ALL OF A SUDDEN, the discussion is about small jets. Not just the 100-seater which China and Korea, or China and Singapore, want to build with European help. Not just the rival 100-seater, for which Boeing and Bombardier may link up with Japan. Not just the 100-seater which IPTN wants to make in Indonesia. Small jet airliners in this case means jet airliners with as few as 30 seats. It's a concept which many are discussing, but to which few are committing - and not without reason.

By general consensus through most of the past three decades, jet airliners had more than 70 seats and turboprops fewer than 70. Canadair, and then Embraer, have successfully challenged the first assumption with their 50-seat CRJ and EMB-145 respectively, but, so far - notwithstanding Yakovlev's non-open-market Yak-40 and the commercially disastrous VFW-614 - nobody has successfully floated a sub-50-seat jet-powered airliner.

The arguments against have been overwhelming. Jet airliners are expensive to build and operate; on short sectors, their extra speed contributes little or nothing to savings in block times; their high-speed wings are inherently less suited to short fields; their pilots want greater pay than their turboprop cousins.

Overwhelming as they may seem, many of those arguments are, individually, suspect. Much of the expense in building a jet airliner derives from its intended use - flying further and higher than a turboprop means that it is generally heavier per seat, and weight means cost. A purpose-built short-haul, medium altitude, jet airliner could be a lot cheaper, especially if it had a simple turbofan engine (which should be cheaper to make than its turboprop equivalent, because it does not need the usual reduction gearbox and variable-pitch propeller of the turboprop). The days of jet pilots earning far more than their turboprop equivalents are passing, and technical advances mean that even a cheap wing should have a better speed range than did earlier ones.

More crucially, however, a simple, lightweight jet built to the ambitions of the regional carriers, rather than those of the majors, could conceivably be just as economical to operate as a turboprop. This is certainly the ambition of Embraer with its EMB-145 - and, if that is just as economical as a turboprop, there is no relevance to the argument over relative speeds about short sectors.

So far, so good - but where does our cheap and cheerful small jet fit into the greater equation? Even though it may be faster than a turboprop, it will be little easier to insert into the "proper" jet market than existing turboprops, unless it can be made to be compatible with the big jets - either by being as fast as them, or by being agile enough to slot in between.

The former is unlikely, so the small jet could end up simply being a slightly quicker, inherently quieter, turboprop-substitute. If that is the case, the airlines will expect it to be delivered at turboprop-substitute prices, not traditional jet-aircraft prices. That in turn means somebody has to tool up for genuine high-rate, low-cost production of both engine and airframe. That leaves the opportunity to build such an aircraft in the hands of those who can make a business case for investing in advanced, automated manufacturing techniques, or those who have efficient production in genuinely low-wage economies.

However it is finally made, a low-cost jet will involve high-cost investment, much higher than has been traditional in the turboprop business, but with no promise of a rate of return greater than that of traditional turboprops. That has been enough in the past to turn giants like Boeing away from turboprops, and to push Daimler-Benz Aerospace towards the disposal of its Dornier business.

In short, to build a 30-seat regional jet would require its maker to create a genuine revolution in production technology and costs, and that the market guarantees to accept huge numbers of the result. Is anybody brave enough to do it?

Source: Flight International