Flying under bridges

m0j0 · Dec 12, 2018

Guys -

I'm curious. How many of you routinely fly under bridges? Do you have issues doing that? I would expect there would be GPS loss. Any other issues flying under or through structures outside. I you have videos please share them. Thank You

Just_nick · Dec 12, 2018

Depends on what kind of bridge you're talking about. And how wide it is. The wider it is, the larger the chance of a disconnect or a GPS error. Both of which can bring your drone down. A short flight underneath a narrow bridge is not going to be as bad as say trying to fly under a four-lane bridge crossing the Mississippi.

calmar81 · Dec 12, 2018

I personally have not flown under bridges yet. But I think a bridge is too narrow to cover so many satellites, that this could be a problem. At least if you do not fly too close... Satellites are distributed over the entire sky and are in different angles, aren’t they?

Mossiback · Dec 12, 2018

There are a lot of crash videos on YouTube. The first thing that is likely to happen is a loss of GPS. You can still fly but it will tend to drift. The next problem is a disconnect to the RC causing RTH to kick in. Even with RTH set to hover it will drift with the breeze until it hits something. Of course this all depends on the size and type of bridge.

waylander · Dec 12, 2018

Hi Guys

I have flown a zig zag pattern around all the arches of this viaduct at a slow speed, without loss of signal.

You can't tell from the perspective but the Span is about is about 50 feet wide and 30 foot deep and 100 foot high ( at Highest point ).

Waylander

m0j0 · Dec 12, 2018

Mossiback said:
The next problem is a disconnect to the RC causing RTH to kick in.

That should not happen in most cases if you have an unobstructed path between the TX and the UAS. GPS loss and the associated loss of position lock would be anticipated in most cases of the bridge is wide enough. TX disconnect should not occur unless there is an obstruction between the TX and UAS. I have been flying a long time... Never flown under a bridge but I am curious as to how it would react.

I like learning from others mistakes not my own ; )

m0j0 · Dec 12, 2018

waylander said:
Hi Guys

I have flown a zig zag pattern around all the arches of this viaduct at a slow speed, without loss of signal.

You can't tell from the perspective but the Span is about is about 50 feet wide and 30 foot deep and 100 foot high ( at Highest point ).

Waylander
View attachment 55794

I would think in this photograph you could navigate through those spans without too much issue. As long as you fly in the middle (Top to Bottom) you should still have GPS.

m0j0 · Dec 12, 2018

This in my opinion is pretty sketchy ...

Likely to have GPS loss and possibly TX disconnect if your are not in the right position.

swooshdave · Dec 12, 2018

Y'all act like as soon as you lose GPS the drone plummets to the ground.

Gr8ful · Dec 12, 2018

I flew under the Mackinac bridge pre 911 in a 1940 Taylorcraft.

m0j0 · Dec 12, 2018

swooshdave said:
Y'all act like as soon as you lose GPS the drone plummets to the ground.

No I have flown RC, losing GPS wouldn't bother me at all especially under a bridge where the wind is reduced. - But a TX disconnect could be bad under a bridge. Would be a good idea to change setting to Hover on disconnect.

The bigger challenge here isn't the loss of GPS its the loss of connection with the transmitter.

Mossiback · Dec 12, 2018

Mossiback said:
...The next problem is a disconnect to the RC causing RTH to kick in...

m0j0 said:
That should not happen in most cases if you have an unobstructed path between the TX and the UAS...

You are correct. A RC disconnect should not happen if you are in VLOS. However the OP was asking what problems could happen and and that is one of the major ones. Some people do not maintain VLOS and cannot resist the urge to fly under a bridge.

Kilrah · Dec 12, 2018

I remember a thread where the guy had an RC loss and hadn't changed the failsafe setting. Not sure he had been careful to place himself appropriately to keep LOS though. Reliable picture transmission makes you confident and looks all good initially, but 3m thick brick can ruin that pretty quick.

swooshdave · Dec 12, 2018

This was me flying under a couple wooden bridges. Pucker factor was high as I obviously lost sight momentarily. I guess I should get reported to the FAA for no VLOS.

Chip · Dec 13, 2018

waylander said:
Hi Guys

I have flown a zig zag pattern around all the arches of this viaduct at a slow speed, without loss of signal.

You can't tell from the perspective but the Span is about is about 50 feet wide and 30 foot deep and 100 foot high ( at Highest point ).

Waylander
View attachment 55794

Fantastic location! How old is viaduct, ancient Roman?

waylander · Dec 13, 2018

Hi Chip... the Viaduct location is in the north of England, it is a railway bridge which when built carried the Great Northern Railway and was opened in 1883. It's name is Hewenden Viaduct and it is near Cullingworth, West Yorkshire.

Regards Waylander

Congoblue · Dec 13, 2018

That brings back memories - I used to live near it, we played on top as kids. Very dodgy as there were open shafts that went right down the towers.
It's been disused since 1960's then was converted into a cycle track about 10 years ago.

clovis09 · Dec 13, 2018

waylander said:
Hi Guys

I have flown a zig zag pattern around all the arches of this viaduct at a slow speed, without loss of signal.

You can't tell from the perspective but the Span is about is about 50 feet wide and 30 foot deep and 100 foot high ( at Highest point ).

Waylander
View attachment 55794

Beautiful.

Aussie Oldtimer · Dec 13, 2018

m0j0 said:
Guys -

I'm curious. How many of you routinely fly under bridges? Do you have issues doing that? I would expect there would be GPS loss. Any other issues flying under or through structures outside. I you have videos please share them. Thank You

Early on, i flew under a single rail bridge and was 'attacked' by a flock of swallows'. no loss of control though