From J. L. EDMONSON
I really must put to rest the concerns of Simon Gardner and Peter Conners
(Letters, 8 February and 7 March) regarding the problem of electromagnetic
radiation affecting aircraft electronic and electrical systems.
This is a design problem of which the avionics and aerospace industries
are fully aware, and treat with the respect and thoroughness accorded to
all other aspects which might affect flight safety. I can assure your readers
that the spurious outputs from CD players, laptops, electronic games and
so on, and the intentional radiation from cell phones, are many orders of
magnitude down on the test levels to which aircraft equipment and the complete
aircraft itself are subjected.
Certification currently requires that civil aircraft continue to fly
safely in field strengths up to 820 V/m (mean) and 8300 V/m (peak). Meanwhile,
emissions from personal equipment that can be plugged into the mains (which
includes laptops, and which most respectable manufacturers extend to apply
to CD players) are restricted by international standards to a few tens of
mu V/m when measured at 1m range, and it is hard to envisage an uncontrolled
electronic toy generating more than a few hundred mu V/m. Even the cell
phone would be pushed to deliver a couple of volts per metre.
I am certain the real reason for the CD ban has more to do with the
possibility of disturbing a fellow passenger’s comfort, either as the induction
of audio frequency into the earphone cables of the next seat (unlikely)
or as direct airborne sibilance, although it beats me why tape cassette
players aren’t banned.
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J. L. Edmonson Yeovil, Somerset
