Unraveling the Mystery: Helicopter Ground Resonance Explained
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- Опубликовано: 10 дек 2023
- Ground resonance is a dangerous and unsettling phenomenon unique to helicopters. It arises from an imbalance in the helicopter's rotor system, specifically when the rotor blades, instead of being evenly spaced, clump together on one side. This uneven distribution causes the helicopter to oscillate or 'rock' in sync with the rotor's spinning frequency. Imagine a washing machine during its spin cycle; when all the clothes are lumped together on one side, the machine starts to shake violently. That's similar to what happens in ground resonance.
This hazardous situation usually occurs when the helicopter is on the ground. The helicopter's landing gear plays a crucial role here. Under normal conditions, the landing gear allows slight movements to absorb the rotor's vibrations. However, if the landing gear is restricted from moving - perhaps due to uneven ground, sticky or frozen surfaces, or mechanical issues - it can't perform this critical function. As a result, the vibrations from the rotor blades get transferred directly to the helicopter's fuselage, amplifying the rocking motion. If not quickly controlled, ground resonance can escalate, leading to severe structural damage, or in extreme cases, a catastrophic failure of the helicopter.
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As Always, Thank you very much for your videos Glenn :)
My pleasure!
Great video, explains perfectly what is misunderstood by a lot of people. I got a two bladed Rc model into ground resonance when I had it secured down to a piece of wood. I was demonstrating the lag effect of aerodynamic paddles, a bit like Arthur Young's video demonstrating his stabilizer bar. Many people say you can't get a two bladed rotor into ground resonance but you can if they have hinges that allow the out of phase condition as you mentioned. Cheers
Merci pour vos vidéos de grande valeur pour tout pilote d'hélicoptère!
My pleasure
I really like your channel it's very clear and well done
Thank you!
Great stuff 👍
Thanks 👍
Great video and illustration!
Thank you very much!
Great video sir
Thank Laxmidass!
Great video. As a follow-up, why is the rotor system described as a semi-rigid? This has been an ongoing conversation in my group. The ability to lead/lag, flap and feather independently, not to mention the capability of ground resonance, reinforces a fully articulated rotor system.
The statement you are referring to has been around since the 70s in their publications.... which is... Starflex semi-rigid, bearingless hub (laminated glass-resin star) without a drag damper. No grease nipples. Modular, fail-safe design. These three sentences have been a source of confusion for many years and yes, it should have been fixed by now. When they wrote this, as French speakers, they did not know we name a rotor system design... semi rigid... They were relaying the flexibility of the rotor system and to highlight that it wasnt a Rigid Rotor system. They were not naming it semi rigid. They are very adamant that the design type is Starflex. So in other words Semi Rigid in that sentence is not referring to a Semi Rigid rotor system design. Does that make sense?
@EUROiSAFETY Yes! That absolutely makes sense. You're 100% accurate in the reference. Thank you for the clarification.
Hi Glenn,
I always wanted to ask this:
Could you please create a video (if it’s something you reckon would be worth the effort off course) explaining the significance of the XPA and XPC values displayed on the VEMD of the AS350?
Specifically, how does the percentage displayed (ideally at 85%) relate to the power pedal and collective utilisation?
Also, how might deviations from this value impact manoeuvrability, torque, and lift, especially during high-altitude landings?
I think that this will benefit a lot the community, especially since many pilots I know (over 8k hrs of flying) don’t even know how to get this info from the machine.
Everyone is rushing to start the H125 / H130.
Everyone talks about how fast is starting.
I don’t see many people on the ground doing their check before lifting off.
Most guys I know never check the FUEL P on H125 and H130 as it not display by default.
I think that going over that aspects of the VEMD will be a great help for everyone.
Also, I wish you a merry Christmas and a very happy new year and thank you again for your work, you’re doing a lot for the helicopter pilots community my man.
♥🚁🙏
Merry Christmas and Happy New Year to you also! I appreciate the kind words. Its a good idea to do some videos on a deep dive into the VEMD! I will try to come up with some good ones. You seem to have some specific thoughts. If you would like to share them with me would enjoy hearing. You can email or DM on various platforms.
The presentations of your videos are incredible. Recommend me who makes them so I can work with them or use some specific software.
Thank you... we appreciate it. If you are referring to the graphics... we have a team of in house artists that create all our content.
Correct me if I'm wrong. I thought people always said also if it starts to happen to raise collective and get off. The ground is that not true?
Only when the rotor disc is still at flying rpm as mentioned at the end of the video.
OK Thanks
Why does it only occur in AS35x or any light copter only?
it can happen in all helicopters with a rotor system that leads and lags
Lot a mumbo jumbo for just saying it's out of BALANCE
Thank you for your comment. I appreciate your perspective and it's interesting to see different viewpoints. Sometimes, complex topics like ground resonance in helicopters can be perceived as overly technical or detailed, which might be due to the Dunning-Kruger effect - a cognitive bias where complex concepts are oversimplified by those not deeply familiar with the topic.
The goal of my video was to demystify this phenomenon, which is more intricate than a simple balance issue. Ground resonance involves dynamic interactions within the rotor system and the helicopter's structure, crucial for understanding helicopter safety.
I understand that online discussions can sometimes lead to quick judgments or comments, often influenced by the impersonal nature of digital communication. I aim to create content that is both informative and accessible, encouraging a deeper understanding and interest in aviation topics.
If you have any specific questions or need further clarification, feel free to ask. Engaging in constructive dialogue helps us all learn and grow. Thank you again for engaging with the content and I look forward to any further thoughts or questions you might have.
@@EUROSAFETYTRAINING duh I'm too stupid🥴