This week on What the Heck Wednesday we have a turbine powered RC helicopter kicking up some dust on impact. The model is a beautiful Agusta A-109 Heli Factory with a PHT3 turbine engine. The flight starts out great and the heli looks fantastic in the air. Near the end the heli makes a descending left hand turn and that's when it all goes wrong.
It drops rapidly and then pitches the nose up way high, only to drop even faster and smack the ground tail first. The nose follows slamming into the ground and causing a tumble which shreds the rotor. It's an unfortunate event, but what do you think actually happened? Was it pilot error, engine failure or another mechanical issue that caused the crash. Let us know what you think in the comments below.
If you have a video of a weird or entertaining crash and would like to be featured on What the Heck Wednesday, please send me a PM with your submission.
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That to me looks like a vortex ring state situation.
In other words: Pilot exceeded the flight envelope. My heli flight school focusses on the specifics of scale flight, and this is exactly what makes the difference between light and overpowered 3D helies and heavy scale ships. 3D helies usually don't do this, but for heavy scale ships this is a real issue. |
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You could be right... at the 5 minute mark I see a significant change in rotor RPM, and it looks like RPM is going downhill from there...
I hadn't noticed that before. Have to revise my opinion... |
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I blame you ETHANOL!
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Latest blog entry: Assembling a Spandau kit.
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As far as I understand, whatever your thoughts are on the difference between vortex ring state and settling with power, geeez, this looks like classic settling with power to me with regards to full scale helis, which catches even very experienced pilot off guard. You can encounter this with forward speed - it's all about rates of decent and powered flight. When you encounter it - the heli drops like a rock with very low control authority. The first reaction is to pull pitch, which makes it worse - if it wasn't a vortex ring state / settling problem, the first reaction to flare and pull pitch would've slowed you down a bit.
re: settling with power vs. vortex ring state ... I guess I get that there's a difference you can encounter vortex ring states and not settle with power and vice versa - but the worst settling with power incidents are encountered when you enter a vortex ring state, which absolutely can occur in forward flight. maybe there's something about this particular model that prevents autorotation ... or a super low mass rotor system or something that i'm not aware of ... this is just my "i wasn't there and have just enough experience with the topics to be annoying opinion" ![]() (edit: i'm not discounting that a mechanical issue could have been the primary cause of power loss ... but it may have been recoverable. And even then, even the absolute best pilots might have failed to recover the situation. either way it absolutely sucks.) |
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Last edited by run; Dec 18, 2020 at 09:50 AM.
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Latest blog entry: Assembling a Spandau kit.
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Latest blog entry: Assembling a Spandau kit.
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