[NSRCA-discussion] Lost Abbra Battery
Pat Hewitt
phewitt at farmersagent.com
Mon Aug 7 08:26:13 AKDT 2006
I am sure we had a battery problem BUT it was not to loss of power BUT I think
it departed from its hold down and pulled the switch wire lose. Remember you
questioned your material a couple weeks ago and thought of chainging how you
had it. THE ONE THING WE KNOW IS WE WILL NEVER KNOW THE CAUSE. You have a good
point regarding the two new pilots we had at the fied we need to find them and
check them out.
Pat Hewitt
PS I did give you a 10 on the down line.
------ Original Message ------
Received: 11:11 AM CDT, 08/07/2006
From: "Keith Black" <tkeithb at comcast.net>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Subject: Re: [NSRCA-discussion] Lost Abbra
I've been reading this thread and I serously doubt the NiMH batteries had
anything to do with the crash. NiMH batteries aren't new on the market for
goodness sakes and they've been working very very well on probably billions of
flights. Sure we have digital servos, but in truth our loads aren't really
very high and certinally not for and extended draw.
I would think if low voltage had caused the loss of control then once the snap
stopped, even though you had little time before hitting the ground, you still
would have had enough time for the RX to come back to life. Remember, the
battery did discharge 1540 mah on the ground.
As to the servo that was locked at full throw, if this had occurred in the air
the plane would have been spiraling on it's way down and your other surfaces
would have still worked. Therefore, you can rule out the jammed servo, that
most certinally happened upon impact.
As to the IMAC guys having low impedance problems I can buy this, but keep in
mind these guys have two to three servos on each surface, their planes weigh
40 lbs, and they slam the controls like crazy doing blenders and such. The
usage by pattern planes isn't even in the same galaxy.
Most likely this was a simple case of lock-out due to reception. There could
be some other factor, but I would hate to see anyone go back to NiCADs due to
this incident.
Keith Black
----- Original Message -----
From: vicenterc at comcast.net
To: NSRCA Mailing List ; NSRCA Mailing List
Sent: Monday, August 07, 2006 7:44 AM
Subject: Re: [NSRCA-discussion] Lost Abbra
Thanks Chris,
You are right. The event was so fast. Going down hill at 45 degrees didn't
give me too much time.
I went to NiMh two years ago. Looks like I am going to go back to NiCads.
Several fellow pilots are telling me about the voltage drop problem of the
NiMh. Probably, the battery was not the cause of the crash but I think I am
going to feel more confident going back to NiCads. I went to NiMh because
they are lighter for a given capacity. I agree that there has been a lot of
comments in regard the low impedance. However, I really don't want to use
NiMh after having this problem.
I am planing to send the radio to JR for a complete check out.
Vicente "Vince" Bortone
-------------- Original message --------------
From: "White, Chris" <chris at ssd.fsi.com>
Hi Vince, very sorry to hear about your Abbra loss...not much time to
recover or evaluate the problem considering where it happened. For what its
worth, I've heard of airplane losses due to over-demand voltage during snaps .
I also hear many of the giant scale guys are using "low impedance" nimh
batteries when using nimh because of servo over-demand during certain
maneuvers such as snaps. After hearing the low-impedance story I went to
Hangtime Hobbies and am now flying their KAM 1800 6v low impedance packs.
Their site is worth a visit just for the read.
www.hangtimes.com/nobsbatteries.html
I hope you find closure on the cause.
Chris White
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From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
vicenterc at comcast.net
Sent: Monday, August 07, 2006 5:49 AM
To: NSRCA Mailing List; NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Lost Abbra
Ron,
I checked all servos but throttle and one aileron servo. All are working
on the bench fine. One of the aileron servos gears is locked in maximum
travel position and I am assuming that was caused in the crash. However, I
could be wrong.
Thanks,
Vicente "Vince" Bortone
-------------- Original message --------------
From: Ron Van Putte <vanputte at cox.net>
On Aug 6, 2006, at 9:50 PM, vicenterc at comcast.net wrote:
The battery was a little over a year old. I cycled the battery after the
crash and got around 1540 mah. It was freshly charged and I was in the second
fly. I use around 200 mah per fly so the battery was close to 2000 mah. I
always charge at C/10 and never fast charged.
I am discharging the battery now at 500 mah. I discharged the first time
at 250 mah. I will keep increasing the discharge rate to check if I find
something wrong.
I am willing to bet that you will find a bad servo. Maybe Jim Oddino or
one of the other radio wizards can explain, but a single servo can cause the
whole system to crash.
Ron
-------------- Original message --------------
From: "Scott Anderson" <scott at rcfoamy.com>
How old are the NiMh batteries... People have found the have a steep
drop off when going bad..
scott
----- Original Message -----
From: vicenterc at comcast.net
To: NSRCA Mailing List ; nsrca-discussion at lists.nsrca.org
Cc: Fred Huber
Sent: Sunday, August 06, 2006 10:19 PM
Subject: Re: [NSRCA-discussion] Lost Abbra
Fred,
Usually I called pilot (and/or mechanic) error until I find the
cause of the crash. I haven't been in this position in a very long time. I
tend to agree with you since it was clear that I didn't have control. However,
the radio is working even after such a crash. There was a comment at the field
that NiMh batteries can cause this problem. I will check the battery as much
as possible (cycle increasing the current draws) but not sure if the test will
be valid.
Thanks,
Vicente "Vince" Bortone
-------------- Original message --------------
From: "Fred Huber" <fhhuber at clearwire.com>
In that case... it may have gone to lock out just as it was
finishing the snap... rather than your control input to get out of the
rotation, the surfaces go to neutral, it over-rotates and then plays lawn
dart.
No response at all its very easy to thing failsafe lockout. Since
the engine was already at the failsafe setting, you don't have that indicator
to confirm (or refute) the lockout.
I wouldn't call it pilot error when the control input attempts you
made simply had no effect...
----- Original Message -----
From: vicenterc at comcast.net
To: nsrca-discussion at lists.nsrca.org
Sent: Sunday, August 06, 2006 7:15 PM
Subject: Re: [NSRCA-discussion] Lost Abbra
I am wrong below in regard the fail safe in regard the fail
safe. The fail safe is programmed to cut the engine and set the control
surfaces at neutral.
Vicente "Vince" Bortone
-------------- Original message --------------
From: vicenterc at comcast.net
Yes, yesterday afternoon I lost my Abbra. I was doing the 45
degree down with snap. After the snap, I could not control the plane. This is
my recollection of events:
1. I over rotated the snap for a kittle more than 90 degrees.
It was clear to me at that early stage that something was going wrong. I
snapped to the right.
2. My friend Charlie was calling for me. He also noticed and
said something to put it back in position. I told him that the plane was not
responding.
3. First reaction was to give full left to get it back
upright. The ailerons did not respond. When I realized that, I tried to take
it out of the dive by given down elevator since was pracically in inverted
position. It did not respond. It that aptitude everything goes very fast.
Finally, I tried to give up elevator but was already too late. I am aware that
I applied these control input. It was clear to me that there was no reaction.
I was able to realize that I didn't have control and I could not avoid the
crash.
4. I did not have time to do anything with rudder and
throttle. Throttle was at idle.
5. When we checked the crash site. One aileron servo was
buzzing hard. I disconnected the servo. Therefore, my first impression that
the battery flew off and it got disconnected with the force of the snap was
not valid.
6. I took the plane home as it came from the crash. I
disconnected only the ailerons servos. I checked the radio and everything is
working fine. Only two servos are not working. The throttle servo that was
practically destroyed in the crash and one aileron servo that the gears were
stripped. I believe that this was caused by the force of the impact. There was
not evidence of flutter in the ailerons before the crash or structural damage
after coming out of the snap.
7. I believe that the plane was well over stall speed after
the snap. Therefore, the plane was not in stalled condition. However, I could
be wrong.
7. I use JR all around with digital servos. PCM receiver with
fail safe programmed to cut engine and leave the servos in the last commanded
position.
8. I use 2300 mah NiMh battery (4 cells AA Sanyo). I checked
the battery voltage and was at 5.15 volts after the crash. Discharged the
battery and gave 1540 mah using 250mah rate. I am planning to cycle the
battery with higher loads.
9. It was very hot day. The plane was sitting in the sun and
it was second fly of the day around 2:00 PM. Easily was close to 100 oF.
At this point, I have to admit that has to be pilot error
since I have not been able to find a definitive cause of the crash. It is
clear that the snap initiated some kind of failure. Other pilots think that
the NiMh battery gave up at high currents during the snap and caused the
crash. I have been flying this type of battery for two years now with no
problems.
I am informing this to the group since I would like to have
your feedback. If someone had a similar problem and found the cause of the
crash, please let me know. I am going back to my backup plane (the old
hydeout). I have a brand new Abbra so need to put it together.
Thanks and have a nice day,
Vicente Bortone
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