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Under a steel bridge
1665 8 2015-5-13
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hjf
lvl.1

United States
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My excuse for buying my Phantom was that I could utilize it in my work doing structure inspections (FAA regs notwithstanding.)  One of the first projects will be an inspection of concrete bridge piers beneath a section of interstate highway.  I feel competent to control the aircraft in close proximity to the piers; and I've installed prop guards just in case, but I have a few questions for which I'd appreciate the collective wisdom here.

1.  Failsafe - If for some reason the aircraft enters failsafe mode, does it ascend to 60' before returning to the home point?  I ask, because if I am under the bridge, I do not want the aircraft to crash upward into the bottom of the bridge.

2. Compass - While I will calibrate to compass well away from the bridge, is it possible that flying in close proximity to large steel beams will result in any loss of control?

3. GPS - Again, the aircraft will acquire GPS signals well away from the bridge, but is it possible that flying close underneath an interstate hignway bridge will negatively affect the GPS connectivity to the point of loss of control?  FWIW, I will be controlling the aircraft from almost directly below with visual contact, so I do not expect to need GPS, but in the event of interrupted communication with the controller, I want the aircraft to know where it is.

4. Height protection - The blade guards should protect me if I drift laterally into contact with the piers; but is there a mechanical or programmable means to prevent contact with an overhead object (such as a bridge beam)?

2015-5-13
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adrianjacobs
lvl.4

United Kingdom
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sounds like you need a P3!

1.  You can set the height that it'll go to before returning home.  If you set it low, it will not go down before returning home, but will stay at the same height it's at and return home.  Any low beams could be a problem.
2.  Yes it's possible that the compass will suffer but shouldn't be a problem unless flying in ATTI or course lock mode
3.  Again, yes, the bridge can (will) cause GPS issues.  Flying in ATTI will help, but then any compass issues will cause problems.
4.  Buy a P3.  Or you could set the height limit but to my experience, it's not terribly accurate.

all this assumes you're flying a P2V+ in Naza mode (and all to the best of my knowledge).
2015-5-13
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hjf
lvl.1

United States
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Thanks for the feedback.  Yes, NAZA mode.  Alas, I just bought the P2V+; a new P3 is not in the budget.

You confirmed my expectations re: GPS & compass influences.

I did look at setting the RTH altitude, and its minimum setting is 66 ft.  Alas, I guess I'll just have to be extra cautious when under the bridge.  Tx.
2015-5-13
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Barney Rubbel
Captain
United States
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I was concerned when flying under a big metal bridge as well, mostly because of the RTH issue. I was afraid the bridge would possibly disconnect the transmitter and then crash into the underside of the bridge while trying to go home (my RTH is 200' because of trees). I did some testing since there was land on the side of the lake/river that I could still walk along. As I flew my P2V+ under the bridge, I did lose a few satellites, but still had enough to fly in GPS mode (started with 12 and lost 3 so I still had 9). I can't imagine that the bridge would not cause some confusion for the compass? I made sure to fly in ATTI mode and kinda "whoosh" on thru, but if you need to stay still under the bridge to take pictures or video, I'd keep an eye on that satellite count.
As another thought, if you can make 'home' be 66' below the bottom of the bridge, you'll be safe even in RTH.  Just my 2 cents.     Barney
2015-5-13
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buddhabelly
lvl.1

United States
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Maybe I'm missing something.  Seems to me if you're going to be flying UNDER something to inspect it wouldn't you want the camera to be on the top of the quadcopter so it can look UP?
2015-5-16
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stock12to32
lvl.4

United States
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I have flown under huge steel bridges and was ok for the most part. I usaly stay about 15 feet away from any part of the bridge. There has been a few times while under the bridge my sat count went to 5-6 and the Phantom automatically switches to alti mode but i was allways aware of it and had no problem with the flight.
I have not tested flying closer then 15 feet and you have to make sure you are aware when it switches to alti mode because of wind going under the bridge can be strong and it will push the phantom in the direction it is blowing. Once it comes out from under the bridge it will regain sats and continue to fly. I would make sure you are close enough to allway see the lights on the phantom so you know what mode your in. The lights are faster at telling you it switches modes then the app and somtimes it can go from 10 sats to 6 right when you go under.
2015-5-17
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JtrJr-Droner
Captain
Flight distance : 4341 ft
United States
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stock12to32 Posted at 2015-5-17 19:43
I have flown under huge steel bridges and was ok for the most part. I usaly stay about 15 feet away  ...


Stock,

Have you figured out whether you can pop up on the other side of the bridge? I really wanted to try it on a large, less traveled concrete bridge here but I can't figure out (in my head) how I'm going to get it up and over on the other side. I can go under and back under to return but it'd be sweet if I could somehow come up on the other side. You're dead-on about the lights, they seem to switch very quickly to let you know when ATTI kicks in.

Jerry
2015-5-17
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stock12to32
lvl.4

United States
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JtrJr-Droner Posted at 2015-5-17 22:38
Stock,

Have you figured out whether you can pop up on the other side of the bridge? I really want ...

The bridge I have gone to goes over a lake and I stand below it on one end so I have not gone through and up to the point where I lost line of sight. I think I would have to have one of my "nerves of steel" days before I would try it.
2015-5-17
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JtrJr-Droner
Captain
Flight distance : 4341 ft
United States
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stock12to32 Posted at 2015-5-18 08:17
The bridge I have gone to goes over a lake and I stand below it on one end so I have not gone thro ...

Yeah, I hear you! I'm just wondering if I could just flip it into ATTI shoot under and through the bridge and at the very end hit the ascend full up, pop it back to GPS at the last second and head back up to the top of the bridge. It'll have to be a nice, calm, "nerves of steel" day for sure. Now that I've got the P3, maybe I'll get one of those days!

Jerry
2015-5-17
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