Featherweight Raven altimeter help - both apogee and main fired at same time!

[colbon1]

I had a strange problem from my flight over the weekend of my upscale Estes Skywinder and seeking help (as no response yet from Featherweight/Adrian) so I thought I'd see if others can shed light on this.

The altimeter was programmed for apogee deployment of drogue (helicopter blades in this case) and main at 800'AGL. When it reached Apogee, both main and apogee charges wrongly fired. I confirmed this both from the Raven datalog as well as the onboard video.

At apogee, the blade charge fired (Volts Pyro Main), pushing the piston forward to deploy the blades. At the same time, the barometric altitude goes haywire and it falsely fires the 2nd event about .1 seconds after the first event, instead of waiting to 800' (Volts Pyro Apogee). Here's the image from FIP. It's a bit hard to see but there is a +16G acceleration when the first charge goes followed by a -30G (I assume from when the blade release piston bottoms out). Did this shock cause the baro sensor to give a wrong altitude (-500 ft), causing it to fire main? About a second later the baro fully recovers and gives a normal altitude reading. Any suggestions on how best to program this to avoid such problems, add a delay as well?? I just used the default menu pulldowns for "At Apogee (baro)" and for "At Low Altitude" to program the events.

Event 1 (apogee) - programmed to "main" pyro channel output to fire at apogee (baro altitude descending)
Event 2 (800 AGL) - programmed to "apogee" pyro channel output to fire at 800AGL
Raven 3, April 29, 2012 firmware build

Any help appreciated!
-Glenn CB TRA 4172 L3

 

[Buckeye]

Looks like you have apogee and main settings reversed.

 

[colbon1]

Hi Buckeye,
Yes they're intentionally programmed reversed due to the av bay orientation in this rocket, but still the charges shouldn't have both fired at once.
-Glenn

 

[dvdsnyd]

Nevermind

 

[dvdsnyd]

Please post your FIPa file

 

[colbon1]

Here is the FIPa file with the datalog from the flight.

 

[kjs]

Was your piston and apogee charge such that it would have pressurized the Raven itself? If so, best solution I think would be to avoid that if possible (isolate the Raven from the charges/pressurization). Otherwise *maybe* (?) you could use the 'flight time > TVAL' to put in a delay past blade deployment...

But it does look like the baro got pressurized enough that it met the criteria for < 400 fps, pressure increasing (a lot) and < 800 ft AGL (based on the pressure spike.

Actually, if you select those bit flags in the graphics, you can see that the three are 'true' during that baro transient:

 

[colbon1]

Thanks Kevin for that hint - I bet it did get pressurized. I had to use a pretty hot charge to blow the 2 shear pins (2-56) and it's a 54mm x 36" chamber. Also I didn't install the O-rings in this av-bay which I normally use to prevent blow-by pressurization. I'll do some ground testing to reduce the charge a bit and add the o-rings to prevent blow-by. In addition, looks like it would be a good idea to add the flight time > Tval lockout just in case until I have flight data to prove the problem is "cured". Really appreciate your help!

 

[kjs]

Thanks Kevin for that hint - I bet it did get pressurized. I had to use a pretty hot charge to blow the 2 shear pins (2-56) and it's a 54mm x 36" chamber. Also I didn't install the O-rings in this av-bay which I normally use to prevent blow-by pressurization. I'll do some ground testing to reduce the charge a bit and add the o-rings to prevent blow-by. In addition, looks like it would be a good idea to add the flight time > Tval lockout just in case until I have flight data to prove the problem is "cured". Really appreciate your help!

Happy to help! And thank you for uploading the FIPa file! (And I haven't used those bit flag graphics in a long time so was happy to remember they were there!)