Emergency Flotation Systems (EFS) Saves ALH Dhruv, But Why Did It Happen

ALH Dhruv MkIII Successfully Saved by EFS

Some  10 days ago ALH Dhruv MkIII operated by the Indian Navy was successfully ditched in the waters of the Arabian Sea thanks to the skills and timely action of the pilot that saved a lot of lives and the precious machine as well after it lost power. A couple of days later the rotary wing aircraft was successfully recovered and saved thanks to an Emergency Flotation System (EFS). So what is an Emergency Flotation System (EFS)?' 

Emergency Flotation Systems (EFS) 

Emergency Flotation (EFS) are emergency systems installed on commercial and military rotary wing aircraft that help to prevent the airframe from sinking in water in the event of a crash landing on water. The EFS is packed within spaces inside the airframe or as externally mounted packs on the aircraft. The floats are inflated using gas stored in pressurized cylinders carried on board the aircraft. 

In the case of helicopters, upon hard landings, the lower plexiglass bubbles in the nose section frequently break. Watertight hull integrity is usually rapidly lost followed by or concurrent with the aircraft rolling over. The EFS helps to save lives as the aircraft rolls over and rapidly fills with water because the nose sinks first trapping personnel in the aft cabin.  As the aircraft rolls over, rapidly filling with water and sinking nosedown, especially at night it becomes impossible for occupants to escape/swim outward against inrushing water and egress successfully. EFS is designed to facilitate the escape of personnel as well as save the airframe from disintegrating.

In the case of helicopters, an EFS is activated upon an emergency landing of the aircraft on water, which helps prevent at least the sinking of the aircraft, characterized by a capsizing avoidance buoyancy system. The capsizing avoidance buoyancy system is activated if predetermined activation criteria are satisfied and only after activation of the EFS upon an emergency landing of the aircraft on water, to prevent capsizing of the aircraft.

In an EFS, the most rapid inflation is provided by pressurized helium although some float systems use helium blended with other gases such as nitrogen to slow down the inflation rate.

History

By 1979, United States Navy and Marine Corps CH-46 Sea Knight helicopters were involved in 64 emergency landings on water. Of the 64, 47 helicopters sunk after crash landing, killing 75. A study estimated 50% of those fatalities could have been prevented if helicopters were equipped with EFS. As helicopters have a higher center of gravity due to the high-mounted engine and transmission, even if they are naturally buoyant in water with hatches secured, they will tend to overturn in heavy sea conditions.

EASA CS-29 and EASA CS-27 define airworthiness standards for rotary wing aircraft, according to which rotary wing aircraft must be equipped with the EFS.

What Next?

The type-certification of helicopters to withstand the undesirable consequences of ditching does not necessarily prevent such consequences. The EFS fitted is often damaged by the ditching impact and rendered wholly or partially ineffective.

Ways of improving the crashworthiness of EFS were also considered. Many say that an EFS should be manually armed for all overwater arrivals and departures and where practicable activated automatically in all water impacts even when not armed. Such an Automatic Float Deployment System (ADFS) adds additional functionality to an EFS and was the subject of one of the 27 Safety Recommendations made as a result of the UK AAIB Investigation into the inadvertent descent into the sea by an EC225L2.

Another way of increasing the crash-worthiness of the EFS is the installation of additional floats to ensure that if the helicopter/aircraft does not remain upright, perhaps because of float damage or sea conditions, it will lie on one side rather than capsize. It should be noted that a multiplicity of buoyancy systems with more or less operator-independent inflation logic already exists. This multiplicity of buoyancy systems relates, however, not necessarily to capsizing avoidance buoyancy systems, but more broadly to buoyancy systems in general.

This requires an air pocket to comply with the provision of a suitable capsizing avoidance buoyancy system such as a roof-mounted inflatable flotation device or float bag, in addition to a normal EFS. Such a roof-mounted float bag is located in a rotary wing aircraft comparatively close to the respective main rotor blades of an associated main rotor and it is specifically needed when, upon an emergency landing of rotary wing aircraft on water, the sea state is above-predetermined emergency flotation system limits of EFS of rotary wing aircraft. This helps avoid rotary wing aircraft going into a capsized position.

However, an unintended release of the capsizing avoidance buoyancy system during the flight of rotary wing aircraft because of a system error must be avoided as otherwise, the inflated float bag may get in contact with the rotating main rotor blades and damage or rupture the rotating main rotor blades, making a crash of the rotary wing aircraft inevitable. Furthermore, non-activation of roof mounted float bag in successive required actions upon an emergency landing of rotary wing aircraft on water may be caused by the unconsciousness of an aircraft crew, resulting in capsize of the helicopter despite the provision of the capsizing avoidance buoyancy system. Therefore, an applied inflation logic for the capsizing avoidance buoyancy system must be safe and reliable and should, preferably, be operator-independent.

India’s MH370

                                                   

Malaysia Airlines Flight 370 was a scheduled international passenger flight that disappeared on 8 March 2014 while flying from Kuala Lumpur International Airport to Beijing Capital International Airport. The crew of the Boeing 777-200ER aircraft last communicated with ATC around 38 minutes after takeoff when the flight was over the South China Sea. The aircraft was lost from ATC radar screens minutes later but was tracked by military radar for another hour, deviating westwards from its planned flight path, crossing the Malay Peninsula and the Andaman Sea. It left a radar range 200 nautical miles (370 km) northwest of Penang Island in northwestern Peninsular Malaysia. Despite international search efforts for years all 227 passengers and 12 crew aboard were presumed dead, and the disappearance of Flight 370 is still a mystery as to where did the plane go.

In the same way on 22 July 2016, an Antonov An-32 twin-engine turboprop transport aircraft of the Indian Air Force disappeared while flying over the Bay of Bengal. The aircraft was en route from Tambaram Air Force Station in the city of Chennai on the western coastline of the Bay of Bengal to Port Blair in the Andaman and Nicobar Islands. There were 29 people on board. Radar contact with the aircraft was lost at 9:12 am, 280 kilometers (170 miles) east of Chennai. The search and rescue operation became India's largest search operation for a missing plane on the sea in history. Yet after a futile search on 15 September 2016, the search and rescue mission was called off; and all 29 people on board were presumed dead and their families were notified. Where is the aircraft still remains a mystery? If there was an Emergency Locator Beacon (ELB) active, the downed aircraft could have been easily located.

In the same way, a Dhruv mk4/Rudra WSI helicopter of the Army with a pilot and co-pilot on board went out of control and crashed into Ranjit Sagar dam at village Purthu in Basohli tehsil of Kathua district on August 3, 2021, after taking off from Mamun In Cantonment in In Pathankot for security recce ahead of Independence Day celebrations and drone attacks. Twelve days later, the body of Lt Col AS Baath, one of the pilots onboard the ill-fated helicopter, was recovered but the body of the co-pilot was recovered after several days more.

If EFS was available the helicopter would have remained afloat for a few hours at least saving precious lives and more importantly precious flying platforms. 

How to Avoid 

1. Make use of EFS compulsory for any rotary aircraft that is assigned to fly over water for whatever type of mission, be it EW/CASO/CASVAC/MEDVAC/CSAR/RC/TRS.

2. Make use of the EFS part of SOP along with ELB any aircraft (rotary/fixed) be it manned or unmanned (drones) that are assigned to fly over water either permanently or temporary basis.

3. EFS can also be used if needed on heavy amphibious armored vehicles of the army, and air force in case they get stalled in the water.

Why Dhruv MkIII Lost Power

After ALH Dhruv MKIII lost power and was ditched but saved thanks to EFS some 10 days ago; the armed forces who operate any variant of ALH Dhruv grounded the helicopters, be it Indian Army, Indian Navy, Indian Air Force, Indian Coast Guard, and Border Security Force. This was done ostensibly to do a thorough check-up of the helicopters before they are allowed to fly again.

Since then some Dhruvs have been allowed to return to the air, but those of the Indian Navy and Indian Coast Guard still remain grounded. Here lies the problem, as why the Dhruv MKIII lost power in 1st place has still not been made public. If India wants to market the ALH Dhruv to international markets, it is very important that the manufacturer at least comes out with clarification as to why and what happened. This opaqueness can damage the export prospects of the helicopter.