Thin-Haul Transport and

Air Taxi Aircraft Design

System Requirements Review

Purdue University, Spring 2019

AAE 451 Team 4

Sam Buck, Nicholas Turo-Shields, Joseph Tenney

Nicholas D’Onorio, Liam Ochoa, Tristan Zabicki

7 February 2019

Supervisor: Dr. William Crossley

Contents

1 Executive Summary 2

2 Nomenclature 3

3 Study Objective and Mission Statement 33.1 AIAA RFP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2 Mission Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

4 Market Analysis and CONOPS 44.1 Potential Market Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.2 Primary Market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.3 CONOPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94.4 Design Mission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.5 Additional Markets for Consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5 Aircraft System Design Requirements 14

6 Baseline Aircraft 156.1 Selection of Baseline Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156.2 Beechcraft Baron G58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156.3 Daher TBM 700C2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176.4 Limitations of Baseline Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7 Technologies and Advanced Concepts 197.1 Hybrid Propulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197.2 Composite Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

8 Sizing Tools 228.1 Aircraft Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Appendix: MATLAB Code 24

1

1 Executive Summary

Black Tie Air is an aircraft design company whose mission is to provide an aircraft for luxury on-demand

service to popular business locations around the country. The company was founded by a group of Purdue

Aerospace Engineering students in Purdue’s 451 senior design course. The team used the American

Institute of Aeronautics (AIAA) 2018-2019 Thin Haul Transport and Air Taxi design competition as a

starting point and guide for the aircraft design but ultimately decided to focus on the luxury market.

Upon completing some initial market research, the team determined that the Air Taxi/Thin Haul market

was highly saturated with aircraft carrying out the mission of the AIAA request for proposal with ease.

The team felt that even a very well designed aircraft would only be a marginal improvement on the current

fleet and the team was not confident about competing in this market space.

When narrowing in on our market the team considered the following analogy: Consider the taxi cabs in a

big city like New York City. The Ford Crown Victoria is a common car to be used as a taxi cab because

it is cheap, reliable and gets the job done. Even if our team designed a car that was in our marginally

better than the Crown Victoria it would be hard to convince taxi drivers that they need to upgrade their

cars from something that already fits their needs. Now consider a luxury car service. The luxury car

service in order to appease its customers needs the latest and greatest cars to keeps its clientele happy.

For this reason our team decided to focus on the luxury market as a better business prospect.

Our city-hopper aircraft will service business men and women and help them travel comfortably to and

from business meeting in neighboring cities. Some additional markets the team is also targeting include:air

taxi, individual ownership, cargo operations and aeromedical. Design requirements were developed start-

ing with the RFP and adding additional requirements including cabin volume, and wing loading to assure

the best experience for passengers.

The team selected the Beechcraft Baron G58, and Daher TBM 700C2 as the baseline aircraft which will be

used as references during the design process. Features from each will be drawn from and improved upon

to create our proposed aircraft. Advanced technology will also be implemented in the aircraft design.

Research is being done into technologies such as hybrid propulsion and composites to evaluate their

technology readiness level for service in 2025 and the benefits they can provide in the teams design.

Moving forward the next steps for the team include: continuing to develop and validate the sizing code,

complete constraint diagrams, and create a geometric representation of the baseline aircraft.

2

2 Nomenclature

AIAA American Institute of Aeronautics

FBO Fixed-Base Operator

TRL Technology Readiness Level

RFP Request for Proposal

VLJ Very Light Jet

3 Study Objective and Mission Statement

3.1 AIAA RFP

The objective of the AIAA design competition is to design a domestic transport aircraft for the thin haul

or on-demand service operations that service small airports and short routes.

3.2 Mission Statement

The mission of Black Tie Air is to provide our customers with luxury on-demand service to the country’s

most popular business locations.

3

4 Market Analysis and CONOPS

4.1 Potential Market Overview

To find a profitable niche in the market into which an aircraft may fit, we will begin with two extremely

general sizing requirements given by the AIAA RFP: carrying 2-6 passengers and having a maximum

speed of greater than 180 knots. For reference, we select the two most-produced series of civil aircraft,

currently in production, which easily meet these requirements: the Beechcraft Baron and the Cirrus SR22.

Both models have seen thousands of aircraft produced, and both are used in civilian applications within

the United States, making them excellent representatives of the aircraft market in question.

The Beechcraft Baron is a 6-seat, twin piston engined light aircraft with a storied history as a versatile

transport. First sold in 1961, the Baron is generally sold to private individuals and small businesses for

individual use. At a price of almost 1.5 million dollars [1], the Baron is one of the most expensive aircraft

of its class, largely due to its branding and reputation as a luxury model. Most of the Baron’s market,

therefore, is individuals who own their own aircraft and are willing to pay a premium for luxury features

therein. A smaller number of owners are charter aircraft operators, who use the Baron for luxurious,

on-demand executive transport. A notable secondary market does exist as a training aircraft for flight

schools and tourism, generally using secondhand, lower-cost airframes. The G58 has little to no use in

the air taxi market, however, as its cost renders it a relatively difficult aircraft from which to make a

profit.

The Cirrus SR22 is a 4-seat, single piston engined, composite aircraft, which has grown an impressive

presence in the small aircraft market. The SR22 was introduced in 2001 and has sold over 5,700 airframes,

making it one of world’s best-selling aircraft [1]. At a price around $600,000, the Cirrus is accessible to

a diverse set of markets [1]. While individual and private sales comprise a large proportion of owners,

the airframe is used by flight schools, air taxi companies, tourism operators, and a variety of other niche

businesses, including aerial photography and surveying [1].

This application encourages us to examine the air taxi market more closely. The AIAA RFP encourages

the development of the aircraft for air taxi use, so it is sensible to investigate how many aircraft of this

type the market would support purchase of in 2025. The two largest and most notable operators of the

SR22 as an air taxi have been ImagineAir, with a fleet of around 30, and SATSair, with 26 [2, 3]. Both

of these operators flew SR22s in an on-demand fashion, offering fares for transport from one airport to

4

another. Both operators, however, have also gone out of business, suggesting that aircraft in the range

of the SR22 may not provide sufficient profit when operating as an air taxi. This conclusion is further

supported by the recent actions of Hopscotch Air, another similar company. Hopscotch Air, which also

flew SR22s on demand for fares, has transitioned to a membership model, requiring anyone wishing to

buy a ticket to first pay a steep monthly membership fee [4]. These data provide compelling evidence

against the long-term profitability of SR22-like aircraft as air taxis.

Despite the uncertain viability of aircraft like the SR22 in the air taxi market, air taxi operators are

finding success with other platforms. The largest air taxi organization in the United States, Cape Air,

flies a fleet composed, almost exclusively, of Cessna 402 airframes [5], outfitted to seat nine passengers.

As these aircraft are aging, Cape Air has elected to order 100 Tecnam P2012 Travellers [5], also designed

for nine passengers. Similar (though smaller) air taxi services exist flying the Cessna 208 Caravan and

Beechcraft King Air, also designed to carry nine passengers. The nine passenger requirement represents

a hard upper limit to the air taxi market in many cases: aircraft carrying nine or fewer passengers may

be certified using the FAR Part 23 guidelines, while those with ten or more must adhere to the more

stringent Part 25 (though waivers are available in some circumstances). All of these aircraft are far larger

than both the SR22 and Baron, indicating that an aircraft designed primarily for the needs of air taxi

organizations would be far larger than that envisioned in the AIAA RFP. While such a market may buy

some aircraft of the target size for a variety of reasons, we cannot assert that the market exists with

enough confidence to “bet the company” on such a proposal.

Understanding that the air taxi sector is not a viable market for our potential aircraft, we will return

to the first example aircraft to develop a business case. As a luxury aircraft, the Baron has seen high

market penetration in private service, and a smaller, but still significant, amount of use in charter service.

Both of these markets are much more expansive, with especially the charter market having a significant

amount of flexibility to use an aircraft of the size we intend. It is these customers to whom we will turn

in order to sell the aircraft.

4.2 Primary Market

Charter operators and small airlines regulated under FAR Part 135 will be the customers for whom the air-

craft is primarily designed. An aircraft used in such a market would typically be operated on an as-needed,

unscheduled basis as a luxurious option for the transport of small groups of people between nearby cities,

5

allowing clients to bypass traffic, discomfort, and delays associated with ground transportation.

The charter aircraft market generally caters to individuals and businesses requiring fast, flexible travel

options who are less sensitive to cost. In general, the individual or individuals being transported have not

organized the logistics of the flight nor will they ever see the bill: these tasks are generally the responsibility

of secretaries and travel managers, working with relatively large executive budgets [6]. While this does

mean that small differences in the price of a flight are less important than in other sectors, inefficiencies

or exorbitancies which inflate the price of a flight may still prove problematic, especially if they have a

large effect on the customer’s total required transportation budget. This is especially true if customers

have a financial stake in the aircraft, as is the case with fractional ownership organizations. Operationally

similar to standard charter companies, fractional ownership systems allow customers to purchase a certain

percentage of the airframe and thus grant them a certain number of flight hours on it or other company

aircraft [7].

The fleet of aircraft in charter or fractional service is dominated by medium range turboprop and jet

aircraft, which can provide short flight times and luxurious accommodations for passengers. These air-

craft are generally larger than required for short range, low passenger missions, with the Piper Navajo

representing the smallest aircraft commonly observed in charter service [8]. We envision an aircraft which

would fall at the bottom of this market, serving a shorter-range, fast executive transport role with more

desirability, and thus marketability, than current offerings.

To provide an offering in this market space, it is prudent to examine which aircraft are currently competing

within the market. The Baron, clearly, is widely considered a leader within this short-range luxury space.

The Piper Seneca (and retired Piper Navajo) have similarly seen service with charter operators [8]. The

Piaggio P.180 Avanti also has a similar passenger capacity, and is popular with business and executive

passengers due to its roomy cabin and high speed [1]. Additionally, the very light jet (VLJ) market,

including the Honda HA-420 and Embraer Phenom 100, offer rapid, short range transport in a smaller

cabin [1]. While these are clearly not a comprehensive list, we will use these aircraft to form a working

estimate of the market available for our aircraft.

6

Table 1: Selected Competitive Aircraft [1]

Manufacturer Model Series Number Sold Unit Price Years on MarketAircraft Produced

per Year (est.)

Beechcraft Baron G58 2,494 $ 1.4 Million 58 43Piper PA-34 Seneca 5,122 $ 1.0 Million 47 109

Piaggio P.180 Avanti 234 $ 7.7 Million 32 7.3Honda HA-420 HondaJet 110 $ 5.0 Million 3 36.6

Embraer Phenom 100 374 $ 4.5 Million 10 37.4

The Piper and Beechcraft, which have both been on the market for many decades, are clearly relatively

dominant. The raw number of aircraft currently in operation, however, is a poor measure of how many

aircraft we may be able to sell. Because the Piper and the Beechcraft have been in production for so long,

many of the aircraft included in their sales numbers have been retired or otherwise scrapped. Because

our company will not have decades of sales to build off of, it makes sense to normalize the aircraft sales

numbers by number of years in production.

From Table 1 we can begin to get a better idea on the number of aircraft a successful company should

be able to sell in a given year. Together, these aircraft have a mean production rate of 46.6 and a total

rate of 233, so we will use a figure of 230 aircraft per year as a rough estimate of the market’s total size.

The share of this market we can capture in 2025 will be determined by how well we are able to meet the

needs of the charter operators who will purchase the aircraft.

By comparing dual requirements of comfort and speed, we can form an understanding of how a competitive

aircraft will perform. The VLJ market leads in terms of speed. Represented in Table 1 by the HondaJet

and Phenom 100, these aircraft tend to have small cabin volumes (6.5 m3 for the HondaJet) but high top

speeds (over 400 kt for both). In contrast, aircraft with more cabin volume, such as the King Air (8.5 m3)

operate at far slower speeds. An interesting aircraft which combines both of these features is the P.180

Avanti, which has a cabin volume of 12 m3 and maximum speed of 400 kt. The penalty for this, however,

is a massive price: Piaggio produces 8 aircraft per year and sells each for $8 Million USD.

Because we are choosing to constrain ourselves to a propeller-driven airframe 1, the vehicle should fill a

role where higher speeds are less important our customers. This is primarily the case over shorter ranges

where the aircraft has a smaller distance to travel in cruise flight. Figure 1 shows the additional time a

250 kt propeller-driven aircraft will take over a route compared to a 400 kt turbofan-powered one.

1We feel that using turbofans would begin to deviate from the spirit of the RFP and the course

7

0 200 400 600 800 1000

Distance (nmi)

0

10

20

30

40

50

60

70

80

90

Dela

y (

min

)

Prop Delay as a Function of Distance

Figure 1: Extra flight time required for propeller aircraft at various ranges

As seen in Figure 1, travelling more than around 650 nmi will result in a flight that is longer by over an

hour. We choose this to be our cutoff for the purpose of defining the market. The psychological difference

between an aircraft taking an extra hour compared to an aircraft taking 55 minutes is significant [9], and

so we anticipate that staying below one hour of additional trip duration will improve our ability to market

the aircraft. This, therefore, dictates a range of 600 nmi as a reasonable goal for the aircraft. It also

informs a speed of 250 kt or above.

With these parameters established, we can compare the expected performance of our aircraft to that

of other aircraft in the market. Compared to the Baron (Table 3), the concept is significantly faster,

yet significantly shorter ranged. To attract our desired customers, our concept would also likely need

to include a much larger cabin volume, increasing passenger comfort. The Avanti is therefore a more

comparable aircraft than the Seneca or Baron, from the point of view of the market analysis. Because of

this, we predict that our aircraft will have a production frequency on the lower end of the range seen for

its competitors. To the 40 aircraft per year figure of the Baron we therefore apply a scaling factor of 0.75,

8

as we anticipate that our aircraft will be far closer to the Baron than the distinctive, specialized Avanti.

We therefore anticipate being able to supply 30 planes per year to the market.

If our intention is to market and sell the aircraft to luxury clients, including charter operators and

executives, it is important to discuss an additional important concern: aesthetics. Many individuals who

purchase this aircraft will likely do so because they like its look or brand, not because of its performance.

While form should always come before function, it is especially important, when considering customers of

high net worth, to be conscious of the aircraft’s appearance and design. Configurations and changes which

make the aircraft subjectively ugly should therefore be treated with more skepticism than would otherwise

be the case, and opportunities to add quality or aesthetically pleasing elements should be seized. Due to

the subjective nature of this topic, however, we will not include a quantitative requirement regarding the

aircraft’s physical attractiveness.

4.3 CONOPS

As the aircraft will fit into a mature market, the infrastructure and lifestyle requirements for such a vehicle

are well-established and simple to meet. Because the aircraft is designed for travel between executive

airports, we can safely assume it will operate at airports with full-service Fixed Based Operators (FBOs).

FBOs can be assumed to have fuel and basic services, such as weather reports and transportation, available

for use by the aircraft’s operator and occupants. While some FBOs are able to provide very simple

maintenance assistance, operation of the aircraft will also require more intensive routine maintenance,

and thus a facility in which to do so.

The aircraft can generally be assumed to be based at a specific regional airport capable of providing

maintenance and fleet management service, from which it is dispatched. This base would also ideally be

located nearby the place of residence of the aircraft’s pilot, allowing them to commute to work. On a

typical day, an aircraft in charter service may be scheduled for three to four flights, though the exact

tasking for these flight will vary greatly. As a reference, we will describe what could be considered

a standard operational day, with the understanding that such an outline is purely an example of one

possible scenario. This example will consist of a two-stop executive transport flight, followed by a two-

stop return to base. In this example, the aircraft is based at Purdue University Airport in West Lafayette,

Indiana (KLAF).

9

Three days prior to this mission, a high-level executive at a medium-sized business in Carmel, Indiana,

is requested to attend a 12:30pm meeting at her company’s national headquarters in St. Louis. Because

she has other work to complete that day, she cannot spend the four hours it would require to drive from

her office to the meeting, nor the similar amount of time it would require to drive back. She instructs her

secretary to arrange a private aircraft to take her to this meeting, bypassing the delays and inconvenience

of the highway and its traffic. Her secretary, knowing that she would prefer a flight on which she is

comfortable and relaxed, calls a charter operator in West Lafayette whom she knows flies one of Black

Tie Air’s aircraft.

The charter operator examines potential options for travel, and recommends that the aircraft pick the

executive up at Indianapolis Executive Airport (KTYQ), a 10-minute drive from her office, and bring

her to St. Louis Downtown Airport (KCPS), a 10-minute drive from the company’s headquarters. The

aircraft will wait at KCPS for the executive to return, at which point it will fly her back to KTYQ, where

she can resume her normal schedule. The secretary agrees, and confirms the itinerary.

On the day of the flight, maintenance technicians working for the charter operator arrive at 8am as part

of their normal work schedule. One of their first tasks is to prepare the aircraft for flight. They remove

any windshield or engine covers installed when the plane was last parked and fuel the aircraft. They also

perform a short maintenance check, verifying that no crucial component of the aircraft is unsuitable for

flight. At 9am, the pilot of the aircraft arrives, reviews the scheduled itinerary, and checks the weather,

seeing good flight conditions. They promptly complete all their required paperwork and make their way

to the aircraft, which is waiting on the apron. He preflights the aircraft and begins the power-up sequence,

finding himself ready to taxi at 9:30am. After receiving the all clear from his company, he taxis and takes

off at 9:40am, bound for KTYQ. He touches down at 10:20am, taxiing to the local FBO to meet his

passenger, shutting the engines down upon arrival. She arrives at 10:30am, as arranged, and boards the

aircraft, keeping her briefcase with her in the cabin.

After boarding, the pilot will conduct a brief safety briefing, explaining how to use the aircraft’s emergency

exits and similar safety equipment should they be necessary. He shuts the door and returns to the pilot’s

seat, where he restarts the engines and obtains taxi clearance, eventually taking off at 10:45am. He flies

the aircraft at its maximum cruising speed for the 200 nmi trip to KCPS, where he lands the aircraft at

11:55am. At the FBO, a company vehicle is waiting to drive the executive to her meeting: as soon as the

pilot shuts the engines off and opens the door, she exits the aircraft and meets her driver inside the FBO.

10

She is expected to return at 2pm for her return flight.

While the executive is away, the pilot completes the requisite tasks to turn the aircraft around. He

purchases fuel from the FBO, who fill the aircraft with enough for the return trip to Lafayette. He files

a new flight plan for the return trip, and has lunch at a restaurant near the airport. When the executive

returns, now with a large box of important files she was given at the meeting, he loads them into the

aircraft’s cargo hold, preflights the aircraft, and takes off at 2:10pm on the return trip to KTYQ. There,

he unloads the cargo, which is taken by the executive’s driver. He then promptly flies the final leg of the

day, from KTYQ back to the company base at KLAF, where he powers down the engines for the evening.

As he returns to his office, technicians push the plane back into the hangar to conduct routine checks and

storage.

During the standard operation of the aircraft, the pilot, in coordination with a host FBO, will be able

to meet the required support needs of the aircraft using equipment that is standard at all airports as of

2018. While there would be maintenance and support staff at the aircraft’s base, the only infrastructure

required for operation at other airports would be fuel available for sale. The pilot will handle the operation

of the aircraft, the loading and unloading of passengers, and the loading and unloading of cargo on their

own.

As we’ve established that our aircraft will be comparable in size to a Beechcraft Baron, we look to that

aircraft for information about passenger entry and storage. The Baron has a small cargo area towards

the rear of the aircraft, which is capable of storing luggage, and has a main cabin door with built-in

stairs. Both of these are standard features on aircraft of this size, and we can assume that our aircraft

will contain the same, or comparable, features.

11

4.4 Design Mission

The design mission for the aircraft (Figure 2) is considered with a 250 nmi minimum range between origin

and destination airports. Conceptually, the baseline route is from Westchester County Airport in White

Plains, New York (KHPN) to Dinwiddie County Airport in Petersburg, Virginia (KPTB). These airports

are 243 nmi apart, and thus represent a representative pairing of the aircraft’s threshold mission.

The higher range of 600 nmi is the target for the aircraft’s maximum performance. In this alternate case,

the aircraft will depart from Paris - Le Bourget Airport in Le Bourget, France (LFPB), and arrive at

Zagreb Pleso Airport in Zagreb, Croatia (LDZA), a distance of 586 nmi.

This design mission incorporates a 45 minute loiter following a missed approach, followed by a landing at

the target airport. This 45 minute loiter should be sufficient to cover the fuel requirement for a diversion

to another landing site, presuming there will not be significant loitering required at the diversion airport.

An additional constraint placed on this design mission is that the cruise-climb phase should be carried

out at the plane’s desired maximum cruise speed.

0 1

2 3

45

6 7

Segment Action

0-1 Start-Up , Taxi, TO1-2 Climb2-3 Cruise3-4 Zero-Range Decent4-5 Loiter5-6 Zero-Range Decent6-7 Landing and Taxi

Figure 2: Design Mission

12

4.5 Additional Markets for Consideration

In addition to the charter market, the requirements dictated by the primary market are also compatible

with several alternate markets. While none of these markets will dictate aircraft requirements, they will

expand the economic prospects of the aircraft system.

With the aircraft now fully sized, we can return to the Air Taxi market originally specified by the RFP.

While we maintain that we are unwilling to “bet the company” on the air taxi market, we could imagine

that some thin haul providers would be interested in a fast aircraft with a large interior cabin volume. In

the case of such a provider, however, the aircraft could be sold with interior furnishings of less luxury and

more space-efficiency, allowing the aircraft to carry more passengers. Because this market is very difficult

to predict, however, we will not anticipate sales to the sector during the design process.

The large cabin volume, included to increase comfort for executive passengers, also makes the aircraft

desirable to cargo and courier service. While specialized short-haul cargo aircraft will likely out-compete

our offering in most applications, it would be reasonable to anticipate selling a few airframes for the

purposes of time-sensitive bulk cargo. While we exclude this use from our economic analysis and maintain

our prediction of 30 aircraft per year, space in the fuselage for a large cargo or loading door should be

made available, if possible, to allow for future development of this application.

We anticipate additional applications which we do not yet foresee for this aircraft. Because of its large

cabin volume, it could be easily retrofit for medical transport, aerial photography, surveillance, and other

markets. These cases, however, are highly specific, and will account for only a small number of airframes,

and will be generally excluded from consideration during the design process. The existence of these

markets does, however, give further support to the argument that the expected production rate of 30

aircraft per year is conservative, and provides confidence that we will be able to meet and exceed our

break-even points for production.

13

5 Aircraft System Design Requirements

The AIAA design competition RFP specifies some initial requirements including certification to 14 CFR

Part 23; level 2, low speed aircraft. It specifies a sizing range greater than 250 nautical miles and an average

ground speed greater than 180 ktas. Our team has increased these requirements for the sizing range and

average ground speed and set additional flight performance requirements to remain more competitive in

our primary market. It is noted that if the target cruise altitude is achieved, the aircraft’s cabin will need

to be pressurized. Requirements for the cabin volume and wing loading have been set, as the team has

placed an emphasis on passenger comfort. The AIAA RFP also states the aircraft must meet single-engine

noise limits per Part 36 Sec. G36.301(c), even if multi-engined. For the weight of the aircraft this limit

would be 85 dBA [10]. Keeping passenger comfort in mind, our team would like to limit the noise level

as much as possible. The number of passenger seats for the main configuration of the aircraft has been

set to four to allow for a more luxurious and spacious cabin. An alternative configuration will have six

passenger seats with more of an economy style of seating that can be offered to air taxi services or private

individuals. Table 2 below displays the requirements matrix for the proposed aircraft.

Table 2: Requirements Matrix

Requirement Unit Threshold Target

Passenger seats 4/6 4/6Sizing range [n mi] 250 600Average ground speed [ktas] 200 250Cabin volume [ft3] 300 320Takeoff distance (over 50 ft obstacle) [ft] 2500 2500Landing distance (over 50 ft obstacle) [ft] 2500 2500Noise limit [dBA] 85 80Cruise altitude [ft] 12000 15000Climb rate [ft/min] 1700 1800Stall speed [kias] 75 75

14

6 Baseline Aircraft

Foremost, throughout the following section on Baseline Aircraft, it is important to note that Sections 4.2

and 5 should examined in conjuncture for all justifications not explicitly addressed here. Baseline Aircraft

are not indicative of all the attributes we desire in our product, nor should they be. Baseline Aircraft

server merely as a foundation from which to draw reasonably attainable attributes from.

6.1 Selection of Baseline Aircraft

Baseline aircraft are chosen that meet similar design requirements and are capable of being promoted in

the desired market of this report. In reference to Section 5, it is illustrated that while we have target

values for design metrics we have also outlined a broader range of acceptable values or Threshold values.

In order to be a practical baseline aircraft for us to base further design choices off of, these platforms need

to have a majority of attributes that fall around our Thresholds. For instance, a Cessna 172 meets only a

minority of our threshold values and is therefore excluded from our choices of Baseline Aircraft. On the

other end, we can similarly say an Airbus A380 likewise meets only a minority of threshold values and

thus, we are able to narrow our scope of consideration.

With a now narrowed scope of aircraft to investigate, it is also important to note that no particular

aircraft preexisting should meet all our demands. If this were the case, our basis for a proposal for a

new platform would be altogether unfounded. With this in mind, we have made the decision to draw

information from a bank of reasonably similar aircraft with significant investigation into two particular

platforms.

In tandem with Section 5, two systems were chosen. These systems represent high and low ends of our

thresholds. With each having some desirable traits, we can draw from them to make a system that

combines the best attributes into a single, new aircraft. The aircraft chosen for this purpose are the

Beechcraft Baron G58 and the Daher TBM 700C2.

6.2 Beechcraft Baron G58

The Beechcraft Baron G58 is a tried-and-true aircraft based on the long existing Baron 58. This platform

is notable for its short-haul services and use by private pilots. Beloved by many, this baseline aircraft

serves as our low performance metric for which to draw from.

15

Figure 3: Baron G58 in flightwww.flytechaviation.aero/uploads/multi-engine-rating.jpg

In essence, the G58 is a small twin piston engine aircraft. Referencing the table below, we can see this

platform’s most desirable traits for our proposal are exterior size and range. These specifications are the

values distinctly different from our other Baseline Aircraft and the ones which allow our system to remain

in the same scale of aircraft that our market typically sees.

As previously mentioned, the Baron serves as our low performance metric. Its size and limited range

make it suitable for standard hangers while remaining optimized for the intercity distance of our target

range. With a wingspan of 11.53 m and a length of 9.09 m, the Baron is poised at the upper end of sizing

in comparison to its current market competitors. [11]. Range is of important note. While Section 4 may

seem to indicate the Baron’s range is significantly extended over our requirements, this range represents

the maximum range. The maximum range of 2000 km is not indicative of its operational range [11, 12].

Truly, the Baron’s operational range at desirable speeds and payloads falls on the shorter threshold of

our requirements.

16

Table 3: Baron G58 Specifications [1]

Max. Range 2000 kmNormal Cruise 356 km/hrEconomy Cruise 304 km/hrStall Speed 139 km/hrEngine Type PistonEngines 2Seats 6Max. Payload 621 kgClimb Rate 527 m/minTakeoff Distance 621 mCeiling 6,300 mWingspan 11.53 mLength 9.09 mCabin Volume 5.2 m3

Wing Area 18.5 m2

Price $1,350,000Introduced 2005

6.3 Daher TBM 700C2

The Daher, or SOCATA, TBM 700 is a premier platform on the market today. Featuring a relatively

new design and high speed attributes, this aircraft serves as the high performance metric for our Baseline

Aircraft. It is known for its speed, comfortable size, and easily marketable aesthetics.

Figure 4: TBM 700C2 in flighten.wikipedia.org/wiki/SOCATA_TBM#/media/File:Daher-Socata_TBM_700_Air_to_Air.jpg

17

In reference to the table below, we can observe that the TBM 700’s most desirable traits are its speed

and interior size. At an operating cruising speed of 555 km/hr, the TBM 700 is primed to be a desirable

platform for those wanting to reach their destination in the shortest amount of time [12, 13]. Maximum

interior seating of eight and a cabin volume of 6.9 m3 also mean that the aircraft can be designed for less

passengers with more room [13]. Thus, the client not only reaches his or her destination quickly, but they

do it in roomy comfort.

Table 4: TBM 700C2 Specifications [1]

Max. Range 2900 kmNormal Cruise 555 km/hrEconomy Cruise 472 km/hrStall Speed 121 km/hrEngine Type TurbopropEngines 1Seats 8Max. Payload 794 kgClimb Rate 725 m/minTakeoff Distance 863 mCeiling 9450 mWingspan 12.68 mLength 10.65 mCabin Volume 6.9 m3

Wing Area 18.0 m2

Price $1,900,000Introduced 2002

6.4 Limitations of Baseline Aircraft

In conclusion to this overview on our Baseline Aircraft, it is again important to note that neither of

the aforementioned aircraft are the desired proposal of the report. In addition, each of these aircraft

alone would fail to meet the requirements set forth. However, they are not insignificant as they give us

contextual clues as to what can be feasibly produced. This provides us with a more targeted focus in our

further design process. Only through the adaptation of attributes will a system capable of meeting our

needs be created.

18

7 Technologies and Advanced Concepts

7.1 Hybrid Propulsion

Hybrid propulsion is an advanced technology that offers the possibility of improving efficiency and reducing

engine noise at the same time [14]. The advantages and disadvantages of this technology must be carefully

weighed before a decision can be made whether or not to integrate it into the aircraft. Hybrid systems

are typically considered in one of two configurations: parallel and series.

In the parallel configuration, an electric motor-generator is placed on the same power train as an internal

combustion engine. This internal combustion engine can be either piston-based or turbomachinery-based.

Power conditioning circuits connect the motor-generator to a battery. During takeoff and climb, the

battery is discharged as the electric motor works alongside the internal combustion engine to provide

additional power. Once the aircraft reaches its cruising altitude and speed, the electric motor is shut off,

and the internal combustion engine alone provides power for stable flight. During the descent phase of

the mission profile, the internal combustion engine can be deactivated, and the batteries can be charged

from the spinning of the propellers. This would provide some stored power in the event that a landing

needs to be diverted last-minute, and additional power is required for climbing. The advantage that this

system confers is that the internal combustion engine can be reduced in size compared to conventional

aircraft. This allows savings in fuel as well as in weight, although the savings in weight will be offset by

the additional weight of the hybrid system. It may also allow the aircraft to operate more quietly, which

would be an excellent selling point for higher-end markets concerned about minimizing engine noise.

In the series hybrid configuration, fuel is burned in an internal combustion engine, which is connected

only to a generator. The power from this generator is fed through power conditioning circuits to a

battery or supercapacitor. From the storage system, power is then fed to one or multiple electric motors.

This configuration allows a significant reduction in battery size, since only a few flight-minutes worth of

power needs to be stored to provide an instantaneous boost when required. By decoupling the internal

combustion engine from the propeller, the engine can always be run at whatever speed is most efficient for

power generation. It also allows for conventional fueling, eliminating concerns about battery charging time

or having to swap batteries between flights. However, there are some significant disadvantages inherent

to the series configuration. First, a significant portion of the energy stored in the aircrafts fuel will be lost

between being burned in the internal combustion engine and powering the propellers. Efficiency losses will

19

occur when the generator converts the mechanical power provided by the internal combustion engine into

electrical power, and the power conditioning circuits will also impose losses [15]. This configuration also

requires the inclusion of relatively heavy and expensive components, such as the generator and electric

motors, which contain large amounts of copper, a valuable material that only increases in cost with time

[16]. Considering that the series configuration will not yield significant savings in fuel, these costs cannot

be as easily offset as in the parallel configuration.

The AIAA RFP specifies that the aircraft must be capable of being introduced into service by 2025;

therefore, any technology incorporated into the aircraft must also meet this requirement. In 2016, the

National Academies of Sciences, Engineering and Medicine conducted a survey of the latest research into

electric aircraft propulsion. They assigned a turboelectric general aviation-sized hybrid aircraft concept a

time frame of N+1, which is a NASA nomenclature meaning the technology will achieve initial operational

capacity sometime between 2020 and 2025 [17]. Therefore, it should be possible to incorporate hybrid

technology into an aircraft of the size being considered within the time frame specified in the AIAA

RFP.

Until design parameters such as cruise altitude and climb rate are selected, a trade analysis cannot be

performed to directly compare a hybrid propulsion system to a conventional one. Therefore, to investigate

the merit of various hybrid systems, previous research in aircraft hybrid systems has been gathered. The

trend identified by other hybrid aircraft sizing attempts is that smaller aircraft have more to gain by

hybridization than larger aircraft. UAVs and ultralight aircraft have been shown in practice to achieve fuel

savings as high as 47% when hybridized. An analysis conducted on a single-aisle jet-propelled passenger

aircraft (Boeing 737-800) showed that, for a medium-range inter-city mission, fuel savings of 10% are

possible. The aircraft currently being considered for the AIAA RFP-specified mission falls between the

categories of ultra-light and single-aisle passenger jet, so fuel savings are expected to fall somewhere

between 10% and 40%.

When hybridizing, the degree of hybridization is another design parameter that must be selected in

addition to cruise speed and altitude. The degree of hybridization is defined as the ratio of electric power

to power provided by internal combustion while the aircraft is taking off and climbing [18]. This parameter

cannot be chosen until a model can be made to test which degree of hybridization would yield the highest

fuel savings with a minimum of added weight.

20

7.2 Composite Technology

Composite materials are an advanced technology that have been widely used in the aviation industry.

Over the next ten year the appreciable use of composites in general aviation is expected to change from

57 to 69 percent [19]. With such a significant portion of general aviation aircraft utilizing composites

already, the technology is already in service and therefore is not a concern for it being ready to use in

2025. However, it is important that the team weight the advantages and disadvantages of the use of

composites in our design.

Some of the advantages of composite materials include: weight reduction, flexibility, lower maintenance

and repair cost, and ability to design more complex shapes [20]. Weight reduction is a big player for larger

aircraft like the Boeing 787 but on a smaller aircraft it has a much smaller weight benefit. Flexibility

and ability to deign complex shapes is a big positive for a designer. Contrary to traditional materials like

aluminum composites can be modeled into almost any shape allowing for really aerodynamic planes.

The disadvantages of composite materials are it is difficult to detect internal structural damage, higher

cost, complex metal to composite joining, and complex fabrication. Delamination and cracks in composites

are mostly internal and hence require complicated inspection techniques for detection. As for cost, it will

continue to decrease as composites are more widely used and manufactured, but they are still more

expensive than traditional materials.

An aviation industry example of how composites are used in general aviation is Diamond Aircraft. The

DA62, DA40, DA42 all feature an all-carbon frame structure [21].

Figure 5: DA62 Composite Fuselage.www.diamondaircraft.com/aircraft/da62

21

8 Sizing Tools

8.1 Aircraft Database

A list of aircraft was compiled to form the database from which empirical fitting equations would be

generated. The breakdown is as follows.

Reciprocating Piston Engine

• American Champion Scout

• Diamond DA20(-C1)

• Diamond DA62

• Cirrus SR22 (G5)

• Mooney M20V Acclaim Ultra

• Mooney M20U Ovation Ultra

• Piper PA-32R-301T Saratoga II TC

• Piper M350

• Bonanza G36

• Baron G58

• Tecnam P2010

• Tecnam P2012

Turboprop

• KingAir C90GTx

• Piper M500

• Piper M600

• Epic E1000

• Pilatus PC-12 NG

• Pilatus Porter PC-6

• TBM 700C2

• Tecnam P2006T

• Piaggio Avanti Evo

• Quest Kodiak

• Cessna 208B Grand Caravan

• Vulcanair A-Viator

Parameters Recorded

• Year introduced

• MTOW (W0)

• Empty Weight (We)

• Maximum occupancy

• Primary construction material

• Landing gear type (fixed/retractable)

• Engine number, type, and model

• Combined engine power

• Power loading(W0S

)• Wingspan (b)

• Chord (c)

• Aspect ratio

• Wing planform area

• Wing loading

• Takeoff distance (over 15 m obstacle)

• Max. rate of climb (S/L)

• Ceiling

• Max. speed 2

• Cruise speed

• Range

• Landing distance (over 15 m obstacle)

• Typical Price

• Autopilot, Radar, other notable features

2Taken as never-exceed speed VNE when published. Otherwise, the maximum speed listed was used.

22

Currently, the empty weight fraction predictor being used is that from Raymer Table 6.3.

We

W0= a + bWC1

0 ARC2

(P

W0

)C3(W0

S

)C4

V C5max (1)

Input units: Weight 3 [kg], power-to-weight [kW/N], wing loading [N/m2], and velocity [m/s]. It should

be noted that the signs on the exponents must match the observed historical trends in order for this

model to produce any physically meaningful results. For example, the variables b, C2, C3, and C5 should

be positive, while C1 and C4 should be negative.

When the database entries for piston-engine aircraft of aluminum construction were compared, the above

fitting equation regression results had an R2 = 0.838, with the specific constants listed below.

Table 5: Parameters for piston aluminum aircraft from the regression from Eq. 1.

a -2.0957b 2.2142C1 -0.049311C2 0.029035C3 0.056948C4 -0.025104C5 0.1497

3We understand that weight and mass are not synonymous, but unfortunately society treats them as such. Thus, theweight (force) is the force felt by a mass experiencing a standard 1-g sea-level gravitational acceleration.

23

Appendix: MATLAB Code4

%% Sizing Regressionglobal GRAV; GRAV = 9.81; % gravitational acceleration, m/sˆ2database_file = '../aircraft_database4.xlsx';

% Piston Engines[data_P,alum_P,engines_P] = readExcel(database_file,1);exclude = ˜alum_P; % include only aluminum construction

guess = [-0.5, 1.2, -0.15, 0.08, 0.05, -0.05, 0.20];[a, b, C, mdl_Piston_al] = sizingParameters(data_P, guess, exclude)

% Written by Nick Turo-Shields, 30 Jan 2019. Modified 5 Feb 2019.function [a, b, C, mdl] = sizingParameters(data, guess, exclude)

%sizingParameters Estimate We/W0 from aircraft database% Utilizes the empirical equation in Table 6.2 of Raymer and fits% coefficients to the equation.global GRAV

% parse individual variablesWe = data(:,3);W0 = data(:,2);AR = data(:,16);powerload = data(:,13);wingload = data(:,18);V_max = data(:,22); % km/hrV_max = convvel(V_max, 'km/h','m/s');

We_W0 = We ./ W0;wingload = GRAV * wingload; % convert kg/mˆ2 to N/mˆ2P_W = GRAV ./ powerload; % invert and convert to mass to force (kg -> N)tbl = table(W0, AR, P_W, wingload, V_max, We_W0);

modelfun = @(d,x) d(1) + d(2) * x(:,1).ˆd(3) .* x(:,2).ˆd(4)....* x(:,3).ˆd(5) .* x(:,4).ˆd(6) .* x(:,5).ˆd(7);

opts = statset('MaxIter',600,'TolFun');mdl = fitnlm(tbl,modelfun, guess,'Exclude',exclude,'Options',opts);d = mdl.Coefficients.Estimate;a = d(1); b = d(2); C = d(3:end)';

if any([b, C(2:3), C(5)] < 0) || any([C(1), C(4)] > 0)warning('The coefficients might not be physically meaningful.');

endend

function [nums,alum,engines] = readExcel(file,page)%readExcel Extracts numbers from Excel file and material/engines% Reads numeric data from Excel database and returns vectors% of the construction material and number of engines[nums,txt] = xlsread(file, page);alum = strcmp(txt(3:end,8), 'Al')';engines = nums(3:end,10)';

end

4The MATLAB code utilizes the Statistics and Machine Learning Toolbox and Aerospace Toolbox

24

References

[1] Jane’s All the World’s Aircraft.

[2] ImagineAir, Jul 2018. URL en.wikipedia.org/wiki/ImagineAir.

[3] SATSair, May 2015. URL en.wikipedia.org/wiki/SATSair.

[4] Hopscotch Air. URL flyhopscotch.com.

[5] Jim Moore. Cape Air Begins Tecnam Transition, Sep 2017. URL www.aopa.org/news-and-

media/all-news/2017/september/27/cape-air-begins-tecnam-transition.

[6] Kevin Rossignon. “Market Analysis of the Private Jet Charter Industry”, 2009. URL

www.paramountbusinessjets.com/downloads/AviationWritingCompetition2009/

MarketAnalysisOfPrivateJetCharterIndustry.pdf.

[7] “The Smarter Way to Own”, 2019. URL www.netjets.com/en-us/how-fractional-jet-

ownership-works.

[8] Utah Air FAQs, 2015. URL www.flyutahair.com/faqs.

[9] E. Bruce Goldstein. “Cognitive Psychology: Connecting Mind, Research, and Everyday Experience”.

Cengage Learning, 2015.

[10] FAR Part 36: “Noise Standards: Aircraft Type and Airworthiness Certification”. Washington, DC:

Federal Aviation Administration, 2002.

[11] “Beechcraft Baron G58: Easy Twin Transition”. URL www.beechcraft.txtav.com/en/

baron-g58.

[12] “Socata TBM 700A Specifications”. URL www.globalair.com/aircraft-for-sale/

Specifications?specid=156.

[13] SOCATA SAS. “Daher TBM 700 Version C Pilot’s Information Manual”, Oct 2014.

[14] Joachim Schomann. “Hybrid-Electric Propulsion Systems for Small Unmanned Aircraft”. PhD thesis,

Technische Universitat Munchen, 2014.

25

[15] Josef Kallo, Johannes Schirmer, Steffen Flade, Steffen Poggel, Thomas Stephan, and Caroline Willich.

“High Efficient Energy System for Electric Passenger Aircraft Propulsion”. In AIAA Scitech 2019

Forum, page 1672, 2019.

[16] John E Tilton and Gustavo Lagos. “Assessing the Long-Run Availability of Copper”. Resources

Policy, 32(1-2):19–23, 2007.

[17] “Commercial Aircraft Propulsion and Energy Systems Research: Reducing Global Carbon Emis-

sions”. National Academies of Sciences, Engineering, and Medicine, 2016.

[18] Christian Friedrich and Paul A Robertson. “Hybrid-Electric Propulsion for Aircraft”. Journal of

Aircraft, 52(1):176–189, 2014.

[19] Chris Red. “Aviation Outlook: Composite Aerostructures in General Aviation”, Jun

2008. URL www.compositesworld.com/articles/aviation-outlook-composite-

aerostructures-in-general-aviation.

[20] Sarina Houston. “Advantages and Disadvantages of Composite Materials on Airplanes”. URL www.

thebalancecareers.com/composite-materials-aircraft-structure-282777.

[21] Diamond Aircraft. URL www.diamondaircraft.com.

26