Thursday, October 22, 2009

SPECIAL: Dhruv Shakti In Siachen






By Group Captain Hari Nair
Flight Ops (Rotory), HAL

It is the raison d’être for the Advanced Light Helicopter (Dhruv) with Shakti engines, and the very mention of the mission starts the adrenaline rush in a helicopter pilot.

Picture the stark landscape of the Siachen Glacier comprising just three colours: the Brown of the craggy mountains with peaks so sharp that they resemble fangs, the almost alien dark Blue of the high-altitude sky, and the dazzling White of the perennial ice cover. Then throw in a stupefying mix of high-air temperature and rarified atmosphere, add a postage stamp-sized helipad situated between deep ice crevasses at a geographical elevation of 5,940m (19,480 ft). The mission is to land on that postage-stamp helipad at a temperature of ISA+20 (-5°C), hover the helicopter Out of Ground Effect (OGE) with 200 kg of load and fuel for one hour of flying plus 20 minutes of reserve.

To add a further bit of spice as if all this were not enough, there are also tactical considerations in the approach and getaway due to extreme proximity of the helipad to a very ‘friendly’ neighbour on the west. Simply impossible you say? Well you were right — up to now that is. Demonstration of the mission was well beyond the performance envelope of most helicopters and in fact it was one of the reasons for development of the Lama (Cheetah) helicopter from the Alouette-III (Chetak) in the 1970s.

Although the Cheetah manages some payload in the hot summer months,it is unable to meet the above mission requirement. Also, its payload drops significantly in ISA+20 conditions at that altitude. The mentioned mission requirements appear beguilingly simple — however at those stated conditions, everything (aerodynamics, engine performance, control margins, handling and stability) tapers off to a point, usually well short of the target for most helicopters.

It is not just about additional power from powerful engines. There are helicopters that can fly at the required altitude. However, they invariably are at the limits of control margins, stability and handling due to their conventional hinged rotors, and therefore are practically not suited for such missions in the harsh flying environment which is invariably accompanied by extreme turbulence. Also, the technical trick is to translate the additional power available from the more powerful (but invariably heavier) engines into rotor thrust and still have a useful margin of payload. Usually, at that altitude, the power required by conventional rotor systems to hover with useful payload and fuel rapidly outstrips the power available from most turbine engines.

So, it is that sort of a target that would make most helicopter designers and test pilots frown, shake their heads and mutter darkly under their breath —“elusively out-of-reach and quite simply impossible”. However, the ALH was designed to stringent manoeuverability requirements specified by the IAF and Indian Army. Some of its capabilities are routinely demonstrated by the Sarang Display Team. In fact when various combinations of manoeuvres were initially tried out by this scribe as a former team-member to define the display manoeuvre sequences, there were always generous margins available on all controls.

The ALH’s highly manoeuverable rigid rotor system has some beneficial spin-offs at high altitude — good control power, good control margins and easier handling for pilots. The typical high-altitude sluggish handling and inertia in other helicopters is absent in the ALH. The controls remain crisp, with adequate control margins and good stability. The only compensation on approach to a helipad is to cater for the higher True Air Speed (TAS) and reduce the IAS appropriately at an earlier point.

On 11 Aug 2009, at 0750 hrs, the shrill whine of two escorting Cheetah helicopters mixed with the deeper roar of the ALH’s Shakti engines broke the morning silence on the glacier as the ALH-Shakti made an approach to the helipad.

The observed temperature was between -1°C and0° C (ISA+22) and Wg Cdr (Retd) Unni Pillai (Chief Test Pilot (RW), HAL) was at the controls with Lt Col T. Srinivas. The two experimental test pilots wereintensely focused on the difficult approach, which under the best of conditions usually approaches near white-out condition.

This was the beginning of the culmination of years of hard work by the dedicated team of designers, who had toiled hard to achieve the ‘impossible corner point’. They had strived to achieve the near-perfect mix of carefree handling of the ALH’s rigid rotor system with abundance of power from the Shakti engines at extreme altitudes. While ‘Srini’ called out the approach and reserve power parameters, Unni manipulated the controls and brought in the ALH to a hover over the tiny helipad.

On the approach, the ALH hadan equivalent mission payload of175 kg on-board. Unni brought in the ALH to a low hover, pulled up into a hover OGE, while Srini checked the power and other margins. After the sit-down, personnel from the post loaded upthe helicopter with an additional 160 kg and the crew pulled up the ALH to hover OGE above 12m (35 ft) on radio altimeter.

The hover was a tricky exercise — too low and they would be ‘in Ground Effect’ which would affect the accuracy of the test, and if too high, the crew would lose sight of the tiny helipad under the helicopter’s nose and would enter white-out. The crew observed the power margins and carried out a second sit-down. Another 80 kg was added and the ALH was hovered OGE for the third time. The power margin was adequate and so the crew carried out another sit-down and added a further 240 kg. The ALH was picked up for the fourth hover OGE. At that point, after catering for fuel burn during the successive hovers, the ALH had an equivalent of 619 kg of mission payload on-board, with fuel for one hour plus 20 minutes of reserve.

It was best summarised by the marshaller at the post who gave the thumbs-up to Unni and Srini, walked up to them after the last hover andy elled to them above the noise of the engines and rotors: “Jhahaz mein bahut dum hain (the craft has plenty of power)!” The ALH-Shakti had gone well beyond the mission requirement of 200 kg of load and had beaten the dreaded ‘corner point’.

It was an elated team of designers lead by Ms Rama Bhat who received thehelicopter back at Leh. The Chief Aerodynamist Mr Girish who had been into serious number-crunching into the late hours, notwithstanding the rarified atmosphere of Leh was especially happy since the performance had been as predicted. The team had also been supported very well on-site by representatives of the certification and inspection authorities. Team ALH-Shakti had proved true the ALH slogan — Any Mission, AnyPlace, Any Time.

(Gp Capt Nair flies for HAL's Rotory Wing Flight Ops team. He was commissioned in the helicopter stream of the IAF in December 1983. He has been associated with the Dhruv (ALH) programme, and commanded a combined Chetak-Cheetah unit in the Western Sector. He formed and commanded the Sarang Helicopter Display Team comprising Dhruv helicopters, during 2003-2005. He served as Chief Operations Officer, in an IAF base in the North-East)

Photos and Text ©HAL

24 comments :

Anonymous said...

proud proud proud!

Anonymous said...

india needs more DHRUVs period.The airforce itself should around 70more dhruvs. it's pathetic how the civil as well as the military operates helicopters of other origin when we have the best helicopter in the world.

Anonymous said...

I hope this article by Grp Captain Hari Nair will silence those who criticize the ALH for no reason whatsoever. There was a recent article by Manu Pubby, an Indian Express journo about the delay in the competition for new LUH for the IAF, where he boldly lied that the ALH was unable to perform at Siachen. Shameless liar.

Anonymous said...

Can someone explain me pic#1. Whats that green arch and red carpet like thing in valley??

Vin said...

Shiv-ji,

Isn't it time for Civil Operators to look @ Civilian variant of ALH too now????

I feel yeah!!!

Anonymous said...

Shiv,

Can you clarify on the Dhruv's high altitude performance?

Is it meeting the requirements for Siachen sorties? Or do we need firangi choppers?

The article mentioned by Anonymous@12:25 is here: http://www.indianexpress.com/news/army-has-to-wait-for-new-choppers/529782/1

Anonymous said...

Thanks for the report on Indigenous helicopter.

Now some food for thought on the indigenous tank arjun also please.

Kaushik said...

Way to go!
Nabha Sparsham Deeptam! :-)

AK said...

This article should warm the heart of every Indian and be a slap on the face of the naysayers of Indian technology. It is high time that the MoD and armed forces seriously start putting more money and resources into indigenously developed products. No more corruption laden defence deals with foreign natashas. Great work HAL and DRDO. You Rock!

the terminator said...

The word 'fantastic' sums up the performance level of the Dhruv Shakti. Grp. Captain Hari Nair and his team should be congratulated along with the designers at HAL for this marvelous effort. Journalists who call themselves Indian but are mere slaves of their foreign masters should be treated as mongrels for undermining indigenous effort.

Articles of extraordinary feats by the Dhruv Shakti team should be published in local and foreign aviation journals to publicize Dhruv as a stable and viable platform.

NJS said...

Good work , Now its proven technology .
MoD need to order for attack variant in large numbers .

Anonymous said...

Truly proud moment for every self respecting Indian.
Heartiest Congratulations to the team from HAL for achieving the near impossible. You guys have done us proud.
This new milestone set by the team should hopefully silence the vested interests for a little while.
Congratulations once again.

Anonymous said...

Great. Now we need to investigate why firangi choppers for medium lift capacity are being proposed for purchase and who are the sell-outs pushing their cause.

Anonymous said...

wow. Anybody who has doubts about Dhruv should now be absolutely satisfied because if any Dhruv can perform at a place like Siachen then surely it is a masterpiece

Anonymous said...

To all guys who knows about arjun mbt will be surprised to know that it is not first time that IA has create problem for better product for only money . In 1965 IA was equip with WW2 M4 Sherman tanks when it could equip with British-made Centurion Tank Mk 7, with the 105 mm Royal Ordnance L7 gun.But M4 Sherman tanks was chosen because money was offered to IA officers .The Centurion Tank order was capped at 188 .But In 1965 WAR only tank which perform was Centurion Tank whereas upgrade M4 like T-90 with western upgrade was easily defeated.I know 1965 story might be repeat with Arjun at 124 and T-90 as it was with Centurion at 188 and M4 Sherman .

Anonymous said...

This is definitely a crowning monent for the Dhruv team as I don't know of any other helicopter in the world that belongs to the same category and can achieve what Dhruv Shakti did. Once this test bed is converted to the production version, IAF or the IA should not have any hesitation in buying these - except the babus because they will not get their dirty kick-backs.

Anonymous said...

Those who criticise the ALH WILL have to shut their mouth.thanks to the CTP Mr.UNNI

anthony said...

The Dhruv chopper is cool!

No wonder it is adaptable for high altitude operations in mountainous areas.

captainjohann said...

Congratulations to the TEAM. God bless this group.

Anonymous said...

@ Last Anonymous,

Already Dhruv is onto production and is with IAF, IN and IA...

Now, It's time to promote Dhruv among Civilian operators like Deccan Aviation too...

Congrats HAL....

Anonymous said...

Jai Hind!!

flanker said...

This happened a long time back its the DS-62 in saarang colours that managed this feat ....
Cheers to dhruv and proud to be at RWR&DC

Sanjeev said...

good show. keep it up.

Anonymous said...

That is a very well written article. It really does touch a new high for Indian defence journalism.

My compliments

shiv