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Unexplained crash

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Old 03-30-2014, 09:45 PM
  #1  
turboromy
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Default Unexplained crash

I have crashed many but my last crash is the most difficult to reason why.

MODEL: 3DHS Vyper 65"
RADIO: DX8 and AR6210X w/ JR 6.0 2500mah battery
SERVOS: 2 futaba 9650 + S9551 + Spektrum A6010

With above setup, I had flown with not a single trouble except it feels not powerful enough. So, a new 6s lipo is put on with very satisfactory results.
Before, I flew with 5s about 85 times. With this 6s, I have flown about 5 times, and this Vyper crashed on its 3rd flight of the day.
I typically flew 6-7 times (w/ no receiver batt recharging, and each flight was about 6minutes) with 5s with no problem.

On this 3rd flight that ended up in crash, I vertical dove and rounded out to a level flight at about 30ft. Almost immediately I heard a banging noise and thought I hit a bird. Then it slowly rolled to left and lost altitude then hit the ground. Crash site inspection revealed it was the canopy popping out first. It was found about 100ft before the main crash site. Also, leading edge of both side wing show no signs of hitting anything. Carbon rod is undamaged either. Also, neither canopy nor latch was damaged. Only damage was clear plastic (glass) portion from the canopy near the latch hole. Was it from dropping or did it cause the pop out ? I don't know.

It was a bit too short from canopy popping to crash to tell exactly what happened, but it did feel like signal loss. And I really wonder why it would happened at that exact moment. Vertical dive was a bit faster... but nothing seriously fast. (was doing pattern practice)

And, this is my reasoning.
With this new 6s, it flew about 10-15% faster, causing higher battery amp draw. It was simply bad luck signal loss occurred at low altitude giving no chance to recover. Canopy popping was somehow relates to higher G maneuver which also drew more juice.
Does this make sense ?
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Old 03-31-2014, 07:23 PM
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jester_s1
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Could the canopy coming off have let the battery come loose?
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Old 03-31-2014, 10:38 PM
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turboromy
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Thanks for the reply.
No, I remember two aileron servos 9650's plastic gears broke and were making those spinning sound. Receiver battery was located far from canopy.
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Old 04-01-2014, 03:06 AM
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I have seen wings flex in a high speed dive. This released the canopy.

Without the canopy, airflow over the fuselage is disturbed. This, then, alters the effective control response, which "feels" like a loss of signal.

You already know the results.

My guess is that your wings flexed when pulling too sharply out of the dive, at probably too high a speed.
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Old 04-01-2014, 04:30 AM
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Tom is part right I suspect, I think that plane would normally fly fine without the canopy, but if flying off and then inducing a high speed stall can feel like loss of radio contact as well,, seen HSS happen many times,, When this happens most guys just don't realize they were pulling full up all the way in.

Both servos striping at the same time in flight?? Highly unlikely,, both stripping when the plane hits the ground,, common

Good luck
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Old 04-01-2014, 06:03 PM
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Yeah, I believe whole frame deformed with high G. Not enough to destroy itself, but just enough to let the canopy loose.
But, canopy coming off.... I have experienced this before. One time canopy latch was simply not the highest quality and came off on its own and while I was inverted it hit the horizontal stab as it leaves. Other than pitching issue, it was absolutely controllable.
Ah, horizontal stab got loose due to the collision, but didn't leave the airplane.
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Old 04-01-2014, 06:15 PM
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Originally Posted by scale only 4 me View Post
Tom is part right I suspect, I think that plane would normally fly fine without the canopy, but if flying off and then inducing a high speed stall can feel like loss of radio contact as well,, seen HSS happen many times,, When this happens most guys just don't realize they were pulling full up all the way in.

Both servos striping at the same time in flight?? Highly unlikely,, both stripping when the plane hits the ground,, common

Good luck
Ah, this is how to reply to a specific post. I clicked simple reply so far. I meant to reply to each person but did wrong.
Anyhow, servos didn't strip in flight. I assume they failed upon crash. I have experienced single aileron servo failures, but didn't really recognize it. I just felt rolls are quite a bit weird and non axial. Never experienced double aileron servo failures yet. If I had more time, I would have tried other channels, but again, it happened very quick.

I haven't crashed due to pilot error for about 8 years now. I doubt that I experienced HSS though.... just not sure what it feels like. Doesn't it usually happen on heavy a/c ? Besides.... I was only slightly faster. Wouldn't HSS right after a vertical dive would draw sagged arc ? I was able to do pattern style line and exact round shape.

I chat with Horizon tech support last night, and I am going to try variable load voltmeter to see how batteries react to simulated loads. I'm getting quite certain it was the battery that dropped in voltage causing the signal loss.
Whether to try LiFE or Lipo or 2 sets of batteries, etc is something I should resolve before getting back to the air.
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Old 04-02-2014, 05:10 AM
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The story of your crash doesn't sound at all like a high speed stall. HSS would cause the nose to drop or either a hard snap depending on the wing design. Your slow roll to the left with no aileron control does sound like a signal loss. If I understand you right, you were using a 2500mah NiCd or Nimh 6v battery? That should be plenty to keep the voltage up unless the battery was defective.
You didn't say if there was any damage you noticed to the wiring, or if was possible for the departing canopy to damage the wiring. The noise you heard, did it sound like balsa breaking? There is always the possibility of a random radio failure (you are flying Spektrum, after all), but I know you want to eliminate all other possibilities first before assuming that.
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Old 04-02-2014, 01:09 PM
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Originally Posted by jester_s1 View Post
The story of your crash doesn't sound at all like a high speed stall. HSS would cause the nose to drop or either a hard snap depending on the wing design. Your slow roll to the left with no aileron control does sound like a signal loss. If I understand you right, you were using a 2500mah NiCd or Nimh 6v battery? That should be plenty to keep the voltage up unless the battery was defective.
You didn't say if there was any damage you noticed to the wiring, or if was possible for the departing canopy to damage the wiring. The noise you heard, did it sound like balsa breaking? There is always the possibility of a random radio failure (you are flying Spektrum, after all), but I know you want to eliminate all other possibilities first before assuming that.
I was using a NiMH. For sometime, I have never used Nicd not because of bad experience, but because of what everyone is saying.
I doubt my battery was defective, but it was getting old for about a year with about 90 flight each lasting about 6 minutes average. It was time to change it and I was considering LiFe. Bad thing I didn't do so right away.

Wiring damage ? Not sure, but I'll check it out when I go home. I believe I pretty much kept all the wires connected.

What radio do you use ? I considered getting a Futaba, but more on not flying RC anymore and/or going back to full scale.
Full scale is my true passion but just not rich enough.
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Old 04-02-2014, 05:50 PM
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I think the loud bang was a violent aileron flutter that stripped one or both aileron servos. Hard to tell without seeing the setup.

Jester just because one uses a Spektrum does not mean that was cause of the failure. 95% of all so called radio failures are self inflicted.
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Old 04-02-2014, 06:33 PM
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Originally Posted by speedracerntrixie View Post
I think the loud bang was a violent aileron flutter that stripped one or both aileron servos. Hard to tell without seeing the setup.

Jester just because one uses a Spektrum does not mean that was cause of the failure. 95% of all so called radio failures are self inflicted.
I know exactly what you mean by "self inflicted". This guy who's a novice pilot hand launched and immediately it tip stalled and crashed.
He was a funny guy and said I know it is a pilot error, but officially it is a radio failure.

I have experienced aileron flutter on single side only on someone else's airplane, but never on mine. One time, on this airplane one of the servo gear failed.
Still, I doubt the noise was flutter since the canopy being so much ahead of crash explains it was canopy that made the noise. Two separate source of noise at exact time is unlikely (but possible).
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Old 04-02-2014, 06:36 PM
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Originally Posted by jester_s1 View Post
The story of your crash doesn't sound at all like a high speed stall. HSS would cause the nose to drop or either a hard snap depending on the wing design. Your slow roll to the left with no aileron control does sound like a signal loss. If I understand you right, you were using a 2500mah NiCd or Nimh 6v battery? That should be plenty to keep the voltage up unless the battery was defective.
You didn't say if there was any damage you noticed to the wiring, or if was possible for the departing canopy to damage the wiring. The noise you heard, did it sound like balsa breaking? There is always the possibility of a random radio failure (you are flying Spektrum, after all), but I know you want to eliminate all other possibilities first before assuming that.
Back home and checked all the wirings. Nothing seems suspicious except battery wire is slightly stripped. I doubt this stripping cause crash though.
Rather, it seems from the crash itself.

Lipo battery was totally destroyed (lucky it didn't start wild fire), motor itself seems all right, but the mount on back of the motor is badly warped.
Besides, battery wire is far from the canopy structure and I can not imagine how that canopy could have somehow dragged the battery wire.
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Old 04-02-2014, 07:34 PM
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That is truly weird. I'm officially stumped.

To answer your question, I fly with an Airtronics SD-10. I have yet to even hear about a connection issue with Airtronics equipment. The radio is fully programmable and has more switches and knobs than I know what to do with. The only things I wish it had were a module option to be able to set it up for the ultra micro bind and fly models and telemetry.
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Old 04-03-2014, 04:24 AM
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The fact that whatever the airframe was doing was stressful enough to pop the canopy off make a loud "POP" tells me the plane was under sever conditions,, not making a gentle arc pull out. Things happen under these split second events and many times the pilot see the crash differently than the observers. The HHS is just one theroy not being there witnessing, yes, it just speculation, I've see HSS and the plane just turns to mush, and I've seen it where the plane does violent snaps. every airframe reacts differently.

Hope you narrow it down, sucks not knowing why the crash happens
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Old 04-03-2014, 06:27 AM
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It's entirely possible that the canopy coming off was part of a larger structural failure of the fuselage. Of course, that would be hidden in the crash damage, so there's no way to distinguish that from what happen during the unplanned landing.
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Old 04-03-2014, 08:36 AM
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Originally Posted by scale only 4 me View Post
The fact that whatever the airframe was doing was stressful enough to pop the canopy off make a loud "POP" tells me the plane was under sever conditions,, not making a gentle arc pull out. Things happen under these split second events and many times the pilot see the crash differently than the observers. The HHS is just one theroy not being there witnessing, yes, it just speculation, I've see HSS and the plane just turns to mush, and I've seen it where the plane does violent snaps. every airframe reacts differently.

Hope you narrow it down, sucks not knowing why the crash happens
Absolutely. I have a few others to fly right away but not doing so until I get some understanding from this crash and make necessary changes.
I kinda feel like those NASA engineers who didn't launch for a few years following the explosion.

I am leaning toward battery issue, but really not sure about canopy. I was flying faster than I usually do. I am no racer in the sky at all. I tend to be the slowest flyer at the field. With new 6s, I was flying slightly faster which must have been quite slow. Contact 3DHS has been on my to-do list.
BTW, I was practicing #13 maneuver (full roll up, stall turn) on Advanced pattern sequence, and it was quite all right, meaning the shape was as planned.
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Old 04-03-2014, 09:38 AM
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I fly a Viper as a back up pattern aircraft. That thing has some huge control surfaces. I'll bet you got some aerolon flutter and that's what stripped the gears in the servos. I fly mine on 6 cells but always come down with the power off and only use full power going straight up. Sorry for your loss.
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Old 04-03-2014, 10:10 AM
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Turbo, What was the capacity of the battery pack that you used for your receiver and servos before and after the crash? Dan.
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Old 04-03-2014, 01:50 PM
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We have a few pattern planes --
from 2 meter on down -
as a suggestion on future setups:

determine maximum throws needed plus a little - and set the linkages for this much throw max-- when servos are set at about 125% throw. This maximizes power to hold servo positions.
using a lot of throw and dialing in low rates - decreases the holding power. (it's a matter of leverages.).
For batteries - we use genuine A123 1100 ma packs for pattern and typically 4 flights will consume LESSTHAN 100 ma per flight-under worst case scenario. the batts supply 6.6 volts at idle and don't drop more than 1/2 volt loaded --flying pattern - .
LiPos will do about the same IF they are 40 C .
NIMH and NiCad -are far more prone to voltage droop. even the highest C rated ones.
The chance that your issue was rx related is nowhere near a good as it being a severe power depression or plain old mechanical failure.

Last edited by rmh; 04-03-2014 at 01:52 PM.
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Old 04-03-2014, 05:40 PM
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Originally Posted by All Day Dan View Post
Turbo, What was the capacity of the battery pack that you used for your receiver and servos before and after the crash? Dan.
I am shocked. I read your post during the day and checked right after I came back home.
It only took 35mah out of 2500mah. It is only 1.4%. I checked the voltage before charging. With 600v scale dc (this was only one available on my tool), it showed 5 as a single digit. It is a 5 cell NiMH. Now I'm wondering if this 5 is too low already. I'll measure it with buddy's tool later on will post it.
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Old 04-03-2014, 05:55 PM
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Originally Posted by bafflerback View Post
I fly a Viper as a back up pattern aircraft. That thing has some huge control surfaces. I'll bet you got some aerolon flutter and that's what stripped the gears in the servos. I fly mine on 6 cells but always come down with the power off and only use full power going straight up. Sorry for your loss.
First of, I apologize to speedracerntrixie for dismissing your flutter comment. It was a good thing that I put "(but possible)".
Like I just posted, 2500mah took only 35mah when I charged it as All day dan suggested. It is still to be accurately measured, but both wing flutter cause both servos are becoming real possibility.

Is there a way to tell if the gears were damaged from crash or before ?
I doubt it, but let me know if there's a way.
I'm getting very curious about this aileron flutter possibility.

Come to think of it, when I commented one of my aileron servo stripping, it was right on this Vyper only a few weeks ago. It was back when I was still using 5s.

What servos do you use on ailerons, bafflerback ?

Loosing one plane is all right. Possibility of loosing more for unknown reasons is not acceptable.
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Old 04-03-2014, 06:04 PM
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Originally Posted by rmh View Post
We have a few pattern planes --
from 2 meter on down -
as a suggestion on future setups:

determine maximum throws needed plus a little - and set the linkages for this much throw max-- when servos are set at about 125% throw. This maximizes power to hold servo positions.
using a lot of throw and dialing in low rates - decreases the holding power. (it's a matter of leverages.).
For batteries - we use genuine A123 1100 ma packs for pattern and typically 4 flights will consume LESSTHAN 100 ma per flight-under worst case scenario. the batts supply 6.6 volts at idle and don't drop more than 1/2 volt loaded --flying pattern - .
LiPos will do about the same IF they are 40 C .
NIMH and NiCad -are far more prone to voltage droop. even the highest C rated ones.
The chance that your issue was rx related is nowhere near a good as it being a severe power depression or plain old mechanical failure.
Dialing down was one thing that I haven't paid much attention. I'll make sure I don't set it up and avoid low % ATV settings.

Vyper though was 3D plane so was using high rates as well. I have at least 3 surviving patternship so I'll check my settings.

One of my buddy suggested exactly what you said about voltage droop. I was about to switch to LiFe. But....do you know of using 2 LiFes ?
Some jet guys use 2 batteries as a redundancy. 1 into battery and another on any remaining channel. What's your suggestion on this ?
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Old 04-03-2014, 06:44 PM
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Turbo, a five cell pack is nominally 6.00 volts or 1.2 volts per cell. At 1.1 volts the cell begins a steep decline and is considered the failure point for R/C use. If you measured 5.0 volts, with a current load, your battery has failed. It may have been lower when you were flying and has recovered. Futaba has their battery fail safe set at 3.8 volts and the receiver will work down to 3.3 volts. It won’t be good but at least you will be able to land. I do not know how low the JRs or Spectrums can go before they fail but from what I hear it is not too low. Check it. It’s always a good idea to monitor your batteries capacity by using a cycler on a regular basis. Dan
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Old 04-03-2014, 07:05 PM
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Am I the only person tired of people posting JR radio bashing. It is obvious the Futaba servos did this plane in. I think we need a whole new thread on why Futaba servos are a hazard and should be immediately replaced with JR.
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Old 04-04-2014, 04:13 AM
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As you described the "banging" sound, my initial thought is the ESC. Could it have overloaded? Is it still operational?
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