Relevant certification rules
Concorde has proven to be safe. But since Concorde certification some new rules were introduced by the authorities e g FAA, JAA. which a new SCT has to meet. The most obvious challenge is cabin pressure loss.
It is required that aircraft and passengers can survive pressure loss in the cabin provoked by a sudden hole like a broken window. Therefore, sufficient pressure levels must be maintained in the aircraft when a hole opens After DC 10 accidents, when a burst of underfloor cargo doors destroyed the floor of the aircraft with the hydraulic systems, size of this hole was increased by pure geometrical definition (about door size); for a wide body aircraft it has а яze of 20 sqft (FAR 25). This poses extreme difficulties for flight altitudes above 40000 ft. It is impossible to fight against this requirement by building a stronger aircraft, because there is no requirement on strength or probability of creation of such a hole, but only a given hole size Concorde needs only to survive a hole in the hull of window size; and Concorde has small windows.
• Concorde produces unacceptable noise at takc-ofT and landing, although having only 110 passengers. A new SCT. which will be of at least double the size of Concorde, has to meet current noise standards (FAR 36. stage 3) or even more stringent ones. For comparison: FAR 36. stage 3 is just met by the B747-200 But SCT engines will not have a bypass ratio of about 5 like the В747-200 engines . but only one of about 2.
• Best aerodynamic performance L/D (lift/drag) is reached at elevated values of the lift coefficient (about Cl=0.5 for subsonic aircraft, below CL=0.15 for supersonic flight). To fly at good aerodynamic performance, to maintain acceptable pressure levels in the inlets and engines, and to fill the engines with air, dynamic pressure at supersonic cruise will be in the range of about 20 to 30 kPa. Therefore, flight altitude depends on cruise speed and weight, for a Mach 2 aircraft about 16 km And the higher the cruise altitude, the more sensitive is the atmosphere to pollution, especially the ozone layer. At the time being it seems that a Mach 2-SCT will not harm the ozonclayer; but this is based on calculations which arc still questionable. Supersonic aircraft will burn more fuel per passenger kilometer than subsonic transports. Although C02 is not altitude sensitise, it is a well known greenhouse gas. and the large amount of COi emitted has to be justified. In the future it has to he expected that the public will become even more sensitive to environmental impacts. Therefore a new SCT has to demonstrate, that its impact on the earth’s atmosphere is tolerable.
• A body cruising at supersonic speed generates a sonic boom which follows the body. This boom is an annoying and startling noise in an area of about 20 to 40 km at both sides of the SCTs track. To avoid harassment or damage, civil supersonic flight will only be permitted over sea or perhaps uninhabited land. Because noise of the natural environment is so high on the sea. there is no harassment or damage known to people, animals or ships below Concorde routes In contrast to people on land, there exists no complaint about Concorde’s sonic boom over sea .
• Any new aircraft must be able to follow сштепі and future AIC (air traffic control) procedures. In lire future, steeper descent angles may be requested in the airport area, which could be a challenge for SCT.
• New SCT must meet current ground load values, i. e. w heel number, size, loading and distribution. High ground load values may damage some airports, especially on aprons with tunnels.
• Loads on passenger and crew during operation must stay within acceptable boundaries Especially long clastic fuselages provide strong vibrations during ground roll and in turbulence. and may impose high g-loads during rotation.