[NSRCA-discussion] Lost Abbra
White, Chris
chris at ssd.fsi.com
Mon Aug 7 03:48:16 AKDT 2006
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
________________________________
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
<mailto:nsrca-discussion at lists.nsrca.org> ;
nsrca-discussion at lists.nsrca.org
Cc: Fred Huber <mailto:fhhuber at clearwire.com>
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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