Suppose a pilot is flying VFR with excellent visibility and calm wind but with a ceiling of 1000, along a wide river at 500 feet. At some point she approaches a suspension bridge. Climbing and trying to cross in between pillars would be illegal due to getting too close to the clouds.

Now, would it be illegal and/or be considered excessively hazardous to fly under the bridge assuming that the vertical clearance above the river is around 300 feet?

  • $\begingroup$ But one needs to be 500' above the Gnd unless landing. $\endgroup$ – CrossRoads Aug 30 '18 at 16:52
  • 1
    $\begingroup$ And also closely related $\endgroup$ – Dave Aug 30 '18 at 16:54
  • $\begingroup$ Not when one is not over populated areas, such as over extensive bodies of water $\endgroup$ – Ch654 Aug 30 '18 at 17:00
  • $\begingroup$ But typically there are boats on the water, those also need to be avoided by 500'. $\endgroup$ – CrossRoads Aug 30 '18 at 17:02
  • $\begingroup$ So you need to be 500' below the bridge, and 500' away from the water just to confirm you are 500' clear of things, so 300' is not legit. $\endgroup$ – CrossRoads Aug 30 '18 at 17:03

Sounds pretty hazardous (and almost definitely illegal) to me

Here's the first photo of the first suspension bridge I found when I looked on Wikipedia Niagara Falls Suspension Bridge

Guy Wires

Can you see all the really narrow guy wires below the bridge? No? I can't either. If you can't see them in a photo, how are you going to see them at 100 knots?

"But Steve, maybe there aren't any!"

Yes, or maybe there are. Are you confident enough to bet your life on it?

I thought you were the one with the plan!

Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight. (FAR 91.103)

Suspension bridges aren't like TFRs, they don't just appear in between the time you took off and the time you get to them. Why didn't you know there was a bridge there before you took off? Why didn't you have a plan for what to do when you got there already?

Boats are people too

You need to stay 500 feet from any structure. Bridges are structures, so you need to be 500 feet away from them. You also need to be 500 feet away from vessels and people, so if there's anyone on the river, your options just went from "bad" to "none".

But what about my emeeeergency?

All the rules go out the window if you're experiencing an emergency...as long as you're acting in the interests of the safety of the flight. I spent some time on a foggy morning talking with an FAA inspector about this very topic (flying under bridges in emergencies) a couple years ago, and his words were to the effect of:

"It would have to be a very unique emergency for flying under a bridge to be the safest course of action."

  • 4
    $\begingroup$ "Why didn't you know there was a bridge there before you took off?" This. $\endgroup$ – Zeiss Ikon Aug 30 '18 at 17:17
  • $\begingroup$ Excellent answer. Just one question, what guy wires are there underneath a suspension bridge? By definition, (and in accordance with the law of gravity) a suspension bridge is suspended by guy wires from above. $\endgroup$ – Michael Hall Aug 30 '18 at 17:24
  • $\begingroup$ P.S. The bridge pictured is a bizarre looking hybrid of a suspension bridge, and one supported from beneath by arches. In either case though, below ought to be clear if you really needed to go there... $\endgroup$ – Michael Hall Aug 30 '18 at 17:27
  • 1
    $\begingroup$ @MichaelHall - If I was a bridge-ineer instead of a plane-xecutive I would probably know facts like that. I'm not willing to bet my life on there being no wires down there, though. $\endgroup$ – Steve V. Aug 30 '18 at 17:27
  • $\begingroup$ @MichaelHall. It's an arc bridge, not a suspension bridge. The 'suspension part' of the hybrid you mention is only a temporary structure erected in order to facilitate the construction work of the central sections. $\endgroup$ – xxavier Aug 30 '18 at 17:47

Yes, it is illegal. Regardless of where you are, you are required to remain at least 500’ from any person, building, structure, or vessel.

Unless you are operating in Class G airspace, it’s also illegal, as you really don’t meet the weather requirements for VFR flight, either.

Don’t try it. People get killed doing scud running like that all the time.

  • $\begingroup$ I have never heard this called "acid running". I am very curious though. $\endgroup$ – Ryan Mortensen Aug 30 '18 at 23:45
  • 1
    $\begingroup$ I'm betting that whatever autocorrect @Carlo used didn't recognize "scud" and helpfully changed it to "acid" $\endgroup$ – Steve V. Aug 31 '18 at 1:07
  • $\begingroup$ @SteveV. - Yeah... I got a good chuckle out of this once I realized you're right. $\endgroup$ – Ryan Mortensen Sep 2 '18 at 2:17

Not the answer you're looking for? Browse other questions tagged or ask your own question.