700e/vbar CPII + Hard Deck Maiden

[rando]

I completed 3 flights with a new HD module installed on my 700e with full size vbar blueline and AR8000.

Flight 1: Preflight check reads all OK. Ground altitude shows -49ft??? Actual altitude of my flying site is ~200ft above sea level. HD did not enable in flight because the controller detected a kink in the tubing. Self leveling flight mode worked as expected. Upon landing, I removed the small tubing from the clip in the HD module and that seemed to resolve the error for the remaining flights. Apparently even the small tubing can get kinked in that clip.

Flight 2: Preflight check reads all OK. Did some ER testing to find the HD at modest angles. Found the 50' deck setting to be uncomfortably low (looked more like 30ft). I landed ad set the deck to 70' and tested a few more ERs. I don't have the POM dampers on my DFC head so I'm a bit nervous to try an ER at a large angle for fear of boom strike. I can tell from the small angle recoveries that the ER is quite fast.

Flight 3: I immediately noticed the HD altitude is now uncomfortably low again. I didn't think to go back and double check my preferences. Are these persistent or is there that much variation in the altimeter readings between flights? I tested one inverted ER. If I saw it right, it appeared to first recover to level inverted then roll to upright in two back to back steps. Was that my imagination?

Flight 4: The HD seems very low this time (maybe 20-25ft before ER kicks in). I flew around a bit, both very high and low but there wasn't much variation during the flight just a consistently low ERs. Getting nervous that something was amiss, I flipped over to the CPII off flight mode for the rest of the flight.

Other observations: The preflight check altitude reading on the ground was all over the place. I think I saw initial readings as low as -49ft and as high as 130ft. Recoveries are so fast that there is very little actual climb out. I assume if I did a very high speed dive into the HD that the climb out might be a bit more noticeable. I noticed in testing with negative collective applied, after recovery it's very easy to get a rapid decent toward the ground -- especially with the actual HD being so low for my flights. This would probably be less of a problem at proper minimum HD altitudes. Is there a way to specify the climb out altitude to be x feet above the HD?

Attached are some pics of my setup -- before I removed the tubing from the clip.

[sutty]

Not sure what's happening with your variable height rescues, but with regard to your explanation of the recovery. Check out what I said in this single post.

It wasn't confirmed if this is how a recovery happens, but I have a video of it, and it sure looks like that.

Cheers

Sutty

[rando]

Ah yes, that' exactly how it looked to me. Hopefully someone will chime in on what might be going on with by seemingly variable HD heights.

I didn't bother messing with flight angle adjustments. I noted a slight drift to the left in self leveling mode. It's close enough to level to not be a problem since I only plan to use the CPII as a bail-out, either manual or HD limit induced (depending on how consistent reliable the HD portion proves to me).

I've also tried the HC3SX as a bail out on a couple of birds. It certainly has the advantage of a substantially cleaner install but, so far, I've been unable to get the gyro portion tuned to my liking. The bail outs do work nice and quick though also.

The big advantage of the CPII is being able to pair it with the gyro of my choice. The HD capability may prove to be a nice bonus to help offset the loss of a few vbar features which are unavailable when using an external receiver.

[jdd1]

Originally Posted by rando

I completed 3 flights with a new HD module installed on my 700e with full size vbar blueline and AR8000.

Flight 1: Preflight check reads all OK. Ground altitude shows -49ft??? Actual altitude of my flying site is ~200ft above sea level. HD did not enable in flight because the controller detected a kink in the tubing. Self leveling flight mode worked as expected. Upon landing, I removed the small tubing from the clip in the HD module and that seemed to resolve the error for the remaining flights. Apparently even the small tubing can get kinked in that clip.

Flight 2: Preflight check reads all OK. Did some ER testing to find the HD at modest angles. Found the 50' deck setting to be uncomfortably low (looked more like 30ft). I landed ad set the deck to 70' and tested a few more ERs. I don't have the POM dampers on my DFC head so I'm a bit nervous to try an ER at a large angle for fear of boom strike. I can tell from the small angle recoveries that the ER is quite fast.

Flight 3: I immediately noticed the HD altitude is now uncomfortably low again. I didn't think to go back and double check my preferences. Are these persistent or is there that much variation in the altimeter readings between flights? I tested one inverted ER. If I saw it right, it appeared to first recover to level inverted then roll to upright in two back to back steps. Was that my imagination?

Flight 4: The HD seems very low this time (maybe 20-25ft before ER kicks in). I flew around a bit, both very high and low but there wasn't much variation during the flight just a consistently low ERs. Getting nervous that something was amiss, I flipped over to the CPII off flight mode for the rest of the flight.

Other observations: The preflight check altitude reading on the ground was all over the place. I think I saw initial readings as low as -49ft and as high as 130ft. Recoveries are so fast that there is very little actual climb out. I assume if I did a very high speed dive into the HD that the climb out might be a bit more noticeable. I noticed in testing with negative collective applied, after recovery it's very easy to get a rapid decent toward the ground -- especially with the actual HD being so low for my flights. This would probably be less of a problem at proper minimum HD altitudes. Is there a way to specify the climb out altitude to be x feet above the HD?

Attached are some pics of my setup -- before I removed the tubing from the clip.

Hi Rando,

Not sure why your altitude is not setting to zero or near zero at beginning of the flight. If your preflight check does not show near zero altitude then then turn off Rx and back on again. CPII HD should and needs to initialize at or near zero every time before flying. When on the ground the altitude reading will continue to fluctuate but stay with in +/- 3' to 4'. Your CPII HD install looks good in your attached pictures. I have not experienced a problem with hose pinch when using the clip one the HD module. FYI, CPII HD should reinitialize to zero or near zero foot altitude regardless of the actual ground elevation of your flight field. Also after the flight the IR programmer screen will show the highest altitudes reached during the flight. Also once the HD is set it remains in CPII memory and does not need to be reset before each flight.

"Flight 3: I immediately noticed the HD altitude is now uncomfortably low again. I didn't think to go back and double check my preferences. Are these persistent or is there that much variation in the altimeter readings between flights? I tested one inverted ER. If I saw it right, it appeared to first recover to level inverted then roll to upright in two back to back steps. Was that my imagination?"

There should not be much variation is the HD altitude between flights if CPII HD initializes to near zero ft. during preflight. On some inverted ERs you will see the helicopter preform as described above. This is normal. CPII HD does not always pick the shortest rotational distance to upright level but can at time take into account the rotational speed and direction of the helicopter at the time the HD ER triggers. This can look a little strange at times but CPII is giving negative collective pitch as long as the helicopter is inverted, so the descent will slow or change to a positive ascent until the main blades are vertical (90 degrees to the ground) then CPII will give +8 degrees collective pitch until the helicopter is level. Note CPII HD does not continue to add a full +8 degrees of collective pitch until the HD is reached but once the helicopter becomes level then CPII HD will continue to add one to two degrees of positive collective to your TX's collective pitch stick position. e.g. ER ends and you are below the HD and you have the Tx collective pitch stick at a position that would give a normal +5 degrees to the main blades then CPII HD will increase the +5 degrees to +6 or +7 degrees until the set HD is reached. Once the helicopter ascends to or above the set HD then the additional positive is removed.

"Flight 4: The HD seems very low this time (maybe 20-25ft before ER kicks in). I flew around a bit, both very high and low but there wasn't much variation during the flight just a consistently low ERs. Getting nervous that something was amiss, I flipped over to the CPII off flight mode for the rest of the flight."

It is not uncommon for the altitude detection to vary +/- 10 feet, so the HD may not trigger until the helicopter is 10' below the set HD. Also the momentum of the helicopter in the descent will effect the lowest altitude the helicopter will reach during a HD ER.

Hope this helps,
Jack

[rando]

Thanks. I'll make a careful note of the pre-flight altitude readings to make sure they baseline near zero now. I definitely saw readings of NEGATIVE 40-50 ft in my maidens which I guess would explain why my 70ft HD actually looked between 20-30ft.

I guess the question remains, why would I be getting those negative readings on the ground? I powered the electronics directly from the take-off position without moving the heli. It was a relatively calm day. Perhaps one of the FMA guys will chime in.

[nightflyr]

First thing to check is that the tube is free from any sharp bends.
Also that the static streamer holes are not blocked.
BTW did you happen to use any CA to attach the tube to the HD module?
If any vapors got into the module, this can be a very bad thing.

[rando]

There are no sharp bends in the tube. The holes in the streamer are open and clear. I used CA on the joints between the streamer and metal tube and as well as the metal tube and flexible tube up front. I did not use CA at the joint between the tube and HD module. The HD module was disconnected from the tubing during CA application and curing at the other joints.

[nightflyr]

By chance.. was there any wind?
Not that it should make a major difference.

[rando]

It was a relatively calm day, ~5mph winds.

[nightflyr]

I would try initializing your electronics with the CPII & HD completely powered off (autotrim set to 0)
Once the VBar and Rx are up and running then power up the CPII and HD and see what readings you get

[rando]

Originally Posted by nightflyr

I would try initializing your electronics with the CPII & HD completely powered off (autotrim set to 0)
Once the VBar and Rx are up and running then power up the CPII and HD and see what readings you get

Autotrim is set to zero or I'd likely have a whole different set of issues to report. How would that relate to the altitude readings in any case?

Looking at how the CPII sits between the receiver and vbar, it's not exactly strait forward to "power up the receiver and VBAR" without the CPII getting power. The CPII draws power from its connections to the receiver and the VBAR from it's receiver/CPII connections. You're asking me to pull all of the CPII inputs (RCVR1..3, ON/OFF) and then re-attach them once the vbar and receiver are up? Are you suspecting a brown out/power rail glitch is futzing with the CPII/HD boot?

[rando]

I just did some bench testing of the initial altitude reading upon powering up my flight electronics. All tests were performed in-doors, HVAC off, windows closed, about as close to zero dynamic pressure variation as I can create in a non-lab environment.

Power Cycle 1: -51ft, fluctuating +/-5ft. Touching plumbing or sensor causes some additional large fluctuations (50-100ft). I next removed the plumbing from the HD sensor and the reading jumped to +48ft.

Power Cycle 2 (plumbing removed): ~4ft, with fluctuations +/-5ft. I lightly tap the HD sensor and reading jumps to 150ft and then settles at -52ft with +-80ft fluctuations.

Power Cycle 3 (plumbing removed): -50ft with large fluctuations (as high as 150ft). After 30-60s this settles down around 4ft with +-40ft fluctuations.

Do the inconsistent power-up readings, large fluctuations and sensor sensitivity to minor vibrations indicate perhaps a defective HD sensor?

[jdd1]

Originally Posted by rando

I just did some bench testing of the initial altitude reading upon powering up my flight electronics. All tests were performed in-doors, HVAC off, windows closed, about as close to zero dynamic pressure variation as I can create in a non-lab environment.

Power Cycle 1: -51ft, fluctuating +/-5ft. Touching plumbing or sensor causes some additional large fluctuations (50-100ft). I next removed the plumbing from the HD sensor and the reading jumped to +48ft.

Power Cycle 2 (plumbing removed): ~4ft, with fluctuations +/-5ft. I lightly tap the HD sensor and reading jumps to 150ft and then settles at -52ft with +-80ft fluctuations.

Power Cycle 3 (plumbing removed): -50ft with large fluctuations (as high as 150ft). After 30-60s this settles down around 4ft with +-40ft fluctuations.

Do the inconsistent power-up readings, large fluctuations and sensor sensitivity to minor vibrations indicate perhaps a defective HD sensor?

Hi Rando,

Based on the bench test you preformed I am in agreement with you. There is no way you should be getting those readings. The HD module appears to be defective. Why don't you give Howard a call at FMA. Phone # (301) 798 2770

Jack

[rando]

Thanks. I assume that the phone call will need to be after Christmas.

[rando]

OK, my replacement HD module arrived just now. A quick power up on the bench and the altitude readings are toggling from 0-1ft. I pinched the hose and the reading dropped to -460ish ft and held until I let go. It immediately returned to 0ft. It looks to be working right now --- next step some more flight testing.

Thanks to the FMA crew that helped in the testing and replacement.

[jdd1]

Originally Posted by rando

OK, my replacement HD module arrived just now. A quick power up on the bench and the altitude readings are toggling from 0-1ft. I pinched the hose and the reading dropped to -460ish ft and held until I let go. It immediately returned to 0ft. It looks to be working right now --- next step some more flight testing.

Thanks to the FMA crew that helped in the testing and replacement.

Hi Rando,
Great!!! Things look correct now. Suspect flights will perform as expected now. Let us know how it goes.
Jack

[rando]

I put in 3 flights today and the CPII + HD worked perfectly as did manual ERs. The replacement module resolved the issues I experienced before. Recoveries were quick and always seemed to occur at about where I expected them to.

Because I never approached the deck at a very high speed, the climb out portion of the recoveries was so quick I had to pay close attention to see it at all. It was easy to hear on my setup as there was one blade fart from the rapid leveling and another for the quick punch out. I have pitch pump enabled in the vbar which I think might exaggerate the climb-out (as well as the return of control to the pilot).

The 50ft minimum deck is probably a few feet higher than I'd like on a 700 size. For anything smaller, I think it would much too high for my tastes. Perhaps FMA will include a safety override in a future release -- you know one of those, "Are you sure? Are you really sure? Go back now! Don't do this! Do you still want to proceed?" kind of prompt sequences. The manul ERs seem to work just as good as those on the HC3SX. Of course with the CPII, I get to keep the vbar which is a plus IMHO.

I'm not particularly fond of all the extra wiring or having to give up vbar bank switching and gyro gain control from the TX. I'm also a bit concerned about the long term reliability of the static streamer. Hopefully a future altimeter module can give the required performance without the need for the plumbing. Also a cool idea for a future Copilot would be to allow it take satellites as well as present itself as a satellite as that would allow a cleaner hookup to FBL systems and (in the case of vbar) potentially preserve their full access to all available channels.

[rando]

I lowered the pitch pump in vbar and it seems to have lessened the harshness of the recoveries a bit. I know other gyros have similar collective acceleration features -- something to look out for when doing your setup.