The DBF 2024 ADT Plane:

EmergenSC

Mission Breakdown:

Ground Mission:

GM tests the ability of the aircraft to change mission configurations quickly. The aircraft begins stowed in the parking spot with all payloads in a triage area. Once time starts, the aircraft is transitioned to M2 flight configuration with Crew, EMTs, and a Patient on gurney, and MSC installed. Once demonstrated successfully the team member replaces the M2 payloads with those for M3, or the maximum number of Passengers declared in Tech Inspection. Finally, the time resumes, and the team member returns the aircraft to parking configuration with Crew and Passengers removed.

Mission 1:

Fly three laps with no payload. One point is awarded if successful.

Mission 2:

Simulates the urgent transport of a Patient with two EMTs and a Medical Supply Cabinet (MSC).

Mission 3:

The payload for M3 is Passengers, with the number of Passengers carried decided by the team. The score depends on the number of laps flown in five minutes and the battery capacity.

Configuration:

Aircraft Configuration: Monoplane
- Offered the best flight characteristics, GM handling, and manufacturability.

Wing Location: High Wing
- Provided flexibility in payload and parking spot designs, with added benefit in flight handling and manufacturing.

Tail Configuration: Converntional
- Ease of manufacturability and decreased weight for TOFL.

Propulsion: Dual Motor
- The use of counter rotating propellers negated propeller torque and increase dynamic pressure over the wing flaps for a higher lift coefficient during takeoff.

Payload: Rail and Neck Hold
- Decreases complexity and incrases relebility verses competing designs. In an event of change to the target payload number, this rail will adapt to these changes easily rather than redetermining the structure to hold another hatch.

Landing Gear: Tricycle
- Maximize effective TOFL due to the smaller wheelbase. Additionally, a tricycle gear keeps the fuselage parallel to the ground, which makes payload operations easier given the rail system selection.

Parking Configuration:
- Entire wing could be manually stored in one movement with minimal mechanical linkages and no compromise to the spar

Manufacturing

The preliminary design aimed to converge on an aircraft optimized for cabinet mass and number of Passengers. Several trade studies were conducted across disciplines using simulations and models to size each major component. Methods and outcomes of this design phase are outlined below.

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Wing ribs were laser-cut from plywood and balsa, depending on the required strength. They were then epoxied to a carbon fiber reinforced polymer (CFRP) tube, aligned with a jig to set the twist angle and spanwise location.

Winglets, ailerons, and flaps were cut from polystyrene foam, reinforced with a fiberglass and epoxy composite, vacuum-bagged, and cured in a mylar-film casing. The winglets were epoxied to the polylactic acid (PLA) winglet adapters.

Wing aft spars were laser-cut from plywood and attached to the ribs with CA glue. The slotted flap vein plate was laser-cut from 1/16-in balsa, steamed, pressed to shape, and dried. 1/8-in square stringers were set in pre-cut recesses in the ribs, providing surfaces for the Solarfilm Lite (Solite) aft skin to adhere to the wing assembly. Foam female molds for the carbon-fiber leading edge were cut using a hotwire tool and prepared with a layer of mylar for a smooth surface. The leading-edge skins were manufactured by wet layups, cut to size with holes for the motor mount, and epoxied to the ribs.

A CFRP layup was selected for the motor mounts since composite fabric is ideal for the loading cases of
the motor and can be streamlined to improve aerodynamics. The tube was manufactured using a wet layup
on a 3D-printed PLA mandrel. One ply of 6.10 oz/yd2 (207 g/m2) twill weave carbon fiber was wrapped twice
around the mandrel, which was destructively removed with pliers after curing. The front and aft plates,
which connect the motor, CFRP tube, and wing, were laser-cut from plywood and epoxied to the tube.

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A balsa built-up structure was selected for the empennage to minimize weight. The tail structural components, including 1/8-in balsa ribs, 1/4-in balsa spars, 1/16-in plywood rib reinforcements, and 1/32-in balsa skin, were manufactured and assembled in a similar process as outlined in Section 6.2.1. The balsa leading edge was steamed, molded to shape, and allowed to dry. The balsa skins were then adhered to the rib structure with CA glue. The complete skin was covered with Solite to create a smooth finish.

A built-up structure with balsa and plywood components was selected for the fuselage. It was constructed around a plywood , to hold the formers during assembly. Structural formers were preassembled with reinforcements and hardpoints. The formers were epoxied together with four spruce- balsa longerons, which were steam-bent to shape before attachment to reduce fracture and stresses within the adhesives. Payload, parking, wiring, and Crew system components were placed, and the truss structure was added once free access to the aircraft interior was no longer required. The tail boom was placed and adhered to the aft three formers. Balsa shapers with stringer cutouts were then adhered to the core structure to create the desired fuselage geometry. Lastly, stringers were added, and the entire structure was covered in Solite film. The Crew and Passenger hatches were assembled separately and hinged last.

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The main bow gear was manufactured using 26 plies of unidirectional fiberglass (FG) in a wet layup. Slow-curing epoxy resin wasapplied after each layer, then sealed in a vacuum
bag under pressure for 12 hours.
Holes were drilled through both bow gear tips to fit an axle to hold a wheel. The wheels and axles were secured in place using collars and set screws.

The FG gear was integrated into the aircraft via a hardpoint beneath the fuselage and sandwiched between 1/4-in plywood. The mechanism was fixed by nylon bolts designed to shear off during a landing over 2.5g to protect the fuselage from horizontal loads.

The nose gear was manufactured with a diameter steel wire. It was attached to the fuselage at a 25° forward angle to match the bow gear height during 1g loading to facilitate payload un/loading. The nose gear was attached to the fuselage on a plywood hardpoint with two mounting saddle straps. A wheel with a foam tire was attached to the strut with collar.

The payload rail was constructed out of 3D-printed polylactic acid (PLA) sections and a sized plywood support as shown in Fig. 35 in Section 5.3.6.1. Testing demonstrated that the friction coefficients between the aluminum insert and PLA were lower compared to alternative materials. The 3D-printed PLA section and the PLA contact areas were cut into sections due to usable volume limitations in the CR-10 3D printer. To support the structural load, the plywood supports were made from a sandwich structure of laser-cut 1/4-in, 1/8-in, 1/16-in panels, and a thin layer of PLA contact area.

Testing

PROPULSION TESTING

Propulsion testing consisted of validating battery performance and theoretical thrust. Battery capacity and energy were examined using the West Mountain Radio Battery Tester. The tester applies a variable load to maintain a constant current and monitors the voltage battery. Static thrust testing was also conducted directly on the V2 aircraft using a fish scale rated for 25 lbf (111.21 N) of thrust. Redundancy in testing methods allowed for data validation and improvement opportunities to both
setups

LANDING GEAR TESTING

o verify the LG could withstand the energy upon
impact, drop testing was performed at maximum weight. The gear was raised to a height of 8.0 in (20.3cm) to simulate a 4.91 ft/s (1.50 m/s) sink rate with a factor of safety (FoS) of 1.5, as pictured in Fig. 56. The gear showed no signs of failure.

Load tests of the main gear were performed to ensure the gear could withstand the maximum expected loads with an FoS of 1.5 and compare actual to predicted deflections. The gear
met the necessary loading requirements.

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FUSELAGE DROP TESTING

After the LG strength and design were validated, the LG was mounted to Version 2 (V2) of the aircraft to confirm that the fuselage could absorb residual energy as designed. This test was also performed at maximum weight and a height of 8.0 in (20.3 cm) to simulate the maximum sink rate with a 1.5 FoS.