Dear Customer,

You are receiving this notice because our records indicate that you purchased an airspeed sensor from 3D Robotics. Our ongoing product testing has turned up a rarely occurring issue that can cause poor performance of the airspeed sensor.

There is no further action required if:

You are not using an airspeed sensor with APM 2.5
You are using an APM 1.0 or APM 2.0

When using the APM 2.5 with a telemetry radio and GPS, the current draw of these two devices may cause inaccurate airspeed sensor readings. An immediate fix for this is to disable the airspeed sensor in the Mission Planner.

For those who do need to use the airspeed sensor along with GPS and telemetry radio, and are affected by this issue, you can return your APM 2.5 to us so that we may replace a single component on your board and remedy this issue entirely.

We will do this at no cost to you. Simply reply to this message, and we will issue you a return merchandise authorization (RMA) with instructions on shipping your APM 2.5 back to us.

We apologize for any inconvenience this may have caused you and look forward to continuing to provide you with the best quality autonomous products at the most affordable prices.

The 3DR Team

if the problem is real is what it is and how to fix it yourself?

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Replies to This Discussion

i powered the RD900 via ESC's BEC . Now the airspeed sensor is giving correct readings. no problem at all. earlier the airspeed readings were jumping wieredly even when speed was zero. thanx all for such a simple solution to a serious problem. excessive electrical load on APM2.5 can even reboot it while in flight. so i ma not sending my APM2.5 for fuse replacement.

There is a better solution, use a decent 5V UBEC, connected to the Input header with JP1 removed, assuming you are not using a Power Module which also goes through the fuse and diode.

Using a 5V UBEC on the Input headers you will not have the diode and fuse in series so you will have to be more careful not to connect the UBEC reversed.

The diode and fuse "protection" act as a de-regulator.for VCC supply.

Using a 5V UBEC connected to the Input headers improves the accuracy of analogue readings such as Current and Voltage by a factor of 10.

Full details at the 2 links below

With the new fuse, it's an order of magnitude lower in resistance, so the UBEC accuracy argument becomes irrelevant with a fixed board or the APM2.6+. And the accuracy is only effected if current pull is changing by a large amount. Like with the RD900 Radio. Otherwise, with automatic voltage reference calibration, is not really a concern if it's 4.8V or 5.0V on Vcc. For most users the ease of use of the Power Module outweighs using a separate BEC.

A PM that could accept a 50V max voltage would be a great evolution, and a better connector (or onboard like the PX4 would also be good)

I have replied to this RMA 4 times, the first on 4th June. All my emails have been ignored. Is that happening to anyone else?

I am especially annoyed by the delay, because I noticed this issue well before the RMA was announced. I use airspeed sensor, GPS, Power Module, MinimOSD, RFD900. I originally powered the other devices from external supply to overcome this, but now that the RMA was announced, I want it fixed!

What is the status, and why have my 4 replies to the original email, and additional emails to the "help" address been ignored for this long?

Please, some feedback!

PS: I did lose a plane due to this issue before my temporary fix - my receiver was powered by the glitchy output rail too, which didnt like the voltage fluctuation, occasionally causing a random PWM on a channel... sometimes the mode channel... you can imagine the confusion that happens with a random mode change at low altitude. Well, it also could have been a reboot or an airspeed fluctuation causing the unexpected mode change. I also lost a bunch of servos before I fixed it, due to the PWM glitching. :(
You can see I blogged about this to warn others back in Jan, Apr and May: #1362
Has anyone successfully arranged a voluntary RMA and had their APM 2.5 repaired? Or has it been standard that the request is ignored?
Andrew, we've been processing loads of these - sorry to hear that there was a problem with yours. PM me with your name and order details and I'll find out why yours didn't go through.

Andrew.. It took a few emails back and forth but I have a shipping label to send mine back to 3dR. I'll be sending mine back on Monday. 

Ok, good to know it's happening.
Thanks Chris. It's been tough having a UAV grounded for so long waiting for a response, let alone begin the RMA turnaround period...

Has anyone else sent their board in yet? I sent mine in via the FedEX Returns system Thursday June 20th and it arrived at 3DR on Thursday June 27th. I didn't expect it to take that long in transit; I.m on vacation this week and had hoped to do some flying. When the email said 3-5 days I had expected it to take a week to ten days total with shipping.......well shipping took a week, so I'd like to know what others have experienced. Has anyone gotten their board back yet, and if so how long did it take?


Nathaniel ~KD2DEY

I sent mine in on Thursday and it arrived on Friday (I live in San Diego). I'm anxious to know the turn around time on the fix.

I'm on the East coast :(, so it took mine longer. Can't say I'd have gotten any flying in anyway, we've had record rain here in May and June. Let's hope July is dry!

Post here when you get your board back. I hope it doesn't come back via the same slow ground method, I would gladly pay to have it come back via USPS priority mail; then at least I'd have it in two to three days instead of a week!


Nathaniel ~KD2DEY


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