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It's so that in the event of mechanical failure a pilot can always rely on a magnetic compass for navigation, without having to know or look up the magnetic var
by SOTGO 4y ago
It's so that in the event of mechanical failure a pilot can always rely on a magnetic compass for navigation, without having to know or look up the magnetic variation of the airport.
- TylerE 4y agoAnd also so when they get cleared for “runway 15” they know which side to come on without having to consult a chart. Also so there’s no confusion, each direction is named, so a runway that runs due North-South will be Runway 36 in the northern direction, and 18 to the south. In practice it is rare for all but the largest airports to have more than 3 or 4 runways so it isn’t like there will be a Runway 2 and a Runway 3 at the same airport. If they need more capacity they’ll build parallel runways which will be named with a suffix, like 9L and 9R. (Also, magnetic compasses aren’t that accurate in the first place, since there’s iron in the engines if nothing else. In theory there should be a compensation/calibration done with the results on a card, but, no guarantees that it’s done or up to date).
- pdonis 4y ago> If they need more capacity they’ll build parallel runways which will be named with a suffix, like 9L and 9R. There are even some airports that have three runways with the same heading, so they have "L", "C", and "R". (Two examples that I've personally took off or landed on all three of are 17/35 at DFW and 01/19 at IAD.)
- sokoloff 4y agoOr 4 parallel runways like Detroit Metro (KDTW): 4R, 4L, 3R, and 3L. https://aeronav.faa.gov/d-tpp/2213/00119AD.PDF https://aeronav.faa.gov/d-tpp/2213/00119AD.PDF
- asciimike 4y agoKDEN also has four parallels (16-34L/R and 17-35L/R). All are 172.6º or 352.6º.
- stevehawk 4y agoKDEN also put their runways so close together that it's not uncommon to for aircraft on approach on the parallel to set off another airplane's TCAS. I think most airline pilots consider that airport ripe for a midair.
- Mountain_Skies 4y agoAtlanta has five parallel runways: 27R, 27L, 9R, 9L, and 28/10. It appears the main four that are close to each other are set alternating east landing and west landing as they're not marked on both ends like 28/10 is.
- sokoloff 4y agoThey are numbered on both ends on both the satellite view (real-world) and on the FAA diagram: http://aeronav.faa.gov/d-tpp/2213/00026AD.PDF http://aeronav.faa.gov/d-tpp/2213/00026AD.PDF There would be no (or extremely rare, at a minimum) operational reason to alternate directions for takeoff and landings on parallel runways. (There are rules for simultaneous operations to parallel runways and having them be in opposite directions would be problematic as you have to assume some aircraft will execute a missed approach and would then be climbing into opposite direction landing traffic with only a small lateral offset.)
- TylerE 4y agoAbout the closest I can think of to that is some mountain airports that do all takeoffs one way and all landings the other. I’m not aware of any of those with more than one runway and traffic is usually extremely limited.
- addaon 4y ago27L and 9R are the same runway, always. 27R and 9L are the same runway. In Atlanta, besides 27L/9R and 27R/9L, there's also 26L/8R and 26R/8L, as well as the 28/10 you mention. See https://aeronav.faa.gov/d-tpp/2213/00026AD.PDF https://aeronav.faa.gov/d-tpp/2213/00026AD.PDF
- pdonis 4y agoThis is the same dodge that ORD uses, as DocTomoe pointed out: pretending some of the runways are a different heading when they're actually not. I'm not sure how that can be avoided with four runways, though, since I don't see how to fit a fourth option in with "L", "C", and "R". In fact, taking this dodge into account, the DFW example I gave actually has five parallel runways; the two they label 18/36 are actually the same heading as the three they label 17/35. I wonder if they'll ever need to go to six and add an 18/36C.
- pishpash 4y agoWhat's L C R and why can't there be more letters?
- TylerE 4y agoCould just go A B C D E left to right I guess. If only 3 use B C D so the middle is always C regardless of system.
- sokoloff 4y agoYou want to have a consistent designation for opposite direction runways. (9R is always the same piece of pavement as 27L) Doing that for 4 would need one direction to be A B C D and the other to be B C D E (which is workable, but doesn't seem particularly more elegant than just using left, right, and center [and in fact is worse in some ways, since from one direction, B is the left-most and from the other, it's A])
- DocTomoe 4y agoAlso, EDDF/FRA, in which one runway got renamed to C when they opened a smaller one in the 2010s. Then you have airports like ORD which have more than three parallel runways - but pretend some of them are ten degrees off to get more naming space. [1] [1] https://upload.wikimedia.org/wikipedia/commons/a/aa/FAA_O%27Hare_Diagram.svg https://upload.wikimedia.org/wikipedia/commons/a/aa/FAA_O%27...
- s1dev 4y agoThe correction card is legally required equipment and there are a few maintenance items that trigger a requirement to update it
- OliverJones 4y agoWith respect, calibrating compass compensations is in fact very important in FAA approved aircraft. It's part of the inspection checklist signed off by the licensed mechanic. My flight instructor once switched off the electricity to the airplane's controls and radios and told me to land. At an airport with a control tower. Using the magnetic compass, airspeed, barometric altimeter, RPMs, that's it. Nothing else works without electric power. There's a whole procedure for doing all that. Being able to navigate safely with an old-school magnetic compass is life-critical.
- TylerE 4y agoOk, that’s totally fair. It’s been 25 years since I took a few lessons, purely dim since then.
- zzless 4y agoNot to doubt your story but being a flight instructor myself, I cannot imagine intentionally turning off power to airplane radios at an airport with a control tower (this is also illegal). As far as the pure mechanics of landing go, one does not need any instruments whatsoever: one can judge the airspeed by the sound and the wing angle. I routinely make my students do this when I teach tailwheel flying.
- TheRealPomax 4y agoNot to mention that no one would ever be insane enough to turn off electronics and then say "right, now IFR your way in". You're flying VFR, you're going to have eyes on the runway.
- stevehawk 4y ago> Not to doubt your story but being a flight instructor myself, I cannot imagine intentionally turning off power to airplane radios at an airport with a control tower (this is also illegal). You just pre-arrange it with the tower and it's no big deal. Probably exceptions for busy class Cs or Ds, but it's no big deal to any airport near me.
- grepfru_it 4y ago
- V99 4y agoThere are only 3 suffixes, so if there are 4 or more parallel runways one will get the "wrong" number, like 2/3L/3C/3R.