Sir - Capt Mark Zucal (Letters, Flight International, 18-24 June) is quite wrong to rail against rules which forbid the use of a compact-disc (CD) player in passenger aircraft. I can assure him that the rules are not nearly tough enough.
The problem is that some portable electronic devices are without doubt serious electro-magnetic emitters, and there is no way of knowing which ones are acceptable. Even the lowly CD player is based on devices which, are near relatives of microprocessors, and have clocks. It only requires a manufacturer to decide that it wants a higher clock-frequency, and that CD player can suddenly become a serious hazard. The only safe solution is to ban them all.
The problem is not associated with "glass cockpits", but with radio receivers, such as VOR, VHF communications, etc.
These receivers are becoming more critical to flight safety, and it only requires a passenger with a piece of entertainment equipment to mess them up, either by denying the flightcrew their use, or, worse, by causing misleading readouts.
The problem is compounded by the increased availability of portable devices which are potential interferers.
Hickling Norfolk, UK.
Source: Flight International