SYSTEMS REQUIREMENTS REVIEW
GREG FREEMAN ANDY GRIMES NICK GURTWOSKI MOTOHIDE HO VICKI HUFF POORVI KALARIA ROMAN MAIRE TARA PALMER SANJEEV RAMAIAH JACK YANG
AAE 451 FEBRUARY 12, 2009
1 . TABLE OF CONTENTS
Executive Summary (Page 4)
I. MISSION STATEMENT (Page 5)
i. Major assumptions
II. MARKET/CUSTOMERS (Page 6)
i. Customers’ Needs and Benefits
ii. Primary Customer
iii. Market Size III. COMPETITORS (Page 8)
i. Market Competition
IV. CONCEPT OF OPERATIONS (Page 9)
i. Representative city-pairs
ii. Cost Predictions
iii. Meeting Customer Needs
iv. Payload/Passenger Capacity
v. Cabin Layout
vi. Design Mission Profile
vii. Economic Mission Profile V. SYSTEM DESIGN REQUIREMENTS (Page 20)
i. Customer Attributes
ii. Quantifiable Characteristics
iii. House of Quality
iv. Target and threshold values
v. Benchmarking
vi. Technologies/advanced concepts
2 . VI. INITIAL SIZING (Page 25)
i. Estimates for L/D
ii. Empty weight fraction predictor VII. CONCLUSION (Page 31)
i. Summary
ii. Next Steps
VIII. REFERENCES (Page 32)
3 . EXECUTIVE SUMMARY
As aviation advances, the desire for an economic, affordable Supersonic Transport (SST) has increased rapidly. Since the Concorde, there have been no operable Supersonic Transports in the world. OceanAire intends to design the world’s next SST, called Sky, which will solve the technical challenges that have impeded the development of supersonic airliners for decades. As stated by NASA Aeronautics Research Mission Directorate’s 2008-2009 University Competition, the technical challenges include supersonic cruise efficiency, low sonic boom, and high-lift for take-off and landing. Other design specifications decided upon were high cruise speed, long distance cruise, and reasonable passenger capacity, along with providing a luxurious flight.
Sky will target first and business class customers as well as travelers who have the means and desire to reach their destination in a shorter amount of time. The demand for business class aircraft is growing and will increase dramatically by 2020. Sky intends to meet that demand and capture the expanding market. Daily overseas flights will connect major business cities around the world, allowing businesses and airlines to save both time and money.
OceanAire proposes a Supersonic Transport to meet and exceed the requirements set forth by NASA, Lockheed and the future market. Through research on past and present concepts, and ideas
recommended by Dan Raymer [15] , tools have been used to begin setting goals and benchmarks that Sky will adhere to. Sky has taken customer attributes into consideration and will meet specific requirements catering to those attributes. These specifications have led to initial estimates for a design that will reasonably meet the aforementioned goals.
4 . I. MISSION STATEMENT
The two main mission objectives are to design an aircraft with supersonic capabilities that is able to link major city pairs, and to compete with other existing aircraft on the market. Building on the first mission statement, it is very imperative that the designed aircraft will be supersonic, flying at speeds of approximately Mach 1.6- 1.8. The aircraft is being designed as a supersonic airliner and will be used for civilian purposes, enabling transport of passengers and cargo between city pairs across the world. There are already quite a few aircraft concepts in the market catering to this aspect. Hence, the second mission statement is to design an efficient aircraft that can compete with the existing ones in the market and still remain profitable.
Major Assumptions
A few assumptions were made about supersonic flight while developing the mission statement. It was assumed that this aircraft will be designed and manufactured to have its first flight sometime in 2020 and to enter service by 2023. This assumption will give ample time to designers to investigate and incorporate new and effective technologies into design, and hence, come up with a competent and competitive aircraft. It was also assumed that the current regulations on flying supersonic over U.S. mainland would not change. The U.S. government presently prohibits supersonic flight over land. Since it is assumed that this will not change, risks will be reduced by designing an aircraft to fly supersonic only overseas.
5 . II. MARKET/CUSTOMERS
Customer Needs and Benefits
OceanAire’s Sky will hold 49 passengers in a luxurious and comfortable cabin. This aircraft will reduce travel times of subsonic transports by around half due to its supersonic cruise capabilities. Sky will operate internationally and will offer transpacific and transatlantic flights to passengers. Overall, Sky will fly more passengers farther and faster than any other subsonic and supersonic airliner.
Primary Customer
Specifically, this aircraft is designed to serve business travelers who wish to significantly decrease their travel time. Even though business travelers are the primary customer, the aircraft is also available to any traveler who has the desire and means to reach their destination faster. Due to Sky’s designed range capability of 5000 nmi, passengers will be able to not only fly faster but farther. The customer will be able to enjoy a luxurious flight with all the amenities available on current flights with the additional benefits of a faster trip time and more cabin space. Furthermore, OceanAire will offer even more benefits for its business and first-class passengers. OceanAire realizes that connectivity is a priority in this fast-paced business environment and will provide passengers access to the Internet and corporate internets, voice over Internet protocol (VOIP), e-mail, virtual private networks, fax services and video conferencing through Rockwell Collin’s eXchange service [6] . Furthermore, live satellite-television will provide up-to-date news, sports and weather.
Market Size
Sky will offer business and first-class seats with the majority being business-class. Richard Branson, the president and founder of Virgin Atlantic is quoted saying, “There clearly is a demand for a niche for an all-business-class offering.” Henry H. Harteveldt, a senior analyst at Forrester Research states that his research shows that 50 percent of business travelers are willing to pay an above-average price for a noticeably better quality travel time, and that only about a third describe themselves as loyal to a specific airline. Furthermore, as stated in the New York Times in July 2007, Eos, MAXjet, Silverjet, and l’Avion reported in 2007 that each filled 70% or more of their seats flying only transatlantic all business- class flights. Eos and MAXjet began flying in late 2005 and offer 48 and around 100 seats, respectively. Silverjet and l’Avion began flying in 2007 and offer 100 and 90 seats, respectively. As a result, an average
of 59 seats were filled on these four airplanes in 2007 [13] .
The Travel Insider stated in an Airline Review dated October 2006 that business class is the airlines’
largest source of income [19] . In 2008, the senior vice president for worldwide sales at United Airlines, Graham Atkinson, said that the 10 percent or so current passengers who fly in international business class on U.S. carriers generate about 35 percent of airline revenue [3] . The number of passengers that pay for business class and first class tickets range. The number also depends on the route and airline. The Travel Insider in 2006 reported that the number of first class passengers that pay for their ticket might be as low as 10% while other airlines estimate around 20%. Regardless, it can be shown from the statements made above that the business class remains the most profitable income for the airlines.
Over the past 20 years, air travel has grown each year. This occurred despite two major world recessions, terrorist acts, the Asian financial crisis of 1997, the SARS outbreak in 2003 and two Gulf wars. As stated by Boeing, the average growth in airline passenger numbers between 2008-2027 will be
6 . around 4.0 percent each year [4] . According to Airbus, air traffic will double in the next fifteen years [7] . As stated in Embraer’s Market Analysis realesed in 2008, Asia Pacific world air travel demand will grow by 5% each year while North America and Europe will increase by 4% per year. This new growth in airline travel will result in new airplane deliveries. The following graph produced by a Boeing market forecast shows that a much larger demand will be made for single-aisle airplanes than any other type of aircraft (around 65% of the total new deliveries made between 2008 and 2027). As a result of Sky being a single- aisle aircraft, the demand will be maximized.
Figure 1: Boeing Market Outlook’s New Airplane Deliveries for 2008-2027 [4]
7 . III. COMPETITORS
Market Competition
Sky’s first flight will be assumed to be in the year 2020 with full entry into service in 2023. Currently there are no supersonic aircraft in the market, but it can be assumed that this will not be the case in 2020. The following 4 aircraft will be assumed to be competing with Sky in the market of supersonic aircraft: Aerion Corporation’s Supersonic Business Jet (SBJ), Lockheed Martin’s Quiet Supersonic Transport (QSST), Dassault Aviation’s High Speed Aircraft (HISAC), and Sukhoi’s S-21. The following table displays some general specifications of Sky compared to its competition.
Table 1: Market Analysis
The highlighted green boxes in Table 1 indicate where the strengths in each category of the market lie. For instance, the largest cruise speed is Mach 1.8, which is offered by three supersonic aircraft: Lockheed Martin’s QSST, the HISAC and OceanAire’s Sky (hence, three green boxes). Another strength in the market is the capability of the aircraft to fly supersonically overland. Aerion’s SBJ, Lockheed Martin’s QSST and Dassault Aviation’s HISA are all designed to fly overland (no information was found for Sukhoi’s S-21). This is Sky’s only weakness in the market. However, OceanAire’s Sky holds the most strengths in the supersonic market. Sky will be able to hold at least 37 more passengers than its competition. Furthermore, Sky has the largest range capability with 5000 nmi and the largest cruise speed at Mach 1.8. Per FAR36, supersonic overland flight in the United States as well as over 50 other countries has been prohibited. Each of Sky’s competition relies on this regulation being redefined or on using new technological advances to mitigate the sonic boom level. However, OceanAire will not rely on FAR36 being redefined. As a result, OceanAire will operate in city pairs that will eliminate supersonic flight overland. Despite not flying overland, Sky will be designed to be as eco-friendly as possible.
8 . IV. CONCEPT OF OPERATIONS
Representative City Pairs
Sky will fly to a total of 17 global locations with a total of 19 city pairs. In order to operate more profitably, Sky will fly transpacific and transatlantic. Specifically, there will be a total of 11 transpacific
city pairs and 8 transatlantic city pairs. The tables below display the chosen city pairs [18] .
Airport Code Airport Code Distanc e (nmi) LA to Tokyo LAX NRT 4737 SF to Tokyo SFO NRT 4462 SF to Seoul SFO ICN 4927 Seattle to Tokyo SEA NRT 4144 Seattle to Seoul SEA ICN 4533 Tokyo to Singapore NRT SYD >4211 Tokyo to Sydney NRT SIN 2889 Shanghai to Singapore SHA SIN 2038 Hong Kong to Singapore HKG SIN 1387 Hong Kong to Tokyo HKG NRT 1587 Bombay to Dubai BOM DXB 1040 Table 2: Transpacific City Pairs
Airport Code Airport Code Distance (nmi) NYC to London JFK LHR 2999 NYC to Paris JFK CDG 3158 NYC to Amsterdam JFK AMS 3166 Boston to London BOS LHR 2837 Boston to Paris BOS CDG 2997 Boston to Amsterdam BOS AMS 3004 Miami to London MIA LHR 3845 Miami to Paris MIA CDG 3987 Table 3: Transatlantic City Pairs
The distances shown in the tables above indicate the current flight distances between each city pair. The greatest distance Sky will fly will be from San Francisco to Seoul, and the shortest route will be between Tokyo and Sydney. The distances shown for the transatlantic city pairs might be a little less than Sky’s actual flight distance in order to avoid flying supersonically over Novia Scotia, Newfoundland, and the United Kingdom.
The longest runway lengths for each of the 17 global airports were researched in order to ensure that Sky would be able to land at each destination. For instance, Taipei was initially a chosen destination. However, the longest runway length was less than 4000 ft. A takeoff and landing length of less than 4000 ft was believed to be too optimistic for a design specification. As a result, Sky will not fly to Taipei. The following table shows the runway lengths for the 17 airports Sky will be operating at.
9 . Airport Runway Length (ft) Tokyo (NRT) 13123 LA (LAX) 12091 SF (SFO) 11870 Seattle (SEA) 11900 Sydney (SYD) 13000 Singapore (SIN) 13200 Seoul (ICN) 12300 NYC (JFK) 14572 London (LHR) 12802 Paris (CDG) 11811 Amsterdam (AMS) 12467 Boston (BOS) 10081 Miami (MIA) 13000 Hong Kong (HKG) 12467 Bombay (BOM) 11302 Dubai (DXB) 14780 Shanghai (SHA) 10500 Table 4: Runway Lengths for Airport Destinations
A 2008 market analysis was performed for the chosen city pairs. The number of flights per week between each city pair was researched. This number was determined by finding how many non-stop flights operated between each city pair seven days a week. The following graph shows the estimated number of flights per week between the fifteen chosen city pairs.
10 . Flights Per Week in 2008 for City Pair 90 80 70 60 50 40 30 20 10
Flights/Week 0
City Pair
Figure 2: Flights/Week for Chosen City Pairs in 2008
As can be seen from the graph above, the top three flown city pairs are Los Angeles and Tokyo, Tokyo and Sydney, and New York City and Paris . A plot was created in order to show how many passengers fly between each city pair each week. The number of pass engers per week was estimated by assuming that every seat on each flight between the city pairs (see Figure 2) is filled. The figure below shows the estimated number of passeng ers each week that fly to the 19 chosen city pairs on non -stop flights.
11 . Number of Passengers Per Week in 2008 Flying to City Pairs 35000
30000
25000
20000
15000
10000
5000
0 Passengers/Week
City Pair
Figure 3: Passengers/Week Flying to Chosen City Pairs in 2008
Figure 3 shows that more passengers fly between Los Angeles and Tokyo, Tokyo and Sydney, and San Francisco to Tokyo. It can also be noted that the transpacific pairs will be the most profitable for OceanAire. Specifically, OceanAire should target the East Asian market. From the market analysis performed for the year 2008, the predicted number of units needed for 2020 was estimated. The following ste ps were performed to make this prediction. Each step can be viewed in the following table as well.
• First, the number of possible legs that could be achieved by Sky was estimated. This was determined by assuming that the flight time between each city pair would be at most reduced by half. A two hour turn-around time was assumed for conservatism. Assuming that an airport only operates 20 hours per day, the number of possible legs for one aircraft between each city pair was determined. • From the researched number of flights per week (see Figure 2), the number of flights per day was calculated. This was done by dividing the number of flights per week between each city pair by seven. • From the number of 2008 flights per day, the number of aircraft needed was ca lculated. Then, the number of flights per day was divided by the number of legs that Sky could fly each day. Furthermore, an aircraft was assumed to be out of commission 20% of the time due to maintenance. As a result, more aircraft would be needed.
12 . • The number of passengers that Sky could carry was found to be the number of units needed per day multiplied by 49. • From the number of passengers per week flying between each city pair in 2008, the number of business and first-class passengers flying per day in 2020 was calculated. This was done by assuming a 4.0% increase in passenger travel each year from Boeing’s market outlook for 2008- 2027. Furthermore, the number of business travelers flying per day was assumed to be 15% of total number of passengers. • By looking at the number of business and first-class passengers in 2020 and Sky’s passenger capacity, the number of planes needed was increased by a scale factor. The scale factor was found by dividing the business and first-class passengers in 2020 by Sky’s passenger capacity per day.
2008 Units Pax Business Scale Units*Scale City Pairs Legs/Day Flights/Day Needed Capacity/Day Pax in 2020 factor factor
LA to Tokyo 2 12.00 6 294 932.40 3.17 20 SF to Tokyo 2 11.00 5 245 710.40 2.90 15 SF to Seoul 2 7.00 4 196 466.20 2.38 10 Seattle to Tokyo 2 3.43 2 98 212.49 2.17 5 Seattle to Seoul 2 1.14 1 49 76.11 1.55 2 Tokyo to Singapore 2 2.57 2 98 215.66 2.20 5 Tokyo to Sydney 3 11.86 4 196 811.89 4.14 17 NYC to London 3 10.57 4 196 742.11 3.79 16 NYC to Paris 3 11.14 5 245 666.00 2.72 14 NYC to Amsterdam 3 9.57 4 196 593.60 3.03 13 Boston to London 3 7.00 3 147 461.44 3.14 10 Boston to Paris 3 1.86 1 49 164.91 3.37 4 Boston to Amsterdam 3 3.71 2 98 225.68 2.30 5 Miami to London 3 6.86 3 147 453.51 3.09 10 Miami to Paris 2 3.00 2 98 222.00 2.27 5 Shanghai to Singapore 4 4.00 2 98 266.40 2.72 6 Hong Kong to Singapore 5 8.00 2 98 761.14 7.77 16 Hong Kong to Tokyo 5 10.00 3 147 688.20 4.68 15 Bombay to Dubai 5 10.00 3 147 688.20 4.68 15 Table 5: Units Needed for Each City Pair
By looking at the table above, the total number of units needed to be sold to each city pair would be 203.
Cost Predictions
Using NASA’s Airframe Cost Model calculator [5] and the 203 total units needed to accommodate all of Sky’s city pairs, a crude cost of each unit was estimated and can be seen in the chart below. After researching the QSST, SBJ, and Concorde’s sell price and number of units to be produced, a cost analysis of these companies was also made. The calculator estimated cost in millions of 2004 dollars, which was
then converted to 2009 dollars using a 1.07 inflation rate [10] . A cost analysis was not done in 2020 dollars
13 . because the competition is currently selling their units at today’s price. In order for OceanAire to make a reasonable profit each unit needs to be sold at roughly 200 million dollars. This is a reasonable value since both the QSST and SBJ are currently being sold at 80 million each and Sky will hold almost 6 times as many passengers. OceanAire’s estimated profit over a 10-15 year period is 11.9 billion dollars. Traveling to more city pairs will be looked into to see if the demand of Sky units could be increased and therefore, the cost of each unit possibly reduced.
We Max Speed # of Test Production Sell Price CALCULATOR 2009 PROFIT (lbs) (mph) Units Quantity (Units) (Millions) (Millions) 2004 (Millions) (Million) 10-15 years QSST 80071 1190 2 350 80 59.8 63.9 5635 SBJ 45139 1058 2 300 80 37.7 40.3 11910 Concorde 173500 1336 2 20 374.5 827.1 885 -10210 Sky 96359 1322 2 170 200 104.2 11.5 11875.5 Table 6: Cost Analysis
Meeting Customer Needs
Numbers of considerations were taken into account to determine customers’ needs. The majority of customers on Sky are 1 st class customers and business class customers. Thus, luxuriousness while maintaining efficient cabin spacing was heavily weighted.
Comfortable chairs and innovative interior design will provide for a luxurious cabin space. To accommodate for the comfort of the passengers with constrained cabin spacing, the 1 st class seat pitch will be 60 inches (see Figure 4), and the business class seat pitch will be 50 inches. The majority of international business seats pitches range from 60 to 70 inches, and the 1 st class seats pitches range from 70 to 80 inches. Since our aircraft flies equivalent distances as other subsonic aircrafts in a shorter amount of time, seat pitch was lessened compared to other competing subsonic aircraft. Luxurious entertainment and communication capabilities are intended to improve passenger productivity during flight. The specifics for in-flight entertainment and communication capabilities will be investigated in the future. Lastly, the empowering strength in our aircraft is in its ability to fly long distances in a significantly shorter duration.
= 60 ”
Figure 4: First Class Seat Pitch [12]
14 . Payload/Passenger Capacity
Spacing efficiency in the aircraft was a major focus in order to optimize passenger capacity within designated aircraft spacing while enabling optimal profit and allowing for effective use of space without inhibiting the comfort of passengers. The eradication of needless uses of spaces will effectively cut down on the costs.
Enhancing flight efficiency through optimization of aircraft payload can be done by avoiding unnecessary payloads such as limiting passenger check-in baggage to 50 pounds per customer. This can significantly decrease the payload. The majority of passengers are business oriented and statistically, they do not carry a lot of luggage. With these considerations, the following payload distribution was determined.
Passenger Total Weight (lbs/ passenger (or crew)) 4 Crew Members 180 4 Crew Members (check in baggage) 30 49 Passengers 180 49 Passengers (check in baggage) 50 49 Passengers (carry on baggage) 15 Conclusions
Wpayload 12005 Wcrew 840 Table 7: Payload Distribution
Cabin Layout
The Sears-Haack body was implemented to design an aircraft fuselage that is lease susceptible to wave drag. The average international business class seat width in the present competing market is 21 inches [11] . With our cabin layout, the seat width for business class is 3 inches larger than the competition. For the international first class, the average airline seat width is 25 -26 inches [11] . With the cabin layout described below, the seat width for our aircraft is is 30 inches. There will be 49 passenger seats for the aircraft consisting of 10 first class seating and 39 business class seating. Table 8 displays all aforementioned dimensions, and Figure 5 shows cabin layout.
First Class (inches) Business Class (inches) Seat Pitch 60 50 Seat Width 30 24 Aisle Width 30 20 Table 8: Cabin Dimensions
Figure 5: Cabin Layout
15 . Design Mission Profile
The mission profiles will be one of the tools used to design the aircraft. It plays an important role in the sizing of the plane and the constraints diagram as well as other design considerations. Two different profiles will be used: the design and the economic mission profiles. Both will be discussed in further details thereafter.
The design mission profile is based on the longest flight in the worst conditions. This is to ensure that our aircraft will be able to meet certification requirements such as climb rates and emergency procedures in case of the loss of an engine, and that it will be able to cover all the routes included in our market analysis. The longest flight to be covered is the San Francisco to Seoul route. On top of the link between these two cities, the aircraft must be able to reach an alternative airport 200 nmi away and loiter there as well. Figure 6 shows the design mission profile.
H
G N E F I J M K O D A C L P Q B 55 nmi 200 nmi 275 nmi 5,155 nmi Figure 6: Design Mission Profile
Each segment is explained in more detail below: Segment Description A-B Taxi 9 min ;
Accelerate to V LO ≥ 1.1∙V STALL and liftoff with one engine inoperative within a 11,800 ft runway B-C 1st segment climb:
Take off to 35 ft at V TO ≥ 1.2 ∙ V STALL with one engine inoperative, gears down at a rate ≥ 2.4% C-D 2nd segment climb:
Climb to 1,500 ft at V CL ≥ 1.25 ∙ V STALL with one engine inoperative, gears up at a rate ≥ 1.2% D-E 3rd segment climb: Climb to 10,000 ft at 250 KCAS with all engines operating, gears up at a rate > 3% E-F Accelerate to best climb speed F-G 4th segment climb: Climb to best cruise altitude at best climb rate G-H Step cruise for best range (5,155 nmi accounting for head winds and range credit during climb) at M = 1.8. (See below for calculation) H-I Descend to 10,000 ft (no range credit) I-J Decelerate to 250 knots J-K Descend to 1,5000 ft at 250 knots
16 . K Loiter for 30 min
K-L Approach at V A ≥ 1.3 ∙ V STALL L-M Missed approach, climb at V CL ≤ 1.5 ∙ V s at a rate ≥ 2.1% with one engine inoperative, gears up OR
Missed landing, climb at V CL ≤ 1.3 ∙ V s at a rate ≥ 3.2% with all engines operating, gears down) Climb to 10,000 ft M-N Cruise for be st range to alternative airport (200 nmi) with one engine inoperative. N-O Decelerate to 250 knots and descend to 1,500 ft O Loiter for 30 min
O-P Approach at V A ≥ 1.3 ∙ V s P-Q Land over a 50 ft obstacle at V TD ≥ 1.15 ∙ V STALL and stop within a 11,800 ft runway Table 9: Design Mission Description
The range between Seoul and San Francisco is 4,919 nmi, but head winds must be accounted for in order to find the true air nautical miles that have to be covered. An assumption of 100 knots head winds was made, and the new necessary range to be covered was calculated. It was also assumed that, for now, Sky is going to cruise at 50,000 ft. This was based on the cruise altitude of the Concorde, but further investigations will have to be performed to find the most efficient cruise altitude. At this altitude, Sky will be above subsonic traffic and will be free to fly supersonic. Range credit was also given to the climbing segments. Assuming a 3% climb rate, it takes 274 nmi to reach a 50,000 ft altitude. Therefore, the ground that now needs to be covered is reduced to 4,645 nmi. In conclusion, at 50,000 ft, a = 573.56 knots and M = 1.8 = 1031 knots.
With head winds, the ground cruise speed is 931 knots. At this speed it takes exactly 5 hours to cover 4,645 nmi. The number of air miles to be flown in order to later calculate the fuel weight fraction needed is of interest here. In 5 hours at 1031 knots, the still air range is 5,155 nmi.
Economic Mission Profile
The economic mission profile will be used later to calculate the direct operational cost on the flight route that is flown most frequently. In the market analysis, it was determined that this route has to belong to the 2,500 nmi to 3,000 nmi range, and that New York (JFK) to London (HEA) happens to also be the most flown path. On the take off and approach of both JKF and HEA, a detour must be taken to minimize the time spent over land, and therefore, be able to reach a supersonic speed as early as possible. Figure 7 and 8 show the approaches of London Heathrow and New York JKF respectively. This procedure deviates from the great circle path but it will enable us to be more efficient overall. In all segments of the profile, the aircraft is in normal flying conditions and no emergency procedures have to be followed.
17 .
Figure 7: London Heathrow Approach
Figure 8: New York JFK Approach
18 .
Below is the profile of the economic mission:
H
G J E F I K D C L M A B
Figure 9: Economic Mission Profile
Segment Description A-B Taxi (9min);
Accelerate to V LO ≥ 1.1 ∙ V STALL and liftoff B-C 1st segment climb:
Take off to 35 ft at V TO ≥ 1.1 ∙ V STALL , gear down at a rate > 0% C-D 2nd segment climb:
Climb to 1,500 ft at V CL ≥ 1.2 ∙ V STALL , gear up at a rate > 3% D-E 3rd segment climb: Climb to 10,000 ft at 250 KCAS, gear up at a rate > 3% E-F Accelerate to climb speed F-G 4th segment climb: Climb to best cruise altitude at best climb rate G-H Step cruise for best range (3,000 nmi) at M= 18 H-I Descend to 10,000 ft I-J Decelerate to 250 knots J-K Descend to 1,500 ft K Loiter 30 min
K-L Approach at V A ≥ 1.3 ∙ V STALL L-M Land over a 50 ft obstacle at V TD ≥ 1.15 ∙ V STALL Taxi to gate (9 min) Table 10: Ecomonic Mission Description
19 . V. SYSTEM DESIGN REQUIREMENTS
Customer Attributes and Quantifiable Characteristics
In order to define and generate requirements for this design, a house of quality was created. The first step in doing so was to brainstorm all the customers, both internal and external, that would be affected by Sky. The four particular customers that were chosen were the airline, the passengers, the public, and NASA and Lockheed Martin. The following needs and wants were generated for each of the customers based on what was believed to be important to them as it related to the design of Sky.
Airline Passenger Public NASA/Lockheed • Airport compatible • Comfort • FAA requirements • Supersonic cruise • Maintenance cost • Cargo • Quiet efficiency • Operational life space/payload • Low emissions • Low sonic boom • Turnaround time • Fast trip time • High lift for takeoff • Oversea Range • Affordable ticket and landing price
Table 11: Customer Attributes
Quantifiable Characteristics
After establishing customers’ needs and wants, the next step was to identify how Sky will meet those specific needs and wants. Following are the quantifiable characteristics that were chosen in order to assure that there was at least one characteristic that could be quantified for each of the above customer attributes:
• Takeoff field length • Landing field length • Door height above ground • Airframe life • Range • Number of passengers • Cruise Mach number • Cabin volume per passenger • Operating cost • Cruise altitude • Cruise efficiency • Cumulative certification noise • Stall speed • Wing span • NO x emissions
20 . House of Quality
With these attributes and characteristics, a house of quality was created.
Figure 10: House of Quality
The relative importance of customer needs and wants were also determined. FAA requirements, supersonic cruise efficiency, and airport compatibility were ranked as the top three customer attributes. This was mainly because, for one, Sky cannot fly without meeting FAA Requirements or without being able to land and take off from airports. Also, the objective of this specific aircraft is to fly efficiently at supersonic speeds. Without meeting that attribute, Sky would be designed for a purpose outside of this specific mission profile.
Once the house of quality was completed with how strongly the requirements affected the customer’s needs and wants, it became evident that the top two engineering characteristics in terms of importance in the design of Sky were cruise Mach number and cruise efficiency. Thus, these two requirements will remain the major focus for the design of Sky.
21 . Targets and Threshold Values
Lastly, to finalize the house of quality, initial target and threshold values were established. In the requirements compliance matrix, these values are listed and compared to design values based on simple Excel formulas. As shown in Table 12, the important target and threshold values are listed per the initial sizing design of the aircraft.
Requirement Unit Condition Target Threshold Design Date Takeoff Field Length [ft] < 10,000 11,800 11000 Range [nmi] > 5000 4000 3500 1/25/2009 1/25/2009 Payload [pax] > 49 35 49 Cruise Mach # [N/A] > 1.8 1.6 1.8 Cruise Efficiency [lb fuel/pax -nmi] < 0.25 0.33 0.36 Certification Noise [PldB] < 50 70 69
Cabin Volume per Pax [ft^3/pax] > 11 9.7 8 1/27/2009 Cruise Altitude [ft] 50000 60000 0
Aircraft Life [years] > 30 20 28
Aspect Ratio [N/A] < 2 3.86 2.2 1/29/2009 1/29/2009 Thrust to Weight Ratio [N/A] > 0.37 0.3 0.3 Wing Loading [N/A] > 125 95 100 Crew [crew] < 3 5 4 Table 12: Requirements Compliance Matrix
This Excel table is set up so that once a requirement is agreed upon, it can be inserted into a new row, and a target and threshold value can be determined for it based on sizing. The condition column shows the preference that the design values will take in order to meet the best idea of the aircraft design. The target values are based on either requirements for the design competition or design mission. The threshold values are also either based on the design competition or values that were necessary for an efficient and obtainable aircraft design. The design column is color-coded based on a conditional Excel formula. If a design value is in the range given by the target and threshold values, then the column will appear green to signify a working constraint. If the design value does not match the requirement, then it appears red and denotes a sizing quality that needs work. The table above contains some correct and incorrect design values to show the Excel formulas.
Benchmarking
Once the requirements compliance matrix was completed and inserted into the QFD, the next step was to take a look at some other similar aircraft and/or concept designs in order to evaluate the
22 . effectiveness of the design and to compare it to other competitors. Below in Figure 11, the benchmarking of other similar supersonic transports can be viewed.
Figure 11: Benchmarking Analysis
In the benchmarking analysis, the chosen competitors were the Concorde [2][8] , the Lockheed Martin Quiet Supersonic Transport (QSST) [14] and the Aerion Supersonic Business Jet (SBJ) [1]. The Concorde was chosen since it was the only supersonic transport aircraft to ever go into production. Although it did eventually fail, it was a necessary aircraft to study. The Lockheed Martin and the Aerion jets were also analyzed due to their high possibility as future competitors of Sky. Once the competitors were established, the effectiveness of each aircraft based on the customer needs/wants were analyzed. The scale used ranged from one to five; one being an abysmal score and five denoting that the aircraft completes the requirement well. There were two important aspects to the benchmarking done. After looking at the aircrafts, certain focuses were established based on which customer needs/wants each
23 . competitor fulfilled well. As described in the discussion on the QFD, the three most important customer requirements were airport compatibility, FAA regulations and supersonic cruise efficiency. Having these focal points will allow Sky to be designed more efficiently and in an optimal manner. Other important aspects taken away from the benchmarking analysis were the shortcomings of the competitors, especially for the Concorde. Being able to discuss the areas where the Concorde performed poorly will allow for Sky to be designed in such a way that its performance will exceed the Concorde.
Technologies and Advanced Concepts
Another aspect in the design of Sky will be to delve into possible technologies and advanced concepts that may be used to help make it more efficient and cheap. The first important facet of any aircraft, especially one that can fly supersonic, will be engine design/selection. Due to Sky flying supersonic for over 4000 nautical miles, the engine selection will need to be one which is quite powerful as well as efficient. The first engine to be considered was the Pratt and Whitney JT8D-219 turbofan, which will be used on the Aerion SBJ. This is a powerful engine; however, there is a possibly that it will not provide enough thrust for Sky’s much larger payload capacity. Military engines were also discussed, but later nixed due to the fact that they are extremely loud for civilian airports, and the technologies used might not be possible for use on commercial applications. From the analysis, however, it has be decided that a possible military derivative will be used. Another decent possibility will be a variable cycle concept engine or a medium bypass turbo fan concept that is still in production, but may be in operating condition by 2020.
Another important technology to consider for Sky will be the use of different materials for various components on the aircraft. The most obvious choice for aircraft with an IOC of 2020 is carbon fiber reinforced plastic. Some basic characteristics of carbon fiber reinforced plastics (CFRP) are that they are quite strong, lightweight, and if prepared correctly, have a very long lifetime. In many areas of the aircraft, CFRPs will be used to save weight and allow for a more streamline aircraft to be produced. In the industry now, most materials used for skins are aluminums that have been used for decades.
Aluminum such as 2024 and 7075 are still being used today [17] . However, in an aircraft such as Sky that will have to efficiently fly supersonic for many decades, other materials will have to be used. Another possibility for 2020 will be the use of new nanotechnology imbued materials.
As with engine and material selection, wing configurations will be an important aspect of Sky. The first configuration that was looked into was a non-planar configuration. Using this type of wing setup would allow for a reduction in induced drag, as well as an increase in the lift-to-drag ratio in the supersonic flight regime [9] . Similar to the configuration used on the Concorde, the possibility of using a delta wing or derivative, as well as canards, will also allow for increased stability and a wing configuration that will remain inside the Mach cone. Whichever wing configuration is chosen, it will most likely be one with a low apesct ratio and a wing that is aft-fuselage, similar to that on the Aerion and Lockheed Martin concepts. Another important idea to think about is the use of compression lift via the supersonic regime. By altering the underside of the aircraft during the supersonic flight, compression will allow for more lift to be created, and the lift-to-drag ratio can be increased.
24 . VI. INITIAL SIZING
Once the requirements for the aircraft had been drawn up, the next step was to predict the size of the aircraft. It is very important to predict of the size of the aircraft as it helps immensely in making an initial educated guess about other aspects of the aircraft such as the amount of thrust required, total weight of the aircraft, the empty weight fraction, specific fuel consumption, Aspect ratio for the wings, lift to drag ratio among others. The logic behind the sizing algorithm used is explained as follows.
Estimates for L/D
Because of the fact that sizing is an iterative process, many variables and parameters had to be determined and/or estimated. The goal was to design an aircraft that would be as lightweight as possible, while being able to achieve all of its mission goals. In order to successfully come up with a lightweight aircraft, the design variables and parameters which were most important had to be determined. Range, payload, and maximum and cruise Mach numbers were already decided upon, so the next step was to determine the supersonic maximum lift-to-drag ratio, subsonic maximum lift-to- drag ratio, cruise lift-to-drag ratio and loiter lift-to-drag ratio. For the initial sizing, these ratios were estimated using the Thomas Corke equations, as follows:
M < 1: L/Dmax ≈ 1.4AR + 7.1 Equation 1
L/D loiter ≈ L/D max Equation 2
-0.5 M ≥ 1: L/D max ≈ 11M cruise Equation 3
L/D cruise ≈ 0.86L/D max Equation 4
Empty Weight Fraction Predictor
In the supersonic regime, the lift-to-drag ratios (max and cruise) are based on the cruise Mach number. In the subsonic regime, the lift-to-drag ratios (max and loiter) are based on the aspect ratio. Since the cruise Mach number was already determined, the supersonic lift-to-drag ratios could be calculated. In order to calculate the subsonic lift-to-drag ratios, and thus, continue the initial sizing process, it was necessary to determine an estimate for the aspect ratio along with other parameters such as thrust-to-weight ratio and wing loading. These estimates were obtained through the use of an aircraft database compiled by Professor Crossley, which housed many different types of supersonic aircraft, both military and commercial. Data for each of the aircraft including gross takeoff weight, empty weight, empty weight fraction, aspect ratio, thrust-to-weight ratio, wing loading and maximum Mach number were obtained from various sources (sited in the References section). It was decided that the database would be altered due to the fact that there were some aircraft originally omitted that were similar to our potential design and could be useful in obtaining an estimate for some of these initial parameters. The Tupolev Tu-144 [16] , Aerion Supersonic Business Jet [1] and the XB-70 Valkyrie were
25 . added, while the Boeing/McDonnell-Douglas HSCT was deleted due to a lack of specifications. The database can be seen below in Table 13:
2 Aircraft W0 [lb] We [lb] We/W 0 AR T/W 0 W0/S [lb/ft ] Mmax Northrop F-5E 15,745 9,588 0.608955 3.86 0.64 84.7 1.51 Lockheed F-104G 27,300 13,996 0.512674 2.45 0.57 139.2 2 Lockheed Martin F-16C 28,050 19,643 0.700285 3.2 1.03 93.5 2 Convair F-106A 34,510 24,038 0.696552 2.1 0.7 49.5 2.31 McDonnell Douglas F-15C 44,500 28,700 0.644944 3.01 1.07 73.2 2.54 Republic F-105D 48,976 26,855 0.54833 3.16 0.5 127.2 2.08 McDonnell Douglas F-4E 53,848 29,535 0.548488 2.77 0.66 101.6 2.25 Lockheed Martin F-22 60,000 31,670 0.527833 2.4 1.162791 71.43 1.7 Boeing F-15E 81,000 31,600 0.390123 3 0.578035 133.22 2.5 General Dynamics F-111D 82,819 46,172 0.557505 1.95 0.57 124.5 2.2 Lockheed YF-12A/SR-71 140,000 60,000 0.428571 1.717422 0.428571 77.8 3.3 SAI/LM QSBJ 153,000 70,000 0.457516 2.040617 0.431373 78.6632391 1.8 Convair B-58A 163,000 55,560 0.340859 2.09 0.38 105.7 2 Concorde 408,000 173,500 0.425245 1.829876 0.373039 105.809129 2.2 Boeing B-1B 477,000 190,000 0.398323 3.13 0.3 202.6 2.2 Tupolev Tu-144 410,000 186,000 0.453659 1.893207 0.44 84.2 2.35 Aerion SBJ 90,000 44,600 0.495556 3.4347 0.217778 75 1.6 XB-70 550,000 210,000 0.381818 1.751112 0.314 84.93 3.1 Grumman F14D 74,349 43,735 0.588239 7.28 0.758585 96 1.88 Table 13: Supersonic Aircraft Database
Estimates for the aspect ratio and wing loading were determined from the aircraft database with special attention to the Concorde, Tu-144, and the Aerion SBJ. The missions of these aircraft were determined to be most similar to the potential design, and thus, also to the design specifications. Using the aspect ratio estimate, the estimate for the subsonic lift-to-drag ratios could be determined. It was also necessary to determine an estimate for the specific fuel consumption. This was a little more difficult to do, leading to a less accurate estimate. The educated guess was made that the engines would be low to medium bypass turbofan engines. Thus, the Pratt and Whitney F119-PW-100 engine, which was used on the F-22 Raptor, was used as an initial “model”. Specifications for the engine were difficult to come across, but a specific fuel consumption of 0.78 1/hr was found on a forum for the F119.
Once the database was created and the parameters to be used for the initial sizing prediction were decided upon, Matlab was used in order to determine an equation for the empty weight fraction
(W e/W 0). This was done by first using a least squares regression in order to calculate the coefficients for this equation, which takes the following form:
c we/w 0 = aw 0 Equation 5
However, this equation can be written as a function of more variables if they are deemed important in
affecting we/w 0. In the case for initial sizing, these other variables were determined to be w0, AR, T/ w0, wo/S, and M max . In order to include all of these variables, the function for we/w 0 can be written as a constant plus the product of all the previous variables, raised to some exponent, as shown in Equation 6 below.
26 .
c1 c2 c3 c4 c5 we/w 0 = a + bw0 AR T/w0 w0/S Mmax Equation 6
If coefficient a is assumed to be zero, then the natural log of both sides of the equation can be taken. This makes the equation linear, and it takes the following form:
ln(we/w 0) = ln(b) + c1ln(w0) + c 2ln(AR) + c 3 ln(T/w 0) + c 4 ln(w0/S) + c 5 ln(M max ) Equation 7
Each side of the equation can then be written in vector form; say, vector f for the left side of the equation, and vector x for the right side of the equation. These vectors will be generated from the data
in the initial sizing database. For example, we/w 0 for each aircraft in the database will be inserted into a column vector as follows: