Okay, Wednesday afternoon pilot poll time.
Flying around the bay the other day, with helicopters taking tourists over the Golden Gate Bridge and a couple of fixed wings circling Alcatraz, I took a look at the geometry of the bridge and asked myself what the minimum crossing height should be, mid-span, as per the FARs.
I did a little reading (So you don't have to) and here is what I found: The clearance of the deck is 220 feet. The thickness of the deck (This was harder to figure out - Not many references) is about 25 feet, so let's call the deck height 245 feet. The towers are 746 feet MSL and 4200 feet apart. Let's assume a mid span crossing. Oh, and in a discussion with the Oakland FSDO, he does consider the bridge a 'congested area' as per FAR 91.119(b). There's also a class Bravo shelf overhead at 3000', for those of you who'd rather stay right away from all the traffic in that area. ;)
Some other clues: 1245 feet isn't going to cut it. Anything over 1746 feet would keep you in the clear no matter where you flew. And mid-span, an aircraft is going to be more 2000' horizontally from the towers. But what I was thinking about were those suspension cables that come down...
Would every pilot here take the unambiguous option and say 1750+ feet MSL? Or would it be perfectly reasonable (mid-span) to go at 1500 feet? Or do I need my set square? ;D
(BTW, this is simply a philosophical question based on obstacle clearance, not one of those 'is it legal to fly 5 feet over open water' type questions. Clearly, the FAR's rule and there's always good old 91.13 if you upset Gavin Newsom...)
Why not fly under the span? You'd be more than 2000' horizontally from any obstruction, I don't think you could call the water a congested area, and I don't believe there is any minimum height below an object... ;D
Hehe. Okay, okay. Something tells me you're definitely talking 91.13 territory there...
I couldn't quote you the exact rule, but an instructor told me here that flying under the bridge was perfectly legal for a sea plane so long as it was taking off or landing.
Quote from: Al Sayre on August 18, 2010, 08:53:38 PM
Why not fly under the span? You'd be more than 2000' horizontally from any obstruction, I don't think you could call the water a congested area, and I don't believe there is any minimum height below an object... ;D
The Blue Angels did it one year at fleet week (I witnessed it). They got in trouble. Grounded. Not invited back the next year. They can fly 36" from a moving F18 but not hundreds of feet from a stationary bridge. Rules are rules.
Quote from: simon on August 18, 2010, 08:59:01 PM
Hehe. Okay, okay. Something tells me you're definitely talking 91.13 territory there...
I couldn't quote you the exact rule, but an instructor told me here that flying under the bridge was perfectly legal for a sea plane so long as it was taking off or landing.
I did it. I was doing touch and goes on a river and flew under a very low overpass.
QuoteThe Blue Angels did it one year at fleet week (I witnessed it). They got in trouble. Grounded. Not invited back the next year.
Interesting. How unlucky can you be to have Gavin driving across the bridge right at that particular moment. ;D
It's okay though. I've sort of figured it out (You can tell I'm busy on this particular afternoon...). For all intensive purposes it practically is 1750' MSL. Since the towers are 4400' apart, it is *reasonable* that a pilot could fly mid span within 200 feet of the low point (You can see where the suspension cables are at their lowest) and therefore be more than 2000 feet from the towers. However, the suspension cables run down from the towers to the mid point. If the pilot was able to fly *precisely* over the mid point, then they would need to be 1000 feet higher than where the suspension cable was 2000 feet away. My calculations put that point 95 feet below than the top of the tower, i.e. about 650' MSL. So the minimum crossing altitude is at least 1650' MSL and that's with Chuck Yaeger precision. Basically, it's going to be 1750' for us mortals to be completely in the clear.
Dunno why I end up answering my own questions, but at least the Blue Angel story was interesting.
Quote from: simon on August 18, 2010, 09:47:53 PMFor all intensive intents and purposes it practically is 1750' MSL.
;)
Quote from: Thrash on August 18, 2010, 09:08:14 PM
Quote from: Al Sayre on August 18, 2010, 08:53:38 PM
Why not fly under the span? You'd be more than 2000' horizontally from any obstruction, I don't think you could call the water a congested area, and I don't believe there is any minimum height below an object... ;D
The Blue Angels did it one year at fleet week (I witnessed it). They got in trouble. Grounded. Not invited back the next year. They can fly 36" from a moving F18 but not hundreds of feet from a stationary bridge. Rules are rules.
So far as I can tell that is simply a long standing urban legend. Since 1981, the only years they've not been at Fleet Week was 2001 (all Fleet Week was cancelled due to 9/11) and 2004 and that was by their own choosing. Any appearance that they went under the bridge is simply an optical illusion, just like the photos of them buzzing fishing boats.
But a good urban legend nonetheless. ;)
The greatest chance that the Blue Angels stand of being canceled in San Francisco is if the loonies at CodePink, Global Exchange and Veterans for Peace get their way. They've been trying to stop them for a while now in support of their causes.
I've seen them down there and it is spectacular flying. The precision of those pilots really is amazing.
Sean Tucker goes nuts as well. I don't know how physically he can do his routine for so long. Plus he must be landing on fumes. Those Pitts don't have a whole lot of endurance.
Quote...I don't believe there is any minimum height below an object...
Yes there is. 91.113(c):
"...the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure."You need to find a bridge 500 feet above the water plus whatever height you are above the water. But in any case, they are going to slap a 91.13 on you.
But while we're on the subject of buzzing, my personal favorite:
http://www.youtube.com/watch?v=_txdqnVP3-c
with a great comment "In the 70's this was cool, now days it's terrorism..."
Love the glasses and no headset.
... I was doing a 'Bay Tour' and got a bunch of images:
(http://17500mph.com/z/main.php?g2_view=core.DownloadItem&g2_itemId=1088&g2_serialNumber=2)
http://17500mph.com/photos-3?g2_itemId=664&g2_page=12
Quote from: simon on August 19, 2010, 12:35:35 AM
But while we're on the subject of buzzing, my personal favorite:
http://www.youtube.com/watch?v=_txdqnVP3-c
with a great comment "In the 70's this was cool, now days it's terrorism..."
Love the glasses and no headset.
On the same topic...and with the bridge:
http://www.youtube.com/watch?v=3Iw0MgyOcRo
Unlike fixed wing aircraft, helicopters under bridges are acceptable.
embarassed to ask, but how do I post a photo...
I had a guy come yell at me once at the DZ because he didn't like the way the visiting Casa 212 was taking off over his house. (I politely directed him to the person in charge, but he preferred yelling at the guy guy who had nothing to do with flight ops..)
After he spent 5 minutes shouting about how he knew it was "illegal for that plane to fly that low" and that he was going to "call the FAA on you idiots," I interrupted him, asked him if he was a pilot, and whether or not he knew FAR 91.119. He said he did not, and I told him that the FAA would like tell him to pound sand, since according to the federal regs, while taking off and landing the plane is allowed to fly that low.
He continued to rant at me until I told him we were going to call the local cops and have him removed.
BTW, if you're feeling sporty about "under bridge flying," google "French King Bridge" (its on the Connecticut River in Western Mass). Around 20 years ago, now, a guy flying skydivers in a Dornier 228 decided to give everybody a thrill ride and fly under the bridge. The guy who is the DO in my CAP squadron here was the Chief Pilot of the regional outfit that owned those planes, and the chowderhead in question was one of his guys. Suffice to say, he was not thrilled that following Monday when the local FSDO ops inspector called his office and said "Hi, we need to talk about one of your pilots..."
:)
(IIRC, the bridge is only 145 ft off the water..)
My rough calculations using an assumption that the cables follow a normal parabola (y=Ax^2), tells me that in the 100 feet from each tower, the cables drop 47', giving an height of 699' for the cables with 2000' clearance either way, so, with 1.000' above would be 1,699' altitude.
This is lower than if you assume the cables drop linearly (y=mx), in which case the cable would only drop 23' over the same 100' of horizontal distance.
NIN, was the Dornier pilot's certificate suspended?
I expect any under bridge flying would result in a suspension.
What he did was pretty risky. I mean compare this in terms of how it would look to a bystander: (a) Seeing someone flying a four seat piston plane out from San Francisco Bay towards the Pacific ocean, under a bridge with pylons 4400 feet apart with nothing else around but water, and (b) Flying a complex type rated 19 seat twin turbo prop with a bunch of people on board along a river less than 1000' wide with rising terrain on both sides then under a parabolic bridge with pylons less than 500 feet apart. An observer on the French King Bridge would have wigged out watching this big noisy aircraft blast by. On the Golden Gate, it may well go unnoticed and probably does given that choppers do it occasionally. I'll bet the FSDO guy really went to town when he found out there were passengers on board.
All illegal of course.
But if you want to see a really great video of a seaplane blasting around San Francisco Bay, checkout the Red Bull Albatross here:
http://www.youtube.com/watch?v=hSJ5ACt7zXo
A big twin radial seaplane. How good would that feel! That bridge must have looked really tempting...and legal, right?
Quote from: simon on August 19, 2010, 07:05:09 PM
NIN, was the Dornier pilot's certificate suspended?
I expect any under bridge flying would result in a suspension.
Oh, you betcha. Funny thing was, according to the story, the guy behind the controls was the "junior man" of the
required 2-man cockpit crew. The "captain" was in the back with a rig on, prepared to jump.
Its my understanding they both got violated.
QuoteWhat he did was pretty risky. I mean compare this in terms of how it would look to a bystander: (a) Seeing someone flying a four seat piston plane out from San Francisco Bay towards the Pacific ocean, under a bridge with pylons 4400 feet apart with nothing else around but water, and (b) Flying a complex type rated 19 seat twin turbo prop with a bunch of people on board along a river less than 1000' wide with rising terrain on both sides then under a parabolic bridge with pylons less than 500 feet apart. An observer on the French King Bridge would have wigged out watching this big noisy aircraft blast by. On the Golden Gate, it may well go unnoticed and probably does given that choppers do it occasionally. I'll bet the FSDO guy really went to town when he found out there were passengers on board
All illegal of course.
Yeah, big time.
I think they were putting 20+ jumpers in the Dornier, too.
I know a gent who was on that aircraft, too. There's video someplace.
(My former DO, being the chief pilot for this outfit, basically said "Throw the book at 'em." They had to send "management pilots" for the remainder of the time they flew for that DZ.)
A part of me says that I wouldn't have minded flying in the 50's where aviation was all fun and games, there was less regulation, less monitoring, a few winks of the eye and a lot more forgiveness (Read 'turning a blind eye').
Yet another part of me says the accident rate back then was also considerably higher...
i saw a few f18s do it in "the rock"
:lol:
Quote from: coudano on August 20, 2010, 01:51:01 PM
i saw a few f18s do it in "the rock"
:lol:
[hijack]
Yeah, well under National Command Authority, they were supposed to fly under radar to Alcatraz Island....This was their safest approach.
[\hijack]
Quote from: simon on August 20, 2010, 02:51:37 AM
A part of me says that I wouldn't have minded flying in the 50's where aviation was all fun and games, there was less regulation, less monitoring, a few winks of the eye and a lot more forgiveness (Read 'turning a blind eye').
Yet another part of me says the accident rate back then was also considerably higher...
You used to be able to do a lot of things in the past, that you can't do now.
Like fly below the rim of the Grand Canyon.
Do it now and you're an ex-pilot.
Quote from: CadetProgramGuy on August 21, 2010, 03:39:12 AM
[hijack]
Yeah, well under National Command Authority, they were supposed to fly under radar to Alcatraz Island....This was their safest approach.
[\hijack]
No hijack.. it involves the Golden Gate Bridge. :)
And launching green flares.
Everybody likes green flares.
Quote from: simon on August 18, 2010, 08:32:51 PM
Oh, and in a discussion with the Oakland FSDO, he does consider the bridge a 'congested area' as per FAR 91.119(b).
Found this online: "Thinking about buzzing the freeway? The FAA has held that moderate traffic constitutes a congested area – even if it is far from any house or structure!" (Source) (http://www.airportjournals.com/Display.cfm?varID=0811004)
This would seem to support a minimum altitude of 1240 over the
length of the span, with the 500 foot rule applying to other parts of the structure itself.
Mustang, it's actually going to have to be 1000' above the top of the towers, so roughly 1750' MSL, because you need to remain 1000' above any structure 2000' laterally.
I'm not going to get picky on +/- 100 feet, but a rep. from the Oakland FSDO went through it with me and his view was 1000' above the top of the towers. The deck height of 250' doesn't really come into it because even though the towers are more than 2000' away from the center point between the towers, the cables running up to the tops of the towers are part of the structure.
The whole point of me calling the FSDO in the first place was to get their interpretation of the rules, which, when you think about it, was probably the gist of what the lawmakers intended. If you stay 1000' above the highest point, you're safe. Anything else...well, history tells me the FAA usually wins.
Quote from: simon on August 24, 2010, 05:37:40 AM
Mustang, it's actually going to have to be 1000' above the top of the towers, so roughly 1750' MSL, because you need to remain 1000' above any structure 2000' laterally.
I'm not going to get picky on +/- 100 feet, but a rep. from the Oakland FSDO went through it with me and his view was 1000' above the top of the towers. The deck height of 250' doesn't really come into it because even though the towers are more than 2000' away from the center point between the towers, the cables running up to the tops of the towers are part of the structure.
The whole point of me calling the FSDO in the first place was to get their interpretation of the rules, which, when you think about it, was probably the gist of what the lawmakers intended. If you stay 1000' above the highest point, you're safe. Anything else...well, history tells me the FAA usually wins.
Like I said earlier, you have about 47' of play room in terms of the height of the cables (about what they drop in the 100' of horizontal you have >2,000), but pretty close to towers+1,000...