What is autorotation, and how do pilots get out of it?
Put simply, an autorotation is what the pilot needs to perform when a helicopter loses power from its engine(s), during which the main rotor is driven only by aerodynamic forces. The engine is disengaged from the main rotor system, and the rotor blades are driven solely by the upward flow of air.
Losing power is frequently cited as a contributing factor in helicopter accidents, as is pilot error. So, it follows that practicing for these events should help mitigate the risk of a fatal incident.
Rogers and Asbury, in their report ‘A flight training simulator for instructing the helicopter autorotation maneuver’ (enhanced version), note that ‘there is no single ‘right way’ to perform an autorotation’ – every helicopter type will be different. And for HEMS and SAR pilots working across multiple platforms, being ready for such a maneuver is vital – and there is a lot going on in that moment when power is lost. They have a few seconds to react and take necessary action to recover control, lower the collective to maintain rotor RPM, add right pedal to prevent yawing, pull the cyclic aft to reduce airspeed and increase airflow through the rotor disk, select a landing zone, and determine how to maneuver for a landing into the wind. Muscle memory is therefore essential to do it right.
Current training methodology
Training comes in two forms – live and simulated. Some fairly obvious pros and cons are related to each approach, but let’s have a quick rundown:
Advantages of simulator training:
• Enhanced availability of the service
• More opportunities to learn from mistakes
• Zero risk to pilot or aircraft
• Environmental benefits such as reduced emissions and noise
• Fewer aircraft hours.
However, there are also disadvantages:
• Initial cost of buying the simulator
• Potential simulator sickness for users
• Potential for low-quality programs not offering sufficient fidelity to the pilot, whether motivational, psychological, physical or functional.
Alex Pollitt, a SAR pilot with the Spanish Coastguard, noted the difference in methodologies between civil and military operations: “Undoubtedly, as an ex-military pilot, the opportunities for training in the civil sector are fewer, and less emphasis is placed on their importance. In military training, significant time was dedicated to actual engines-off landings during initial training, and throughout the time I was flying in the military, a variety of autorotations were practiced in the aircraft at least weekly.
“My experience since leaving the military of training autorotations in the simulator (which can't be done in real life) is that you generally get just one or two attempts to have a go, squeezed in around other training imperatives during your simulator time.” There are several problems with this approach, as Pollitt pointed out:
• Practice is usually pre-briefed, so the pilot knows an autorotation is coming and, to some extent, can mentally rehearse the actions (losing the effect of startle and surprise)
• When the autorotation doesn’t work out or the flare at the bottom is imperfect, resulting in a ‘crash’, it is more often than not excused, because of the challenges getting it right in the simulator. Instructors move on to other things due to time pressures, or because they do not think it worthwhile to repeat (presumably due to a lack of belief in the training value).
Strengths and weaknesses of sim training options
Rotorcraft safety: A Simulator-based Training Perspective, published in 2021, sought to investigate how powerful the process can be for autorotations. While we do not have space in this article to go into too much depth about this illuminating piece of research, the conclusion is telling: ‘The two experiments on autorotation showed that pilots trained in high resource demanding conditions develop a more robust control technique, that can be easily adjusted according to the helicopter handling characteristics, after a short adaptation phase. This may result in a better capability to handle emergencies like engine failures in the real world, where the actual situation may easily divert from the training scenario, because they can quickly adapt to unexpected conditions.’ The authors went on to suggest that current simulator training syllabuses for autorotations be updated to include different helicopter configurations and characteristics.
All the research points to similar outcomes – simulator training offers opportunities for pilots to hone their skills and practice otherwise risky and potentially expensive maneuvers. However, there is always room for improvement. AirMed&Rescue spoke to HEMS and SAR pilots about their experience using simulator training for autorotations.
Valuable tool in the box
Mike Biasatti, a HEMS pilot in the US, shared his views on simulator training, highlighting both the virtues and potential pitfalls of current software on offer: “Flight simulators are an amazing training tool. Modern ones afford a platform where any and all emergency procedures can safely be demonstrated and presented to the pilot to train recognition and recovery. For instrument training, should the pilot make a mistake, the examiner can simply freeze the sim, place the aircraft several miles back and proceed with the training/evaluation.”
Richard Butterworth is Head of Training for Kestrel Aviation in Australia, and his instructional experience ranges from single-engine military training to the latest-generation flight simulators. He noted that the recent advent of virtual reality (VR) has presented new cost-efficient options, affording increased opportunities for training exposure at a lower cost, thereby expanding the pool of participants and enabling cost-effective sequence repetition, which is a fundamental principle of elemental skill assimilation and ongoing proficiency.
The type of helicopter being used commonly in HEMS, SAR and aerial firefighting roles are typically now more medium- and heavy-lift models and this, said Butterworth, ‘supports a heavier emphasis on simulation’. “These aircraft are generally multi-engine, supported by redundant systems with an increasingly digital user interface,” he explained. “Therefore, the management of these aircraft in both nominal and non-nominal situations becomes the dominant training focus and, as such, simulation is the ideal resource to conduct effective training, particularly in the multi-crew environment.”
For larger organizations, investment in a full motion simulator to practice pilot at the controls. Flight simulators get you to about 95 per cent of everything you need, but to have a true sense of what it would feel like, sound like, and how the aircraft will react, takes time in the actual aircraft. As technology advances this may change, but today I think it’s hard to duplicate the internal impact you’ll feel if that engine stops in an aircraft, and how that affects your reaction time, situational awareness, and preparedness over any number of different types of terrain and at typically lower altitudes.”
The interpretation of flight characteristics and performance through feel (proprioceptors) is an essential sub-element in the achievement of competency for single-engine failures and autorotative recovery. The recognition of failure symptoms and pilot initial actions, descent profile adjustment to achieve a safe forced landing area, but most significantly the terminal execution, rely heavily on the feel of the aircraft, in addition to visual and vestibular sensory systems. Timely reaction to aircraft attitude and performance relies on the successful interpretation of these three sensory systems.
“Another key factor is vulnerability,” said Butterworth. “There is no doubting the power of simulation and its persuasive sense of immersion. I often recount instrument navigation sorties where I found myself balancing my inner ear pressure on descent, even though the simulation device never left the ground. That said, within one’s mind there is a default level of comfort, knowing that you are safe within the simulated environment. The conduct of live aircraft training deliberately places the aircraft and crew in a vulnerable state which, while mitigated, must be managed to affect a safe recovery. This intrusive knowledge of susceptibility remains a fundamental element in the management of human performance and its ability to navigate and arrive at a successful outcome under duress.”
Brandon Laird, Chief Pilot for Colorado Highland Helicopters, said that while simulators are a great tool, there are two primary issues in replicating autorotation and other dynamic maneuvers: “The first is the ability to provide accurate representation of the height above ground and other visual cues through field of view, necessary to time the flare and touchdown portion of an auto or power-off landing.” The other involves the physics modeling to accurately represent the aircraft response and transfer cues of that response to the pilot: “Those responses include changes in attitude, engine and rotor RPM, control response or feel and oscillations or vibration. These cues can be transferred to the pilot in a variety of ways, and both the modelled response and cues are usually more closely represented as the complexity (and cost) of the simulator increases," he said.
What can simulators do better?
Manufacturers will need to leverage new technologies to offer better modeling of aircraft response in the full envelope of flight configurations, more accurately transferring the cues provided by the aircraft to sim pilot. “Until recently,” said Laird, “the ability of a cost-effective, light helicopter simulator to accurately replicate and transfer the response and cues necessary for effective training, in more dynamic maneuvers, has been limited.
“The full-flight simulators capable of enough realism to effectively train these more dynamic maneuvers were generally cost-prohibitive for light helicopters and certainly for initial flight training. As available technology advances, accurate aircraft physics data has become feasible to obtain and transfer to more affordable simulator platforms and the viability of VR glasses eliminates the field of view limitations. VR may offer increased benefits beyond the actual aircraft in providing eye-tracking data to better understand the response of pilots in training and emergency situations.”