Flight Check of IFR Navaids by FAA
--Specific intervals
--Fix accuracy
--Centerline
--Missed obstacles
--Approach obstacles
--Fly edges of approach area
--Fly approach all the way at minimums
Letters-of-Agreement
An LOA puts in writing the extent to which ATC can pass information from sector to sector and airspace to airspace by Standard Operating Practice (SOP). These LOA/SOPs cover parachute jumping, military operations, airspace delegation, SVFR procedures, emergency responsibility, and IFR procedures.
The 20 centers of the U.S. subdivide authority and responsibility to other facilities through LOAs. The LOA set airspace dimensions, procedures, responsibility, authority, time periods, sectors. LOAs can exist between two airport Class D airspaces. Pre-set LOA reduces the communications and procedure stress by working according to a plan.
Different divisions of ATC have developed methods of moving traffic via a system that is relatively unknown and unknowable to pilots. Towers can launch traffic into TRACON air space as part of a departure clearance including a transponder code that tells TRACON about the aircraft.
TRACONs work on a system of 1000' vertical separation and three mile lateral separation. LOL aircraft will depart along a route with an altitude restriction so that the departure allows multiple aircraft to get in the air and on their way. This is a pre-coordinated procedure developed in-house by ATC to make a system work where otherwise it wouldn't.
APREQ is a variation of the LOL in which individual controllers make an 'Approval Request'. A controller from one position are moved to other conditions to help maintain a wider awareness of the entire system. A pilot request may require that a controller make an APREQ to allow a selected aircraft to intrude into another controllers airspace to facilitate its movement. As a pilot, knowing that APREQ exists makes it possible for me to take airway shortcuts that avoid extensive en route excursions.
Every controller is give a three dimensional airspace designed to keep similar procedures together and make the workload reasonable. I once sat for 15 minutes at a sector screen where the controller had to talk like a tobacco auctioneer because the supervisor had combined his sector with another. It was disconcerting to see how this controller was so loaded up. One incompetent pilot could have sent the entire mess into a collapsing house of cards.
Major ATC Pilot Problems
--Entering ARSA/TCA without authorization
--Runway incursions
--Altitude deviations.
ATC Separation
ATC separation is done in three dimensions, vertical, lateral, and longitudinal.
Vertical separation is based on altitude. The amount of altitude separation is different for IFR from IFR and IFR from VFR and VFR from VFR. The hemispheric rule usually applies but is often evaded when aircraft are being sequenced for approach, separation will be maintained. Obstacle clearance is 1000'. Every altitude assigned must be above the minimum vectoring altitude. (MVA) VFR aircraft can be cleared to fly below the MVA.
Once cleared for IFR you are separated in all airspace except Class G. An IFR pilot can fly in Class G without dealing with ATC but without ATC being at all responsible. ATC will separate only IFR from IFR in Class E airspace. The tower of Class D will do its best with or without radar to provide separation but VFR separation is not guaranteed. Class C ATC separates all IFR from IFR as well as VFR inside the 10 mile ring. In the 20-mile outer ring of Class C IFR from IFR is provided but not from VFR. This is because VFRs are not required to accept ATC control between the 10 and 20-mile arcs.
TRSAs which surround some Class D airspace separate IFR from IFR but not from VFR since VFR is not required to participate. Class B provides total separations of everybody from everybody else. Class A gives total separation. 18,000 to 29,000' IFR from IFR is 1000'; above 29000' its 2000' vertical.
Lateral separation from displayed obstacles is 3 miles. Visual separation is not allowed by IFR aircraft from obstacles, even if in sight. Radar separation remains in effect. ATC radar is used to maintain airspace separations such as special use airspace (SUA) and jump zones.
Longitudinal separation is normally 3-miles in trail. The aircraft in front cannot be heavier than the plane behind and the tower must be able to see the runway's turnoffs. Where wake turbulence is a factor four-mile separation is required by small aircraft behind large aircraft and five miles behind the 757. Small aircraft must be six miles behind very large aircraft. Small aircraft are all that weigh less than 41,000 lbs. Once a pilot accepts responsibility for separation by saying that he has a 'point-out' in sight then what happens is totally his responsibility until he says he has lost sight again. Best option is to request vectors for greater spacing.
When you ask ATC for a change in altitude, you must realize that what happens TOTALLY depends on the amount of separation such a change would allow. Those of you who fly slick airplanes realize that failure to descend means that you will have difficulty slowing down when you get closer in. The turbo does not enjoy being shock-cooled. Just last week we were denied a descent and vectored on to the ILS just in time to have a false glide-slope center. The same thing had happened several months before and the required rate of descent could not be maintained because of the turbo. We executed the published missed far above DH. This time we expedited the descent to catch the FAF altitude check but it was neither pretty nor smooth.
On the missed we headed toward another airport and were shortly informed that we could expect a long hold. I had the pilot slow to approach speed some 15-miles out from the holding fix. Just as we got to the fix we were cleared for the approach. Piece of cake. Our slowing gave the controller the separation that he needed so we did not need to hold.
Final Approach
On final you should realized that at the outer marker you are five miles out and 1500’ above the runway. Within the lateral limits of the CDI the slope or steps of the approach will keep us above any obstacles. As we descend to 200’ above decision height the lateral limits become so constrained that full CDI deflection occurs at the end of the runway in only 500’. Properly flown you have guaranteed obstacle clearance. The new TERPS criteria obstacle clearance above obstructions at five miles is 755’ and at DH the new criteria provide 122’. Non-precision approaches provide 250’ obstruction clearance throughout the approach. The lights that have reference value for an approach and landing are the runway lights, the end identifiers, approach and VASI.
Block Altitudes
There will be times when IFR flight conditions make it difficult to impossible to maintain an altitude. Actually almost any time you can request a block altitude. The block gives you a practice playground between two altitudes that are above the minimum instrument altitude of FAR 91.177 or minimum vectoring altitude. This way you can legally fly so as to be actual by picking up clouds a few hundred feet higher or lower inside your block. Cloud scooping it is called.
ATC RADAR Sectors
Controllers live by rules in 7110.65. A radar controller separates aircraft as they move through "his" airspace. ARTCC or Air Route Traffic Control Center cover all the wide open spaces between Terminal facilities. Terminals funnel aircraft to and from their airports. Airspace is transferred from ARTCC to Terminals and thence to airports by Letter of Agreement (LOA)s. "Letters of Agreement", often unpublished and unknown to pilots, exist between ATC facilities. These letters allow special flight routes, altitudes and procedures.
"Radar contact" does not guarantee terrain clearance any time you are below MOCA or MEA altitudes. ATC radar airspace is different than a pilot's airspace. A tower may by LOA (letter of agreement) lose control of a part of its space under certain weather conditions or because of the needs of an adjacent airport approach. It helps the pilot to know the ATC preferred direction of traffic and airspace alignment. Hayward has a LOA with TRACON to release the top 1000' of its Class D airspace at all times. Alameda has a similar agreement. CCR and APC release to Travis control of airspace above a fixed altitude during IFR conditions. This appears to the pilot as part of the SVFR clearance.
Some sectors and frequencies are more "quiet" than others. On weekends sectors may be combined so the frequency you normally select will be only monitored so as to assign the active frequency. One sector will feed into another sector by means of a "handoff" Several such sectors may feed to a final controller. If too many aircraft are loading up the final sector some of the outlying sectors may be required to "spin" (hold) aircraft to lessen the final controller's load. The "spin" may consist of a completely different routing.
The handing off of an aircraft from one sector to another requires coordination. This means asking approval via phone/computer of the adjoining sector's controller if the will accept another aircraft. Controllers are not allowed to violate adjoining sectors. Your vector may be simply to avoid an adjacent sector. Every favor one pilot receives, delays another. The controllers can't make all the phone calls in time to meet requests in complex environments. Computerized handoffs are rapidly replacing the phone.
Aircraft on the controllers screen have a data tag that gives call sign, type, groundspeed, altitude readout and may include destination, type of flight and a controller letter of identification. The new automated handoff has some problems since the airspace sectors is often subdivided several times. When a controller notes that an aircraft is leaving his airspace he tells the computer. The computer then decided who gets the aircraft. The originating controller may not know who gets it. If the aircraft fails to make the proper radio contact we have a loose cannon in the system. When the Mode S transponders get used every aircraft will have a permanent code.
A "pointout" is similar to a handoff but allows an aircraft to nip through a corner of a controllers airspace without changing frequency or making radio contact. ATC can do this without the pilots knowledge.
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