It's been too long without an update, no excuse. In no particular order:
Software Version 3.2.2j
Our most current code is version 3.2.2j. We are still testing this version, and, no we still don't have a functional "auto calibration" routine yet. The biggest challenge has been deriving a suitable AHRS solution from the mighty "ten buck chuck" ($10 IMU). This involves some rather complicated math and filtering techniques. Lenny currently has code running in a MatLab environment; but we (see what I did there?) still need to port that code to the Arduino environment.
From the Skunk Works, Lenny has been working on a better differential probe design that provides accurate airspeed information and is more tolerant of sideslip than the Dynon or Garmin probe. Since we already have Alpha Systems mounts in our primary test airplanes, the new probe is designed as a drop in replacement. We are currently acquiring some high-quality printed versions to flight test.
EAA Turnback Project
The team has been asked to participate in the EAA/AOPA/FAA turnback working group. The purpose of this drill is to develop pre-flight planning tools and training resources for the conduct of a turnback maneuver in the event of power loss during initial climb phase. Our primary contribution is providing accurate test data and maneuvers validation. This is a hot-button topic with most aviators. Not all airplanes have sufficient climb performance to make it back around; and, of course, ambient conditions have a huge impact. However, we've been flying demonstration turnbacks to show how easy it is to use the tone as a single reference for several years. The physics are such that an ONSPEED condition is an optimum blend of glide, turn and energy management performance--not perfect, but the Goldilocks portion of the Venn diagram where the "good enough" portions overlap. One of the challenges the working group faces is developing technique for non-AOA equipped airplanes.
Bob Baggerman, our resident flight instrumentation guru has developed a neat capability to translate the data from the test airplane recorded on the ONSPEED system into X Plane graphics. Here's a short video clip of the RV-4 disguised as a C-172 conducting a simulated turnback at altitude after a takeoff and departure stall:
This capability will be nice for developing training resources and the "wingman view" provides an interesting perspective that we don't get from our standard camera set-up.
Welcome Terry Lutz!
Most EAA'ers know Terry Lutz, experimental test pilot, one each and all-around excellent aviator. Terry has an RV-8 and is currently installing an ONSPEED system (hardware version V3, our current "homebuilt" configuration). Additionally, he will be bolting in a VN-200 reference gyro system and mounting a SpinGarage Featherweight YAPS (yaw, alpha, pitot, static) boom to the airplane as well. This configuration is effectively identical to the RV-4 and will give us a second, fully instrumented test airplane. This is 100% increase in capability for the team, which is huge! It also relieves me of "only man" status, which is never a net positive in any organization.
As part of the turnback project and to further demonstrate how the tone logic works, I recently tufted the left wing of the RV-4. Pretty high-tech stuff: yarn and some new fangled, no mar masking tape. The first step was to build a highly complicated, solar-powered fully digital yarn cutting jig...
After scoring the mighty 2 x 4, I simply laid the yard across it's length and used a sharp razor blade to slice up 4" strips of yarn in bulk.
To record tuft behavior, a new oblique camera mount was fabricated. I had to raise the camera as high as practical to clear the canopy skirt but still fit under the canopy frame as it opens and closes.
The rectangular planform with constant thickness and no twist/wash-out results in a fairly abrupt stall, i.e., the wing quits flying all at once. This is in contrast to a tapered wing of variable thickness with the tips twisted down which allows a stall to progress from the wing root outboard. Typically, the later configuration gives better buffet cues when operating near the aerodynamic limit. For RV's, the Friese type aileron remains effective thru the stall (although use of aileron during a stall is questionable due to the addition of adverse yaw), and a reduction in AOA results in quick re-attachment of the airflow (i.e., the airplanes starts flying promptly as the stick is eased forward). We'll share video on our YouTube channel as we work thru the next phase of flight test with the tufts.
Adios 433d Fighter Weapons Squadron
In December, the last class of F-15C Weapons Instructors was graduated at Nellis AFB, NV. The mighty-mighty still has the best aerial combat record in history: 114/0. I don't normally publish "news" other than what's up with our all-volunteer team, progress and good Vac least-common denominator stories; but this picture was just too cool to leave buried on the hard drive. This tail actually belongs to my old unit:
Supply Chain Woes
Lots of electronic parts are currently made of "unobtainum." This means we can't get the parts we need to build any new hardware; but we continue to share any bench stock we've got with folks that are building systems. There has been a great uptick in interest since the last round of the EAA Innovation Competition; and our objective remains getting inexpensive systems to the field one way or another, but there's not much we can do in that regard right at the moment, so at looks as though the focus for the next 6-12 months will likely be software development and continued testing of existing V3 systems. We may consider some redesign to accommodate parts made of "obtainium" at some point; but it's too early to pull that trigger. The follow-on productionized hardware design is currently on hold until things recover to a bit more normal.
Best wishes for a healthy and happy 2022, and my resolution is to update the blog a bit more frequently :)