[NSRCA-discussion] Lost Abbra
White, Chris
chris at ssd.fsi.com
Mon Aug 7 07:44:02 AKDT 2006
Hi Keith,
I would have to agree that I don't "Believe" Vince's problem was a NIMH
technology problem, but I had heard stories, so its better to check it
out. (I do feel that since we are only running 1 servo per control
surface and not using 3D throws.... the load shouldn't be excessive.)
I also didn't mention that I "Had" been flying NIMH on my Arresti on
the inexpensive Hydrimax 4.8v 1450 mah. I had over 250 flights getting
4-5 flights per charge on JR digitals (8611, 2-8231's, 2-3421's and the
throttle digital) . I heard about the low-impedance cells and stories
where over-demand was suspect, so I went with more capacity, lower
impedance, and 5 cells. I run NIMH in 2 TX's and 2 airplanes....
Chris White
________________________________
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Keith
Black
Sent: Monday, August 07, 2006 10:03 AM
To: NSRCA Mailing List
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 <mailto:nsrca-discussion at lists.nsrca.org>
; NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>
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
________________________________
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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