For aerospace issues other than PEDs, see this topic.

Passenger Electronic Devices

For many years there has been continuing controversy over whether passengers on commercial airline flights should be allowed to use their electronic equipment (cellphones, laptops, CD players etc) on board during flight, and if so, during which phases. Numerous papers and articles have appeared on the subject. As of October 2013, the US FAA have approved the use of passenger electronic devices (PEDs, but not including cellphones) in flight, in the following manner:

Most commercial airplanes can tolerate radio interference signals from PEDs.

The FAA should provide airlines with new procedures to assess if their airplanes can tolerate radio interference from PEDs.

Once an airline verifies their fleet is PED tolerant*, it may allow passengers to use handheld, lightweight electronic devices – such as tablets, e-readers, and smartphones, at all altitudes.

In some instances of severe weather with low-visibility, the crew should continue to instruct passengers to turn off their devices during landing.

PED ARC members and industry and FAA experts accomplished a safety assessment by using available data.  The assessment concluded that PEDs can be addressed to provide an acceptable level of safety for expanded PED use. The PED ARC report contains 29 recommendations including technical, operational and safety communications aspects of PED usage.

The group did not consider the use of electronic devices for voice communications during flight because Federal Communications Commission (FCC) regulations prohibit any airborne calls using cell phones.

The ARC recommends that airlines can expand PED use by the following path:

Use a Safety Management System (SMS) risk analysis to mitigate hazards associated with passenger use of PEDs.

Make aircraft PED-tolerant.

Train crew members to recognize and respond to potential PED interference.

Develop standardized messaging to better inform the public regarding PED-tolerant airplanes and PED usage Policies.

(FAA Fact Sheet – Portable Electronic Devices Aviation Rulemaking Committee Report, October 31, 2013)

* "PED tolerant" in this context means that the aircraft is certified to RTCA DO-307, "Aircraft Design and Certification for Portable Electronic Device (PED) Tolerance", November 2007.

** In December 2013 the CAA announced that European operators would be able to follow suit. See the CAA website for the current position. **

The following examples have been abstracted from the NASA Aviation Safety Reporting System (ASRS) database, available from http://asrs.arc.nasa.gov/search/reportsets.html.

May 2011, CRJ200 

After departing, climbing through ~ 9,000 feet we received an EFIS COMP MON caution msg. Flight Manual directs pilots to slew compass to reliable side. It was apparent neither side was correct with the Captain's, Mag Compass, and First Officer's headings all different. We were cleared direct to a fix. Multiple attempts were made to match the headings with only temporary results. The Captain elected to hand fly while the headings mismatched. While the FMS was taking us in a direct line, with the wind shift while hand flying the aircraft ended up 4 miles south of the original "direct to" course. ATC called and asked if we were going direct, I told them we are having heading problems and asked how our heading looked. He told us 10 right and direct when able. On this trip we flew this same aircraft for 9 legs and did not have this problem on any other flight. In the past I have had similar events with speculation that cellphones left on may contribute to the heading problems. I made a PA asking our passengers to check their cellphones and make sure that they are off. Short of flying with both headings in DG we attempted to slew the compasses together again, and the EFIS COMP MON was cleared with no further messages. Our Flight Attendant called and asked if that had helped, I said yes, what did you do? He stated he walked through the cabin and spoke to each of the 12 passengers. A passenger in Row 9 had an iPhone in the standby mode, not airplane mode or off. He showed the passenger how to turn the phone off fully. The flight continued to destination with no further problems. In my opinion and past experience the cellphone being on and trying to reconnect to towers on the ground, along with the location of row 9 to the instrumentation in the wing caused our heading to wander. The timing of the cellphone being turned off coincided with the moment where our heading problem was solved. Eight other flights in the same aircraft in two days span completed without a similar event. 

August 2007, Boeing 737  

I had this exact problem about 10 years ago under the same circumstances. This event occurred in the same type of acft, a B737 [non glass]. During clbout and initial cruise, I noticed the nav radios were in auto update but they were not updating. I then chked the FMC status of the IRS' and FMC radio updates. It showed DME updating fail. Before I completed a position shift, I (capt) called the flt attendants and asked they do a walk through and chk for any PED's. They found a pax with a handheld gps, Garmin nuvi model 660. Once this was turned off, the FMC DME updating went from fail to on and the radios started to update again. The flt continued and landed without incident. The acft was a B737 'classic' meaning round dials and not EFIS. It had two IRS' with a single FMC but 2 FMC headsets in the cockpit.

Callback conversation with rptr revealed the following info: the rptr stated that he was concerned that because he had experienced this same type of event three times in the last 10 years and all in the b737 acft with the FMS system but no glass, that there may be a common thread. One previous event was confirmed as caused by portable gps and the other may have been a cell phone call made just prior to landing. In the event reported here, the DME failing to update was the first indication. He now flies the B737 classic as well as the B737 NG's. The NG's appear to be more electromagnetically robust. 

June 2006, Airbus A320 

We were acr x dsnding via the WEEDA 1 arr into DTW. We had ZOB freq blocked and unusable by a pax cell phone searching for svc (the pax thought he had it off). The pax was in seat 22-d which would have been near the antenna location. ATC confirmed that no one else was receiving the signal but us. The signal quit about the time the cell phone was turned off. During the event, all coms on the freq to and from us were totally blocked whenever the phone would search for svc. This occurred about every 20 seconds and would last for about 10 seconds duration. 

September 2005, Boeing 737-800 

Flt xxx, a B737-800 zzz-zzz1. After tkof near max gross wt, prior to flap retraction received a resolution advisory 'maintain vert spd' with red area not to decrease to 1500 fpm or less rate of clb. Delayed thrust reduction and flap retraction to comply with RA and scanned for tfc. TCAS indicated a co-alt target (red circle) less than .01 behind us. This occurred at 1000 ft msl, and clred up approx 30 seconds later. Second RA occurred near 12000 ft msl. Same target indication, a red circle co-alt less than .01 behind us. Now the RA advised 'DSND, DSND, DSND.' we started the dscnt, advising ATC of the RA and scanning for tfc. ATC advised us there was nothing in our vicinity, and TCAS was clean of targets for nearly 10 miles. Began to suspect EMI from cabin. Started to clb again -- ignoring the TCAS RA commands. The box was quiet. Recycled the xponder power. At 14000 ft, we got a third TCAS RA. Same display and DSND callouts. We ignored them. Called cabin for a chk of equip that may have caused interference. Found pax seated in first class with laptop on. Model HP 6220 with wireless function enabled. The pax closed the lid when we were boarding on the gnd, putting the laptop into standby/hibernate mode. Once he disabled the wireless function, all ok. The tech people should get a heads up on this. Guess the wireless function was trying to establish a connection and each time it did (or a fraction of the attempts) was interpreted as a TCAS signal. (coalt, .01 behind us.) The display was a red circle, not a red square. No yellow or white circles prior to any RA events. Is the TCAS antenna cable shielded from internal (cabin computers) EMI? I have not seen an event like this before. What makes it hazardous -- is the rate of clb at dep, prior to acceleration and flap retraction and the 1500 fpm or greater rate of clb. (transcon near max tkof wt.) With the proliferation of wireless computers, I am sure we will be seeing this more often. 

June 2005, CRJ700 

On clbout from CLT we heard what sounded similar to a fax machine sound or a modem sound. We thought it was just an anomaly, but it happened again and again in repetitious intervals. I asked the capt what he thought, and he said it was probably a 2-way pager because a similar incident occurred to him a few trips ago. He found that out after asking a flt attendant to investigate the situation, and she found someone was typing messages above 10000 ft msl so that they could be sent upon lndg. We asked our flt attendants to take a walk through the cabin to see if anyone was using anything of the sort. None were found after she rpted back to us. However the annoying noises still continued. It was annoying and loud enough to almost cause us to almost miss radio calls. So, an announcement was made to please make sure cell phones and 2-way pagers were turned off because it was interrupting our coms, and if this was not done we may have to return to CLT. After that, nearly the entire plane got up to find and make sure all the devices were turned off. The noises then stopped. No make/model info was gathered because: the flt attendants were doing their svc, we were still clbing, and we assumed no one was going to admit guilt for fear of prosecuting action. Recommendation: I would highly encourage many more indepth studies to be performed prior to allowing cell phones and other coms devices to be used on board acft inflt. 

June 2004, Boeing 737-700 

On being vectored for ILS rwy 8 at bur, we were given our final loc intercept hdg, and clred to intercept the loc. I was the PF and had the autoplt engaged. The MCP was set up in the HDG mode. Once I turned to the intercept hdg using the bug, I selected VOR/LOC to capture the loc. Both the PNF and I observed loc captured and the acft turning to intercept. As the acft apched the inbound course, I glanced at the altimeter to calculate where my alt callouts would be made. When I looked back over to my primary flt insts, I noticed we had flown through our inbound course, and the acft was in a 30 deg l-hand bank. I noticed it showed ctl wheel steering in the lateral mode. At approx the same time I was calculating my callouts, the PNF was tuning in the twr freq. We both looked up to notice the discrepancy at the same time. I immediately initiated a 30 deg bank rhand turn back toward the inbound course. We were approx 30 degs off course. Before we could tell apch we were going to miss the apch, the ctlr immediately assigned a clb and hdg. We were vectored back around and executed an uneventful ILS rwy 8 and landed without incident.

I feel the most important factor was the fact that I allowed myself to become distr during a critical phase of flt. We all have seen the autoplt capture a loc numerous times without incident, and I feel this lead me to take it for granted. I should have done all my calculations before beginning the apch. I am not sure why the MCP went from a VOR/LOC capture to ctl wheel steering mode. We later talked to the flt attendants, and they observed a pax who may have been using their cell phone. I suppose radio interference is possible. I believe this incident has taught me to take my already heightened sense of awareness to a higher level. Especially during a critical phase of flt.

Supplemental info from ACN 619585: I saw that the acft was still in a 30 deg l bank and the hdg had gone through loc course and was passing 030 degs. I noticed some loc needle modulations on the missed apch. In talking with the flt attendants, they stated that they suspected a pax of hiding below seat level and using his cell phone during the apch. I am not certain the cause of the event but, I suspect that as the autoplt had the acft in a 30 deg l bank to intercept the loc, cell phone interference caused the loc needle to deflect full scale to the l. The autoplt continued the turn, trying to intercept the deflected needle and when the needle swung back to a full r deflection, the autoplt reverted back to ctl wheel steering, leaving us in a 30 deg banked l turn.  

February 2004, Boeing 737-300 

We were at 2000 ft msl on a hdg clred to maintain 2000 ft till established and clred for the ILS rwy 13 at JAX. The loc came alive and the FO who was flying began a dscnt to 1700 ft which was the GIA. Just after beginning the dscnt, the loc began to ping from side to side on both capt and FO's insts. We informed JAX apch of the prob, clbed back to 2000 ft and were given another vector as we had gone through the course. There were no flags and the ident was good. Apch then said if we continued to have a prob with the ILS, we would be given a surveillance to rwy 7. I asked if anyone was in the clr zone and was informed that there was not. Additionally, the acft preceding us and behind us had no loc probs. We continued to have difficulty with the loc and ended up flying the surveillance to rwy 7. The ILS seemed to operate fine on the gnd and since we had no probs with it earlier, I thought perhaps someone had used some electronic equip in the cabin during our apch. I chked with the flt attendants and, in fact, a guy had operated a palm pilot of some sort during the apch. We were unable to talk to the pax because he had already left the acft by the time we talked to the flt attendants. I assumed that was the prob and advised the crew who took the acft at jax what had occurred. I did not write up the occurrence in the logbook. After further reflection, I probably should have because there is no way I can prove the palm pilot was the cause. 

November 2003, MD-88 

During tkof roll, received 'heading' annunciations on FMS flt mode annunciator panel (FMA) with about a 10 deg heading split. We elected to continue the tkof rather than abort at high spd and noted that the FO's heading matched the rwy heading more closely. This prob occurred intermittently for the next 5 mins with an 8-10 deg hdg split and the heading channel (roll window) blanking out on the FMA. (the autoplt could not engage in this condition.) I suspected electronic interference and directed the flt attendants to sweep the cabin and chk for use of personal electronic devices while the FO made an announcement to request pax double-chk that devices were turned off. Flt attendants also had pax chk devices in carry-on luggage. Shortly after directing these chks, the prob clred up, capt and FO heading refs agreed with each other and the whiskey compass. There were no probs for the remainder of the flt, including after we allowed laptop computers to be used. For additional ref, this was an AHRS acft (did not have IRS-based heading sys). Also, although no pax admitted having any devices on, a flt attendant who was seated in the back later mentioned that she heard at least 1 cell phone ringing on tkof roll. (the flt attendants had made the standard preflt PA to turn devices off.) We have an abnormal proc in our manuals for heading errors, but it wasn't effective during this event. Since it was VFR, this didn't seriously degrade safety, although it was a distracting event in a busy ATC environment. Had this happened during an apch in IMC conditions, it would have been more serious. Perhaps the traveling public needs to be made more aware that PED use during flt is a serious concern. 

October 2003, DC-9 50 

While level at 6000 ft 5 mi SE of BUNTS intxn at 250 kts clean, we had just been handed off to PHL final apch when we got a TCASII RA to clb full scale 6000 fpm with no proximate tfc preliminaries. The FO as PF immediately began a max performance clb while I went heads up to acquire the tfc which had popped up at 12 o'clock pos less than 1 mi alt -03. I did not see any tfc and by the time I could get a word in edgewise on the freq to tell ATC about the RA, the RA had evaporated with no 'clr of conflict' annunciation. (initially, the target had appeared to clb with us, maintaining a -00 alt differential.) The FO leveled off at 7000 ft and then began a dscnt back down to 6000 ft and ATC said there was no tfc near us which should have provided an RA. I tested the TCASII (test ok) and asked the lead flt attendant to do a PED walk, she rpted no obvious PED use. As apch handed us off to LCL, he told us there was VFR tfc below us at 3500 ft at the time of the RA. When we got to the gate, the lead came up to say that a flt attendant had caught a lady trying to call her daughter on her cell phone at the time we 'pulled up.' 

April 2003, DC-9 

During clb and while talking to SDF dep, we got a TCAS RA showing a target at 12:00 o'clock, level and showing a clb. TCASII commanded a full scale (6000 fpm) clb and I as PF increased clb rate to 3000 fpm (the max we could safely do). We called SDF dep to rpt the RA and ask about the target. He said he had no target within 5 miles of us, so I hit the TCAS press to test button. TCAS test rpted 'test ok.' I then asked the lead FA to do a PED walk and he rpted back that a computer was in use in violation of the sterile environment condition. The computer, a 'dell inspiration 8000,' with rptedly no xmission capability and no external power pack, was shutdown for the remainder of the flt and TCAS functioned normally with no further false RA's or TA's.

Callback conversation with rptr revealed the following info: the PIC stated that the flt had been clred to 10000, so there was no alt dev involved. The rptr stated that he had no direct knowledge as to the reliability of the TCAS sys, or it's ability to detect 'real' tfc while resolving a false warning instigated by a pax's electronic device. Rptr advised the company of the incident, but the only feedback was from the union safety representative who simply asked him if he had responded to the RA. The PIC said that the company appears to shy away from these issues of 'PED's'. The PIC talked with the pax who appeared to be quite contrite over the issue, while failing to state her reasons for using the computer prior to any FA announcement. The rptr believes that the issue of reliability of the TCAS sys during a scenario such as this is a key safety issue. 

July 2002, Boeing 767 

Instrument malfunction autoplt abnormality. Clr of clouds, FL350, econ cruise mach .78, smooth air. The FO was flying this leg when 30 nm NE of LEFKO intxn on green 26 proceeding direct to REDFIN, JAX center clred us direct REMIS for a warning area had gone active. At approx xa:44 ENE of REMISS we encountered the event. First thing I noticed was the amber autoplt and auto throttle EICAS msg and audible alert for a disconnect. We also noticed solid yellow lines that went through all flt mgmnt ctl data on both capt and FO ADI's and HSI's. I looked at the top EICAS eng instrument and noted no N1 or EGT digital readouts, only white circles remained. Lower EICAS reflected the same. No digital info for N2, FF, oil pressure, oil temp, oil quantity, VIB. Both CDU's were blank. An immediate chk of the electrical panel indicated no malfunctions, a test of indicator lights revealed no burned out lights. Center autoplt was engaged and showing panel active with normal indications. Standby ADI indicated we were starting a left bank. With warning of autoplt and auto throttle disconnect I grabbed the yoke and hit the autoplt disconnect switch and directed the FO to fly. He maintained level flt and stated that the autoplt was still engaged. I attempted to disengage the autoplt with the disengage bar by pulling it down and waiting. The white autoplt CMD light remained on. I went back to the yoke and again hit the disconnect and felt the yoke pressure the FO was holding. I called ATC and advised we were having some kind of an electrical anomaly. Just after the call to ATC the autoplt disengaged and the white CMD light went out and all systems returned to normal ops. I directed the FA 1 to search the acft for unauthorized electronic equip being used. I then rpted to ATC that ops were normal. The event lasted approx 45 secs. I questioned ATC reference military activity in the area which may have affected our equip. Dispatcher was called. FA 1 rpted a cell phone was in use by pax. I directed FA 1 to have it turned off and confiscated to me. Pax stated it was a new phone by AT&T, model Siemens CEO168, he was installing new phone numbers in data bank and not talking on phone. Maint was called and stated the acft had no previous history of this type of event. One area of concern was a potable water tank gauge quantity prob. The FO and I completed a complete systems chk concluding ops normal. With passenger's cell phone off and in my possession the FO and I agreed with dispatcher to continue the flt with caveat that should any other similar event occur we would land asap. The FO and I noted no recall EICAS or status history. From navigation point REMISS we proceeded uneventfully to SFO.

Callback conversation with rptr revealed the following info: the acft had just been vectored to clr a military area over the gulf of mexico at the time of the incident. Even though there was some suspicion that there may have been a military activity that could have caused the prob this could not be determined. The cell phone that was on at the same time is rpted to be a powerful new type in the search mode. The location of the phone during the incident was the cabin at seat row x which is roughly above the electronics area. During the failure the standby eng instruments activated. In maint follow up action it was thought that a voltage spike off the left generator ctl could have been a possible cause. There was rpted to have been five different 'black box'  components replaced during maint. The digital recorder was read and it verified the failures occurred as rpted by the crew. During the course of the failures there were no status or alert messages displayed and none were able to be recalled after the fact. The rptr reiterated again that the total time of the incident was no more than 1.5 mins.

2013

FAA Calls for Fix to Remove Interference on Airplane Display Units

The Federal Aviation Administration is pushing to replace certain older airplane cockpit instruments manufactured by Honeywell International Inc., claiming that they may be susceptible to Wi-Fi interference.

The request comes as U.S. regulators finalize recommendations for easing restrictions on in-flight use of personal electronic devices (see above).

In a proposed directive released earlier this month, the FAA said Wi-Fi systems may interfere with the Honeywell phase 3 display units aboard 157 Boeing airplanes in use by various U.S. airlines. These display units are critical for flight safety, providing crew members with information such as airspeed, altitude, heading, and pitch and roll.

According to the FAA, the issue was discovered two years ago during testing to certify a Wi-Fi system for use on Boeing 737s.

“This testing determined that certain Honeywell phase 3 display units exhibited flickering and blanking when subjected to radio frequency emissions in Wi-Fi frequency bands at radiated power levels below those that the displays are required to tolerate for certification of a Wi-Fi installation,” the FAA explained in its proposed directive. In some cases during testing, display units went blank for as long as six minutes.

Though the FAA seemed previously content to make the change optional, as pointed out by Honeywell Aerospace Chief Executive Tim Mahoney in an interview with Reuters, agency officials have now made the decision to propose a mandatory replacement because “the unsafe condition described previously is likely to exist or develop in other products of the same type design.”

If not corrected, says the agency, the unexpected loss of information during a critical phase of flight, such as an approach or takeoff, could result in a temporary loss of airplane control and even a crash. U.S. costs for the upgrades are estimated at $1.6 billion, but could ultimately be higher if the new rules are adopted internationally. The Boeing 737 is widely considered to be the world’s most popular passenger jet, with over 10,000 orders placed globally since 1967.

2000

CAA cellphone measurements

A campaign of measurement was carried out by the Civil Aviation Authority in 2000 on two aircraft types - a Virgin Atlantic Boeing 747-243B and a BA Boeing 737-236 - to evaluate the effect of mobile phone transmissions on equipment in different locations in the aircraft. It observed that "by comparing the test results with the qualification levels (for RF immunity, in RTCA DO-160), it can be seen that interference levels produced by a portable telephone, used near the flight deck or avionics equipment bay, will exceed demonstrated susceptibility levels for equipment qualified to standards published prior to July 1984. Since equipment qualified to these standards are installed in older aircraft, and can be installed (and is known to be installed) in newly built aircraft, current policy for restricting the use of portable telephones on all aircraft will need to remain in force."

Also, "for equipment approved prior to December 1989, no qualification tests were required for susceptibility at portable telephone frequencies of 1800 MHz. Also, versions C and D of the Standard permit increased interference susceptibility for equipment installed in a partially protected environment assuming that the interference source is external to the aircraft. For example, for test Class T, a qualification test level of 5V/m is permitted for equipment installed in a well protected avionics bay. Few aircraft can claim such a level of protection when the interference source is inside the aircraft. Equipment approved in accordance with earlier standards can remain in production and continue to be installed in newly built aircraft which are derivatives of types first certificated in an earlier period. The significance of this point is that the equipment installed in an aircraft will be a mix of items which have been qualified to different levels of interference susceptibility."

(CAA Report, Interference Levels In Aircraft at Radio Frequencies used by Portable Telephones, 2nd May 2000)

A further set of tests are described in CAA Paper 2003/3:

"Tests that exposed a set of aircraft avionic equipment to simulated cellphone transmissions revealed various adverse effects on the equipment performance. Although the equipment demonstrated a satisfactory margin above the original certification criteria for interference susceptibility, that margin was not sufficient to protect against potential cellphone interference under worst-case conditions.

In October 2002, a set of avionic equipment was tested under controlled conditions in a test chamber for susceptibility to cellphone interference. General aviation avionic equipment, representative of earlier analogue and digital technologies, was used. The equipment, comprising a VHF communication transceiver, a VOR/ILS navigation receiver and associated indicators, together with a gyro-stabilised remote reading compass system, was assembled to create an integrated system.

The tests covered the cellphone transmission frequencies of 412 (Tetra), 940 (GSM) and 1719MHz, including simultaneous exposure to 940 and 1719MHz. The applied interference field strengths were up to 50 volts/metre for a single frequency, and 35 volts/metre for dual frequencies.

The following anomalies were seen at interference levels above 30 volts/metre, a level that can be produced by a cellphone operating at maximum power and located 30cms from the victim equipment or its wiring harness.

Compass froze or overshot actual magnetic bearing.

Instability of indicators.

Digital VOR navigation bearing display errors up to 5 degrees.

VOR navigation To/From indicator reversal.

VOR and ILS course deviation indicator errors with and without a failure flag.

Reduced sensitivity of the ILS Localiser receiver.

Background noise on audio outputs.

Most anomalies were observed at 1719MHz."

(CAA PAPER 2003/3. Effects of Interference from Cellular Telephones on Aircraft Avionic Equipment)

A 2005 document states that "Over the past ten years, the CAA has received 65 MORs (Mandatory Occurrence Reports) relating to interference experienced with one or more of the aircraft systems that cited PEDs as a factor, which were not subsequently found to be caused by a system's malfunction."

(CAP 756, Portable Electronic Device Generated Electromagnetic Fields on board a Large Transport Aeroplane, November 2005)

The current guidance to airlines and passengers is contained in CAA publication CAP 1066, published in July 2013. Extracts include:

The use of mobile phones on board aircraft to make voice calls or send texts is generally prohibited on UK airlines, unless the aircraft has been especially equipped with an approved mobile phone control system.

Whilst the aircraft is taxiing, with the cabin doors closed and engines running, there is still a potential risk of mobile phone signals interfering with ground communication between flight crew and air traffic controllers. Because safety must be guaranteed before any use of a system, service or device is permitted, an aircraft operator (airline) must successfully prove that no interference risk exists before they are able to permit voice calls and text messaging while the aircraft is taxiing to the terminal.

British Airways is currently undertaking a CAA approved trial on board all its aircraft which allows passengers to use mobile phones for voice/text functions while taxiing to the terminal after arrival.

Mobile phones, and many electronic gadgets, when not in Flight Mode, will continue to transmit electromagnetic signals as the device attempts to maintain contact with a communications network. These signals will normally, as in the case of mobile phone networks, be commanded to transmit at the devices’ maximum power to maintain the connection between the device and network if the aircraft is in flight and thus at a significant distance from the network’s primary field of coverage, i.e. the ground.

The cumulative effect of a large number of mobile phones or T-PEDs being used simultaneously when not in Flight Mode, particularly during the critical phases of flight, such as take-off and landing, remains a serious concern.

In addition, the cumulative effect of the spurious emissions from a large number of PEDs being used simultaneously could result in an increase in electromagnetic noise within the aircraft that could affect the sensitivity of the aircraft receiver systems, preventing them from being able to detect the faint electromagnetic signals used for such purposes as navigation. Therefore, in critical phases of flight, PEDs should remain switched off unless informed otherwise. The CAA recognises that some non-transmitting PEDs will remain operational, such as watches, medical implant stimulators, hearing aids, etc, but all of these devices are understood to present extremely low emissions and the cumulative effect of them is considered low, and these are not a significant contributor to the overall EM noise that poses the risk to the aircraft receivers, so their use will continue to be accepted during all flight phases.