STOL HWB

The project focused on a fictional aircraft concept for mass cargo transportation capable of operating on unprepared short runways. The first concept was a combination of a traditionally mounted high wing and a tube-like fuselage with extensions on the side to mount the engines and brace the wing. 

It is soon discovered that the required wingspan for the payload is too large if we're to keep the wing loading in a reasonable range. The tube-shaped fuselage is also not suitable for groups of non-stackable objects. The fuselage is flattened to increase the projection area along the z-axis, and the cargo hold's floor area.

Initially, flying at high transonic speed was one of the main goals, and the airframe was modified to reduce wave drag. Dummy cargoes are placed into the cargo bay to size the fuselage.

The coordinates are exported and converted for aerodynamic optimization using Aeolus. The software iteratively changes the selected parameters within the specified range to optimize for the selected characteristic. 

The model on OpenVSP is updated following the modifications made by  Aeolus. The new geometry is used to rearrange the space available. Sections for passengers and the cargo area are defined based on their dimensions and position requirements.

CATIA is the tool used for detailed modeling. Geometries are exported from VSP in step format and are used as a reference for the reconstruction in CATIA. Most of the features, such as engine intake, boundary layer diverter, and cargo ramp, are planned out.

The cockpit arrangement is also planned using CATIA. The unfavorable large frontal area of this aircraft became an advantage when a large cockpit was needed. The flight deck is large enough to hold up to 6 crews to work together if ever required.

The main landing gear kinematics are designed in spar time. The number of tires was easily determined using the weight of the aircraft and the distributed weight per tire of the aircraft (C-17) having a similar mission. A large number of tires is mainly a result of the need for low tire pressure for unprepared runway short take-off and landing operations. The complexity of the main landing gears is higher than expected due to the number of large-diameter tires and the restricted space caused by the cargo bay floor.

To counteract the moment generated by the blown flaps, the Vee stabilizer generates a large amount of trim drag; the large trimming force needed due to the short tail length has also eroded the extra lift generated by the powered high-lift device. Thus, the canard configuration became a possible solution to this problem. The downwash from the canards was expected, and the chord length distribution was modified. The new concept was to operate the aircraft at high alpha till the ground effect cushions the vehicle for a soft landing. In the process, the canard downwash was expected to compensate for some loss of pressure at the intake. 

A simplified model is tested in the ERAU wind tunnel lab, with the help of Zebulon, Nathan, and the class TA. More information is listed in Aerodynamic Forces and Flow Visualization on an Experimental Canard Delta Wing.

Zebulon joined the project after this update.

Several engines with comparable thrust were selected for the new concept. Because of the mix-flow nozzle and the pressure needed, only the engines with a moderate bypass ratio (around 5) were considered. The pressure distribution at the inlet station is also the main concern at this point; this will likely result in engine failure at the most critical phase of flight.

An airfoil with a converted lower surface near the leading edge was modified from a NASA SC(2) foil. This feature reduces the moment coefficient of the centerbody, but the concentrated high-pressure region lowers the lift-to-drag ratio. More study is needed to determine whether the reduced trim drag (pressure) is worth the increased drag. 

The flow visualization experiment indicates that the effectiveness of vertical stabilizers at their recurring location is not ideal, and the increase in the angle of attack worsens the situation. The stabilizers were removed to reduce drag, and the increase in sweep angle and winglets' size was an attempt to restore the needed directional stability.

After analyzing the canard volume of aircraft with varying missions, a new concept has been developed with smaller canards. This is also an improvement because the violent movement of cargo in the transition of high and low alpha is dangerous, and the new concept would only use the canards for attitude control, unlike the close-coupled canards in the previous iteration.

This project is currently paused because of the high course load. But more testings are planned for future development, and portable equipment and tools were designed to obtain more data from each test cycle.