How does the FAA determine a flight's altitude?

Question

Is it mostly weather & traffic related?

One other question:

What is the closest that 2 inflight planes can be to one another?

Thanks,

Primo

Thank you......I guess I didn't ask this correctly though. What I meant was....how does the FAA determine what a plane's altitude will be?

In other words.....when a plane takes off and control is switched over, how do they (FAA) determine how high up to put the aircraft on it's flight plan?

Answer 1

We, (the FAA air traffic controllers) will normally always try to get an aircraft up to it's requested altitude. Sometimes there are altitude restricted routes that preempt a higher requested altitude and a flight will not get up to it's requested.

A good example of this are flights operating from either ORD or MDW going to DAY(Dayton, Ohio) These flights musts fly a specific route of flight everday and are restricted to a maximum altitude of 23,000ft, known as Flight Level 230 (FL230). It is not uncommon for us to see a corporate aircraft want to go up to a much higher altitude, but it's not going to happen. These aircraft are held down at FL230 to keep them from becoming a hazard from ORD and MDW arrivals entering Chicago ARTCC airspace from SE.

Other aircraft of course play a role in determining the altitude an aircraft will climb to. Sometimes a small turn left or right will keep an aircraft's route of flight clear by 5 miles of lateral separation of a converging aircraft, so we can keep an aircraft climbing. But there are also instances where we have to let two aircraft cross each other, a minimum of 1,000' vertically separation.

5 miles lateral separation and 1,000' of vertical separation is the standard within the "center" en route environment, which a normal air carrier flight operates within usually for all of roughly 15 minutes of it's flight. There are many other rules of separation within the approach control/tower arena, (terminal), and that could actually be another question for Yahoo! Answers.

Barring an thunderstorm activity, (this will starting turning into a thesis if I elaborate on thunderstorms), the only weather I can think of off the top of my head that will preclude an aircraft climbing to it's RAL(requested altitude) is turbulence. Read on.

For example, an aircraft want to climb to FL330 and cruise there. But atc knows that at FL330 and above aircraft are experiencing continuous light and occasional moderate turbulence. If it's a longer flight, we'll advise the aircraft and let the pilot make the decision of what he wants to do with his altitude request. If we know his flight is not all that long, we will just tell the pilot that a lower altitude with a smooth ride will be his "final altitude" or cruising altitude to his destination.

WIthin the contiguous 48 states, the standard separation when talking to a "center", (this includes Class A airspace), is 1,000ft vertical and 5 miles lateral.

I think I've got it about covered here on the question. But without manuals in front of me, I'm shooting from the hip. Hope this was what you're looking for.

Answer 2

Under instrument flight rules each plane has a transponder which reports altitude as shown on the encoding altimeter in the cockpit. The transponder reports by responding to the ground based radar. In some parts of the country radar coverage is lacking and the pilot must report location and altitude periodically.

Under visual flight rules and away from major airports no reporting is required.

On an instrument approach FAA controllers keep 3 mile lateral separations or more. In VFR conditions and rules it is simply "see and avoid" other aircraft.

Your suplemental question: Under IFR the pilot files a flight plan with a series of "waypoints" and altitudes. These meet the rules of odd thousands Eastbound and even thousand Westbound. When he has completed his pretakeoff work air traffic control will issue a "clearance" which may be "as filed" but usually there are modifications and altitude may be one of them.

While the plane is in the air either air traffic control can order or the pilot can request an ammended clearance (route or altitude). Pilot requests are usually approved and vectoring around a storm would be an example.

Except around large airports where a clearance is required a pilot operating under VFR is responsible for choosing and maintaining altitude. In VFR the altitude rule is "odd thousand plus 500 ft Eastbound and even thousand plus 500 feet Westbound."

Answer 3

Normally the Pilot in Command will determine his or her operating altitude. Once he has chosen his altidude, Air Traffic Control will determine if it will work based on other traffic or airspace requirements. Weather does play a role, such as turbulence or icing and maybe even height of a thunderstorm. But, once again, it's up to the pilot to figure out his altitude. There are certian Federal Aviation Regulations that require a pilot to choose thier altitude based on restricted areas, millitary operating areas, and noise abatement areas,etc...

ATC has a very long list of spacing requirements. It is usually based on type of aircraft and speed. I guess technically two planes can fly adjacent to one another as long as both pilots are aware and have arranged the "formation flight". Under normal everyday commercial flying it's usually 500' vertical separation and around 2 miles or so.

Answer 4

Scheduled airline flights use what they call "canned flight
plans." They are the same every time. The FAA has these
in a database and are able to plan airspace positions in
advance. There are unscheduled instrument flights in the
system that delay the message they are waiting for: "cleared
as filed." So they have a plan for the aircraft and they have to
adjust each flight path for traffic and/or weather. Separation
distance changes with airspace but controllers like 3000 ft
vertical and 5 miles horizontal separation in class A and
1000' vertical in class B,C airspace.