quist

My Feedback: (198)

Today my buddy was flying his 60 size H9 p-51. He is an old warbird racer and he loves to fly low and fast. He was doing hot laps with his plane today maybe 8 foot AGL when the plane rolls hard to the left and skids down the desert. He was low enough that it didn't destroy anything. The plane was going maybe 90 mph tops.

All the radio gear was fine and still functioning. the wing seperated when it hit the ground and broke in half but it was together when it hit. The ailerons are still attached and working in each of the broken halves. This was the 5th flight on the dx-7, it had 40 or so flights with the old radio.

It didn't go into lockout, the engine never cut and it was set to idle failsafe. The ailerons just went to full deflection by itself.

DX-7 with AR7000 rx. It was still in its mounting position in the fuse, the second receive was perpendicular to the main rx and about 5" away.

Any thoughts??

chrisF test pilot

None here but you might find this interesting. Sounds like they may have more problems than just the 6100.

http://runryder.com/helicopter/t339177p1/

NikolayTT

Hi,

It might prove not so bad for you but you have to ivestigate and document it properly; if I am the one who
manufature the radio I would pay you the model and also the work effort, i.e. check with the Radio-Manufacturer
and the distributors. In fact some might have been willing to pay you to not pubilish that event; but now it is too
late for - we have read about it and we have expected it to happen.

Here are some hints:
--------------------------
Sounds a lot like a getting into an Out-of-Coverage-Area, which has been big enough. With given speed and update
rate for the control sequences one could calculate how big is this area, maybe in the range of about 10x10 to 50x50
feet is what I would guess quckly. It is typical for GHz range communications, similar to mobile phones coverage
problmes, which are even very near to the base station and still can get out of coverage in some strange "spots".

This phenomena is not seen in the 27-70 MHz radio because that kind of "SPOT" there is too big and also very seldom
event due to the nature of Wave-propagation. The technical side of the problem is currently under heavy investigations
for finding stable solutions in the Mobile-WLAN communications and all kind of pocket wide-band comminicators. One
solution is so called MIMO antena (Multiple-Input-Multiple-Output) and I guess your system, what ever that is does
have One-Output and no more than 2-4 inputs(receivers), i.e. the current best Spektrum/Futaba/JR radios in 2.4GHz
are still not up to the task in all circumstances, although they have been pretty good anyway.

You have now an UNIQUE OPORTUNITY to investigate the problem and help the Community in the following manner
(I do not want to put a stress on you but you have that opportunity anyway; most of us do not have it, while we
are in fears when we will have it ... ):

1. Could you please make a Photo and a Map of the Place where this has happened with all movable and not movable
objects, people, cars etc. Distances are also critical with at least +/- one-feet-precision (about 10 inches) due to the
wave-lengt of the 2.4GHz. On the map please indicate exactly the positions of the Transmitter and Receiver. Indicating
the Temperature and Humiditiy might prove also good idea althoug it is not so critical.

2. Also, if still possible, with the remains of the plane in hands would be nice to walk on the place where the control
was lost and see if the radio works properly. Do not use Mobile-Phone that time because a FAULTY PHONE COULD
HAVE BEEN "helping" the crash, although very ulikely, or ... (read next item , it is a "scary movie").

3. Maybe you should use the same phones if someone had used that time ... Direct interference of the phone is unlikely
but if the phone is MALFUNCTIONING and the base-stations are away(pretty natural case for RC-field) then the output
power of the phone is maybe LOT STRONGER than the RC-transmitter and can "blind" the RC-receiver, i.e. so called
blocker-phenomena in GHz-ranges by 2nd or 3rd harmonics of the main transmitter standard frequency.

Some of us whose main job is well repated to those problems could even support your claim for recovering the
cost by providing you with computer Simulated Picture of the 3-D distorsion of the electromagnetic field, and
that could also help the manufaturers who are still very silent (!!!) on this topic, while they tell us how good are
the other features of the system; sure they need to tell more about the COVERAGE problems prior someone gets
even injured by RC crash.

Regards,
Nick

d_wheel

We have 2 "spots" at our flying field that affect all channels on the 72mhz band. It isn't noticed so bad when on PCM, but on PPM you get a "hit" almost every time you fly through the spots. It only lasts for a few feet, so most of us just fly on through them without worry. The first few times, however, it is quite disconcerting. So far, I have not noticed it on 2.4. It might be interesting to have a glitch counter on board and see what it reports in these areas.

Later;

D.W.

Gordito Volador

My Feedback: (1)

Might I suggest that you post here and communicate with Danny at JR/Spektrum. http://www.rcuniverse.com/forum/forumid_116/tt.htm They are very responsive.

NikolayTT

Hi D.W.

Could you post photos of the places where the signals get "lost", are those places totally empty of you have massive trees around?
It is above 100-150 MHz (i.e. wave-lenght in the range of couple meters and below) usually where those things are seen, unless in
the places you have in mind there is something condustive-alike underground. Could be any king of metal or metal-alike, underground
water etc. Well I do not suggest digging out for GOLD indeed, but you never know...(not quite a joke indeed). By the way, are there
any high-voltage lines even in couple miles away ? Are those events time-dependent, i.e. do they happen all the time or only in some
certain time intervals ? Are all your pilots always staying in the same place ? Do you have metal bars or nets to prevent visitors runing
into troubles, etc... - there could be so many things, and still at 73 MHz that is very(!!!) unusual and very unlikely to be at all the same
phenomena like at 2.4GHz, the nature of the things is very, very different.

Regards,
Nick

NikolayTT

Hi Gordito Volador,

Could you link somehow the two places for posting ? - I am not sure I know well how to
do that at this stage of the things.

Regards,
Nick

Gordito Volador

My Feedback: (1)

Nick,

The link is there in the message already.

Regards, Bill

rino

My Feedback: (121)

There is another similar post on RC Groups where a 1/4 scale Extra using a 7000 went in when the aelerons locked. I am searching for it so I can post the link here. I certainly hope this equipment gets sent in for evaluation. Ohterwise, we will won't know if there is an issue with the 7000 or not. Considering the seemingly low number of 7000 issues it doesn't seem like there is a lot to worry about though.

chrisF test pilot

Here you go.. I linked it to here.

http://www.rcgroups.com/forums/showthread.php?t=672912

wbpo

Seen this on my DX6. Appears to be RX battery related. When voltage drops below a certain rate, the RX goes out to lunch. Had it happen multiple times on an electric. Kept it up high so when it happened I could recover to reproduce the problem. Apparently it also can be effected by speed controlers and voltage regulators.

Not exactly that "locked in feel" I was looking for.

rmh

A little "rush to condemnation?"

chrisF test pilot

No one is rushing or condemning anything. He had an issue, just so happens there are others who have experienced very similar issues. Just people looking for information, I havent seen anyone bashcing anything.

NikolayTT

I agree with you 'chrisF test pilot'. There are unfortunately quite many people in RCU who just prefer typing instead of
go flying and deliver quite frequently noise-instead-of-information. They think they know everything and if faced with
something thay do not know their internal wish to tell something is pushing them to write "funny" statements which
are not funny at all, just a waste of time and rise of the number of the useles posts in RCU. And also knowing that
usually such people never learn, then it is better simply to ignore such behaviour, because when we reply then we
take the risk to cause even more noise as response to our comments, i.e. watch out what is comming ...

Also I noticed that there are smart features in RCU - how to filter out posts from certain people, that helps me
following what is going on the real discussions.

Cheers,
Nick

bronney

I don't have a spektrum but I can confirm on the "spots". I fly 40Mhz PPM here in Hong Kong, both in kai tak airport and tseung kwan o. There are 2 spots where I fly at KT that's "jammy". Apparent with first hand experience, and also by the amount of foam on the ground close to those spots. Last week I was at TKO again and again, there're slight jams at the same spot my buddy crashed his J3. Without knowing anything scientific, these spots remind me of the car radio statics when you drive into certain section of a road.

NikolayTT

Hi Bronney,

Those "spots" in case of frequencies below 100MHz might be more likely related to controlled or parasitis radio emmisions.

Controlled = Those are office or military radios which are very powerfull and can cause your radio going "blind". They are
clearly very good radios but their power causes your radio to not "hear" you, like you do not hear you friend in a Disco
where the DJ blows n x 100 Watts high quality music.

Parasitic = those could be power lines for example and especially in the top-load hours; same ffect like in the disco, but
then the DJ plays something else than music.

Both above are to great extend "covered" by PCM-radios and safe-fail features, but not totally. In GHz range those
effects are almost dashed out due to the nature of the signal codding. But then the GHz-range has its own problems.

For the GHz- range the things are more-directionally reasoned. As comparrison, when there is a strong sunshine, the
direct look at the Sun and also to some reflections from mirrors and windows might cause you at least temporary
blind-effect in certain spots of course.

Side-solution: To try to use both MHz and GHz Radios in the same RC-Plane; that is not easy but it is lot safer.

Regards,
Nick

rmh

Nick-I would be receptive to the "techno talk"-- If --it were coming from someone who is/was using the SPECKTRUM system as a model aircraft guidance system.
Theory and speculation are just that- theory and speculation.
My own background is limited to actual use of six setups in various type models .
But what the heck - ramble on --it is an open forum.
If you are using these systems for model aircraft - please accept my most humble apology.

rino

My Feedback: (121)

I would have to agree with Dick to some extent. I have a really hard time believing that the system would be released for use with all aircraft including jets and then adopted by JR, with such a huge "hole" in radio reception. In addition, you can buy the module to track whether you are loosing frames or not. That would expose this hole in reception. Anyways, it doesn't make much sense.

rmh

Yeh - my comments may pi-- off some guys but I am one who still believes the experience with a product is of more value than guesswork - no matter how well intended .
Or how much "tektalk" is provided . Lord knows I have heard plenty of that.
I am a cynical guy -- but having spent years rebuking wild $$$$$ claims in industrial accidents - I found that experience with the product is always the best approach to resolving a issue.

Rodney

I have experienced similar happenings when flying on 6 meteres. In this particular location, we had a chain link fence near the pilots station. If you stood in the right spot, you could predict where a dead area was. Some serious and extensive testing pretty well proved that this happened when the distance between the pilot and fence caused the wavefront reflected off the fence to be 1/2 wavelength off or exactly out of phase. The reflected wave was nearly the same strength as the primary wave due to the spacing and would cancel out signal received by the model. Most did not believe this until we proved it by carefully positioning equipment and aircraft position to repeatedly create the same dropout. Fortunately, it never caused a crash because you could fly through the deadzone quite quickly.

rmh

yep -multi path - was a problem we had years back with an old metal roofed barn-
so far --I have not seen that particular problem with the 2,4 Spektrum.
We also had a 6 metre problem in Las Vegas - caused by a particular commercial tower --plus use of older dual conversion JR
NO system is 100% safe against any outside interferrence -
but so far the 2.4 Spektrum is the best I have seen.
I sold all my 53 stuff -

Panzlflyer

My Feedback: (15)

Im with you there, to expect anything else shows a complete lack of real world knowledge and experience.

The other thing that springs to mind is that guys are yanking out their old stuff and re installing, Im sure the odd thing or 2 comes loose, end points dont get checked and servos bind because a new system was not as thoroughly setup as the initial one, all contributing to a dive in voltage that didnt exist before...seen it done many times.

There also seem to be a lot of people who simply wont or cant read...case in point a fellow claimed his DX didnt work (never even opened page one)and the reciever was dead, until it was explained verbally how to bind.
Do you take his crashes seriously????

Gordito Volador

My Feedback: (1)

Dick,

I agree with you. Lots of technical inuendo, not much more.

Panzlflyer,

You are 100% correct. Binding control links, stalled servos, and a host of other issues brought a lot of 72 MHz stuff down, but it was absolutely "The Radio's Fault".

Regards, Bill

Bob Pastorello

My Feedback: (198)

I was just going to suggest that NikolyaI go into the business of designing and manufacturing our systems.

Nikolay - just curious - since the DX 7 has been released (and the DX 6 before), would you share with us your experience in using these systems in airplanes?

Electriceddie

Hey Guys,

So much for all the hype of the DX-7. Sounds like they have there share of problems as well.
[>:]

Good Luck

Ed