# Howto: Procedure Turns

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Hi, While we all wait for the big bird, I have a question: If doing a non precision approach that involves a procedure turn, how does one use the MCP to make sure that the rate of turn is standard etc.?I have been watching the GOL World Air Routes DVD and one of the approaches they do is such an approach. In the DVD the captain constantly changes the heading on the MCP, which I can understand. It seems to me that he is doing so to try to follow the programmed track on the ND. If that is indeed the case, how does he then program the route such that the turn is standard? Is is based on guestimation and experience?Thanks, :-waveBoazKSEA

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> While we all wait for the big bird, I have a question: If>doing a non precision approach that involves a procedure turn,>how does one use the MCP to make sure that the rate of turn is>standard etc.?I don't think there is a requirement anywhere that the turn must be at "standard rate". As a matter of fact big airliners usually do not turn at standard rate, most likely at half that rate. Also the topic is a bit academic since passenger jets hardly ever fly procedure turns these days.Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

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Yeah, there's no requirement that the turns be standard rate, but there is a 200 knot maximum speed in a PT to ensure a reasonable rate of turn. At 25 degrees of bank and 220 KTAS, I calculate a rate of turn of about 2.3 degrees per second...close to standard rate. Keep in mind that rate of turn is not airplane dependent...it's purely a function of bank angle and true airspeed. So a 747 at 25 degrees of bank and 200 KTAS will have the same rate of turn as a King Air at the same speed and bank angle.

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> Also the topic is a bit academic since passenger jets>hardly ever fly procedure turns these days.as an air traffic controller, I disagree with this statement. There are many airports that only have non precision approaches. We also have several in Washington Center where we clear for full ILS with procedure turn. granted, most of these are CRJs or smaller, but I have had a 737 go into one of these fields.In South America, there are a lot more.I don't know if it is the same now, but 10 years ago, NorthWest restricted all approaches in China to NDB only. No VOR or ILS approaches due to concern on the maintenance of the navaids. KLM flies into Bonaire TNCB and it only has a NDB approach. TNCM only has VOR approach and KLM flies the queen in here too.to answer the original question, most procedure turns are published as to the heading to fly. once you turn on the outbound heading, start your clock and fly one minute, turn back 180 degrees (most air carriers will use the MCP heading select mode for this) and fly back to intercept your approach. One minute is one minute - in a C172 or a B744, you just fly farther in the B744 :Dto quote the AIM http://www.faa.gov/atpubs/AIM/Chap5/aim0504.html#5-4-7On U.S. Government charts, a barbed arrow indicates the direction or side of the outbound course on which the procedure turn is made. Headings are provided for course reversal using the 45 degree type procedure turn. However, the point at which the turn may be commenced and the type and rate of turn is left to the discretion of the pilot. Some of the options are the 45 degree procedure turn, the racetrack pattern, the tear-drop procedure turn, or the 80 degree

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>Yeah, there's no requirement that the turns be standard rate,>but there is a 200 knot maximum speed in a PT to ensure a>reasonable rate of turn. At 25 degrees of bank and 220 KTAS,>I calculate a rate of turn of about 2.3 degrees per>second...close to standard rate. Keep in mind that rate of>turn is not airplane dependent...it's purely a function of>bank angle and true airspeed. So a 747 at 25 degrees of bank>and 200 KTAS will have the same rate of turn as a King Air at>the same speed and bank angle.Doesn't the amount of horizontal lift component (or stick back pressure, and rudder pressure) also factor in here? As an extreme example of what I mean, consider a stunt plane doing a knife-edge maneuver. 90 degrees of bank, but zero turn rate.Or does what you say above assume a level and coordinated turn?

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>Doesn't the amount of horizontal lift component (or stick back>pressure, and rudder pressure) also factor in here? As an>extreme example of what I mean, consider a stunt plane doing a>knife-edge maneuver. 90 degrees of bank, but zero turn rate.>>Or does what you say above assume a level and coordinated>turn?Good clarification...yes, it assumes a coordinated turn...I'm not positive about needing to be level, I pulled out one of my aerodynamics books and it uses the term "steady." It seems to me that steady is generally used to mean "unaccelerated." So, even in a steady, coordinated climbing or descending turn, you'll have the same turn performace regardless of airplane size (at a given bank angle/true airspeed).

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>> Also the topic is a bit academic since passenger jets>>hardly ever fly procedure turns these days.>>as an air traffic controller, I disagree with this statement. >And what exactly do you disagree with? I said "hardly ever" which does *not* mean "never". Also since the original poster mentioned MCP it means 737 or bigger jets but he probably even meant 747. Frankly I would like to know how many times full procedure turns were flown last year by a 737 or heavier in the US. Was it 1% or more likely closer to say 0.001% of approaches. Michael J.WinXP-Home SP2,AMD64 3500+,Abit AV8,Radeon X800Pro,36GB Raptor,1GB PC3200,Audigy 2http://www.precisionmanuals.com/images/forum/747400.jpghttp://www.hifisim.com/images/asv_beta_member.jpg

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>Also since the original poster>mentioned MCP it means 737 or bigger jets but he probably even>meant 747. I actually was not trying to be too specific on any kind of plane, but used the 737 as that is what I have currently. My original question was more how to ensure that the rate of turn is standard (assuming that is important) when you have no way of seing if you are doing a standard rate turn or not. Finally, I was not trying to limit myself to American airspace. I know that there are several airports, especially smaller ones served with 737's, that have non precision approaches.Thanks,Boaz

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>is standard (assuming that is important) when you have no way>of seing if you are doing a standard rate turn or not.No, it is not important. It is much more important that PT gets completed within some amount of airspace. You can't keep on slowly turning and turning and getting too far from the runway - you have to stay within the protected airspace.>smaller ones served with 737's, that have non precision>approaches.These day, at least in the US, flying a non-precision approach will *not* result in having to fly a PT. They will give you radar vectors to intercept the final course and off you go. Even to small airports. "Vectors to final" is pretty much standard these days in the US.Michael J.

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Yeah, that's what I mean by level. For a given angle of bank, you obviously need a certain amount of back pressure to maintain altitude. If the turn were accerated, you'd have to increase bank angle to avoid climbing. I guess that's what they mean by "steady" also, like you said, unaccelerated.

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"My" formula for completing a coordinated 180 deg turn is this:V/7/Tan(bank angle) = seconds to complete 180 deg turnWhere V is speed in MPH.Obviously it does not depend on type of aircraft or even its weight.Michael J.

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>These day, at least in the US, flying a non-precision approach>will *not* result in having to fly a PT. They will give you>radar vectors to intercept the final course and off you go.>Even to small airports. "Vectors to final" is pretty much>standard these days in the US.>>Michael J.>Well, except where terrain and/or radar coverage do not permit vectoring to final. Gunnison, Colorado comes to mind (http://www.myairplane.com/databases/approach/pdfs/00517I6.PDF) ...Continental and United (maybe others too) serve it in the winter with Airbuses/737s...Denver Center can't vector to final because of terrain constraints and radar coverage. Those of us who spend a fair amount of time flying in the mountains still do procedure turns regularly for non-precision and ILS approaches.

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>>These day, at least in the US, flying a non-precision>approach will *not* result in having to fly a PT. They will give you>>radar vectors to intercept the final course and off you go.>>Even to small airports. "Vectors to final" is pretty much>>standard these days in the US.I disagree again ;) in the enroute environment (the Centers) we can only vector to a final if the approach is depicted on the radar scope including the IAF. Also, you have to be on a display range :D You are totally right on that part. commercial carriers probably make .001% non precision approaches. the air taxis and civilians make up most non precision approaches.

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