• How To Land On An Aircraft Carrier For Real

    How To Land On A Carrier By Matthew Hummer
    Before I talk about how we land on a carrier I should explain angle of attack, or AOA. Angle of attack is the angle between the mean chord of your aircraft's wing and the relative velocity of the oncoming air. Coupled with the optical landing system it's the heart and soul of a carrier-based landing.
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    Angle of attack is important because it's one of the factors affecting lift that you can change in flight. When you pitch up, you momentarily rotate the aircraft about its lateral axis. This causes the angle of attack to increase, and as AOA increases your wing develops more lift. Your plane climbs. Increasing AOA increases lift. At a constant AOA and power setting AND when the plane is straight and level, all forces are in balance. Knowing this we can also deduce that in straight and level flight and at a constant angle of attack, an increase in power will also cause the plane to climb. The increase in thrust produces a corresponding increase in airspeed, and since our AOA is constant, with the increase in airspeed we develop more lift. The airplane climbs. In order to maintain straight and level flight while increasing airspeed, you must reduce AOA. To fly slower you have to increase AOA. HOWEVER...you can only increase angle of attack so far until the oncoming wind can't wrap around the wing anymore. The angle is too sharp. It separates off the backside of the wing and this is called an aerodynamic stall. The point on the angle of attack graph where this happens is called critical AOA. Note that theoretically you could be going extremely fast, pull back really hard on the stick, and if the plane rotates about its axis fast enough you could exceed the aircraft's critical angle of attack and stall the wing even with sufficient airspeed for flight. Here's the important stuff. At a constant angle of attack in straight and level flight, a DECREASE in power will cause the plane to DESCEND. This is the underlying principle of flying an AOA approach, which is exactly how we do it going to the boat. Since angle of attack is measurable by the angle of the wind to the chord of the wing, we can tell our AOA by sticking a probe out on the wing and showing the readout in the cockpit. AOA is measured in arbitrary "units". Typically, the high 20's is where you'll find critical AOA. In the T-45C Goshawk, critical AOA with gear and flaps down is 26 units. Increasing AOA past 26 units will result in a stall. Besides the AOA gauge, we also have what's called an AOA INDEXER. This is the little green, amber, and red thing next to the HUD that turns on when the gear is down and locked.
    We know that as we slow down we must increase angle of attack, but we also know that we can't slow down and increase AOA TOO much or we'll stall. One way to tell just what speed and AOA we need is from tables and graphs...but the simple way is by the AOA indexer. When the amber donut in the center of the indexer is the only indicator illuminated, you're flying just the right speed for approach. This is called being on-speed. If you get too slow for the approach the green chevron will illuminate. The color and direction are important...it tells you exactly what you need to do to fix the situation. Green means go...add power. Adding power will flatten out your approach and reduce the angle of attack. Your angle of attack is high because you're slow or your descent angle isn't steep enough. The chevron points down...lower the nose. Lowering the nose will increase your rate of descent. Either action will cause the chevron to disappear in favor of the amber donut, but always remember that with a correction of pitch you're going to need to adjust the power. The opposite is the red chevron. The red chevron points up. Pitch up. Red means stop...back off the power. In either case you'll increase angle of attack, which is exactly what the indexer is telling you you need to do. Keeping the amber donut illuminated will keep you on a nice slightly nose-high glide to the deck. If you slow to on-speed and stabilize in straight-and-level flight you'll find an associated airspeed given your weight. For the T-45C this is roughly 141 with gear down and half flaps. Once stabilized with the airplane trimmed out it should fly itself. The beauty of an AOA approach is that once you have that condition you're basically done making serious inputs. Decreasing power will cause the airplane to descend without changing angle of attack and the opposite is true for adding power. Trim the plane for on-speed. When it comes time to descend from pattern altitude, smoothly reduce power slightly and bump the nose over just a touch to start the aircraft descending. From here on, all corrections to descent rate should be made with power only. The only thing you're using the stick for is lateral control. But how do we get to that point? Like this...
    So this picture is from one of my pubs about field carrier landings but it applies just the same. Instead of a runway, substitute the boat. The setup begins 3 miles directly behind the carrier...not behind the approach course, but behind the boat itself and aligned on the same course that the boat is driving. We want to be 800' above water's surface at 250-300 knots and heading straight for the ship with the hook down. What we're aiming to do is fly past the ship just slightly to its right and as we pass the bow we're going to flop, chop, and pop: flop the plane over into a 70 degree angle of bank left turn across the bow of the ship for 180 degrees while simultaneously deploying speedbrakes to full and chopping the power to idle. This is called an overhead break (sometimes also called the overhead, or carrier break). The turn in combination with the loss of thrust and speedbrakes should bleed off a ton of energy. The goal is to roll out after 180 degrees of turn at 200 knots or less (safe gear speed). The speedbrakes stay OUT from then until landing. We land with the speedbrakes out to provide a margin of error and to allow the engine to operate at a higher rpm for a given airspeed where it'll be more responsive. We're on downwind now, 180 degrees to our original course and on a reciprocal of the ship's course with the speedbrakes out and our airspeed below 200 kts. Descend to 600'. Drop the gear and bring flaps to full. Perform landing checks...gear down, flaps/slats full, hook down, harness locked, speed brakes extended, anti-skid switch OFF, checklist complete. Abeam your intended point of landing (the ship) make your radio call to the LSO. "Blazer 302, gear & flaps, 122 knots, 2.5 (fuel in thousands of pounds), number 1 (qual number), downwind". 15 seconds after making your abeam call (at what's called the 180) start a 2-300 fpm, 30 degree angle of bank descending turn to the left. You should be focused on the instruments and not outside for the first half of the turn to final. Halfway through the turn (called the 90) establish a 500 fpm descent, 30 degrees AOB turn, on-speed, and start peeking outside. As you finish your 180 degree turn you get to a point called the start. The start is just what it sounds like...the start of the groove. The groove is carrier talk for the final approach. Roll out wings level, 425 feet, 15 seconds behind the boat at approximately 3/4 mile and spot the Fresnel lense on the aft left side of the ship. If you see it, call the "Ball". If not, call "Clara". From here you should be concentrating on two things: Keeping the orange "meatball" centered top to bottom and side to side in the big green cross, and maintaining that on-speed airspeed (amber donut). The ball is your position on the glideslope and the amber donut is your angle of attack. Keep the descent coming down all the way to the deck. From the time you hit the start until touchdown NOTHING SHOULD CHANGE. Don't flare. Hold the amber donut until you impact the deck. Hopefully you would've picked up a wire but either way when the wheels touch, throttle comes to MRT, speedbrakes retract, and expect to go around. If you "bolter", leave gear and flaps down, establish a climb to 300' and turn downwind while climbing at 130 or on-speed, whichever is greater. Re-enter the pattern and do it all over again until you trap!
    That's it on the landings. Matthew Hummer Matthew Hummer is an instrument-rated, multi-engine, commerically licensed pilot with C172/PA28/DA42/T6B/T45C time, currently on active duty in the US Marine Corps
    This article was originally published in forum thread: How to land on an Aircraft Carrier. For real. started by jetguy19 View original post

    21 Comments
    1. KEUGVirtual's Avatar
      KEUGVirtual -
      Thank you for this article. This is the best explanation of this I have seen (for obvious reasons). Thank you for allowing us to help apply this challenge to the Sim.
    1. RaysAviation's Avatar
      RaysAviation -
      This was a superb description of the entire procedure for a carrier landing. This I am positive will help a lot of simmers to increase the realism of this kind of flight.

      Thank you Matthew, This really helped me understand carrier landings better. I am an experienced glider pilot and know quite a lot about aerodynamics, but your explanation of this procedure was really good, and helped me ease up trying to land on a carrier. Normally I would pitch up and down to keep on track in stead of just using the throttle which gave me a very stressful final approach to the carrier.

      This was excellent

      Ray
    1. napamule2's Avatar
      napamule2 -
      Not even a 'hint' or mention of use of (elevator) pitch trim, which I find works good for Sim COPS. Is it strange that I rely, and use, plenty of up pitch trim to INSURE successful trap? Or is this only 'useful' for Sim flying and not for 'real' flying? So why is it 'easy' for me to do traps with 95% success in FSX Acceleration (moving carrier) where I fail 50% of time when I don't use pitch trim? (Don't say luck). Model (F-18)? Dynamics? PC specs? Empty stomach? It's a mystery as how you land (with 'ideal' AOA) without ANY pitch trim.
    1. max_gradient's Avatar
      max_gradient -
      >> "AOA is measured in arbitrary "units""

      What do you mean by this? AOA is measured in degrees!
    1. RaysAviation's Avatar
      RaysAviation -
      The AOA is NOT measured in degrees eventhough stated as an angle. Please read description below:

      The AOA Instrument is based upon sound aerodynamic principle. The term "angle of attack” is the angle between the relative wind and the chord of the airfoil. The new term you may not be familiar with is "angle from zero lift” which is the angle measured from the reference angle when aligned with the relative wind creates no lift. Angle of attack and angle from zero lift are identical to each other for symmetrical airfoils. For non-symmetrical airfoils, the difference between angle of attack and angle from zero lift is a fixed constant. When the term angle of attack or AOA is used for nonsymmetrical airfoils, the term angle from zero lift should be substituted in order to be technically correct. Your AOA instrument technically measures angles from zero lift. When the PRO display indicates 0 units AOA, the aircraft properly calibrated is creating no lift. The Angle of Attack Instrument (AOA Instrument) utilizes pressures from two pressure ports located on your aircraft’s upper and lower airfoil or probe, and pressures from your aircraft’s pitot and static ports. The result of dividing the airfoil or probe differential pressure Pw by the pitot static differential pressure Pp is a coefficient of pressure (CP). There is a unique variation of CP with angle of attack. This variation is very linear over most of the airfoil's AOA. The process of calibrating the full range AOA Instrument to a specific airfoil requires as few as two coefficients of pressure that are permanently recorded into the angle of attack instrument’s memory.

      Hope this helps

      Ray
    1. max_gradient's Avatar
      max_gradient -
      If I read your post correctly, you are effectively saying is that the angle of attack IS measured in degrees, as I have stated, however due to the technical implementation you have described (measuring the CP) the AOA instrument in most situations will not give the 100% correct angle but only an approximation based on pressure calibration?
    1. RaysAviation's Avatar
      RaysAviation -
      The AOA is a calculation with input from various sources and not a measured angle as stated above. It cannot be described as being degrees since you cannot measure it as degrees and since you cannot compare it to other units this makes it a arbitrary unit as stated.

      I am sorry if my previous post was unclear, but the fact is that the AOA is not actual measured degrees but in fact arbitrary units as Matthew wrote.

      Ray
    1. asos's Avatar
      asos -
      This must be for FSX.

      No mention of arresting wires is made--how does the plane stop then?

      In fs9 I have used all sorts of addons to add arresting wires--all of them, in fact, plus some more tricks I made myself through gauges.

      I have trapped over 1000 times in fs9, but only a coule in FSX through the AI Carriers stuff.

      Nick
    1. napamule2's Avatar
      napamule2 -
      If you have GOLD Edition of FSX (FSX Deluxe plus Accelleration) the wires are already there to use on MOVING carriers. They are AI and have a 'route' they sail from/to and knowing their destination you can set 30 min before arrival (in 'Time and Season' menu) to 'catch' the moving carrier and do traps. Use 'Top Down' view to find the tell-tale wake of carrier (zoom in/out with '-' and '+' keys).
      Chuck
    1. asos's Avatar
      asos -
      Thanks,

      I had forgot all that with the default AI carrriers. Can anyone remind me how I find them?
    1. asos's Avatar
      asos -
      Of course, one flaw of FSX (and FS9 also) is that the LSO is not simulated. In real navair ops the LSO is a great and necessary help and no traps are made without his help. And on the LSO platform, there many LSO guys, not just one, most being senior pilots.

      The AOA indexer lights are repeated on the nose gear leg of all aicraft and the LSO can see them all the time when the trapping a/c is close by just looking at the lights on the nose gear leg. That helps him with his correction callouts. In addition, there are are regulations or directions on how the LSO is to speak to the pilot, so that he does not sound offensive or too cirtical. One example is this:

      The LSO says to the pilot: "You're working too low"---instead of saying "You'e too low". The 2nd comment is considered negative and bad and it may upset the pilot. The first one is polite and postive and emphasizes the work the pilot is putting in, acknowledging his part in it and also boosting his confidence.

      Confidence is a very important factor, cosnidering the extreme and dangerous nature of any trap on a carrier deck and the ordeal the guy about to trap is undergoing.

      "Approach" magazine, a USN publication, has lots of stuff on all this, with digarams and texts, and I may be posting some items that are directly related if I find the time to scan them.

      By the way, all of the stuff so far posted in here is very old stuff, and has been around since the 1960's. I have known all of this since I was 20 and I am 66 now.
      Only some of the a/c have changed, and the old bridle has been replaced by the tow bar.

      One drawback of fsx is that aircraft like the E-2 and EA-6B are absent in acceleration. Not to mention many earlier types.

      Alphasim did a wonderful job with its USS Enterprise for fs9, and I still consider that as the best carrier addon ever.
      If some developer did something similar for fsx, he would make money.

      FlightDeck 3-4 and 5 were also good, and one of them works for FSX--was it Abacus who did it?
      I have used all of the above many times.


      Nick
    1. keeska's Avatar
      keeska -
      As a check of any accepted aerodynamic reference will show AOA is the Angle between the relative wind and a reference line on the aircraft. For most small aircraft (Piper, Cessna, Mooney, etc.) the reference line is the wing chord line. For jet transport aircraft it is often a line on the fuselage defined by the manufacturer. AOA is measured in degrees when designing the airfoil and evaluating the airfoil's characteristics.

      However in flight is it not measured in degrees. A previous post went into some detail about how AOA Instruments work. Basically AOA is calculated based on input from various air pressure sensors on the aircraft. Often AOA gauges in aircraft are not accurately calibrated and the actual AOA value in degrees is not shown. High quality gauges are calibrated (sometimes daily) during the flight testing phase. Even then the data may be recorded in the air and the actual AOA calculated on the ground after the flight.

      BTW - most of you already know that airspeed in aircraft is not measured in knots, miles/hour or kilometers/hour. It is calculated based on pressure difference and displayed in the knots, etc. Likewise altitude is not measured in feet or meters. It is also based on pressure difference and shown as feet/meters.
    1. jesse.kasper07's Avatar
      jesse.kasper07 -
      Quote Originally Posted by napamule2 View Post
      Not even a 'hint' or mention of use of (elevator) pitch trim, which I find works good for Sim COPS. Is it strange that I rely, and use, plenty of up pitch trim to INSURE successful trap? Or is this only 'useful' for Sim flying and not for 'real' flying? So why is it 'easy' for me to do traps with 95% success in FSX Acceleration (moving carrier) where I fail 50% of time when I don't use pitch trim? (Don't say luck). Model (F-18)? Dynamics? PC specs? Empty stomach? It's a mystery as how you land (with 'ideal' AOA) without ANY pitch trim.
      In the real world you don't use pitch trim. You trim to a certain AOA by the abeam and you leave it. Don't touch it. This does two things. It sets a certain AOA that is critical for your landing attitude so that the hook has a higher probability of catching a wire and it sets that basic attitude so that when you roll around in the groove you can devote 80% of your scan to glideslope and lineup as the AOA will remain fairly steady throughout the approach. In FS I've noticed it's a problem with the model / flight dynamics that are inherit within the system that require you to use more pitch trim in the sim. In the real airplane you remain fairly steady and also in the airplane it is very easy to make the minute adjustments that you need compared to what you get in the sim. I hope this helps.

      Overall though, it still gives you the right idea and is exactly what it's supposed to be, a simulation. I will never say however that being an "expert" in FS will ever help you at the boat. I actually believe it will hurt you more than it would ever help you as you would develop habit patterns that guarantee you a 100% boarding rate in the sim that would get you killed in real life. Just my two cents though.

      Jesse
    1. max_gradient's Avatar
      max_gradient -
      Thank you keeska, this is also the way I understand it after some research.

      The AOA is defined as an angle, by definition its unit is a degree.

      In some aircraft that have calibrated AOA instruments it is displayed in degrees. In other aircraft that lack instruments with proper calibration it is displayed in units/whatever.
    1. Deacon211's Avatar
      Deacon211 -
      A very good article. A few points I'd like to address:

      1. You absolutely trim the aircraft on speed! I have no doubt Matt knows this, but probably didn't want to write a book here. Remember this isn't "Everything You Need to Know About How to Land on a Carrier". That would require considerably more space.

      Certainly, you would like to be perfectly trimmed up on speed by the abeam, but you may or may not be. You will know this if, every time you take your eyes off the AOA indexer, you see something other than an amber donut. If you are trimmed fast, I guarantee you will wind up fast no matter how hard you try to hold the stick motionless. Same same if you are trimmed slow. The AOA gauge is very sensitive. If you keep seeing a fast indication, put some nose up trim in there...a couple of clicks. If you are still not seeing a near constant amber donut, put in a couple more. Keep doing this until you are on speed. Period. Don't be sloppy.

      On an aircaft like the T-45, you can slowly learn to really nail that AOA. On an aircraft that doesn't have centerline thrust however, like the T-2, you will be clicking down every time you add power and clicking up every time you take it off. Luckily, I don't think FSX models that particularly annoying attribute.

      Matt did a great job about explaining the importance of the AOA approach. One other reason that AOA is so important is that your hook is targeted to catch the three wire on the carrier with a centered ball only when your aircraft is "on speed" (i.e. on AOA). Depending on your aircraft, the point of that hook may be 30 or more feet from your head. Every degree you are off your optimimum AOA will raise or lower that hook point by several inches. Considering the fact that you are trying to put that hook point on a surface that you are encountering at an angle of only about 3 degrees, those few inches can turn an OK 3 wire into a Taxi 1 wire or a bolter. Try throwing darts at a dartboard that's lying flat on a table and you'll see what I mean.

      And that's when the ship isn't pitching.

      2. I can't add much to the degree/units discussion other than to say that most (perhaps all...perhaps not) naval aircraft AOA gauges are displayed in "units", because that's what the NATOPS says. That's not a very intelligent explanation, I grant you.

      But considering that the smartest student naval aviator I ever knew tried to turn four A-4s into one "A-16" on an off target rendezvous thus becoming the smartest former student naval aviator I ever knew....I'm OK with that.

      Or, in other words, there's a reason that engineers shaped the landing gear handle like a wheel....

      3. I may have missed a technological breakthrough or two in "meatball" technology, but I believe that you must still use the landing area centerline for lineup on the ship. If the ball provides lateral guidance, then that is a newer feature that I don't believe is modelled in FSX.

      As an aside, remember that, if the ship is moving, your landing area is moving to the right as you fly your approach due to the angled deck. You will need to make a series of small "right for lineup" corrections to remain on centerline. Don't crab.

      Thanks again Matt for a great article on a subject that often constitutes a little bit of PFM for most real pilots and Semper Fi!
    1. steveboston's Avatar
      steveboston -
      Thankyou Jetguy 19 for giving us "The Bible" on carrier traps. I love these (FS9+ Flight Deck) I have read all the posts as well and I accept that "It ain't always like that" but here's why (In my opinion).
      FS in its many forms has very compicated maths to mimic real flight and many "paths" through those sums to get a model of - say an F18 - to behave exactly at say 400kts level at 900 feet in 15 deg C. There is then no guarantee it is still exact at 160 or 660, or that drag or pitch moment of gear, brake, flaps etc is still 100% accurate. Worse still, the FS model may have wrongly placed thrustlines, wings, tail, gear (and while we are at it my pet hate - centre of rotation of model NOT placed at centre of gravity).
      Even Microsoft were guilty - using FS Editor I once checked their 737 or Lear or whatever (long time ago - forget which sim etc). Mathematically it was a straight-winged Pilatus Porter clone made big. Now with experiments I found their own editor correctly modelled (up to a point) sweepback giving - for example - yaw/roll coupling, every 3 deg correctly equalling 1 deg of dihedral etc etc. BUT they never used it - instead they used lots more tricks and odd maths.
      Payware or freeware I often have to tweak aircraft a bit - if only so they sit ON the ground properly and don't jump if I change views. There are some very good Maths Model sim designers out there but also many who get there by cloning the nearest thing to hand or patching something up - crude example - new Wonderplane flies right except it is too slow - fix by reducing form and induced drag - OK now! (except it is now a military transport that glides better than a Duo-Discus).
      So Jetguy is right and the others are too - in that we are having to compensate for the unrealistic behaviour of our sim model. Unfortunately, unless we fly real world Naval as well, we can't know what is most life-like from our collection and how everything else differs from true performance. I have learned a lot though - mainly to fly the whole circuit properly - I was dirtying up much later and not capturing speed/AOA until finals - should be more relaxing now! Heart pills for sale going cheap!
    1. mikeandpatty's Avatar
      mikeandpatty -
      The reason the Navy AoA Indexer is in units is that it is a standard MILSPEC item. Maintenance, training, logistics etc is much easier than having custom units.

      Internally, the AoA device "bug" is calibrated to be located at the 3 O'clock position for any type of airplane, but the actual degrees of AoA is different for each type of plane. All three items of the system - the vane, the gauge and indexer have to work together, and this is checked on routine test flights as well as specific checks if the system is repaired or replaced.


      In my early days (1960's or so), AoA indexers were all yellow. Later they got smart and colored them.
    1. jskinner's Avatar
      jskinner -
      I would like to recommend some packages for those who would like to do carrier landings wherever you like.

      USS Nimitz & USS Eisenhower Version 2.0 by Javier Fernandez (jafergon@gmail.com) . A working ai carrier. With a lift for access to the hangar bay, etc.

      aicarriers by Lamont Clark - lc0277@nerim.net to place ai boats.

      RCBco-11 By Rob Barendregt and Doug Dawson for launch and arrestor action and sounds.

      I've enjoyed these programs for a long time using FSX with Acceleration pack.

      John
    1. Deacon211's Avatar
      Deacon211 -
      Quote Originally Posted by mikeandpatty View Post
      The reason the Navy AoA Indexer is in units is that it is a standard MILSPEC item. Maintenance, training, logistics etc is much easier than having custom units.

      Internally, the AoA device "bug" is calibrated to be located at the 3 O'clock position for any type of airplane, but the actual degrees of AoA is different for each type of plane. All three items of the system - the vane, the gauge and indexer have to work together, and this is checked on routine test flights as well as specific checks if the system is repaired or replaced.


      In my early days (1960's or so), AoA indexers were all yellow. Later they got smart and colored them.

      Interesting! What did you fly Mike? By the time I got to A-4s and T-2s, we had the standard red, yellow, green.

      Indeed the AOA gauges were all the exact same model. I just never asked why they didn't just use degrees.

      We'd need a Hornet guy to chime in, but I thought that their AOA was in degrees. Of course, I could be wrong and there was always a tendency to use the terms interchangeably...a common habit in aviation in all manner of terms.
    1. PRB's Avatar
      PRB -
      Just to add to the discussion on AOA, here is a page from an A-7 maintenance manual. The implication here is that "units" is a term used to describe how the indicator is designed to indicate, and for a specific aircraft, "1 unit" does equal some number of degrees of AOA, in the case of the A-7, 1.5.

      - Paul