Can Portable Electronic Devices (PEDs) Interfere with Aircraft Systems? IEEE International Symposium on EMC Dr. Wolfgang Kreitmair-Steck
Dipl.-Ing. Wolfgang Tauber
EUROCOPTER Deutschland GmbH 81663 Munich/Germany e-mail:
[email protected]
Abstract - Passengers request to be allowed to work onboard of airplanes with PEDs of any kind. But this comfort is acceptable only if the airplanes are protected in such a way that all interferences of PEDs with aircraft systems, especially with flight critical systems are impossible. This paper reports of PED measurements performed in the context of the European research programme EMHaz. The result is a new overall limit curve of PED emissions. Based on this limit curve, the threat of coupling into antennas and into installed cable looms for helicopters is investigated and the possible effects and functional influences on aircraft systems are deduced. Keywords - PED, Electromagnetic Hazards, Electromagnetic Interference, safety, helicopter. INTRODUCTION
EUROCOPTER Deutschland GmbH 81663 Munich/Germany email:
[email protected]
PEDs the results were then extrapolated to the worst case limit curve proposed in document [1]. The threat levels were then compared to the sensibility levels of the specific avionics functions. INVESTIGATION STEPS Step 1:
Radiated Emission Levels
Figures 1 and 2 provide the data for radiated electromagnetic emission levels of a huge range of PEDs. Figure 2 summarizes reported measurement results from the literature as well as a number of additional measurement results, especially of more recent PEDs on the market. The emissions have been measured in 1 m distance from the radiating equipment in the frequency range from 100 kHz up to 4 GHz. The following (at the time of the measurements) most recent PEDs have been tested:
Motivation During take-off and landing phases of an aircraft, airlines strictly prohibit the use of any electronic device. Mobile phones have to be switched off during the whole flight time. Some people not involved in techniques often don’t understand why electronic devices have to be switched off. Others feel unsafe due to the danger of PED impact. The number of publications and reports on the subject is increasing. One representative report is e.g. reference [6]. It might be dangerous to deny the possibility of interferences with safety critical consequences without careful investigation. Therefore, it is one of the major targets of the European reseach programme EMHaz to analyze the potential impacts of PEDs and to define adequate protection measures. Targets and Approach of the Investigations The objective of the investigation is to clarify whether interferences with aircraft functions due to the radiation of PEDs used onboard an aircraft are possible or not. For sure, special attention has to be given to safety critical functions. Baseline of these analyses has to be the worst case limit curve for radiated emission of PEDs. To investigate a realistic case for the possible impact, radiation tests with the new EC 145 helicopter from Eurocopter had been performed: The PED radiation was simulated by a radiating antenna inside the helicopter; the coupling into antenna inputs and on helicopter cable looms was then measured, and the results were normalized to a field strength of 1 V/m. In order to obtain the real threat level of
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several mobile phones (dualband and triband); CD-, minidisk- and memory stick players; organizers; several notebooks from different manufacturers; photo cameras with integrated zoom and flashlight; a digital video camera.
One interesting result from the investigations is that the most recent technology has reduced the emission levels, especially in the most critical frequency range of 1 MHz up to 700 MHz. Figure 1 shows that between 10 kHz and 10 MHz the drivers of the emission levels are primarily the video cameras, the digital cameras and the laptops. On the other hand the mobile telephones increase the radiated emission values above 800 MHz significantly regarding the previously available test results. Mobile phones are the drivers of the emission values during ringing and during active communication. Taking into account the new UMTS standard frequencies one has to expect high emission values in the range of 700 MHz until 2.5 GHz. The standard RTCA DO 160D of the Radio Technical Commission of Aeronautics is required to be applied to all electronic equipment which is installed in a civil aircraft. Based on the assumption that it cannot be controlled what type of PED will be used in the aircraft, an emission limit curve (cf. Figure 4) has been established. This limit curve of PED emissions, which is a worst case envelope of all available measurement results, shows
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that in fact the PED emissions exceed the aircraft standard requirements almost over the whole frequency range.
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voltage levels in COM/NAV antenna inputs (by replacing the receiver by a measurement receiver); current levels on some selected helicopter cable looms according to figure 4; currents and voltages on specific simple cable configurations connected to special metallic boxes for avionics simulation.
Figure 1: Measurement results for the different groups of PEDs (and ambient levels)
Figure 4: Cable loom measurement on the helicopter ceiling.
Figure 2: Comparison of the PED measurements with previous results from RTCA and GEC studies.
Figure 5: Test set-up for helicopter measurements.
Figure 3: Proposed limit curve and its relation to the PED envelope, the DO 160D and the EN 55022 Class A Step 2 : Measurements on the Helicopter EC 145 Test Set-up and Types of measurements The general used test set-up is shown in Figure 5. A radiating antenna, representing a PED, was positioned on different locations within the helicopter cabin. While radiating the following coupling levels were measured:
In general, the applied frequency range was from 100 kHz up to 1 GHz. This has been limited to max. 200 MHz for current measurements however. In order to get an impression of the effect of multiple PEDs radiating at the same time, some tests were performed with two radiating PEDs simultaneously. Results All measurement results were normalized to 1 V/m field strength in order to compare them with other test results, e.g. HIRF Transfer Function Measurement results. In a second step, the results have been related to the actual limit curve for PEDs (see Figure 3). This approach is shown in detail only for the example of helicopter cable loom currents. For all other results, only the extrapolated results are presented in this article.
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cabling from the COM receiver and connecting the antenna cables to the measurement equipment. The analyzed frequency range was selected with respect to the associated receiver frequency range including possible sidebands. The envelope of the worst case voltage on a 50 Ohm input of the measuring equipment extrapolated to the PED limit curve is shown in Figure 8. 0 -10 dBµV (relative to PED envelope) .
Helicopter specific Cable Loom Currents For the measurements some specific cable looms in the helicopter have been selected, representing different characteristic cable routings. In addition, an extra cable loom with defined cable routings was integrated connecting two specific measurement boxes for avionics simulation. For each loom, the current was measured from 100 kHz up to 200 MHz for vertical and horizontal radiated electromagnetic fields from three different positions in the helicopter cabin. Summarizing all results, Figure 6 shows the worst case envelope normalised to a 1 V/m field. 30 20
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Figure 8: Extrapolated voltage levels on COM receiver antennas resulting from 1 radiating PED
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Figure 6 : Worst case current curve on helicopter cable looms coming from PEDs (normalized to 1 V/m electromagnetic field). 0 -10 -20 -30 -40 -50 -60 -70
Step 3 : Sensibility Levels
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NAV Antennas The measurements were performed on all installed NAV receivers: ADF, VOR, Marker, Glide Slope, DME, Radar Altimeter. In order to get the coupled levels in the input of the receivers, the measurements were performed similar to the measurements of COM antenna couplings. The applied frequency range was selected respecting the associated receiver frequency range. The envelope of the worst case voltage on a 50 Ohm input of the measuring equipment extrapolated to the PED limit curve is shown in Figure 9. No GPS was installed, but since the working frequency is not far from 1 GHz it seems to be adequate to assume 25 dBµV as the respective threat level.
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Since the RTCA-Standard (document [2]) defines calibration levels, in general it is necessary to perform radiated Transfer Function measurements for every new aircraft in order to get the real expected current levels on the aircraft cable looms.
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Figure 7 : Extrapolated worst case current curve for helicopter cable looms resulting from one radiated PED. The extrapolation of this envelope curve to the proposed limit curve for the emission of PEDs leads to the maximum expected currents on any helicopter cable loom (see Figure 7). Tests with two PEDs, radiating at the same time with the same frequency from different positions in the helicopter have shown unmistakably that an increase of up to 10 dB in cable loom current could be possible. COM Antennas The measurements were performed on all installed COM receivers of the specific helicopter tested: 2 VHF AM receiver, 2 VHF/FM receiver, and 1 UHF receiver. In order to investigate the coupled levels in the input of the receivers, the measurements were performed by disconnecting the antenna
Signal Lines It is assumed that all aircraft electronic equipment has passed BCI and HIRF tests according to reference [2] and are therefore compliant to those levels (see Figure 10 for the most restrictive requirement of CAT J). Consequently this equipment is guaranteed to resist those current levels without signal interferences. Evaluating the extrapolated currents of Figure 10, a rough estimation shows that this equipment is tested with higher levels than possible levels of PED emissions, irrespective of the specific CAT level. This is even true for the case of two PEDs radiating at the same time with the same frequency. COM Receivers The assumed receiver sensitivities of COM receivers are: VHF /AM Squelch opening at about 2 µV VHF / FM Squelch opening at about 0.5 µV UHF Squelch opening at < 1 µV
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ADF, Marker, GS shall have no problems with respect to the interference levels; VOR interferences cannot be excluded; GPS and DME are the weakest points of the avionics.
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CONCLUSION
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The results of our present research on possible PED hazards for aircraft could be summarized with the following remarks:
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Figure 9: Extrapolated voltage levels on NAV receiver antennas resulting from 1 radiating PED
Signal lines are immune with respect to PED emissions; for the VHF/FM type of COM receivers a possible interference cannot be excluded; NAV receivers are in general immune against PED emissions, except VOR, DME, and GPS; GPS is especially threatened by mobile GSM and UMTS phones. REFERENCES
[1] Kreitmair-Steck, W., W. Tauber. Aircraft Hazards by Using Portable Electronic Devices (PED). In: Proceedings of the EMC 2002 / Wroclaw, June 25-28, 2002. Wroclaw 2002. [2] RTCA / DO 160D. Environmental Conditions and Test Procedures for Airborne Equipment. [3] RTCA / DO-233. Portable Electronic Devices carried on board aircraft. SC-177, August 1996 GEC-Marconi. "Carry-On" Passenger Equipments. Report 277/EMC/102/45, 1995. [4] Tauber, W., L. Jeancoux. Test Report for Personal Electronic Devices. Internal Report EMHAZ-ECD-REP-001, Ottobrunn, March 2001 [5] Tauber, W., L. Jeancoux. State of the Art Analysis of the PED, HIRF and HPM threat. Summary of the investigations. EMHAZ-ECD-REP-001A, Ottobrunn, June 2001. [6] Ross, E. Personal Electronic Devices and Their Interference With Aircraft Systems. Langley Research Center Hampton/Virginia, NASA / CR-2001-210866, June 2001.
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Figure 10: Conducted Susceptibility Test Levels for Rotorcraft / CAT J These levels have to be related to the expected voltage levels of Figure 8. Analyzing these results it seems obvious that the VHF/FM sensitivity level is well within the levels which could be coupled by radiating PEDs (except mobile phones). In evaluating this finding it should be taken into consideration, that worst case conditions have been the baseline for our research. For the other radios the margin of at least 10dB with respect to the worst case assumptions should provide sufficient margin to guarantee the correct function. NAV Receivers The NAV receiver sensitivities are approximately the following VOR LOC ADF DME Marker Glide Slope GPS These levels have Figure 9.
about 2.4 µV about 1 µV 70 µV (for antenna gain = 0 dB) about 10µV 200 µV about 1.0 µV about 0.025 µV to be related to the expected voltage levels of
The results of that analysis could be summarised as follows:
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BIOGRAPHICAL NOTES Dr. Wolfgang Kreitmair-Steck, MBA, received his Dr. degree in 1989 from Univ. of Tübingen. Since 1989 he is working for Eurocopter Deutschland as a programme manager for systems technology and EMC research.
Dipl.-Ing. Wolfgang Tauber received his Dipl.-Ing. from the TU Munich. He started his career in 1978 at Dornier Systems with NEMP studies and NEMP simulation. Since 1989 he is engaged in NEMP, HIRF, TEMPEST, Lightning and EMC measures at Eurocopter Deutschland.
