PRELIMINARY DESIGN

Preliminary Design Phase

The phase of aircraft design that follows the conceptual design phase and employs calculation procedures to determine parameters that will influence the entire detail design phase.

Aircraft Maximum Take-Off Weight (MTOW or WTO)

The maximum weight at which an aircraft is allowed to take off, determined during the preliminary design phase and broken down into payload weight, crew weight, fuel weight, and empty weight.

Wing Reference Area (SW or Sref or S)

The area of the wing used as a reference for calculating various aerodynamic parameters, determined during the preliminary design phase.

Engine Thrust (TE or T) or Engine Power (PE or P)

The force or power generated by the aircraft's engine, determined during the preliminary design phase.

Initial Sizing

The process of determining the size of fundamental features of the aircraft, such as wing area and engine thrust or power, during the preliminary design phase.

Maximum Take-Off Weight Estimation

The technique used to obtain the first estimate of the MTOW for an aircraft before it is designed and built, based on past history and data from similar aircraft configurations and missions.

All-Up Weight

The maximum allowable weight of the aircraft during take-off operation, also known as the maximum design take-off weight.

Weight Build-up

The process of breaking down the aircraft weight into different components, including payload weight, crew weight, fuel weight, and empty weight.

Payload Weight (WPL)

The weight of passengers, loads, luggage, and cargo carried by the aircraft.

Crew Weight (WC)

The weight of the pilots and crew members on board the aircraft.

Payload Weight

is the net carrying capacity of an aircraft. An aircraft is originally required and designed to carry the payload or useful load. includes luggage, cargo, passenger, baggage, store, military equipments, and other intended loads.

190 lbs

weight of an average adult during summer

195 lbs

weight of an average adult during winter

200 lbs

weight of an average adult male during summer

205 lbs

weight of an average adult male during winter

179 lbs

weight of an average adult female during summer

184 lbs

weight of an average adult female during winter

82 lbs

weight of a Child weight (2 years to less than 13 years of age) during summer

87 lbs

weight of a Child weight (2 years to less than 13 years of age) during winter

70 lbs

weight of the luggage (two bags) in an international flight

50 lbs

weight of the luggage (one bag) in a domestic flight

Crew Weight

the weight of the people who are responsible for conducting the flight operations and serving passengers and payload

Aircraft maximum takeoff weight (MTOW), wing reference area, and engine thrust or engine power

Three fundamental aircraft parameters determined during the preliminary design phase

Engine thrust is calculated during the preliminary design phase

If a jet engine is selected during conceptual design phase…..

Engine Power is calculated during preliminary design phase

If a propeller - driven engine is selected during conceptual design phase…..

Estimate aircraft MTOW

and Determine wing area and engine thrust simultaneously

Preliminary design phase is performed in two steps:

1. Maximum speed

2. Range

3. Endurance

4. Rate of climb

5. Take-off run

6. Stall speed

7. Maneuverability

8. Load

9. Passenger

10. Cargo

10 aircraft performance design requirements

Determine Aircraft maximum take-off weight (MTOW)

This technique’s results are not accurate. It's just an estimation

Determine wing area and engine thrust/ power

This technique's results are very accurate and reliable

20% inaccuracies

How many inaccuracies will be the result of mtow?

Boeing, Airbus, Lockheed, Grumman, Cessna, Raytheon, Bombardier, Dassult, Emberaer, Learjet, and Jetstream

Aircraft manufacturering companies

Passengers, loads, luggage, and cargo

Payload is consist of…

Federal Aviation Administration

Meaning of FAA

Maximum design take-off weight

Also referred to as the all-up weight

1. Payload Weight

2. Crew Weight

3. Fuel weight

4. Empty weight

MTOW is broken down into four elements…

Wpass = 180 lbs

Suggested value for passenger weight based on published data.

180 lbs

Male flight crew members

140 lbs

Female flight crew members

180 lbs

Male flight attendants

130 lbs

Female flight attendants

140 lbs

Flight attendants not identified by gender

Specific Fuel Consumption

SFC

Transport, fighter, and reconnaissance

Three typical mission profiles/ aircraft

Dash

The main feature of a fight of a fighter aircraft that makes up the longest segment of the flight

range

In terms of flight mechanics, the cruising flight is measured by…

endurance

In terms of flight mechanics, the loitering flight is measured by…

radius of action

In terms of flight mechanics, the dash is measured by…

20%

FAA regulations requires a transport aircraft to carry how many percent of fuel that needed on a flight of 45 minutes to observe airworthiness standards.

5%

The extra fuel required for safety purposes is almost ____ of the aircraft total weight

1. take-off

2. climb

3. cruise

4. loiter

5. descent

6. landing

what are the six flight segments or phases

The Breguet Range Equation

The fuel weight fraction for the cruise segment is determined by employing the….

Range

it is the total distance that an aircraft can fly with a full fuel tank and without refueling

1. constant- altitude, constant lift coefficient flight

2. constant- airspeed, constant lift coefficient flight

3. constant- altitude, constant airspeed flight

Three flight programs that satisfy trim requirements:

Jet engine is generating thrust while prop-driven engine is generating power

Difference between jet engine and prop-driven engine

Endurance

The aircraft performance criterion loiter is measured with a parameter called the…

Endurance (E)

is the length of time that an aircraft can remain airborne for a given expenditure of fuel and for a specified set of flight conditions.

Loiter

This is a flight condition where the endurance is its primary objective.

lb/h lb and N/h N

unit of C

Vemax

Speed for maximum endurance

Vpmin

Minimum power speed

20-40%

The minimum power speed for most prop driven aircraft is about…

it is a technical figure of merit for an engine that indicates how efficiently the engine is burning fuel and converting it to thrust.

JP-8

the most commonly used fuel for US air force jet aircraft

JP-5

It is denser, less volatile fuel than JP-8, which allows it to be safely stored in the skin tanks of ships.

Jet A and Jet A-1

most common commercial aircraft fuel is…

wing reference area and engine thrust or engine power

two major outputs in the preliminary design

1. stall speed

2. maximum speed

3. maximum rate of climb

4. take-off run

5. ceiling

6. turn requirements

6 aircraft performance requirements

range and endurance

following aircraft requirements have been used to determine aircraft mtow

Wing Loading

The ratio between aircraft weight and wing area is referred to as wing loading and represented by W /S . This parameter indicates how much load (i.e., weight) is held by each unit area of the wing.

Thrust to weight ratio

The ratio between aircraft engine thrust and aircraft weight is referred to as thrust loading and is represented by T/W . This parameter indicates how heavy the aircraft is with respect to engine thrust

Power Loading

The ratio between aircraft weight and engine power is referred to as power loading and is represented by W /P. This parameter indicates how heavy the aircraft is with respect to engine power.

Tmax

maximum engine thrust

Dmax

maximum aircraft drag

Talt

engine thrust at altitude

Tsl

engine thrust at sea level

Cdo

zero lift drag coefficient

Cdi

induced drag coefficient

K

induced drag factor

e

Oswald span efficiency factor)

AR

wing aspect ratio

Pmax

maximum available engine power

Cd

drag coefficient

CL

lift coefficient