Study Guide: Approach

General

TMA controller includes approach and departure control services associated with a particular airport have the following main tasks:

1. maintain an orderly flow of traffic
2. provide separation service between aircraft
3. provide assistance to pilots
   

---

General radar procedures

Identifikation mit Hilfe eines Transponders

Ein Transponder ist ein Bauteil von den gängigen Verkehrs- und Sportflugzeugen, es dient zur Übermittlung von Daten an die Flugverkehrskontrollstelle um die Flugsicherung zu vereinfachen. Mit Hilfe des Transponders ist es möglich, einem Kontakt auf dem Primärradar ein Callsign und einen Flugplan zu zuordnen. Aus diesem Grund erhält jeder Instrumentenflug und spezielle VFR Verfahren von der Flugverkehrskontrollstelle einen Transpondercode zugewiesen.

Mode A

Flugzeuge mit Transpondermode A senden nur den zugewiesenen Transpondercode.

Mode C

Flugzeuge mit Transpondermode C sind in der Lage neben dem Transpondercode auch die aktuelle Flughöhe, gemessen vom barometrischen Höhenmesser. Die übermittelte Höhe ist unabhängig vom eingestellten QNH, die Übermittlung erfolgt in 100-Fuß-Schritten.

Mode S

Transpondermode S übermittelt neben dem Squawk und der Flughöhe zusätzlich das Callsign des Flugzeugs.

---

Position informations

Positionsinformationen dienen zur Orientierung des Piloten und können nach Möglichkeit an Hand von Navaids oder markanten Punkten, ähnlich den Pflichtmeldepunkten an den Piloten übermittelt werden. Die Positionsinformation unter Angabe markanter Punkte soll nur reaktiv angeboten werden, nicht jeder Pilot unter IFR ist mit den Örtlichkeiten vertraut, es empfiehlt sich daher grundsätzlich veröffentlichte Navaids oder einfache Kursangaben und Entfernung für die Übermittlung solcher Informationen zu nutzen.

---

Vectoring of Aircrafts

Flugzeuge kann man mit Hilfe von Kursanweisungen in die gewünschte Flugrichtung führen. Es ist dabei zu beachten, dass eine Kursanweisungen zu einem gewünschten Punkt in Abhängigkeit von Wind, Geschwindigkeit und Bank-Angle nicht immer 100%ig zum gewünschten Ergebnis führen kann, darum ist es wichtig, ein gewisses Gefühl für die Piloten und Flugzeuge zu entwickeln. Übrigens, bei einem Bank Angle von 30° und identischer Geschwindigkeit, ist der Kurvenradius eines Airbus A380 genau so groß, wie der einer Cessna Citation, obwohl diese viel kleiner ist. Grundsätzlich empfiehlt sich, Kursanweisungen möglichst großzügig und rechtzeitig zu erteilen und ein Flugzeug lieber bei 12 dme until touchdown auf dem LOC aufzufädeln, als auf 8 dme.

---

Usage of directs

Piloten unter RNAV und Non-RNAV sind neben dem befolgen von Kursanweisungen auch in der Lage, ihr Flugzeug direkt zu einem gewünschten Wegpunkt zu navigieren und anschließend auf der ursprünglich geplanten Route weiterzufliegen. Die Anweisung zum fliegen eines directs ist für den Piloten nicht verbindlich, er darf dies jederzeit ohne Angabe von Gründen ablehnen. In Absprache mit benachbarten Flugverkehrskontrollstellen ist es auch möglich, directs über große Entfernungen und durch mehrere Flugsicherungssektoren anzubieten. Bei der Freigabe für den Direktflug zu einem Wegpunkt ist zu prüfen, ob der Pilot davon überhaupt einen Nutzen hat, ein Shortcut welcher den Flugweg des Flugzeugs lediglich um 2 Meilen verkürzt ist kein direct und keine Hilfe für den Piloten. Bei der Vergabe von Shortcuts besteht die Gefahr, dass man sich selbst sehr schnell den Luftraum zusperrt, besonders auf Flughäfen wie Innsbruck ist es riskant allen Flugzeugen den Direktflug zum IAF (RTT bzw. KTI NDB) zu erteilen. Ein Direct zu einen Punkt auf einer Transition ist übrigens die gleichzeitige Freigabe für die gesamte darauffolgende Wegstrecke der Transition, allerdings nicht des vertikalen Profils, gleiches gilt für einen Direct zu einem Punkt der STAR, so ist der Pilot freigegeben für die gesamte STAR bis zum IAF, nicht mehr nur bis zum clearance limit.

---

Separation

Vertical separation

Vertical separation is obtained by requiring aircraft using prescribed altimeter setting procedures to operate at different levels to avoid lost of separation. The vertical separation minimum shall be 1000 feet below FL 410 in RVSM airspace or 2000 feet above FL290 in non-RVSM airspaces. To fly within RVSM an aircraft must be equipped with:

1. 2 independent altimeters
2. an autopilot witch must be able to hold an specific altitude
3. min. Mode C transponder

---

Lateral separation

Lateral separation is also known as radar separation and shall be applied so that the distance between those portions of the intended routes for with the aircraft are to be laterally separated is never less than an established distance to account for navigational inaccuracies. Have a look into the wake turbulance separation to find the required distances for the lateral separation.

---

Wake turbulence separation

Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wingtip vortices and jetwash. Jetwash refers simply to the rapidly moving gases expelled from a jet engine; it is extremely turbulent, but of short duration. Wingtip vortices, on the other hand, are much more stable and can remain in the air for up to three minutes after the passage of an aircraft.

Takeoff

An aircraft of a lower wake vortex category must not be allowed to take off less than two minutes behind an aircraft of a higher wake vortex category. If the following aircraft does not start its take off roll from the same point as the preceding aircraft, this is increased to three minutes.

Landing

Preceding aircraft	Following aircraft	Minimum radar separation
Super	Super	4 NM
	Heavy	6 NM
	Large	7 NM
	Small	8 NM
Heavy	Heavy	4 NM
	Large	5 NM
	Small	5 NM
Large	Small	4 NM

Staying on or above leader's glide path

Incident data shows that the greatest potential for a wake vortex incident occurs when a light aircraft is turning from base to final behind a heavy aircraft flying a straight-in approach. Light aircraft pilots must use extreme caution and intercept their final approach path above or well behind the heavier aircraft's path. When a visual approach following a preceding aircraft is issued and accepted, the pilot is required to establish a safe landing interval behind the aircraft he was instructed to follow. The pilot is responsible for wake turbulence separation. Pilots must not decrease the separation that existed when the visual approach was issued unless they can remain on or above the flight path of the preceding aircraft.

---

the role of Approach Controllers

TMA Controllers (S3) includes approach and departure control services associated with a particular airport.

• maintain an orderly flow of traffic
  
• provide a separation service between aircraft
  
• provide assistance to pilots
  

The greatest difference when you are starting you TMA-carreer will be the separation between approaching and departing traffic.
There are some separation in your airspace:

• Vertical separation: should be at least RVSM 1000ft, Non-RVSM 2000ft. Austria uses RVSM (Reduced Vertical Seperation Minima). So you can use 1000ft up to FL410.
  
• Horizonal separation: The Minimum Horizontal Seperation depends on the radar equipment involved. APP Sectors work with a minimum of 3 nm, CTR Sectors use 5 nm.
  

How to maintain visual separation?
You may use:

• Lateral vectoring When issuing a heading to an aircraft, make sure that you are using a direction ending on 0 (zero) or on 5 (five).
• Vertical vectoring: climbing or descending. For departing or arriving traffic you also can use a "stop climbing/descending at FLxxx" to avoid a conflict.
  
• Speed limit: A controller may issue speed instructions within an aircrafts operating limits. There are two possible ways to do this, either by using Indicated Airspeed (FL280 or below) or by specifying a Mach number (FL280 or above). Take notice of the minimum speed of the aircraft! Normally you are working with "minimum clean" (means the lowest speed an aircraft can maintain without using flaps or spoilers) above FL100. The second is “minimum approach speed” which is the lowest speed an aircraft can maintain using both flaps and spoilers.
  

Phraseology

A ...Pilot
G...ATC

Approach

Standard clearances for arriving aircraft shall contain the following items, if applicable:

1. Aircraft identification
2. Designator of assigned STAR
3. Runway-in-use, except when part of the STAR description
4. Initial level, except when this element is included in the START description and
5. Any other necessary instructions or information not contained in the START description, e.g. change of communication

Type of approach procedure

G: CLEARED / PROCEED VIA (designator) ARRIVAL
G: CLEARED TO (clearance limit) VIA (designator) ARRIVAL
G: CLEARED (type of approach) APPROACH RUNWAY (number)
G: CLEARED LOCALIZER APPROACH [RUNWAY (number)] [GLIDE PATH INOPERATIVE]
G: CLEARED APPROACH RUNWAY (number)
A: REQUEST (type of approach) APPROACH [RUNWAY (number)]
G: (type of approach) NOT AVAILABLE DUE (reason) [alternative instructions]
A: REQUEST (RNAV plain language designator)
G: CLEARED (RNAV plain language designator)
G: ARE YOU FAMILIAR WITH (name) APPROACH PROCEDURE [RUNWAY (number)]?

Straight-in approach

A: REQUEST STRAIGHT-IN / DIRECT [type of approach] APPROACH [RUNWAY (number)]
G: CLEARED STRAIGHT-IN / DIRECT [type of approach] APPROACH [RUNWAY (number)]

Approach instructions with radar

G: VECTORING FOR (tpye of pilot interpreted aid) APPROACH RUNWAY (number)
G: VETORING FOR VISUAL APPROACH RUNWAY (number), REPORT FIELD / RUNWAY IN SIGHT
G: VECTORING FOR (positioning in the circuit)
G: VECTORING FOR SURVEILLANCE RADAR APPROACH RUNWAY (number)
G: VECTORING FOR PRECISION APPROACH RUNWAY (number)
G: (type) APPROACH NOT AVAILABLE DUE (reason) (alternative instructions)
G: POSITION (number) MILES FROM (position) / TOUCH DOWN. TURN LEFT / RIGHT HEADING (three digits)
G: YOU WILL INTERCEPT (radio aid or track) (distance) FROM (significant point) / TOUCH DOWN
A: REQUEST (distance) FINAL
G: CLEARED FOR (type) APPROCH RUNWAY (number)
G: REPORT ESABLISHED [ON ILS / LOCALIZER / GLIDE PATH]
G: REPORT ESTABLISHED ON FINAL APPROACH TRACK
G: CLOSING FROM LEFT / RIGHT [REPORT ESTABLISHED]
G: TURN LEFT / RIGHT HEADING (three digits) [TO INTERCEPT [RIGHT TO LEFT / LEFT TO RIGHT / REPORT ESTABLISHED]
G: EXPECT VECTORS ACROSS (localizer or radio aid) (reason)
G: THIS TURN WILL TAKE YOU THROUGH (localizer or radio aid) [reason]
G: TAKING YOU THROUGH (localizer or radio aid) [reason]
G: MAINTAIN (altitude) UNTIL GLIDE PATH INTERCEPTION
G: REPORT ESTABLISHED ON GLIDE PATH
G: INTERCEPT (localizer or radio aid) [REPORT ESTABLISHED]
G: INTERCEPT (radio aid) [LEFT TO RIGHT / RIGHT TO LEFT]
G: CLEARED FOR ILS APPROACH RUNWAY (number) LEFT / RIGHT
G: YOU HAVE CROSSED THE LOCALIZER. TURN LEFT / RIGHT IMMEDIATELY AND RETURN TO THE LOCALIZER
G: ILS RUNWAY (number) LEFT / RIGHT LOCALIZER FREQUENCY IS (number)
G: TURN LEFT / RIGHT (number) DEGREES / HEADING (three digits) IMMEDIATELY TO AVOID TRAFFIC [DEVIATING FROM ADJACENT APPROACH], CLIMB TO (level)
G: CLIMB TO (level) IMMEDIATELY TO AVOID TRAFFIC [DEVIATING FROM ADJACENT APPORACH] (further instructions)

Go around

G: GO AROUND IMMEDIATELY (missed approach instruction) (reason)
G: IF GOING AROUND (appropriate instructions)
G: ARE YOU GOING AROUND?
A: GOING AROUND

Level changes, reports and rates

G: CLIMB / DESCEND
- TO (level)
- TO AND MAINTAIN BLOCK (level) TO (level)
- TO REACH (level) AT / BY (time or significant point)
- REPORT LEAVING / REACHING / PASSING (level)
- AT (number) FEET PER MINUTE [OR GREATER / LESS]
G: REQUEST LEVEL / FLIGHT LEVEL / ALTITUDE CHANGE FROM (name of level) [AT (time or significant point)]
G: STOP CLIMB / DESCENT AT (level)
G: CONTINUE CLIMB / DESCENT TO (level)
G: EXPEDITE CLIMB / DESCEND [UNTIL PASSING (level)]
G: RESUME NORMAL RATE OF CLIMB / DESCENT
G: REPORT LEAVING / REACHING / PASSING (level)
G: WHEN READY CLIMB / DESCENT TO (level)
G: EXPEDITE CLIMB / DESCENT AT (time of significant point)
G: EXPEDITE CLIMB / DESCENT UNTIL PASSING (level)
A: REQUEST DESCENT AT (time)
A: REQUEST ALTITUDE (number FEET) / FLIGHT LEVEL (number) VIA (route) [DUE TO (reason)]
A: REQUEST LEVEL CHANGE / CLIMB / DESCENT AT (time / position)
G: EXPECT LEVEL CHANGE / CLIMB / DESCENT
- FROM (name of unit)
- AT (time or position)
- AFTER PASSING (position)
- IN (number) MINUTES
G: IMMEDIATELY
G: AFTER PASSING (significant point)
G: AT (time or significant point)
G: WHEN READY (instructions)

Vectoring

G. LEAVE (significant point) HEADING (three digits) [INBOUND [AT (time)]
G: CONTINUE HEADING (three digits)
G: CONTINUE PRESENT HEADING
G: FLY HEADING (three digits)
G: TURN LEFT / RIGHT HEADING (three digits) [reason]
G: TURN LEFT / RIGHT (number) DEGREES [reason]
G: STOP TURN HEADING (three digits)
G: FLY HEADING (three digits), WHEN ABLE PROCEED DIRECT (name) (significant point)
G: HEADING IS GOOD
G: WHEN ABLE PROCEED DIRECT (position)
G: SUGGEST (suggestion)
G: IF UNABLE [(alternative instructions)] ADVISE
A: UNABLE TO COMPLY (reason)
G: VECTORING FOR SPACING / SEPERATION / DELAY
G: VECTORING DUE TO TRAFFIC
G: RESUME OWN NAVIGATION (position of a/c) (specific instructions)
G: RESUME OWN NAVIGATION [DIRECT] (significant point) [MAGNETIC TRACK (three digits) DISTANCE (number) MILES]
G: MAKE A THREE SIXTY TURN LEFT / RIGHT [reason]
G: ORBIT LEFT / RIGHT [reason]
G: MAKE ALL TURNS RATE ONE / RATE HALF (number) DEGREES PER SECOND START AND STOP ALL TURNS ON THE COMMAND “NOW”
G: ALL TURNS RATE ONE / RATE HALF (number) DEGREES PER SECOND, EXECUTE ISNTRUCTIONS IMMEDIATELY UPON RECEIPT
G: TURN LEFT / RIGHT NOW
G: STOP TURN NOW

Speed instructions:

G: REPORT SPEED
G: REPORT INDICATED AIRSPEED / TRUE AIRSPEED / MACH NUMBER
A: SPEED (number) KNOTS / MACH (number)
G: MAINTAIN (number) KNOTS / MACH (number) [OR GREATER / LESS] [UNTIL (significant point)]
G: DO NOT EXCEED (number) KNOTS / MACH (number)
G: MAINTAIN PRESENT SPEED
G: INCREASE / REDUCE SPEED (number) KNOTS / MACH (number) [OR GREATER / LESS]
G: INCREASE / REDUCE SPEED BY (number) KNOTS / MACH (number) [OR GREATER / LESS]
A: UNABLE TO COMPLY, INDICATED AIRSPEED WILL BE (number) KNOTS / MACH (number)
G: RESUME NORMAL SPEED
G: REDUCE TO MINIMUM APPROACH SPEED
G: REDUCE TO MINIMUM CLEAN SPEED
G: REDUCE TO MINUMUM SPEED
A: MINUMUM SPEED / MINIMUM CLEAN SPEED / MINIMUM APPROACH SPEED IS (number) KNOTS
G: NO [ATC] SPEED RESTRICTIONS

Flight rules

A: CANCELLING IFR
G: IFR CANCELLED AT (time)

A: REQUEST IFR CLEARANCE
G: CLEARED TO (clearance limit), VIA (route) (level) (other instructions), IFR [FLIGHT] STARTS AT (position or time) / WHEN REACHING (level) / PASSING (level) / NOW [(instructions)]

G: CLEARED NIGHT VFR
G: CLEARED SPECIAL VFR

FAQs

How do I work with STARs and Transitions?
STAR means Standard Terminal Arrival Route is like a route to the airport.This road has a name that has three parts. The first part is the navigational point where the route starts, the second is the version number, and the third is usually but again not always coupled to a certain runway(s). Transitions are connecting between the end of STAR to the final but not at any airport.
Using STARs and Transition simplifies the arrival considerably for both pilots and controllers. By clearing "transition and profile" the pilot has also the clearance for descending as published. So you can expect the track, descend and speed of an aircraft as published.

How to use a Holding?
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.
A holding is situated around a holding fix. In a standard holding pattern the aircraft flies inbound to the holding fix on a certain course (Inbound leg). After passing the fix it turns right (standard turn: 2° per second) and flies one minute (1,5 min above FL 140) into the other direction (outbound leg). After one minute the pilot turns right again (standard turn) and establishes again on the inbound leg.
If you count all this together you end up with four minutes required to finish one holding pattern. However some holding patterns use left turns, others don't use one minute to measure the outbound leg, but fly to a certain distance.
Also every holding has a minimum altitude.

What does MRVA mean?
Minimum Radar Vectoring Altitude: lowest altitude above MSL that can be used for IFR vectoring

When is the best moment for my handoff?
Out of conflict and as early as possible.

Which classes of airspace are provided in Austria?

• C (Charlie) controlled airspace, IFR and VFR possible, aircontroll is mandatory. IFR will be separated to other IFR and VFR traffic, VFR traffic receive traffic information about other VFR traffic. C starts AT FL195 and inside Special Rules Area (e.g. SRA Wien)
  
• D (Delta) controlled airspace, IFR and VFR possible, aircontroll is mandatory. IFR is separated to other IFR and receives traffic information about other VFR; VFR traffic reveives information about other traffic. D in Austria covers space between FL125 and FL195 (CTA) and inside contolled zones and certain SRA.
• E (Echo) controlled airspace only for IFR; VFR receives information as far as possible. In Austria up to FL125 in inside of certain TCAs (Terminal Control Areas).
• G (Golf) uncontrolled airspace. Traffic information as far as possible.
  
  

What are Y and Z-flights?
Basically these are flights with a change between IFR/VFR

• Y starts with IFR, changing to VFR (IFR cancellation)

• Z starts with VFR, changing to IFR (IFR pickup)

References

Information about airspaces and airways can be found here: [1]

Details about air pressure and altitudes you will find here: [2]

Links for the reference (working) sheets you find at the airport details.

Local Procedures

LOWW

Frequencies:

LOWW_APP can be divided into up to six Sectors:

LOWW_APP	LOWW_N_APP	LOWW_S_APP	LOWW_F_APP	LOWW_D_APP	LOWW_DEP
128.200	124.550	129.550	119.800	132.470	118.770
GND-FL105	FL105-FL245	FL105-FL245	1st Director	2nd Director	Departure

The decision which sectors are used shall be based on traffic Situation.

Transition Altitude: 5000ft

Limits

- vertikal: GND - FL245 - lateral: see appendix and shown by sectorfile

Arrivals

• LOVV_CTR should clear traffic for LOWW STAR. Hand-off 2 minutes before listed waypoints below:

VIA	FL
MASUR	at FL170
BARUG	at FL170
NIGSI	at FL180

• LHCC: approaching traffic is maintaining FL140 over GIGOR

• LZBB: arriving traffic via TOKVA has to maintain FL160 and via REKLU FL180

• LKAA: FL 130 via MIKOV/LEDVA and FL170 via LANUX FL170

Departures

• via UMBIL, OSPEN, SITNI, LUGIM and MOTIX cleared to FL200.

Those flights are released to LOVV_CTR for further climb within the Release Area South and Release Area West (see Appendix)

• via LANUX, KOVEL, MIKOV, LEDVA cleared FL240 to LKAA_CTR.

• via SASAL, STEIN cleared FL230 to LHCC_CTR

• via ABLOM cleared FL150 (ABLOM FL130 or above) to LZBB_CTR.

• LOWW to LOWL: maximum FL160 (hand-off to LOWL_APP)

• LOWW to LOWG: maximum FL160 (hand-off to LOWG_APP)

• LOWW to LOWS / LOWK / LOWI: if requested FL is above FL160, traffic shall be transferred to LOVV_CTR.

Inbound / Outbound LZIB (Bratislava) and LKTB (Brno)

• Inbounds LKTB and LZIB shall be cleared from LOVV_CTR to FL210 and hand-off short before Approach Area Wien.

• Outbounds LKTB and LZIB shall be cleared to FL240 and hand-off to LOVV_CTR.

inbound LZIB	FL070 (KUNET at level)
outbound LZIB	climbing FL120
inbound LKTB	FL110 (MIKOV at level)
outbound LKTB	climbing FL100
LOWW to LZIB	FL070 (ABLOM at level)
LZIB to LOWW	6000ft (TOVKA at level)

Remarks

• Coordination regarding procedures not listed in this document shall be done in due time with the respective and responsible ATC unit.

• LOWW_APP may send departing traffic to the last waypoint of the SID without coordination.

• Hand-off for arrivals to LZIB short before MIRLU.

Appendix

 

reference sheet you find downloads.vacc-austria.org/Documents/QRS_LOWW_v1.3.pdf

LOWI

Frequencies: 119.27

Transition Altitude: 11000ft

Limits

- vertikal: GND - FL165

Arrivals

• LOC/DME West via KTI FL130 over KTI

• LOC//DME East via RTT 9500ft over RTT

• RNP – RNAV Approach Runway 26: instrumental approach with lower minimas, final also a visual approach. Only on pilot request; different miss-appproach-procedure

• All arrivals are going via AB, finals after AB are always visual

The reference sheet you find: downloads.vacc-austria.org/Documents/QRS_LOWI_v1.2.pdf

LOWG

Frequencies: 119.3

Transition Altitude: 4000ft

Limits

- vertikal: GND - FL165

Arrivals There are no STARs in LOWG. Most of the arrival routes ends at GRZ-VOR. After GRAZ normally vectors are used.

• ILS 35C starts at 3300ft. Best way is to intercept at LENIZ at 3500ft.

• VOR-DME 35C: Approach über GRZ-VOR nach DME 7.0 GRZ (heading 147°), danach vector auf final track

• VOR-DME 17C: Approach über GRZ-VOR, starts at D15. GRZ 7000ft, descend profile see chart.

hand/over

• LHCC_CTR via GOTAR FL150

• LJLA_CTR via RADLY FL160

• LOVV_CTR FL160

LOWK

Frequencies: 126.825

Transition Altitude: 7000ft

Limits

- vertikal: GND - FL165

Arrivals

• ILS 28

• NDB-DME 28

• NDB-DME 10

• Circling 10: Anflug über ILS28, desc. 3000ft, circeling starts at KI

hand/over

• LJLA_CTR via REKTI FL160

• LOVV_CTR FL160

LOWS

Frequencies: 123.720
Transition Altitude: 4000ft

Limits

- vertikal: GND - FL125

Arrivals

ILS 16
NDB 16 
visual 34

hand/over

EDDM_S_APP via NAPSA and TRAUN
EDDM_CTR via TRAUN
rest to LOVV_CTR, all FL120

reference sheet you find at downloads.vacc-austria.org/Documents/QRS_LOWS_v1.1.pdf

LOWL

Frequencies: 129.620
Transition Altitude: 4000ft

Limits

- vertikal: GND - FL165

Arrivals

ILS/VOR 08 (ILS 08 not in standard FSX) 
ILS/NDB 26
(former RWYs known as 09 and 27)

hand/over

EDDM_CTR via PABSA and TRAUN
LKAA_CTR via ADLET
rest to LOVV_CTR, all FL160

reference sheet you find at downloads.vacc-austria.org/Documents/QRS_LOWL_v1.0.pdf

==References== 

http://en.wikipedia.org/wiki/Wake_turbulence