Follow Us on Google
Louis Ibah
On February 2, 2018, an Agusta Westland AW139 chopper operated by Caverton Helicopters Limited with registration number 5N-CML departed the Murtala Mohammed International Airport, Lagos at about 07:26am for the Nnamdi Azikiwe International Airport Abuja to conduct a chartered VIP flight from Abuja to Okene via Kabba and then return to Abuja.
However, while the first leg of the flight from Lagos to Abuja was successful, the flight from Abuja to the Kabba Football Stadium proved unsuccessful as it crashed while attempting to land. Although no life was lost, the accident nonetheless aroused public interest. Vice President, Yemi Osinbajo and his political entourage were guests on the flight.
Allegations of sabotage reigned everywhere: who wants Osinbajo dead?
The Accident Investigation Bureau (AIB) quickly swung into action and assured Nigerians it would unravel the cause of the crash.
As expected about 11 days after the crash, the AIB released its preliminary findings linking the crash to a ‘brownout’ incident experienced by the aircraft pilots minutes before landing. It was the first time in the country’s air crash history that such a word would be used to reflect the cause of a mishap.
What is brownout in aviation?
Brownout in helicopter operations is an in-flight visibility restriction caused by dust or sand in which the flight crew looses visual contact with nearby objects that provide the outside visual references necessary to control the helicopter near the ground.
Over the years, landing helicopters on clean concrete or cement pavements or helipads have proved to be the safest. But by their nature and the kind of services they render, helicopters are also designed to land in open fields and deserts as well. But it is in landing on the latter that pilots risk encountering brownout a condition caused by dust generated by the helicopter rotor blades (propellers) spinning at very high speed to generate lift and thrust to fly as well as the control that allows the helicopter to move laterally, make turns and change altitude.
Sadly, in sandy environment like the Kabba Football field the sand or dust particles that began to pick up at 50 feet enveloped the helicopter cockpit and cabin at 20 feet above the ground and at swept up in the rotor downwash and obscure the pilot’s vision of the terrain. If a pilot cannot have visual contact with the ground where it is landing, then he’s bound to crash-land. Landing helicopters in brownout conditions is considered the most dangerous and Herculian task for helicopter pilots. Globally, it is costing the industry huge amounts of money and – more importantly – lives of pilots and crew. One pilot described this phenomenon as ‘essentially flying a controlled crash into the ground with no outside reference’.
Indeed, the issue of helicopter brownout has long been a known problem, but in the recent past it has become a really expensive problem for helicopters involved in operations in desert war-torn countries like Afghanistan and Iraq. The US Army alone has lost or damaged 27 helicopters in brownout mishaps.
The US Air Force Institute of Technology stated that the US Department of Defense (DoD) attributes over $100 million in total costs per year to brownout mishaps, and it found brownout accounted for 65 per cent of non-hostile fatalities during hover and low speed flight. Globally, about $400million is lost to brownout helicopter mishaps.
AIB findings on Caverton
The AIB in its preliminary findings acknowledged that the Caverton helicopter had a valid certificate of airworthiness meaning that there was nothing wrong with the aircraft. The flight crew were properly licensed and adequately rested to operate the flight.
The AIB however stated that Caverton Helicopters had failed to conduct the site survey of the landing field at Kabba stadium prior to the flight which is a necessary safety requirements for landing in an unapproved aerodrome.
“Caverton Helicopters did not carry out safety and risk assessment of the landing area prior to dispatch of the flight and the helicopter hovered to land in a brownout condition,” the report stated. “During cruise at 5,000 feet and at about 10 minutes to touchdown, the crew noticed the flight recorder light on the Crew Alerting System (CAS) come on. The crew briefed passengers on landing in brownout conditions and used the company’s brownout landing procedures. During the landing, at about 50 feet to touchdown, a heavy brownout arose and enveloped the helicopter and the crew lost visual contact with the ground. At about 14:34hours, the helicopter touched down hard on the right side of the main landing gear and rolled over to the right.
The helicopter was substantially damaged. But the crew had carried out emergency landing procedure which included immediate engines shutdown, fuel shut off, battery switch off, and generators switch off. All occupants of the helicopter were evacuated uninjured,” the AIB report concluded.
Way out
Once an helicopter is not heading to land in a standard approved helipad or concrete ground, the operator must first carry out a site survey and must also do a proper safety risk analysis before dispatching any helicopter to carry passengers to such an unapproved landing pad like the Kabba Football field in Kogi where the Caverton Helicopter crashed.
There is also the need by operators to strengthen pilot awareness on the possibility of flying into brownout conditions and for them to adhere to standard manuals and procedures in operating into an area that lacked an approved aerodrome.
Lastly, passengers or clients who hire helicopters to fly them to such unapproved locations also have the right to demand that the operator show evidence of having carried out a risk assessment of where they are flying to before boarding the aircraft. The task of ensuring safe flight operations should not be left solely for regulators.
