Ditching: Helicopters: Ditching an aircraft into the sea, a river, or a lake, is a manoeuvre that, by definition, cannot be practiced and may be extremely hazardous.
It is only contemplated when no other realistic option remains in an emergency or, in the rotary case, imminent emergency situation.
For helicopters, ditching may be prompted by a sudden-onset emergency or where continued safe flight to the nearest designated landing location or even the nearest suitable land is not assured; it will often be accompanied by considerable structural conditions outside of the “norm”, such as tail rotor failures or very high vibrations. All of these contribute to the already considerable pressure of getting the aircraft down and evacuating it.
Even if the Sea State is slight, there is a strong possibility that a helicopter will fail to remain upright and/or will sink rapidly.
A controlled ditching might be made in anticipation of a loss of control or its actual onset.
Other potential causes of an impending loss of control which could prompt a decision to ditch include uncontrollable and developing fire or structural failure indications of imminent power transmission failure or loss of rotor integrity for which the procedural response is ‘Land Immediately’.
Helicopters may also need to ‘land immediately’ for other reasons, including the failure of a single engine.
Ditching a Helicopter (“Power On”)
Whilst there are many variables in any evolving incident, a controlled “power on” ditching will be considerably easier than a “power off” autorotation to the sea; an autorotation to an angry sea needs immediate transition to trained automatic actions, as time is extremely limited.
Ultimately, success will be determined by the rigorous and comprehensive training that should be undertaken on a regular basis.
It cannot be stressed enough that thorough and ongoing training is the key to survival in these (and most) circumstances, and that crews should regularly take the opportunity to discuss situations and procedures when possible.
Few emergencies ever go according the script, and ditching’s are no different. The priority should be, as always, “fly the aircraft”; training and procedure will get you into the water in one piece.
Helicopters often fly at relatively low altitudes, and generally a decision to ditch (apart from impending fuel starvation) tends to be reached fairly quickly as the aircraft malfunctions around us.
Good CRM and repeated training, is the key.
As it is for crew, so it should be for our passengers.
Inverted in a hull rapidly filling with water is not the time to ponder the correct way to activate one’s re-breather or open and exit with window/hatch.
In an ideal world this should be done without conscious thought, as a direct result once again from good training and a positive will to survive.
Facilitating Rescue after ditching
- Ensuring Awareness’ of the Emergency.
- If in a radar environment, a MAYDAY transmitted on the ATC frequency in use should suffice.
- Otherwise, distress calls should be made 121.5 or allocated UHF or HF frequencies and (if time permits and not at the expense of more pressing actions) A7700 should be selected on the transponder.
- If feasible, operate Emergency Location Transmitters (ELT).
- Position. Ensure that any agency which has responded to the MAYDAY declaration is made aware of the likely location of a ditching.
- (Bear in mind a helicopter committed to ditching will not travel very far from its initial descent point.
- Depending on altitude, the distance will only be a matter of a few miles at best.)
- Rescue Agencies include ATC, other aircraft or boats and, where possible, directly to the emergency services such as the Coastguard.
- Shipping. Survival after a ditching will often depend on how quickly you are picked up so unless it is going to be possible near an offshore platform then ditching within line of sight of any vessel which can be located makes a lot of sense,
- The Helicopter Emergency Floatation Systems (EFS) must be armed as soon (within the limitations of the flight manual) as it becomes obvious that a ditching is inevitable.
- Cabin Preparation. In the time available, passengers should be forewarned of the impending ditching as soon as possible to allow them a mental rehearsal of the evacuation and survival techniques which will be needed.
- This may be accomplished by the flight crew but cabin crew (if present) should be prepared to supplement any announcement and, if necessary, provide a complete briefing.
- Final Approach and touchdown. Determine the best direction to approach the ditching location in relation to sea state and wind direction.
- Unless the wind is calm, the chances are that the direction of the wind will differ from that of the swell.
- Where the swell is more marked, it may be advisable to ditch along the swell accepting a crosswind component and the higher touchdown speed, thus minimising the potential for nosing into the face of the rising swell.
- Radio Altimeter height callouts from the Co Pilot are likely to be of assistance both by day and by night.
- The overriding objective should be to maximise the chances the helicopter remaining upright.
- Clearly a low forward speed, low rate of descent and appropriate pitch attitude will all be of importance.
- Monitoring the horizon if possible at touchdown, rather than the sea at one’s feet, should reduce the tendency to “hunt” the swell, facilitating the landing.
- In the dark, the extent to which external lighting may assist touching down will be a matter of judgment based on the prevailing circumstances.
- Since judging sea state at night may be difficult, a power-available ditching will allow a low-level pre-inspection of the sea surface and may be worthwhile.
- Evacuation. Once on the surface, the engines should be shut down if running and the main rotor stopped.
- In most cases, Rotor Brake should not be used as the transfer of energy thorough the aircraft could be enough to capsize it.
- Once the rotor has stopped, the occupants should be instructed to begin evacuation.
- The primary objective will be to deploy and board the life rafts carried without undue delay.
- After a headcount, these should be detached from the helicopter to avoid being dragged down should the helicopter then capsize fully – but attached to each other if more than one is being used.
- Where a life raft “long line” has a shear type connection that is designed to tear free if the helicopter sinks, remaining attached to the helicopter can be considered, to remain close to the scene of the accident where SAR (Search And Rescue) will begin its search and where surface oil/debris and aircraft provide added visual cues for the searchers.
- There will be a survival knife in the life raft’s kitbag if it becomes necessary to cut free from the aircraft.
- In all cases, if there is more than one life raft they should be attached to each other.
- Deploy the life raft sea anchor to improve its stability and, as early as possible, administer seasickness tablets to everyone; it is almost inevitable that when one person vomits the rest will follow, increasing the survivors’ fatigue and dehydration and reducing their morale.
Post Ditching Survival
Training and procedure may get you down into the water safely; leadership and strong mental attitude is needed to get out.
The environment the survivors will now find themselves in will certainly be unfamiliar and unexpected and may be extremely hostile.
Continued survival will depend on the water and air temperature, the wind and sea state, the physical and mental condition of individuals, the clothing worn and the availability of useful survival equipment amongst many other things.
Swift location and rescue may well be of crucial importance.
For all occupants of Helicopter offshore flights, prior familiarisation with and recurrent training in survival equipment, evacuation procedures and maritime survival is of paramount importance; there will not be an opportunity to practice in a live accident.
Training for Ditching and the Aftermath
Full Flight Simulator practice of ditching by pilots is impossible because there is no data with which to meaningfully program the simulator.
For Helicopter crew regularly operating offshore and their passengers, realistic practice of some aspects of evacuation and post evacuation scenarios is available and usually is a significant part of training/familiarisation.
Regular training in helicopter underwater escape should continue throughout aircrew’s careers and is equally important for passengers.
Although all helicopters operating offshore public transport are likely to be equipped with emergency floatation systems and Automatic Deployment Emergency Locator Beacons and the occupants provided with some form of survival suit and emergency breathing equipment, this preparation for survival after ditching addresses the need for prompt evacuation before any capsize of the floating helicopter.
The installation of floats towards the top of the fuselage could clearly sustain a helicopter that had rolled on the water 90° to the vertical. However, such modifications carry significant technical challenge to avoid the risk of an inadvertent inflation interfering with the main rotor and creating an accident in the first place.