What is HDG TRACK and V/S FPA for?

[Guest Ali]

I know this changes the flight director and is called the bird. As you as looking at the aircraft on a cross section from front to back. When is it used? When is it handy? What procedures can you use it for? I was told you use it during crosswinds to correct drift and track.Many thanks.Regards,Alexander Martin.-----------------------------------TMPRADIO DJOnair Monday - Friday 1900GMT @ http://www.tmpradio.com

[Guest Calum]

Hello Alexander , :)HDG-V/S = Heading - Vertical SpeedTRK-FPA = Track - Flight Path AngleYou are correct , they both are different modes of FD operation.HDG-V/S is the mode where the autopilot ( or you ) will use a Heading ( the Flight Computer systems will take wind into account to provide you with an accurate heading ) indication to fly the correct flight path ( route ). And your climb path will be established by vertical speed ( the aircraft will pitch up to maintain a constant vertical speed ) , which will keep the airspeed stable as well.HDG-V/S is the easiest of the two to use , and for most training pilots on the airbus , as they can quickly grasp the idea of " crossing the lines in the middle ". If the bar goes up , you go up , if the bar moves left , you move left.If TRK-FPA is the active mode for FD , then this will use the correct Track to follow the flight path , and the Flight Path Angle to produce a climb attitude. Flight Path Angle is to do with a constant degrees of climb on the attitude indicator , not so much with the vertical speed indicator.TRK-FPA can appear confusing because most time in wind conditions , the aircraft symbol ( black bars and small black sqaure in center ) will be at a completly different indication from the command indications.Difference between HDG and TRK is wind direction and speed.If there is no wind at all , when you are flying , HDG and TRK will be the same. But ...if you are HDG 090' and there is wind from 360' at 9 knts , that is direct crosswind. Your aircraft will be HEADING ( pointing its nose ) at 090' , but the wind is hitting the aircraft side on , and will be pushing it about 099' , this is drift ( where the aircraft is drifting off its path ). If you left it long enough while trying to fly a flight path of 090' , you would see the aircraft would eventually be getting pushed off ( drifting off ) that path towards the south , because of the wind.The HDG-V/S mode doesnt show TRK/Drift angles on the Attitude Indicator itself , but can be found at the bottom of the PFD or on the ND ( Navigation Display ) , this information is displayed at the top of the Navigation Arc ( as a Yellow bar for HDG , and a Green Diamond for TRK ) , so you can easily use either mode for operations.So basically , they both show the same information , its just that TRK-FPA shows it to you all in the same place , and with HDG-V/S , you need to look down or at the ND as well.You may have seen TRK-FPA being used in crosswind conditions , and this is probably because the pilot can see at a glance , exactly what drift he/she needs to compensate for.There are also some Airbus aircraft i have seen with HUDs ( Heads-Up-Displays ) , this will just show the same information and layout , except without the pilot having to look down , and this can be used in bad weather take-offs and landings , where it is important to watch in front of you.So to recap :HDG and TRK are different because of windV/S and FPA are different because they use different measurements to calculate climbs/descents.Either Mode can be used with ease , although TRK-FPA is more often used in Crosswind conditions as it is easier to identify immediatly any drift corrections that need to be made.I think ( or hope ) i have answered your qeustions :)If you would like to know more about how to USE the TRK-FPA indicators to fly as accurate as you would with the HDG-V/S , then just post here and i can explain what the indications mean and how to follow the route and climb/descent paths without using HDG-V/S. Good LuckCalumSorry for the length of this post and lack of smilies ;)

[Guest vrandar]

One description of it is as follows: "The flight director bars indicate the movement of the sidestick to achieve the target as selected on the FMA. Namely, if you select a higher altitude and pull, then select a different heading and pull, you are targeting a climb and a turn. The flight director bars will initially indicate that you must pull back on the sidestick, and push it to one side. When the aircraft is stabilized in the climbing turn, the flight director bars will be centered, as no input is required from the pilot, (until you stop the climb and/or turn).Now, the Flight Path Vector or "bird" as we call it is a very different animal altogether. In normal operations, it is used during hand flown visual approaches. Or sometimes, with the autopilot, using the Flight Path Angle, or "cage" - you try to put the "bird" in the "cage".What you have to understand, is that the "bird" indicates altitude change, not attitude. And it indicates track, not heading. So you have to understand the difference, to understand the "bird". If the aircraft altitude is not changing, then the "bird" will be on the horizon, regardless of the nose pitch attitude. Handy when trying to regulate loss of altitude during a hand flown approach. As a matter of reference, when the "bird's" tail is just under the horizon, then the aircraft is descending on a 3 degree angle, ideal under normal approaches.In a no wind condition, when track and heading are the same, then the "bird" will be centred. But as the bird shows track flown, not heading, it is handy when setting heading when landing in a strong crosswind, with no ground lateral guidance, like an ILS. You put the "bird" on the runway track, then regardless of heading you are on the correct track for the runway. And if you are using the autopilot, and using the "bird" in track mode, the aircraft will maintain the correct runway track all the way during the approach even if the crosswind is changing"

[Guest Calum]

Hello all ,regarding what Rob said about the FPA being about altitude rather that attitude , that makes sense , so its better to go with whats said there , than in my post about the FPA.Even i learned something new :)Calum

[Guest Ali]

YES PLEASE! :)>If you would like to know more about how to USE the TRK-FPA>indicators to fly as accurate as you would with the HDG-V/S ,>then just post here and i can explain what the indications>mean and how to follow the route and climb/descent paths>without using HDG-V/S. Regards,Alexander Martin.-----------------------------------TMPRADIO DJOnair Monday - Friday 1900GMT @ http://www.tmpradio.comEdited to remove previous (long) post quoted in full