Conceptual Design

The conceptual design phase was done to assess the rules of competition and give a design configuration that is feasible, the team took inspiration from real life planes and decided the design based on mission requirements. The resulting configuration is a conventional airplane with tricycle landing gear, a high wing with a single engine. This configuration would give optimum results within specifications.

3.1 Mission Requirement

DBFC 12 comprises of 3 types of missions performances, design report submission and conduction of viva on the competition date. The scoring weightage for Design report, De-Briefing and Viva Voce are 25%, 30% and 45% respectively.

3.1.1 General Mission Requirement.

The aircraft cannot be of rotary wing or lighter than air.

No structure/components may be dropped from the aircraft during flight.

No form of externally assisted take-off is allowed. All energy for take-off must come from the on-board propulsion battery pack(s).

Must be propeller driven and electric powered with an unmodified over-the-counter model electric motor. May use multiple motors and/or propellers.

May be direct drive or with gear or belt reduction.

Motors may be any commercial brush or brushless electric motor. Aircraft must use commercially produced propeller/blades

Teams can change the propeller diameter/pitch for each flight attempt.

Motors and batteries will be limited in current draw by means of a 40 Amp fuse in the line from the positive battery terminal to the motor controller.

Must use over the counter NiCad or NiMH batteries. Maximum propulsion battery pack weight 1.7lb.

Missions has to be completed as: Mission 1; Mission 2.

During each mission 3 laps must be completed after takeoff.

One lap means that the aircraft must complete a 360 degree turn. Lap 1 = 360 left 2. Lap 2 = 360 right 3. Lap 3 = 360 vertical

3.2 Mission Requirement into Design Requirement

These mission requirements will limit our design so the plane was designed with the following features relating to the stated mission.

Mission 1

No Payload.

Aircraft is to be light weight to quickly complete all laps in least possible time.

Mission 2

500ml water bottle payload.

Fuselage structure should be strengthened to bear payload. The design must have high lift capability

3.3 Solutions, Configurations and Results

3.3.1 Motor Configuration

Single motor pull type propulsion system was selected for our design since it was very simple to design and fabricate with no complexities. It also makes it easy to adjust the C.G of the plane and hence makes it simple to adjust other aircraft components accordingly.

3.3.2 Wing Configurations with respect to Position

There are generally three types of wing configuration:

• High Wing
• Mid Wing
• Low Wing

Required tasks were reason why team opted for high wing configuration. High wing configuration is more stable, gives more lift, and makes it easy to remove and place payload. It also gives better ground clearance. Mid wing and low wing configurations although providing greater flight maneuverability, had payload ground clearance and stability issues.

3.3.3 Wing Configuration with respect to Number

Bi-plane configuration even though provided more stability and lift, wasn’t selected because it creates problems with case fit and is complex and costly to design. Monoplane design is least complex and easier to manufacture was chosen with detachable wings to increase case fitting and repair ability. Delta wing and Canard wing is not suitable since they were heavier and create case fit problems and provided manufacturing challenges.

3.3.4 Fuselage Configuration

Single boom design was selected since it is lighter in weight, it generates least amount of drag force. Twin boom provides more internal payload space but generates more drag which it was not worth. The wing shaped-fuselage required thicker inner camber and therefore was difficult to design and fabricate. Hence by method of elimination single boom design proved to be the best option. Fuselage was designed for horizontal internal payloads so as to keep its width small.

3.3.5 Tail configuration

The Conventional configuration is structurally more stable since the elevator is directly attached to the solid fuselage. It provides decent yaw and pitch control characteristics and hence was selected for our plane tail. The T-tail design even though increases the effectiveness of the vertical tail, but it poses structural issues. Same is the case with the Cruciform tail configuration. The U-tail gives best yaw and pitch control characteristics, but it requires more complex control linkages hence increased cost of the manufacturing.

3.3.6 Landing Gear

Tricycle gear aircraft have the advantages or making the plane more difficult to 'nose over' while landing, reduce possibility of ground loop and makes it easier to control on ground in case of heavy winds. The tail dragger configuration has the possibility of making the plane “nose over” when hitting a bump. Therefore tri-cycle configuration was chosen in our design.

3.4 Final Conceptual System Selection

So far, it was decided that the aircraft design must be having the following characteristics:

i. High wing mono plane configuration

ii. Single boom fuselage

iii. Conventional tail

iv. Tri-cycle landing gears

v. Detachable wings to load payload.