The effect of fuel type (liquefied natural gas vs. kerosene) on the optimum cruise altitude for a single-aisle, medium-range transport aircraft is investigated. An automated aircraft synthesis program including a detailed mission analysis module was used to assess the impact of liquefied natural gas (LNG) on fuel burn and equivalent CO2 emissions. Verification studies for four different reference aircraft showed that the mission analysis module was able to predict the fuel weight for various missions with an error between -1.5% and +5.9%. A baseline, kerosene-fuelled, mid-range, single-aisle aircraft was designed which was estimated to have an optimum cruise altitude for minimum fuel burn of 11,400m (37,500ft). It also showed the altitude for minimum equivalent CO2 emissions to be at 12,500m (41,000ft). Changing to LNG, the aircraft showed a maximum reduction in CO2-equivalent emissions of 21% at a cruise altitude of 10,400m (34,100ft). At altitudes above 9,000 meters, the higher H2O emissions rapidly increased the equivalent CO2 emissions. It was therefore concluded that, to a much larger degree than for kerosene-fuelled aircraft, cruise altitude is an important design parameter for LNG-fuelled aircraft if equivalent CO2 emissions are to be minimized.@en

Pulsed jet actuators (PJAs) are one of the candidate technologies to be integrated in Fowler flaps to increase the maximum lift coefficient of transport aircraft in the landing configuration. The total system consists of the actuators plus sensors, a piping system to supply pressurized air and a (redundant) power and communication system to provide actuator control. In this paper, it is investigated what increase in the maximum lift coefficient is required to justify the added weight and power off-takes that accompany the integration of pulsed jet actuators. This is done by making an automated design process for the overall aircraft, the piping assembly system, and the electrical wiring interconnection system. These last two sub-systems rely on KBE techniques that automate dimensioning and performance evaluation. A test case is specified that encompasses the design of a typical single-aisle mid-range aircraft with and without the PJA system installed. It is concluded that the introduction of the PJA system requires at least an increase in maximum lift coefficient of 0.2 to justify the increase in system mass and power off-takes. Furthermore, it is shown that if the maximum lift coefficient increases with 0.4, only small reductions in maximum take-off weight (−0.3 %) and operating empty weight (−0.6 %) can be expected, while the total fuel burn remains virtually constant.@en