From
http://www.caa.co.uk/docs/33/srg_gad_gasil2002_03.pdf
So near, and yet . . .
From a report by the BEA (the French AAIB)
The pilot of a Mooney M20J was approaching his destination. The weather had been good for the majority of the flight, but he was aware that it deteriorated considerably towards the destination and had informed his planned alternate aerodrome, which he had passed on his route, that he expected to have to turn back and land there. However the forecast was for the situation to improve.
The visibility below cloud deteriorated, and was described by witnesses as “very poor”. It seems the pilot had selected the first stage of flap, possibly to improve his forward view and increase his manoeuvrability at low speed. The aircraft disappeared from radar view and the wreckage was found in the side of a barn on the top of a hill 2 and a half kilometres from the aerodrome, which was situated in the valley beyond.
The investigation is not yet complete, but the initial report has found several factors which they believe are pertinent to the accident. The pilot was using GPS for navigation, and they believe that the precision of the GPS information gave him an excess of confidence in his ability to find the aerodrome in the conditions. The cloud layer through which the aircraft was flying was broken, and probably allowed him to catch sight of the ground from time to time. He also knew the aerodrome and the surrounding area well, having flown the route many times before.
There were other factors. The temperature of the cloud was below freezing, and icing could be expected. Finally, at the moment of impact the pilot was talking on his mobile phone to a colleague on the ground at his destination, having requested an update on the weather.
And from
http://www.caa.co.uk/docs/33/FOD200119.PDF:-
LEAFLET NO. 29 GUIDANCE CONCERNING THE USE OF PORTABLE ELECTRONIC DEVICES ON BOARD AIRCRAFT
1 PURPOSE AND SCOPE
To safeguard operations, JAR-OPS 1.110 requires an operator “..... to take all reasonable measures to ensure that no person does use, on board an aeroplane, a portable electronic device that can adversely affect the performance of the aeroplane’s systems and equipment”.
Recognising the need to avoid differences between airlines in the manner in which portable electronic device (PED) usage is controlled, this leaflet provides information to assist understanding of the issues, and it establishes common operational policy consistent with the requirements of JAR OPS 1.110.
Although the primary target audience of this leaflet is the airline community, operators of business aircraft, and operators of light aeroplanes and rotorcraft need to be alert to the risks from PED interference. These operators are recommended to adopt equivalent precautions as promoted in this leaflet.
The certification of systems and equipment is outside the scope of this leaflet. Hence it does not apply to approved equipment permanently installed in the aircraft for the purposes of passenger entertainment, or to installed telephone systems approved as satisfying airworthiness standards and licensed for air-ground radio telephone. These systems and equipment will need to satisfy applicable certification requirements and related operating restrictions. Similarly, the leaflet does not apply to permitted medical equipment which meets applicable requirements.
2 DISCUSSION OF THE ISSUES
2.1 General
The use of portable electronic devices (PEDs) on board aircraft by flight crew, cabin crew and passengers presents a source of uncontrolled electro-magnetic radiation with the risk of adverse interference effects to aircraft systems. Given that a civil aircraft flying at high altitude and high speed in busy airspace is in an obviously hazardous environment, and given that many of the onboard systems are safety devices intended to reduce the risks of that environment to tolerable levels, then anything that degrades the effectiveness of those systems will increase the exposure of the aircraft to the hazards.
Consequently, the aircraft operator needs to take measures that will reduce the risks to acceptable limits. PEDs fall into two main categories; non-intentional transmitters and intentional transmitters. The first category includes, but is not limited to, computing equipment, cameras, radio receivers, audio and video reproducers, electronic games and toys, together with portable, non-transmitting devices intended to assist flight and cabin crews in their duties. Intentional transmitters are transmitting devices such as remote control equipment (which may include some toys), two-way radios, cellphones and satellite phones. In periods between transmissions, an intentional transmitter may radiate interference as a nonintentional transmitter.
2.2 Non-intentional transmitting PEDs
PEDs that are non-intentional transmitters will radiate emissions from internal oscillators and processor clocks, some types of motor, and power supply converters. The radio frequencies involved may fall in the bands used for aeronautical radio services, and emission levels may be sufficient to affect aircraft radio receivers through their antennas. Use of a PED on the flight deck presents a particular risk to those navigation systems having antenna systems located in the radome.
JAA Administrative & Guidance Material
2.3 Intentional transmitting PEDS
PEDs that are intentional transmitters may induce interference directly into aircraft equipment, wiring or components with sufficient power to adversely affect the proper functioning of aircraft systems. Many aircraft have non-metallic floors and internal doors that present no barrier to prevent the transmission from penetrating to the avionics equipment bays and to the flight deck. Tests (reference 8.6) have shown that demonstrated susceptibility levels of aircraft equipment, particularly equipment qualified to earlier standards, can easily be exceeded.
2.3.1 Cellphones
The rapid growth in cellphone1 usage has presented the most significant risk to aircraft safety from PED interference. Cellphones are both non-intentional and intentional transmitting PEDs, operating on spot channel frequencies in the bands of approximately 415 MHz, 900 MHz or 1800 MHz. (Some regions of the world use slightly different bands). Most use digital modulation but analogue types are still in use. Their maximum transmitted power is in the range of typically 1 to 5 watts. The actual power transmitted at a particular time is controlled by the cellular network and may vary from 20mW to maximum rated power of the cellphone depending on quality of the link between the cellphone and the network. Even in standby mode, a cellphone transmits periodically to register and re-register with the cellular network and to maintain contact with a base station.
The transmitted power and precise radio frequency of an operating cellphone is dependent on the traffic on the network, the distance of the cellphone from the nearest base station, and any obstacles or attenuation in the signal path. An aircraft on the ground at an airport is likely to be in close proximity to a base station resulting in a strong link between that station and an onboard cellphone. Under these circumstances, the cellphone would seek a free channel in the assigned communication band and its output power would be set by the network to a low level sufficient to maintain the link. Interference levels would, as a result, be low and probably harmless but this cannot be guaranteed. Closing of the aircraft doors increases attenuation in the signal path, and as the aircraft increases its distance from the base station, the output power setting of the cellphone is increased, eventually to its maximum rating. The risk of interference is then at its greatest. At altitude, the cellphone will transmit periodically attempting to register with the cellular network. The quality of the link is likely to be poor and the cellphone will radiate maximum power in these circumstances. Furthermore, since it is likely to be in line-of-sight range of multiple base stations, some degradation of the network operation may result2 and actual communication may not be possible.
The effect of this type of functioning is that, when the aircraft is on the ground near a base station, the interference risk can be low but not negligible, and it will increase as the aircraft taxies and then climbs away from the network base stations. The simultaneous use in an aircraft of several cellphones will result in transmissions at different radio frequencies leading to a more complex interference environment.