A/R-14 Fox Attack, Reconnaissance, CAS/COIN Aircraft

Submitted To:

United States Air Force

BY

First In Flight, Inc.

Mississippi State University,

Mississippi State, Mississippi, 39762

2

EXECUTIVE SUMMARY

First in Flight, Inc. is pleased to present its final report for the A/R-14 Fox light close air support and

counter-insurgent aircraft. First in Flight has completed the initial contracted conceptual design including initial

analysis of the requirements, creation of the mission profile, initial weight calculations and sizing, creation of

and calculations for aircraft geometry, cockpit sizing, aerodynamic analysis, cost analysis, performance analysis,

and structure load analysis.

First in Flight followed and used the requirements to calculate important geometry and aerodynamic

properties. The max weight and cruise speed were too low to work with the remaining requirements according

to the team’s calculations, so First in Flight negotiated the properties to a higher value. The team created the

mission profile and functional flow block diagram to set a vision and design goals for the aircraft’s systems from

both a broad and focused viewpoint. The initial requirements established a set of constraints from which the

initial weights and sizing were calculated. These values lead to the aircraft geometry and aerodynamic properties,

which the team then used to do a performance analysis. First in Flight sized the cockpit using anthropometric

data taken in a survey to fit a wide range of pilots, from a 5th percentile female to a 6 foot 4 inch tall male. The

cost analysis provides initial data on how much the A/R-14 project will cost, and shows that the project achieves

the low cost requirement. The team created a V-n diagram showing load limits across the velocity range the A/R-

14 will fly at safely.

The cost results and model for the aircraft are presented below. The A/R-14 project is very affordable,

with 72% of the unit cost of an A-10 Warthog and 0.21% of the project cost of the F-35 project. The A/R-14

uses one engine, has a mid-wing setup, and uses a conventional empennage. The team designed the engine

intakes to be placed behind the cockpit near the leading edge of the wing in order to prevent debris intake on

unimproved airfields. First in Flight has completed the requirements placed to create the A/R-14 Fox.

3

TABLE OF CONTENTS

EXECUTIVE SUMMARY 2

TABLE OF CONTENTS 3

LIST OF FIGURES 4

NOMENCLATURE 5

INTRODUCTION 6

BACKGROUND 6

STATEMENT OF THE PROBLEM 6

APPROACH 7

RESULTS 9

SUMMARY & CONCLUSIONS 31

REFERENCES 35

4

LIST OF FIGURES figure 1. Mission Profile 7

figure 2. Vehicle Arrangement Three-View 8 figure 3. First and Second-Level Functional Flow Block Diagram 8

figure 4. Third-Level Functional Flow Block Diagram 9

figure 5. Weight Regression 9 figure 6. Takeoff Weight Analysis - Nikolai Method 10 figure 7. Constraint Analysis 11

figure 8. Wing Top View 12

figure 9. Horizontal Tail Top View 13

figure 10. Vertical Tail Left View 13

figure 11.Wing and Tail Characteristics 14

figure 12. Top View of Cockpit 15

figure 13. Side View of Cockpit 16

figure 14. Airfoil Selection table criteria 16

figure 15. NACA 6-Series Selected Airfoil 17

figure 16. CPI Normalized against 2012 USD 18

figure 17. CPI Estimation up to 2025 Normalized against 2012 USD 18

figure 18. RDT&E Cost Analysis 19

figure 19. Speed Overview 20

figure 20. Takeoff Lengths 20

figure 21. Max Rate of Climb 20

figure 22. Lift and Drag Variance 21

figure 23. Thrust Required 21 figure 24. Ferry Range and Endurance 22

figure 25. Combat Radius and Endurance 22

figure 26. Cruise Turn Capabilities 23

figure 27. Max Turn Capabilities 23

figure 28. Glide and Decent Capabilities 23

figure 29. Landing Distance over 50 ft Obstacle 23

figure 30. V-n Diagram for Combat load at Sea Level 24

figure 31. Lateral-Directional Time-History Plots ##

figure 32. Longitudinal Time-History Plots ##

figure 33. Stability Derivative Analysis ##

figure 34. Digital SparrowHawk HUD ##

figure 35.Cockpit Armor ##

figure 36. Fly By Wire Flight Control System ##

figure 37. Fuel System ##

figure 38. Bleed Air System ##

figure 39. Advanced Pitot-Static System ##

figure 40. Hydraulics System Schematic ##

5

NOMENCLATURE

AAO = Airborne Armed Overwatch

AOA = Angle of Attack

AR = Aspect Ratio (span2/reference area, applied to wings and tails)

A/R = Attack/Reconnaissance

CL = Wing Lift Coefficient

CAD = Computer-Aided Design

CAS = Close Air Support

CFD = Computational Fluid Dynamics

CG = Center of Gravity (mass)

CHK VLV = Check Valve

COIN = Counter-Insurgent

CPI = Consumer Price Index

DADC = Digital Air Data Computer

DAPCA = Development And Procurement Cost of Aircraft

DATCOM = Data Compendium (USAF aerodynamics methodology report)

EDP = Engine-Driven Pump

EIS = Entry of Service

F = Fighter

FAC = Forward Air Controller

HOTAS = Hands on Throttle and Stick Operations

L/D = Lift-to-Drag Ratio

M = Mach Number

MAC = Mean Aerodynamic Chord

MLG = Main Landing Gear

MTOW = Maximum Take Off Weight

OBIGS = On Board Inert Gas System

OBOGS = On Board Oxygen Gas System

Px = Pressure

RDT&E = Research, Development, Test, & Evaluation

RFP = Request For Proposal

TAT = Total Air Temperature

TSFC = Thrust Specific Fuel Consumption

T/W = Thrust-to-weight ratio

USAF = United States Air Force

USD = United States Dollars

W/S = Wing loading (weight/area)

We = Empty Weight

VL = Vertical Landing

6

1. INTRODUCTION

First in Flight is completing its contracted effort to provide a close air support/counter insurgent

(CAS/COIN) aircraft to the United States Air Force. The airplane will enter service in 2025. First in Flight’s

goal is to provide a fixed wing, low cost, lightweight close air support and counter insurgent aircraft that can

play multiple roles on the battlefield. These roles include but are not limited to: strike capabilities,

reconnaissance, forward air controller, counter insurgent and light strike aircraft. The aircraft that First in Flight

designed is intended to be an armed overwatch for ground troops that are in contact with enemy forces, and is

intended to provide detection, observation, and targeting of enemy forces all while operating from unimproved

runways. The Fairchild Republic A-10 Thunderbolt II is rather costly to maintain and operate. It was designed

to destroy tank columns and armored divisions instead of unarmored cars and lightly armed infantry. The First

in Flight aircraft is designed as a light close air support aircraft, as well as to provide a vantage point from which

to designate hard targets for threat based battle.

2. BACKGROUND

The goal of this study was to design an effective low cost aircraft to be used in combat scenarios where

it would be far more costly to use other aircraft such as Lockheed Martin's F-22 and F-35, or the armored tank

that is the Fairchild Republic A-10. The United States Air Force is asking for a low cost, lightweight close air

support aircraft to support the United States and her allies in low threat environments in any theater around the

world. The A/R-14 will be able to take off from unimproved runways for ease of use in any territory.

The A/R-14 was designed with lightweight close air support in mind, whereas the F-22 is primarily

designed for air superiority combat. The low risk environment that the Air Force will be flying in does not require

the use of stealth technologies that both the F-22 and F-35 make use of. This aircraft will also be able to take on

the role of the A-10 in these low risk environments, where the heavy hitting older brother will not be needed in

the area of operations. All three of these aircraft need to have a paved runway to take off from, but the A/R-14

does not need these well kept runways. It can take off from an unimproved runway or grass field. Although

aircraft of this designation do exist, there are not many that have the requirements given to First in Flight. For

this reason, the design that First in Flight came up with is an important addition to an often underappreciated

family of aircraft.

3. STATEMENT OF THE PROBLEM

The fundamental problem addressed by First in Flight is to design a lightweight close air support and

counter insurgent aircraft that is capable of handling many roles on a modern battlefield. First in Flight designed

the A/R-14 Fox. This aircraft is a fixed-wing, low-cost aircraft whom the U.S. Air Force is seeking. The A/R-14

not only has strike capabilities but it also has a reconnaissance role. This aircraft is able to fulfill the role of

forward air controller (FAC) directing heavier strike aircraft into the region. The objective for this aircraft is to

provide continuous airborne armed overwatch (AAO) presence over and close air support to regular and special

operations ground troops in contact with an enemy force. The A/R-14 can also provide observation, detection,

and targeting imagery of enemy forces and facilities for strikes by other supporting aircraft. The scope of this

design project extended to nearly every aspect of the aircraft. From engine selection to aerodynamics and

performance, the design is thorough. First in Flight created a V-n diagram of the A/R-14’s performance envelope

with a load factor of 7 in mind. Even though thorough, an actual structural design of the aircraft was beyond the

scope of this project. In this project we took the plane from a set of requirements from the Airforce, and turned

those given requirements into an aircraft. The A/R-14 Fox will have an entry of service (EIS) in 2025.

7

4. APPROACH

A. Request for Proposal (RFP) Requirements

The RFP outlines specific characteristics including but not limited to performance, simple design

constraints, anthropomorphic envelopes, avionics, and armaments. The aircraft’s requirements are as follows:

- Gross Weight: no more than 28,500 lb (negotiated from 25,000 lb)

- Max Speed: 460 knots

- Cruise Speed: 350 knots (negotiated from 300)

- Stall Speed (dirty): 95 knots

- Service Ceiling: 40,000 ft

- Combat Radius: 500 nmi

- Combat Endurance: 3.5 hr

- External Load: 6000 lb with 6 hardpoints

- Ferry Range: 1250 nmi

- Crew: 2: Pilot and Combat Systems Officer

- Limit Load: 7g

- Operate from unimproved airfields.

- Carry an electro optical targeting system and advanced communications array.

The team used these constraints to produce the mission profile shown in Fig. 1. This mission profile drove all

aspects of the design, as performance, endurance, and weight would all need to be managed efficiently in order

to accomplish the mission. As with any design, the requirements are not only the constraints, but a major driving

factor that shapes the aircraft from start to finish.

figure 1. Mission Profile

B. Initial Design

At the beginning of the project, First in Flight came together, each with a drawing of what they wanted

the aircraft to look like. This initial design gave the team an end goal to shoot for as well as somewhere to start.

The initial design considered different possibilities that we could chose. For example, First in Flight decided to

use a single jet engine, a tapered mid-wing design, conventional tail, and tricycle landing gear. Although a single

engine was chosen, two inlets were necessary to accomplish the intake area. The design also required the inlets

to be high off the ground as to not take in any debri on takeoff or landing since the capability of using unimproved

8

runways was a requirement. In terms of the wing design, a tapered wing planform was the frontrunner because

it provided a more elliptical lift distribution. The decision to place the wing along the center of the fuselage was

a result of the team’s desire for optimal stability of the aircraft. The initial design team of First in Flight chose a

conventional tail design because it does not disturb the rudder’s effectiveness at high angles of attack. These

decisions, though not set in stone, united the team to work toward a common idea. Fig. 2 shows a general three

view of the aircraft with the chosen physical characteristics applied.

figure 2. Vehicle Arrangement Three View

First in Flight drafted a functional flow block diagram for the A/R-14 so that the team could determine

requirements for the plane’s systems. A first level overview of the plane’s functions leads to a second level

overview detailing the mission operations of the aircraft, which can be seen in Fig. 3. In Fig. 4, a third level

overview looks closer in detail at the requirements necessary for the operations.

figure 3. First and Second-Level Functional Flow Block Diagram

9

figure 4. Third-Level Functional Flow Block Diagram

5. RESULTS

Task 1: Initial Sizing

The sizing group of First in Flight began initial sizing of the aircraft by using a weight regression of

aircraft of similar capability and size. This regression was based on empty weight vs takeoff weight as shown in

Fig. 5. This regression was used to form the iterative solution that was used for determining the empty weight of

the aircraft. First in Flight decided that it was necessary to use the Nikolai Method of the iterative weight

calculation to determine their empty weight due to the fact that this method

figure 5. Weight Regression

included a weight drop during the middle of the mission which fit the team’s mission profile. From this method

and the initial conditions from the RFP, the team began determining the aircraft’s weight fuel fractions. The

weight fractions were based upon the mission profile from Fig. 1 and were used in conjunction with the Nikolai

method and a guessed value for the takeoff weight of the aircraft to determine the empty weight of the aircraft.

A crew weight of 440 lbs total was accounted for as requested in the RFP as well as 8750 lbs of armament that

were dropped during flight. After multiple iterations and negotiating the RFP, the team reached a less than .01%

difference between the guessed takeoff weight and the actual takeoff weight. This miniscule difference meant

10

that the team had correctly predicted the takeoff weight of the plane. A summation of the iterative process is

shown as a graph in Fig. 6.

figure 6. Takeoff Weight Analysis - Nikolai Method

The predicted empty weight and the calculated empty are the two plotted lines and the intersection

represents the correct takeoff weight of 28430 lbs. From the Nikolai method, the team was also able to gather

that the aircraft’s empty weight is 13805 lbs and the total weight of fuel for the mission is about 7750 lbs. After

completing these crucial initial sizing reports, the First in Flight team was able to make additional calculations

that helped form the constraint analysis and all of the aircraft geometry.

Task 2: Constraint Analysis In order to determine a combination of wing loading and the thrust-to-weight ratio needed for the

requested aircraft, the First in Flight crew formed a constraint analysis. This analysis included performance plots

of stall, take off, rate of climb, service ceiling, constant speed turn, and cruise. Each performance characteristic

was plotted based on the wing loading and thrust-to-weight ratio combinations that could fulfill the characteristic.

For stall, a wing loading of 60 was used for all values of thrust-to-weight ratio to establish the upper bound of

the design space. In the process of determining the bounding curve of takeoff performance, the team used an

obstacle clearance height of 50 feet was required for clearing an obstacle at the end of the runway. The takeoff

curve was also a function of the coefficients of drag and lift at liftoff as well as the required takeoff distance. For

the rate of climb curve, the defining equation was a function of climb velocity and vertical speed. This curve

became fairly linear as wing loading increased. The service ceiling curve is defined by the aircraft only gaining

100 ft per minute of altitude. First in Flight used the given jet equations for constant level turn which related the

thrust-to-weight ratio to the minimum drag coefficient and the turning velocity. Cruise performance was based

mostly only the given cruise velocity specified in the RFP with the minimum drag coefficient being an integral

part as well. Fig. 7 shows the constraint plot calculated by First in Flight with the yellow region representing the

acceptable design region for their aircraft.

11

figure 7. Constraint Analysis

As seen in Fig. 7, the region is bounded by four performance curves: stall performance, rate of climb,

takeoff, and cruise performance. For the region defined by these curves, the team was able to choose an aircraft

design wing loading and thrust-to-weight ratio that fit their aircraft and performance needs. One of the optimal

design points is listed in the Fig. as the intersection of the takeoff and stall performance curves. This intersection

called for a wing loading of 60 (PSF) and a thrust-to-weight ratio of 0.4311. This thrust-to-weight ratio fell near

the predicted value and was considered before the team decided to go with a slightly larger value of 0.4787. The

larger ratio was chosen due to the limited engine selection that would fit within the requirements of the RFP.

The proceeded to use the newly determined constraints to form the aircraft geometry and calculate the necessary

aerodynamics.

Task 3: Aircraft Geometry (wings and tails and fuselage layout)

First in Flight began calculating the geometry of the aircraft only after calculating the desired wing

loading and weight of the aircraft. Once these parameters were decided, the team used the wing loading to decide

critical wing sizing features. The first step in their calculations divided weight by wing loading to find the wing

area that fit the criteria. Using the wing loading, span was able to be calculated as well as the root chord and tip

chord of the wing. After determining the main shape of the wing planform, the mean aerodynamic chord (MAC)

could be calculated. First in Flight determined the MAC of the wing to be 9.45 ft and the quarter chord was then

calculated. The team also decided to taper the wings in a fashion that gained a more elliptical lift distribution as

12

well as improved aesthetics. Fig. 8 shows the planform of the wing.

figure 8. Wing Top View (units in feet)

Due to the flight speed required for the A/R-14, the team decided to sweep the wings. In order to calculate the

sweep of the wing, equation 1 was used. The team balanced the need for less transonic drag characteristics and

aesthetics to produce a 10 degree leading edge sweep and a 4.45 degree trailing edge sweep. The transonic regime

applies to the aircraft since Mach .68 is required.

(1)

For all parameters that came from comparing the proposed aircraft to existing aircraft, the team used averaged

values from between jet trainers and jet fighters. The first characteristic that used these calculations was the

aspect ratio (AR). First in Flight calculated the required AR of the wing to be 5.25. This AR allows for good roll

response of the aircraft as well as a limited adverse yaw. Wing incidence for military aircraft is normally 0

degrees and the team decided that this should be the case for the A/R-14 also. The team decided that since the

aircraft was designed as a mid-wing, wing dihedral was not needed. Once the wing geometry was finished, the

team added endplates onto the wing tips because they were the most cost effective option to increase lift and

reduce drag.

From wing geometry, the moved to designing the tail geometry. For simplicity sake, the team decided to use a

conventional design for the empennage. The planform of the horizontal wing is shown in Fig. 9. Using the fighter

characteristics, First in Flight decided the AR and the taper ratio. The rest of the horizontal characteristics were

decided in the same fashion as the wing.

13

figure 9. Horizontal Tail Top View (units in feet)

First in Flight used a conventional layout ratio between the tail geometry and wing geometry. Blanketing

and deep stall were also taken into account by the team and were avoided by positioning the tail accordingly.

The vertical tail was then designed so that during all angles of attack the rudder would still be affected. Fig. 10

shows the vertical tail configuration. Fig. 11 shows a tabulation of all of the wing and tail geometries. Reference

appendix of this document for full 3-view drawing with dimensions.

figure 10. Vertical Tail Left View (units in feet)

14

figure 11. Wing and Tail Characteristics

Task 4: Cockpit Design

First in Flight was asked to design a cockpit based on the given parameters in the proposal. The proposal

called for an aircraft that could support a crew of 2, a primary pilot and combat system officer. There must be

adjustable rudder pedals and adjustable seats. The primary pilot seat must be able to occupy a 6’4” pilot to a

minimum 5’ pilot and 6’ to a minimum 5’ combat officer. In order to do this, the team used data from a study

North Carolina State University conducted. In this study, First in Flight took the dimensions of the 5th percentile

of women and the 99th percentile of men into account. Due to the requirements of the proposal, these ranges fit

the height requirements for the pilot and combat officer. To quantify these findings, the design team made

drawings using a stencil and pencil to precisely sketch the dimensions of the seats, seat adjustments, rudder

deflection, and cockpit dimensions.

As shown in Fig. 12, the total length of the cockpit is 138.2” with a total width of 34”. The pilot and

combat system officer’s seats width are 22.92” with seat-back height of 38”. Due to g-forces and blood flow in

the body during these these steep maneuvers, both seats are angled backwards 30 degrees, or 120 degrees from

horizontal. The height of the canopy from the floor is 46.9”, this leaves 2” from the top of the pilot’s head to the

height of the canopy. The pilot’s seat has an adjustable height deflection of 7” while the combat officer’s seat

has a height deflection of 6” as shown in Fig. 13. For horizontal adjustment, the pilot’s position has a rudder

deflection of 12” total, 6” either side from the neutral position. For safety purposes, the combat officer has rudder

pedals as well with a total deflection of 9.25” with 4.625” on either side of the neutral position.

The basic design of the cockpit was inspired by slide 30 in the Fuselage Layout Presentation 6 [8] from

mycourses. The layout chosen was the tandem seating. For the actual seat, First in Flight chose the Martin Baker

MK-16 Ejection Seat [1] for the aircraft due to its characteristics and use in similar aircraft. The Martin Baker

MK-16 has many attractive traits that the A/R-14 Fox will benefit from. This ejection seat has an operating

ceiling of 50,000 ft which far exceeds the ceiling of this aircraft. The A/R-14 Fox has a cockpit armor thickness

of about 1.5” made of titanium. This armor is called the “Titanium Bathtub” and was first used in the Fairchild

15

Republic A-10 Thunderbolt II. This armor is intended protect the pilots from small arms fire.

figure 12. Top View of Cockpit

figure 13. Side View of Cockpit

16

Task 5: Aerodynamic Analysis

Starting with the rough drawing and looking at similar aircrafts, First In Flight had good approximation

of what the airfoil choices were. we started with three NACA 6-series airfoils that best fitted with the required

design parameters. With the help of airfoil selection table as shown below, NACA 64₃-218 dominated among

others.

figure 14 . Airfoil Selection table criteria

The airfoil that was finally chosen was the NACA 64₃-218 as shown in Fig. 15, which took us a step

further towards our aerodynamic analysis goal. This extensive analysis was done using the presentation provided

to First in Flight by Mr. Walker, Presentation 7: Aerodynamics. This analysis took a great portion of time from

the Aerodynamics group at First in Flight, and was only just recently finished. Afterward we focused on the

efficiency factor for straight wings and swept wings which turns out to be 0.853 for our design aircraft. That lead

us to work on the flaps of the aircraft.

For the flaps of the Fox we, at First in Flight, chose to stick with a simple flap. First in Flight did this

because the stall speed with the flaps down (Vₛ₀) had to be at a velocity of 95 knots. Because this stall speed

could be achieved without using any leading edge devices or complex flap, we chose to keep it simple and use a

plain flap. With the flaps fully extended, 30 degrees, the stall speed, Vₛ₀, was 88 knots. This was below the

requirements so the plain flap will work for the aircraft.

17

figure 15. NACA 6-Series Selected Airfoil

Task 6: Cost-Effectiveness

The First in Flight team estimated the cost for the A/R-14 by using a modified Development And

Procurement Cost of Aircraft (DAPCA) IV Cost Model, using 2012 USD as the currency. The modified DAPCA

IV model is a good estimate of the final cost for the aircraft because it was initially modeled using military

aircraft similar to the First in Flight design. This cost analysis includes development and production costs, and

it adjusts for inflation in 2025. Since the USAF is covering the costs for the development of the A/R-14, a break-

even analysis is not included.

The cost analysis team adjusted for inflation by normalizing the annual average Consumer Price Index4

(CPI) for the years 2000 through 2017 against the 2012 CPI. Fig. 16 shows the results of these calculations. The

linear trendline gives an equation which the cost analysis team uses to estimate the inflation for the years 2017

through 2025. See Fig. 17 for the results of these calculations. The final result is that 1 USD from 2012 is

equivalent to 1.237 USD from 2025. The 2012 wrap rates for engineering, tooling, manufacturing, and quality

control use this ratio to find the rates updated for inflation. The DAPCA model uses these rates among a few

other equations to calculate the research, development, testing, and evaluation (RDT&E) costs, which can be

seen in Fig. 18.

figure 16. CPI Normalized against 2012 USD

18

figure 17. CPI Estimation up to 2025 Normalized against 2012 USD

figure 18. RDT&E Cost Analysis

The USAF called for a low cost project. With a unit cost of $15.5 million and a project cost of $3.1

billion, this project is relatively low cost when compared with other aircraft costs. The unit cost for an A-10, a

comparable aircraft, is about $21.5 million in 2025 USD. The A-10 was initially a low-cost aircraft design, and

the A/R-14 continues that trend with only 72% the unit cost of the A-105. Compared to a more costly program,

such as the $1.5 trillion F-35 program6, the A/R-14 costs much less than the US government spends on other

programs.

Task 7: Performance

First in Flight did all of the performance analysis of the A/R-14 Fox with MATLAB. The performance

analysis team designed scripts that could readily change inputs for common, useful values like maximum lift

19

coefficient and parasite drag. This coding style not only facilitated changes as the aerodynamics team pressed

on, but allowed for changes in the aircraft’s characteristics based on variables unique to each mission such as

combat loading or runway surface condition.

Fig. 19 below shows an overview of the speeds of the aircraft from sea level to service ceiling these

calculations consider an aircraft at maximum takeoff weight (MTOW) with a combat load of 6000 pounds.

Similar performance results and more will be shown in detail in subsequent charts and graphs.

figure 19. Speed Overview

The A/R-14 is required to have the ability to takeoff on unimproved runways. Because unimproved

runways are often short, the aircraft was designed to takeoff and clear a 50 foot obstacle in as little distance as

possible. The chart below, Fig. 20, shows the takeoff and obstacle clearance distances for each flap setting

available to the pilot. The 30 Degree flap setting is not

figure 20. Takeoff Lengths

Although the RFP did not specify a required rate of climb (ROC), the First in Flight performance team

used MATLAB to predict the maximum rate of climb of the aircraft at MTOW to be 6,795 fpm at a velocity of

best climb (Vy) of 235 KIAS shown in Fig. 21 below.

20

figure 21. Max Rate of Climb

Next, the performance team needed to characterize level flight. Fig. 22 and Fig. 23 below show the

coefficient variance and the thrust required curves for the A/R-14 Fox at sea level with maximum fuel and combat

load.

figure 22. Lift and Drag Variance

21

figure 23. Thrust Required

The thrust required graph, colloquially known as the power curve or thrust curve shows the drag for different

airspeeds as well as the thrust required to overcome the drag.

When the plane is not combat loaded, the A/R-14 Fox was designed to be able to ferry 1250 nautical

miles on only internal fuel, but did not have an endurance requirement. Despite this, the MATLAB script should

still contain endurance time calculations. To assess these values, the First in Flight performance team found the

ferry ranges and endurances for three different cruise types based on varied airspeed, altitude, and angle of attack.

In each calculation, one of the aforementioned variables was varied while the other two were held constant. The

range equations below, Eq. (2)-(4), show the method of calculation for variable AOA, variable airspeed, and

variable altitude respectively.

(2)

(3)

(4)

The endurance equations below, Eq. (5)-(6), show the calculation method for endurance when considering a

variable AOA, variable airspeed/variable altitude respectively.

(5)

(6)

The resulting calculations from the equations above are shown in Fig. 24 below.

22

figure 24. Ferry Range and Endurance

The A/R-14 Fox is required to have combat radius and endurance of 500 nm and 3.5 hours with a maximum

combat load. The combat radius is the distance that an airplane can fly and still be able to return home safely

after completing the mission. The results of the analysis are shown in Fig. 25 below.

figure 25. Combat Radius and Endurance

The distances and times related to the range and endurance all exceed the required parameters on the RFP. This

allows for wiggle room in case the design needs to change in the future.

It is also important to calculate the aircraft’s turning abilities. Despite the fact that the RFP did not require

a certain turning radius, turning ability is a great way to judge the performance capabilities of a close air support

aircraft. First in Flight’s analysis of the the level turning capabilities of the A/R-14 Fox consisted of cruise speed

turn calculations for bank angles ranging from 15 to 81 degrees. The significance of the 81 degree limit is that it

is close to the aircraft’s load factor limit of 7. The results are shown below in Fig. 26.

figure 26. Cruise Turn Capabilities

The A/R-14 Fox’s cruise turn capabilities are interesting to note, but its ability to turn in sea level conditions

with and without combat load is notable as well. This is why the First in Flight performance team calculated the

maximum turn rates and velocities in Fig. 27 below.

figure 27. Max Turn Capabilities

23

The next thing that the performance team analyzed was the gliding capabilities of the aircraft. This

consisted of calculation of glide speed, glide range, sink rate, and decent rate. These calculations are shown in

Fig. 28 below.

figure 28. Glide and Decent Capabilities

Finally, the performance team analyzed the landing distance capabilities of the design with the shortest

landing distance in mind. This short field landing is achieved through the use of flaps, gear, and a full combat

load for extra drag. Fig. 29 below shows the landing capabilities for different flap settings.

figure 29. Landing Distance over 50 ft Obstacle

First in Flight is content with this performance analysis. Though it is not a complete analysis, the

performance team provides tangible results for the hard work of all of the other disciplines of aircraft design.

Task 8: Loads and Structures

First in Flight used a limit load of 7 for cruise flight. This is a common limit load value based on modern

fighter aircraft data. The customer requested that the aircraft should be able to withstand a limit load of 7 for

cruise and 5 with a combat load. First in flight developed the analysis using MATLAB and the requirements for

a FAR part 23 aircraft. Though these requirements do not apply directly to a military aircraft, the customer

advised that we develop our envelope based on these requirements.

Fig. 30 below shows the V-n diagram for both cruise and combat loadings at their respective altitudes.

24

figure 30. V-n Diagram for Combat load at Sea Level

Task 9: Flight Dynamics

First in Flight performed a lateral-directional and longitudinal stability analysis of the A/R-14 Fox at

cruise conditions. The analysis looks at perturbations in steady flight and analyzes the stability derivatives. For

the lateral-directional analysis, a positive 10 degree deflection of the ailerons occurs for one second and a

negative 15 degree deflection of the rudder occurs for three seconds. For the longitudinal analysis, a constant

negative 2 degree deflection of the elevators is input after 1 second. The First in Flight team looked at the results

of the analysis, which can be seen in Fig. 31, Fig. 32, and Fig. 33, and calculated the handling qualities for the

aircraft. The A/R-14 Fox is a high maneuverability Class IV aircraft, leading to more restrictive handling

qualities. It meets Class IVB roll requirements with 100 degrees in 1.0 seconds. Phugoid damping handling

qualities are Level 1 across all flight phases. Short period damping handling qualities are Level 1 across all flight

phases. Dutch roll handling qualities are Level 2 across Category A flight phases and Level 1 across Category B

and C flight phases. Spiral mode handling qualities are Level 1 across all flight phases. Roll mode handling

qualities are Level 1 across all flight phases. The A/R-14 Fox is statically stable, although a few stability

derivatives are on the edge of the criteria. It meets all ten static-stability criteria for velocity perturbations: The

forward speed, sidespeed, vertical speed, pitch, sideslip, roll rate, pitch rate, yaw rate, pitching moment and

forward speed, and rolling moment and sideslip criteria are all met. This analysis is based on the aircraft without

the Fly By Wire system’s computer. As such, the computer’s active stability will make handling the aircraft

easier for the pilot. The A/R-14 Fox will provide exceptional handling adequate for its mission in all phases of

25

flight with the use of a Fly By Wire Control System (See Task 12).

figure 31. Lateral-Directional Time-History Plots

figure 32. Longitudinal Time-History Plots

26

figure 33. Stability Derivative Analysis

Task 10: Avionics First in Flight was required to use a glass cockpit for the A/R-14 Fox. A glass cockpit allows for easier

access for controls, and customization of the touch display as opposed to than steam gauges. First in Flight used

the Esterline Electronics Cockpit 4000 NexGen that utilizes all of these controls and displays. The 4000 NexGen

features a Hands on Throttle and Stick Operations (HOTAS) that allows very easy access to controls and options

without having to take the hand off the throttle or stick. The HOTAS system allows the pilot to toggle between

three flight modes on the Head Up Display (HUD) and other displays. These three modes are Navigation, Air-

to-Air, and Air-to-Ground. These modes display useful information to the pilot such as the aircraft’s direction of

flight, the direction its nose is pointing, and even Continuously Computed Impact Lines/Points for air to air and

air to ground applications. For the HUD, First in Flight elected to use the CMA-7150 Low Profile Digital

SparrowHawk. This HUD, shown in Fig. 34 below, has a 26 degree Field of View and is designed for easy

integration in to the existing avionics system.

figure 34. Digital SparrowHawk HUD

27

Task 11: Weights and Balance

The aircraft’s MTOW was set by the RFP. This weight was negotiated to accommodate the capability to

hold more fuel in the airplane and increase its range. The Aircraft’s static margin is about 18%. The airplane’s

center of gravity was calculated through the careful use of a MathCAD sheet. The sheet took into account the

weights of everything from the tail to the fuel in the wing based on empirical equations derived through years of

aircraft design. The center of gravity was adjusted to be in the correct spot by changing the dimensions of the

titanium armor that surrounds the pilots in the cockpit. This armor is shown in Fig. 35 below.

figure 35. Cockpit Armor

After each iteration of resizing the armor, effectively moving the CG, the airplane was ran through a

flight dynamics simulator to verify stability in the chosen configuration. When a stable configuration was

realized, the position and weight of the 519 lb armor plate was finalized.

Task 12: Fly By Wire Flight Control System First in Flight chose to design the A/R-14 Fox as a Fly By Wire Flight Control System (FBW FCS)

aircraft. Since this aircraft will be used in military applications, it was first established that the FCS should be

triply redundant meaning that the system would have two failsafes in the case of failure of the system. Fly By

Wire systems are basically defined by their ability to control an aircraft without the use of traditional physical

cables and pulleys connected to the pilot’s controls. The system works by taking pilot inputs and feeding them

electronically into a centrally located FCS system that reads the inputs and outputs movements to the control

surfaces such as the ailerons, rudder and elevators through the use of a combined electronic and hydraulic system.

28

figure 36. Fly By Wire Flight Control System

The FCS also takes data inputs from the atmosphere conditions as well as the plane movement to

distribute warnings and limitations to both the aircraft and the pilot. Fig. 36 shows a rough schematic of the

FBW-FCS system utilized by the A/R-14 Fox. As shown, the system take inputs from various aircraft sensors as

well as physical inputs by the pilot to guide the aircraft to the pilot’s specified maneuver. In other words, the

FBW-FCS is the electronic middle-man between the pilot and the aircraft control surfaces.

Task 13: Electrical System The electrical system that First in Flight used for inspiration for the A/R-14 came from the T-6A Texan.

Rather than redesign the wheel, the team determined that it was more time and cost effective to implement a

working design. Some of the main points that the team used from this design were the single 24 volt-42 amp-hr

battery, a forward battery bus, and a forward generator bus. A full diagram of the flow through the electrical

system is attached in the appendix of this document. The things that are powered by the to battery buses varied

slightly from the Texan due to the requirement of a combat loadout and radar system for the A/R-14. This

addition was accounted for within the aft generator battery bus for the combat control system and the aft avionics

battery bus for the radar system. Electrical systems for the displays within the cockpit were modeled nearly

directly after the T-6A system due to requirements and standards set by the USAF. An auxiliary 24 volt 5 amp-

hr battery was also utilized for powering most standby instruments and lights. Per the USAF emphasis, the

system is a 270 VDC system.

Task 14: Fuel System

The A/R-14 Fox uses a General Electric F414-GE-400 engine that produces 13,500 lbs of thrust. The

engine uses Jet-A for fuel and has a TSFC of 0.777 pounds of fuel per hour-pound of thrust. For this amount of

thrust, there must be a fuel system that is able to provide the amount of fuel it needs to feed the engine. As shown

below in Fig. 37, First in Flight designed the fuel tanks to be dispersed through the fuselage and the main wings

and will be bladderless. The main wings carry 37.5% of the fuel each while the fuselage carries 25% of the fuel.

29

These tanks will hold 1156.31 gallons, 7747.33 lbs of fuel and will use a single point fueling point.

figure 37. A/R-14 Fuel System

Task 15: Bleed Air System

The A/R-14 Fox is equipped with an Onboard Inert Gas System and an Onboard Oxygen Gas System.

These two systems are necessary because they provide oxygen and inert gasses for the people and systems

onboard the aircraft. They work by scrubbing and separating the air of oxygen and sending this gas through an

air conditioner and then to the pilot’s mask and cockpit for breathing at high altitude. The inert leftover gas after

separation (mostly nitrogen) is sent various places like the fuel tanks to pressurize them. The OBIGGS gas is

also sent to the wings and leading edge of the cowling for anti-icing purposes. The entire bleed air system is

shown in Fig. 38 below.

30

figure 38. A/R-14 Bleed Air System

Task 18: Digital Air Data Computer and Advanced Pitot-Static System

The A/R-14 Fox has a digital air data computer (DADC) which takes information from a primary pitot-

static system and a redundant pitot-static system. The information is processed and sent to the pilot’s and combat

officer’s instruments. The data is also sent to other systems throughout the plane such as the transponder, flight

computers, and autopilot as seen in Fig. 39. Data is taken in from a pitot probe, a static pressure port, an auto

transformer, an angle of attack (AOA) probe, and a total air temperature (TAT) probe. This data is sent to the

DADC, which processes the information and makes calculations for data, such as mach speed, altitude, etc. This

31

data is then sent to the instruments and flight computers for use.

figure 39. Advanced Pitot-Static System

Task 17: Hydraulic System

The A/R-14 Fox uses a single-reservoir hydraulic system to control the landing gear, wheel brakes, and

air brakes. There is an accumulator that can be used for landing gear extension in the event of a hydraulic system

failure. The system utilizes MIL-H-83282 fluid at 3000 psi in the hydraulic system. The First in Flight team

chose this hydraulic fluid for its fire-resistant properties and widespread usage in the military. A system

schematic can be seen in Fig. 39. The reservoir is pressurized by the bleed air system. It flows through the engine-

driven pump (EDP) and then passes through a check valve (CHK VLV) and pressure (Px) filter to ensure there

is no backflow and the system is clean. The hydraulic system can control the landing gear, gear doors, and

speedbrake via switches in the cockpit. The nose wheel steering and main landing gear (MLG) brakes are

controlled by the rudder pedals. After use in the system, hydraulic fluid will travel back to the reservoir via a

return line, which has another check valve and pressure filter. An emergency accumulator powers a separate line

to drop the landing gear and gear doors in an emergency. Pressure is initially supplied by the main system. The

transfer station in between both lines has a check valve so that in a situation where the main system loses pressure,

the emergency line does not lose pressure and can be used. A separate lever is used to drop the gear in the case

32

of an emergency.

figure 40. A/R-14 Bleed Air System

Task 18: FADEC

The Engine control system chosen for the A/R-14 was the Full Authority Digital Engine Control

(FADEC). The FADEC is a system consisting of a digital computer called an Engine Control Unit (ECU). This

coupled with its related components control all aspects of the aircraft’s engine performance. The A/R-14 is a

combat aircraft, and will be in hostile combat zones for an extended period of time as an air support platform

and spotting aircraft. The FADEC system allows the pilot to focus on flying the aircraft and scanning the horizon

and ground for potential threats and it allows the weapons systems officer(WSO) to focus on tracking hostile

targets for engagement or relaying that information, such as size, location, and elevation to friendly ground

elements or other strike aircraft in the area of operation. There are several other advantages to using this system.

The FADEC allows for better fuel efficiency and better integration with engine and aircraft systems. It also

provides semi automatic engine starting, this is useful for getting the Fox in the air faster and that means it can

start the mission which would save the lives of our service members, and it saves weight on the aircraft for more

fuel or munitions. This system also allows for the monitoring of the engine health, and since this aircraft will be

seeing combat scenarios, that allows for maintenance to be performed more quickly. This would let the crews

take on missions frequently and effectively.

6. SUMMARY & CONCLUSIONS

First in Flight, Inc. has completed its contracted effort for the A/R-14 Fox. This includes the completion

of the aircraft weights, airfoil selection, armament selection, and many more subsystems that make up the

aircraft. The team was given a list of requirements from the airforce requesting a Close Air Support (CAS) and

Counter Insurgency (COIN) aircraft that could be used as a Forward Observer and designate targets for other

aircraft in the Area of Operations (AO). The Air Force has a problem in the war on terror. The aircraft they are

currently using are costly to use, and they request a smaller aircraft that can do the job required as effectively as

33

the other aircraft, but at a lower operating cost. The first hurdle First in Flight faced as a team was the initial

sizing phase. Then the constraint analysis lead First in Flight, Inc to the design point picked to best suit the

requirements submitted. The wing geometry was the next task. This is what produced the wing shapes and sizes

seen in the geometry section above. After these were done, the team made decisions on the cockpit and airfoil,

and the sizings were used to find an engine that would give our aircraft the thrust needed to obtain the speed

listed in the requirements. The performance analysis could only be completed once the other sections gave their

information to the performance group, so that the information could be used in the calculation software. First in

Flight, Inc.’s A/R-14 Fox is a perfect fit to this missing niche of a low-cost CAS/COIN and light reconnaissance

aircraft with 0.21% the program cost of the F-35 program and 72% the unit cost of an A-10 Warthog.

The A/R-14 Fox flight dynamics were also determined which revealed that the handling qualities were

level one except for category A Dutch Roll. First in Flight Inc. is also proud to report that the aircraft meets Class

IV B Roll requirements and has been established as a statically stable aircraft. The avionics portion of the aircraft

design led First in Flight Inc. to select a Low Profile Digital SparrowHawk HUD and a glass cockpit to meet

mission requirements. In determining the weight and balance of the aircraft, the center of gravity was calculated

to be located at 29.9% of the mean aerodynamic chord of the wing. The center of gravity was shifted by adding

or subtracting weight to the armored cockpit. Following this calculation it was also discovered that the static

margin was about 18%. Next the FBW FCS was chosen to satisfy both the design criteria and mission

requirements. This system was triply redundant to ensure operation even in the case of failure as this is both safe

and required for USAF aircraft. The electrical system was then mapped throughout the aircraft from the main

battery to each individual display and subsystem. Once this was completed, the same was done for the fuel

system and bleed air system. The final system to be mapped was the hydraulic system which was designed based

on the T-6A Texan just like the electrical system. The final portion discussed in this write up was the FADEC

system. This system was designed in similar fashion to most modern USAF fighter aircraft and was chosen

because it provides control over the engine in an efficient way. In conclusion, this aircraft was designed to be a

modern hybrid of the A-10 warthog and A-29 Super Tucano with a generalized direction of being consistent

with modern USAF attack aircraft.

34

APPENDICES

35

36

REFERENCES

1“Mk16 Ejection Seat for T-38,” Martin-BakerAvailable: http://martin-baker.com/products/mk16-

ejection-seat-for-t-38/.

2Gordon, Claire C. et. al 1988 Anthropometric Survey of U.S. Personnel: Summary Statistics Interim

Report. March 1989.

3“GAU-22/A 25mm Gatling Gun,” General Dynamics Ordnance and Tactical SystemsAvailable:

https://www.gd-ots.com/armaments/aircraft-guns-gun-systems/gau22a/.

4“Consumer Price Index (CPI) Databases,” U.S. Bureau of Labor StatisticsAvailable:

https://www.bls.gov/cpi/data.htm.

5Bogaisky, J., “Lockheed Lowers Price Of F-35 Under $90M In New Contract,” ForbesAvailable:

https://www.forbes.com/sites/jeremybogaisky/2018/09/28/cost-of-f-35-drops-under-90-million-

in-new-contract/#1a7383d183bd.

6“A-10 Thunderbolt II,” U.S. Air ForceAvailable: https://www.af.mil/About-Us/Fact-

Sheets/Display/Article/104490/a-10-thunderbolt-ii/.

7Walker, C., “ASE 4513 Aircraft Design: 10 Performance,” 2018.

8Walker, C., “ASE 4513 Aircraft Design: 4 Wing- Tail Selection,” 2018.

9Walker, C., “ASE 4513 Aircraft Design: 6 Fuselage Layout,” 2018.

10Walker, C., “ASE 4513 Aircraft Design: 7 Aerodynamics,” 2018.