An Indian Air Force helicopter with 14 persons onboard crashed into the hills near Coonoor, Tamil Nadu in southern India, around 12:20 PM (IST), Wednesday Dec 8, 2021. The Russian-made Mi-17 V5 helicopter ex- IAF’s 109 Helicopter Unit (109 HU) had taken off from Air Force Station, Sulur to the military cantonment at Wellington in The Nilgiris (Blue Mountains) when it crashed about ten miles short of destination.
It is an unprecedented loss of the highest ranking officer in Indian military. The crash takes away India’s first Chief of Defence Staff General Bipin Rawat, his wife Mrs Madhulika Rawat, four crew, the general’s defence advisor, staff officer, protocol officer and five personal security officers. IAF confirmed 13 deaths by Thursday evening. Lone survivor Group Captain Varun Singh, directing staff at Defence Services Staff College, was admitted to the military hospital at Wellington with grave injuries (he has since been shifted to Command Hospital Air Force, Bengaluru). Hope and pray he makes it.
I have vivid memories of a sortie I flew along that route many years back (1995) on a single-engine Chetak (Alouette) helicopter. Also, ironically, in 2020, I was witness to a safe, uneventful landing of a similar V5 from the same 109 HU at the Wellington Gymkhana Club (WGC) helipad. I subsequently used photos and videos captured of that beautiful flight to explain, with theory, experience & accident investigation, the nuances of helicopter performance. Though “performance” seems unrelated to the latest tragic crash, with a heavy heart, I write this piece to inform the lay reader nuances of weather, topography & flight rules for helicopter flying in the hills.
Gen Rawat was headed for a guest lecture at the nearby Defence Services Staff College (DSSC) at Wellington. DSSC is a tri-service establishment that conducts the Staff Course for mid level officers. The Wellington cantonment also houses the Madras Regimental Centre, a military hospital (MH), the Wellington Gymkhana Club and support units. It is a beautiful town with salubrious weather year round, throbbing with the energy of young recruits from MRC & the “Owls” of DSSC. Homes and livelihoods at the one horse town are practically supported by the military, tourism & tea estates. The peace & calm is occasionally broken by a passing helicopter landing at WGC. Locals are used to helicopters that appear periodically overhead; so much that they remember accurately the route the choppers follow. On Dec 8, as per eyewitness accounts to this writer, the helicopter appeared to be flying lower and slower than usual. Fog or mist can also be seen in certain visuals that have appeared on open media. The regular beat of churning rotors suddenly ground to a horrible stop, chopping huge tree trunks & erupting into flames.
Flight Rules and Meteorological conditions
The fairway of golf course at Wellington Gymkhana Club (WGC), Coonoor in The Nilgiris has a helipad with unidirectional approach that’s usually used for airlifts ex-Sulur/Coimbatore. Military helicopters fly that route for VIP visits, logistics, medical evacuation, etc. It is a short climbing flight of less than 50 miles that would take a Mi-17 V5 about 30 mins along a predetermined route that military crew have been flying for decades. The helipad is approximately at an elevation of 6000 feet with hills and dense forests all around.
Such flights are undertaken under ‘Visual Flight Rules’ or VFR, which implies “see & avoid”. Most civil flights and fixed wing aircraft fly under IFR or Instrument Flight Rules. Most military helicopters operate VFR at low height, particularly in the hills where the departure or destination may not be equipped with modern navigation or landing aids.
The weather and visibility conditions that define ‘visual’ and ‘instrument’ meteorological conditions (VMC / IMC) are known to all pilots. An important distinction is in order. While you can abide by VFR or IFR in VMC, you cannot fly VFR in IMC. It is a simple geometrical problem of height vs terrain. You cannot avoid what you cannot see unless you fly at safety altitudes. IFR was impractical in the given location where the ill-fated helicopter was flying. ‘Continued VFR flight into IMC’ or ‘inadvertent IMC’ (IIMC) is one of the leading causes of helicopter accidents worldwide. Faith cannot move mountains in aviation.
Weather in the hills
Coonoor for the most part has lovely salubrious weather with clear visibility & sparkling clear skies. However, during winter season, low drifting clouds, fog & mist often roll in unannounced, reducing visibility that can push “see & avoid” VFR flights into peril. Also, technical issues, if any develops, can impose dangers due to hilly terrain and/or reduced performance. As such, the higher you climb, the lesser the margins for performance, abnormal situations or the room for error.
A VFR flight that encounters bad weather has one of three options:
- Divert or force land before weather closes down
- Deviate from flight path so as to avoid weather and continue flight keeping within VMC minima
- Change to IFR flight plan in coordination with ATC
There are practical limits to options 1 & 2, especially in the hills or over ‘hostile terrain’. However, if the destination is a helipad like WGC with no IFR aids or published IFR procedures, option 3 is all but ruled out. Another danger is ‘scud running’ — descending to keep below clouds, thus getting trapped between lowering cloud ceiling and rising terrain.
The helicopter and crew
The Mi17V5 is a robust twin-engine helicopter with advanced glass cockpit, weather radar, moving map display, autopilot with flight director, etc. As compared to my generation of pilots who cut our teeth on VFR-only helicopters, sometimes getting lost and even descending to read the name of railway stations to reorient, aircrew today are trained for instrument flying and IFR like never before. Almost every helicopter pilot in the IAF today has a service-issue iPad with modern flight planning software and safety information. But the trap of VFR into IMC still lurks, particularly in the hills. Only RNAV / RNP-based low-level routes and ‘Point in Space’ approaches (with matching equipment and published procedures) can improve safety. We are still a miles away from that in India.
The Russian-made Mi-17 V5s were ordered in two tranches between 2011-2018, totalling 150, under the IAF’s Medium Lift Helicopter program. Since their induction, there have been five accidents (three fatal) in the V5 fleet, including one that was accidentally shot down by IAF’s own air defence during the Indo-Pak air skirmish on Feb 27, 2019. Contrary to speculation that arose soon after the crash, the track record of IAF V5s have been fairly safe & consistent, save for the odd crash enforced by human error. The IAF crew are trained & aircraft is well equipped to fly under Instrument Flight Rules (IFR). But IFR rules cannot be directly applied to such ‘VFR-only’ helipads, especially if they encounter instrument meteorological conditions. Sadly we don’t yet have a silver bullet for the deadly cocktail of bad weather and hills. Remember the Kobe Bryant S76B crash near Los Angeles in 2020?
IAF has not yet reported any reasons for the crash. It is a matter under investigation and nothing can be ruled out. However, any abnormal situation or failure can extract a heavy price in the hills. For example, an engine failure at high altitude may force the chopper to ‘drift down’, thereby reducing terrain clearance. At the other end, the crew may reach a physiological or helicopter performance ceiling when attempting climb to route safety altitudes. There is also no clear cut solution to an abnormal situation that may enforce a ‘land as soon as possible’ or ‘land immediately’ landing guidance. The helicopter pilot juggles around with far too many variables while flying in the hills. Often the best laid plans can fail.
Maintain calm, avoid speculation
The IAF has ordered a court of inquiry into the accident. No probable cause has been mentioned in the updates as of Dec 9. The helicopter was fitted with a CVR and FDR though it is not known whether the same has been retrieved intact from the wreckage. While we await the inquiry report, it would be proper to avoid speculating or fanning conspiracy theories. The tendency towards unregulated and unethical sharing of graphic videos and photos in the aftermath of any accident also needs to be curbed. It is immensely unkind to the victims and their families. This dark side was again on full display yesterday, as it was during past crashes (Suryakiran crash at Aero India 2019, Feb 2019 Mirage crash at HAL Bangalore, Budgam shootdown, etc).
My deepest condolences to the bereaved families. Blue skies.
(An edited version of this piece was first published as an op-ed by The Quint. You can access that here.)
©KP Sanjeev Kumar, 2021. All rights reserved.
About the Author
Kaypius is a former naval aviator, experimental test pilot & graduate of 61st Staff Course at DSSC, Wellington. He is dual ATP-rated on Bell 412 & AW139 helicopters and a synthetic flight instructor on ALH Dhruv. Over 90 of his articles have been published in magazines, journals and news media in India and abroad. He enjoys being ‘full-time aviator, part-time writer’ and blogs at https://kaypius.com/. He can be reached at firstname.lastname@example.org or on Twitter @realkaypius. Views are personal.