Normal procedures enroute will vary according to your proposed route, the traffic environment, and the ATC facilities controlling your flight. Some IFR flights are under radar surveillance and control from departure to arrival; others rely entirely on pilot navigation. Flight proceeding from controlled to uncontrolled airspace are outside ATC jurisdiction as soon as the aircraft is outside of controlled airspace.
Where ATC has no jurisdiction, it does not issue an IFR clearance. It has no control over the flight; nor does the pilot have any assurance of separation from other traffic.
With the increasing use of the national airspace, the amount of uncontrolled airspace is diminishing, and the average pilot will normally file IFR via airways and under ATC control. For IFR flying in uncontrolled airspace, there are few regulations and procedures to comply with. The advantages are also few, and the hazards can be many. For rules governing altitudes and course to be flown in uncontrolled airspace, see FAR 91.
Enroute Separation. For enroute control, departure control will advise you to contact Air Route Traffic Control (the appropriate Center) on a specified frequency as you approach the limit of terminal radar jurisdiction. At this point departure control, in coordination with the Center, has provided you with standard separation from other aircraft on IFR clearances.
Separation from other IFR aircraft is provided thus:
a. Vertically by assignment of different altitudes.
b. Longitudinally by controlling time separation between aircraft on the same course.
c. Laterally by assignment of different flight paths.
d. By radar - including all of the above.
ATC does NOT provide separation for an aircraft operating -
a. Outside controlled airspace.
b. On an IFR clearance:
(1) With "VFR conditions on top" authorized instead of a specific assigned altitude.
(2) Specifying climb or descent in "VFR conditions."
(3) At any time in VFR conditions, since uncontrolled VFR flights may be operating in the same airspace.
Of more importance to you are the reporting procedures by which you convey information to the Center controller. Using the data you transmit, the controller follows the progress of your flight. The accuracy of your reports can affect the progress and safety of every other aircraft operating in the area on an IFR flight plan because ATC must correlate your reports with all the others to provide separation and expedite aircraft movements.
Reporting Requirements. Federal Aviation Regulations require pilots to maintain a listening watch on the appropriate frequency and unless operating under radar control, to furnish position reports over certain reporting points. Any unforecast weather conditions or other information related to the safety of flight must also be reported.
If not in "Radar Contact," position reports are required by all flights regardless of altitude, including those operating in accordance with a "VFR conditions-on-top" clearance, over each designated compulsory reporting point (shown as solid triangles) along the route being flown. Along direct routes, reports are required of all flights over each reporting point used to define the route of flight. Reports over an "on request" reporting point (shown as open triangles) are made only when requested by ATC.
Position Reports. The use of standardized reporting procedures generally makes for faster and more effective communication. A standardized communication with ATC normally complies with the Radiotelephone Contact Procedures comprising call-up, reply, message, and acknowledgment or ending. Use this procedure when making position reports to a Flight Service Station for relay to the center controlling your flight. Your IFR position reports should include the following items:
3. Time. Over a VOR, the time reported should be the time at which the first complete reversal of the TO/FROM indicator is noted. Over a nondirectional radio beacon, the time reported should be the time at which the ADF needles make a complete reversal, or indicates that you have passed the facility.
4. Altitude or flight level. Include actual altitude or flight level when operating on a clearance specifying "VFR condition-on-top."
5. Type of flight plan, if your report is made to a Flight Service Station. This item is not required if your report is made direct to an ATC center or approach controller, both of whom already know that your are on an IFR flight plan.
6. Estimated time of arrival (ETA) over next reporting point.
7. The name only of the next succeeding (required) reporting point along the route of flight.
8. Remarks, when required.
During your early communications training, your reports will be clear and concise if you learn and adhere to the procedures outlined in the AIRMAN'S INFORMATION MANUAL. Often these procedures are abbreviated by both pilots and controllers when clarity and positive identification are not compromised. With increasing experience in ATC communications, you will readily learn to reduce verbiage when high radio congestion makes it advisable.
Enroute position reports are submitted normally to the ARTCC controllers via direct controller-to-pilot communications channels, using the appropriate ARTCC frequencies listed on the enroute chart. Unless you indicate the limitation of your communications equipment, under "Remarks" on your IFR flight plan, ATC will expect direct pilot-to-center communications enroute, advising you of the frequency to be used and when a frequency change is required. Failure to provide ATC with frequency information on your flight plan contributes to radio congestion until ATC can assign you a frequency suitable to your equipment limitations.
In order to reduce congestion, pilots reporting direct to an ARTCC follow special voice procedures when making the initial call-up. Whenever an initial center contact is to be followed by a position report, the name of the reporting point should be included in the call-up. This alerts the controller that such information is forthcoming.
Malfunction Reports. Pilots of aircraft operated in controlled
airspace under IFR are required to report immediately to ATC any of the
following malfunctions of equipment occurring in flight:
(1) Loss of VOR, TACAN, or ADF receiver capability.
(2) Complete or partial loss of ILS receiver capability.
(3) Impairment of air/ground communications capability.
In each such report, pilots are expected to include aircraft identification, equipment affected, and degree to which IFR operational capability in the ATC system is impaired. The nature and extent of assistance desired from ATC must also be stated.
Additional Reports. The Airman's Information Manual specifies the following reports to ATC, without request by the controller:
1. The time and altitude/flight level reaching a holding fix
or point to which cleared. (Not required when in "Radar Contact.")
2. When vacating any previously assigned altitude/flight level for a newly assigned altitude/flight level.
3. When leaving any assigned holding fix or point. (Not required when in "Radar Contact.")
4. When leaving final approach fix inbound on final approach. (Not required when in "Radar Contact.")
5. When approach has been missed. (Request clearance for specific action; i.e., to alternate airport, another approach, etc.)
6. A corrected estimate at any time it becomes apparent that an estimate as previously submitted is in error in excess of three minutes. (Not required when in "Radar Contact.")
7. That an altitude change will be made if operating on a clearance specifying "VFR conditions-on-top."