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Captains,

Is there someone who can explain me in simple words the logic behind "HDG SEL", (you know, that annunciation on the FMA) in conjunction with LOC/APP.

My problem:  when appraoching for an ILS landing, and when being vectored to the ils-interception point, all of a sudden the plane starts to turn the complete other direction…
Only way to interrupt is to deselect AP and FD and select both back on when established in the good direction.
I have selected a STAR and APPROACH, but as i’m being vectored the plane flies away from the original route.
It is like it wants to turn back to one or other point behind me?!?
The problem usually starts after i have engaged LOC and/or APP modes.

Difficult to explain this intelligible.

The FMA shows me: SPD | HDG SEL | FLCH SPD (or VS) in conjunction with LOC and/or G/S

What can cause the plane to react like this.  I’m sure i miss something but i am unsure what.

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HDG SEL is simply the heading that you are commanding the aircraft to maintain.  The FMA roll mode of HDG SEL will not intercept a LOC for you, you need to press the APP button and small white letters below HDG SEL should say LOC.  This means the A/P is armed to capture the LOC.  Once captured, the roll mode will change from HDG SEL to LOC.

I am missing a few steps in your story, when on a vector to intercept final approach course (LOC) I presume you are indicating HDG SEL and when within range of the ILS you press APP button to arm LOC and GS.  Correct?  Engaging LOC and APP do not have to be done separately in most cases, you normally press only the APP button.

Have you flown the tutorial?

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2 hours ago, Headley said:

Is there someone who can explain me in simple words the logic behind "HDG SEL", (you know, that annunciation on the FMA) in conjunction with LOC/APP.

My problem:  when appraoching for an ILS landing, and when being vectored to the ils-interception point, all of a sudden the plane starts to turn the complete other direction…

The FMA shows me: SPD | HDG SEL | FLCH SPD (or VS) in conjunction with LOC and/or G/S

What can cause the plane to react like this.  I’m sure i miss something but i am unsure what.

Following on from Dan's reply, there is nothing wrong with using HDG SEL (and FLCH) to intercept the ILS localiser, provided your intercept track angle is always less than 120 degrees to the inbound localiser course. 

The use of HDG SEL mode with the aircraft heading controlled by use of the HDG knob is actually considered normal practice on the B744 for most intermediate approaches.  Ideally, you should aim for an intercept heading of between 30 to 45 degrees towards the inbound course to allow for a safe and positive capture (passenger comfort too!).  In practice the intercept heading should never more than 90 degrees, otherwise the autopilot is very likely to turn the aircraft the wrong way and/or you risk going through the localiser and ending up with a false LOC capture.  Incidentally, the use of LOC mode (i.e LOC armed) will in fact allow for capture of the inbound ILS localiser course when on an intercept track angle of up to 120 degrees, whereas APP Mode (i.e. LOC and G/S armed) allows for capture of the glideslope on a reduced intercept track to the ILS localiser course of up to 80 degrees.

Another good tip is to always capture the ILS localiser using LOC mode first.  You should only arm APP Mode (i.e LOC and G/S armed) after the aircraft is established on the correct ILS localiser inbound course and it is stable.  Then, as you approach the glideslope from below (i.e. never from above) you can arm the APP mode and capture the glideslope, usually at the published approach altitude. This helps to reduce the risk of an unstable or rushed approach, or capturing a false glideslope lobe from above, or descending on the ILS with an incorrect altimeter setting.  For safety reasons it is imperative that you do not descend on any glideslope until you are safely established on the correct localiser inbound course and know exactly where you are and at the correct altitude for the distance from the field (verified using the ILS DME, procedural height checks etc)

Bertie Goddard

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1 hour ago, berts said:

Incidentally, the use of LOC mode (i.e LOC armed) will in fact allow for capture of the inbound ILS localiser course when on an intercept track angle of up to 120 degrees, whereas APP Mode (i.e. LOC and G/S armed) allows for capture of the glideslope on a reduced intercept track to the ILS localiser course of up to 80 degrees.

Good info.

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Thanks for the reply's Dan & Bertie.

As i said, it's difficult to explain, but i will try again.
I was in HDG SEL and FLCH, and over the aerodrome, the controller vectored me on a heading 030.  When out of +/- 10miles of the Rwy , he turned me Right HDG 240, and cleared me to intc ILS Rwy 24.  At that point i engaged LOC and APP.

I think: maybe i turned the Hdg Sel knob to fast to Hdg 240 (as Bertie said) and the "Thing" was confused and turned the other way around...

Quote

Ideally, you should aim for an intercept heading of between 30 to 45 degrees towards the inbound course to allow for a safe and positive capture (passenger comfort too!).  In practice the intercept heading should never more than 90 degrees, otherwise the autopilot is very likely to turn the aircraft the wrong way and/or you risk going through the localiser and ending up with a false LOC capture.

Will try to keep this in mind for the future.

One more question:
The speed at witch you intercept the localiser, what should that be ideally?  I was flying +/- 180 knots at the point of intercepting the localiser.  Too fast?

@Dan, don't worry about the tutorial, i flew the tutorial when the QOTS came out for FS9 and FSX.
But nevertheless, i learn every day:cool:

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1 hour ago, Headley said:

,,,, think: maybe i turned the Hdg Sel knob to fast to Hdg 240 (as Bertie said) and the "Thing" was confused and turned the other way around...

to turn right (more than 180o) ..... initially turn the bug right but not beyond (in this example) to say 150o, then as the turn progresses past 060o, set bug to 240o

never turn the bug left (ie the shorter way) !!

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1 hour ago, vadriver said:

never turn the bug left (ie the shorter way) !!

Thank you,

Well i was aware of that indeed. Anyway thanks for the advice about the progressive heading turn.

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14 hours ago, berts said:

  For safety reasons it is imperative that you do not descend on any glideslope until you are safely established on the correct localiser inbound course and know exactly where you are and at the correct altitude for the distance from the field (verified using the ILS DME, procedural height checks etc)
 

Bertie Goddard

Bertie,

You explanation was right on, perfectly stated. The only item worth reminding is that you should always check the chart for new airports you are going to to make sure that it is not an offset LOC.

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My two cents, there are too many differences between products....please fly the Tutorial.... it is just a short hop KDEN-KSFO.

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On 3/31/2018 at 10:22 AM, Headley said:

The speed at witch you intercept the localiser, what should that be ideally?  I was flying +/- 180 knots at the point of intercepting the localiser.  Too fast?

@Dan, don't worry about the tutorial, i flew the tutorial when the QOTS came out for FS9 and FSX.

The intercept speed will depend on several factors, such as how far and how high you are from the airfield, the intercept angle, the current flap setting as well as the final flap and landing weight you have programmed into the B744 FMC.  Descent in icing conditions and the associated engine thrust required can also catch you out if you don't allow extra distance (i.e. speed versus time) for it in your descent calculations.  No matter what your intercept speed is, you should always avoid making a rushed approach and aim for a continuous descent profile if at all possible, gradually slowing down and extending the flaps as you get closer and lower towards the airfield and the final approach.  As Dan says, read the PMDG tutorial, but a good general guide at or below approx 3,000ft agl is to initially intercept the localiser with Flaps 10 set and speed Flaps 10 + 10kts  and commence descending on the glideslope with Flaps 20 and Gear down.  You should be fully established and speed stable in the landing configuration by 1000ft agl

On 3/31/2018 at 2:52 PM, Bob Marton said:

 The only item worth reminding is that you should always check the chart for new airports you are going to to make sure that it is not an offset LOC.

Agreed.  There is no substitute for good airmanship and this includes thorough preparation, planning and vigilance; both on the ground and in the air.  In fact, prior to top of descent  most pilots will have mentally rehearsed and briefed the other crew member(s) for the approach, including the missed approach (just in case!). 

I don't know of many offset LOC approaches that the B744 uses today.  However, the most notable exception for the B744 was probably RWY 13 IGS approach into Hong Konmg's old airport, Kai Tak.  As far as I am aware, most operators had a strict and comprehensive briefing and training requirement, which was carried out initially in the simulator and then followed with a flight there under supervision, before each pilot was cleared to operate there.

On a relatively short hop like the one Dan mentions between KDEN-KSFO, the operation can get very busy with ATC, holding etc; so it can sometimes be worth including a short preliminary brief for the expected arrival procedure as part of the departure briefing.  At least this will confirm you have the correct landing charts readily available and you won't have to rush eating your first class chicken meal approaching top of descent and end up suffering with indigestion!

Bertie 

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I check the pink diamond on approach and do a small turn adjust towards it before capture it will change to a solid pink diamond then I hit APP button.

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9 hours ago, berts said:

...

Bertie 

 

1 hour ago, rjfry said:

...

Thank you for replying.

The reason i started this thread was indeed having trouble with the plane behaving unexpected when in HDG SEL.  And every time i was under control of an approach controller (i fly only online - IVAO) who put me: or to high above the glide slope or let me turn to short on final approach course, witch is why i had to turn to fast and the plane started to behave like i discribed (turned the opposite direction).
I thought there was some logic behind HDG SEL (like there is a logic behind VNAV PATH and VNAV SPD), but is was all pilot error by turning the HDG Knob to fast and confusing the autopilot, like Bertie said earlier.  When flying without controller i roughly follow the path like i see on Flight Tracker and usually have no problems at all.

Thanks again for your real live input all ... 

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12 hours ago, Headley said:

The reason i started this thread was indeed having trouble with the plane behaving unexpected when in HDG SEL.  And every time i was under control of an approach controller (i fly only online - IVAO) who put me: or to high above the glide slope or let me turn to short on final approach course, witch is why i had to turn to fast and the plane started to behave like i discribed (turned the opposite direction).
I thought there was some logic behind HDG SEL (like there is a logic behind VNAV PATH and VNAV SPD), but is was all pilot error by turning the HDG Knob to fast and confusing the autopilot, like Bertie said earlier.  When flying without controller i roughly follow the path like i see on Flight Tracker and usually have no problems at all.

Thanks again for your real live input all ... 

In that case here are two recommendations from me. 

First of all, file an Air Safety Report with IVAO about their approach controller because it seems he might need some more aircraft vector training.  Secondly, the next time you have issues controlling your B744 using the autopilot in HDG Select mode, simply disconnect it and fly the aircraft manually.  You will find it is much more fun! :biggrin:

Bertie

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