JEDDAH — You are piloting an executive jet at 200 kilometers an hour along a runway; you rotate the aircraft off the ground and use full power to climb away and — all the electrical generators fail. At this point you really begin to work for your riyals. Not a speculative example is this, but an actual one. Securing the aircraft on battery backup, the pilot checked to see what was happening and discovered that at the point of take-off his VIP passenger had made a call at exactly the moment of electrical failure. Proof that the cell phone caused the incident? Perhaps. Certainly evidence. Asking the passenger to switch the telephone off and recycling the generators back on-line, the systems were restored to normal and the flight continued uneventfully.
While there seems to be no positive proof that cell phones or some other non-trivial electronic devices cause navigation or system failures, anecdotal evidence is strong and pilots have reported anomalies with their navigation equipment that seem to be linked to the use of personal electronics in the cabin. And before anecdotal evidence is dismissed out of hand, it frequently justifies empirical investigation that later proves it true.
The phenomenon of electromagnetic interference with avionics (aviation electronics) is not new and neither is it mere speculation. It has happened — and to military aircraft that one would assume to be shielded against such interference.
When the Blackhawk helicopters were introduced to service in the late 1980’s, five crashed soon after. Investigators found the cause to be strong electromagnetic interference from radio and radar transmitters in the flight control systems of the aircraft. If it can happen to military aircraft, perhaps we should at least be concerned about commercial aircraft.
You are a pilot on final approach to touchdown; of the six information screens in the cockpit feeding you essential data, four go blank. Within two minutes of touchdown and before the pilots could run a diagnostic check, all the screens came back to life. “I suspect that was to do with cell phones,” the pilot said. Cell phones? Perhaps; every air traveler has seen the “Hello-mom-I’m-landing” syndrome.
In 1992 the Radio Technical Commission for Aeronautics (RTCA) Special Committee 177 was formed at the request of the US Federal Aviation Authority (FAA) to examine the possibility of interference with aircraft systems from passenger portable electronics most particularly computers, game machines and cell phones. Founded in 1935, RTCA today includes about 335 government, industry and academic organizations from the United States and around the world.
Bruce Nordwall, a specialist in avionics, writing in Aviation Week and Space Technology in September 1996 said that the RTCA advisory group was worried that no group was testing or systematically tracking the potential effect of passenger electronics on avionics. It was also concerned that the flying public is not being educated about the potential hazards, and that the airlines must work out how to deal with the issue themselves.
The RTCA report recommended developing and installing devices in aircraft cabins that could detect and locate potentially harmful radiation coming from within the aircraft. However, the problem of interference involves both the inside and outside of an aircraft’s fuselage. Navigation systems are particularly vulnerable because they have parts devised to detect and act on signals coming from “outside” and radio-based systems are particularly susceptible to low levels of interference. Nordwall said that aircraft control systems were located entirely within the aircraft and were shielded from absolutely any signals not coming from one of their own devices; they are also not radio-based, but are based entirely on electrical signals conducted through wires as are most computer networks. Navigation avionics, on the other hand, must have some designed sensitivity — to as low as only micro-volts per meter — to environmental radio signals in order to perform their functions. Being outside the aircraft, the radio and navigation antennae get some protective attenuation from the fuselage from radiation originating inside the aircraft. Non-radio systems generally have higher signal levels, and so are less susceptible to low levels of interference. The fuselage provides a shield from electromagnetic emissions from inside the aircraft. However, passengers can still phone from inside the hull, as any traveler will know. Couple that with the sensitivity of the external antennae and perhaps there is an area for examination.
There are two other factors to add to that. A cell phone increases power output the further it gets from an available cell. First, flying at 12 kilometers altitude will cause cell phones to increase their output to seek a cell. Secondly, pilots Arab News spoke to all focused on the fact that the interferences with aircraft systems that they had experienced and thought to be caused by cell phones were not consistent. It was that inconsistency that concerned them. In other words, they could not prepare for a predictable effect and so if and when it came, it had to be handled ad hoc.
One senior captain told Arab News that two passengers were exchanging text messages in the aircraft. “That caused interference with the VHF and navigation information,” he said. They were asked to stop and when the phones were turned off, all returned to normal. Going with all the weight of their experience, it is quite clear what should be done. They say that devices, “including laptop and palmtop computers, audio players/recorders, electronic games, cell phones, compact-disc players, electronic toys and laser pointers, have been suspected of causing such anomalous events as autopilot disconnects, erratic flight deck indications, airplanes turning off course and un-commanded turns.”
They recommend that devices suspected of causing these anomalies be turned off during critical stages of flight (takeoff and landing). The company also recommends prohibiting the use of devices that intentionally transmit electromagnetic signals, such as cell phones, during all phases of flight.
Despite this trumpet call to caution, it is still operators and their flight crews that are ultimately responsible for deciding whether to allow the use of portable electronic devices (PEDs).
Arab News contacted a large number of airlines, including Saudia and bmi. Only two, Air Arabia and Emirates, responded to our inquiries about their procedures. They said: “At Air Arabia, we consider the safety of our aircraft and passengers amongst our top priorities and we have certain policies and procedures to follow for any situation we face on board. If any passenger refuses to shut off a mobile phone, we hope to solve the issue by speaking reasonably to them.
“However, should the passenger keep refusing different procedures, such as signing a warning letter and some times diverting the flight, are followed. These procedures are also applied in case of smoking and drinking on board. Mobile usage on board is dangerous because it has an effect on the avionic system of the aircraft, especially during take-off and landing where the risk of interference in the navigation system is higher.”
However, Emirates were much more close-mouthed. One Mr. R. Menon replied on behalf of the airline: “With reference to your message of Jan. 23 to Mr. Badr Abbas, we regret our inability to provide you with the required information, due to our internal corporate restrictions.” Make what you will of that.
Boeing conducted an analysis of operator reports to ascertain the effect of PEDs on aircraft systems. Of the reports involving airplane anomalies, only a few showed a strong correlation between the airplane reaction and the suspected PED. In 1995, Boeing tested a passenger’s laptop after it was reported to have caused autopilot disconnects.
The emissions from the computer exceeded the Boeing emission standard limits for airplane equipment at various frequency ranges up to 300 MHz. Two in-flight tests with the actual PED, using the same airplane and flight conditions, attempted to duplicate the problem. Using even these extensive measures to recreate the reported event, Boeing was unable to confirm the reported interference between the PED and the airplane system. That supports the pilots’ claims of inconsistency.
In 1996/1997, with the 767 airplanes, Boeing received five reports in eight months about interference with various navigation equipment (un-commanded rolls, displays blanking out, flight management computer [FMC]/ autopilot/standby altimeter inoperative and autopilot disconnects) caused by passenger operation of a popular handheld electronic game device.
In one case the flight crew confirmed the interference by turning the unit on and off to observe the correlation. The same unit was used on another flight and on a different airplane, but the event could not be duplicated. Boeing purchased two of the actual suspect units through the airline and tested them in the laboratory, along with three off-the-shelf units. It was determined that these suspect units had emission profiles similar to the off-the-shelf units and that the levels from these devices were below airplane equipment emission limits.
A passenger’s palmtop computer was reported to cause the airplane to initiate a shallow bank turn in a 747 aircraft in 1998. One minute after turning the PED off, the airplane returned to “on course.” When the unit was brought to the flight deck, the flight crew noticed a strong correlation by turning the unit back on and watching the anomaly return, then turning the unit off and watching the anomaly stop. Laboratory tests could not duplicate the effect, even though the PED exceeded Boeing’s PED emission standards for the aircraft.
The bottom line to all this is simply this; the effects of PEDs seem to vary between laboratory and actual flight conditions. Thus we do not really know what is going to be the effect of using one on an aircraft.
The UK Air Accidents Investigation Board investigating the recent 777 crash at Heathrow said that the thrust on the right engine fell and eight seconds later, the thrust on the left engine also fell. Both engines continued to work, but with inadequate power.
“Investigators have also established that the engine control commands worked normally and the aircraft was found to have an adequate fuel supply when it was examined on the ground. The mystery now is why the engines failed to respond despite the automatic throttle appearing to work normally,” The Daily Telegraph Reported. Is this a case of “Hello mom...?” The answer quite disturbingly is that we just do not know.
And if some phone-addicted dimwit wants to phone his mother to ask where she is or tell her he is about to land, then he should be evicted from the aircraft. Personally, I am not too fussy about the altitude.