|
6. Change of Plans
6.1 Vectors
6.1.1. Lateral Vectoring
6.1.2. Vertical Vectoring
6.1.3. Conditional ATC instructions
6.1.4 Calculating the TOD
6.2. Re-routing
6.3.Holdings
6.3.1. Concept
6.3.2. .Usage
6.3.3. Flying a Hold
6.3.4. Holding Clearance
6.3.5. Standard Holding Pattern
6.3.6. Non Standard Holding Pattern
6.3.7. Holding Entry Procedures
6.3.8. DME Holdings
6.3.9. published en-route and Terminal Chart Hold Patterns
6.3.10. Estimated Approach Time
6.3.11. Examples and Recap
6.4. Speed
6.4.1. General Concepts
6.5.2. So what does this all mean?
6.4.3. Minimum Speed
6.4.4.Speed Restrictions
6.4.5. Conversions
6.4.6. Summary
To
download this chapter... right-click and select "Save
destination as ..."
6.1. Vectors [S]
As
ATC we tell aircraft what to do, what route, heading or track to
follow, as well as what Flight Level to fly at. In essence ATC has the
right to instruct any aircraft to turn in any direction depending on
local circumstances.
When dealing with lateral separation we speak about vectoring and when
dealing with vertical separation we speak about climb or descend
instructions. (in fact all of these are a kind of vectors)
In order to issue either of the above correctly, efficiently and above
all purposefully you need to have the Area Charts and know the airspace
around you.
There really is not that much that can be explained about radar
vectoring as it is something you will pick up and learn as you progress.
The Main thing to bear in mind is “Do not Over Vector”.
What we mean by this is keep your instructions to the point, do not
tell the pilot what to do every 2 minutes, don’t ask the pilot to
report in every 5 minutes. There is absolutely no need for this and
above all think ahead at all times.
Back
to Top
6.1.1. Lateral Vectoring [S]
9.1 VFR – Visual Flight Rules
|
|
Let us start
with an explanation here of what navigation is. This is more relevant
to pilots, but from time to time you get a pilot who has just un-packed
his Flight Simulator, joined VATSIM, fired it all up, come on line
being totally new and does not know the difference between a VOR and an
ILS.
The essential component of navigation is the concept of direction and this applies both to Pilots and to ATC.
Let us consider
the above diagram: bearing in mind that a VOR has 360 different Radials
or if you want 360 compass degrees, where 360 degrees (note that 000
does not exist) indicates North, 90 degrees East, 180 degrees South and
270 degrees West.
- Heading: The direction the nose of the aircraft is pointed at
- Course: The direction over the ground that the PIC want to fly
- Track: The actual path over the ground which the aircraft is following
- Wind Correction Angle: The angle used to compensate for wind drift.
- Radial: The direction from a navigation aid (outbound)
- Bearing: The direction to a navigation aid (inbound)
Now that we
have established the most basic components dealing with direction or
lateral navigation we will look at a few things you as ATC need to bear
in mind when controlling.
When issuing a HDG advice to an aircraft, always use a direction ending on 0 or on 5.
ExAir123, Turn Right Heading 090, or Left Heading 155
If we once again refer to the above diagram, keep in mind that the
radials of a VOR (all 360 of them) extend from the VOR. Therefore if
you instruct an aircraft to leave VOR ABC on Radial 360, Direct to VOR
XYZ, the aircraft will point its nose to heading 360 and will be flying
the inbound leg towards VOR XYZ on Radial 180, but on a Bearing of 360.
When issuing Left or Right turn instructions to an aircraft, keep the
turn radius in mind, as the heading the aircraft ends up on after
leveling out, may very well be the heading you instructed but on a
different track altogether. Therefore add the expected variance to the
head instruction.
The higher the speed at which an aircraft is flying, the larger turn radius is needed to come to the heading instructed by ATC.
For instance an Aircraft is flying a heading of 190 but you want it to
be at a specific point, showing a heading or track of 130 at a
particular moment in time. Instead of instructing the aircraft to turn
Left hdg 130, add another 5 to 10 degrees that you want the aircraft to
turn, in this instance to intercept your desired points, instruct the
aircraft to Turn Left Hdg 120.
The above example depends on a number or factors, such as speed of
aircraft or speed and direction of wind. As you become more experienced
you will automatically get into the habit issuing these
corrective-heading instructions.
Most of your active vectors will be when you as ATC have traffic
inbound to a field that either requires ATC vectors for the approach
due to not being able to follow a STAR or who need to be vectored away
from conflicting traffic or vectored for the sake of maintaining or
increasing separation on approach or final.
A good Controller will always explain to the pilot the reason for the
vector instructions being issued. For instance a pilot is following a
published STAR and ATC decides to deviate from this STAR
ExAir123 Turn Right heading 120 expect vectors for approach runway 05L
Back
to Top
6.1.2. Vertical Vectoring [S]
Let us start by recapping on the two main concepts to use when giving climb or descend instructions:
Flight Levels
Used for aircraft flying Above the Transition Altitude, Transition
Level or for Aircraft climbing through and above the Transition Layer
The Altimeter in the aircraft is set to Standard Barometric Pressure 1013 (QNE)
Altitude
Used for aircraft flying below the Transition Altitude or for Aircraft descending through and below the Transition Layer
The Altimeter in the aircraft is set to Local QNH pressure.
When instructing an aircraft to climb or descend to a Flight Level
below FL100, omit the initial “0” from the
FL.
ExAir123 Climb and Maintain FL80
or
ExAir123 Descend and Maintain FL60
Remember to ensure that the aircraft are at a correct Altitude when
nearing the Final Approach Fix (a good rule of thumb is 3000FT at 10
miles from the Runway.
Remember that aircraft fly slower and use more fuel at low altitudes
than at higher altitudes; it is therefore pointless getting an aircraft
down to 5000ft or 3000ft with 50 or 60 miles to go until on final.
Try to avoid the Descend/maintain/descend again/maintain etc situation
and instead aim for a continuous and fluid movement where the aircraft
at all times is gently descending, if needed advice the Pilot the Rate
of Descend he should follow.
Another advice that ATC can give to a pilot which helps the pilot to
choose a good rate of descent is to advice the pilot of the
remaining track-miles to thouchdown
ExAir123 expect 45nm to touchdown, when ready decent to 4500ft, QNH 1020
Back
to Top
6.1.3. Conditional ATC instruction [S+]
As ATC you can issue specific constraints or conditions in a climb or descend instruction
An instruction could be conditional on the aircraft having to pass a given FL or Altitude over a Fix or Navaid.
ExAir123 Climb To Reach FL150 at GED VOR
This would instruct the pilot to climb towards FL150 and reach this level at GED
It could also be an advice to the pilot to expect further action after having passed a navaid
ExAir123 After Passing GED VOR Descend to 5000 feet
An instruction could be conditional on the aircraft having to pass a given FL or Altitude at a specific time.
ExAir123 Descend To be at FL180 At 20.15Z
But it can also be that ATC needs specific action to be taken at a given time.
ExAir123 Expect Further Climb At 20.15Z
Similarly as ATC a pilot can be instructed to expedite a Descend or a Climb
ExAir123 Expedite Descend until passing FL90
If you have
instructed a pilot to “expedite” climb or have issued a
conditional minimum climb per minute for what ever reason, and the
pilot is unable to maintain this rate of climb after a time, then the
pilot will continue climb to what ever Level he has been cleared to at
his Best Rate of Climb
ExAir123 Climb to FL280 maintain 3000 feet per minute until passing FL250
App ExAir123, passing FL220 unable to maintain 3000 FPM
ExAir123, Continue Climb to FL280 at best rate of climb
Or ATC can instruct a pilot to Stop his climb or descend
ExAir123 Stop Climb at FL120
Usually followed by
ExAir123 Continue Climb to FL240
ATC can also issue conditional report instructions to a pilot
ExAir123 Report Leaving FL330
Or
ExAir123 Report Reaching FL190
Or
ExAir123 Report Passing FL100
Or
ExAir123 Report Passing LBE VOR
If ATC needs urgent action from a pilot then the word immediately is used
ExAir123 Descend FL230 immediately
Back to
Top
6.1.4. Calculating the TOD [S+]
There are
several ways to calculate the Top of Descend (TOD), lets take an
example of a Jet Flying at FL330 with a GS of 530 (average TAS of
a Jet at Cruise Speed is 8 nautical miles per minute.
Method A
= Altitude divided by average rate of descent will give the descent
time in minutes. Multiply this by the average ground speed, which will
give you the approximate distance required
Explanation: FL330 at 2500 fpm aircraft needs 13 minutes at average 8 miles per minute
So 13x8=104nm, next add 5 to 10 miles for the deceleration and approach
segments and the aircraft should commence descend approximately 115
miles out.
Method B
= An aircraft looses 300ft each nm on a 3 degree glide, so from FL330
the aircraft will descend at 33000 divided by 300, equals 110nm, again
add between 5 and 10 nm for deceleration and approach and again the
descend should start 115 to 120 nm miles out
Another aircraft is cruising at FL310 and you want it to be at FL250 in
40nms. 40 divided 8= 5 minutes. The Difference in FL is FL60 or for
ease 6000ft, divide 6000 by 5 minutes and the aircraft should be
instructed to descend with a minimum rate of descend of 1200fpm.
If you have 2
or more aircraft following the same track with identical destination
but maintaining different FL on cruise and you want them to descend.
Never instruct the trailing aircraft, even if at a higher level to
descend before the Leading aircraft.
If you are unsure when to instruct a pilot to descend, you can issue a
“descend at Pilot Discretion” This means that the pilot may
opt to descend immediately or may opt to maintain current FL until the
pilot decides to commence descend.
ExAir123 When Ready Descend to FL90
Avoid asking the Pilot to report altitude as you can clearly see that
on your radar, unless it looks like the aircraft is not where is
supposed to be.
Back to
Top
6.2.Re-Routing [S+]
ATC
can reroute an aircraft away from its filed flight plan either with the
aim of providing a more direct route or short cut to the destination or
any other significant Navigation Aid filed in the plan, or for the sake
of maintaining separation between aircraft or to maintain an orderly
approach into a saturated field or to expedite the flow of air traffic.
It can also be used to assist pilots in circumventing adverse weather areas by vectoring them around these areas.
ExAir123 Re Cleared direct to HAM
Or
ExAir123 from present position proceed direct Ham
Directs or Re-Routes will usually be given by the Center Controller
and the rule is that the direct clearance limit has to be within ones
own FIR. For example if you are controlling Barcelona Control you
cannot give a direct to Zurich, but only to the border of your own FIR.
In the event however that Marseille Control is on line then you could
coordinate between you an acceptable direct route and offer this to the
pilot.
A different kind of re-routing is provided by Departure or Approach respectively. For example you are on as Departure:
Departure, Good Afternoon ExAir123 with you passing 2000feet on the LOPIK1F
ExAir123, Good afternoon Turn Left Heading 170 direct LOPIK, then climb FL190
In the above example Departure has re-routed the aircraft direct to
LOPIK intersection instead of having to follow the prescribed SID.
Another type of re-routing occurs when a pilot decides to divert to an
alternative airport due to adverse weather condition or fuel shortage
Back to
Top
6.3.1. Holding Concept [S+]
In aviation, a
holding (or hold) is an area of airspace used to delay aircraft already
in flight. Because fixed-wing aircraft cannot stop in midair, they fly
in circles, which keep them near their destination airport until it is
their turn to land.
A holding for IFR aircraft is usually located over a radio beacon such
as a NDB or a VOR, this is called the holding fix. Aircraft will fly
towards the beacon, and enter a a fixed racetrack pattern
over the beacon. A standard holding pattern uses right-hand turns and
take; Depending on FL flown; approximately 4 to 5 minutes to complete
(one minute for each 180 degree turn, and two one-minute to one and a
half minute straight ahead sections) . Deviations from this pattern are
common, if long delays are expected longer legs (usually two or three
minutes) may be used or aircraft with distance measuring equipment may
be assigned holds with legs defined in nautical miles rather than
minutes. Less frequent turns are more comfortable for passengers and
crew.
A holding for VFR aircraft is usually a (smaller) racetrack pattern
flown over something easily recognizable on the ground (such as a
bridge, highway intersection or lake).
In our VATSIM environment we often have to do with pilots who have
little or no knowledge on how to fly or follow a Holding Pattern or who
my have some idea but do not have the charts.
The positive side of things however is that most of our traffic has
sophisticated FMS on board which in most cases should be able to fly
the hold.
Although of more importance to pilots, ATC must be familiar with all
Hold related concepts, especially as you will be issuing the hold
instructions. Let us therefore look at the components of a hold in more
detail.
Back to
Top
6.3.2. Usage [C]
The primary use
of a holding is delaying aircraft that have arrived over their
destination but cannot land yet because of traffic congestion, poor
weather, or unavailability of the runway. Several aircraft may
fly the same holding pattern at the same time, separated vertically by
1,000 feet or more. This is generally described as a holding stack or
stack. As a rule, new arrivals will be added at the top. The aircraft
at the bottom of the stack will be taken out and allowed to make an
approach first, after which all aircraft in the stack move down one
level, and so on. ATC controls the whole process.
One airport may have several holdings; depending on where aircraft
arrive from or which runway is in use, or because of vertical airspace
limitations.
An aircraft with an emergency will be allowed to bypass the holding and
proceed via vectors directly to the airport of course this would cause
further delay to other
aircraft already in the stack.
Remember that you can have more than 1 aircraft holding at the same
fix, this is called “Stacking” where the 1st aircraft is
holding at the lowest FL and so forth. As aircraft are cleared out of
holds, they are cleared from the Lowest FL. This means that all
aircraft in the hold are then sequenced down to a lower FL and a new
aircraft about to enter the hold will enter at the highest flight level.
Once you as ATC want to clear the aircraft out of the hold you just instruct the aircraft to fly a new heading or to a new fix.
Back
to Top
6.3.3. Flying a Hold [S+]
Most aircraft
have a specific holding speed published by the manufacturer, this is a
speed at which the aircraft uses the least amount of fuel per hour,
this a relatively low speed compared to en-route flying. A typical
figure for airline aircraft is 180 to 230 knots. If possible, a holding
is flown with flaps and landing gear up to save fuel.
Maximum holding speeds are established in order to keep aircraft within
the protected holding area during their one-minute inbound and outbound
legs.
As a rule of thumb the Speed to be flown depends on the altitude or flight level the aircraft is at within the hold as follows:
- At 6,000' MSL and below: 200 knots
- From 6,001' to FL 140: 230 knots
- At and above FL140: 265 knots
Having entered
the holding pattern, on the second and subsequent arrivals over the
fix, the pilot would execute a right turn to fly an outbound track that
positions the aircraft most appropriately for the turn onto the inbound
track. When holding at a VOR, the pilot should begin the turn to the
outbound leg at the time of station passage as indicated on the
TO–FROM indicator.
The pilot would then continue outbound for one minute if at or below
FL140, or one and a half minutes if above FL140 and then turn right to
realign the aircraft on the inbound track. A Complete hold should take:
- FL140 and below 4 minutes
- FL140 and above 5 minutes
These times do not take any wind into consideration as such the pilot
should make due allowance in both heading and timing to compensate the
wind effect.
After the initial circuit of the pattern, timing should begin abeam the
fix or on attaining the outbound heading, whichever occurs later. The
pilot should increase or decrease outbound times, in recognition of
winds, to effect 1 or 1 1/2 minutes (appropriate to altitude) inbound
to the fix.
Pilots are to advise ATC immediately if airspeeds in excess of those
specified above become necessary for any reason, including turbulence,
or if unable to accomplish any part of the holding procedure. After
such higher speed is no longer necessary, the aircraft should be
operated at or below the specified airspeeds, and ATC notified.
After departing a holding fix, pilots should resume normal speed
subject to other requirements, such as speed limitations in the
vicinity of controlled airports, specific ATC requests, etc
At all times ATC needs to bear in mind the Minimum Holding Altitude
(MHA) which is the lowest altitude prescribed for a holding pattern
that assures navigational signal coverage, communications and meets
obstacle clearance requirements.
Back
to Top
6.3.4. Holding Clearance [S+]
A holding clearance issued by ATC includes at least
(a) A clearance to the holding fix.
(b) The direction to hold from the holding fix.
(c) A specified radial, course, or inbound track.
(d) If DME is used, the DME distances at which the fix end and outbound end turns are to be commenced.
(e) The altitude or FL to be maintained.
(f) The time to expect further clearance or an approach clearance.
(g) The time to leave the fix in the event of a communications failure.
During entry and holding, pilots manually flying the aircraft are
expected to make all turns to achieve an average bank angle of at least
25˚ or a rate of turn of 3˚ per second, whichever requires the lesser
bank. Unless the ATC clearance contains instructions to the contrary,
or a non-standard holding pattern is published at the holding fix,
pilots are expected to make all turns to the right after initial entry
into the holding pattern.
Occasionally, a pilot may reach a clearance limit before obtaining
further clearance from ATC. In this event, where a holding pattern is
published at the clearance limit, the pilot has to hold as published.
Where no holding pattern is published, the pilot has to hold in a
standard pattern on the inbound track to such clearance limit and
request further clearance.
If for any reason a pilot is unable to conform to these procedures, ATC should be advised as early as possible
Back
to Top
6.3.5. Standard Holding Pattern [S+]
- Standard Hold A hold where all turns are made to the right
- Non Standard Hold A hold where all turns are made to the left
- Holding Course The course flown on the inbound leg to the holding fix.
- Inbound Leg The standard 1 or 1.5 minute leg to the holding fix as Published
- Holding Fix This can be a VOR, a VORDME, an Intersection or an NDB
- Outbound Turn A standard rate, 180 degrees turn which is begun at the holding Fix. Also called the “Fix End”
- Abeam The position opposite the holding fix, where the outbound Begins.
- Outbound Leg This leg is defined by the
inbound leg, pilots should adjust the outbound leg so that the inbound
turn, the other standard 180 degrees turn is
completed just as the holding course is intercepted.
- Holding Side The side of the course where the hold is accomplished.
- Non Holding Side The side of the course where you do not want the pilot to be Holding
Back
to Top
6.3.6. Non Standard Holding Pattern [C]
A non-standard holding pattern is one in which
(a) The fix end and outbound end turns are to the left; and/or
(b) The planned time along the inbound track is other than the standard
one-minute or one-and-a-half minute leg appropriate for the altitude
flown.
Back
to Top
6.3.7. Entry Holding Procedure [C]
The entry to a
hold is often the hardest part for a novice pilot to grasp, and
determining and executing the proper entry while simultaneously
controlling the aircraft, navigating and communicating with ATC
requires practice.
There are three standard types of entries: direct, parallel, and teardrop
A
direct entry is exactly what it sounds like the aircraft flies directly
to the holding fix, and immediately begins the first turn outbound.
In
a parallel entry, the aircraft flies to the holding fix, parallels the
inbound course for one minute outbound, and then turns back, flies
directly to the fix, and proceeds in the hold from there.
In a teardrop
(or offset) entry, the aircraft flies to the holding fix, turns into
the protected area, flies for one minute, and then turns back inbound,
proceeds to the fix and continues from there
The pilot is
expected to enter a holding pattern according to the aircraft’s
heading in relation to the three sectors shown bellow, recognizing a
zone of flexibility of five degrees on either side of the sector
boundaries. For holding on VOR intersections, entries are limited to
the radials or DME arcs forming the fix as appropriate.
When
crossing the fix to enter a holding pattern, the appropriate ATC unit
shall be advised. ATC may also request that the pilot report
“established in the hold”. The pilot is to report
“established” when crossing the fix after having completed
the entry procedure
Back
to Top
6.3.8. DME Holdings [C]
DME
holding is subject to the same entry and holding procedures previously
described except that distances, in NM are used in lieu of time values.
In describing the direction from the fix on which to hold and the
limits of a DME holding pattern, an ATC clearance will specify the DME
distance from the navigation aid at which the inbound and outbound legs
are to be terminated. The end of each leg is determined by the DME
indications.
For example:
An aircraft cleared to the 270˚ RADIAL 10 mile DME FIX, to HOLD BETWEEN
10 AND 15 miles, will hold inbound on the 270˚ radial, commence turn to
the outbound leg when the DME indicates 10 NM and commence turn to
inbound leg when the DME indicates 15 NM.
Back
to Top
6.3.9. Published en-Route and Terminal Chart Hold Patterns [C+]
At most high
traffic density areas, holding patterns are depicted on IFR terminal
area and en-route charts. When pilots are cleared to hold at a fix
where a holding pattern is published, or if clearance beyond the fix
has not yet been received, pilots are to hold according to the depicted
pattern using normal entry procedures and timing in the hold ATC will
use the following phraseology when clearing an aircraft holding at a
fix that has a published holding pattern;
Exair123 cleared to (fix), hold (direction) as published expect further clearance at (time)
Note: If you at any time need to slow an aircraft down due to
congestion and either are unsure if the pilot understands how to enter
and maintain a hold or if the aircraft is no where near a published
primary or secondary hold position.
Then you can order the aircraft to make a 360-degree left or right turn, or an “Orbit”.
Back
to Top
6.3.10. Estimated Approach Time (EAT) [C]
Note above the
“Expect Further Clearance” this has the same meaning as EAT
or “Estimated Approach Time. This is the time in UTC when an
aircraft is expected to leave the Initial approach fix, usually the
holding fix. In case off lost communications, an aircraft is expected
to leave the holding at this time.
ATC should always include the EAT to the pilot in order for the pilot
to compute his revised arrival time and above all to ascertain the
remaining flight time endurance (Fuel onboard)
Exair123 "cleared to (fix), hold (direction), as published, EAT (time)"
Or
Exair123 "cleared to (fix), hold (direction), as published, No Delay Expected”
If for what ever reasons the EAT changes then ATC should advise the pilot accordingly
Exair123 "cleared to (fix), hold (direction), as published, Revised Expected Approach Time (time)”
Or
Exair123 "cleared to (fix), hold (direction), as published, Delay Not Determined (reasons)”
Back
to Top
6.3.11. Examples and Recap
Exair123, enter hold at FL100, inbound track 042, left turns, expect further clearance at 25 Zulu.
- The aircraft would fly the Inbound Leg on Radial 222 of the holding Fix.
- The aircraft would be doing Left Hand standard turns
- The aircraft would fly the outbound Leg on an approximate heading of 222
- The aircraft would maintain FL100 in the hold, unless told differently
- The aircraft would maintain the published Speed Restrictions
- The aircraft would continue holding
unless told differently, until the pre advised Zulu time, at which time
the PIC in absence of further clearance may proceed as per Radio
Communication Failure.
Exair123, enter hold at FL80, inbound track 328, right turns, expect further clearance at 05 Zulu.
- The aircraft would fly the Inbound Leg on Radial 148 of the Fix
- The aircraft would be doing Right Hand standard turns
- The aircraft would fly the outbound Leg on an approximate heading of 148
- The aircraft would maintain FL80 in the hold, unless told differently
- The aircraft would maintain the published Speed Restrictions
- The aircraft would continue holding
unless told differently, until the pre advised Zulu time, at which time
the PIC in absence of further clearance may proceed as per Radio
Communication Failure.
Exair123 hold at QDM 115 RK ndb, right hand turns, further clearance at 15 Zulu
- The aircraft would fly towards RK ndb on Track 115
- The aircraft would be doing Right Hand standard turns over RK.
Exair123 cleared to the 130 RADIAL 5 mile DME SPL, to HOLD BETWEEN 5 AND 10 miles.
- The aircraft will hold inbound on the SPL (Schiphol, EHAM) 130˚ radial.
- The aircraft will commence the turn to
the outbound leg when the DME indicates 5 NM and commence the turn to
inbound leg when the DME indicates 10NM.
| 
