BristolPaulL

I have a problem with an R617FS RX. A moment after takeoff the plane wing waggles and the receiver goes into failsafe mode (engine rpm drops and control is lost). This is approximately 60 yards from the TX. A bad landing results.
This has happened every flight for the last two attempts. The plane flew for several minutes before control lost before that for a total of three crashes. (An amazing airframe wouldn't you say?) In a previous incarnation, the RX was in a P47 that lost control and crashed in a similar fashion (The airframe did not survive).
Greatplanes P51
OS 46AX Max engine
4 Futaba S3004 servos
1 Futaba S148 servo
1 Futaba S136G
Hydramax ultra 1450ma battery
Hobbico retracts
Metal clevises use on retracts, all other are nylon
Futaba T7C TX
Range testing at both full and reduced TX power with engine running at various speeds was done before the last flight. Range was approximately 70 yards at low TX power and exceeded 500 yards at full power. Less through range testing was done before previous flights with no problems found.
Range testing at both full and reduced TX power with engine running at various speeds was done before the last flight. Range was approximately 70 yards at low TX power and exceeded 500 yards at full power. Less through range testing was done before previous flights with no problems found.
The antennae were carefully mounted at 90 degrees and as far from wires as possible.
The receiver was mounted on a piece of foam using Velcro in the P51 and wrapped in foam in the P47.
The receiver appears to work fine after the last crash.
I can find no metal to metal loose parts in the plane outside of the engine.
I have 5 other planes using the same TX and different R617FS receivers. They fly without incident
Can you help?

Bax

My Feedback: (11)

Is it possible that your battery pack just cannot deliver enough current to the system when the servos are under air loads? NiMH battery packs are notorious for not being able to deliver high levels of current. That would cause the receiver to quit when the electrical loads pull the battery voltage low enough that the servos won't work.

One good clue is that the entire system works immediately after you get it back following the "lockout".

Also, there could certainly be a difficulty with one of the components in the system, including the receiver. We'll be glad to examine any or all of the components involved to see what can be found.

BristolPaulL

I ground tested the system with the 1450ma NIMH flight battery and an alternate 800ma NICD flight battery. I measured the voltage on the receiver buss by inserting a Y cable in one socket and measuring the voltage on the Y cable. Both batteries were partially discharged to about 5.0 volts (no-load).
Both batteries delivered approximately the same voltage behavior. I was able to get the voltage to drop to about 4.7 volts by stalling 2 servos and also by cycling all servos while stalling one servo. I repeated the tests multiple times and extended the "on" time to as long as the crash flight lasted. The receiver did not lockout at anytime. By the end of the tests, the no-load voltage was about 4.8 volts and dropped to about 4.5 volts under stall and all servos cycling conditions on both batteries.
Do you think I should use a more sever test?
Regards,
Paul Bristol

Bax

My Feedback: (11)

Well, it's not really possible to say what the difficulty may be. If a severe test of the power system and wiring produces no faults, then the receiver may have an issue. This would be doubly-so if the receiver did not have any checkout or repairs after the first crash. Subsequent impacts could add to any damage. It's possible that the receiver is damaged such that it needs the unrestrained vibration of a model in flight to act up. A receiver that's mounted only on a small foam pad and then velcro'd or zip-tied into place isn't really protected against much at all. That could be a source of difficulty. If you cannot determine what the difficulty may be there, you can send it to us or just replace it.

BristolPaulL

I replaced the receiver, battery, servos, extentions, and switch and flew again. Only the retract servo remained. It was new on the previous crash flight. Exactly the same results occured. Control loss seems to be a distance problem, not a time related one. I took off towards to transmitter, flew past and then away. About 60 yard out the wings began to wag and control was lost.
A low power range test was done before the flight. Low power control continued beyond 80 yards.
Regards,
Paul B.

flhyr

Try replacing your switch with a heavy duty one, Maybe the vibrations are chattering the switch contacts. ( I los a plane earlier this year from this-although no way to prove it, I still believe it was the switch)

Bax

My Feedback: (11)

A distance-related problem can be caused by a difficulty in the transmitter or anything in the airborne system's installation...any component, any wiring, and particular configuration of the items. It's just not possible to tell. We can only check out the individual items and see what can be found.

TimT2000

My Feedback: (1)

We had the very same thing happen today. Everything you said is what happened to us.
We are at a loss to what is wrong at this time. Did you ever figure out what was wrong?
Was it the receiver? We lost a Tiger 60.

Tim

BristolPaulL

Tim,

I have not resolved the issue. It is not likly to be the receiver or transmitter because. Both work in other aircraft. I bought a new receiver. It did not help. I put the old receiver in another aircraft and it worked fine.

The last thing I did was to move the receiver into the rear fuse area to get it away from all other electrical and metal parts. I have not tested it yet.

Regards,
Paul Bristol

TimT2000

My Feedback: (1)

I have read that it is the servos not being able to handle the 6.6 volt LiFe batteries. I think you were using
nimhi batts though. It is so odd that the system works so well on the ground then fails as soon as you get in
the air. I want to test if loading the servos will cause this on the ground, then try a regulator. Idono what to think.

Tim

TimT2000

My Feedback: (1)

Tonight I checked the chrashed plane over again and found nothing wrong. We powered it up and range checked it again with the same good results. I did stall three servos and tested it again with no sign of control loss. We are using a LiFe battery with no regulator. The servos are all analog and a mixture of hitec and JR. This is a new radio and this was its first flight. It is a Futaba 7C with the R617FS receiver. Control did come back 3 times during the flight for a few seconds. But I could not get the plane back close to me. It seemed to get worse the farther it got away. At about two hundred feet out I lost it completely. I just do not know what to do with this radio now. Send it in? Never seen anything like this in my 30 years of RC before. I am at a loss as what to do next with this radio. The plane flew perfect
for 3 years on 72 MHz, this was its first flight on 2.4 GHz.

Tim

nonstoprc

My Feedback: (90)

How were the antennas mounted? 90 degrees apart?

TimT2000

My Feedback: (1)

Yes they where and away from other componets. One time when control returned for a second the throttle went to idle as that is where the stick was in the panic. The fail safe was set for hold or was not set, I will never do that again! I will set the throttle to go low at a signal loss. The plane went in at idle so we do have a plane that can be checked out. But I do not think it is worth repairing. This was a friends plane that he wanted me to take up and trim out for him. Sad

Cheers
Tim

crazy8s

My Feedback: (21)

Paul,
After reading all of your posts and noting all of the things you tried to do to figure out what went wrong the one thing that stands out is the "new" retract servo for the mechanical retracts. It's first flight in the P-47 resulted in the same type of "power" failure to the receiver and resulting crash as its second flight in the new plane right after take off? Was that right after you hit the retract switch to pull the gear up? A stalling high torque retract servo can put a massive drain on a 4 cell Nimh battery. That's why most manufacturers recommend a 6 volt battery for 2.4 Ghz systems in case of a situation that drains the battery. You have a better chance of avoiding a receiver reboot with a 6 volt battery than a 4.8 volt. You also noted that when you put a new receiver in that plane it still wasn't good. Still the same retract servo? And the "multiple crash" receiver when put in another airplane worked fine?? I'm just pointing out the only thing "common" to all of the situations that went on. It might be worth a shot swapping out that retract servo just for the heck of it.

nonstoprc

My Feedback: (90)

That will be good. My point is if at least one of the antennas does not see the radio wave, you will have bad receptions. From the pictures, it seems both antennas are "dangling". They should be secured.

BristolPaulL

I did not cycle the landing gear in flight so as not to have more confounding factors. I did stall servos on my test bench to see if the voltage dropped. The voltage stayed up and the receiver did not drop out when multiple servos were stalled. I did not stall the retract servo.

The issue existed before and after the new retract servo was installed. I did not change the retract servo a second time when I changed everything else.

The only common components in all flights are the mechanical retracts and the engine. Even the airframe was changed at one point.

Regards,
Paul

Bax

My Feedback: (11)

I'm closing this down. This forum is not a discussion forum. If you want to have a discussion, it must be done in the General Radios Forum.

As we've said earlier, we'd not be able to locate the difficulty here. The OP has stated that the receiver works correctly in other models, but not that one, so t here's something in that particular model that's causing the difficulty. From all the discussion, the only way to solve the difficulty would be to remove the entire system installation and start over, with new items in different locations, and have the current equipment thorougly checked.

If you want the best of all worlds, then you will have to make your tests using all Futaba equipment. Mixing and matching brands only adds to your difficulties. Futaba does not assure compatibility with non-Futaba equipment.