Carrier Air Operations

A home away from home for many naval aviators

Carrier Air Operations are the various procedures and techniques that make up landing on a moving ship, usually several miles away from any solid ground on which you can land instead. Both fixed-wing and rotary wing aircraft can make use of aircraft carriers to land on, as well as STOL / STOVL aircraft such as the Harrier and the F-35B. Because of the relatively small size (compared to a fully fledged land-based airport) of the carrier, strict procedures and rules are employed to avoid accidents (such as airplanes crashing into one another).

Carrier Basics

Before we dive headfirst into the procedures and rules associated with carrier air operations, we will first go over the various basics that come into play when operating on a carrier. These include items such as how does a carrier work, what does a carrier look like, and what sort of key features should you pay attention to when you cannot make out left from right when operating on a busy carrier.

Carrier Features

Because of the limited length of an aircraft carrier some special equipment is used for launching (departure, taking off) and recovering (landing) aircraft. Whereas normally a runway would net you somewhere in the ballpark of 6000 - 12000 feet of usable space, having a total length of 1100 feet is already quite spacious for an aircraft carrier. There are various types of key equipment used on a carrier:

1. Arresting gear

Used to slow down / landing aircraft (recoveries)

2. Catapults

Used to speed up / launch aircraft

3. Launch ramp

Used to launch aircraft

4. IFLOLS

Used to guide aircraft into landing (recoveries)

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Ski ramps (STOBAR)

Su-33 taking on from ski carrier ramp

Most modern aircraft tend to be quite heavy (due to radar / sensor electronics, as well as heavy jet engines) and as such they cannot simply run off the edge of the ship at full speed to get into the air (though this was common practice for the lighter World War 2 aircraft). Instead modern carrier aircraft need a lot of lift to become airborne.

The method preferred by some (Soviet / Russian) aircraft designers is to use the carrier ramp and a high thrust to weight ratio: i.e. the plane is capable of putting out a lot of power compared to its weight (the plane has a large acceleration and power output). These aircraft may also have a large wingspan, which combined with the higher power output allows it to obtain a lot of lift upon accelerating. This allows these planes to launch via 'ski ramp', by simply running off this ramp at full power: the ramp increases both the altitude and angle of attack (which improves lift) to launch the aircraft.

Ski ramp on a Russian carrier

The procedure of using a ramp to launch aircraft is called STOBAR ( Short Take-Off But Arrested Recovery ) and is a simple (cost effective) manner of launching aircraft from a carrier.

Launching via STOBAR is done by lining the aicraft up on the designated positions (painted onto the aircraft deck): removable wheel chocks are located in these positions and come up out of the deck to hold the aircraft in place (via its wheels). Simultaneously the Jet Blast Deflector (JBD) is raised behind the aircraft: the JBD is used to prevent the exhaust from the airplane preparing to take-off from blowing away other aircraft lined up behind it.

The aircraft taking off can then select (maximum) afterburning mode to build up the power, as jet engines take a second or so to spool up to full power (i.e. they do not deliver instantaneous throttle-power response, instead there is some power lag). On some (Russian) aircraft an override (carrier takeoff) switch can be set to provide even more engine power (at the trade-off of more engine wear and tear), to be used when an aircraft is heavily loaded or in bad weather conditions.

This is also the large drawback of using the ramp system: overall aircraft weight is reduced. This typically means that the aircraft is able to bring less ordinance (weapons) and fuel, or that the systems are less capable to keep the aircraft weight down. Fuel reduction may not be a primary concern, as carrier aircraft tend to proceed directly to a tanker to fill up on fuel after launch, but the reduction in ordinance (weapon loadout) may be more pressing.

The aircraft carrier ramp also nets you less total space on the carrier that can be used to park aircraft (as you cannot park aircraft on the ramp due to the slope and blocking of the only takeoff option), as well as being able to launch aircraft at slower intervals compared to using catapults (as you can launch multiple aircraft from different catapults at nearly the same time).

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Catapults (CATOBAR)

F-18C taking off using the catapult

Rather than implement the CATOBAR ramp system, the United States (whom pioneered the system) and most NATO countries instead use the CATOBAR (Catapult Assisted Take-Off But Arrested Recovery system. The aircraft catapult is a launcher to which an aircraft is hooked up, which is then launched using external power from the carrier (either steam or electromagnetic power).

Up to the Cold War most aircraft used a length of reinforced rope (called a bridle) to attach to the catapult shuttle, but in all aircraft after the Cold War the shuttle instead connects to the nose gear of the aircraft via the launch bar. The pilot can selectively lower the launch bar with a switch in the cockpit to hook up to the catapult (shuttle). This shuttle also holds back the aircraft, so that the engines can be run up to full (afterburning) mode before launching. The catapult is then set to the appropriate amount of power and the aircraft can be subsequently launched.

Although more expensive (maintenance costs) to operate than the comparative ramp system, the catapult system allows you more flexibility in operating it: you can increase the amount of power on the catapult for heavier aircraft (more fuel/ordinance), as well as being able to hookup and launch multiple aircraft in quick succession by using multiple catapults.

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Arresting gear

F-18C landing with arrestor wires

To allow aircraft to land in a much smaller space, a number of wires (typically 4 or 5) are strung across the landing deck. The aircraft catches one of these arresting wires with the use of the hook built into the airframe, after which the aircraft slows down rapidly (though quite harshly). Obviously aircraft such as helicopters and STOL/STOVL (such as the Harrier or F-35) do not need these arresting wires, as they can simply land (semi) vertically.

Because of the limited length of the landing area and the harsh landing, the aircraft used for landing on a carrier (carrier aircraft) also have very robust landing gear to withstand the high rate of descend. In a way, landing on an aircraft carrier is more controlled crashing than actual landing.

To allow aircraft carriers to launch and recover aircraft at the same time, the landing deck often has an offset: this means the landing deck is at an angle compared to the rest of the ship (typically at 9 degrees). Typically you will visually adjust for this offset (respective of the carrier course) in your landing procedure, but during nighttime or bad visibility you will be given a different heading to adjust for this offset automatically.

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IFLOLS

IFLOLS

The IFLOLS (Improved Fresnel Optical Landing System) is a system used on carriers to guide aircraft into the correct landing approach ('line-up'). Aside from extreme weather conditions or nighttime (both leading to limited visibility) landings, you will use this system to correctly line yourself up so that you may make a successful landing first time round.

The LSO (Landing Signal Officer) are in charge of operating these lights and will guide you on landing the aircraft, as well as grading the landing attempt afterwards. Please see the appropriate chapter for further information.

[Expand] IFLOLS
#	Name	Function
1	Ladder / Meatball	On this vertical bar with yellow/red lights, the orange ball ('meatball') will move up and down according to aircraft position. If the ball is too low, your aircraft is too low. If the ball is too high, your aircraft is too high. The goal is to line it up with the datum lights (2) for optimal landing: should the orange ball fall into red lights you are dangerously low and you will need to wave off (stop) the landing attempt.
2	Datum lights	These green horizontal bar of lights indicates your ideal line up: the goal is to have the orange ball ('meatball') line up with the datum lights for ideal vertical landing position.
3	Cut lights	On early approach the cut lights illuminate 2 ~ 3 seconds to indicate 'proceed with landing'. Any subsequent illumination means 'add power', according to length of illumination of lights
4	Wave off lights	Should the landing fall outside safe parameters (for example you are way too low), the LSO will call 'Wave Off!' and these lights will illuminate: you need to terminate the landing attempt and go around (climb away).
5	Emergency wave off lights	Identical in function to normal Wave Off Lights (4): for really dense pilots.

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Carrier Deck Layout

Let's first familiarize ourselves with the overall carrier deck layout (topology). Unlike an airfield, where there is space aplenty, the carrier is quite cramped and often busy with other aircraft, so knowing where you are going (and not hindering others) is vital.

All (modern) aircraft carriers more or less have the same layout: the figure here shows the diagram of the USS Nimitz class carriers, but we could still apply the location names to all other carriers (including carriers such as the Russian Admiral Kuznetsov).

Objects such as parked aircraft or munition carts can be placed on the aircraft deck (by the mission developer): even if they are not moving ('static') they can till be collideable. So ensure your path and catapult are clear before moving, before finding out on take-off that there is an aircraft parked on the catapult.

The most critical locations on an aircraft carrier are the catapults or ramp (marked in green and numbered), and the landing deck (between the red stripes, with yellow centerline). These are for respectively launching aircraft (taking off) and recovering aircraft (landing), so like a runway, do not block them. Typical recovery or departure intervals are approximately 20 to 30 seconds, so try to cross them quick if you have to and be wary of other aircraft.

[Expand] | Carrier Topology List |
#	Name	Location	Colour	Function	Notes
1	Landing Deck	Slanted along deck	Between red lines, with yellow centerline	Landing aircraft	Keep clear at all times
2	Catapults	Bow (front)	In green, JBD in light blue	Launching aircraft	Be mindful about parked aircraft obstructing catapults
3	Island	Starboard, midways ship	In purple	Ship control, aircraft control tower	Waive to your Airboss
4	Elevators	Edge of ship	In blue	Transporting aircraft to hangar / deck
5	Crotch	Bow (front)	Black	Do NOT use for landing lineup
6	Box	Between catapults 1 and #2	Black	Shooter / catapult control	Little hut where the catapult controller sits
7	Point	Starboard bow		QRA: Quick Reaction Alert	Parking aircraft for quick reaction air support
8	Corral	Between elevators 1 and #2		Parking
9	Street	Midship / Center		Access to elevators, corral, sixpack
10	Sixpack	Midship / Center		Parking
11	Junkyard	Between island and elevator #3		Parking of AWACS, Tanker, Transport aircraft
12	Patio	Starboard stern		Parking
13	LSO	Port stern		Landing Officer	Bunch of guys grading your landing
14	Finger	Port stern		Parking

Knowing these areas by name is certainly not required, but know to keep the landing deck clear!

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Carrier Cases

During carrier operations we use 1 of 3 possible cases, with cases each having different approaches and procedures: this is to adjust to the weather and visibility conditions. The carrier will normally dictate which case is currently in use, but mainly it is dependant on the minimum visibility ('horizontal sightlines') and ceiling ('vertical visibility') according to the table below:

Case	Conditions	Ceiling	Visibility
1	No instrument conditions during daytime departures/recoveries	> 3000 ft (910 m)	> 5 nm (9.3 km)
2	(Light) Instrument conditions during daytime departures/recoveries	> 1000 ft (300 m)	> 5 nm (9.3 km)
3	Severe instrument conditions during daytime and nighttime recoveries	< 1000 ft (300 m)	< 5 nm (9.3 km)

Please note that recovering during night time automatically defers you to a case 3 landing, regardless of actual weather and visibility conditions.

Altitudes, ranges and distances

The Air Traffic Controller in charge of the flight procedures around the carrier is called the 'Marshall', and he gets to boss you around for not flying perfectly perpendicular to his nice pattern / approach. He will tell you what case the carrier is currently operating in, gives you permission to transition to a given holding stack (altitude) or move closer to the carrier (zone).

Most notably the Marshall should tell you the BRC, or Base Recovery Course. This the current course that the carrier is moving in, and should be the course that you adhere to for landing your aircraft on the carrier deck: please note that the actual carrier landing deck is offset by 9 degrees from the BRC. During Case 3 conditions you will instead be told the FB, or Final Bearing which is the BRC adjusted with the 9 degree offset (FB = BRC - 9).

Below are the altitude blocks and zone distances associated with carrier operations:

Altitude	Zone
6000+ ft	Case 3 Marshall (traffic) stack
3000+ ft	Case 1 holding pattern / stack
1200 ft	Case 3 approach and missed approach
800 ft	Case 1 initial overhead break
600 ft	Case 1 downwind and missed approach
500 ft	Case 1 departure in CCZ
300 ft	Helicopter operations in CCZ

Distance	Altitude	Zone
50 nm DME	Inf.	CCA, Carrier Controlled Area
10 nm DME	Inf.	Marshall Controlled Area
5 nm DME	2500 ft	CCZ, Carrier Controlled Zone

Distances given in DME (Distance Measuring Equipment) are thus identical to distance from the carrier: this distance can be obtained by using the TACAN signal of the carrier or similar equipment (ICLS).

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Carrier Landing

For this chapter we have outline the various carrier cases landing procedures and approaches: for ease of use these are split into the traffic pattern and landing pattern. The traffic pattern is used for approaching to the carrier and holding the in the traffic pattern / stack until you it is your time to land on the carrier (which usually involves waiting for other pilots to land first). The landing pattern goes about explaining the actual steps for the landing approach. Thanks to Kola360 we have also been able to provide you with the relevant communications guide for these cases.

We would like to give a massive 'Thank you' to Jabbers, Kola360 and Redkite for their contributions to making these chapters.

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Case 1 Landing

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  Case 1 Traffic Pattern

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  Case 1 Landing Pattern

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  IFLOLS

The Case 1 landing in good visibility conditions is (and probably should be) the first type of landing you learn for carrier recovery. It follows these 3 stages:

1. Enter traffic pattern

For case 1 you will contact the relevant air controllers (see communications list), which will grant your permission to enter the airspace and direct you to a holding pattern / altitude (a circle of approx. 5 nm at 1000 feet intervals, starting at 2000 feet).

2. Fly landing pattern

When you are cleared by the Marshall for landing, you will use the landing pattern to get to the carrier (on final, or 'in the groove')

3. Line up with IFLOLS

The final stage of Case 1 is the line-up with the IFLOLS on final approach, or 'in the groove'

Instructions for Case 1 communications and approach pattern are in the table below. For this communications example our pilot has (side) number '118' and we have a number of radio frequencies (called 'buttons'): the pilot/side number and radio frequencies will most likely be different in your scenario.

[Expand] Case 1 Communication / Landing Pattern
#	Location	Pilot action	Messages	Frequency
1	17000 ft, 75+ DME Outside of CCA (~ 50 nm)	Ask permission from Red Crown to enter.	Pilot: [Red Crown, 118, Mother's 250 for 75, Angels 17] Red Crown: [118, Sweet/Sweet, contact Strike on Button 3]	Button 4, 256.000 AM
2	12000 ft, 55 DME Inside CCA Outside Marshall Area (10 nm)	Ask permission from Strike to enter.	Pilot: [Strike, 118, flight of 2, Mother's 250 for 55, Angels 12] Pilot: [State 5.4, no Alibis] Strike: [118, Sweet/Sweet, Mother is VFR, Case 1] Strike: [Contact Marshall on Button 2]	Button 3, 265.000 AM
3	9000 ft, 52 DME	Pilot makes call outside 10 nm (but inside CCA). Contact Marshall to enter CCA.	Pilot: [Marshall, 118, 2050 for 52, Angels 9, State 5.3] Marshall: [118, Case 1, BRC is 010, hold at 2000, Charlie Time 22] Marshall: [Altimeter 29.92. Report see me.] Pilot: [118, Wilco]	Button 2, 264.000 AM
4	5000 ft, 10 DME	Pilot has visual on carrier. Cleared to enter stack (2000 ft, stack 1). Monitor button 1 for other traffic.	Pilot: [118, See you at 10] Marshall: [118, Switch Tower on Button 1]	Button 2, 264.000 AM
5	2000 ft, In the Stack	Pilot has obtained Charlie Time from Marshall and must be 'At Ramp' at given time (2200 hours).	Zip Lip, unless [safety concerns]. Monitor Button 1 for traffic	Button 1, 301.000 AM
6	2000 ft, In the Stack	Pilot matches speed so he is 'At Ramp' on Charlie Time	IMC ONLY Pilot: [118, Commencing] Pilot: [118, at Initial]	Button 1, 301.000 AM
7	800 ft	Case 1 Recovery	LSO: [3/4 mile, Call the Ball] Pilot: [118, tomcat/hornet, call/clara, state, auto*] LSO: [Roger Ball]	Button 1, 301.000 AM
Additional case 1 communication
8	2000 ft, In the Stack	Air Boss adds Delta Time to given Charlie Time: 'At Ramp' time becomes Charlie Time + Delta Time	Air Boss: [118, Delta 6]	Button 1, 301.000 AM
9	2000 ft, Commencing	Pilot has to go into spin pattern before heading for the initial break	Air Boss: [118, Spin It] Pilot: [118, Spinning]	Button 1, 301.000 AM
10	600 ft, Abeam carrier	Pilot has extend downwind too far and must return to initial (800 ft starboard of carrier), to redo the case 1 pattern	Air Boss: [118, too long in the groove, (an airbus cut you off), wave off and return to pattern]	Button 1, 301.000 AM

Once you have successfully reached step 7 in the communications example above you should now go into the Case 1 Landing Pattern, as follows in the table below:

[Expand] Case 1 Landing Pattern
#	F-14	F-18
A	800 ft entry, approx. 300 - 350 kts,hook down, wing sweep 68	800 ft entry, approx. 300 - 350 kts,hook down
B	Speedbrake[1], radar altimeter to 370 ft
C	Level break at 1.5 ~ 2.0 nm DME; 15 to 17 seconds between breaks,level turn at 800 ft. Turn should be at 45 ~ 50 degrees of bank or at 10% in G of airspeed (i.e. 330 kts -> 3.3 G).
D	Halfway into turn, set gear down at < 280 ktsand flaps/slats at < 225 kts	Halfway into turn, setgear/flaps/slats at < 250 kts
E	Descend to 600 ft, auto throttle[1]
F	On-speed AOA at 15 units, set DLC	On-speed AOA at 8 units
G	600 ft
H	Prepare to turn once abeam of LSO station, at 1 ~ 1.3 nm abeam DME
I	Commence turn once 'round down' visible, turn at ~ 30 degrees bank
J	Maintain AOA, halfway into turn at 500 ft
K	Enter groove at ~ 350 ft (altimeter!), at 3/4 miles, on-speed and call the ball:side number, tomcat/hornet, ball/clara[2], fuelstate[3], (auto[4])
W	Upon (or prior to) waveoff set full power: return to BRC paralleland intercept pattern at LSO / marshall discretion
Speedbrake / ATC [1]		As desired
Clara [2]		Ball is obscured, LSO will give instructions
Fuelstate [3]		Remaining fuel in thousands of pounds:5100 pounds -> 5.1
Auto [4]		Auto throttle is engaged

Once you are on final approach / in the groove (K), you should now switch to the use of the IFLOLS system. This last phase should last around 15 - 17 seconds: any shorter and you may not be able to line up correctly, any longer and the LSO / Marshall will wave you off for being in the pattern for too long.

[Expand] IFLOLS
#	Name	Function
1	Ladder / Meatball	On this vertical bar with yellow/red lights, the orange ball ('meatball') will move up and down according to aircraft position. If the ball is too low, your aircraft is too low. If the ball is too high, your aircraft is too high. The goal is to line it up with the datum lights (2) for optimal landing: should the orange ball fall into red lights you are dangerously low and you will need to wave off (stop) the landing attempt.
2	Datum lights	These green horizontal bar of lights indicates your ideal line up: the goal is to have the orange ball ('meatball') line up with the datum lights for ideal vertical landing position.
3	Cut lights	On early approach the cut lights illuminate 2 ~ 3 seconds to indicate 'proceed with landing'. Any subsequent illumination means 'add power', according to length of illumination of lights
4	Wave off lights	Should the landing fall outside safe parameters (for example you are way too low), the LSO will call 'Wave Off!' and these lights will illuminate: you need to terminate the landing attempt and go around (climb away).
5	Emergency wave off lights	Identical in function to normal Wave Off Lights (4): for really dense pilots.

The IFLOLS landing phase will typically be accompanied by call-outs from the LSO, which can be found in the next chapter.

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LSO Callouts

LSO Callouts
Callout	By	Meaning
Paddles Contact	LSO	You are abeam LSO platform, begin final turn
3/4 mile call the ball	LSO	Can you see the meatball?
118 Tomcat Ball 5.6	Pilot	Modex / Aircraft Type / Meatball / Fuelstate / Auto* [1]
Go Manual	LSO	Disengage Autothrottles (ATC)
Roger Ball	LSO	Aircraft is cleared to continue
You are high	LSO	Aircraft is above glideslope
Power	LSO	Add power, aircraft below glideslope
Right for lineup	LSO	Come right to centerline
Come left	LSO	Come left to centerline
Easy with it	LSO	Control corrections are excessive
In Close	LSO	Aircraft at ramp
You are fast/slow	LSO	Adjust aircraft AOA, it is incorrect
Burner!	LSO	Select afterburner!
Wave-Off!	LSO	Execute Wave-Off!
Bolter	LSO	You missed all the arrestor wires

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Case 3 Landing

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  Case 1 Landing Pattern

[Expand] Case 3 Communication
#	Location	Pilot Action	Messages	Frequency
1	17000 ft, 75+ DME Outside of CCA (~50 nm)	Ask permission from Red Crown to enter.	Pilot: [Red Crown, 118, Mother's 250 for 75, Angels 17] Red Crown: [118, Sweet/Sweet, contact Strike on Button 3]	Button 4, 256.000 AM
2	16000 ft, 55 DME Inside CCA (~ 50 nm), outside Marshall Area (10 nm)	Ask permission from Strike to enter.	Pilot: [Strike, 118, flight of 1, Mother's 250 for 55, Angels 12] Pilot: [State 5.4, no Alibis] Strike: [118, Sweet/Sweet, Mother is IMC, Case 3] Strike: [Contact Marshall on Button 2]	Button 3, 265.000 AM
3	14000 ft, 52 DME	Ask for assigned stack from Marshall: Stack is given on radial 082, 22 nm behind the carrier and at 7000 ft. Marshall also gives other key information (write it down!)	Pilot: [Marshall, 118, 250 for 52, Angels 14, State 5.3] Marshall: [118, Mother's weather is 600 overcast, visibility 3 miles, altimeter 29.87] Marshall: [Case 3 recovery, Marshall on the 082, 22, angels 7.] Marshall: [Expected Final Bearing 262, Expected approach time 22, Approach button 18] Pilot: [118, Altimeter 29.87, Marshall on the 082, 22, angels 7. Expected approach time 22.]	Button 2, 264.000 AM
4	7000 ft, in holding pattern	Pilot has established holding pattern at 7000 ft: gives fuel state for Marshall to keep track off	Pilot: [118, established angels 7. State 5.1]	Button 2, 264.000 AM
5	All flights	Marshall constantly updates all flights with new info: bearing, visibility, altimeter QFH	Marshall: [118, altimeter 29.88. New final bearing is 265]	Button 2, 264.000 AM
6	7000 ft, leaving holding pattern	Pilot notifies Marshall the descent from holding pattern has begun, states altimeter setting + fuel state	Pilot: [118, Commencing, 29.88, state 4.8] Marshall: [118, roger]	Button 2, 264.000 AM
7	5000 ft (platform), descending	Pilot notifies Marshall he is passing 5000 ft (platform)	Pilot: [118, platform]	Button 2, 264.000 AM
8	1200 - 5000 ft, descend	Marshall hands pilot off to approach (can happen before reaching platform!)	Pilot: [118, checking in, state 4.6] Marshall: [118, switch button 18]	Button 2, 264.000 AM
9	1200 - 5000 ft, descending	Pilot checks in with approach: pilot may be asked to dirty up earlier / later to match correct landing intervals	Pilot: [118, checking in, state 4.5] Marshall: [118, final bearing 262]	Button 18, 251.000 AM
10	1200 ft, around 4 -8 nm DME	When ACLS is acquired, approach asks what ACLS ('needles') is showing. If unsatisfactory, new lock will be tried: if no lock approach will tell pilot to fly ICLS ('bullseye')	Approach: [118, say needles] Pilot: [405, fly up, on] Approach: [118, fly your needles] OR Approach: [118, fly bullseye]	Button 18, 251.000 AM
11	800 ft, 3/4 mile	LSO chimes in	LSO: [3/4 mile, Call The Ball] Pilot: [118, tomcat/hornet, ball/clara, state, auto*] LSO: [Roger Ball]	Button 18, 251.000 AM

[Expand] Case 3 Landing Pattern
Pattern	Step
A	Marshall stack: starting at 6000 ft, with increments of 1000 ftfor each flight / package
B	Platform, passing 5000 ft
C	10 miles DME, 600 ft, commence landing descent
D	6 miles DME, maintain 1200 ft ACLS (Automated Carrier Landing System)[1]
E	1.5 miles DME, 600 ft, commence landing descent
F	1 mile DME, 400 ft
G	3/4 mile DME, call the ballside number, tomcat/hornet, ball/clara[2], fuelstate[3], (auto[4])
H	1/2 mile DME, 200 ft
I	Wave off on Final Heading, climb to 1200 ft
J	Turn to downwind heading, using 10% speed G-turn
K	Maintain 1200 ft and on speed AOA, flaps/slats/gear/hook down
L	Turn into Final Heading via 18 ~ 22 degree bank turn
Speedbrake / ACLS [1]		As desired
Clara [2]		Ball is obscured, LSO will give instructions
Fuelstate [3]		Remaining fuel in thousands of pounds:5100 pounds -> 5.1
Auto [4]		Auto throttle is engaged

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References

US Navy Carrier Case 1/2/3 PDF File

Aircraft Carrier Communications, two hours worth of carrier radio chatter