Week of 02/25/19: Preperation of the C-Astral

After months of waiting, our primary aircraft for the capstone, the C-Astral Bramor, has arrived. The Bramor is a fixed-wing catapult-launch, parachute recovery, survey purposed, multi-sensor aircraft. The system is engineered with a combination of conventional aviation manufacturer techniques and modern UAS production methods to maximize fidelity of production and operation. The aircraft is truly state-of-the-art and will be crucial for the mapping missions we have planned at the scale we wish to accomplish them. For more information on how the aircraft operates specifically, please see my previous post on the test flight of the aircraft in the Fall of last year. With the aircraft arrival, the primary task for this week was to take an inventory of the product's components and practice running through checklists. The inventory is important for obvious reasons, as an aircraft this complicated will not fly if critical components are missing, but practice runs (pretending we are in the field) are also critically important. There is many "moving parts" to setting up this system for a mission and if done incorrectly, it could severely damage the aircraft. Two major operational benefits to this fixed wing aircraft are also it's biggest weaknesses: the method for takeoff and landing. Having a catapult launching system and parachute recovery system enable the aircraft to operate in regions where a tradition style of takeoff (lateral takeoff for fixed wing UAS) is not possible. However, the added benefit of being able to operate in non-improved terrain comes with costs to safety. The catapult system, when under tension, could severely injury someone if not set up properly. In addition, an incorrectly configured catapult could damage the aircraft on takeoff. If the parachute system, including all mechanisms for deploying or storing the parachute, malfunctions in any way, the aircraft may be unable to land safely (a safety risk to the aircraft and others in the area). For these two reasons, in addition to other slightly less critical reasons, we must produce competent trained flight crews before the aircraft ever launches into the air.

Unboxing and Inventory: Specifics of Our System

The aircraft is shipped in the two large containers at which it is designed to be carried in. What is unique about these containers, is that they lock together when mounted, so that an individual can easily maneuver the crates in the field (Figures 1 and 2).  One of the containers is built to house the aircraft and it's physical components, while the other is mostly built to hold the catapult and other operational equipment (Figure 3).

Figure 1: The aircraft and associated equipment being removed from boxes

Figure 2: The two containers stacked and latched together, this is how the system will travel

Figure 3: Both containers opened to display the C-Astral Bramor system in aggregate

Something important to make note of is the MicaSense reflectance panel positioned on top of the aircraft fuselage (Figure 3). On closer examination, an individual that may have worked with C-Astral systems in the past may notice some other peculiarities. Most notably, the silver rectangular structure towards the nose of the fuselage in figure 3. The panel as well as this other structure, which is a hardened sensor GPS and sunlight sensor, are for the MicaSense Rededge Altum sensor that C-Astral integrated into this system for us. While significant engineering challenges had to be completed to integrate the sensor (as seen in figure 4), C-Astral has promised that the sensor should work as designed. This will allow us to complete cutting edge multispectral and thermal remote sensing data collection at our test site. At the moment, this is the only Bramor aircraft in the world integrated to use the Altum sensor.

Figure 4: Rededge Altum sensor integrated into the fuselage of the C-Astral Bramor

Taking inventory on the system, it appears all the ordered equipment is present except potentially a GNSS ground station. The C-Astral uses a PPK GNSS system which may possible not need a separate ground control system for position correction, and if it does, we have systems that can currently provide the correct data. Either way, further discussion with C-astral will take place to identify if we have the requisite equipment.

Dry Run 

After completing the inventory, we decided to conduct a dry run of an operation with this aircraft. There a few main reasons for doing this:

1) Gaining proficiency and experience at utilizing this system for flight operations
2) Identifying critical steps where additional attention to detail may be needed for safe flight
3) A dry run acts as an additional inventory, where it would be clear if we are missing components, as we would be unable to complete checklist items

Before flights actually are conducted with this system, it is likely that we will do many dry runs, to the point where we are entirely proficient with the system within 3-4 person flight crews. All steps in the checklists were completed as listed except for:

1) Applying tension to the catapult
2) Any steps that required GPS (we were inside without GNSS connections)
3) Physically launching the aircraft

The first steps involve setting up the catapult and ground station. The catapult essentially unfurls into a long barrel like structure with a few simple locks to maintain it's rigid structure (Figure 5). While it may appear that the elastic bands are under tension in figure 5, they are not, as the catapult is not wound. In this state the catapult is relatively benign, however, in all steps in which the catapult would have been under tension, we treated it as such.

Figure 5: Catapult as set up for aircraft mounting

An important point we made note of in the checklist is how inconspicuous the safety pin is on the catapult (figure 6). The safety pin is a simple bolt on the end of a blue steel coated steel cable. Not only is it easy to miss, but it would be very easy to mistake or think that it is unimportant. We made a point that only one person during the operation will have the role of ever touching this pin for any reason as, almost certainly, the catapult is the most likely component to injure someone (with most potential for severe injury). Another observation we made is how easily the elastic bands can get tied together, which may be dangerous for safe operation.

Figure 6: Safety pin (in blue) on the catapult system

 Putting the aircraft together is very straight forward. The wings are attached to the fuselage with simple spars, and a similar mechanism is the case for attaching the winglets to the wings. However, just because this step is easy does not mean there are not critical aspects. Many of the antennas and data transfer ports are connected while the wings are attached. If these are left disconnected, it could overload the internal circuits of the aircraft's radios, rendering the entire system useless. A perhaps minor and odd step, the wings are secured with a thin layer of tape. The assembled aircraft placed on the catapult is in view in figure 7. The catapult acts as a staging station for late checklist items because it is a clean surface.

Figure 7: C-astral mounted on catapult

Once mounted, our attention turned to packing the parachute. manipulating and packing the chute into it's compartment is actually a fairly complex and obviously important step. The parachute deployment system uses a system of latches, servos, cables, and pins to function properly and each of these things are prepared or tested in the checklist. There is a safety pin for the compartment, as seen in figure 7 (remove before flight pin). Testing the compartment caused some confusion due to the fact that steps that seemed to require electronic manipulation of the servo occurred before electrical systems had been engaged according to the checklist. There seems to be a means to manually open the latch, which we did (figure 8) but we were not sure if this was the proper way to do this. Further study will take place.

Figure 8: Manipulating parachute cover

The parachute must be folded before each flight. Fortunately, our team has a few members that have been practicing folding and packing the parachutes since the beginning of the semester. They are both involved in equipment, so flight crews may not be required to pack before each flight, as they may handle it before the aircraft is dispatched. An example of the folded parachute is available in figure 9. At the end of our checklist, we did test deploy the parachute system on the ground, which was successful.

Figure 9: Folded C-Astral Bramor parachute

Kyle, being the operations manager, mostly handled the flight control software. In the field, each pilot will handle the role he did during this exercise. The system is fairly straight forward and we will be in the classroom simulating the software as seen in figure 10 next week. C-astral provides fully functional simulations that we will run through in addition to further dry runs next week.

Figure 10: Software display of C3P flight software