Fluttering

[RPR]

My TH+ was flow 3952 flights including test flights after each new firmware updates. From the day of my first maiden flight to date, my TH+ is quieter vs my inspires.

Today, while accelerating to a height, I heard a flutter and I’ve never heard this before, even on a windy day or a hard stop. Just to be on the safe side, I quickly landed and did a thorough investigation, when went through my preflight list for the second time. Checked booms, motors, props and battery to make sure that it’s seated in place securely. Everything was okay.

I took off again and got to 55ft alt (wind 4mph) by this time, I was not looking at the bird, thinking that it might probably just a fluke, and concentrated on the monitor, moving the TH+ forward. 10 seconds into a slow forward flight my VO advised me to land, because he heard a flutter. Frustrated of his new and strange noise, I had to retire the TH+ early and used another sUAS to complete my mission.

Earlier this eve, I reviewed the footage, because if there was any abnormality such as a flutter it would create a wobble and that would become evident in the footage, but I have found none, the footage came out steady.

A flutter is caused by two factors 1) Wind 2) fluctuations of power of the motor.
My question is. Is there a way to retrieve my power load? If so, where is it located my log file? and is there a best way to bench test each motors? And if so, any suggestions on how to?

Thanks in advance, gang.

 

[AH-1G]

@RPR Check the two screws that hold the motors on the arm, they may have come slightly loose?

 

[RPR]

@RPR Check the two screws that hold the motors on the arm, they may have come slightly loose?

Good morning, sir. This will be my first mission in the AM, check for loose screws.

 

[Ty Pilot]

I have also heard this flutter on one or possibly two occasions. Like you I landed immediately and went over the entire craft and found nothing. I re launched and was not able to get it to repeat the noise. I eventually decided it was caused by wind possibly as it flowed over a rooftop. It was very strange and I have not heard it again in over three months.

I have also seen and heard another phenomenon that I can make the Plus repeat that I think is similar. On a windy day, when getting close to the ground, maybe a foot high, if I let the craft hover, it will begin a small series of jitters where it is pitching in one direction to hold position against the wind, and then release the pitch only to re-induce the pitch. This is almost like a scenario very similar to a pilot induced oscillation, it will continue this oscillation until I increase the altitude to about three feet or enough to get it out of ground effect.

My guess is that the flutter at altitude is a similar phenomenon but is only a guess.

 

[Phaedrus]

Also, when checking props aside from visually inspecting them you might try giving each blade a little bend and twist looking for cracks, etc. that might not show up except under load.

 

[RPR]

@Ty Pilot glad that I’m not the only one, how many flights have you had with your sUAS?

I’ve tested the Plus against my inspires and the Plus can hover in place unaffected by the wind and quieter vs the inspire 1 v2 as well as the Inspire 2, and the flutters on the inspires are noticeably annoying, but this the first time that I’ve noticed a flutter on my Plus, even on a hard brake or windy conditions.

Right now it’s 7:44 here in Cali. But at 6a I ran a flight test. Tested out the batteries for any changes in the voltage on a hover, but found none. However (and also, a note that I did not include to a member that I’m talking to via PM) when throttle up and pitch down (mode 2) to move in forward flight, seconds into the flight it flutters. (Wind 6mph SE) and battery V drops, once it flutters. I ran 5 batteries just to concur.

This made me believe that one of the motor or all the motors are declining(?)

 

[RPR]

Here in Northern California, we have a high wind warning. I’m going to fly around 15mph wind in a safe distance and height to see what happens.

 

[RPR]

Also, when checking props aside from visually inspecting them you might try giving each blade a little bend and twist looking for cracks, etc. that might not show up except under load.

Found none, but I will recheck and also balance the blades.

 

[AH-1G]

I'm wondering if this would work.
Remember the old days when checking your timing with a strobe light and put a white chalk mark on the flywheel.
Is there an instrument you can use, and put a dab of white finger nail polish on the blades to measure rpm?

 

[RPR]

I'm wondering if this would work.
Remember the old days when checking your timing with a strobe light and put a white chalk mark on the flywheel.
Is there an instrument you can use, and put a dab of white finger nail polish on the blades to measure rpm?

Aye!!!! I remember doing this when flying helis. Nice, I will do that. And I checked the motor screws as you suggested, intook them all out one by one, applied locktite, and made sure that I placed them back in the same angle of attack (degrees) per factory.

 

[RPR]

Also... I ordered spare motors to be shipped overnight (did a quick search on here and ID the correct motors and part number)

This flutter scares the heck out of me!!!!

 

[AH-1G]

I just recently replace all my motors, I purchased 8 in case something goes/went wrong. 1 new motor was bad, it fired up once and died!

 

[oliver]

Ball bearings can be incriminated, the sound of squeaking is sometimes random

 

[NorWiscPilot]

@RPR,

I do not have an H Plus (yet), but... I do have a couple H480s and an H520.

After reading your post, and remembering the saga of @AH-1G and his worn out motors, I added a little something to my pre-check before heading out in the snow.

Instead of simply checking for prop security, I gave each one the one-finger spin. To my surprise, I not only felt strong pulsing as I spun the first prop, but I also noticed what can be best described as a rattling sound. I checked the rest of the motors. Four of the six had the same feel and noise.

Upon further examination, these "noisy" props also had some play in the hub to motor interface. Not much, but noticeable. The two silent props/motors have no play. Of course, I replaced one of the noisy props with a new one. Tight as can be, and silent.

As a standard practice, I date stamp each of my props as I put them in service. This practice paid off as the four suspect props were put in service in March and May of 2017. The two quiet ones were installed back in August and October of 2018. I also include markings to insure I place each prop on the same motor during its lifetime.

I post the above for two reasons:

• a heads up for anyone not yet including prop and motor checks in their pre-flights;
• still trying to understand the definition of "flutter" and the source of it. Perhaps my experience can help either identify or at least eliminate a possible contributor.

@RPR - you state your pre-flight includes checking the motors and props. I am curious if this check includes checking the prop/hub play or tightness?

I don't have even tenth of the flights you have, but... being this particular craft is the one I fly at least three or four days a week, it does have some history to consider.

Best of luck to everyone trying to decipher the causes for this anomaly. We will all learn!

Jeff

 

[PatR]

Here in Northern California, we have a high wind warning. I’m going to fly around 15mph wind in a safe distance and height to see what happens.

Wait until tomorrow. If you can dance between the rain drops you should have some 30-50mph winds to play with.

I agree with Phaedrus in checking the props for a cracked blade. A weak or cracked blade can flutter.

 

[Ty Pilot]

@Ty Pilot glad that I’m not the only one, how many flights have you had with your sUAS?

I’ve tested the Plus against my inspires and the Plus can hover in place unaffected by the wind and quieter vs the inspire 1 v2 as well as the Inspire 2, and the flutters on the inspires are noticeably annoying, but this the first time that I’ve noticed a flutter on my Plus, even on a hard brake or windy conditions.

Right now it’s 7:44 here in Cali. But at 6a I ran a flight test. Tested out the batteries for any changes in the voltage on a hover, but found none. However (and also, a note that I did not include to a member that I’m talking to via PM) when throttle up and pitch down (mode 2) to move in forward flight, seconds into the flight it flutters. (Wind 6mph SE) and battery V drops, once it flutters. I ran 5 batteries just to concur.

This made me believe that one of the motor or all the motors are declining(?)

I've only got 211 flights at a little over 45 hours of operation and I would guess the first time I heard the flutter was at about half that and again just a little over three months ago.

If you have nearly 4000 flights thats got to be close to 900 hours give or take, so; yeah I would say a motor change might be in order.

 

[Phaedrus]

Nice being a late adopter. Letting others determine the TBO for props/motors

 

[Ty Pilot]

I actually was thinking in the beginning, when I got the Plus last summer- if I get to 50 hours, I might start to think about these things, heck at this rate I've got about four and a half years to go.

 

[RPR]

@RPR,

@RPR - you state your pre-flight includes checking the motors and props. I am curious if this check includes checking the prop/hub play or tightness?

Jeff

You got me here, I don’t nor I neglect to visually inspect the prop hub. Determining due to its design it’s the most secure hub that I’ve seen/use, but I do check for tightness. I will reconsider and add this to my checklist.

To add, I do date my blades, and I switch blades every 2mos

 

[RPR]

Update:

The new motors came in, and successfully installed each one. For those, interested on how to disassemble the motors follow this thread. Remove motor from H

I did not have time to bench test the stock motors due to a time constraint, I have to pack the Plus for my trip back to Hawaii. Once the motors are installed, I quickly fired up the Plus in my backyard, which has adequate area for testing (time of flight 1032) taking advance of the small window of opportunity before the rain starts again.

The current weather in San Jose, CA
Precipitation: 47%
Humidity: 92%
Wind: 24 mph SE

Inspire 1 Pro and Inspire 2 flutters in these wind conditions (this is normal...lol even with carbon fiber blades) Yuneec Typhoon H Plus, stable, quite and flutter free in both hover and forward flight, flying on build 784. My theory is that one of the stock motor is declining causing the flutter in forward flight, but I am not 100% sure, without testing the Kv, but by changing the motors it eliminated the strange flutter that I am not used to hearing on the Plus. Once again, my previous flights 3952 + today's test, I am now at 3956 flights.