New Swift down - what happened?

[broke-again]

My fourth flight and my new century swift is in bits :arggg:

Quite a lot of damage,usuall stuff; but worst part is a new 20c lipo with 2 flights on it!

Had just taken off and was about 4 feet in the air in a hover when i increased power it jerked hard to the right, then suddenly shot up like a bullet and was doing the funkey chicken as it did. Totally shocking to watch your new bird die and apparently having no control. I had the new co-pilot operating and had 2 previous flights using it with no issues.

At first i thought i had suffered some kind off major electronic failure until i arrived at the crash scene. The bird was sitting on its belly minus landing gear (exploded) and had clearly came in tail first. I was surprised to see that both blades were intact, bar a clean tear in one of the coverings.

I think i know what happened, but would like some other input and if i am right about what happened - what caused it? was it something i did?

I suspect and you will see from the pics - that there was a major failure on the main rotor grips. i.e where the pitch control attaches - snapped.

I think that one blade covering may have split mid air, allowing air to enter between the blade and the covering. (One blade covering has a clean tear) The difference in load pressure on the blade caused the pitch control to snap, which is why it climbed so fast. The remaining blade couldnt handle the load and followed suit.

Either that or i got two very weak blade grips......... :dontknow

On the bright side, i guess that is my first and last crash for 2006

Off to lick my wounds.

[cudaboy_71]

headspeed too high? what were you running?

[lperagallo]

Did you re-shrink the covering on the blades before you flew it? With the wrinkles on the blades is doesn't look like you heated the shrink covering up and made it tight. That's not good for aerodynamic airflow and balance. I assume you balanced the blades :dontknow .

I also think cudaboy_71 may be on to something asking about head speed. You don't want to run woodies above 1,700 RPM.

[broke-again]

headspeed too high? what were you running?


Im running 550+ motor 10T & Electron 80A 4 cell lipo's


Did you re-shrink the covering on the blades before you flew it?


Nope, they didnt look as though they needed re-shrunk. The wrinkle in the pic is on the blade that has a tear on it. I balanced the blades and they tracked well.

Pitch was set for +-10 and i was no where near top speed when it happened - i was only in a hover. With the set up i have, i reckon the top head speed would be 2040 - well over the 1700. Guess i should use the 8 tooth next time.

[cudaboy_71]

i don't know the swift. i was just guessing from the looks of the grips.

and, woodies, carbons, it doesnt matter. it's not the blades that broke, it's the grips. my next step would be calling century tomorrow and see what they have to say about it.

[lperagallo]

Almost all covered blades need to be re-shrinked before putting them into service, even if they don't look like they need to. Especially at high head speed any disturbance will put undo and un-natural forces on the blades that will translate into un-natural loads on the grips.
There is also no reason to be over 2,000 RPM headspeed. I'm sure Centruy will tell you that headspeed is excessive, escpecially if all you are doing is hovering. Blade grips do not fail unless under undue stress. Head speed should be closer to 1,500 - 1,650 in hover and maybe 1,800-1,900 in 3D.

[broke-again]

I emailed them with some pics, im concerned that this may be an as yet unknown design issue. Just my luck to be the one who finds it. :arggg:

I am also posting this in the Century forum.

I cant even bring myself to look at the remains of my heli... :(

[Rodney]

If the blades grip had broke in flight it would have boom struck long before climbing and going to one side. By the decription of the flight, it could have very well been the coving being loose on the blade, also did you glue the roots down to the blades? If the grips were the cause there would be a thousand more post just like this form everyone else having this failure.

[RAV50]

Sorry to hear of your mishap, but from the description of the event in your original post, there is absolutely no doubt in my mind that your crash was NOT the result of blade grip failure. These would have failed afterwords - during the crash.

Why? Simply because, if the blade grip control arms would have broke off as pictured, either the blades would have feathered at 0 degrees of pitch and lost all lift OR they would have feathered at 90 degrees in which case again they would have lost all lift and in this case you would also most probably experienced an in air boom strike!! In which case, you would have been witness to an in air explosion similar to the heli being hit by a shotgun shell - it would have exploded in mid air!!!

In either case, there is no way that your heli would have climbed at all after you lost control nor could it have "rolled".

The most likely cause was a radio or servo issue. What radio equipment was being used? Where was the receiver located relative to the Motor, ESC and Gyro? This is the areas that I would be prone to examine.....along with a few others.

[Adam Turner]

From the looks of your bird it appears that you have one of the original Swifts. That indeed had weak blade grips. Fortunately they saved me allot of blades when the grip broke in a crash instead of impacting the blade to much.

Now the New plastic Swift blade grips are much more stronger, I have personally tested them on a 2300 head speed 6s setup with 16 degrees of pitch using stiff Carbon fiber Rotorteck blades. Flying it trying to break it, and also in drag races at Fall Fest. So they are far more capable than the originals.

Sorry for your loss.

Adam

[RAV50]

Adam,

I agree the old original blade grips had weaker blade pitch arms then the current ones and win a crash they would break off and save the blades from damage.

That being said, they would never brak in the air under the flight loads of even 3d maneuvers.

This is why thye could not have caused broke-again's crash. He should look elswhere for the causes...as I mentioned radio components and their location etc.

[broke-again]

The co-pilot system that was on the bird recorded the events, no failsafes or bad frames and all servos acted as they should until the event. (the co-pilot records your flight and allows you to play it back on the PC) I have no issues with electronics, noise or interference and can definately rule that out - again the co-pilot allows you to check all this and im wise enough when it comes to electronics placement. i also had 3 previous flights with no issues at-all.


The only thing that i did notice with the swift is some shake during spool up - which i understand to be common place and the new style feathering shaft is supposed to help eliminate this. I got an older version (silver) the new ones are black.

It is a process of elimination, i have ruled out electronics thus the only explanation i have for now and from what i seen happen-the dip, crazy to-fro climb is a mechanical failure and all i have to go on is what i witnessed and the aftermath and this is what leads me to suspect the grip. Nothing else on the head or swash etc was out of place.

The grips were glued down and secured with the supplied screws.

Either way i guess i will never know and just wanted to play safe in case anyone else has this happen.

[broke-again]

I just went through the remains of the heli as it has been bothering me. I know its often hard to explain events, it is one of those "you had to see it" to fully understand as it all happened so fast. After reading the feedback and the references to boom strikes, i forced myself to look at the remains and think i did have a boom strike. I have never had one before and would have thought that the blade contacting the boom would have smashed into a million pieces. One blade is clearly marked on the leading edge with an impression in the wood and a nice crack- i didnt see it because of the covering and i wasnt looking for it either. The boom has a clean line impression too.

The pics dont show the blade markings too good, but they are there.

[RAV50]

That is a regular occurance in most crashes, AFTER the heli meets the ground - NOT in the air.

If it had happened in the AIR, your heli would NOT have climbed or rolled - it would have EXPLODED.

And as both your blade pitch arms are broke, I would bet that happened as the blades made contact with the ground, which caused one to lag drastically and contact the boom. That blade would be the one with the covering damage.

[trevorz]

I would agree with most of what is said. The grips pitch arms are broken, and I have had that same failure, but it happened when I hit the ground, not in the air. RAV50 is correct, if you were to lose both pitch arms in the air and boom struck, the machine would have made a very horrible sound in the air and exploded. It would have rolled up into a ball and fallen straight to earth. I know, it has happened to me after a mid air collision. Your boom strike occured during contact with the ground.

I have also had a hiller rod come off, and a blade flutter. It makes quite a noise, and you lose power and the machine comes out of the air, usually with some control. The machine will not climb suddenly, it will go to zero pitch or 90 degrees and do nothing but cause drag. I don't think that matches what you have exerienced.

In my opinion, I would say you got a radio hit, or your radio lost power, or perhaps an issue with the transmitter (bad pot perhaps on the cyclic). Anyhow, the blade grips did not break in the air, they broke on the ground.

Anyway you look at it, it sucks.
Regards,
Trevor.

[Dennisu]

broke-again

All I can think of is if it happened in the air then your linkages must have overtraveled the pitchhorns on the bladegrips. Did you check for servo/linkage travel to see if the horns could be moved beyond their intended movement?

[broke-again]

Thanks for all the feedback guys. Im at a total loss as to any other cause. Ive checked everything and all seems to be as it should. I would belive the radio issue, but the co-pilot recorded it all and gave it a clean bill of health.No failsafes, no bad frames etc On play back you can see the servos being given commands and moving as they should, but the heli didnt respond, only elevator(servo ch2) and (sevo ch6) produced any movement.

When i killed power it came down. Either way i am stumped. Maybe my not re-shrinking the blade covering had something to do with it. :dontknow

Ive not heard anyone else with this issue, most recorded issues appear to be with the tail, feathering and main shafts.

[trevorz]

Hi,

With regards to the co-pilot recording, I have heard reports of them being used in Gassers, and although the co-pilot did not record any issues, they were getting hits all over the place. Just a thought. Could be the servo came unplugged or is intermittent (I had that problem too on a servo), it worked great for awhile then would quit. You would let it rest, and it would work again for awhile.

I sure seems to me like the servo gave out, or a radio hit.

Regards,
Trevor.

[djtommyboy]

I just went through the remains of the heli as it has been bothering me. I know its often hard to explain events, it is one of those "you had to see it" to fully understand as it all happened so fast. After reading the feedback and the references to boom strikes, i forced myself to look at the remains and think i did have a boom strike. I have never had one before and would have thought that the blade contacting the boom would have smashed into a million pieces. One blade is clearly marked on the leading edge with an impression in the wood and a nice crack- i didnt see it because of the covering and i wasnt looking for it either. The boom has a clean line impression too.

The pics dont show the blade markings too good, but they are there.

I wrecked my trex 2 times becasue of boom strikes..belt drive locks BOOM!!! see ya.............

[WillJames]

Have you very carefully checked the servo wires for cuts or chafing? No RX or copilot can detect that I don't think if a servo wire is bad or chafed and causing glitching.

[comeflywithme]

What type of receiver are you using?

If its simplya Dual or single conv receiver rather than PCM then your problem might be interference induced from ESC into receiver - something that I found very common in Larger electric models.

This would make sense from the point of view that the heli starting misbehaving when you applied power as this would result in higher currents passing through the esc. This issue is easily resolved by coiling the esc receiver wire through a ferrite ring (costing peanuts).

I know there has been a lot of talk about one of the blade grips failing but as you described the first action your heli did was pull sharp to the right which a filling blade grip is unlikely to do.

Although its probably not the best comparisson, I have had a T-rex sized heli snap its Bell-Hiller link which essentially left one blade without pitch control. The heli reacted by shaking severely and poor response to control... having said that I managed to save it and it didnt act in the way you described yours.

Sorry to hear about your crash. Dont let it set you back too far - This hobby wouldnt be half as much fun without crashing (hell of a lot cheaper though :-) )

[broke-again]

This issue is easily resolved by coiling the esc receiver wire through a ferrite ring (costing peanuts).

I had the esc mounted on the frame near the motor, with a ferrite ring on the esc wire. The RX was mounted above the tail gear box and its an FMA failsafe rx. My gyro is at the front of the heli and all wiring was as neat as could be. In fact i was rather proud of my wiring and i know how important this is....they dont call me "Broke-Again" without good reason...iv'e learned the hard way. :D

I have spoke with FMA and i today shipped the co-pilot back to them so that they can check it over.

I checked all wiring, servos etc and cant find anything amiss..all linkages were good

I just wish i had some other explaination as to what else could have happened and i do realise that crashes are part of this hobby. I had a few before, some dumb thumbs and a few due to part failures, which is the most frustrating part of this hobby.

Anyway, i really do appreciatte everyones input. Thanks :hug: