1. Introduction
The effect of electromagnetic fields on human health and various areas of human activity is studied in numerous scientific and research centers worldwide. Despite researchers’ widespread interest, the methodology for the assessment of the effect of electromagnetic fields has not been standardized. Considerable activities aimed at decreasing the negative influence of electromagnetic fields are being undertaken [
1,
2,
3]. It is worth mentioning that there are plentiful positive applications of electromagnetic fields, particularly in medicine, such as its therapeutic effect in the treatment of such disorders as neoplasms, burns, circulatory system diseases, or arthritis, as well as modern diagnostic imaging methods that utilize electromagnetic fields, including computed tomography, optical tomography, and microwave tomography. Moreover, research on the effect of electromagnetic fields on human health, which is concerned with the operation of electric and electronic devices, are being conducted [
3,
4,
5]. Except for the direct protection of health, there are numerous technical aspects regarding the hazards resulting from electromagnetic fields exceeding their normal values. High-frequency electromagnetic fields can disrupt or even cause permanent damage to electronic equipment used in aviation, among other areas. Therefore, some special attention is paid to the issue of electromagnetic fields that can disturb the operation of communication, radar, and location devices or systems. The research investigates avionic measuring equipment that is subjected to high risk during its operation [
6,
7,
8,
9,
10].
Research on electronic devices used in aviation is performed in specially screened chambers where avionic equipment is subjected to high-frequency electromagnetic fields from 10 kHz to 40 GHz. The research is conducted in order to determine the sensitivity of the devices to the effects of external fields and whether the instruments affect the environment. The requirements, which must be met by all onboard electronic devices and systems used in aviation, are depicted in the EU Directive 2013/35/ [
11,
12,
13,
14,
15,
16]. Onboard devices, radio-navigation devices, aviation communication, and navigation systems constitute basic avionic equipment.
High-frequency electromagnetic fields are most frequently produced by radio communication devices. Radio stations, telecommunication devices, mobile telephony base stations, WiFi devices, radars, and communication systems are indispensable nowadays. Tests on the effect of electromagnetic fields on electronic devices are commonly conducted when designing the device [
17,
18,
19].
The increasing load of the electromagnetic field in light aircrafts can lead to negative effects on the pilots’ health and mental condition, especially when it comes to instructors flying many-hour flights daily, which can lead to safety risks. Studies on the impact of electromagnetic fields on humans result from the EU Directive 2013/35/ directive. The continuous increase in radio infrastructure, including mobile telephony, is associated with an increasing electromagnetic field strength. In particular, in the area of Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) relays, the electromagnetic field values can reach high values. The second source of electromagnetic fields that affects the pilot during the flight is avionics. Integrated avionics, which use one large display instead of many single indicators, is a great convenience for the pilot due to the presentation of a great deal of flight information on one display. Glasscocpit is currently the standard in aircraft communication. Thus, flight training organizations (FTO) are increasingly willing to use training aircrafts with the Glasscocpit system [
20,
21,
22,
23,
24].
The purpose of the present study was to conduct electromagnetic field measurements on selected aircrafts from the Aviation Training Center in Royal Depultycze, near Chelm, Poland. The center is an integral part of the higher vocational school in Chelm and conducts training for airline pilots on airplanes and helicopters as a part of engineering studies.
The results were depicted in the form of graphs as a function of time. Due to the stochastic character of the sample, the analysis of the data obtained, with the emerging characteristic trends and parameters, was performed using the Statistica 13. 3 software (JPZ803D036327AR-2, StatSoft Poland, Cracow, Poland).
3. Results and Discussion
The measurements were performed during the flights. In order to measure the intensity of the electric field, the first measurement was conducted on the ground in the Air Traffic Control Tower of Depułtycze Królewskie airfield (
Figure 3).
Maximum values of the electric component of the electromagnetic field obtained during measurements in the ground service station were measured using the GSM 900 frequency band. What is of great significance is that the values were several-fold higher than the ones recorded in other frequency bands. The intensity of the electromagnetic field in this location was relatively low.
The next step involved the measurement during the flights. The flights presented in the study were performed in the vicinity of such towns as: Krasnystaw, Bilgoraj, and Tomaszow Lubelski where antennas of mobile telephony are located. The selected flight route is shown in
Figure 4.
The results for the GSM 900 system are shown in
Figure 5. The values depicted in
Figure 5,
Figure 6 and
Figure 7 refer to the measurement results obtained using the dosimeter in the Cessna 152.
The highest measured value using the GSM 900 frequency band obtained was E = 0.29 V/m for the oldest mobile telephony system. GSM 900 frequency was the first system utilized in mobile telephony communication. The next GSM 1800 frequency band obtained in the measurement with the ESM 140 dosimeter is shown in
Figure 6.
The maximum result of the intensity of the electric component of the electromagnetic field using the GSM 1800 obtained during the measurement with the dosimeter was E = 1.58 V/m.
Communication systems, such as UMTS, used for frequencies of 1920–2170 MHz, and GSM differ in terms of the implementation of various modern multimedia services. Moreover, UMTS uses services that are available both on the ground and through the satellite system. The system enables the simultaneous transmission of audio, video, and data in real time.
The maximum value obtained during the Cessna C152 flight for the UMTS communication system was E = 1.21 V/m (
Figure 7). It can be observed that the maximum values of the electric field for all frequency bands analyzed refer to the point of time from the 68th to the 70th minute of the flight, which corresponds to the location of the aircraft over Bilgoraj.
The measurement error was recorded for the frequencies researched during a flight, which are presented in
Figure 8.
The limits of measurement uncertainty for the data obtained are given in
Figure 8. Systematic error was chosen as the basis for uncertainty, whose sources were mainly: instrument class, characteristics of the band filters in the tested frequencies, flight altitude and heading relative to electromagnetic field sources, and meteorological factors. Moreover, the measurement error was also affected by the installation of the measuring unit, which, mainly for practical reasons, was placed on the pilot’s arm (see
Figure 1, right), which meant that the measurement was not carried out in the free field. In future test, we are planning to use an on-board electromagnetic field-monitoring sensor in order to minimize the installation effects. This sensor is described in
Section 4 of the present paper.
Although the majority of high-frequency electromagnetic field measurements are performed in scientific centers on land, this study was concerned with the comparison of the results obtained both before take-off and during the flight. The results confirmed that the pilot was more exposed to the effects of the high-frequency electromagnetic field during the flight.
The analysis presented next was for a two–hour training flight by the Cessna C172 on the following route: Depułtycze Królewske–Lublin Airport–Krasnystaw–Depułtycze Królewski. During the flight, the approach to landing on runway 25 at Lublin Airport was performed. Measurements of electromagnetic field for individual frequency ranges are shown in
Figure 9,
Figure 10 and
Figure 11.
The highest value of the electric component of the electromagnetic field was recorded using the UMTS frequency band with E = 2.30 V/m. At this point, the aircraft had entered the instrument landing system (ILS) approach path. It is a radio navigation system that supports the landing of an aircraft in conditions of limited visibility. For the other frequencies tested, the electric field values obtained that affect the pilot was exposed are much lower. For the GSM 900 frequency band, the electric component of the electromagnetic field was E = 0.6 V/m, and for the GSM 1800, it was E = 1.05 V/m.
The next aircraft analyzed was the AT3. The flight took place on the route Depułtycze Królewskie–Lublin–Mielec–Depułtycze Królewskie (
Figure 12,
Figure 13 and
Figure 14). The total flight duration was 1.40 h.
For the training flight with the AERO AT3 aircraft, the highest value was also recorded using the UMTS frequency band with E = 1.15 V/m (
Figure 14). A similar value was recorded for the GSM 900 frequency with E = 1.14 V/m (
Figure 13) and the lowest was for the GSM 1800 with E = 0.68 V/m.
For the Robinson R44 helicopter flight, the highest value of the electric component of the electromagnetic field E = 1.89 V/m was read using the UMTS frequency. For the GSM 1800 frequency band, the maximum value of the electrical component was E = 1.16 V/m. For the oldest GSM 900 communication system, the maximum values (electric field) were two–fold lower than values obtained from measurements for other frequencies and equaled E = 0.89 V/m.
The statistical analysis involved the introduction of the values of the electric field intensity recorded by the ESM 140 dosimeter into the Statistica 13.0 software. The values of the analyzed parameters measured in the normal scale were characterized by the number and percentage, while those measured on a ratio scale by means of average, medians, standard deviation (SD), and range of variation. A 5% error of inference and associated significance level of p < 0.05 were adopted.
The data used in the statistical analysis were obtained during flights with all four aircrafts. First, results from a flight with the Cessna 152 aircraft were analyzed. The flight took 1.42 h on the route 1 from Depultycze Krolewskie to Bilgoraj and Tomaszow Lubelski using all frequency bands, from UMTS installations on the ground, as well as from onboard instruments (see
Table 2). The following table presents the characteristics of the electric field intensity E for individual frequency bands of the selected route. A sample group included a total of 15641 measurements registered for each frequency band.
The mean value of the electric field intensity using the individual GSM and UMTS frequency bands ranged from 0.007 V/m to 0.048 V/m. The range of the variable analyzed was from 0.000 V/m to 3.30 V/m. Differences for the indicated frequency bands obtained with the ESM 140 dosimeter proved to be statistically significant and are depicted in
Figure 18.
Selected results for one GSM1800 frequency range in which the highest values of the intensity of the electric component of the electromagnetic field were recorded during flights with one type of Cessna 152 aircraft was made on four routes. The variation of the electric field intensity for various aircraft routes is shown in
Figure 19.
The data presented in
Figure 19 consider the highest values of the electric field recorded for four aircraft routes for the GSM 1800up frequency band, which justifies the choice of the frequency band.
The numbers from one to four represent the flight routes researched, namely route 1: Depultycze Krolewskie-Bilgoraj-Tomaszow Lubelski, route 2: Depultycze Krolewskie–Rejowiec–Siennica–Pokrowka, route 3: Depultycze Krolewskie–Cycow–Rejowiec, and route 4: Depultycze Krolewski–Krasnystaw–Frampol.
Variation in the intensity of the electric field observed proved to be statistically significant and ranged from 0.000 V/m to 3.30 V/m. The mean value in time ranged from a minimum of 0.054 V/m to maximum of 0.101 V/m. The differences described are reflected in the values of the test function (
Table 3).
Student’s
t-test was performed in order to determine statistically significant differences between the values of electric component of the electromagnetic field for the aircraft routes (1,2,3,4) compared to the values obtained for the aircraft located on the ground (background) and is presented in
Table 4.
Having compared the values of the electric component of the electromagnetic field for the GSM1800 band, which presented the highest values recorded on different aircraft routes compared to the background (the airport), statistically significant differences were observed.
The next analysis presented included the results obtained during flights with the Cessna C172 aircraft on the route Depułtycze Królewske–Lublin–Krasnystaw–Depułtycze Królewskie for individual frequency ranges.
Table 5 presents the characteristics of the electric field intensity E for individual frequency bands of the Cessna C172. A sample group included a total of 7372 measurements registered for each frequency band.
The mean value of the electric field intensity for individual GSM and UMTS frequency bands ranged from 0.011 V/m to 0.074 V/m. The range of the variable analyzed was from 0.000 V/m to 2.18 V/m.
Next, the statistical analysis of the results obtained during flights on AT3 aircraft on the route Depułtycze Królewskie-Lublin-Mielec-Depułtycze Królewskie was performed. The characteristics of the electric field intensity E for individual frequency bands of the AT3 is presented in
Table 6. A sample group included a total of 7287 measurements registered for each frequency band.
The mean value of the electric field intensity for individual GSM and UMTS frequency bands ranged from 0.0046 V/m to 0.0629 V/m. The range of the variable analyzed was from 0.000 V/m to 1.17 V/m.
The results obtained during the flight of a Robinsson R44 aircraft were also statistically analyzed. The flight was made on the route Depułtycze Królewskie–Lublin–Kielce–Pyszkowice–Czestochowa–Krasnystaw–Depułtycze Królewskie. A sample group included a total of 14653 measurements registered for each frequency band (
Table 7).
The mean value of the electric field intensity for individual GSM and UMTS frequency bands ranged from 0.012 V/m to 0.0687 V/m. The range of the variable analyzed was from 0.000 V/m to 1.89 V/m.
Differences for the indicated frequency bands obtained with the ESM 140 dosimeter proved to be statistically significant and are depicted in
Figure 17. Results from flights with different types of aircraft were analyzed for each of the tested frequency ranges. The variations of the electric field intensity for various types of aircraft are shown in
Figure 20,
Figure 21 and
Figure 22.
The data presented in the figures relate to the highest electric field values recorded for four routes made with different types of aircraft in the GSM 900, GSM 1800, and UMTS frequency bands.