# Flying a Jetliner into a Tunnel **URL:** \ **Category:** Factual Questions\ **Created:** [January 15, 2009, 8:00am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401 "2009-01-15T08:00:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Tuckerfan](https://avatars.discourse-cdn.com/v4/letter/t/eada6e/32.png) [@Tuckerfan](https://boards.straightdope.com/u/Tuckerfan)\ **Post date:** [January 15, 2009, 8:00am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/1 "2009-01-15T08:00:21Z")
I was listening to a news account of the troubles the British government was having with expanding Heathrow Airport, and I got to thinking that if such things continue, at some point (say 50 years from now), someone’s going to attempt to do a “Big Dig” and bury the airport and runways. One _big_ issue I can see with this, is that you’re **not** going to want a human at the controls, flying the jet into a tunnel (unless its _really_ oversize), it’ll have to be computer controlled. Another issue would be the noise in the tunnel/underground airport, you’ll need some serious noise abatement systems in the tunnel, or it’ll be loud enough _inside the plane_ to damage hearing. I’m sure that there’d be other issues as well, but I don’t know enough about aircraft to even WAG what they might be. Perhaps the change in air pressure caused by having the jet enter the tunnel would cause problems. (Need to have a way to circulate fresh air rapidly into the tunnels, at the very least.) So, what other technological hurdles would there be? ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [January 15, 2009, 8:45am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/2 "2009-01-15T08:45:15Z")
I think the runways are going to be, necessarily, open air. The taxiways are relatively small addenda. What’s the advantage for subterranean facilities? ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [January 15, 2009, 8:45am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/3 "2009-01-15T08:45:17Z")
> [@Tuckerfan](#): > > I’m sure that there’d be other issues as well, but I don’t know enough about aircraft to even WAG what they might be. Perhaps the change in air pressure caused by having the jet enter the tunnel would cause problems. (Need to have a way to circulate fresh air rapidly into the tunnels, at the very least.) > > So, what other technological hurdles would there be? The go around would be a bitch. If the bury anything it would be the support network for the airport such as underground parking garages, fuel depots, utilities etc… ---
**Author:** ![Robot\_Arm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robot_arm/32/18280_2.png) [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)\ **Post date:** [January 15, 2009, 9:36am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/4 "2009-01-15T09:36:43Z")
There’s a phenomenon called “ground effect” that operates within about one-and-a-half wingspans of the ground. It works as sort of a cushion beneath the wing, giving more lift than you’d have (at the same speed and angle-of-attack) outside of ground effect. So there are aerodynamic considerations when flying in places where the airflow is constrained in one way or another. In a sufficiently narrow tunnel, where the airflow is limited above, below, and to the sides, I suspect the effects would be even more pronounced. I just can’t see this ever happening. You may think that planes stay in narrow corridors defined by the runways, but they don’t. Not every plane uses the same amount of runway on takeoff. Pilots sometimes have to abort a landing and climb out. Climb angles are different depending on the type of plane and how heavily loaded it is. The only reason to build an underground airport is if something else is on the surface. In that case, put the airport on top and the something else underneath. What could need that airspace more than the airport? Actually, there is another reason for a subterranean airport; security. The germans built rockets and aircraft in hollowed-out tunnels during World War II. From what I can find online, I don’t see any sort of runway. I suspect the completed planes were taken away by rail. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [January 15, 2009, 9:51am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/5 "2009-01-15T09:51:15Z")
At least someone was crazy enough to do something similar, flying through a hangar in the opening of the Bond movie Octopussy. From an article in [Air & Space Magazine](http://www.airspacemag.com/history-of-flight/Live_and_Let_Fly.html?c=y&page=3): > [@](#): > > Fornof explains that he opened all the hangar’s doors and windows to reduce the sudden pressure increase caused by an aircraft trying to push a lot of air through an enclosed space. He calculated that, given the frontal area of the BD-5 and the size of the hangar, airspeed couldn’t exceed 180 mph. If he went too fast, “the pressure feedback would probably have caused me to bounce off the floor and into the rafters,” he says. I suspect an A380 will displace a _wee bit_ more air when plunging down a tunnel. Either it would have to be a truly gigantic tunnel or have the mother of all air extraction systems. Besides that, IIRC, the normal landing approach angle is 3 degrees, so you’ll need a fairly long trench for the plane to go down into as it descends into the tunnel opening or you’ll have to build the tunnel on the face of a mountain or hill. Please note that pilots are not keen on flying into mountains. 😛 By my calculations, if you go with the trench idea, and assuming a tunnel height of 50 meters, in flat ground you’ll need a trench 1Km long to descend into the tunnel opening. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [January 15, 2009, 10:49am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/6 "2009-01-15T10:49:06Z")
Did you ever watch Battlestar Galactica? Accidents in tunnels tend to be bad bad things. What could have been a rough crash landing would turn into a monumental fireball. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [January 15, 2009, 11:31am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/7 "2009-01-15T11:31:39Z")
> [@Sapo](#): > > Did you ever watch Battlestar Galactica? Accidents in tunnels tend to be bad bad things. What could have been a rough crash landing would turn into a monumental fireball. Yes, but it would be so levely _contained_! a fiery inferno of destruction and death underground, while oblivious birds chirp in the prairie above. I just remembered something related, the IJN carrier Akagi actually had two stacked decks, one on top of the other. Planes could take off from both the lower and upper decks. But not even the Japanese where suicidal enough to attempt landing on the lower, tunnel like, deck! ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [January 15, 2009, 11:39am UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/8 "2009-01-15T11:39:46Z")
Well, what do you know?. I went out to refresh my memory on the Akagi and it turns out that it didn’t have two decks for take off… it had three. :eek: [Here you can see the arrangement on a plastic model of the ship](http://solomaquetas.com/forum/index.php?showtopic=7123) ---
**Author:** ![glee](https://avatars.discourse-cdn.com/v4/letter/g/b5a626/32.png) [@glee](https://boards.straightdope.com/u/glee)\ **Post date:** [January 15, 2009, 12:25pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/9 "2009-01-15T12:25:04Z")
> [@Tuckerfan](#): > > I was listening to a news account of the troubles the British government was having with expanding Heathrow Airport, and I got to thinking that if such things continue, at some point (say 50 years from now), someone’s going to attempt to do a “Big Dig” and bury the airport and runways. It’s not the English style to do this. Instead protesters have: - formed pressure groups - challenged the expansion at planning enquiries - lobbied their Members of Parliament - protested outside the airport (admittedly [Plane Stupid](http://www.planestupid.com/) did [get onto Stansted Airport](http://www.planestupid.com/?q=content/plane-stupid-invade-stansted-airport), but there’s still no violence) - [bought up land needed for expansion](http://www.greenpeace.org.uk/) ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [January 15, 2009, 1:31pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/10 "2009-01-15T13:31:44Z")
[North Korea](http://googlesightseeing.com/2008/05/19/north-koreas-thunderbird-runways/) has apparently built a few runways that go through/under mountains. It’s not clear, though, whether they actually intend to use these for landing planes, or just as a convenient place to hide them until they take off. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [January 15, 2009, 2:15pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/11 "2009-01-15T14:15:57Z")
Well I know you can fly a helicopter in the railroad tunnel! I saw it in the movies! :dubious: ---
**Author:** ![flyboy](https://avatars.discourse-cdn.com/v4/letter/f/4da419/32.png) [@flyboy](https://boards.straightdope.com/u/flyboy)\ **Post date:** [January 15, 2009, 2:27pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/12 "2009-01-15T14:27:07Z")
This is pretty silly speculation. There is no way this’ll ever happen. Aside from everything already mentioned, you simply cannot shoot an approach down to the minimums, break out at the last second, make corrections, and zoom right on into a tunnel opening. Firstly, there’s no way to make corrections due to crosswinds and centerline adjustments. Secondly, you’d have to raise the landing mins (the height of the cloud deck above the ground) to give aircraft more time to make a precise path to the opening. Aircraft need a nice long, wide, open-field runway to make these corrections. Ever been on an airplane that’s floated for a bit down the runway before setting down? How’s that going to work with a tunnel opening? This isn’t even taking into account the empty aircraft and soon-to-be bankrupt airlines operating out of that airport. I mean, I wouldn’t fly on that plane. Would you? ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [January 15, 2009, 2:42pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/13 "2009-01-15T14:42:20Z")
> [@MonkeyMensch](#): > > I think the runways are going to be, necessarily, open air. The taxiways are relatively small addenda. What’s the advantage for subterranean facilities? It would be massively cool. If VTOL or STOL planes ever catch on as well as their researchers would like them to, there may be a place for them in an underground, or mostly underground, facility, but I would wager that, like on an aircraft carrier, would be mostly for storage and maintenance. ---
**Author:** ![Dead\_Cat](https://avatars.discourse-cdn.com/v4/letter/d/9fc29f/32.png) [@Dead\_Cat](https://boards.straightdope.com/u/Dead_Cat)\ **Post date:** [January 15, 2009, 2:50pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/14 "2009-01-15T14:50:19Z")
I’m surprised that nobody has yet mentioned (or perhaps they have, I only skimmed the thread) that the main reason people protest about expanding airports is not the noise from the airport itself, but the noise from the additional flightpaths and the extra planes that would use these in the event of expansion. Putting the airport itself underground does nothing to solve these problems. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [January 15, 2009, 3:49pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/15 "2009-01-15T15:49:39Z")
> [@Dead\_Cat](#): > > I’m surprised that nobody has yet mentioned (or perhaps they have, I only skimmed the thread) that the main reason people protest about expanding airports is not the noise from the airport itself, but the noise from the additional flightpaths and the extra planes that would use these in the event of expansion. Putting the airport itself underground does nothing to solve these problems. You are just too shortsighted in your approach. If you built extensive networks of underground flight paths, that would solve the problem. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [January 15, 2009, 3:51pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/16 "2009-01-15T15:51:46Z")
> [@Ale](#): > > Besides that, IIRC, the normal landing approach angle is 3 degrees, so you’ll need a fairly long trench for the plane to go down into as it descends into the tunnel opening or you’ll have to build the tunnel on the face of a mountain or hill. Please note that pilots are not keen on flying into mountains. 😛 > By my calculations, if you go with the trench idea, and assuming a tunnel height of 50 meters, in flat ground you’ll need a trench 1Km long to descend into the tunnel opening. Airplanes, including airliners, are capable of approaches significantly steeper than 3 degrees - it’s just that such steep descents are likely to scare the hell out of a certain percentage of passengers. Some airports require angles steeper than 3 degrees, and cargo pilots fly steep approaches more often than passenger airliners because boxes don’t complain. A trench/ramp is necessary, but not as long a one as you assumed. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [January 15, 2009, 4:02pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/17 "2009-01-15T16:02:46Z")
I consider it more likely that they’ll start burying other things under the airport, rather than burying the airport under things. Why don’t they just expand Gatwick? It’s half the size of Heathrow, right? ---
**Author:** ![A\_Dodgy\_Dude](https://avatars.discourse-cdn.com/v4/letter/a/a87d85/32.png) [@A\_Dodgy\_Dude](https://boards.straightdope.com/u/A_Dodgy_Dude)\ **Post date:** [January 15, 2009, 5:01pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/18 "2009-01-15T17:01:45Z")
I saw the title of the thread and the first thing I thought was, “This is going to be the coolest video ever!” :smack: ---
**Author:** ![Figaro](https://avatars.discourse-cdn.com/v4/letter/f/ea666f/32.png) [@Figaro](https://boards.straightdope.com/u/Figaro)\ **Post date:** [January 15, 2009, 6:05pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/19 "2009-01-15T18:05:14Z")
Flying an airplane near any object or building, let alone eveloping it in a tunnel, is unsafe. Aside from the logistical and aerodynamic problems already mentioned (say…what happens when the tunnel lights fail when you’re airborn at 100 knots…?), flying in a tunnel would be like driving a car at full speed across a mile-long suspension bridge consisting of nothing but two planks for the tires. Certain death. ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [January 15, 2009, 7:46pm UTC](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401/20 "2009-01-15T19:46:14Z")
> [@Figaro](#): > > flying in a tunnel would be like driving a car at full speed across a mile-long suspension bridge consisting of nothing but two planks for the tires. Certain death. But that’s something a computer specifically designed to do that would be able to do repeatedly. Flying is a much more difficult task but it might be possible to build special planes capable of doing this with special tunnels. I don’t have a cite but I was under the impression that a lot of the modern military aircraft are not even all that stable without constant micro adjustments by their flight systems. The problem I foresee is that even if such technology were to materialize it’s still fairly stupid to make a passenger jet that can’t be landed by a human being. [Next page](https://boards.straightdope.com/t/flying-a-jetliner-into-a-tunnel/481401.md?page=2)