Blog Nitros

From first successful flight by Wright brothers to Airbus A380, and from first flight of Sikorsky’s VS-300 to Boeing’s AH-64 Apache, the aerospace industry has made huge advances in both fixed-wing and rotary-wing aircraft.
Fixed wing allows an airplane to fly by generating lift through vehicle’s forward airspeed. On the other hand, helicopters do not need the vehicle’s forward speed; the lift is generated by the spinning rotary wings. Helicopters have the ability to vertically takeoff and land that allows them to takeoff and land virtually anywhere and access remote areas, however, it has limited capability in speed and range when compared to a conventional fixed-wing airplane. The ambition to combine best of both worlds i.e., an aircraft that has VTOL (Vertical Takeoff and Landing) capability of a helicopter, and speed and range of a fixed-wing airplane, led to the development of several hybrid configurations. Tiltrotor is one such example and is the only rotary convertiplane in service.
Tiltrotors are the ultimate transformers, because not only they transform from one configuration to another during flight, they are also transforming the future of aviation industry. Most of the modern transformative VTOL aircraft, such as Uber Elevate, Lilium jet, Vahana from A3 by Airbus, Project zero by Leonardo helicopters, are inspired by tiltrotors in one way or another.
The hybrid configuration of these transformative VTOL aircraft allows them to operate over a broad flight envelope and thus present a lot of opportunities. The ability to hover like a helicopter and at the same time to fly at relatively high cruise speeds and range make them an effective point-to-point fast means of transportations. Their multi-role capability not only make them ideal for urban air mobility but also for energy & medical services and search & rescue missions.
However, the multi-role capability with large flight envelope pose various technical challenges in designing an aircraft to perform adequately over a wide range of aircraft configurations. These technical challenges include: dramatic change in control strategies with flight conditions and aircraft configurations, Rotorcraft Pilot Coupling (RPC) and structural loads.
In conclusion, the modern rotary VTOL aircraft will be half airplane and half helicopter that will fly long distances at higher speeds. In order to ensure safety and take full advantage of the hybrid capabilities of future transformative VTOL aircraft, various technical challenges need to be addressed at the design phase of the aircraft.

It happens to everyone that in some conditions of loading to your body, the body couldn’t tolerate the situation and it will be injured. Body of older persons or individuals with a previous injury are more vulnerable and they are at greater risk of injury. So how you realize that your body is in danger? The nervous system that is distributed all over the body will recognize the pain and brings all the data to the brain and then after analyzing the data your brain finds out what has happened to the body and will decide the next step and will trigger an immediate command before the failure of the body. For example, if body experiences pain inside the knee and this pain signal becomes amplified, the next step is to sit, otherwise it could cause the body to fall down.
Now consider that helicopter structure could sense what is going to happen like human body and could make decision before a complete failure. It means that the structure could sense if it has been strained to the point of damage and could reduce its load-carrying capacity, then report that information in real time before the structure’s safety is compromised or in the case of propagation of damage, pilots will be informed how much time he has left for landing. For many years, such a scenario was more like the stuff of science fiction than fact, but today, structural health monitoring (SHM) systems that can perform these tasks are closer to reality.
The damage tolerance and high strength-to-weight ratio of composites have motivated designers to expand the role of advanced materials in aircraft structures. This practice, however, further complicates inspection of flaws before it causes critical situation. As a result, the aviation industry has recognized the need for more sophisticated and more innovative ways to deploy them in situations where complex structural geometries create accessibility limitations that may impede efforts to locate and identify deeply hidden flaws. “The basic idea of SHM is to build a system similar to the human nervous system, with a network of sensors placed in critical areas where structural integrity must be maintained” says Holger Speckmann, who is the Co-Founder of the SHM-AISC (SHM – Aerospace Industry Steering Committee) (Bremen, Germany) [1].
In general, SHM is a method of integrity analysis of an object via real-time measurements of a set of parameters, which characterize the object’s integrity [2]. The main assignment of SHM system is to alert system operator in case of critical structure situation such as fibre strains or breakage and matrix cracks. The other benefit of damage detection is reduction in the cost of maintenance. Operation and maintenance which can account for more than half of a rotorcraft’s total cost, but health monitoring can reduce those maintenance costs by more than 15% and reduce unscheduled downtime by nearly 50%.
The most common measurement quantity which is used to detect the presence of damage is strain. Devices used for this measurement are commonly referred to as ‘sensors’, measuring a value linearly proportional to a quantity of interest such as deformation. Currently, most sensors employed in SHM systems are either optical fibres or piezoelectric devices [2].
Practically, fibre optic sensors form the most useful class of sensors for SHM systems. Employing an embedded FBG sensors for measurement of distributed stress and strain fields of the composite material has significant advantages. First of all, FBG sensors can be easily embedded into materials to provide damage detection or internal strain field mapping. The FBG sensors supposed to be located in fiber optic cable mounted in the sample. Furthermore, the key feature of FBGs sensors is that the information about perturbations is encoded in wavelength. Indeed, this type of sensor has fantastic compatibility with composite [3].
Although SHM is still immature, research and development has already yielded promising results. It will be hoped that in the near future this system could prevent all the accidents cause by structural failure and help to reduce the cost and time of maintenance.
References:
[1] https://www.compositesworld.com/articles/structural-health-monitoring-composites-getsmart
[2] Fedorov A, Lazarev V, Makhrov I, Pozhar N, Anufriev M, Pnev A, Karasik V, Structural monitoring system with fibre Bragg grating sensors: Implementation and software solution, Journal of Physics: Conference Series, vol. 594, issue 1 (2015) Published by Institute of Physics Publishing
[3] Guo H, Xiao G, Mrad N, Yao J, Fibre optic sensors for structural health monitoring of air platforms, Sensors, vol. 11, issue 4 (2011) pp. 3687-3705

Piloting a helicopter is not an easy task. To support the pilot, automated systems like stability augmentation systems, autopilot systems or flight management systems have been developed and used in the aviation domain. While these systems can be a great asset, many issues and potential pitfalls must be considered during their development and design process. This blog post briefly describes some of the more widely known issues with these systems, called “Ironies of Automation”.

Ironies of Automation
The so-called “Ironies of Automation”, as introduced by Lisanne Bainbridge in 1983, describe pitfalls of introducing automation into human control tasks. Originating in the industrial process control domain, the discussed ironies are also applicable to the generalized case of a (complex) technical system being controlled by a human operator. Bainbridge’s paper details a number of problems which arise by reallocating control responsibilities from the human operator to automated systems.
I want to highlight some of the ironies of automation that must be considered when developing and evaluating helicopter automated systems. It is based on Bainbridge’s original paper [1]. Reviews of the current state of these problems are available for example in [2] or [3]. There exist more issues, beside these ironies, that must be considered while designing or evaluating automated systems, which are outside of the scope of this short blog post – interface design principles, which metrics should be used for system evaluation, or additional automation issues like opaqueness and brittleness.

1. Tasks after automation
Often, automated systems are designed for a certain task and specific conditions. While the automation controls the system directly, the human’s task is to monitor the actions of the automation. In case of unanticipated automation or system behaviour, or unanticipated external conditions, the human operator is supposed to take control from the automation and control the system manually/directly, or in a state of reduced automation capabilities. The human operator’s task is no longer predominantly a manual control task, but a supervisory control task. This kind of responsibility allocation leads to several problems.

1.1 Manual control skills
“Physical skills deteriorate if they are not used“ [1]. If the operator must take over after unusual system behaviour, he might not have much experience in manually handling the system anymore. This, in turn, can increase the time-delay and control gain (in case of manual control tasks) of the operator’s response, and lead to longer decision times or “worse” responses. Complicating things further, situations that require human intervention will most likely be abnormal situations which the automation couldn’t handle anymore, requiring not only nominal system control capabilities, but the ability to control the system while it shows abnormal behaviour.

1.2 Cognitive skills
“(…) An operator will only be able to generate successful new strategies for unusual situations if he has an adequate knowledge of the process” [1]. Long-term knowledge retrieval is dependent on frequent use. As the operator is only expected to take over control in rarely occurring unusual situations, he might lack enough opportunities to employ his knowledge, hindering his capability of retrieving his knowledge efficiently. In addition, an operator with mainly supervisory responsibilities will seldom have opportunities to build up a knowledge basis about the system behaviour. Therefore, the operator’s ability to build up, as well as the ability to employ his system knowledge might be impaired by introducing automation.
In addition to long-term knowledge storage, the operator of a complex system keeps short-term system characteristics and system states in working storage memory. This knowledge is used to make predictions about future control actions and their effects. “This information takes time to build up. The implication of this (…) is that the operator who has to do something quickly can only do so on the basis of minimum information” [1]. After taking over from automation, the operator will need some time to acquire knowledge of the system state.

1.3 Monitoring
Humans are not built for the task of monitoring a system. “Vigilance” studies show “(…) that it is impossible for even a highly motivated human being to maintain effective visual attention towards a source of information on which very little happens, for more than about half an hour” [1]. Trying to solve this problem by introducing automated alarms only shifts the problem one level higher (“who monitors the alarm system?”). When automated systems run long enough without incident, it might also induce “automation complacency”, the tendency to trust the automated systems even in situations where human intervention is necessary.
In addition, in cases where the automated system outperforms the human operator in nominal conditions, it can be hard for the human operator to distinguish between appropriate system behaviour and abnormal states. It might be hard for him to understand the system’s actions: in nominal conditions, it performs the task at hand “better”, possibly taking more input data or system dynamics into consideration than the human operator can.

2. Operator attitudes
Introducing automation will affect the skills and tasks of the human operator, but it might also impact his satisfaction with the task at hand and his health. It can be hard for operators to build up and maintain their manual control skills if they are not used (anymore). This can lead to situations as described by [4], where fast process dynamics, a high frequency of actions and inadequate skills/options to control the system correspond to high stress levels, high workload levels and poor operator health.

3. Conclusion
Several “ironies of automation” must be considered while designing automated systems. Inducing automation complacency, vigilance problems or a degradation of piloting skills should be avoided. The existence of these issues warrants the analysis of human-automation interaction in the helicopter domain, to enable the development of resilient and effective automation systems that reliably support the pilot, ideally also in unanticipated situations and emergencies.

Literature

[1] L. Bainbridge, “Ironies of automation,” Automatica, vol. 19, no. 6, pp. 775–779, Nov. 1983.
[2] G. Baxter, J. Rooksby, Y. Wang, and A. Khajeh-Hosseini, “The ironies of automation: still going strong at 30?,” in Proceedings of the 30th European Conference on Cognitive Ergonomics – ECCE ’12, 2012, p. 65.
[3] B. Strauch, “Ironies of Automation: Still Unresolved After All These Years,” IEEE Trans. Human-Machine Syst., pp. 1–15, 2017.
[4] C. L. Ekkers, C. K. Pasmooij, A. A. F. Brouwers, and A. J. Janusch, “HUMAN CONTROL TASKS: A COMPARATIVE STUDY IN DIFFERENT MAN—MACHINE SYSTEMS,” in Case Studies in Automation Related to Humanization of Work, Elsevier, 1979, pp. 23–29.