Flight Path Vector
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Flight Path Vector
Guys & Gals, being new to the 737 NG I have never used the FPV before, nor has much been explained about its functions or advantages to me. I know its big on the Airbus, but few Boeing pilots I know use it.
Can anyone give me the low down on it, when is the best time to use it and for what etc?
Many Thanks,
S.C.
Can anyone give me the low down on it, when is the best time to use it and for what etc?
Many Thanks,
S.C.
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I suppose for one it would make doing non-precision approaches easier - just stick the nose down until the FPV indicates the required descent angle. It saves having to know the 3 and 5 times tables (I'm joking before anyone says anything 
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I find it useful only during raw data flying,put the vector on the horizon and you are level,no need to remember all those attitudes.Some use it to measure crab angle or even what tilt to use on the Wx radar(assuming it's fixed to the horizon).
I personally find it distracting to have it displayed during T\O or approach,just my opinion though!
I personally find it distracting to have it displayed during T\O or approach,just my opinion though!
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poor use on nonprecision app,actually is not recommended by Boeing.You have no way of determining a 3 deg GP,only by aproximation on the EADI (somewhere bellow 5 deg..
)
One use that Boeing recommends it for it's for weather radar :by tilting the antena at the aprox FPV indicated angle during climb or descent you can say if you'll enter or not through a cb top.
It may be used for level flight when FD not in use.
Important: "when on final approach,the FPV does not indicate airplane glide path relative to the rwy.ILS GP,VASI/PAPI or other means must be used for proper GP indication. "-FCTM 1.34
It can be also used in case of unreliable speed.
On the bus,you could fly 'bird in the cage' but on Boeing the cage is missing.
)One use that Boeing recommends it for it's for weather radar :by tilting the antena at the aprox FPV indicated angle during climb or descent you can say if you'll enter or not through a cb top.
It may be used for level flight when FD not in use.
Important: "when on final approach,the FPV does not indicate airplane glide path relative to the rwy.ILS GP,VASI/PAPI or other means must be used for proper GP indication. "-FCTM 1.34
It can be also used in case of unreliable speed.
On the bus,you could fly 'bird in the cage' but on Boeing the cage is missing.
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So its good on a climb or descent to determine whether you'll make it above the red weather in time, and its debatable whether to use it on a non precision approach. But what is its official purpose, since, as alexban says, you don't have the cage for using is it you have unreliable speed 
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going to seattle to take one of our first NG's ,we asked ,what about this new feature,the FPV?
The answer was,never mind that,just a new gadget added by the somputer guys.Or something like that.
My guess is that the FPV is just the beggining of instalment of some new,not ready yet systems or indications.
They are developing ,for ex,a vertical display indication,positioned bellow the EHSI map indication,which will display the vertical profile of the a/c,very usefull I guess during app.
So ,I guess,soon,will see some software improvement ,that will take use of the already installed FPV.
The answer was,never mind that,just a new gadget added by the somputer guys.Or something like that.
My guess is that the FPV is just the beggining of instalment of some new,not ready yet systems or indications.
They are developing ,for ex,a vertical display indication,positioned bellow the EHSI map indication,which will display the vertical profile of the a/c,very usefull I guess during app.
So ,I guess,soon,will see some software improvement ,that will take use of the already installed FPV.
A Flight Path Vector is a potentially very useful display, especially with HUD, but it requires a good understanding and a different way in thinking about flying.
First, it is important to distinguish between systems that only have flight path angle (FPA) and those which are true vectors (FPV).
Second, most systems are based on inertial references, but there are some that use a mixture of air data for the vector and ancillary displays such as flight path acceleration.
FPA is normally constrained to the pitch plane and shows the flight path with respect to the ‘inertial’ horizon; thus when used in conjunction with an attitude scale (EFIS PFD) it shows where the aircraft is going as a climb or dive angle. It is most valuable when displayed on the EFIS ND as ‘dive arc’, in these displays the range is normally referenced to the selected altitude, but may use the FMS, you need to know which applies and when, if they alternate.
When the symbol is displayed in the HUD there is an additional advantage in VMC by indicating exactly where the aircraft is flying towards in the real world (or in some new systems the synthetic world, IMC use). Thus if the vector is on the runway threshold then that’s where the aircraft is going, the climb / dive angle indicating the descent path, which may or may not be the desired path.
Some difficulties have been seen in training in how to maneuver the aircraft with reference to the vector, e.g. for a safe approach landing the vector should be over the runway glidepath origin and the actual descent angle at 3 deg, but as the aircraft is maneuvered via pitch and airspeed, any readjustment will change both the FPA and/or the overlaid aiming point, this can be a complex control / visual feed back loop.
True vector displays (FPV) use the lateral component of the flight path in addition to PFA, the horizontal inertial component is referenced against the aircraft longitudinal datum 'bore-sight'. In a cross wind this shows the drift angle, but again training complexities may arise with yaw due to engine failure that still requires an indication of lateral acceleration (‘slip’ ball).
In my experience, a FPV HUD adds valuable visual capability especially where ground aids, lighting etc are poor, but those conditions are now infrequent. FPVs are very good displays for monitoring the aircraft position and motion, but this still requires approach guidance scales; FPVs also help with where to look for the runway when transitioning to visual before landing. Use of FD guidance overlaying a FPV display is yet another complex issue which can lead to more training and monitoring problems.
A lesser advantage is that the angle between the ‘bore-sight’ and the vector approximates to the aircraft AOA. This is the vector sum of the bore-sight pitch angle / horizon value, and the climb dive angle / to FP value.
The downside is that the visual display draws the focus of attention away from other displays that are still required for safe flight; the FPV encourages tunnel vision (target fixation).
The FPV can be a great aid on an NPA provided you start at the correct place and cross check altitude against range during the approach, otherwise all that FPV tells you, is the angle at which you will hit the ground – never where you are, it is not a FMS or EGPWS replacement. Do not use FPA on the EFIS ND if it requires the selected altitude to be set to the airfield height – very hazardous.
I would not choose to install a HUD with FPA unless it was the only method of achieving low visibility operations (land and takeoff), but if the FPV is available as an option for EFIS, I would have the option, but also think very carefully about the training issues before use e.g. misunderstandings about NPAs.
First, it is important to distinguish between systems that only have flight path angle (FPA) and those which are true vectors (FPV).
Second, most systems are based on inertial references, but there are some that use a mixture of air data for the vector and ancillary displays such as flight path acceleration.
FPA is normally constrained to the pitch plane and shows the flight path with respect to the ‘inertial’ horizon; thus when used in conjunction with an attitude scale (EFIS PFD) it shows where the aircraft is going as a climb or dive angle. It is most valuable when displayed on the EFIS ND as ‘dive arc’, in these displays the range is normally referenced to the selected altitude, but may use the FMS, you need to know which applies and when, if they alternate.
When the symbol is displayed in the HUD there is an additional advantage in VMC by indicating exactly where the aircraft is flying towards in the real world (or in some new systems the synthetic world, IMC use). Thus if the vector is on the runway threshold then that’s where the aircraft is going, the climb / dive angle indicating the descent path, which may or may not be the desired path.
Some difficulties have been seen in training in how to maneuver the aircraft with reference to the vector, e.g. for a safe approach landing the vector should be over the runway glidepath origin and the actual descent angle at 3 deg, but as the aircraft is maneuvered via pitch and airspeed, any readjustment will change both the FPA and/or the overlaid aiming point, this can be a complex control / visual feed back loop.
True vector displays (FPV) use the lateral component of the flight path in addition to PFA, the horizontal inertial component is referenced against the aircraft longitudinal datum 'bore-sight'. In a cross wind this shows the drift angle, but again training complexities may arise with yaw due to engine failure that still requires an indication of lateral acceleration (‘slip’ ball).
In my experience, a FPV HUD adds valuable visual capability especially where ground aids, lighting etc are poor, but those conditions are now infrequent. FPVs are very good displays for monitoring the aircraft position and motion, but this still requires approach guidance scales; FPVs also help with where to look for the runway when transitioning to visual before landing. Use of FD guidance overlaying a FPV display is yet another complex issue which can lead to more training and monitoring problems.
A lesser advantage is that the angle between the ‘bore-sight’ and the vector approximates to the aircraft AOA. This is the vector sum of the bore-sight pitch angle / horizon value, and the climb dive angle / to FP value.
The downside is that the visual display draws the focus of attention away from other displays that are still required for safe flight; the FPV encourages tunnel vision (target fixation).
The FPV can be a great aid on an NPA provided you start at the correct place and cross check altitude against range during the approach, otherwise all that FPV tells you, is the angle at which you will hit the ground – never where you are, it is not a FMS or EGPWS replacement. Do not use FPA on the EFIS ND if it requires the selected altitude to be set to the airfield height – very hazardous.
I would not choose to install a HUD with FPA unless it was the only method of achieving low visibility operations (land and takeoff), but if the FPV is available as an option for EFIS, I would have the option, but also think very carefully about the training issues before use e.g. misunderstandings about NPAs.
The Boeing FPV is an add on, probably as a result of Airbus' Track/FPV function being popular. My experience of it was that it was another button to play with on mind numbing Atlantic crossings, but you soon got tired of that. It was only useful when flying a visual circuit because it told you that you were level. Descent on a NPA was best done by dialing in 5 x your groundspeed on the MCP VS function.
The Airbus FPV is much more useful.
The Airbus FPV is much more useful.
