sudden dive

[erhard52]

i wonder if anyone has a possible explanation for the following model behavior with nano receiver.

first time i crashed a larger glider 6 years ago the following way: i did i range test as recommended and forgot to remount the transmitter antenna. nevertheless i flew on a slope and the plane flew beautifully but then went into a sudden dive, i obviously pulled the elevator but nothing happen and just before crashing it recovered. oh i thought what was that and kept flying and it happened again, same thing it recovered. no i thought oh i better land. so i flew a larger loop behind the hill made a turn and the plane flew towards me ready for landing and suddenly when into a dive again and crashed. 
obviously i blamed the missing antenna. i am not sure how fail safe is set but when i just turn off the transmitter all servos stay where they are. 

second time just 1 week ago: another glider, flying happily and same dive behavior and plane luckily recovered. i thought it was maybe a down draft in the hills but way would it go in a real dive as if pushing down the elevator? after inspecting the plane i thought i found an issue with a lose vtail mount which allowed the vtail to slide along the fuselage. obviously nit good, so i fixed it thought that was it and following 5 flights or so where fine.
today i flew again and again the sudden dive happened and luckily i could recover just before crashing.

so what can this be?
down drafts don't seem to really explain the sudden dive
losing RC link should leave the servos in place and not cause the dive

any ideas what be great because it makes me very uncomfortable 

btw: transmitter is a multiplex EVO 16 with XPS RF module

thanks
erhard

[XPS]

If the failsafe is set to HOLD all positions then it is not possible for the servo itself to move on its own if there is a loss of radio control. That would leave either a problem on the transmitter side - pot glitch, encoder glitch, module pin failure (especially for Futaba transmitters - EVO's are not known to have any issues with the module pins), or a servo/power/mechanical issues on the aircraft. Did you look at the LED on the Nano when this happened? The LED will blink if there was a loss of power. We have seen cases where fast power glitches can cause servos to move to one end, especially analog servos, but the servo signal returning immediately corrects this. The power glitch can occur with just a single servo when the connector makes poor contact. Remember, servo connectors are only good for about 25 insertions/removals before you are suppose to throw them away and use new connectors.

Let us know about the LED on the Nano.

[erhard52]

If the failsafe is set to HOLD all positions then it is not possible for the servo itself to move on its own if there is a loss of radio control.  That would leave either a problem on the transmitter side - pot glitch, encoder glitch, module pin failure (especially for Futaba transmitters - EVO's are not known to have any issues with the module pins), or a servo/power/mechanical issues on the aircraft.  Did you look at the LED on the Nano when this happened?  The LED will blink if there was a loss of power.  We have seen cases where fast power glitches can cause servos to move to one end, especially analog servos, but the servo signal returning immediately corrects this.  The power glitch can occur with just a single servo when the connector makes poor contact.  Remember, servo connectors are only good for about 25 insertions/removals before you are suppose to throw them away and use new connectors.

Let us know about the LED on the Nano.

thanks so much for the reply. sadly yesterday it went into a dive again and did not recover. entire front part crashed but could be repaired. but no fun really. 
i forgot to check if the receiver was blinking , indicating a power outage. i tried to use the XDP to check the failsafe settings in the nano receiver but cannot install on w11 PC so far.

what i do now is switching to spectrum system - just needed to order a receiver - i will fly with that setup and if it dives again it is not XPS.

i use my multiplex evo 12 transmitter with a XPS 2.5GHz RF module which i thought usually works but then again it gives my these sudden dives .
to check the failsafe i turn the transmitter off and all servo stay where they are - 
i did a range test with reduced power and all servo stay where they are 

i just cannot reproduce erratic servo behavior. also i tested the system with the same battery after the crash and never could introduce a power loss even with running motor.

i simply have a problem to explain this behavior with aerodynamics but it is little bit gusty  in the hills but i have seen the dive in quiet conditions too.

this time i use a vtail glider - when it had crashed the elevator was all in neutral condition.

when i fly again i will try to produce a stall higher up and a controlled dive to see how long it takes to recover

the failsafe takes about 2 sec to recover which is the default setting as for as i am reading

other question:
do people still fly with XPS or they all moved on?

last question
way back i bought a spectrum DSM2 module for the hitec transmitter, i wonder if i could use this also for the EVO 12 - does it only need the PPM signal line to be connected to the RF module.

or maybe it is time to move to a new system - i must say the EVO 12 is a very flexible nice transmitter and i hate to give it up

and where is all the XPS community chatting these days or are you and me the only one left?

thanks
erhard

[XPS]

The amount time before entering failsafe can be programmed. 2 seconds is the default. As soon as the signal is available failsafe is exited.

Again, failsafe set to HOLD will not change the servo positions while a failsafe is occurring. A failsafe set to USER DEFINED will hold the failsafe at whatever positions you have deliberately set them to. You should be setting the failsafes to some known position. We typically recommend slight up elevator, and either slight left or right rudder. Failsafe is not designed to save an aircraft - it is designed to give you predictable flight path where you can determine where a loss of radio control impact will occur so that people can be moved.

We are still selling products, and doing upgrades and repairs, so people are still using XPS radio systems.

[erhard52]

thanks again for the reply. 
yes i understand the failsafe settings. 
it would be nice to have also an indicator light if failsafe was invoked after a flight



it seems the XDP program cannot be used in win11. missing dll etc 
FTD2XX.DLL missing

when starting XDP in w11

also the USB driver could not be installed - any ideas.

glad you are still taking care of your customers

in the next days i will explore the spectrum DSMX system with the plane and see what happens

erhard

[XPS]

That is the driver from FTDI. You will need to download the latest drivers from there website here:

https://ftdichip.com/wp-content/uploads/..._Setup.zip

[erhard52]

That is the driver from FTDI.  You will need to download the latest drivers from there website here:

https://ftdichip.com/wp-content/uploads/..._Setup.zip

i did and installed it successfully but same error. looks like i need this dll

[erhard52]

That is the driver from FTDI.  You will need to download the latest drivers from there website here:

https://ftdichip.com/wp-content/uploads/..._Setup.zip

i did and installed it successfully but same error. looks like i need this dll

i have a bunch of those in the system - where does it need to be in?

[erhard52]

That is the driver from FTDI.  You will need to download the latest drivers from there website here:

https://ftdichip.com/wp-content/uploads/..._Setup.zip

i did and installed it successfully but same error. looks like i need this dll

i have a bunch of those in the system - where does it need to be in?

ok it started up - i copied the file to the x86\xps directory - now i need ot find my xpd device

[erhard52]

That is the driver from FTDI.  You will need to download the latest drivers from there website here:

https://ftdichip.com/wp-content/uploads/..._Setup.zip

i did and installed it successfully but same error. looks like i need this dll

i have a bunch of those in the system - where does it need to be in?

i don't see to be able to find my XDP programmer - are there still some available?