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About rahill

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    Reid Hillview Airport, San Jose, CA (KRHV)
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  1. http://static.garmin.com/pumac/sa01899wi_aml.pdf
  2. Understood, she already told me that "xfoil doesn’t account for vortices, wing-body join, interface between the two airfoils, etc. so there are probably a lot of things contributing to the differences". I think she gets it.
  3. I've already got my daughter plugging numbers into XFOIL and wondering why the airfoil numbers don't match the measured data. I think we may have you beat in the geek department. Rich
  4. Oh, if you can find the drag polars, please share them - those would be cool to see. Rich
  5. But that reference states "This approach only holds for a blunt impactor (no aerodynamical shape) and a target material with no fibres (no cohesion), at least not at the impactor's speed. This is usually true if the impactor's speed is much higher than the speed of sound within the target material. At such high velocities, most materials start to behave like a fluid." (note: speed of sound in aluminum is ~6000m/s) It then goes on to discuss very high density projectiles, shaped charges, and the like. That's not the case here. Perhaps you meant to include the reference about impacts (from the same site) https://www.revolvy.com/page/Impact-(mechanics). "When vehicles collide, the damage is proportionate to the relative velocity of the vehicles, the damage increasing as the square of the velocity since it is the impact kinetic energy (1/2 mv2) which is the variable of importance."
  6. This was covered in the video (the longer one, not the 0:43 second clip). An equivalent mass bird deformed more and did less damage. The density of the drone, particularly the heavy battery, is something to consider.
  7. Energy goes up as the square of the speed. They address this in the video and mention closing speeds, assuming some velocity of the drone. The DJI they used is capable of 30+ mph so take that into account. 238 mph is maybe a bit fast, but (also addressed in the video) these things have the capability of doing more damage than an equivalent-mass bird.
  8. Can you double check this, or provide a reference? Best glide in an M20J is about 90 kts (load dependent). The low point in power curve (left of which is "backside") is the point of minimum drag, not the point of best glide. Best glide (L/Dmax) is to the right of that. I know we're mixing up topics now, but if you cross the threshold of Palo Alto at 80-85 KIAS, you're probably not going to land on that attempt. Rich
  9. Yes, I did something similar (a practice/estimate W&B, not a stall!) - I was a bit surprised to find that it was within range. Rich
  10. Wind was 6 kts at 040 so 90 degrees to 13 (which was the runway in use at the time, not 31). He was clearly unfamiliar with the airport - requested assistance finding the KGO towers when asked to fly there, then later requested help finding the runway. Finally found the runway on ~2 mile final - not a lot of time to set up for a relatively short field. The prop strike comment is speculation, we'll have to wait for the report to find out.
  11. “Two more months” - seriously, that’s what they said. Not really believable at this point though.
  12. We were based in Palo Alto for about 10 years - I don't think I ever saw the airport full. If transient fills, it seems like there should be other places available. There is a rebuild project that will affect (or already is affecting) the tie down areas. Best bet would be to call the airport and ask. Rich
  13. What are you "not sure" about enhanced traffic awareness? Now, with ADS-B out, you'll get traffic from the GDL 39 all of the time, instead of some of the time - it's a huge enhancement.