An Indian Air Force (IAF) helicopter with 14 persons on board crashed into the hills near Coonoor, Tamil Nadu, in southern India, around 12:20 PM (IST) on Wednesday, 8 December 2021. The Russian-made Mi-17 V5 helicopter ex-IAF’s 109 Helicopter Unit (109 HU) had taken off from the Air Force Station, Sulur, to the military cantonment at Wellington in The Nilgiris (Blue Mountains), when it crashed about ten miles short of the destination.
It is an unprecedented loss of the highest-ranking officer in the Indian military. The crash takes away India’s first Chief of Defence Staff (CDS) General Bipin Rawat, his wife Madhulika Rawat, four crew, the general’s defence attaché, staff officer, liaison officer and five personal security officers. The Indian Air Force (IAF) confirmed 13 deaths by Thursday evening. The lone survivor, Group Captain Varun Singh, directing staff at Defence Services Staff College, has been admitted to the military hospital at Wellington with grave injuries. I hope and pray that he makes it.
I have vivid memories of a sortie I flew along that route in 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 and accident investigation, the nuances of helicopter performance. Though “performance” seems unrelated to the latest tragic crash, I write this piece with a heavy heart to inform the lay reader about the nuances of weather, topography and flight rules for helicopter-flying in the hills.
Flying Slower Than Usual
Gen Rawat was headed for a guest lecture at the nearby Defence Services Staff College (DSSC) at Wellington. The 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 and tea estates.
The peace and calm are occasionally broken by a passing helicopter landing at WGC.
Locals are used to helicopters that appear periodically overhead, so much so that they remember accurately the route the choppers follow. On 8 December, 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 the golf course at the Wellington Gymkhana Club (WGC), Coonoor, in The Nilgiris, has a helipad with a 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 fewer than 50 miles that would take a Mi-17 V5 about 30 minutes along a predetermined route, which military crew have been flying for decades. The helipad is approximately at an elevation of 6,000 feet, with hills and dense forests all around.
Such flights are undertaken under ‘Visual Flight Rules’, or VFR, which implies “see and avoid”. Most civil flights and fixed-wing aircraft fly under IFR, or Instrument Flight Rules. Most military helicopters operate on VFR at low height, particularly in 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.
Winter Season Can Get Tricky
Coonoor, for the most part, has lovely salubrious weather with clear visibility and sparkling clear skies. However, during the winter season, low drifting clouds, fog and mist often roll in unannounced, reducing visibility that can push “see and avoid” VFR flights into peril. Also, technical issues – if any – 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 the 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 Air traffic control (ATC)
There are practical limits to options one and two, especially in the hills or over ‘hostile terrain’. However, if the destination is a helipad, like the WGC, with no IFR aids or published IFR procedures, option three 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.
A Deadly Cocktail of Bad Weather & Hills
The Mi-17 V5 is a robust twin-engine helicopter with an 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 flight planning software and safety information. But the trap of VFR into IMC still lurks, particularly in the hills. Only GPS- or RNP (Required navigation performance)-based low-level routes and RNAV (area navigation) approaches (with matching equipment and published procedures) can improve safety. We are still miles away from that in India.
The Russian-made Mi-17 V5s were ordered in two tranches between 2011 and 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 the IAF’s own air defence during the Indo-Pak air skirmish on 27 February 2019.
Contrary to speculation that arose soon after the crash, the track record of IAF V5s has been fairly safe and consistent, save for the odd crash enforced by human error. The IAF crew are trained and aircraft are 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?
Too Many Variables
The 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 a 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 9 December. The helicopter was fitted with a CVR (Cockpit Voice Recorder) and FDR (Flight Data Recorder). 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 an 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, such as the Suryakiran crash at Aero India 2019, the February 2019 Mirage crash at HAL Bangalore, and the Budgam shootdown, among others.
My deepest condolences to the bereaved families. Blue skies.
(The author is an ex-navy experimental test pilot. He is dual ATP-rated on Bell 412 & AW139 helicopters and a synthetic flight instructor on ALH Dhruv. He can be reached on Twitter @realkaypius. Views are personal. This is an opinion piece and the views expressed above are the author’s own. The Quint neither endorses nor is responsible for them.)
(At The Quint, we are answerable only to our audience. Play an active role in shaping our journalism by becoming a member. Because the truth is worth it.)