Momentum - October 2020 - 13

Student Generation
even if the destination changes. Better yet, the team
can accurately predict the end time using past and
present data from the ongoing development
progress. The rover equipped with sensors is
representative of Agile product development. Texas
A&M has fully adopted Agile principles within the
Scrum framework to consistently meet deadlines and
deliver meaningful products. The result is a selfmotivated, well informed, and increasingly productive
team. Moreover, multiple aircraft designs are explored
throughout an SAE season, which helps the product
converge to a well-balanced configuration.
For SAE Aero Design at Texas A&M, two Scrum
teams were formed and overseen by a chief engineer
and director. The chief engineer is responsible for
monitoring the system and ensuring each component
of the aircraft is compatible with the others. The
director takes care of logistics, team organization,
and administrative duties while guiding the business
division. Within the two scrum teams, there is a
product owner, development team, and design lead.
The product owner sets expectations, reviews work,
and manages coming deadlines throughout each
"sprint," or work period. The development team,
made of numerous members, breaks down the
sprint's assignments and delivers designs for multiple
"products." A product may be specifications on a
vertical tail or the front landing gear structure. Unique
to A&M is the design lead. In industry, members of a
scrum team come and go slowly, one at a time, and
are skilled in their field. However, college students are
still developing their knowledge, and SAE is often
their first design experience. Because of this, the
design lead provides guidance on calculations and
decision making, drawing on their past experiences
with the team.
Immediately after instituting agile management,
Texas A&M saw tangible benefits. Engineers and
managers alike know most problems, big or small,
can be avoided with better communication. Within
Scrum, the design engineers hold most control-the
product owner just guides their direction-so
everyone must work together and remain on the
same page. In past systems, they all looked to one
person who assigned tasks, but now they look to
each other. That sense of ownership translates to a
genuine interest in the success of their project, and
prompts both introverts and extroverts to
communicate as they work. To facilitate those
conversations, and maximize their team-wide benefit,
a daily standup is held so everyone can answer three
simple questions: what have I done, what am I going
to do, what is impeding my progress. In engineering
terms, the daily standups increase the sampling rate,
so more relevant and frequent corrective inputs can
be added. The system becomes stable, and less

MOMENTUM

SAE Aero Design 2020 rules mandated a short, 100-foot takeoff distance.

Punching above its weight
New for the SAE Aero Design 2019-2020 season, Regular Class, was
a ruleset that required takeoff within 100 feet and a flight score
equation that, among other things, penalized wingspan and
rewarded cargo weight. This twist meant a large wingspan was not
necessarily the most efficient configuration. Texas A&M opted for a
wing roughly half the specified limit of 120 inches, one of the smallest
among all competitors.
The decision for the small wingspan was driven by the short 100foot takeoff requirement and the benefits of a high takeoff velocity.
Newton's second law states the acceleration of an object is equal to
force divided by mass. The aging 1,000-watt power limit meant
teams had optimized the thrust force in the past, so minimizing drag
and weight would provide the competitive advantage A&M needed.
For reference, a competitive plane with a 60-inch wingspan would
have to carry half the weight of a 120-inch plane to score 25 points.
Therefore, a small plane can be much lighter and reach a higher
velocity at 100 feet. This is significant because the modern lift
equation states that lift is dependent on velocity squared. A small
increase in speed can result in a large increase in lift, and ultimately
payload-the key flight score factor.
Maximizing the lift from a small wing was the most challenging
task. Verified in XFLR, STAR CCM+, and a low-speed wind tunnel,
Texas A&M employed a multi-element flap design to make full use of
the high velocity, generating more lift and less drag than the
competition-standard S1223. Additionally, a swept trailing edge
minimized wingtip vortices, and a refined winglet design increased
lift by 10%. A blended fuselage-wing took advantage of the
fuselage's planform area, which constituted 24% of the available
wing area. The result was a low aspect ratio wing with a moderate
efficiency but high lift value, prioritizing the score benefits of a small
wingspan dimension and heavy payload.
Though unconventional, the A&M team's plane took 6th place in
the Technical Design Report Event at SAE Aero Design East 2020,
with full credit to the small and lightweight design. n
By John Blausen

October 2020 13

Momentum - October 2020

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