Lv 4
null asked in Cars & TransportationAircraft · 1 decade ago

How do pilot's navigate?

How do major airlines navigate through the sky via IFR? What about VFR?

Does ATC tell them when to turn, what altitudes to fly at...

Or does the aircraft's Flight Managment System manage that stuff?

When Do You Contact ATC?

Stay In contact throughout whole flight

Only contact towers when you want to land.

How strictly are you controlled by ATC?

Do they tell you your altitude to fly at in private aircraft?

When must flightplans be made?

4 Answers

  • 1 decade ago
    Favorite Answer

    Good answers so far. I just want to add a couple things.

    Remember IFR and VFR don't technically have anything to do with weather or visibility but rather indicate what rules you're flying under. When visibility and cloud clearance allow, private pilots fly under Visual Flight Rules, but may opt for Instrument Flight Rules if the pilot is qualified.

    Commercial flights fly under Instrument Flight Rules all the time, regardless of the weather. This means they are always flying under direction of ATC even if they're not directly in communication with ATC at any given time.

    When flying under IFR, the pilot files a flight plan that includes a proposed route. ATC can alter that route and communicates it to the pilot in the form of a "clearance". A clearance includes a destination, routing information, altitude, frequency to use to communicate with ATC, and a unique transponder code to use so that you can be identified by ATC. Along the route, ATC can amend the clearance. They can also issue temporary turns or climbs/descents depending on traffic, weather, equipment malfunctions on the ground, or other factors.

    The pilot enters the clearance into the FMS and it works together with the autopilot to fly the route. Of course the pilot can also just fly the route him or herself, but that is unusual. For private pilots, the route can be entered into a GPS unit, which then communicates with the autopilot to fly the route. Again, the pilot can and often does fly the airplane him or herself, following the route given in the clearance.

    Commercial flights are at altitudes that require minimum changes along the way. Private pilots are sometimes flying at altitudes that are low enough that they need to climb along the way to maintain radar and communications contact with ATC. These are described on navigation charts and can be assigned by ATC.

    Contact with ATC begins when the aircraft is ready to taxi. They contact ground control for taxi, then tower for take-off, then departure after they are in the air. Normally the pilot switches to the tower frequency when at the end of the runway and ready to depart. After that, hand-offs are handled by ATC. That is, ATC will instruct the pilot to contact departure, then departure will tell the pilot to contact center or the next enroute controller. In each case the pilot will also be given the frequency, except for the handoff to departure. In that case the pilot already has the frequency, which was given to him or her as part of his original clearance.

    Contact with ATC continues throughout the flight. Communication is handed off to the next controller along the way. Commercial flights fly at high altitudes and have fewer handoffs. Private flights tend to fly lower and tend to have more handoffs. Each handoff consists of the name of the station to contact and the frequency to use (i.e. "Contact XYZ Center 132.8"). As the flight approaches its destination, it is handed off to approach for the destination airport, then to the tower, then -- after landing -- to ground.

    When flying below 18,000' each contact with a new controller will also include the barometric pressure being used for that sector. This assures that all aircraft in the sector are using the same altimeter settings.

    Pilots are required to always obey ATC instructions unless doing so would endanger the flight. Controllers are flexible, though, and try to accommodate requests. So you can request a different altitude, different routing, etc.

    Private pilots flying VFR choose their own altitudes. When flying generally west, VFR flights are at even 1000's plus 500' (i.e. 4500, 6500, 8500, etc.) When flying generally east, they are at odd 1000's plus 500' (5500, 7500, 9500, etc.) IFR flights are at 1000' intervals (i.e. 4000, 6000, 8000, etc. for westbound; 5000, 7000, 9000, etc for eastbound.)

    Flightplans can be filed at any time. They take about 30 minutes to make their way through the system, so we try to file at least 30 minutes prior to departure. Flightplans are not required for VFR flights. They can be filed with Flight Service as a safety measure but in general they are not used for most VFR flights.

    Hope this helps.

  • 1 decade ago

    Airliners use multiple navigation methods for redundancy, including dead reckoning with inertial reference systems, radio navigation via VOR stations, and radio navigation via GPS satellites. They have several of each type of navigation device to provide back-up in case of failures. For landing, they use mostly ILS for precision approaches, and GPS or VOR for non-precision approaches.

    There is no VFR for commercial airliners. They always fly IFR, no matter what the weather is like.

    The FMS contains computers that direct the autopilot, which in turn flies the airplane for most of a flight. The FMS knows the complete route of the flight, both laterally and vertically, and will manage the entirety of the departure, en-route, and arrival phases of the flight. Take-offs are usually flown by hand; so are landings, except in poor weather, in which case the on-board computers may be instructed to autoland the airplane automatically.

    Airliners are in contact with ATC all the time, from gate to gate.

    Airline pilots are required to follow ATC instructions at all times, unless they cannot for safety reasons.

    In a private aircraft, if you are flying VFR, altitude is at your discretion as long as you follow a few guidelines. If you are flying IFR, you are assigned altitudes by ATC, based in part on your filed flight plan. If you are VFR in certain types of controlled airspace around major airports, ATC may also give you headings and altitudes to follow while you are in that airspace.

    Flight plans are required for IFR flights. They are optional for VFR flights except in certain airspaces (such as around Washington, D.C.).

    Some of these rules vary from one country to another. The above is for the U.S.

  • ztim
    Lv 5
    1 decade ago

    Many good questions here. An airline pilot lets the auto pilot do most of the work. Routs are already planned and unless he has to re-rout due to bad weather, he/she can just the plane do its thing. A private pilot can file his or her own flight plan according to needs. Altitude can vary but I do recall direction can dictate at least the altitude one flies at +/- 500'.

    Flight plans should be filed as close to the fight as possible. That way the ground control and tower can be sure all the latest weather etc. is up to date. The weather forecasts at some airports have a code you mention when asking for clearance.

  • By sixth sense :)

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