We were on final approach into the Sanford (Florida) International Airport a few weeks ago. We were on a mid-size jet. My seat companion looked out the window and saw a small aircraft flying directly under us perpendicular to our direction.
Is that normal? I always thought that if you could see another aircraft in the air, you were too close.:eek:
Big airports like Sanford are generally a class B airspace, where the airspace is shaped like an upside-down wedding cake. Small aircraft often fly under one of the larger tiers (where the airspace is class E or G).
In general, aircraft are more closely spaced in altitude than horizontal distance. A vertical separation of 1000 feet is often acceptable, but horizontally it is more like several miles. Of course there are a zillion details which affect the exact numbers.
It is about following the rules and trusting the other pilot to follow the rules. How close is the car in the next lane when you are doing 65mph on the freeway?
If you fly close enough to read the N number without seeing the other aircraft coming that is way to close. If both pilots can see the other airplane and are in radio contact, it is no big deal.
I saw something even more surprising while landing in Lambert Field in St. Louis. There was another plane parallel to us, also landing. It couldn’t have been more than a few hundred feet away. Looking at Lambert in Google earth, it seems it has three parallel runways, two of them almost right next to each other and a third that is offset to the west past the ends of the other two.
It’s actually routine to have airplanes crossing above or below each other. Provided everyone is following the rules and air traffic control instructions it is quite safe. You’re just not used to actually seeing the other airplanes.
I recall the FAA several years ago was cracking down on airline pilots who were engaging in “races” on takeoff on parallel runways. IIRC, it was who could get off the ground first. I think it was O’ Hare.
When getting my license, my “long” cross-country flight was to Fresno. When taking off again from 29L (in my Cessna 172), there was a military jet–looked like an F-16–on 29R. Although I was a only few hundred yards ahead and we started at about the same time, when he passed me he was already climbing at what seemed like a 45 degree angle and four times my speed. A bit like a drag race between a Top Fuel dragster and a Ford Fiesta :).
It is entirely normal to see other aircraft in the air, especially in the vicinity of airports.
I’ve actually flown into Sanford in a very small plane (Cessna 152).
Sanford has parallel runways. In my case they slotted me in to a very long final (about 5 miles) for 27C and I was about 3rd to land when I joined final. This would have involved flying a base leg under the approach path for 27R, which could have given rise to the situation you experienced.
Oddly enough, while I was on final they changed my clearance to land on 27R, which is IIRC about 14000 feet long, and I had to taxi for miles (literally) after landing.
Interesting; I didn’t realize it was that close. Although I have a VFR ASEL license, it’s been several years since I used it, and I don’t recall ever learning the minimums between different combinations of flight rules. I just did what the controller said :).
Well rules vary between countries but are generally similar. In Australia east bound IFR traffic take odd thousands and west bound take even thousands as their standard cruising levels so you always have a 1000’ split between the IFR traffic, but the VFR traffic is slotted in between at odd thousands plus five hundred and even thousands plus five hundred respectively. Therefore you have a minimum of 500’ between any two aircraft in the cruise. Approach and departure is a more dynamic phase of flight so the rules that ATC work to may be more stringent, but you are only required to stay 500’ above the bottom of a control zone step and an uncontrolled aircraft is allowed to fly at the edge of the step, so once again only a minimum of 500’ is guaranteed between aircraft. When you factor in a possible combined altimeter error between two aircraft of 120’ and that sloppy pilots may be flying up to 100’ off their assigned altitude and it’s possible that two aircraft may only be a couple of hundred feet apart while operating quite legally.
Others above have covered the legalities & the numbers. On a more qualitative level …
When we’re in the arrival or departure phase of a flight and if the sky is anywhere near clear, we can almost always see one or more other airplanes. They’re all over the place if you have a big enough window & know where & how to look. On a nice day over a big city if I can’t see 10 I’m not trying.
As others have said, altitude is the primary separator, with 500 or 1000 feet being typical. For airplanes at the same altitude, spacing varies depending on what we’re doing. In cruise it’s several miles, usually more than 10.
Funny enough, in the old days (pre, say, 1998) in cruise nobody was exactly on-track; the nav systems weren’t that precise. And so a passenger could occasionally see a jet go by the opposite direction and 1/4 to 2 miles away and 1000-2000 feet (e.g. roughly 1/4-1/2 mile) higher or lower.
Nowadays with almost everybody on GPS, passengers don’t see those airplanes because they’re passing *directly *over or under us. In other words, with the same vertical offset as always, but *zero *lateral offset. We see folks coming right for our nose at 1000mph of closure all day long. Making darn sure they’re really at a different altitude than we are is an important task.
For situations like **Boyo Jim **described, the airplanes can be about 1/4 mile apart laterally with some fore/aft stagger. They start out 1000 ft vertically separated and can descend to be all-but co-altitude once both are established on track to the runway and both see each other.
Had the weather been poor that day instead of almost alongside each other they’d have been staggered with 3 or more miles fore/aft spacing between them. Which greatly reduces the total flow rate to the two runways. Hence the not-quite side-by-side operations on good weather days; it squeezes in more airplanes per hour.
It probably was an F-16; the California Air National Guard flies F-16s out of FAT. Query for people like LSLGuy? Is the wake turbulence from a F-16 anything to worry about for a C172 in Dr. Strangelove’s position?
Thanks for the confirmation. I didn’t get a really good look and I’m hardly a plane spotter but I was pretty sure it had a single engine and vertical stabilizer, so I figured an F-16 was the most probable.
I didn’t notice any out of the ordinary buffeting at the time (though the sound was pretty intense!). I know the wind can move a turbulent region to a different area… I don’t recall the wind speed/direction at the time, except that it was pretty light. I’d suppose the controller took all this into account when queuing us up.
Well, I call it Sanford to differentiate it from Orlando International. We’ve flown into MCO before and it’s a whole 'nuther ballgame. Sanford is so small that I was surprised to see multiple aircraft in the air at the same time.
It is actually a very busy airport because of flight training and it also gets a lot of charters because the landing fees are much lower than Orlando International.
If I could piggyback on Ruby’s question: LSLGuy, you mentioned more-advanced avionics reducing horizontal offsets. I was wondering about this just the other day. I live on (under, I suppose) one of the approach paths to Bradley International (BDL) in CT. I’m guessing that this path gets used on days that the wind favors landing on certain runways at BDL, since some days I see no traffic and some days there are planes going overhead all day long. On those days, I notice that not all the aircraft are actually flying the same path. Monday, for instance, I noticed and MD-80 that was literally directly overhead, but the 737 that preceded it and the A-320 that followed went by well to the west.
I know that approach plates are really detailed about turning at such-and-such point, fly at such-and-such speed, etc. I would think that any commercial jet would therefore fly the same approach relative to the ground. From my observations, though, this doesn’t appear to be the case.