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Radar Procedures
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Contents:
FAR 91.215 Transponder Requirements;
...Web Radar; ...Radar Facilities;
...Bay Tracon; ...Oakland Center;
....Military Radar; ...ATC
radar accountability; ...VFR radar advisories;
...Class B Airspace; ...Class
C Airspace; ...Basic enroute procedure;
...The Handoff; ...Operational
Procedures; …The Best from Radar
Communications; …Radar Communication;
…ATC Radar Acknowledgment; …Transponder Failure; …The
Danger of Expectations; …
FAR 91.215 Transponder Requirements
1. Any airborne aircraft with a transponder is required to
have it on. Mode C, if available, must be used.
2. VFR use requires that Mode C be on when within 30 nautical
miles of the primary airport of Class B airspace. See Sectional.
3. Mode C is required in Class B airspace, and positive control
areas (above 18,000'),
4. Mode C is required in Class C airspace and above the lateral
limits of the Class C airspace to 10,000'.
5. Mode C is required above 12,500', below a positive control
area (Classes B and C) if over 2,500' above ground level.
6. Mode C is also required within 10 nm or airports at Billings,
Montana, and Fargo, North Dakota. (Trivia question)
Weather radar is available at the following sites.
Http://members.aol.com/weathernow/index.html
http://www.geocities.com/CapeCanaveral/6186/index.html
http://www.intellicast.com/weather/usa/radar
http://www.geocities.com/SunsetStrip/7033/weather.html#doppler
http://wxp.atms.purdue.edu/radar.shtml
Oakland Center, Bay Approach, Travis Approach
Some of the radar areas are depicted on charts and some are
not. Those depicted require that communications be established
or a clearance given be prior to arrival. The San Francisco Class
B boundaries and information is shown in blue. An additional 30nm
circle around San Francisco requires Mode C operation. The Class
C airspace around airports having radar is shown in magenta has
a ten mile inner circle in which a call up is required to approach
just as though were Class D airspace. The outer 20-mile circle
has a permissive call up.
In most situations the frequency and controller for approach or
departure will be the same. The call up to approach or departure
depends on whether you are coming or going. Your first call is
brief, who you are and who you are talking to. If you received
your transponder code while on the ground, your call-up gives
only your identification and altitude.
The latest version of traffic control (TRACON)radar is the ASR-9.
Weather circuits are included into TRACON radars but tends to
eliminate airplanes when on. Weather depiction can be turned on
but the controllers are not competent to make interpretations.
Everything changes with ASR-9. ASR-9 is similar in color and display
to aircraft radars. There are six levels of precipitation display.
Level three and higher should be avoided by all aircraft. The
controller who selects the level 3 key has all precipitation level
three and higher shown brightly, levels 1 and 2 are shown at low
intensity on the screen. As a pilot who is exposed to weather
you should be prepared to ask the controller if he has ASR-9 radar
display. Ask how many lights he has available (1 to 6) for light
aircraft anything over 1 suggests that landing is a good option.
Controller liability makes them generally reluctant to give weather
advisories without hedging what they say.
Automated Radar Terminal System ARTS has gone from ASR-4s to ASR-9s
and 11s. Everything is digitized and put on a computerized display.
ASRs have a search antenna and a secondary interrogation antenna
for triggering transponders. ASR-9s will trigger Mode S transponders
that can do everything but name the wife of the pilot. ASR-9 accuracy
is down to 1/32 of a mile close in and 1/16th at 30 miles. Even
primary (non-transponder) targets are digitally processed.
The tracking of targets is necessary to implement the Conflict
Alert and MSAW elements now being installed. MSAW (Minimum Safe
Altitude Warning procedures must be requested by VFR aircraft.
The display can overlay the EOVM (Emergency Obstruction Video
Map) which might allow a safe descent below the MVA (Minimum vector
altitude) used for IFR. The display has a DVA pie slice that allows
controllers to fan out departures in different directions and
depart more planes in less time. ASR-9s can depict weather which
means vectors around weather are available.
Bay Approach is located near hanger 10 at Oakland airport. It has multiple backup computers and two radar antennae. The #1 radar is at Oakland Airport adjacent to runway 29. The backup is at Moffett Field. The primary region of Bay Approach is the San Francisco Class B airspace which overlies the Oakland Class C airspace and part of the San Jose Class C airspace. Some of the sectored frequencies overlap. The call is always, "Bay Approach". The frequencies and sectors are on the sectional's frequencies list and shown in appropriate (blue/magenta) boxes on the San Francisco Area chart.
Oakland Center is based at Fremont on the sectional it is coded as ZOA. It has triplicate back up computers and remote communications lines from the Oregon border to Bakersfield, East to Utah and half way across the Pacific. In many instances you must be at certain minimum altitudes to establish radar contact. You may be able to communicate and still not be high enough to be in radar contact. Each sub-region of Center's airspace has a discrete frequency. ZOA frequencies are not on VFR sectionals.
Most military bases offer civilian radar service. The area may be sectored by frequency. The frequencies are available in the sectional frequency list. Call up would be as, "Travis Approach". Most of these services are limited as to altitudes. If you are climbing, you may well be handed off to ZOA (Oakland Center) after passing through a given altitude.
The controllers to expedite the movement of traffic use ATC
radar. The system is designed and operates for the convenience
of ATC. The individual pilot becomes insignificant and can only
be assured of the benefits of radar by being both proficient in
communication and aware of the limits of radar. Radar contact
occurs when ATC has identified you on the PPI display scope. Radar
contact in no way relieves you of your responsibility to see and
be seen and to avoid flight into terrain. While you are expected
to comply with any assigned headings and altitudes, you are also
obligated to question any such assignments that you deem hazardous.
ATC does not provide VFR flights with terrain separation. Terrain
avoidance is a pilot responsibility per FAR 91.119. VFR pilots
should never expect ATC to provide any warnings about terrain.
Night VFR, off-airways, or marginal VFR conditions under FAR 91.103
require special planning.
ATC radar does not show terrain. Blocks of airspace have Minimum
Vectoring Altitudes (MVA) that can be displayed. These are IFR
altitudes that allow 2000' in mountains and otherwise 1000' terrain
clearance. VFR flight below these altitudes is relatively common
but radar has no specific knowledge of terrain below the MVA.
If you have Mode-C on your transponder radar may have Minimum
Safe-altitude Warning (MSAW) or Low-altitude Alert System (LAAS)
but this is often MVA and no lower.
Radar advisories can be terminated to VFR flights just on the
say-so of the ATC specialist. There are some automatic terminations
that apply to IFR flights but can be applied to VFR situations.
It is very possible that a VFR flight may just be dropped from
the system without the pilot ever being told. You should have
some general idea of the region and altitudes for a given radar
facility. If you have not been in communications for a while,
just ask for a radio check. You may have flown off the scope without
being noticed. Never leave a radar communication frequency without
advising ATC.
ATC radar facilities primarily provide IFR to IFR separation.
Secondarily, they will give VFR traffic advisories, navigational
assistance; weather information, vectoring, ground speed and safety
precautions as work load permits. The VFR pilot is responsible
for traffic avoidance but ATC will "take over" if a
collision risk exists. VFR flight following is not a substitute
for a clearance into Class B or C airspace. When radar coverage
does not reach, flight following ceases. There are no VFR separation
standards and altitude bust may result only in ATC giving you
the current altimeter setting as a gentle reminder. With sufficient
altitude you can get flight following anywhere in the U.S. Even
at relatively low altitudes you can get it in the non-Sierra part
of California.
Getting a local ATC radar frequency is not always easy for
the VFR pilot. It may be listed in a blue box for Class B airspace
and a magenta box for a Class C. You may need to request it from
a nearby tower or FSS. The FSS frequency may not be the correct
one for your sector of radar coverage but it will get you into
the system. You could get old IFR charts and plates as a source
for radar frequencies. The way you make contact with a radar facility
makes an impression that is likely to affect the service you receive.
It shouldn't but it does. The initial contact, unlike that to
a tower or an FSS, should give only the name of the facility,
your full call sign, and possibly "over". You will understand
the 'why' of this better if you visit a radar facility. Until
then just do it.
When the controller returns your call-up, you give again your
full identification, type of aircraft, /(slash code) position
(departure point), altitude (final altitude), and your destination.
To do this well you should practice before initial call-up. Giving
the destination lets the controller select a code that lets other
controllers up the route know where you are going. The better
your flight following radio procedures, the better you will be
preparing for your IFR rating and the better overall radar service
you will receive.
Under VFR flight following you must be assertive and in charge
of your flight. Do not rely on the controller to tell you to climb,
descend or make a heading change. You just state that you and
doing so, and do it. If it makes a problem for him he will so
advise by making a "suggestion". If you get confused
or into trouble, admit your difficulty. State your willingness
to accept help. Do what you are told to do.20% of ATC controllers
are pilots many at commercial level or better.
The altitude limits of radar means that just when you need it
most, it will not be available. Much the same limits exist for
radio communications. If you are in conditions that put you both
below ATC radar and communications, it is time to get on the ground.
Many FSS or Flight Watch frequencies can be used through remote
outlets where other ATC frequencies are not available. It never
hurts to have another radio frequency option along your route.
ATC can cancel VFR advisories/following at any time. Should this
occur because of lost radar contact, you should ask for the next
available frequency that can resume these services along your
route. Most often altitude will be the limiting factor as when
flying the Sierras or other remote areas. You can monitor the
frequency you just left or expect and get some idea as to the
altitudes and conditions experienced by other aircraft. Center
frequencies are not usually available to the VFR pilot but can
be obtained from IFR charts for VFR use.
Since VFR difficulties can develop into emergencies, a VFR pilot
must know how to get ATC radar assistance and its limitations.
ATC cannot tell the pilot what to do; the pilot must make all
decisions. ATC can advise or suggest only. A pilot can request
MSAW (minimum safe altitude warning) or LAAS (low altitude alert
system) assistance but beyond that radar is limited by the system
display to providing MVA (minimum vectoring altitude) as the 'safe'
altitude. An individual controller may not have sufficient knowledge
to vector you to successively lower MVA sectors and it doesn't
hurt to ask.
It behooves the VFR pilot to learn how to use radar services in preparation for the future IFR rating. Radar is capable of providing a pilot with considerable information. With the proper transponder a pilot can be told his airspeed, altitude, direction and any changes of the three. Radar can give severe weather warnings, emergency headings to airports and traffic alerts. Being on radar or in contact with a radar facility is going to give quicker emergency help than all the filed flight plans ever written. Outside of specific airspace such as B or C any radar service is a matter of what the controller's workload permits.
Radar vectors are headings assigned to the pilot and aircraft for specific purposes such as heading for an airport or runway. Other vectors can be assigned for traffic sequencing or avoidance. Any VFR pilot using radar should not hesitate in advising of a willingness to accept radar vectors. Your ability to get radar service in addition to workload depends on altitude, terrain and radio capability. Older aircraft may not have the required frequencies for continuous or specific radar coverage. I once flew across the U.S. with a 90-channel radio. I was only able to maintain radar service with every other sector. I was always able to get the next facility or sector that could communicate with me well in advance.
Towers use a BRITE display instead of a Plan Position Indicator display most common to Approach and Center displays. BRITE is like a large TV picture. Tower specialists are required to use visual procedures even though they do have the BRITE as a backup. Should you lose your marker receiver, the tower can call it for you using the BRITE. ATC can use the picture for locating only unless trained to use it for separation. A 'letter of agreement' is required between the tower and approach before tower can acquire separation responsibility.
Most importantly, the pilot is still the total responsible person for the safety of the aircraft. Radar is only an aid, capable of offering assistance but assuming no responsibility.
Not available to student pilots in some locations and in others
students require instructor endorsement.
Be sure that you initiate Class B airspace communications early
enough to avoid entering before getting a clearance to enter.
Know your positions and altitudes in relation with the Class B
airspace so that no entry will occur prior to entry. If the controller
fails to give a clearance to enter, be sure to ask for it and
get it, before intruding into the Class B airspace. With the latest
Class B and Class C airspace requirements, it is not unusual to
have a considerable delay before establishing contact. Controllers
are often on the phone or processing data that prevents immediate
response. In the LAX area it may take five or more minutes before
a busy controller can get to a new arrival. General Aviation IFR/VFR
flights can expect few, if any, direct or shortest route flights
in Class B airspace. 250-kt maximum airspeed restriction.
Procedure
Monitor frequency to determine use. Be sure to remain clear
of Class B airspace both horizontally and vertically.
"Bay Approach Cessna 1234X over" If no response, wait
30 seconds and call up again. The controllers are often on the
phone or processing data that prevents immediate response. When
their workload permits they will say...
ATC: "Cessna 1234X Bay Approach go ahead"
34X: "Cessna 34X Birones Reservoir at 3000 squawking 1200
VFR Concord to Half Moon Bay request flight into the Class Bravo
airspace at 3500 enroute"
ATC: "34X Standby for squawk" (Standby means not to
make any response.)
ATC: "34X Squawk 0734 and ident"
Turn X-ponder to STANDBY, reset code, set to ALT, push the IDENT
button.
34X: 34X squawking 0734
ATC: "34X Radar contact" acknowledge with 34X.
ATC: "34X traffic 12 o'clock 1 mile" 737 at 2000 climbing"
34X: "34X negative traffic will accept vectors"
ATC: "34X turn right 340"
34X: "34X right to 340 have traffic"
ATC: "34X with reference to traffic proceed own navigation
via G.G. Bridge and shoreline"
34X: "34X understand own navigation"
Do not enter Class B airspace until you receive a specific clearance
to do so. Always write down squawk and frequencies. Always repeat
back squawk, frequencies, headings, and directions as much as
practical. All assigned altitudes and headings are maintained
since traffic clearances are determined thereby.
The Class C airspace system has a ten mile inner circle in which a call up is required to an ATC approach facility just as though it were Class D tower airspace. A Communications is a FAR requirement as is transponder operation in Mode C. The outer 20-mile circle has a permissive call up. Class C airspaces are charted with altitudes in magenta outlines.
Operational procedures
1. Get the ATIS
2. Use the correct frequency
3. Practice for smoothness/accuracy/completeness
4. Check for frequency congestion
5. Full aircraft identification + student pilot
6. Position and altitude
7. Request and expected reporting point
8. Initial Class C airspace call up:
"Podunk approach Cessna 1234X student pilot over."
DON'T ENTER THE Class C airspace UNTIL ACKNOWLEDGED. (No clearance
required.)
"34X (position-altitude) with ATIS and full intentions and
any special request.
Initial Tower Call-up
"Podunk Tower Cessna 1234X student pilot Position at altitude
request left base entry for the right will report 2 mile base"
Initial call-up to get into the system before you have a transponder
code (squawk)is always:
Blank Approach Cessna 6185K over
If no answer... Check your radio switches and frequency. Wait
30 seconds and try again
When ATC radar responds they need certain information for their
computer.
--Aircraft type and identification
--Present position and destination
--Present altitude and final altitude
--The ATIS letter if you are inbound for landing
There is a 'canned' procedure for saying this:
Cessna 6185K is a Cessna 150 Walnut Creek
landing Oakland out of one-thousand six hundred
for two thousand five hundred with Alpha
ATC will assign a transponder code:
1. Write down the assigned code
2. Say back the code as...
85K understand squawk 5234
3. Place selector on standby
4. Set in assigned code
5. Place selector on altitude
6. If ATC does not advise in radar contact, say
85K squawking 5234
Occasionally, you may immediately be given a squawk or just to
remain clear and standby. Be sure you understand the significance
of what ATC says. Normally, you will be assigned a squawk and
may or may not be told to IDENT. Do not IDENT unless told to.
The IDENT button causes a flashing IDENT to appear on the controller's
scope adjacent to your data block. The discrete transponder code
does more than just identify the aircraft. It often is used as
a destination indicator so that other sector controllers know
where you are going.
If the controller says "Radar Contact" acknowledge with
your last three call letters. If for some reason no secondary
target (transponder) is seen, you may be requested to recycle.
This means to reset the numbers perhaps providing better electronic
contact.
All instructions, traffic point-outs must be repeated back to
the controller in acknowledgment with aircraft identification.
Any changes of altitude or direction must be communicated to ATC
and authorized by the controller.
When you leave a radar service area the controller will so advise
you and ask you to squawk VFR (1200) and approve a frequency change.
You must never leave contact with ATC approach/departure without
such an approval. If you need to change frequency to contact Flight
Watch or an FSS just request a 30-second frequency change. You
will be told to report when back on frequency.
The area around a radar facility or antenna is divided into
both horizontal and vertical sectors. This means that as you proceed
you will be changed from one controller to the next. This is called
a handoff. The controller will, prior to informing you of the
hand off, tell the next controller via phone/computer that you
are coming and the particulars about your aircraft and operation.
Then he will advise you of whom to contact and on what frequency.
Once the controller has completed your data block this information
can be passed via computer from sector to sector or between facilities.
For this reason the 'handoff' requires a minimum of communications.
As you transition from Travis airspace to Sacramento Class C airspace,
the controller will say...
"85K contact Sacramento Approach on 118.8"
Acknowledge any handoff by repeating back the place and frequency
assignment.
"85K going to 118.5 with Sacramento Approach."
1. Write down the new ATC name and frequency
2. Repeat back the essentials for confirmation
3. Set new frequency and establish contact
4. Check for congestion before using radio
5. You must request any changes of altitude or course while
6. In Class B airspace. You must advise on any changes in altitude
or course in Class C airspace or other radar areas when in contact.
7. At any time ATC may assign an altitude and heading for safety
purposes. If no such assignment is made you are free to make changes
as long as you keep them advised of your intentions.
The radar controller as part of FAA Order 7110.65, Air Traffic Control paragraph 2-16b is required to coordinate with other ATC facilities such as a tower your passage through their areas. You are not expected to obtain your own authorization since it would detract from your ability to maintain radio contact with your primary facility. However, if you have a specific need to contact a facility such as flight watch, FSS, or tower it is appropriate to request a 30-second frequency change for such contact. You must report back on frequency when through.
A radar traffic advisory usually gives a 'clock' direction off your nose, a distance and an altitude. Expect the 'clock' to be wrong by an hour or so. You are unlikely to see any small aircraft beyond 5 miles and in haze the distance may be less than a mile. You immediately advise, "85K looking, 85K have traffic, 85K negative traffic" as appropriate. If you can't find the traffic and feel it constitutes a hazard wait 30 seconds and say, "85K negative traffic, will accept vectors." You do this because ATC may wait too long to give you warning or to turn you. Most often they come back with, "85K traffic no longer a factor". You read back everything a radar controller tells you to do. This procedure is to prevent misunderstandings.
The radar handoff requires that you read back the instructions
given and the frequency. If you have been listening to what other
aircraft have been told you should be expecting the change. The
controller has already told the next controller/facility, electronically,
that you are coming. They are expecting you. Don't be in too much
of a hurry. When a break in the frequency occurs, the handoff
call requires you merely to state, to whom you are talking to,
your identification, and altitude.
You say...
85K to Sacramento Approach on 118.8
You then change frequency to 118.8 and say...
Sacramento Approach Cessna 85K level at five thousand five hundred
Say this every 30 seconds or so until acknowledged.
There is a procedure for changing from one transponder code
to another designed to prevent the inadvertent selection of a
restricted code as the one for Air Force One.
Procedure:
1. Standby
2. Select new code
3. Altitude
Have a pencil ready in your hand you can keep it there while holding
the yoke (lefties) or while holding the throttle (righties)
The Best from
Radar Communications
There are some radio procedures that are relatively infrequently
used by new pilots. In this tome I will attempt to clarify why
some of the distinctions exist and what to say, when. The proper
radar frequency is often not available to the VFR pilot. If you
know a facility exists, such as Center, the local frequency can
be obtained by contacting a local tower or an FSS. Every sectional
chart has a Facilities Frequency section behind the chart legend.
The initial radio call for such a frequency should end in the
word "request" as "Napa Tower Cessna 1234X request"
(All radio communications will be written without punctuation,
just as they should be spoken.)
Approach control is a radar facility as is the Air Route Traffic
Control Center. The communications procedures are identical. The
major difference lies in distances and altitudes. Approach is
usually within thirty miles of a particular airport. Approach
can be contacted directly for flight advisories (Preferred over
flight following) which warns you of potential traffic conflicts.
Such advisories are required for IFR flights but on work-load
basis for VFR. Radar does not relieve a pilot from situational
awareness or see-and-be-seem responsibility. Frequencies are available
in the A/FD, charts and IFR plates.
When your flight takes you from one radar sector or facility to
another the radio procedure is to only give the name of the new
facility, your aircraft identification, and your altitude relationship
as level at, out of (altitude) for (higher/lower) altitude. If
no handoff is involved you give the name of the facility, your
aircraft identification followed by "over". Read back
any ATC transponder settings, frequency changes, to ident, headings,
turns and traffic. Advise when traffic is in sight or "negative
traffic'. The way you say things is just as important as what
you say. When ATC answers, be prepared to give the following information:
1. Aircraft identification
2. Aircraft type
3. Location
4. Altitude
5. Intended route or destination.
Every radar facility is required to obtain at least one confirmation
of altitude with every contact. You can save time by including
your altitude with every initial contact with a radar facility.
Always advise ATC if you are planning to change altitude when
VFR. IFR pilots are required to report descending out of any altitude
as well as the altitude they are descending to.
The initial callup to every radar facility is the same. It makes
no difference if you are dealing with a Class B or C, an approach
/departure, traffic control (TRACON), or a center.
Initial Call
Name of facility, full aircraft identification + "Student
pilot" over
Example:
"Travis Approach Cessna 6185K student pilot over"
The reasons for this brevity is because the radar controller has a multiplicity of tasks. In addition to your frequency he may have a military one. He has a phone line for contact with controllers of adjacent areas. He often records data and writes notes. In low traffic periods one controller may have two areas and two frequencies. Under certain workload/weather conditions VFR advisories may not be possible. When this condition exists you will be so advised. A visit to a radar facility will help you be more understanding as to why the controller does not answer immediately.
A more distant initial callup procedure allows the controller to select when to contact you as his workload permits. Wait at least 30 seconds before calling again. The more efficiently you communicate the more likely it is that you will be accommodated since good communications reduce the workload.
ATC
Radar Acknowledgment:
Make NO response if told to standby. When the controller is able
you will be told to go ahead. However, you may be occasionally
'forgotten'.
Example:
"Cessna 85K go ahead with your request"
When the controller acknowledges your existence give the particulars
of your flight and aircraft. Occasionally, a transponder squawk
will be immediately assigned only to be modified to indicate additional
information later on.
Full call sign; type of aircraft; Present position; present altitude
and enroute altitude; destination; and
request
Example:
"Cessna 6185K is a 150, off Concord for Half Moon
Bay out of 2000 for 2800 via Golden Gate Bridge requesting
flight advisories"
The controller will ask for anything you leave out. The type information is added to the radar data block by the ATC specialist. The present altitude information is used to check the accuracy of your transponder encoder. Once you are established at an altitude do NOT leave that altitude without first advising ATC. As a VFR pilot you are allowed to select your own altitude as long as it follows the hemispheric rule for your direction. To change you must first advise ATC. Alternatively, ATC may assign you an altitude, in which case you must request approval of any change. Your transponder code assignment will indicate IFR/VFR and destination.
The importance of correct, concise, and accurate communications when dealing with a radar facility is essential. You are required to fly assigned headings and altitudes. If you wish to change heading or altitude advise ATC. If there is a traffic conflict ATC may provide an alternative. Always write down squawk and frequencies. Always repeat back squawk, frequencies, heading, and directions as much as practical. If you need something repeated, say so. If you cannot visually locate conflicting traffic, do not hesitate to indicate that you will accept (want) a vector for traffic avoidance.
When given a handoff to another sector you just have to tell
the controller your altitude. Every radar controller is required
to check your transponder-readout accuracy at least once so get
it over with right away.
Example:
"Sacramento Approach Cessna 6185K level at 6,500"
ATC will assign a squawk and confirm your Mode C operation by saying,
"85K squawk 5234 say altitude ident"
Do not believe that being on radar relieves you from 'see and
avoid' responsibility. As a VFR flight you are relatively low
on the ATC totem pole. When ATC radar advises you of nearby traffic
you should acknowledge the 'point out' with.
Example:
"85K have traffic"
Do this only if you are sure of the traffic direction, distance
and aircraft type. If you are uncertain or have failed to see
any aircraft of the type indicated you say,
Example:
"85K negative traffic"
If after thirty seconds to a minute you still have not identified
the traffic and you feel that a hazard may be involved, you should
request vectors for avoidance by saying,
Example:
"85K will accept vectors"
The controller may indicate that traffic is no longer a factor
or may give your a vector by saying,
Example:
"85k turn to 030"
Your response will be the direction of the turn and the heading
given so as to establish the certainty of your instructions.
"85k left/right to 030"
When you are clear of the traffic ATC will instruct you to resume your own navigation.
If your transponder is not making a reply or is giving the wrong code ATC will request that you recycle. This means to turn it off then on and roll through the numbers again. This often is sufficient to fix the problem. If some aspect of transponder operation is unsatisfactory ATC can usually work with a primary signal. Under the escape clause "unless otherwise authorized or directed by ATC" you can be given a waiver. The willingness to ask for help when you need it from ATC is more important than whether your transponder is working. Not only can ATC give you vectors they can give you 'no gyro' aid that will get you out of IFR conditions into VFR.
At some point on a flight either you or ATC may wish to end
radar service. You merely ask for a frequency change.
Example:
"85K have Concord in sight frequency change"
"85K frequency change approved squawk VFR"
Transponder
Failure
If you should experience a transponder failure, be cautious
about accepting flight into a radar environment where radar is
the prime system. Once you land at a Class C airport without a
transponder you may be unable to get out. Trick: Try to get piggy-backed
on to another aircraft as a flight of two. Nice if you can get
out in the direction you want to go. Radar can track a primary
signal with little difficulty today. They can even attach a data
block. Planed flights into Class C or even B require one hour
notice
--First malfunction check is the reply light
--Some older military radars have difficulty with Mode C. Check
with TRACON or Center for Mode C.
--Gear land flaps down may block reception or transmission.
--Turn off DME to see if signals are in conflict.
--Encoder must be reading within 300 feet or ATC will have you
change mode.
The
Danger of Expectations
When you look outside an aircraft you have expectations. If
ATC has called a 'point-out' you expect to see an aircraft. You
have a right to assume that you will see an aircraft. However,
the quality of the 'point-out' very much depends on what you will
actually see. It is not unusual for what you are looking for to
be off in azimuth as well as distance. An aircraft 'point-out'
that is off by 20 degrees may be well outside your focal vision.
An aircraft called as being three miles away is the size of a
fly at ten feet. Your visual shortcomings as well as ATC misdirection
may lead to trouble.
--It takes two seconds to focus on a distant object.
--It takes 12.3 seconds to evaluate, determine the threat and
take evasive action.
--Vast majority of midairs occur in VFR daylight near traffic
areas.
--Head on aircraft on the horizon do not move on the windshield.
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