Sir - I take issue with the statement in the article "Sparks ßy over TWA 800" (Flight International, 16-22 July, P12) that "-the FAA has so far failed to adopt fuel safety recommendations issued by the NTSB [US National Transportation Safety Board]". The article also states that "-the NTSB still does not know why the centre fuel tank exploded". The US Federal Aviation Administration has not failed. It has decided, for good reasons, not to do certain things.
Under the heading "Collision conclusion" (News in Brief, Flight International, 23-29 July, P6) I read that "-the mid-air collision near Delhi, India-happened because-[the Il-76 freighter] was 1,000ft lower than its cleared altitude".
This is not really so. It happened because we have an air-traffic-control system wherein, on occasion, two aircraft using extremely accurate navigation equipment on reciprocal tracks rely on one, or sometimes both, aircraft to level off at their assigned altitudes to avoid catastrophe. This is hardly a 10-6 risk, but more in the category of "pushing one's luck".
Regardless of what the authorities might authorise, you will find an increasing number of aircraft crews tracking a mile (1.6km) to the right of centreline.
Capt F W Pike
President
Australian and International Pilots Association
Woollahra, New South Wales
Australia
Sir - After reading "Sparks fly over TWA 800", I had a look through the European Joint Aviation Requirements. There seem to be no specific requirements to cover the installation of electrical equipment and wiring inside fuel tanks.
There is a requirement, however (JAR25.981), which covers fuel-tank temperature. Section G of this requirement states that the temperature inside the fuel tank must not be increased by "any probable operating failure or malfunction" of any component.
"Probable" is a vague word, as it leaves room for discussion as to whether a chafed wire, or a short circuit, is "probable" or not.
Thus, there appears not be a specific requirement to eliminate "all ignition sources", as stated in the article.
P Gambardella
Farnborough, Hampshire, UK
Source: Flight International
