Letters 12 April 2005

Can humans manage better?
Your analysis (Flight International, 5-11 April) of the UK Air Accident Investigation Board's (AAIB) description of the Airbus A340-600's fuel management on the Virgin fuel diversion of 8 February raises fundamental certification issues in the realm of the UK Civil Aviation Authority/Joint Aviation Authorities, and basic "shopkeeping" duties in the realm of Virgin.
In the former, if the subordinate slave fuel control monitoring computer cannot override an incapacitated master, the effectiveness of fail safe operation is eliminated. That is why commercial jet aircraft are crewed rather than piloted. In the latter, surely when faced with the loss of an engine after noticing it was out of fuel, it should almost be a reflex action to pull up the fuel synoptic on the electronic centralised aircraft monitor (ECAM), with the expectation of another loss? More human-centric than techno-centric certification should be at the centre of approving a system of which a human operator is an integral part. Consider the "archaic" Boeing 747-400 at the same point of tank to engine operation on the same flight sector.
With 13,000kgs (28,630lb) per tank, an engine indicating crew alerting system (EICAS) /ECAM message "fuel tank/ENG" appears, prompting the pilot not flying to push off the override/jettison pumps for tanks 2 and 3 and push 1 and 4 crossfeed valves off, thus isolating for symmetrical fuel feed. Failure of EICAS messaging would prompt some pushing/pressing questions before running out of fuel. Keeping the crew involved in such an integral part of LROPS, mitigates against software errors translating into hardware errors. While the automation lunatics have not yet taken over the asylum, it is surely unwise at this stage to confer upon them the keys to the pharmacy?

David Connolly Brussels, Belgium

From Genie to GEnx
A lifetime ago de Havilland considered expanding its licensing of General Electric engines to include the T64 turboshaft/prop. The name Genie was adopted, but the programme failed to materialise due to a lack of new airframe projects and the predominance of the Rolls-Royce Dart, which at that time was well established.
The reason the licence was considered was because the design of the T64 matched its own proposed project in terms of pressure ratios and compressor and turbine stage numbers. Looking at the GEnx design layout and noting Mike Wilking's comments (Flight International, 22-28 March), the same cannot be said for this engine.
Blade numbers have always been a bone of contention, and the temptation to reduce them is attractive. However, the problem with reduced numbers of blades is that individual blades will be of wider chord and heavier, therefore the "blade-off" test will establish the need for a strengthened structure to retain the blade, with the associated weight increase. Again, a seven-stage low-pressure turbine will provide a high turbine efficiency and contribute towards a lower specific fuel consumption and possibly improved emission, but the trend towards "low parts count" is lost and a size and weight penalty must be incurred. With regard to certification, it is difficult to imagine how much read-across there can be from the 53,000lbs thrust (235kN) version and the 72,000lb engine, a 40% increase. 

D F Newland Stanmore, Middlesex, UK

Should this be allowed?
You report that Lufthansa proposes to acquire Swiss (Flight International, 29 March–4 April). Competition authorities scuppered KLM's acquisition by British Airways. Air France on the other hand was allowed to go ahead and buy KLM. Following this, the European Union's competition authorities are unlikely to hinder Lufthansa's takeover of Swiss. But they should analyse the proposed transaction with great care.
Apart from Lufthansa the dominant national network carriers of Austria, Scandinavia and Poland are grouped in the Star Alliance. This means network carrier duopoly between Germany and these neighbouring countries. Now potentially Switzerland would be added to this region of stunted competition. Zurich, as Austrian's chief executive acknowledges, is a competitive hub to Munich and Vienna. The EU's competition authorities should recognise that present day competition isn't just between individual airlines, but increasingly is also between alliances. They should insist denial of Swiss's accession into the Star Alliance as a condition for allowing the proposed deal.

Jouko Vallikari Helsinki, Finland

Stick to the frequency
When listening to an airband radio recently, I was amazed to hear pilots failing to follow simple air traffic control instructions. Three aircraft all within an hour were told before departure: "Do not change frequency until advised." So why when called had the pilots already switched? These thoughtless actions are dangerous. ATC is obviously aware of the problem, so why is more not done to prevent them?

Allan Huse Heston, UK