Being just south of University of Colorado - Boulder, Arvada Associated Modelers is greatly involved in the Aerospace Engineering Sciences program helping students design and test their new aerospace creations.
|Hyperion||Hyperion is a research project with on-going phases of development and experimentation of unique blended body/wing designs conceived by the graduate students at CU.|
Read about what CU AES has been up to and how they need help below.
By: Joe Pirozzoli
The 2018 DBF fly-off was completed last weekend (Apr 19-22) in Wichita, KS. Two (2) Colorado teams competed and finished very, very well – University of Colorado (CU) and the CO School of Mines (CSM). Both teams completed all required missions and both were in the top 25 out of 90! CU finished 13th and CSM finished 22nd!
One of the biggest accomplishments you can achieve, beyond just showing up and competing (because that in-and-of itself can be a daunting task when you have to travel half way around the world), is completing all the required missions. And, that does not guarantee you a top 10 finish. I estimate that less than 20% of all 90 teams completed all required missions (1-ground + 3-flight). Many, many teams never even got off the ground. When you see some of the contraptions that showed up at DBF, you wonder… what were they thinking? Nevertheless, you have to remember that this competition is about innovation and thinking outside the box.
DBF is sort of like a fun fly, except the scoring is very complex and specific to each of the missions. There is a little luck involved, there are timed events, and a duration event with heavier payload. DBF challenges teams to come up with a design that will be versatile enough for the entire rigor of the fly-off. For the ground event, teams rolled diced to determine the challenges. Among the challenges were removing/replacing the Rx, removing/replacing the rudder, prop, etc. A score was awarded only if you were able to do these tasks within the allotted time. The first flying mission was an empty plane for 3 laps around the field within 5 minutes (piece of cake). The second flying mission was with passengers (i.e. rubber “bouncy” balls). The teams would choose the number of balls, but the size varied, again, by a roll of the dice. Then fly the same 3 laps in the shortest amount of time, without any balls coming loose from their restraints in the fuselage. The third and last mission was flown with passengers and payload (i.e. extra weight), the heavier the better. Then fly as many laps as you can within a maximum limit of 10 minutes. All flying missions had to end with a successful landing on the runway. Cessna’s runway is several thousand feet long, but only about 35 feet wide. Planes were also weighed after each flying mission to help determine the final score. Extra attempts at missions 2 and 3 were allowed to improve scores, but not many teams would be in a position to complete 3 missions let alone any extra attempts.
I found out later that some teams had their own goals. For instance, I was informed that Stanford’s goal was to win missions 2 and 3 by carrying the most passengers and payload for the longest time. The geometry of their plane (i.e. long wingspan and heavy weight) eliminated them from winning DBF. There was no doubt in my mind that there was a contest within a contest going on! However, it was also obvious that in order to contend to win DBF, you had to have a very light plane with short wingspan. Thus, some very small planes were built. So small, was the plane from Clarkson University, that I could not see it at the far ends of each lap (500’ north and south of center field). Simply put, I could not have flown that plane because my eyes are not good enough anymore. USC’s pilot admitted to the same affliction flying their tiny plane (i.e. less than 11” span). Small planes in low visibility are a bad combination! That proved to be an added challenge for the test pilots at DBF this year.
As usual, the weather in Wichita was abominable. All 3 flying days (Friday – Sunday) were plagued with high winds (gusting to 35 mph), chilly temps and a full day of rain on Saturday. I do not remember ever seeing the sun. There was only 1 day when the wind wasn’t a crosswind. It’s bad enough dealing with the wind when you have good flying airplane. When you combine experimental design, marginal power, dicey construction and a substantial lack of practical experience… crappy flying conditions are the last thing any pilot wants to deal with. Despite that, however, the test pilots were able (in many cases) to “make a silk purse out of a sow’s ear!”
As I mentioned in the previous update, CU’s plane was the 3rd generation, and many things improved along the way including construction quality and precision. CSM’s plane was a bit more crude, but more conventional in design, so it ended up being the easier plane to fly. Also, based on the aforementioned, less competitive in terms of mission scoring due to its size, but a success design nonetheless. CSM had not asked for help from either Dan, myself or AAM prior to the competition. A situation I hope to rectify in the future. However, I did end up flying for both teams even though CSM already had a student pilot. He was inexperienced and had never flown is high wind or attempted a crosswind landing. As it would turn out, I not only flew for CU and CSM, but also for UCLA, Cornell (for the 2nd time in 2 years), Rutgers, Notre Dame and a university from Istanbul, Turkey. Needless to say, I was a busy test pilot.
CSM had a rough start. On their way out of town, Thursday morning at 3 am, they hit a deer on Hwy 58. No one was injured (except the deer), but it caused them to miss tech inspection that day, which cascaded into missing their first flight que (i.e. opportunity to fly) on Friday. Missing flight ques is a bad thing because you don’t get another chance until all other teams have gone through the que, and that takes a lot of time when there are 90 teams competing. The flight order is set based on your report score. CSM and CU were 4th and 7th, respectively, with their reports. Anything in the top 10 is impressive and both schools have historically done very well. This is particularly impressive for CSM despite the obvious disadvantage of NOT having an aero-engineering program.
CU did get their tech inspection on Thursday and we flew a successful 1st mission early Friday morning when the winds were calmer. Thus, CSM was immediately behind the 8-ball to get in all required missions over the weekend. Plus, there was a new wrinkle this year. The ground mission had to be opted for in place of a flight mission. That rule ended being changed on Saturday during the rain delay, but it still impacted CSM negatively because they opted to do the ground mission late Friday afternoon instead of flying when they came up in the que for the 2nd time. They did that partly because of severe crosswind conditions. The thinking (at the time) was that they’d still get in 3 flights attempts between Saturday and Sunday. So after Friday, CU had successfully completed its ground and 1st flying missions while CSM had only completed its ground mission.
Then the rain came early Saturday morning. As they did 2 years earlier, the organizers tried to wait out the rain based on the promise of improved conditions (by mid-morning) in the forecast. However, the weather never broke and it rained all day. It was a cold, wet, windy, miserable day! And, not only did we lose 2 ½ hours in the morning, but they suspended flying 2 hours early at the end of the day. Thus, they barely got through the flight order 1 complete revolution. Both CU and CSM flew successfully, but only the 1 time. So after Saturday, CU was sitting comfortably with 1 mission remaining and CSM nervous about getting 2 flight missions in on Sunday.
The rain departed on Sunday, but the wind remained. Fortunately, it was due north and right down the runway. Unfortunately, it was 15-20 gusting to 20-30 mph and, at times, very bumpy. CU was busy strategizing how to fly based on the prospect of a possible 2nd attempt at mission 3. Meanwhile, CSM was crossing their fingers that they’d get the 2 chances needed to complete all 3 missions. With CSM and CU both early in the order (at 4th and 7th), their prospects for 2 flights each were pretty good, but not guaranteed. CSM came up (for the 1st time) and flew a successful mission 2. Now it was CU’s turn. A successful mission 3 would be the best result for CU in many years and everyone was excited. Mission 3 was all about duration. Their strategy was to complete 3 laps on this attempt. Then, if a 2nd attempt could be made, run the plane out of batteries (for as many laps as possible) and hope to get back to the runway. The 3 laps were easily completed, but I just missed the runway on the landing, DQ’ing the attempt. A nasty gust pushed the plane to the edge of the runway and it bounced off. It was a crushing outcome, and to add insult to injury, the plane sustained minor damage.
Fortunately, repairs were not going to be the issue. The team would have ample time to repair/replace broken parts. The question was whether CU would get another chance to complete mission 3. CU now found itself in the same boat as CSM… hoping for the flight order to circle around 1 more time to provide another attempt at mission 3. The first flights for both teams had occurred shortly before noon. Therefore, the flight order needed to circle all the way around in just under 5 hours (i.e. before the 5 pm deadline). On the plus side, there is a lot of attrition by Sunday afternoon (i.e. many teams have crashed out). Very few actually thrown in the towel. However, many would miss their que by not having repairs completed in time to fly. So the waiting game began.
The one thing we knew for sure was that all the top teams (i.e. everyone ahead of CU and CSM) would be ready to take their turns at either mission 3 or for an extra attempt (at missions 2 or 3). Also on the negative side, many teams would be attempting mission 3, which meant up to 10 minutes per flight. As was the case with Notre Dame at #80. I flew for them late in the afternoon (around 4:30 pm). They wanted me to fly 8 minutes, and then more if I thought the batteries would hold up. However, after 4 laps the batteries felt very weak and the team agreed to let me land. Subliminally, I may have been in a hurry to get them down as valuable minutes were ticking away from CU and CSM, but honestly, I just did not want to wreck their plane. From #81 on up, there were very few teams left in the que and we knew, for sure, CSM would get another attempt. CSM opted for a 1-lap mission 3 because addition laps simply would not improve their score. In fact, Virginia Tech, at #30 in the que and who was destined to finish 2nd overall, elected to do the exact same thing. Additional laps would not have significantly improved their score, but completing mission 3 was crucial.
So it was, about 4:45 pm CSM came up. I completed 1 lap and put it right on the centerline. Mission 3 complete and a top 25 finish. CU came up at about 4:50 pm, same plan, same result, 1 successful lap, a perfect landing, and 13th place. As it would turn out, UCLA also got 1 more chance as they were right behind CU at #8. We were still trying to complete mission 1 and came up just short. On the landing, the plane tipped over on its narrow gear and the wing came off its mount, DQ’ing the flight. Cornell came up right behind UCLA at #9, but they didn’t get to go… it was 5:02 pm and the 2018 DBF fly-off was over.
I was utterly and completely humbled (and exhausted) this past weekend by several things. First, the incredible enthusiasm, shear tenacity and unwavering determination of the all the teams, but in particular UCLA. Their 2nd to last flight ended in a complete wreck after the motor quit down wind. Yet, they managed to put it all back together for the final try. They could have easily cashed in their chips, but they just wouldn’t quit!
Next, this challenged my flying skill and emotional courage to the utmost. Every plane and every situation presented a new challenge and any slight lapse in concentration could end in disaster, and it did on a couple occasions. Granted, most planes were poorly built, underpowered and pushed boundaries. In addition, the conditions were truly miserable. However, the sense of despair I felt after an unsuccessful flight was truly monumental. All the hopes and optimism of a dozen students (after months of sweat and hard work) rests on your shoulders. And, if you fail, those hopes are dashed in an instant. It is tough to shake that off. You want to quit, but you cannot because they refuse to. And, they never place blame or show frustration. They just want to keep trying. I guess that is why I enjoy this so much. You just can’t buy that kind of spirit anywhere!
Below are pictures from the event. Needless to say… these 2 teams went home very happy and satisfied.
University of Colorado
Colorado School of Mines
Map of DBF Teams/Reports
Scores were projected in real time (top 45 shown)
The “Essence” of DBF
Georgia Tech – 3rd Place
Stanford – Built for passengers and heavy payload
USC – Top Contender (but didn’t finish M-3)
MIT – Winner “Weirdest Design”
USC T-Shirt – They are “in it to win it!”
The two above equals this (I don’t believe this ever flew)
This actually flew (but not very well)
Beautiful craftsmanship by Team Lederhosen (Austria)
This was mostly carbon fiber and very tiny
Turkey’s all carbon fiber entry – the elevator failed
Virginia Tech – 2nd Place (the Tech’s have it)
UCLA (before crash) – It flew well, but underpowered
Notre Dame – large, conventional and easy to fly
Homework – always beckoning
Sleep – get it when you can!
The Insanity inside the hanger
“Fly Like an Egyptian”
Does this look like fun to you?
Arial view of field/flight pattern (North =>)
I wanted to provide just a brief update about the 2018 project and the going’s on. First, what is Design-Build Fly (DBF)? DBF is an annual competition for university students whereby they will design, fabricate, and demonstrate the flight capabilities of an unmanned, electric powered, radio controlled aircraft that can best meet a specified mission profile. The mission profile changes each year, the goal of which is… “balanced design possessing good demonstrated flight handling qualities and practical and affordable manufacturing requirements while providing a high vehicle performance”. The competition also requires a detailed proposal (i.e. report) which is a significant part of the competition score.
The competition is put on by the American Institute of Aeronautics and Astronautics (AIAA) and sponsored by (among others) Textron Aviation, Raytheon Missile Systems, and the AIAA Foundation. The competition is held, biannually, in Wichita, KS and Tucson, AZ. This year, as in 2016, we’ll be going to Wichita April 19-22. Learn more about DBF here: http://www.aiaadbf.org/Rules/
CU has perennially participated in this event and is both well staffed and funded. I am told that every student in AES (at CU) will, at some point in their academic career, participate in DBF. The faculty advisor for CU DBF is Dr. Donna Gerren. We have assisted other teams in the past from CO School of Mines, North Dakota State University, and Cornell University. I flew for Cornell in 2016 who finished in 8th place that year.
This year’s CU team has been very exciting and fun to work with. As usual, these very talented and bright students have many great ideas for their vehicle design and are willing to try anything. They also show a very significant commitment to this project despite their rather heavy academic work-load. Dan Underkofler and myself have spent numerous hours going over designs, construction techniques (for models) and flight testing. This is the first time that we have had 3 prototypes with which to improve the design, construction and flight characteristics of the vehicle. I’m amazed at how their building skill and proficiency has improved with each new prototype.
They now have prototypes #2 and #3 which have demonstrated flight and could be used in competition. The latest version #3 was flown last weekend (4/7), with great success, and with multiple power and payload configurations.
I have the pleasure of being the primary, designated pilot as Dan will be unavailable the weekend of the competition. Thus, we are in the final planning stages. I will meet the team in Wichita on Friday (4/20) morning for a mandatory pilot’s meeting. 3 missions will be completed Friday through Sunday, with the winner being announced Sunday evening.
Attached are pictures of prototype #3. This model is only about 24” long with a wing-span about the same dimension. It is powered by either a 7 or 8 cell Nicad battery. It is made with numerous composite materials and many parts were fabricated with a 3D-printer. If you look closely, you will also see “laser-cut” balsa and ply components and the gear is machined aluminum. These guys have all the toys at their disposal!!!
Speed will be part of the competition, but we have struggled with stability at full throttle. Nevertheless, it does have a fairly wide flight envelope, will fly very fast, and is manageable to take off and land. We are able to complete a “lap” which consists of 500’ upwind pass, 1000’ downwind pass including 360 degree circle back at center, then 500’ back upwind in about 30 seconds. One mission will be to complete as many laps as possible within 10 minutes, with a successful landing.
Wish us luck,
Joe Pirozzoli & Dan Underkofler
The Arvada Associated Modelers (AAM) has, for many years, made efforts to give back to the community. In 2014, this effort was furthered by moves to actively support local University aviation-related projects. The club created an “Education Coordinator” position, with a primary duty to support and enable university groups. This year, AAM supported the Colorado School of Mines (CSM) and University of Colorado (CU) student teams in their efforts with an international Design, Build, Fly (DBF) competition.
DBF is an annual competition where student teams from around the world create model, radio control, aircraft to meet a set of given criteria and to complete designated “missions”. Teams are typically clubs, extracurricular, and supported with limited university funding.
The missions this year required the students to design two aircraft:
- The “Production Aircraft”, which was to carry a payload of a 32oz bottle of Gatorade™.
- The “Manufacturing Support Aircraft”, which is designed to carry the Production Airplane internally.
Rules and criteria favored, limited, or specified: batteries, weight, and number of pieces the production aircraft dis-assembled into.
The 2016 Design/Build/Fly Competition Flyoff was held in Wichita, KS, April 15-17, 2016. The event is organized and put on by the American Institute of Aeronautics and Astronautics (AIAA) and is sponsored by the AIAA Foundation, Cessna and Raytheon. This was the 20th anniversary year since the original competition. A total of 145 entries were received, 93 teams were selected for the next phase, and 69 teams attended the Flyoff (25 international). Over 625 students, faculty, and guests were present.
The CSM team approached AAM in order to utilize AAM’s flying facility. The team consisted entirely of Mechanical Engineering students and had a talented student pilot. We arranged access to the AAM field as requested, where they performed numerous test flights.
The CU team not only needed a testing facility, but needed help flying their designs. AAM members/pilots Dan Underkofler and Joe Pirozzoli volunteered to assist. Test flights were scheduled around weather and personal schedules and were, to say the least, not entirely satisfactory. Nevertheless, Dan generously volunteered to take the planes, support equipment, and several students in his motorhome to the Kansas competition.
Dan and Joe also had the opportunity to support other DBF Teams including North Dakota State, Cornell University, and PES University (India). With their assistance, Cornell finished impressively in 8th place.
While neither CSM nor CU were in the hunt for victory, both teams were satisfied with the success they did have. What impressed us the most was the time, effort, and perseverance that the teams displayed in the face of all the obstacles encountered that weekend. We are excited about being involved with DBF next year and hope to be involved earlier in the project to lend advice in addition to facilities and piloting expertise.
AAM Education & Research Coordinator
On Monday February 9, a group from Colorado University’s Research and Engineering Center for Unmanned Vehicles, which is part of CU Boulder’s Aerospace Engineering Sciences department test flew a RC Pilatus. They plan to take the plane to Alaska to do an artic environmental survey and had concerns about carburetor freezing in the cold so they had converted it from gas to electric. They flew several laps, then flew a preprogramed pattern on auto-pilot, and had a smooth landing for a successful test flight.
James Mack is the pilot and an AAM member; Doug Weibel is a graduate research assistant; Tevis Nichols is a graduate research assistant; Gijs de Boer is with the Cooperative Institute for Research in Environmental Sciences which is a joint institute between NOAA and CU; and Brian Argrow is a professor at Aerospace Engineering Sciences.
Fall 2012 – Spring 2013 — A collaboration between Arvada Associated Modelers and the University of Colorado, Aerospace Engineering Sciences Department
Joe Pirozzoli, a long-standing member of AAM, reports:
Hyperion is a research project consisting of multiple, on-going phases of development and experimentation involving many disciplines of aeronautical and aerospace engineering. The face of Hyperion is the vehicle itself which is a unique design and “proof of concept” blended body/wing conceived by the graduate students at CU, and funded in large part, by the Boeing Corporation. The Blended Wing Body Design of the Hyperion was based off of the Boeing X-48 Unmanned Aerial Vehicle. The Hyperion vehicle was constructed almost entirely from composite materials including extensive use of carbon fiber. The current design of the Hyperion aircraft was conceived in the second year of the Hyperion Project at CU, which began in Fall 2011-2012.
The current design combined the first year’s center-body, which was made partly at the University of Stuttgart, Germany and partly by CU Graduate Students (which has been previously documented), with a new set of “swept” wings. The new swept wings, unlike the wings of the first year, complied with the defined specifications of Boeing’s Blended Wing Body Design. In addition to the new design, the aircraft was now also equipped with a newly designed and custom machined set of main landing gear struts including a braking system that was incorporated for the rear, main wheels.
Hyperion was a true experiment because of all the uncertainties and questions about its design. Questions included, was it too heavy, would it be underpowered, exactly where was the center of gravity (CG), and how much control surface deflection would be required. It seemed that there were more unknowns than knowns. However, working through these unknowns with a group of extremely bright, enthusiastic, and creative individuals turned out to be half the fun and challenge. There were many frustrations along the way, but in the end, it was pure exhilaration.
Hyperion would also be a surrogate of sorts for me to collaborate with intelligent, young, prospective scientists who are very much akin to my oldest son Tony. Tony is currently enrolled at the University of Nebraska and on his way to getting a Masters degree in theoretical physics. Admittedly, I am often baffled by the work he is doing, but I never tire of trying to understand what new things science is uncovering or researching. “Hanging out” with the graduate students at CU seemed to bridge the distance from my son.
Hyperion also consisted of many other subsystems and components that were designed and being tested. Everything “Hyperion” was somewhat experimental, but also meticulously designed, tested, monitored and evaluated. I attended 2 presentations by the students to their professors and it was clear that every aspect of Hyperion was under intense scrutiny. There was very little about Hyperion that wasn’t being “graded” except for the RC systems.
Myself and Stewart Garret got involved in Hyperion back in late October 2012. Dr. Jean Koster, a professor at the University of Colorado, was looking for experienced pilots to fly their SIG Rascal 110 with “Hybrid-Electric” engines. Many others from AAM would also become involved in the project as it progressed and I am truly proud and grateful to everyone (who are too many to name) that supported and helped. AAM truly put its best foot forward and demonstrated once again, its commitment to community outreach.
AAM provided the “RC” experience and knowledge base to bring Hyperion to life. AAM’s expansive runway was also a great asset to the project. It was really the only suitable site (in the Denver area) for testing this vehicle short of a full scale runway. Due to the high cost and time involved with constructing the vehicle itself, the Hyperion team had decided not to experiment with new or untested RC systems and components. They instead used well known and fully proven RC equipment. Our job was to make sure that the RC systems and components, including the competence to fly the vehicle, were the least of their concerns. Despite all this, flying Hyperion would prove to be quite challenging and require all of my experience and skill as an RC pilot.
The success of Hyperion would lie less in the accomplishment of achieving flight, but rather more in what these students would learn about the processes of project development and management. Hyperion would also provide the valuable “hands-on” experience that fresh-faced, graduate engineers are often criticized for not having. I could have only have imagined such an opportunity as an undergraduate engineering student. Hyperion was well beyond anything one could learn in a classroom.
Rascal fights in the latter months of 2012 consisted of testing two, not so unique, engines: an OS 120 4-stroke, and a Plettenberg Terminator electric out-runner (11 HP), powered by 12S lipo battery system. Eventually, the students would combine these prime movers to create an integrated IC/electric hybrid system which has yet to be fully tested and flown. The work on the Rascal would eventually lead to test flights of both a ½ scale Hyperion prototype and then the actual, full scale Hyperion.
Flight testing of the ½ scale prototypes and early taxi testing of the full scale Hyperion would prove to be extremely challenging. One of our greatest challenges was scheduling testing when the runway was clear of snow. Much of the testing was attempted from late-February through mid-April when it seemed as though a major snow storm was expected almost weekly. I would like to thank my good friend Lanny Hansen for always being ready to assist with plowing and clearing the runway using the Club’s trusty tractor.
Fight readiness and testing of Hyperion would begin in earnest in early March 2013. It began with the full integration of all the RC flight systems with the other components and subsystems including telemetry and monitoring. The students also created a flight simulator specifically for Hyperion that turned out to be quite accurate and useful. Systems integration, ground checks and flying on the simulator would lead to a series of high speed taxi tests and eventually, hopefully, a series of successful flights.
I was invited to assist with a series of flight readiness reviews and check-outs some of which took place on the CU campus. One purpose of these reviews was to assure that the RC systems were functioning and set up correctly. This included aspects of both performance and safety. These students were not well versed with transmitter programing, servo/control surface setup, ESC programming, etc. Despite their lack of experience they did an excellent job of construction and preliminary setup.
The flight readiness reviews included a couple of presentations by the students to their professor’s. These presentations shed quite a bit of light on all of the other aspects and goals of Hyperion. It was during these presentations that I learned that Hyperion’s success did not depend absolutely on a successful flight. Further, their mentors were not rushing toward that conclusion. I was also surprised at how much they valued and relied on my experience simply as an RC pilot. I felt very welcomed and appreciated during those meetings which exemplified the integrity of the project and the Hyperion program.
For anyone that was present when the Hyperion team arrived at the field, it may have appeared that things were somewhat disorganized and chaotic. Their activities were actually well practiced and choreographed. Unfortunately, there always seemed to be something that needed repair or added attention prior to each taxi/flight attempt, a situation all of us can relate to at some time when “maidening” a new aircraft. Still, the rigidness of their processes resulted in consistent and well-prepared flight readiness which gave us all the confidence that Hyperion was ready for safe testing.
There are many aspects of RC flight preparation that can make or break a successful flight, but paramount are: ample thrust and the ability to achieve proper air speed, location of the CG, and control surface deflections. All of these were in question when it came to Hyperion despite the fact that the students had calculated, simulated or experimented to find the proper values and parameters. At the end of the day, all of that is subject to the accuracy of construction. And not just for the aircraft and airfoil, but also for gaps in the control surfaces, drag of external components (such as the gear), etc.
No matter what, a light aircraft with plenty of power is the best insurance for successful flight. Unfortunately, Hyperion was neither light nor was it blessed with an overabundance of power. Hyperion weighted a robust 48 pounds. The estimated body/wing loading was a hefty 42.2 ounces (2.64#) per square foot. Not a problem if you have an equally robust power plant. Let’s face it, a lot of power can cure a lot of ills. Unfortunately, achieving maximum output and efficiency from the Terminator motor was inhibited by the use of a 20” diameter, 4-blade propeller which was necessary because of the low ground clearance from the vehicle’s tricycle landing gear. Experimentation with numerous propeller diameters and pitches provided a maximum power output of 5000 watts from the Terminator (i.e. just over 104 watts per pound). Hyperion would only have 6.7 HP for its 48 pound airframe. In comparison, my 27 pound CompArf Extra 300 is equipped with a 10 HP DA-100. Yet, the students were confident that 5000 watts was adequate, and in the end, they were quite right.
The simulator provided a starting point for control surface deflections. The students had successfully adapted their Futaba 10-channel transmitter to an accurate model simulator of Hyperion. The program allowed us to experiment using the radio’s travel endpoints to adjust control surface deflection on the aircraft, and incorporating functions such as exponential. We adjusted the radio and surfaces such that Hyperion would fly smoothly and authoritatively. The values that were obtained from the simulator became our “low rate” starting point. Actual setup would also utilize a “high rate” for backup. The higher rates would prove to be necessary for stable flight because the simulator could not predict the loss of efficiency caused by gaps between the trailing edge of the body/wing and the control surfaces. A lesson most of learn early on in RC building and flying.
Numerous high speed taxi tests were performed to optimize both the stability and effectiveness of the tricycle landing, but also to experiment with the location of the CG. Simulations and wind-tunnel testing suggested that there may be serious issues with pitch stability if the CG was too far aft. Additionally, the location of the CG was very finite. In other words, the simulations also suggested that the CG location (for stable flight) was within a fairly narrow range.
The close proximity of the CG relative to the rear main gear also made taxiing in a crosswind quite difficult. This was exacerbated by the lack of sufficient rudder surface to induce yaw in order to assist with steering as the nose wheel was not, by itself, able to overcome a minimal crosswind. It became apparent after a short amount of high speed taxiing (and one mishap) that testing could only be continued under conditions with the wind nearly down the runway (or non-existent).
Early taxi testing without successful rotation or obviously lifting of the nose wheel also suggested that Hyperion was nose heavy. However, there was limited opportunity to shift the CG aft without adding additional weight and causing further instability on the ground. Conversely, the concern of potential pitch instability was always in the back of everyone’s mind, so the CG was moved back in small increments (i.e. 1 centimeter or less at a time).
Finally, on Saturday, April 6th, and after numerous high speed taxi events Hyperion achieved a very short flight. Hyperion successfully rotated and flew, but only briefly and without adequate pitch control. There was enough elevator to achieve rotation, but it took full deflection and when the elevator was slightly decreased it caused Hyperion to pitch immediately back downward to the runway. The resulting damage ceased the day’s testing, but also provided a great deal of knowledge and data to review and evaluate. Mainly, we were all now assured that Hyperion had enough power and lift to achieve flight. Questions about CG, elevator deflection, flap reflex, etc. were still very much up in the air (no pun intended).
There was much discussion about moving the CG further aft, but eventually that it was not implemented. Instead we focused on gaining adequate elevator authority. The elevator was modified in 3 ways: 1) positive trim up was added; 2) deflection was increased by 25%; and 3) exponential was changed from negative to positive. We concluded that the elevator needed to move quickly away from neutral and be less sensitive when the stick was at or near full deflection. This is counter to the way most flyers set up their planes, but seemed perfectly logical for Hyperion. Another modification was to increase flap reflex. Hyperion’s design was such that negative flap deflection (i.e. upward) also helped improve the elevator’s effectiveness.
After a lot of discussion and evaluation about the results on April 6th and settling on modifications, the team had to wait another nearly 3 weeks to try again. School schedules, business travel, parts availability and inclement weather postponed Hyperion for another flight attempt until Friday, April 26th. Even at that late date in April, another snow storm threatened the test flight, but snow was followed by very warm weather and the runway would be clear and dry on the day of the test. The million dollar variable would be the wind, which as everyone knows, had been very unpredictable and blustery throughout the early Spring.
Finally, the day would arrive and everything was ready except for the wind. The wind was not strong, but it was a crosswind. We did not want to risk another “taxi” mishap that would unnecessarily delay things further. However, the reality was that the school semester was coming to a close and many of the Hyperionites would be graduating and/or moving on to careers, internships or other destinies. The students were anxious to attempt a flight and had an “all or nothing” attitude. Even if it meant severe damage or destruction they were ready to risk it all in favor of a total commitment to flight.
Up until now, I had been very cautious with Hyperion. In a sense, caution had led to tentativeness and even reluctance to push for flight. Under normal circumstances, we take a new airplane to the field confident in the knowledge that a successful flight will be achieved. All of the questions and lack of success with Hyperion had created doubt and even a little fear. Success this day would depend on being fully committed to flight and to just go for it all. And fortunately the students felt the exact same way. They were willing to risk everything for one moment of success (regardless of how brief).
The Hyperion was readied for flight, minor issues were resolved and modifications were implemented. The vehicle was ready, but the wind was proving to be a pest. A fairly steady NE cross wind prevailed for most of the morning. Everyone was anxious, but I wanted the least of my concerns to be the wind. Finally, the wind began to wane and change direction. As it switched from NE to SE it also diminished. Additionally, there were brief periods when the velocity was very low. We positioned ourselves at the West end of the runway and waited for a lull in the wind. When the moment came, the goal would be to achieve a maximum throttle taxi as quickly as possible.
Stewart was at my side and prepared to make dual rate switches and trim adjustments as needed. We waited for approximately 10 minutes, which seemed like a lifetime, but finally a window of opportunity presented itself. I advanced the throttle and was able to taxi straight down the center line and achieved full throttle as I passed the first set of pilot stations. I waited a few moments longer then progressively pulled back on the right stick. As Hyperion passed the last pilot station it rotated and began to fly. It climbed out fairly aggressive, but not too steeply and accelerated once it was in the air. All the doubts about thrust and weight were erased.
I continued to climb at full throttle then began a fairly aggressive left turn. The first thing I noticed was a distinct lack of rudder authority. Thus, I was forced to bank very steeply in order to complete the turn without ending up over Leyden road. On the first downwind (westerly) leg I began experimenting with part throttle and control surface effectiveness. Reducing the throttle would be necessary for landing and to conserve the batteries which were not expected to last more than 4 minutes. The ailerons were trimmed, but sluggish, so I switched to high rate (+33%).
Well past the field I began another less aggressive left turn to the south. At reduced throttle and with a lack of rudder authority this took me well south of the parking lot and eventually back toward the east. It would fly at ½ to ¾ throttle, but I began to lose pitch control. It was on the upwind leg that pitch control completely evaporated, Hyperion was extremely nose-heavy. Hyperion was heading downward at approximately 10 degrees with the elevator at full deflection. We acted quickly. I advanced the throttle and switched the elevator to high rate. At the same time, Stewart increased the flap reflex. Pitch control returned before making a other wide-sweeping left turn that would put Hyperion back north of the runway and again downwind. By now it was readily apparent that landing was not going be an easy affair.
I also knew that I may not have time for several landing attempts so I committed to attempt a landing on the next upwind pass. I flew well downwind and made another sweeping left turn to a final approach. As I throttled back progressively, I also let Hyperion pitch forward at a fairly steep attitude and glide path. Just off the end of the runway and at approximately 50-100 feet high I again lost pitch control. Additionally, I could not keep Hyperion from drifting to the north side of the runway. Without pitch, I didn’t dare bank and the rudders would not hold it on course. Within 150 feet of the runway I knew I had 2 choices: throttle up and try to regain pitch control, or simply let Hyperion come to earth. I knew Hyperion was on a heading that would put it on the north apron so I elected to let it crash land there.
Before I took off, I had already considered the very real possibility (based on everything we had learned up to that point) that I may not have full pitch control, particularly at slower speeds. Under that scenario I would have to fly at a very high rate of speed and essentially fly it into the runway in order to land. An extremely risky and dangerous proposition with a 48 pound beast that had very little rudder authority. No, I had already contemplated the results of such a botched maneuver including it “cart-wheeling” down the runway or skipping off the concrete and landing in the pits or careening full speed into the fencing. The choice had already been made and I had the presence of mind in that last 150 feet to simply let Hyperion come to rest well west of the pit area and on the reasonably soft north apron.
Surprisingly Hyperion’s damage was fairly minimal. Hyperion can certainly be repaired and flown again although I am not aware of its future plans. The project will certainly continue and I sincerely hope that AAM continues to be an integral part of it. I know one thing for sure, despite all the commitment, work, frustration, stress, and uncertainty… I had a blast and would do it again in a heartbeat!!!
Hyperion Report – From Germany to Australia via Colorado in Three Minutes
Mark Johnson, an aerospace engineering graduate student at the University of Colorado, reports:
On April 23rd, 2011, a group of engineering students from around the globe convened at the Arvada Associated Modelers Airpark to conduct a three-minute demonstration flight of Hyperion. Hyperion is the most recently completed graduate project based at the University of Colorado’s (CU) Aerospace Engineering Sciences department. Hyperion is an experimental, 10-foot span composite aircraft designed to demonstrate hybrid power technology on a modified blended-wing platform.
The Hyperion team consists of graduate students from CU as well as the Universities of Stuttgart (Germany) and Sydney (Australia). The team was faced with the challenge of finding a suitable testing site to fly the aircraft. The Arvada Modelers Airpark, located only 20 minutes south of Boulder, quickly emerged as the top choice in meeting this objective. The primary runway was considered necessary for Hyperion: a 750 feet long, 50 feet wide, smooth, highway-grade concrete surface that proved to be ideal for flight testing a novel aircraft geometry. Combined with the welcoming, curious and community-oriented club members who accompanied the team at the airpark and advised on safety, these attributes finalized the team’s decision to schedule a test flight.
On the morning of April 23rd, light snow was falling and the cloud ceiling was low, but winds were adequate for flying. The Hyperion team, accompanied by R/C pilot James Mack of Boulder, met at the airfield and promptly conducted a final check-out flight of a half-scale prototype aircraft. The prototype was launched eastbound and flew perfectly. Satisfied with the results, the team completed final preparations and assembly of Hyperion and started rolling the cameras. After a brief taxi and weight & balance check, the aircraft accelerated down the runway and rotated smoothly in a distance of less than 200 feet. The 45 lb experimental model lifted off and climbed into the air to the cheers of spectators and students alike. After making a few circles north of the runway, the aircraft settled on all three wheels without a scratch as it rolled down the 750 foot runway.
The Hyperion team documented several lessons learned from this project, aside from the design tasks of the project itself. The logistics of flying, from weather limits to personnel coordination to FAA requirements all came into play as the project entered the flight test phase early this year. Having a helpful ground crew of experienced modelers, like the group at AAM, proved to be a huge help in making the final demonstration of this project a success.
Arvada Associated Modelers (AAM) is an AMA Gold Leader Club that’s dedicated to community service both in the City Arvada and the surrounding Denver metropolitan area. The Arvada Air Park is a City-owned facility that is managed and maintained by AAM through its lease with Arvada. AAM has been involved with the University of Colorado, Aerospace Engineering Sciences department and its student for many years. AAM has proudly and enthusiastically supported, facilitated and participated in numerous experiments and student projects related to CU’s Aerospace Engineering program.