Blades are long. The blade tips start reaching transonic regimes at high revs. By aerodynamic need (i forget exactly what) we need to have symmetrical aerofoil on the helicopter rotor blade. The symmetrical high lift aerofoils cannot withstand sonic regimes and therefore the max revs of the MRB need to be kept low enough to avoid going supersonic at tips. Longer the blades, lower the rev at which the tip speed will start approaching sonic regimes.

Hope, there is some clarity.

P.S.: I am no techie, but I attended a few classes on rotor dynamics and write from memory. You may read books on Rotor Dynamics from R. W. Prouty for more info. He is / was considered the ultimate authority on the topic.

Shreeman · Post by **Shreeman** » 04 Jan 2015 01:20

There is something transformative happening in this field. Perhaps biggest since the jets. Or turbines. The observation is perhaps merely a conjecture for designs being frozen today, so this may be OT.

Rigidity and weight, once they were enemies. So there grew separate categories in aviation history. Soon, in the time of healthy among us, they will be indifferent to each other. Materials and production methods exist already, just scale of manufacturing is yet to materialise.

The V22 is not the full exploitation of a transforming craft. The F35 and Harriers, basically same. Some more helicopters, other more fixed wing. Each preferring one principle of flight at all time. But each is also essentially a screw. Design tradeoffs were quite severe even when V22/F35 designs were frozen.

It all changes when the shape is no longer fixed to discrete one or two shapes. Because things wont break "easily" and stress/strain numbers become less dominant. On a small scale you already see the glimpses in the "insect" class "hobby" craft. The fixed nature of the rotor or the wing is temporary, and only because manufacturing hasnt caught up.

Designs that would vastly improve their performance in mid-life refits when they shed weight or gain lift outside of the main mechanism -- rotors or engine/wing -- could prolong the utility of those machines to C130 or Mig21 style lifespans. Otherwise, it will become a model year event. And few will have resources to buy new models each year.

Picklu · Post by **Picklu** » 10 Jan 2015 14:21

Hari Nair Sir, was that you today around 2:30pm over the Iblur camp? Thanks for the extended 20 mins display with LCH PV1. Looks like aero india 2015 practice started.

ravip · Post by **ravip** » 10 Jan 2015 14:45

Picklu wrote:Hari Nair Sir, was that you today around 2:30pm over the Iblur camp? Thanks for the extended 20 mins display with LCH PV1. Looks like aero india 2015 practice started.

Have seen LCH PV1 fly over south bengaluru, over kanakapura main road. It is usually seen in the after noon.

Picklu · Post by **Picklu** » 10 Jan 2015 21:20

Ok, for the viewing pleasure of aam brfites, the 42 images taken today of from the LCH flying display @ HSR

Photobucket Library

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Photobucket Slideshow

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Victor · Post by **Victor** » 10 Jan 2015 21:44

Pratyush wrote:^^^

IIRC, the MI 25 family uses the concept as visualized by you. That its wings do provide some amount of lift. However, when it comes to landing. Please note that every helo has the auto rotation ?? landing capacity. So am not sure what your point is regarding the sorter distance for safe landing.

The wing stubs on the Mi 25s are tilted downwards to minimize loss of downdraft from the main rotors.

When in ground effect, the rotors are pitched and produce a blast effect on the landing area. I was fortunate enough to witness some congress walas waiting to receive a neta at a helipad have their malas, topis and dhotis blown away by such a blast, leaving them to scatter, clutching their chaddies.

deejay · Post by **deejay** » 10 Jan 2015 22:21

Picklu wrote:Ok, for the viewing pleasure of aam brfites, the 42 images taken today of from the LCH flying display @ HSR

Photobucket Library

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Photobucket Slideshow

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Picklu da, thanks. I could almost visualise H Nair Sir in the cockpit taking the bird through her paces.

Picklu · Post by **Picklu** » 10 Jan 2015 22:31

Q for Gurus: I never realized before that the pitot tubes at the front had such pronounced horn type fundament. Are they permanent or will they be removed?

http://s1121.photobucket.com/user/Pickl ... ort=3&o=24

Btw, it was flown by a single pilot

http://s1121.photobucket.com/user/Pickl ... ort=3&o=39

the hover, sideway moves, tight turns .. all were there, an early aero india gift it seems

brar_w · Post by **brar_w** » 10 Jan 2015 23:57

vasu raya wrote:

The comments on the video are worth a read

deejay · Post by **deejay** » 11 Jan 2015 13:30

Picklu wrote:Q for Gurus: I never realized before that the pitot tubes at the front had such pronounced horn type fundament. Are they permanent or will they be removed?

http://s1121.photobucket.com/user/Pickl ... ort=3&o=24

Btw, it was flown by a single pilot

http://s1121.photobucket.com/user/Pickl ... ort=3&o=39

the hover, sideway moves, tight turns .. all were there, an early aero india gift it seems

The aircraft is being piloted by a single pilot. That is good, IMO. I hope it gets certified for single crew operations also.

shiv · Post by **shiv** » 11 Jan 2015 13:37

Picklu wrote:Ok, for the viewing pleasure of aam brfites, the 42 images taken today of from the LCH flying display @ HSR

Photobucket Library

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Photobucket Slideshow

http://s1121.photobucket.com/user/Pickl ... 20at%20HSR

Many thanks

Indranil · Post by **Indranil** » 11 Jan 2015 13:40

deejay wrote: The aircraft is being piloted by a single pilot. That is good, IMO. I hope it gets certified for single crew operations also.

^^^ What do you mean by that? It was always single pilot (in front) + WSO (at the back).

deejay · Post by **deejay** » 11 Jan 2015 14:33

Nothing very serious is implied but more from own experience of discussions on Single Pilot operations in multi-crew environment / cockpit.

The aircraft has multi-crew cockpit. Unless single crew operations are certified, we will need two people sitting in the aircraft for all roles. I remember a lot of discussions in crew rooms for Single Pilot operations of Cheetah (specially) and Chetak but very few places or roles existed where single pilot operations were cleared.

These clearances would change with a lot of 'ifs' and 'buts' thrown in. More to do with IAF and flight safety. Clarity on Single Pilot operations right from the start for LCH will be great. Certification for single pilot operations will be role specific (for eg. any armament on-board would / could make it mandatory for both crew in cockpit).

vasu raya · Post by **vasu raya** » 12 Jan 2015 08:41

Here are two modern designs, the X-2 prototype from Sikorsky

http://en.wikipedia.org/wiki/Sikorsky_X ... 00689).jpg

and the Ka-52 from Kamov

http://en.wikipedia.org/wiki/Kamov_Ka-5 ... _Ka-50.jpg

Both use co-axial rotors however the pusher propeller on X2 gives it higher speeds and instead of stub wings like the Ka-52 has, they claim that above 200kts, a slight +AoA on the rotor disc gives a lift to drag ratio twice that of a conventional chopper without the need for stub wings on the X2

if higher speeds are achieved on the LCH airframe maybe they could refuel from a fixed wing without doing the stunts like the above chopper in the previous post nor need to be carted in C-17s between north-eastern and western war theaters as described in Vivek's scenario

deejay · Post by **deejay** » 12 Jan 2015 09:17

Vasu Raya ji, in addition to these suggestion for higher forward speed there are other developments which have already been used.

Higher forward speed blade or rotor design has been for decades a major area of R&D in helicopter development. Shorter rotor blades, more lift, co-axial rotors (also removes tail rotor), stub wings for lift, tilt rotor, BERP (British Experimental Rotor Programme).

The BERP design which I have mentioned before, took a special fancy in the IAF at least with a lot of discussions and a favourite question among examiners responsible for aircrew categorisation and rating.

The BERP basically is a modification of the blade tip on the main rotor which allows higher tip speeds, provides increased lift without needing AOA adjustments.

http://en.wikipedia.org/wiki/BERP_rotor

From the wiki link:

How it works
If we wish to reduce compressibility effects in forward flight, we can use sweep on the tip of a rotor blade. Many modern helicopters use some form of simple sweepback on the blade tip. Examples are the UH-60 Blackhawk and the AH-64 Apache.

However, so we don't get centre of gravity or aerodynamic centre movements aft of the blade elastic axis (which can introduce undesirable aerodynamic and inertial couplings), then the tip must be configured with an area shift forward. This can be kept to a minimum by recognizing that the Mach number is varying along the blade so we do not have to use a constant sweep angle, thereby minimizing the amount of forward area shift.

The methodology used in the design of the BERP blade ensures that the effective Mach number normal to the blade remains nominally constant over the swept region. The maximum sweep employed on the large part of the BERP blade is 30 degrees and the tip starts at a non-dimensional radius r/R=cos 30 = 86% radius. The area distribution of this tip region is configured to ensure that the mean tip centre of pressure is located on the elastic axis of the blade. This is done by offsetting the location of the local 1/4-chord axis forward at 86% radius.

and...

The BERP blade employs a final geometry that performs as a swept tip at high Mach numbers and low angles of attack, yet also enables the tip to operate at very high angles of attack without stalling. This latter attribute was obtained by radically increasing the sweep of the outermost part of the tip (the outer 2% approximately) to a value (70 degrees) where any significant angle of attack will cause leading edge flow separation.
Because the leading edge is so highly swept, this leading edge separation develops into a stable vortex structure which rolls around the leading edge and eventually sits over the upper surface (as on a delta wing aircraft). This mechanism is enhanced by making the leading edge of the aerofoil in this region relatively sharp.

This rotor profile has been used on UH-60 Blackhawk and the AH-64 Apache. (from the above link)

deejay · Post by **deejay** » 12 Jan 2015 16:43

From: http://www.drdo.gov.in/drdo/English/DRD ... -ebook.pdf

EW Suite on MLH–Mi-17

EW Self-Protection suite, developed and integrated on Mi-17 helicopter is an integrated Radar Warning Receiver (RWR) and Missile Approach Warning System (MAWS) with BDL-CMDS. RWR can intercept and identify airborne and ground-based acquisition, target tracking and missile guidance 42 radars in the 1-18 GHz frequency band. Missile approach warning system is a UV- based passive
warner system for protecting aircraft against heat- seeking missiles by providing warning to the air crew. CMDS, an airborne defensive system, provides self-protection by passive ECM against radar, radar-guided and IR seeking, air-and ground-launched missiles and radar-guided anti-aircraft missiles. Protection is achieved by deceiving the missiles through the dispersal of chaff and/or flare. The systems were individually flight-evaluated for verification of their respective functional parameters and also evaluated in the integrated mode. After trials, the system has been recommended for the entire fleet of Mi-17 helicopters.

This is good development for this helicopter fleet. The Mi 17 Ops in CT / COIN Ops, in Khalsi, Kargil and Siachen areas will surely benefit if these are fitted as per recommendation on the entire fleet.

SagarAg · Post by **SagarAg** » 17 Jan 2015 21:26

Flying beauties

Courtesy: @writetake

vasu raya · Post by **vasu raya** » 17 Jan 2015 22:50

deejay ji, pardon as work had me on leash, the conclusion of the wiki article on BERP rotor sounded interesting with the blade AoA increased to 22 degrees and the retreating blade not reaching stall even at higher speeds. Wonder why Apache with such rotor has a altitude ceiling same as LCH when the blades give it better hover performance?

Anybody studied co-axial rotors with such blades?

vasu raya · Post by **vasu raya** » 19 Jan 2015 02:17

Here is a slow bi-plane with a good threshold for stall,

with today's advances the lower wing section can be folded under the fuselage as the plane transitions to higher speeds as enough lift is generated by the top wing alone. The right term seems to variable sweep wing and when fully stretched will be in the shadow of the top wing.

vasu raya · Post by **vasu raya** » 20 Jan 2015 09:08

Here is a video about the BERP rotor blades, watch from 1:07,

it seems to say the tip is shaped for high mach number much like a fixed wing aircraft and the outer edge aerofoil section allows for vortex formation along the length of the blade, the AoA of the blade then can be increased upto 22 degrees as this vortex holds the air flow stable

deejay · Post by **deejay** » 21 Jan 2015 15:55

^^^ Thank You Vasu Raya ji, that was a very informative video. I am trying to get my hands on the detailed drawings of the BERP blade which we studied in the AF. Apart from the sweep there are other features and tip parts on that design which play significant role in providing more lift, greater rotor tip speed and increased forward sweep.

In your previous post you had mentioned about high hover performance and high altitude performance with BERP. Why the Apache is on the same levels as LCH at High Altitude and co-axial rotors with such blades. I bounced these questions with some rotor dynamic 'enthusiasts' in the IAF and they have all scurried to the rabbit holes and promised to come back on these. Personally, I am unable to add anything as I am out of depth here and do not have the resources / research material at present.

ravip · Post by **ravip** » 21 Jan 2015 16:17

LCH formation dancing over my house. My god you should have listened to the turbine sound. Truly awesome.

Picklu · Post by **Picklu** » 21 Jan 2015 19:09

^^ Am I seeing 3 LCHs? When did the 3rd proto start flying?

JTull · Post by **JTull** » 21 Jan 2015 21:43

Picklu wrote:^^ Am I seeing 3 LCHs? When did the 3rd proto start flying?

on 12 nov 14

joygoswami · Post by **joygoswami** » 22 Jan 2015 10:19

More.

vasu raya · Post by **vasu raya** » 22 Jan 2015 17:28

deejay wrote:^^^ Thank You Vasu Raya ji, that was a very informative video. I am trying to get my hands on the detailed drawings of the BERP blade which we studied in the AF. Apart from the sweep there are other features and tip parts on that design which play significant role in providing more lift, greater rotor tip speed and increased forward sweep.

In your previous post you had mentioned about high hover performance and high altitude performance with BERP. Why the Apache is on the same levels as LCH at High Altitude and co-axial rotors with such blades. I bounced these questions with some rotor dynamic 'enthusiasts' in the IAF and they have all scurried to the rabbit holes and promised to come back on these. Personally, I am unable to add anything as I am out of depth here and do not have the resources / research material at present.

Thanks deejay ji, recently in news was the presenting of a 3D model Su-30 MKI in an IAF function, does that mean the wind tunnel models can be built using this technique now? a decade long research for these blades seemed lot of effort yet not every flagship chopper uses these. And also what is the Russian comeback?

deejay · Post by **deejay** » 22 Jan 2015 18:06

^^^ AFAIK, the Russians never used the BERP design on their blades. They have continued to use Co-axial contra rotating main rotors which also help in reducing blade length and do away with tail rotor. Also, they have often used more than 04 main rotor blade system thus slowing down the revs required and hence lower tip speeds.

BERP as a design (IMO) would help in high top speed helicopters but I am unaware of its overall impact (as in % change vis a vis Co-axial rotors). The increase in top speed with this design will also have a limiting value and further increase in forward speed would need newer developments. In case the helicopter is not aiming for high top speed but the focus is more on short hops, small area operations from unprepared airfield the advantage of BERP is lost and conventional design would suffice.

Combat / Attack helicopters could obviously benefit but I guess the gains of BERP may be bettered by the Sikorsky X2 design and hence BERP would not make the cut with these new developments.

What attracts me to BERP design is that a lot is known and we may develop this hopefully with lesser R & D cost and time implications to improve forward speed performances on our own helicopters (Dhruv, Rudra, LCH,etc).

Thakur_B · Post by **Thakur_B** » 22 Jan 2015 20:23

TD-3 has a new camo paint job. Can't wait to see hi res photos.

Thakur_B · Post by **Thakur_B** » 22 Jan 2015 20:28

Picklu · Post by **Picklu** » 22 Jan 2015 21:55

JTull wrote:
Picklu wrote:^^ Am I seeing 3 LCHs? When did the 3rd proto start flying?
on 12 nov 14

Thanks JTull; must have missed it

vasu raya · Post by **vasu raya** » 22 Jan 2015 22:14

DJ, with the X2 the convergence seems to be co-axial rotors which puts more blades on the job and speed is push prop based. Although the tips might be run slower than BERP, the retreating blade stall will have a lower threshold with conventional blades. In contra rotating rotors does the retreating blade stall even matter as one blade is always in forward motion at any time and at high speed the lift provided compensates for the combined lift provided by the upper and lower blades before a retreating blade reaches stall speed.

btw,the co-axial rotors on Ka-50 also do not seem to help its altitude ceiling, not sure if its by design.

if I may add, the Augusta Westland chopper with BERP was selected after the altitude requirement was lowered, seems like we are running in circles with no way to improve the high altitude performance.

if we assume that the BERP blades are passe, implying the other side is willing to sell, then buying this technology might be an option than to develop it again.

Then the other factor is endurance, both for Naval applications and the East-West commute scenario, by increasing L/D, the BERP blades improve on this?

VinodTK · Post by **VinodTK** » 29 Jan 2015 02:59

India to buy 22 attack, 15 heavy-lift copters

Mumbai, January 28:

As part of Prime Minister Narendra Modi’s plan to bolster the nation’s military posture, India is to acquire 22 Boeing AH-64E Apache attack helicopters and 15 CH-47F Chinook heavy lift helicopters for the Indian Air Force (IAF), valued at $2.5 billion.

Approval stage

Officials in the know said the attack helicopter (Apache) and the heavy lift helicopter (Chinook) are currently in the Government approval stage.

“The Ministry of Finance and Cabinet Committee on Security needs to approve...before contracts are signed. All other steps are done,” officials said.

Sources pointed out that India’s defence acquisition process mandates that all contracts that are in excess of $50 million require 30% offsets. Way back in 2013, Boeing had signed a memorandum of understanding with Dynamatic Technologies of Bangalore, to manufacture the aft pylon and cargo ramp assemblies for the Chinook. Sources indicated that Boeing had done this in anticipation of the IAF order. When contacted, Boeing said it was deferring all questions on the Apache procurement to India’s Ministry of Defence for comment.

Offsets galore

“Defence spending eligible for offsets through 2017 are huge. Based on the current order pipeline, big procurement programmes ensure that offset obligations could become an opportunity worth $10-$20 billion for the domestic industry,” said sources.

Another official pointed out that offsets are expected to spur growth, as well as aid the basic intent of the offset policy, which is to build a domestic defence manufacturing base.

Force projection

“Multinational original equipment manufacturers with Indian defence contracts can discharge their offset obligations by sourcing military grade components from India,” the official added.

Boeing’s Apache is the most capable multi-role combat helicopter, “combining performance and lethality with more affordable and efficient maintenance.

“It will provide the Indian Air Force with enhanced dominant force projection capabilities, and will address the full spectrum of conflict to peace keeping and nation building.”

Newest member

India has been offered the AH-64E, the newest member of the combat proven Apache family, and is to get the latest upgraded version of the helicopter, which has been delivered only to the US Army. In the case of Boeing’s Chinook helicopter, “the tandem rotor H-47 Chinook is the most capable, advanced heavy lift helicopter, providing maximum value at the lowest risk.

The H-47 Chinook offers India heavy lift and high altitude transportation for a multitude of military, humanitarian, rescue, disaster relief, fire fighting and nation building missions in all climates and conditions and altitudes.”

Flight trials

The Chinook and an advanced version of the Mi-26 helicopter were put to flight trials in 2011, in desert and high altitude terrain. Boeing’s Chinook had beaten out Russia’s Mi-26, when the Indian Defence Ministry had opened bids in November 2012, said sources, adding that the Russian bid was set aside after officials failed to provide details on how they would execute their offset liabilities.

Boeing is deferring questions on the contract to India’s Ministry of Defence.

member_28756 · Post by **member_28756** » 30 Jan 2015 15:34

They lost 4 out of 7 ? Unbelieveable

http://www.janes.com/article/48382/ecua ... o-to-crash

Ecuador loses another Dhruv helo to crash

Gareth Jennings, London and Oliver Shorvon, London - IHS Jane's Defence Weekly
27 January 2015

As the only export customer of the type, Ecuador has now lost four of its seven Dhruv helicopters to accidents. India, which manufactures and also operates the helicopter (pictured), has grounded the Dhruv on several occasions over safety concerns. Source: HALThe Ecuadorian Air Force (Fuerza Aérea Ecuatoriana: FAE) lost a Hindustan Aeronautics Limited (HAL) Dhruv utility helicopter to a training accident in late January, the second to be lost this month and the fourth since deliveries began in 2009.

The accident, which is reported to have occurred on 27 January (the Ministry of Defence has yet to confirm it), happened near the town of Tena in the remote interior of the country.

According to the reports, there were no casualties among the four personnel on board.

Ecuador signed the agreement with HAL in 2008 for seven Dhruv helicopters at a cost of USD45 million. These were to be delivered in kit form and assembled in Ecuador, but this plan was later abandoned with the aircraft instead being manufactured in India.

In FAE service the Dhruv is operated by 2211 Combat Squadron, 22 Combat Wing (221 Combat Group), based at Simón Bolivar Airbase.

COMMENT
With this accident, the FAE has lost more than half of its Dhruv fleet in less than five years of operations. The first aircraft was lost on 28 October 2009, the second on 22 February 2014, the third on 13 January 2015, and the most recent reportedly on 27 January 2015. While at least one of these incidents has been attributed to pilot error, a loss rate of close to 60% is significant.

Dhruv crashes have not just been confined to Ecuador, the type's only export customer. India has also suffered multiple losses since introducing the type into service with its armed forces in 2002. Indeed, India has grounded its entire fleet on several occasions following crashes.

Whatever the findings of this latest accident turn out to be, the Dhruv cannot afford many more of these unfortunate incidents if future export sales are not to be adversely affected.

Aditya_V · Post by **Aditya_V** » 30 Jan 2015 15:53

Over 5 years, ecaudor has some challenging conditions. The report is bumcum regarding Indian crashes which have very minimal. Far better record that MI-17. Didnt we export one to Isarel?

Shreeman · Post by **Shreeman** » 30 Jan 2015 18:03

11 out of under 200 is not enviable. A proper registry and NTSB type inquiry and publication would help. But the dhruv is meant for indian forces + generous gifts. not commerce. so nothing except empty statements will arise.

member_28756 · Post by **member_28756** » 31 Jan 2015 16:10

Aditya_V wrote:Over 5 years, ecaudor has some challenging conditions. The report is bumcum regarding Indian crashes which have very minimal. Far better record that MI-17. Didnt we export one to Isarel?

Yeah I agree but the problem is it will hurt the export of this helicopter as the article pointed out. Arms industry is a cut throat business and a bad reputation is going to damage potential prospects not only of this helicopter but other sales as well.

dinesha · Post by **dinesha** » 31 Jan 2015 19:09

TD3

JTull · Post by **JTull** » 31 Jan 2015 19:31

Dhruv helicopters are good, says Defence Minister Manohar Parrikar

Thakur_B · Post by **Thakur_B** » 06 Feb 2015 11:54

Practicing for Aero India.