Okanagan_Jumper

I never knew if the flat earth thing was just an act with him.

Hello, skow. The 5 degrees angle of attack was definitely in correct as you surmised. The 40 degrees was based on my glide/flight path angle of 45 degrees down (based on a 1:1 glide ratio), minus the incorrect hypothesis of an angle of attack of 5 degrees. I managed to used my iphone strapped to my stomach yesterday to record inclined angles in the range of 20-21 degrees down yesterday. Admittedly there was a bit of movement of the phone, and I wasn't able to record the readouts (once per second). Achieved glide ratio at peak sustainable (before translating airspeed into lift) was in the 1.0:1 to 1.2:1 range. If the data was valid, and that's a big if, then the angle of attack would be in the range of 43 degrees (angle down) - 21 degrees (body angle) = 22 degrees angle of attack. I'll set up an Arduino with an accelerometer, along with an SD card to record results, in the nect few months. I assume tracking suit manufacturers can use wind tunnel data or some other means of gathering experimental data. I'm just doing it because I find this type of stuff interesting. It doesn't need an end goal... I was flying a PTS and my friend was in the original Sumo. He flew much faster this weekend so I ended up concentrating on trying to keep up with him. The flysight shows me edging him a race to the lake water's edge at the DZ, but he did achieve higher groundspeeds and glide ratios at times. Cheers John

I kind of figured 35 degrees was too steep. Hopefully I’ll satusfy my curiousity tomorrow. And that’s what it is, curiousity. Luckily the sport is big enough for jumpers who jump for whatever reason and with whatever goals and there’s no need to justify why you jump, or how you jump.Quote

Hi guys. Thanks for the feedback. I think I could have done a better job of explaining myself, as I'll be pushing pack from the gate in just under 2 hours at the command of a 737NG. Ergo, I've got the theory of flight fundamentals in the bag . I was trying to dumb down the essentials of aerodynamics for those who haven't studied the subject. I have two FlySights and I will be loaning one to a newbie tracking suit friend tomorrow. Last week when we flew together, he was flying much too slowly, and consequently his performance suffered. Yesterday I was thinking of how best to explain the need for a steeper angle in order to achieve a better glide ratio. For a conventional general aviation airfoil, the angle of attack required to achieve the best L/D is along the order of 5 degrees. I *think* I'm okay in assuming that it will be similar for tracking in a tracking suit. Therefore, if I am capable (and I am) of a sustained, no wind, glide ratio (GR) of 1.2:1, then my body angle (zero wind) will be 40 degrees (flight path for 1.2 GR) - 5 degrees (angle of attack) = 35 degrees. I have an app on my iPhone that measures inclination. Disregarding accelerometer errors (for my needs I think that's reasonable), I will measure my body angle down by strapping the phone to my chest tomorrow and listen to the audio readout of my angle to see if it's close to the 35 degrees predicted. I realize I won't be tracking on a regular basis, and maybe never again, with an iPhone strapped to my chest, but I just want to see if the 35 degrees is accurate. It seems to me that in the videos of trackers they look flatter than 35 degrees down. Standby for data! Cheers, John

I think this question is best asked here in the wingsuit forum, though perhaps basejumper.com is where I'll find the tracking experts. I was wondering about my body angle down, relative to the horizon, in order to achieve what I think is my best glide ratio (still air) of 1.2:1, or 1.3:1 when using my PTS tracking suit. If I assume for simplicity that my best glide ratio is 1:1, that would mean I am flying/tracking along a 45 degree angle flight path with respect to the ground/horizon. If my body was pointed exactly along this 45 degree flight path, I would have a zero degree angle of attack. The angle of attack is the angle between my body (line from head to toe) and the relative airflow (opposite direction to the 45 degree flight path). I think that I should probably have a positive angle of attack to achieve this 45 degree flight path. Therefore, if I assume and angle of attack of 5 degrees, my body angle would be tilted up 5 degrees from the 45 degree angle down, or more simply, 40 degrees body angle down. Realistically I think I can achieve 1.2:1 glide ratio, which approximates a glide angle of 40 degrees down from the horizon. If I assume a 5 degree angle of attack, then my body angle should be 35 degrees down from the horizon. So, my question, does the above seem realistic? Those of you who have experienc in tracking suits, do you think you are in the 30-35 degree angle down when tracking for max glide performance. I'm sure many will have suggestions for improving tracking performance, but I'm not asking that right now. I just want to know if the consensus is that a body angle of 30-35 degrees below the horizon seems about right. Thanks for your time. John

And I recognize the hazard of impalement from the sharp probe end, which is why I would only jump solo with such a device, and only in the interest of science! :)

I have not jumped with the longer of these two pitot tube arrangements, but the shorter set up did not provide any useful data. Notywithstanding the fact that the helmet moves in flight, I believe it is simply not in free stream airflow. Of the longer set up, I believe that it might give useful data, once the helmet is more or less stationary. I thought about trying some sort of gimbal arrangement to keep it pointed into the relative airflow, but I have more recently focused my efforts on placing a pitot assembly alongside the gripper. I have recently been distracted by an unsuccessful attempt to secure a flying job in China, but do hope to spend some time now revisiting the WingNut project. [inline IMG_0984.jpeg] [inline IMG_0981.jpeg]

I'm not sure what the incentive would be for anyone to produce a $200 wingsuit, given there would be no profit in doing so. Wingsuit manufacturers are not philanthropists. They exist to make money.

For some reason, I don't know how to post images inline, but anyway here is the probe as I tested it on the wing.

I agree. That said, I got good results from my indicator when I placed it on the wing of my father's airplane. I tried placing it below the wing, but lost the Bluetooth signal. I need to go back and do some more experiments with the style of pitot tube, but the static pressure sensor inside of the housing correctly indicated static pressure, so I think that the concept works fine. I just need to refine the size of the tube opening (and wall thinckness) to find the most forgiving (regarding angle of attack with respect to airflow) pitot tube head.

I tried so many things. I now have a cupboard full of things I don't need. But I agree, all we need is something that projects/replicates the screen of the phone. I just received my second Moverio (minus the control module), in order to experiment with different set ups. One problem is getting the right combination of sunlight filter to correct for bright sunlight. Making it too dark, prevents one from easily seeing other skydiving traffic. I also plan to try out a LoRa transceiver that will transmit altitude and coordinates of another skydiver, so that when I am within 1 km or so, my device will give me bearing, distance, and altitude of the other skydiver. A version of what is called ADS-B in civil aviation.

Obviously my project isn't a commercial one, but I am using augmented reality glasses and sensors and a Micro Controller Unit to display altitude information (among other data) visually in front of my eyes in a Heads Up Display (like fighter pilots use). What I found really cool about using this system is that I have the altitudes color coded so that in addition to seeing the numeric readout, I have the numbers in Green, Yellow, Or Red depending on the altitude range. One day, helmets will have visors that have this set up or something similar, to eliminate having to wear wrist mounts or chest mounts.

Hi Yuri, Why is there a .5m minimum in order to get into the undisturbed free stream air? I ask, because on my father's airplane, the pitot tube is under the wing and a mere 4 inches from the wing surface. I took a break from this project over the summer while I spent time at the bridge in Twin Falls, but recently made some progress with the display. I have adapted a set of Epson Moverio BT-300 Augmented Reality glasses to function as a Heads Up Display (HUD). While not perfect at this point, I did 5 jumps with the set up on my G3 and it was very nice and not distracting having digital display of altitude, groundspeed, magnetic track displayed on the screen. Airspeed is still not functioning to a good standard, but I will still keep trying. On the last two jumps, I programmed in a waypoint (using Google Maps coordinates) which was the place I wanted to deploy my canopy at, and the system successfully gave me navigation (direction/bearing and distance) information to this waypoint. Currently, I can't raise the helmet visor with the glasses in place, so I need to work on that aspect. Either that or the AR industry needs to come up with something with a smaller footprint for skydiving applications. As the system stands, I use information from a GPS unit and temperature/air pressure sensor sent to an Adafruit Feather BLE MCU, which then sends the formatted date via Bluetooth (BLE, or Bluetooth 4.0) to the Moverio. I don't use any of the Moverio's sensor information. Essentially, the Moverio is a display, with a Bluetooth receiver, and an android processor which uses a simple App I designed. I spent the last two months preparing for a job interview in China which I was unsuccessful at, so now I can go back to devote some time to this project. [inline G3_Moverio_Rotated.jpg] [inline IMG_2877.jpeg] [inline IMG_2815.jpeg] [inline IMG_2816.jpeg]

Hello. I managed to do 3 flights with my WingNut system in January at Skydive Perris. I was satisfied with the performance and have continued with development. My first flight I set a target airspeed of 95 knots and that was much too slow for the distance round of WOWS. The second run was with 110 knots and that was much better performance. The LED system in use then was accpetable but not ideal as it did not indicate absolute speed but rather indicated a speed above or below the target speed entered prior to exit. The latest development has focused on designing an Android app for use with the Moverio BT-300 augmented reality (AR) glasses. I have a rudimentary app programmed now that indicates speed both in a digital readout and on an analog style airspeed indicator. A 5 minute video [url=https://youtu.be/nlLZoD7mAOc]here[/url]. Skip to 3:45 mark for the app in operation. Cheers John

Don't need to break out the flight computer because it's going to tell us about path over ground, which I think we aren't talking about. We are interested in the aircraft's response in the air. Just landed here in Edmonton. On approach we had a moderate headwind from about 45 degrees from the side. If that headwind had suddenly increased and was still from the same direction, what wouldn't have happened is that the aircraft would turn more into that headwind. We would need to manually adjust the heading to compensate for the increased drift in order to stay on the final approach course. Not sure if that helps. John

I believe we that we all agree that a steady wind won't result in a heading change of a descending parachute. The theory is now that a wind from let's say the front right side that increases in strength will result in a turn of the canopy to the right. May ask what would happen with a wind from the front right that is decreasing in intensity?

We'll I ain't ever seen an airplane turn into an increasing wind from the side. That's only in the first 19000 hours of flying time though. Still time for it to happen I suppose. :) Take care

Bill, the weathercocking only occurs on the ground. There is no weathercocking in the air. As soon as the aircraft lifts off it no longer has a clue where the wind is coming from and hence won't turn into the wind. All it cares about is airspeed and angle of attack.

On the takeoff role, the goal is to keep the aircraft tracking straight down the runway and the wings level, which meams using aileron into the wind and rudder to keep the nose straight. Depending on the strength of the wind, it can feel quite awkward as the wheels skip and hop a bit. The controls in this case are basically crossed, with the ailerons turning left and the right rudder pedal being used to oopose the aircraft's tendency to turn to the left as a result of weathercocking. As the aircraft lifts off, the pilot quickly and smoothly returns the aircraft to coordinated flight. This may mean the pilot will turn the heading of the aircraft towards the wind direction, thereby trying to track the aircraft straight over the ground in line with the direction of the runway, but many departure procedures specifiy maintaining runway "heading", so the aircraft longitudinal axis will remain lined up with the runway, and the aircraft will simply drift with the wind. It should be noted that the weathercocking only happens as a result of an unbalanced force that occurs while the aircraft is attached to the ground. Similar to the effect of a boat on a water. Once the aircraft lifts into the air, there is no longer an unbalanced force, and no longer any weathercocking. (And no tendency to turn into wind or out of wind.)

And that is based upon what.... Well, for one thing a boat is floating on water. It's, not moving through the air. When I did my BASE course in May with SRBA, I realized immediately that Tom Aiello understood airflow and canopies as good as a pilot. Perhaps he could explain this stuff better than I could. I'm in the simulator in March or April. If we have time, I'll get the instructor to program in a very rapid shearing wind from the side and fly hands off with no autopilot and film the results. Cheers

This might be true for boats but not for planes or parachutes I'm afraid. Maybe use a submerged submarine as your sample and see if your theory still holds.

kallend, the relative airflow (relative wind is the less preferred term) is defined as being equal and opposite to the flight path of the aircraft (parachute), so unless the aircraft is moving sideways through the air (not over the ground), there can't be a relative airflow from the side. That would imply that an aircraft could fly with a wing pointed forward and the nose to the side. That would more than likely mean the aircraft was in one heck of a stalled condition.

With all due respect, no. We practice microburst encountering procedures almost everyone we are in the simulator (every 6 months). In the aircraft I'm currently typed on, the Boeing 737NG, it calls out "WINDSHEAR!" repeatedly when encountering either a rapidly increasing headwind or a rapidly increasing tailwind. In the situation you describe, a rapidly increasing tailwind, the immediate reaction of the aircraft is a loss of indicated airspeed as noted in the airspeed indicator, a concomitant loss of true airspeed, and the resulting loss of lift , and therefore a loss of aircraft performance (speed altitude) up to and including an aerodynamic stall. We don't ever train to expect a turn "downwind" because it doesn't happen. Most aircraft, and to a lesser degree, most ram air parachutes, are designed to be inherently stable. For aircraft its pitch stability means it will generally try to return to original speed. Roll stability generally means the aircraft will initially maintain the roll attitude it was left in and gradually end up into an increasing spiral dive (descending turn of increasing speed and bank angle ) until it eventually exceeds design speed and loading leading to structural damage. In a decreasing performance wind shear event, after the nose drops in response to its loss of airspeed and pitch stability, left alone, it would return to its trimmed pitch attitude and airspeed. I used to fly sailplanes. In heavy convective activity, one wing would occasionally encounter a strong thermal (column of rising air) and thus would result in an imbalance of lift between the left and right wing. The pilot would then have to return the wings to level flight, but there was no tendency for a sailplane to turn "downwind". I'm just on my way to fly to Honolulu. If we encounter any jet streams in descent I'll try to get some photos. Cheers John

Well, in the jet I fly, the wing will move up or down or yaw slightly in response to air flow changes due to turbulence and shearing effects of changing wind velocity. How much a wing or parachute reacts to this airflow change is a question of stability, and for a ram air parachute this is complicated by inflation. But I think you can give up any notion of defending the idea that wings, inflatable or not, turn downwind as a matter of course. If there is a built in turn well that's a different topic. P.S, I've flown in 150 knot tailwinds up at altitude and the aircraft shows no desire to turn around.

Oh gosh it's hard to read posts implying headwind or tailwind or crosswind affect flight characteristics of an airfoil in flight. As others have stated, a wing in flight doesn't care what it is doing over the ground, it only cares about it's airspeed. A change in the wind's velocity results in a momentary change in the wing's performance until equilibrium returns.