Assessment of Training Aircraft Crew Exposure to Electromagnetic Fields Caused by Radio Navigation Devices

energies

Article Assessment of Training Aircraft Crew Exposure to Electromagnetic Fields Caused by Radio Navigation Devices

Joanna Michałowska 1,*, Jarosław Pytka 2,* , Arkadiusz Toﬁl 1 , Piotr Krupski 2 and Łukasz Puzio 1

1 The State School of Higher Education, Pocztowa 54, 22-100 Chełm, Poland; atoﬁ[email protected] (A.T.); [email protected] (Ł.P.) 2 Faculty of Mechanical Engineering, Lublin University of Technology, 20-618 Lublin, Poland; [email protected] * Correspondence: [email protected] (J.M.); [email protected] (J.P.)

Abstract: The paper depicts research concerning the value of the electric component of the electromagnetic (EM) energy determined by the NHT3DL meter by Microrad with the 01E measuring probe during a number of flights made by Aero AT-3 R100, Cessna C172, and Tecnam P2006T fixed wing aircrafts and a Robinson R44 Raven helicopter. The point of reference for the recorded measurement was the normative limits of the electromagnetic field (EMF), which can influence a pilot in the course of a flight. Selected studies of the maximum value recorded by the meter was E = 10.66 V/m when landing at an airfield equipped with the VHF (Very High Frequency) omnidirectional radio range (VOR) approach system. Particular attention has been paid to changes in electric field intensity during the operation and their effects on the type of radio navigation systems as well as communication with the airfield control tower. The obtained results were validated in the Statistica 13.3 software for the purpose of a detailed stochastic analysis of the tested values. Results obtained are subject to the mandatory requirements of Directive 2013/35/EU as well as to the relevant regulations in Poland.

Keywords: electromagnetic ﬁeld; aircraft; exposure; air navigation devices

Citation: Michałowska, J.; Pytka, J.; Tofil, A.; Krupski, P.; Puzio, Ł. Assessment of Training Aircraft Crew 1. Introduction Exposure to Electromagnetic Fields The influence of (electromagnetic) EM energy on human organisms is the topic of Caused by Radio Navigation Devices. Energies 2021, 14, 254. https:// research in many research centers around the world. There are no clear criteria for assessing doi.org/10.3390/en14010254 its effects. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) describes guidelines providing protection against adverse health effects related to exposure Received: 5 December 2020 to non-ionizing radiation [1,2]. Preventing undesirable effects on the human organism and Accepted: 31 December 2020 the environment is the main goal of protection against ionizing and non-ionizing radiation. Published: 5 January 2021 The electromagnetic field energy is present in the world around us, but we should focus on its tolerable level. The level of the exposure threshold is necessary for the negative Publisher’s Note: MDPI stays neu- health effects to be present. The limits of the electromagnetic field (EMF) take into account tral with regard to jurisdictional clai- the presence of direct and indirect health effects. They refer to exposure regardless of its ms in published maps and institutio- duration and include the effects of both short-term and long-term exposure [3,4]. nal affiliations. In general, measurements of the electromagnetic field of radio navigation equipment are carried out in function checks of newly installed systems or for diagnostic purposes. In such instances, airplanes with measuring equipment or ground measuring systems are used [5–7]. Copyright: © 2021 by the authors. Li- censee MDPI, Basel, Switzerland. In the literature, studies on the quantitative determination of air crew exposure to This article is an open access article the energy of electromagnetic fields are rare. It is also difficult to find studies dealing distributed under the terms and con- with passenger exposure. The ICNIRP commission undertakes extensive research in a ditions of the Creative Commons At- similar field, however, it is usually only related to the effects of EM field energy on ground tribution (CC BY) license (https:// handling staff [8,9]. creativecommons.org/licenses/by/ Novak (2012) used a Piper PA-34-220T airplane equipped with on-board instrumen- 4.0/). tation together with ground instrumentation for the comparative aerial measurements of

Energies 2021, 14, 254. https://doi.org/10.3390/en14010254 https://www.mdpi.com/journal/energies Energies 2021, 14, 254 2 of 17

the newly installed Instrument Landing System (ILS) at the Zilina Airport, Slovakia [10]. Another example of research in this area is the use of simulation methods to assess the accuracy and operational characteristics of the ILS system [11]. Apart from simple elec- tronic systems, airplanes also have advanced avionics devices. On-board electronics and flight control instruments use most of the electric power distributed by the aircraft’s power system. This is often associated with significant current densities in the power lines, which in turn generate the electromagnetic field of the devices themselves and the entire working space of the aircraft. In addition to the electromagnetic field energy from on-board devices, to which the pilot and passengers are exposed, a number of ground devices for guidance and communication with the airport emit an electromagnetic field [12,13]. The intensity of the electric component of the electromagnetic field for aircrafts crews was related to the guidelines of Directive 2013/35/EU [14], in which reference levels for time-averaged exposures of ≥6 min were given. The directive provides Action Levels (ALs) for exposure to electric fields of frequency 100 kHz–300 GHz, ALs (E) (RMS) = 61 V/m as the maximum value. The legal regulations for reference levels for time-averaged general public exposures of ≥6 min and for electromagnetic fields from 100 kHz to 300 GHz were compared with the normative values presented by ICNIRP. Both guidelines indicate the same value for general public and occupation. On the other hand, legal regulations in Poland are more stringent. According to the regulation of the Ministry of Health, in the work environment, the normative values are defined as intervention exposure levels; ALs where E = 7 V/m refer to the safe zone for pilots and ground handling staff [15], and for places accessible to the public where E = 28 V/m [16]. Interpretation of the results concerned the frequency bands of radio navigation systems. Monitoring and measurement of the EMF generated by the operating devices is cur- tailed not only from the point of view of environmental and human body protection but also in regard to the electromagnetic compatibility [17,18]. Therefore, the following research gives the results of a study that carried out EMF measurements on various aircrafts of the Aviation Training Center in Royal Depultycze near Chelm, Poland. This center provides training for ATPL licenses on airplanes and helicopters as a part of engineering studies. The increasing load of the EMF in light aircrafts can lead to negative effects on pilots’ health and mental condition, especially when it comes to instructors flying multiple-hour flights daily, which can also cause safety risks [19]. It is worth adding that the quantitative assessment of field effects at the workplace is important, especially since contemporary research indicates that possible long-term effects include effects on the reproductive system (asthenozoospermia, oligozoospermia, necrozoospermia), disturbances in memory processes, sleep disorders and their complicated forms, endocrinological disorders, and severe psychosomatic medical conditions [20–22]. Taking into account the measurements and methodology, the paper presents a different approach to the issue of both the electromagnetic field and crew exposure. Typically, tests of devices in the context of electromagnetic compatibility are performed in laboratories on the ground. The presented research depicts an innovative approach to the analysis of the electromagnetic field energy affecting pilots, staff, passengers, and the avionics devices themselves during high-altitude flight, which may affect flight safety. The aim of the study was to quantify training aircraft crews’ exposure to electric field energy, with particular emphasis on components originating from radio navigation devices. Experimental studies were undertaken with the use of real objects (airplanes) and measurements were made during the flight.

2. Air Navigation Devices Currently, aviation uses a variety of RF (Radio Frequency) devices that function as navigation aids and as means of voice communication during the flight. There are transmitting and receiving devices on board that emit electromagnetic fields and, moreover, the plane, together with the crew and passengers, is within the range of electromagnetic fields emitted by ground RF devices. In various phases of flight, especially during take-off Energies 2021, 14, 254 3 of 17

and landing, the airplane is temporarily within the range of the beam electromagnetic ﬁeld being radiated from ground-based navigation guidance devices. This section introduces and brieﬂy describes the most important and most commonly used radio navigation equipment in airplanes [23–25].

2.1. VHF Omnidirectional Radio Range (VOR) The VOR works at the frequency band range from 108 MHz to 118 MHz to ensure the aircraft can receive direction to the ground station location. In order to obtain the demodulation of the signal of a VOR transmitter station, the VOR receiver in an aircraft provides course information relative to the transmitter station. The aircraft position can be derived by triangulating two or more stations. VOR stations provide a relative course to the ground stations. The VOR functions continuously at carrier frequencies with the code identiﬁcation applied to four letters in Morse code, transmitted on a modulation tone of 1.02 kHz.

2.2. Instrument Landing Systems The Instrument Landing System (ILS) constitutes a navigation aid to help landing when visibility is poor, according to Instrument Flying Rules (IFR). The ILS is based upon a radio navigation system (RNS) that guides the aircraft down a slope to the touchdown area on the runway. Multiple radio transmissions that enable an exact approach to landing with an ILS are applied here.

2.2.1. Localizer A localizer constitutes one of the radio transmissions. It is used to oversupply horizontal guidance to the center line of the runway. The localizer transmission is of a Very High Frequency (VHF) broadcast in the lower range of the VOR frequencies band, from 108 MHz to 111.95 MHz on odd frequencies only. Two modulated signals are generated from a horizontally polarized antenna group beyond the far end of the approach runway. They set up an enlarging field that is of 21/2◦ width (about 1500 feet), 5 miles from the runway. The field tapers are situated near the landing threshold. The left side of the access area is filled with a VHF carrier wave modulated with a 90 Hz signal. The right side of the given approach includes a 150 MHz modulated signal.

2.2.2. Glideslope A selected glideslope broadcast holds vertical guidance of the aircraft down the right slope to the touch down point. RF signals help to direct the aircraft precisely to the touchdown point, located at the beginning of the runway. The inclination of the radio signals is approximately 3 degrees, that is, the slope of a typical air trafﬁc airplane approach path. The transmitting glideslope antenna is established off to the side of the approach runway approximately 1000 feet from the threshold. As it approaches the runway and the ﬁeld narrows, it transmits a wedge-like pattern. The polarization of the glideslope antenna is horizontal. The transmitting frequency band range constitutes the UHF from 329.3 MHz to 335.0 MHz.

2.2.3. Compass Locator Additional radionavigation aid are marker beacons, outer, middle and inner. The outer marker beacon is typically 4–7 miles from the runway threshold, which provides additional information to the pilot about the distance from the touchdown point. A middle marker beacon is located on the center navigation light approximately 3500 feet from the runway threshold. However, before the pilot uses the information provided by the marker beacons, the compass locator helps to intercept the approach navigation aid system. The function of an external marker compass locator is performed by an NDB beacon with a transmitting power of 25 W and a range of approx. 15 miles. It transmits omnidirectional Low Frequency (LF) from 190 Hz to 535 Hz radio waves. Energies 2021, 14, 254 4 of 17

2.2.4. Marker Beacons Marker beacons broadcast signals that point at the localization of the aircraft along the glidepath to the runway. As mentioned above, an outer marker beacon transmitter is situated 4–7 miles from the threshold. It spreads a 75 MHz carrier wave modulated with a 400 Hz audio tone in a set of dashes. This transmission corresponds to a very narrow and directed straight up. A middle marker beacon is placed roughly 3500 feet from the runway and transmits at 75 MHz. Its transmission is modulated with a 1300 Hz tone that constitutes a series of dots and dashes due to be distinguished from the all dash tone of the outer marker. An inner marker beacon is eventually used and the modulated signal is transmitted only in a series of dots with a frequency of 3000 Hz. It is located at the Missed Approach Point (MAP), which is the land-or-go-around point of the access close to the runway threshold.

2.2.5. Distance Measuring Equipment (DME) DME is utilized to estimate distance between the aircraft and the runway threshold and works on the query-response timing principle. The airborne transceiver sends 2 pairs of radio pulses. The ground station receives and identiﬁes them and sends a response while handling approximately 100 on-board devices. DME radiometers operate in the frequency range of 960–1215 MHz with a 1 MHz channel spacing; the duplex spacing of the query-response channel is 63 MHz 25. Table1 contains data on the frequency and power emitted by ground-based radio navigation equipment.

Table 1. The frequency and power of emissions of ground-based radio navigation equipment.

Type of Radio Navigation Aid Frequency Range Power Output (Typical) VHF Communication 118–156 MHz 5–50 W VOR 108–118 MHz 100–200 W ILS Glideslope 329–335 MHz 5 W ILS Localizer 108–112 MHz 20 W Marker beacons 75 MHz 2.5 W 1025–1150 MHz DME 25 W 962–1213 MHz

2.3. On-Board Equipment 2.3.1. Receivers and Instruments The localizer, glide path, and eventually the marker beacon and DME receivers are actuated by the one control unit, which is, as expected, located in a separate avionics bay. In cases of light aircrafts, where the available space is narrow, the receiver units are placed underneath the pilot’s seats. There are a large number of different varieties of ILS indexes in operational use. One of them is the cross pointer indicator, used both in the traditional version as a device built into the plane’s dashboard and in the glass cockpit version (visual indicator on the display screen).

2.3.2. Aerials Localizer aerials are typically based in the vertical stabilizer. Similar aerials can feed two localizer receivers; the aerial system and receivers are generally applied for VOR as well. When a third localizer receiver is installed, its aerial is generally placed in the nose section, mostly within the radome given for weather radar. The glidepath receiver antenna is usually placed on the nose of the aircraft to obtain the best possible receiving conditions. Marker beacon aerials are usually mounted on the bottom surface of the aircraft fuselage. They are usually ﬂush mounted type. Figure1 shows a schematic of the radio navigation equipment system near the airport landing runway. Energies 2021, 14, x FOR PEER REVIEW 5 of 18

Localizer aerials are typically based in the vertical stabilizer. Similar aerials can feed two localizer receivers; the aerial system and receivers are generally applied for VOR as well. When a third localizer receiver is installed, its aerial is generally placed in the nose section, mostly within the radome given for weather radar. The glidepath receiver antenna is usually placed on the nose of the aircraft to obtain the best possible receiving conditions. Marker beacon aerials are usually mounted on the bottom surface of the air- Energies 2021, 14, 254 craft fuselage. They are usually flush mounted type. 5 of 17 Figure 1 shows a schematic of the radio navigation equipment system near the airport landing runway.

Figure 1. Diagram of radio-navigation on an approach to landing with the use of ILS. GS—Glide Figure 1. Diagram of radio-navigation on an approach to landing with the use of ILS. GS—Glide Slope, IM—Inner marker, LOC—Localizer, MM—Middle Marker, OM—Outer Marker. Slope, IM—Inner marker, LOC—Localizer, MM—Middle Marker, OM—Outer Marker. 3. Materials and Methods 3.3.1. Materials The Test and Airplanes Methods 3.1. TheMeasurements Test Airplanes of the electric component (E) of EMF were carried out in four different aircraft:Measurements an Aero AT-3 of the R100, electric a Cessna component C172, a(E Tecnam) of EMF P2006T, were carried and a Robinsonout in four R44 different Raven aircraft:helicopter. an Aero The AT-3 measurements R100, a Cessna were C172 carried, a Tecnam out in P2006T, accordance and witha Robinson the PN-T-06580-3: R44 Raven helicopter.2002 standard The measurements [26], which defines were thecarried methods out in of accordance measuring with and the assessing PN-T-06580-3: EMF at work-2002 standardplaces with [26], frequencies which defines from the 0 methods Hz to 300 of GHz.measuring The airplanes and assessing presented EMF at are workplaces used every withday frequencies for flight training from 0 in Hz the to Center 300 GHz. of Aviation The airplanes of the Statepresented School are of Higherused every Education day for in flightChełm, training Poland. in the Center of Aviation of the State School of Higher Education in Chełm, Poland.The AT3 R100 is the smallest aircraft used for the tests. Its origin is connected with an amateurThe AT3 design, R100 Pottier is the P220,smallest which aircraft was aused popular for the homebuilt tests. Itsaircraft. origin is Although connected the with AT3 anresembles amateur thedesign, P220, Pottier it is a P220, completely which new was design,a popular with homebuilt major structural aircraft. andAlthough conceptual the AT3changes resembles that were the P220, necessary it is a tocompletely comply with new certification design, with regulations. major structural As mentioned, and concep- it is tuala small changes airplane that were (wingspan necessary 7.60 to m) comply with two with side-by-side certification seats. regulations. The airplane As mentioned, is certified itfor is a VFR small (Visibility airplane (wingspan Flight Rules) 7.60 flights, m) with however two side-by-side it is equipped seats. withThe airplane most of is the certi- IFR fiedinstruments for VFR (Visibility for primary Flight training Rules) in IRflights, flights. however Therefore, it is some equipped of the with avionics most are of placedthe IFR in instrumentsunusual locations, for primary for example training under in IR flights. the seats. Therefore, some of the avionics are placed in unusualThe Cessna locations, 172 for and example the Robinson under R44 the Raven seats. are widely used general aviation aircrafts. TheyThe are Cessna very popular 172 and as the training Robinson aircrafts R44 andRaven are are equipped widely with used full general IFR avionics. aviation aircrafts. TheThey Tecnam are very P2006T popular aircraft as training is a twin aircrafts engine and type are with equipped retractable with full landing IFR avionics. gear. It is poweredThe Tecnam by a pair P2006T of Rotax aircraft piston is a engines twin engine and istype certified with retractable for IR flights, landing being gear. equipped It is poweredwith the by IFR a instruments.pair of Rotax piston engines and is certified for IR flights, being equipped with theAll IFR the instruments. four aircrafts used in the test flights are of metal construction. 3.2. The Device for the Test of Electromagnetic Fields The E tests were carried out with the NHT3DL meter by Microrad, with the 01E measuring probe (Figure2). The device is used for measurements and tests of electromagnetic fields in a wide range of frequencies present in the general environment as well as in the working environment in accordance with the international standards as described in [27]. The measurement of the electrical and magnetic components of the electromagnetic field takes place in the three directions X. Y. and Z for the peak impulse value (PEAK) and the effective value (RMS), which determines the maximum value in time. In terms of high frequency, the effective value (RMS) is most often adopted in standards and legal acts [28]. Energies 2021, 14, x FOR PEER REVIEW 7 of 18

3.2. The Device for the Test of Electromagnetic Fields The E tests were carried out with the NHT3DL meter by Microrad, with the 01E measuring probe (Figure 2). The device is used for measurements and tests of electromagnetic fields in a wide range of frequencies present in the general environment as well as in the working environment in accordance with the international standards as described in [27]. The measurement of the electrical and magnetic components of the electromagnetic field Energies 2021, 14, 254 takes place in the three directions X. Y. and Z for the peak impulse value (PEAK) and6 of the 17 effective value (RMS), which determines the maximum value in time. In terms of high frequency, the effective value (RMS) is most often adopted in standards and legal acts [28].

Figure 2. The Microrad NHT3DL electric field meter with 01E measuring probe, installed in the Figure 2. The Microrad NHT3DL electric ﬁeld meter with 01E measuring probe, installed in the Cessna C172 aircraft. Cessna C172 aircraft.

TheThe obtained obtained values values are are saved saved to to the the device device memory memory using using an an SD SD card. card. The The meter, meter, withwith a a built-inbuilt-in temperature and and humidity humidity sensor sensor,, is islocated located in the in thehousing. housing. Figure Figure 2 shows2 showsthe measuring the measuring device devicewith the with probe. the The probe. devi Thece enables device the enables measurement the measurement of fields emit- of fieldsted by emitted such groups by such of groups objects of as objects industrial as industrial devices, devices,medical medicaldevices, devices,transformer transformer stations, stations,high-voltage high-voltage lines, railways, lines, railways, the defense the defenseindustry, industry, radio transmitters, radio transmitters, wireless wireless telecom- telecommunicationmunication systems systems (base stations, (base stations, mobile mobile phone, phone, broadcasting broadcasting equipment, equipment, satellite, satellite, com- communicationmunication equipment). equipment). A measurin A measuringg probe probe marked marked as 01E as 01E was was used. used. TheThe 01E 01E probe probe is is commonlycommonly usedused toto detectdetect both CW (Continuous Wave) Wave) and modu- mod- ulatedlated signals signals in in the the frequency frequency ranges ranges from from 100 100 kHz kHz to 6.5 to GHz, 6.5 GHz, which which in turn in turnallow allow appli- applicationscations in the in theindustrial, industrial, scientific, scientific, medical, medical, telecommunications, telecommunications, and and power power plants plants sec- sectors.tors. The The high high sensitivity sensitivity of the of 01E the probe 01E probe makes makes it capable it capable of measuring of measuring human exposure human exposureto electric to fields electric in fieldsboth public in both and public environmental and environmental conditions conditions [29]. [29]. TheThe technical technical parameters parameters of of the the probe probe are are presented presented in in Table Table2. 2.

TableTable 2. 2.The The technical technical parameters parameters of of the the probe probe [30 [30].].

TechnicalTechnical Speciﬁcations Specifications FrequencyFrequency range range 100 100 kHz–6.5 kHz–6.5 GHz GHz MeasurementMeasurement range range 0.2–360 0.2–360 V/m V/m DynamicDynamic range range 65 dB65 dB SensorSensor type type Diode Diode dipoles dipoles Directivity Isotropic Directivity Isotropic ±1.5 dB (1 MHz–3 GHz) Frequency response Frequency response ±2.5 ±1.5 dB dB (3 GHz–6.5(1 MHz–3 GHz) GHz) Linearity ±0.5 dB (2–200 V/m) Operating temperature 0–50 ◦C Size 327 × 60 Ø (mm)

Weight 120 g

The measurements of EM energy took place from the moment the crew started taxiing until they stopped after landing. Energies 2021, 14, x FOR PEER REVIEW 8 of 18

±2.5 dB (3 GHz–6.5 GHz) Linearity ±0.5 dB (2–200 V/m) Operating temperature 0–50 °C Size 327 × 60 Ø (mm) Weight 120 g

Energies 2021, 14, 254 The measurements of EM energy took place from the moment the crew started 7taxi- of 17 ing until they stopped after landing.

3.3. The Flight Test Campaign 3.3. TheAs already Flight Test mentioned, Campaign the measurements were carried out under real conditions duringAs flights already of mentioned,the training theaircrafts measurements mentioned were above. carried As the out aim under of the real work conditions was to investigateduring flights the ofinfluence the training of individual aircrafts radio mentioned and navigation above. As devices the aim on of the the strength work was of the to electromagneticinvestigate the influence field in the of individualplane, the measurements radio and navigation were started devices at on the the beginning strength of of the landingelectromagnetic approach, field during in the IFR plane, flights. the measurements were started at the beginning of the landingIn order approach, to analyze during the IFR electric flights. field strength, measurements were made on various flightsIn that order lasted to analyze from 1 h the to electric4.6 h. A fieldtotal strength,of 12 flights measurements were made, 3 were flights made on each on various plane. Asflights part thatof the lasted flight from test 1campaign, h to 4.6 h. measurem A total of 12ents flights were werecarried made, out during 3 flights the on procedural each plane. approachAs part of to the landing flight testusing campaign, the ILS system. measurements Moreover, were the carried measurements out during were the carried procedural out duringapproach en-route to landing flights using with the the ILS use system. of VO Moreover,R and GPS the radio measurements navigation wereaids, carriedas well out as duringduring navigation en-route flights exercises with in the the use controlled of VOR zone and GPSof the radio Depu navigationłtycze Królewskie aids, as airport. well as Theduring flights navigation were carried exercises out both in the during controlled the day zone and of theat night, Depułtycze in various Kró lewskieweather airport.conditions,The flights but the were use carried of radio out navigation both during device the days was and the at same, night, regardless in various weatherof the conditions. conditions, but the use of radio navigation devices was the same, regardless of the conditions. 4. Results and Discussion 4. Results and Discussion This section presents the results of selected E measurements by means of the This section presents the results of selected E measurements by means of the NHT3DL NHT3DL meter with the E01 measuring probe. The obtained RMS values to which the meter with the E01 measuring probe. The obtained RMS values to which the regulations regulations refer were analyzed. Figures 3–5 show the measurement results of the electric refer were analyzed. Figures3–5 show the measurement results of the electric component component of EMF in the Aero AT 3. of EMF in the Aero AT 3.

Figure 3. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the Aero Figure 3. The intensity of the electrical component of the electromagnetic ﬁeld in the course of ﬂight no. 1 for the Aero AT3. AT3.

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Figure 4. The intensity of the electrical component of the electromagnetic field in the course of flight no. 2 for the Aero FigureAT3. 4. The intensityintensity ofof thethe electrical electrical component component of of the the electromagnetic electromagnetic ﬁeld field in thein the course course of ﬂight of flight no. 2no. for 2 the for Aero the Aero AT3. AT3.

Figure 5. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Aero Figure 5. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Aero AT3. FigureAT3. 5. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Aero AT3. The maximum values of the electric field strength where E = 4.59 V/m were observed duringThe the maximum approach values to landing of the for el theectric flight field marked strength as AT3where no. E 1. = At4.59 this V/m point, were the observed aircraft The maximum values of the electric field strength where E = 4.59 V/m were observed wasduring on thethe VORapproach approach to landing path. Comparing for the flight the marked results foras AT3 the flight no. 1. marked At this aspoint, AT3, the flights air- during the approach to landing for the flight marked as AT3 no. 1. At this point, the air- no.craft 4 was and no.on the 5 were VOR training approach flights path. without Comparing approach the results to landing for the at Lublinflight marked airport, as where AT3, craft was on the VOR approach path. Comparing the results for the flight marked as AT3, ILSflights and no. VOR 4 and navigation no. 5 were devices training are flights installed. without The highest approach values to landing of electric at Lublin field strength airport, flights no. 4 and no. 5 were training flights without approach to landing at Lublin airport, werewhere present ILS and during VOR navigation radio correspondence devices are withinstal Depultyczeled. The highest Krolewskie values of airfield electric tower, field where ILS and VOR navigation devices are installed. The highest values of electric field wherestrengthE =were 0.73–1.09 present V/m. during The radio next correspondence aircraft analysis with was Depultycze the Cessna C172Krolewskie (Figures airfield6–8). strength were present during radio correspondence with Depultycze Krolewskie airfield Selectedtower, where flights E took= 0.73–1.09 place with V/m. an The approach next aircraft to landing analysis at Lublin was the airport Cessna (VOR, C172 ILS). (Figures tower,6–8). Selected where E flights = 0.73–1.09 took place V/m. with The annext approach aircraft anto alysislanding was at Lublinthe Cessna airport C172 (VOR, (Figures ILS). 6–8). Selected flights took place with an approach to landing at Lublin airport (VOR, ILS).

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Figure 6. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the Cessna 172.

For flight no. 1 with the Cessna 172, the maximum values to which the pilot and the passenger were exposed were E = 9.75 V/m. On the basis of the analysis, it was noticed that the maximum values of E = 8–9.75 V/m occurred during landing phase with the VOR Figure 6. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the Cessna Figure 6. The intensity of thesystem. electrical component of the electromagnetic ﬁeld in the course of ﬂight no. 1 for the Cessna 172. 172.

Figure 7. The electric field in the course of flight no. 2 for the Cessna 172. Figure 7. The electric ﬁeld in the course of ﬂight no. 2 for the Cessna 172. The high value of E = 5. 45 V/m was recorded during an ILS approach. The aircraft at this point entered the ILS approach path. In this case, values between 2.5–3 V/m are present during communication with the airport.

Figure 7. The electric field in the course of flight no. 2 for the Cessna 172.

The high value of E = 5. 45 V/m was recorded during an ILS approach. The aircraft at this point entered the ILS approach path. In this case, values between 2.5–3 V/m are present during communication with the airport.

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Figure 8. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Cessna Figure 8. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Cessna 172. 172. For flight no. 1 with the Cessna 172, the maximum values to which the pilot and the The maximum values of the electrical component of the electromagnetic field during passenger were exposed were E = 9.75 V/m. On the basis of the analysis, it was noticed the measurement at the landing phase (VOR) were reached with Cessna 172 flight no. 3, E thatwhere the E maximum = 10.66 V/m. values It is important of = 8–9.75 to notice V/m that occurred they are several during times landing higher phase than withdur- the VORing non-approach system. flights at airports equipped with instrument landing systems. The value The high value of E = 5. 45 V/m was recorded during an ILS approach. The aircraft Figure 8. The intensity of theof electricalE during componen the landingt of therange electromagnetic went from 5 field V/m in to the the co ursemaximum of flight during no. 3 for this the flight, Cessna 10.66 172. atV/m. this point entered the ILS approach path. In this case, values between 2.5–3 V/m are presentThen during measurements communication were made with theduring airport. the flight of the Tecnam P2006T. The values describedTheThe maximum maximum in Figures values values9–11 record ofof the the el electricalectrical results componentob componenttained by of means of the the el ofectromagnetic electromagnetic the meter in fieldthe fieldTecnam during during theP2006T.the measurement measurement at at the the landinglanding phase (VOR) (VOR) were were reached reached with with Cessna Cessna 172 172 flight flight no. 3, no. 3, wherewhereE E= = 10.66 10.66 V/m. It Itis isimportant important to notice to notice that they that are they several are several times higher times than higher dur- than duringing non-approach non-approach flights flights at ai atrports airports equipped equipped with instrument with instrument landing landingsystems. systems.The value The valueof E ofduringE during the landing the landing range rangewent from went 5from V/m to 5 V/mthe maximum to the maximum during this during flight, this 10.66 flight, 10.66V/m. V/m. ThenThen measurements measurements were made made during during the the flight flight of the of Tecnam the Tecnam P2006T. P2006T. The values The val- uesdescribed described in Figures in Figures 9–119 record–11 record the results the results obtained obtained by means by of means the meter of thein the meter Tecnam in the TecnamP2006T. P2006T.

Figure 9. The intensity of the electrical component of the electromagnetic field in the course of a flight for the Tecnam P2006T flight no 1.

For the Tecnam P2006T flight no. 1, the highest values of E = 2.0 V/m were read at the VOR approach path.

Figure 9. The intensity of the electrical component of the electromagnetic field in the course of a flight for the Tecnam Figure 9. The intensity of the electrical component of the electromagnetic field in the course of a flight for the Tecnam P2006T flight no 1. P2006T flight no 1. For the Tecnam P2006T flight no. 1, the highest values of E = 2.0 V/m were read at the VOR approach path.

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Figure 10. The intensity of the electrical component of the electromagnetic field in the course of flight no. 2 for the Tecnam P2006T.

For the second training flight in the Tecnam P2006T aircraft, the highest values rec- Figure 10. The intensity of the electrical component of the electromagnetic field in the course of flight no. 2 for the Tecnam Figure 10. The intensity oforded the electrical showed component that E = 1.25 of the V/m electromagnetic during correspondence ﬁeld in the course with the of ﬂight airport. no. The 2 for analyzed the P2006T. Tecnam P2006T. flights (Figures 11 and 12) took place in a circuit pattern without ILS and VOR systems. For the second training flight in the Tecnam P2006T aircraft, the highest values recorded showed that E = 1.25 V/m during correspondence with the airport. The analyzed flights (Figures 11 and 12) took place in a circuit pattern without ILS and VOR systems.

Figure 11. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Tecnam Figure 11. The intensity of the electrical component of the electromagnetic ﬁeld in the course of ﬂight no. 3 for the P2006T. Tecnam P2006T.

ForThe themaximum Tecnam result P2006T of flightthe intensity no. 1, the of highestthe electric values component of E = 2.0 of V/m the wereelectromagnetic read at the Figure 11. The intensity of thefield electrical for the componen Tecnamt P2006Tof the electromagnetic flight no. 1 obta fieldined in the in course the course of flight of no.the 3 measurement for the Tecnam with P2006T. VOR approach path. the meterFor the was second E = 3.3 trainingV/m. This flight value in was the recorded Tecnam while P2006T connecting aircraft, theto the highest GPS. values The tests for the Robinson R44 are described in Figures 12–14. recordedThe maximum showed that resultE = 1.25of the V/m intensity during of correspondence the electric component with the of airport. the electromagnetic The analyzed fieldflights for (Figures the Tecnam 11 and P2006T 12) took flight place no. in 1 a obta circuitined pattern in the withoutcourse of ILS the and measurement VOR systems. with the meter was E = 3.3 V/m. This value was recorded while connecting to the GPS. The tests for the Robinson R44 are described in Figures 12–14.

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Figure 12. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the Robinson Figure 12. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the R44. Robinson R44. Figure 12. The intensity of the electrical component of the electromagnetic field in the course of flight no. 1 for the Robinson For the Robinson R44 helicopter flight no. 1, the highest values of the electric compo- R44. The maximum result of the intensity of the electric component of the electromagnetic nent,field forwhere the TecnamE = 3.22 V/m, P2006T were flight read no. for 1 the obtained correspondence in the course with of the the airport measurement via radio. with the meterFor the was RobinsonE = 3.3 V/m.R44 helicopter This value flight was no. recorded 1, the highest while connecting values of the to theelectric GPS. component,The where tests E for= 3.22 the V/m, Robinson were R44read are for described the correspondence in Figures 12with–14 the. airport via radio.

Figure 13. The intensity of the electrical component of the electromagnetic field in the course of flight no. 2 for the Robinson R44. Figure 13. The intensity of the electrical component of the electromagnetic field in the course of flight no. 2 for the Robinson Figure 13. The intensity of the electrical component of the electromagnetic ﬁeld in the course of ﬂight no. 2 for the R44. For flight no. 2, the maximum values of the electrical component were E = 5.23 V/m. Robinson R44. At this test point, the helicopter was at the VOR approach path. The remaining values of the electricFor flight component no. 2, the at maximum the VOR poin valuest vary of the in theelectrical range ofcomponent 3.1–5.0 V/m. were E = 5.23 V/m. At this test point, the helicopter was at the VOR approach path. The remaining values of the electric component at the VOR point vary in the range of 3.1–5.0 V/m.

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Figure 14. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the Robinson Figure 14. The intensity of the electrical component of the electromagnetic field in the course of flight no. 3 for the R44. Robinson R44. For flight no. 3 with the R44 aircraft, the highest values were also recorded, where E For the Robinson R44 helicopter flight no. 1, the highest values of the electric compo- = 7.81 V/m. The helicopter was also in the range of the VOR system. The observed values nent, where E = 3.22 V/m, were read for the correspondence with the airport via radio. in theFor range flight of no.3.0–4.0 2, the V/m maximum were obtained values during of the electrical correspondence component with were the airport.E = 5.23 V/m. At thisIn testorder point, to observe the helicopter the regularities was at the in VORthe studied approach electromagnetic path. The remaining field phenomena values of resultingthe electric from component the large at number the VOR of pointsamples vary obtained in the range by measurements, of 3.1–5.0 V/m. a statistical analysis wasFor performed. flight no. 3 The with statistical the R44 aircraft,analysis theimplemented highest values values were of the also electric recorded, field whereinten- sityE = measurement 7.81 V/m. The by helicopter the NHT3DL was meter also in into the th rangee Statistica of the VOR13.3 software. system. The observedvalues of thevalues analyzed in the rangevariables of 3.0–4.0 are determined V/m were by obtained the mean during value, correspondence median, standard with the deviation airport. (SD), Inand order range to of observe variation. the regularitiesThe researchers in the assumed studied an electromagnetic error of inference field which phenomena equals 5%,resulting and the from level the largeof significance number of was samples p < 0.05. obtained The bycharacteristics measurements, of electric a statistical field analysis for se- lectedwas performed. flights are Thedepicted statistical in Table analysis 3. implemented values of the electric field intensity measurement by the NHT3DL meter into the Statistica 13.3 software. The values of the Tableanalyzed 3. Characteristics variables are of determinedthe intensity of by the the electr meanical value, component median, of the standard electromagnetic deviation energy (SD), Eand, in V/m, range for of testing variation. airplanes. The researchers assumed an error of inference which equals 5%, andVariable the level of significanceMean was p < 0.05.Minimum The characteristics Maximum of electric field for SD selected flightsTecnam1 are depicted in Table0.34373. 0.129 2.075 0.2969 Tecnam2 0.3283 0.107 1.258 0.1603 Table 3. Characteristics of the intensity of the electrical component of the electromagnetic energy E, Tecnam3 0.2895 0.077 3.384 0.2312 in V/m, for testing airplanes. AT3_1 0.1612 0.025 4.594 0.2654 VariableAT3_2 0.1469 Mean Minimum 0.097 Maximum 1.090 0.0958 SD Tecnam1AT3_3 0.1835 0.3437 0.019 0.129 0.730 2.075 0.0629 0.2969 Cessna1Tecnam2 0.6247 0.3283 0.102 0.107 9.776 1.258 1.1847 0.1603 Cessna2Tecnam3 0.2978 0.2895 0.013 0.077 5.445 3.384 0.6785 0.2312 Cessna3AT3_1 0.5766 0.1612 0.073 0.025 10.66 4.594 0.8480 0.2654 AT3_2 0.1469 0.097 1.090 0.0958 R44_1AT3_3 0.2984 0.1835 0.121 0.019 3.221 0.730 0.4020 0.0629 Cessna1R44_2 0.4861 0.6247 0.067 0.102 5.230 9.776 0.7839 1.1847 Cessna2R44_3 0.4970 0.2978 0.079 0.013 7.813 5.445 1.0084 0.6785 Cessna3 0.5766 0.073 10.66 0.8480 TheR44_1 average electric 0.2984 fields value for the 0.121 analyzed airplanes 3.221 ranges from 0.40200.147–0.624 R44_2 0.4861 0.067 5.230 0.7839 V/m. TheR44_3 parameters of 0.4970the tested quality 0.079 is very high, in the 7.813 range of 0.013 1.0084 V/m–10.87 V/m. In order to verify this hypothesis, the differences between the indicated airplanes tests obtained with the NHT3DL meter are presented in Figure 15.

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The average electric ﬁelds value for the analyzed airplanes ranges from 0.147–0.624 V/m. The parameters of the tested quality is very high, in the range of 0.013 V/m–10.87 V/m. EnergiesEnergies 2021 2021, 14, 14, x, xFOR FOR PEER PEER REVIEW REVIEW 1515 of of 18 18 In order to verify this hypothesis, the differences between the indicated airplanes tests obtained with the NHT3DL meter are presented in Figure 15.

1212

1010

8 8

6 6 E, V/m E, V/m 4 4

2 2

0 0

-2-2 Median Median 25%-75% 25%-75% R44_1 R44_2 R44_3 R44_1 R44_2 R44_3 AT3_1 AT3_2 AT3_3 AT3_1 AT3_2 AT3_3 Cessna1 Cessna2 Cessna3 Cessna1 Cessna2 Cessna3 Min-Max Min-Max Tecnam1 Tecnam2 Tecnam3 Tecnam1 Tecnam2 Tecnam3 FigureFigure 15. 15.15. Range Range of of quality quality and andand median medianmedian of ofof electromag electromagneticelectromagneticnetic (EM) (EM)(EM) energy energyenergy during duringduring airplane airplaneairplane flight. ﬂight.flight.

ItItIt can cancan be be observedobserved observed that that that values values values exceeding exceeding exceeding the th electricthe eelectric electric ﬁeld field limitfield limit occurlimit occur inoccur selected in in selected selected Cessna Cessna172Cessna and 172 172 Robinson and and Robinson Robinson R44 ﬂights. R44 R44 flights. Figureflights. 16Figure Figure presents 16 16 presents presents a frame-moustache a aframe-moustache frame-moustache graph with graph graph marked with with markedaveragesmarked averages averages and standard and and standard standard deviation. deviation. deviation.

Figure 16. Box plots of measurements of the electric component of electromagnetic fields. FigureFigure 16. 16. Box Box plots plots of of measurements measurements of of the the electr electricic component component of of electromagnetic electromagnetic fields. fields. From Figure 16, it can be observed that there are differences in the mean of the electric componentFromFrom Figure Figure of electromagnetic 16, 16, it it can can be be observed observed fields that between that there there differentare are differences differences types in ofin the airplanes.the mean mean of of the In the orderelectric electric to componentestablishcomponent whether of of electromagnetic electromagnetic there are statistically fields fields between between significant di differentfferent differences types types of of betweenairplanes. airplanes. the In In electric order order to fieldsto es- es- tablishfortablish particular whether whether types there there of are are testing statistically statistically airplanes, significa significa the Student’sntnt differences differencest-test between (Table between4) wasthe the electric carriedelectric fields out.fields for for particularparticular types types of of testing testing airplanes, airplanes, the the Student’s Student’s t -testt-test (Table (Table 4) 4) was was carried carried out. out.

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Table 4. Test results for individual comparisons (aircrafts). p—statistical signiﬁcance.

Test Results for Individual Comparisons Statistica Signiﬁcance Tecnam 1 vs. Tecnam 2 p = 0.555 Irrelevant Tecnam 2 vs. Tecnam 3 p = 0.000 Relevant Tecnam 1 vs. Tecnam 3 p = 0.000 Relevant AT 3_ 1 vs. AT 3_ 2 p = 0.160 Irrelevant AT3_ 2 vs. AT 3_ 3 p = 0.000 Relevant AT3_1 vs. AT 3_3 p = 0.000 Relevant Cessna 1 vs. Cessna 2 p = 0.000 Relevant Cessna 2 vs. Cessna 3 p = 0.000 Relevant Cessna 1 vs. Cessna 3 p = 0.148 Irrelevant R44_1 vs. R44_2 p = 0.000 Relevant R44_2 vs. R44_3 p = 0.884 Irrelevant R44_1 vs. R44_3 p = 0.000 Relevant

Comparing the levels of intensity of the electric component in different types of airplanes, statistically insigniﬁcant differences were found for Tecnam 1 vs. Tecnam 2, AT3_1 vs. AT3_2, Cessna 1 vs. Cessna 3, and Robinson R44_2 vs. R44_3.

5. Conclusions Measurements of the electromagnetic field in training airplanes were carried out using the Microcard NHT3DL electromagnetic field meter with the 01E probe, during flights, on the landing approach supported by radio navigation systems. During the measurements, the meter was placed between the front seats of the pilots. The obtained measurement results were subjected to statistical analysis. It was concluded as follows: • The values of the electromagnetic field electric component, recorded during the test flights of all the analyzed aircraft types (Aero AT-3 R100, Cessna C172, Tecnam P2006T, and Robinson R44 Raven) with relation to the Directive 2013/35/EU (in terms of health protection, safety, and exposure of workers to hazards caused by physical factors) remain within the limits of the indicated standard. • According to the current regulations by the Minister of Labor, Family, and Social Policy of 27 June 2016, in line with detailed guidelines in force in Poland regarding the exposure of the aircraft crew, the recorded RMS values were: E = 10.66 V/m, E = 9.77 V/m, E = 7, 81 V/m for Cessna flight no. 1, Cessna flight no. 3, and Robinson R44 flight no. 3 are considered to be over-normative. The recorded results concerned the landing phase when VOR system was used. • The use of the VOR system during the approach phase of the Aero AT-3 R100 aircraft also resulted in a high recorded maximum value of E = 4.59 V/m. • The short-range, radio-assisted navigation system (ILS) generated increased values of the electric field. The range of 2.5–5.45 V/m for the Cessna C172 aircraft should be specified here, however, the values allowed in the regulation were not exceeded here. • Larger field interactions and higher field strengths in the VOR beacon system compared to the ILS system can be correlated with the purpose of the system, in particular with the power of transmitting devices. It went up to 200 W in the case of VOR and up to 50 W in the short-range ILS guidance system. • Approaches at airports not equipped with VOR and ILS directional radiolocation systems in all cases resulted in maximum electric field strengths of 0.4–2.5 V/m being registered. It should be noted that the values of the intensity of the electromagnetic field electric component, where E = 2.5 V/m, were recorded only when the crew communicated with the control tower via radio stations. • Particularly high values of the electric field’s electric component intensity were recorded in the Cessna C172, the sheet of which is aluminum, riveted to the spar and ribs, and communication devices were located in the immediate vicinity of the pilot’s seat. Energies 2021, 14, 254 16 of 17

• During the tests, very high values of up to E = 18.5 V/m (electrical component) were noted. These values were omitted in the interpretation of the results, as the indicated standards refer only to RMS values. As for the regulation established by the Minister of Health in December 17, 2019, concerning potential passengers traveling by air, the normative values were not exceeded. Therefore, a representative group of instructor pilots should be tested to identify trends. This will be the subject of our team’s future research work. Another interesting topic is the study of exposure to electromagnetic energy in electric powered trainer airplanes. This is especially important in the era of the global development of the aviation industry and the regional development of aviation infrastructure.

Author Contributions: Conceptualization. J.M., J.P.; Methodology. J.M. and J.P., P.K.; Software. J.M.; Formal Analysis. J.M., J.P.; Investigation. J.M.; Resources. J.M. and J.P.; Data Curation. A.T., Ł.P.; Writing—Original Draft Preparation. J.M., J.P.; Writing—Review & Editing. J.M., J.P., P.K.; Visualization. J.M.; Supervision. A.T., Ł.P.; All authors provided critical feedback and collaborated in the paper. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Informed consent was obtained from all subjects involved in the Study. Data Availability Statement: Not applicable. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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