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gdscei

Autoland Issue At Jfk

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Hello guys,

 

I've done a flight yesterday across the atlantic (EHAM-KJFK) to get myself adjusted to long flights... It was all fine up until the landing.

I tried autoland, but was surprised when the plane did not automaticly fly the glidescope, and I had to land manually. I had made sure the ILS was correct on the FMC, and I pressed the LOC button, waited for "G/S" to appear on the PFD and then turned on APP at the correct altitude (according to my FMC 1500ft for landing on RWY 04L). I did reach the 1500ft at the last moment, so maybe that's the issue? (the plane did not descend quick enough; probably a FMC error on my part)

 

Does anyone have an idea why this failed? Is 1500ft too low (and so is my navdata incorrect), or was this a different problem? I understand this could come off as a newbie question, but I kinda am new to the 777 ;) I did the tutorial flight succesfully, and I applied the same mechanics to this flight (at least, I think).

 

Another thing btw, for the 737 NGX, there was a display mode where you could see the glidescope (or just ascend/descend path), this doesn't seem to be on the 777.. Is there an alternative to this display on there?


Deniz Zoeteman

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Hello guys,

 

I've done a flight yesterday across the atlantic (EHAM-KJFK) to get myself adjusted to long flights... It was all fine up until the landing.

I tried autoland, but was surprised when the plane did not automaticly fly the glidescope, and I had to land manually. I had made sure the ILS was correct on the FMC, and I pressed the LOC button, waited for "G/S" to appear on the PFD and then turned on APP at the correct altitude (according to my FMC 1500ft for landing on RWY 04L).

 

Does anyone have an idea why this failed? Is 1500ft too low (and so is my navdata incorrect), or was this a different problem? I understand this could come off as a newbie question, but I kinda am new to the 777 ;) I did the tutorial flight succesfully, and I applied the same mechanics to this flight (at least, I think).

 

Need more info about it. What do you mena by "didn't fly the glideslope"? Were you in control or was the autopilot? 


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

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Need more info about it. What do you mena by "didn't fly the glideslope"? Were you in control or was the autopilot? 

 

Autopilot was engaged and in APP mode. What I mean with "didn't fly the glidescope", is that the plane did not descend along the glidescope, it just stayed at 1500ft, until the last moment where I took control over.

Were you above or below the G/S when you hit the "APP" button?

 

Catching the G/S from above is an airline choice that has has to be enabled in the livery options.

This might be the problem actually. I was flying a KLM livery. I will check the options for it out, see how they differ from the PMDG house variant.


Deniz Zoeteman

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Autopilot was engaged and in APP mode. What I mean with "didn't fly the glidescope", is that the plane did not descend along the glidescope, it just stayed at 1500ft, until the last moment where I took control over.

This might be the problem actually. I was flying a KLM livery. I will check the options for it out, see how they differ from the PMDG house variant.

 

Did you come in above or below the G/S?


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

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Did you come in above or below the G/S?

As I said in the OP, the plane did have trouble descending quick enough, so I am going to say I leave the possibility open I came in above the G/S. The problem is, I can't exactly tell where the G/S starts exactly without the handy ascend/descent path display like on the 737NGX (or I should look more at charts, though I don't know how accurate they are with FSX, considering I heard that ILS signals are more limited in height in FSX than IRL).

I did try descending quickly to 1000feet, and thought that the glidescope would maybe catch me then, but it didn't. 


Deniz Zoeteman

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As I said in the OP, the plane did have trouble descending quick enough, so I am going to say I leave the possibility open I came in above the G/S.

I did try descending quickly to 1000feet, and thought that the glidescope would maybe catch me then, but it didn't. 

 

According to the chart for 04L you need to be established on the G/S by DME 4.5 at 1500ft. How far out/in were you if you remember?


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

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According to the chart for 04L you need to be established on the G/S by DME 4.5 at 1500ft. How far out/in were you if you remember?

 

I can't remember exactly off the top of my head, however I should be able to figure this out tonight, I will let you know.

Thanks for the help so far.


Deniz Zoeteman

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I can't remember exactly off the top of my head, however I should be able to figure this out tonight, I will let you know.

Thanks for the help so far.

 

No problem. I find in this situation it's often good to go back and repeat the approach to see if there's an issue with Navdata or just that i made a mistake :)


captainhenrychen-1.jpg


Boeing777_Banner_Pilot.jpg


 


James Bennett

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No problem. I find in this situation it's often good to go back and repeat the approach to see if there's an issue with Navdata or just that i made a mistake :)

Yeah, I will try to take a smaller flight with same approach at KJFK, so I can quickly find out what the problem is (though if I want to accurately display the issue, I'd need to do a step climb to FL410 before TOD...) Although then again, it would be extremely difficult to exactly replicate the issue, as winds always change :)


Deniz Zoeteman

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An "exaggerated traffic pattern" - depart KJFK, land KJFK, get up to, say, 12k feet in between, descent a couple of nm out and head for your 4.5 nm DME mark at 1.500 ft, should do.

 

In FSX, LOC comes alive about 27 nm out, G/S alive just under 20 nm out (but you have to be on the correct side of the beam to see it displayed!), and for a standard 3° descent you'll need 3 nm horizontal for every 1.000 ft vertical - that's why the charts say 4.5 nm DME at 1.500 ft.


What happened to AVSIM

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An "exaggerated traffic pattern" - depart KJFK, land KJFK, get up to, say, 12k feet in between, descent a couple of nm out and head for your 4.5 nm DME mark at 1.500 ft, should do.

 

In FSX, LOC comes alive about 27 nm out, G/S alive just under 20 nm out (but you have to be on the correct side of the beam to see it displayed!), and for a standard 3° descent you'll need 3 nm horizontal for every 1.000 ft vertical - that's why the charts say 4.5 nm DME at 1.500 ft.

 

Ah thanks for the info - will try that out!


Deniz Zoeteman

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and I pressed the LOC button, waited for "G/S" to appear on the PFD and then turned on APP at the correct altitude (according to my FMC 1500ft for landing on RWY 04L).

 

Pressing LOC before APP is not required.  I'm not sure where this old wives tale popped up (likely in sim land, or back in the days of the first autopilots), but it's just that: an old tale.

 

 

 


I did reach the 1500ft at the last moment, so maybe that's the issue? (the plane did not descend quick enough; probably a FMC error on my part)

 

It could be, but the FMC only knows as much as is programmed into it (in the nav data) and as much as you tell it (by adding in constraints, where applicable).  What makes matters worse is that you flew into JFK.  The whole NY area is a highly vectored area, which means that the FMC is going to be nearly worthless when it comes to VNAV and LNAV.

 

Here's why:


Kyle Rodgers

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Pressing LOC before APP is not required.  I'm not sure where this old wives tale popped up (likely in sim land, or back in the days of the first autopilots), but it's just that: an old tale.

(...)

 

 

In FSX the LOC indication appears some 10 nm before the G/S indication shows up. That results in a few seconds, where people are tempted to press the LOC button (APP wouldn't work yet during those seconds).

 

 

Deniz,

the KLM livery actually defaults to "no G/S before LOC" ... and I've just noticed you fly a fictional livery!   :P


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