Not Following ILS

[lehbird]

Hello:

Have been flying this AC successfully for weeks now with no issues except for one; I can not get the AC to intercept / follow the ILS glideslope. I have the freq. tuned, it shows up on the HSI, APP button depressed, but it wont follow. I have no problem with LNAV, VNAV, just APP. What am I not doing?

Thanks,

Dave

[cmbaviator]

On samedi 21 mai 2016 at 4:32 PM, lehbird said:

Hello:

Have been flying this AC successfully for weeks now with no issues except for one; I can not get the AC to intercept / follow the ILS glideslope. I have the freq. tuned, it shows up on the HSI, APP button depressed, but it wont follow. I have no problem with LNAV, VNAV, just APP. What am I not doing?

Thanks,

Dave

can you provide a video ?

can you see the LOC and G/S deviation beam on the PFD ?, did you capture the G/S from below ?

[Ubbi]

Do you mean the LOC or the GS? If it does not capture the LOC: maybe you did not turn in the right course?

[FloB]

Also make sure you intercept the GS from below. The AP will not dive to capture the GS.

Flo

 

 

[lehbird]

Thanks for the replies. I am a fairly proficient pilot and have a solid understanding of G/S interception. (sorry to say I have been at this for MANY years )

 I am approaching the approach at an intercepting course and below the G/S.  And yes, the LOC and G/S deviation beam do appear on the PFD. My guess is there is some other button or switch I need to toggle / press on the 733? 

Thanks,

Dave

[mmerelles]

did you set the correct ILS COURSE for NAV1? this is mandatory for this bird.

[lehbird]

4 hours ago, mmerelles said:

did you set the correct ILS COURSE for NAV1? this is mandatory for this bird.

I did not. Honestly, I never do on any aircraft. I am sure I am wrong for not doing so, but AC typically still follow the ILS. But as you say, with this bird, perhaps you must. Thanks. 

Edited May 23, 2016 by lehbird

[cmbaviator]

9 hours ago, lehbird said:

I did not. Honestly, I never do on any aircraft. I am sure I am wrong for not doing so, but AC typically still follow the ILS. But as you say, with this bird, perhaps you must. Thanks. 

 

 

yeah you must, this is not an A320 nor B777, it doesn't set the ILS course automatically.

 

imagine that your ILS course is 180 but is set to 090 on the MCP, you can imagine that you'll never intercept the LOC, lol

[TDPlane]

Same goes for 757 and 767 (type sharing).

[lehbird]

14 hours ago, tdplane said:

Same goes for 757 and 767 (type sharing).

I guess that is my point; I fly many different versions of 757's and 767's, 737NG's never set the course, never have an issue. I guess I assumed Boeing's would be consistent that way.

Edited May 25, 2016 by lehbird

[mmerelles]

On 23 de mayo de 2016 at 4:27 PM, lehbird said:

I did not. Honestly, I never do on any aircraft. I am sure I am wrong for not doing so, but AC typically still follow the ILS. But as you say, with this bird, perhaps you must. Thanks. 

 

Edited May 25, 2016 by mmerelles

[mmerelles]

17 minutes ago, lehbird said:

I guess that is my point; I fly many different versions of 757's and 767's, 737NG's never set the course, never have an issue. I guess I assumed Boeing's would be consistent that way.

 

you mean, you flied them on real life or proficient over inaccurate simulations making you get bad habits? 

[kneighbour]

This is very interesting. I assumed that setting the COURSE bug was just a visual thing - ie to more or less remind you of the bearing you will be flying once you have intercepted the LOC. Good to know.

[Tchou]

Setting the course is to more or less tell the fmc where to go to keep following the right path once the LOC is intercepted…

 

[lehbird]

Just to close the loop on this, not setting the course was my issue. As soon as i did, it followed. As I said before, I have flown many Payware Addons of the 737's, 747's, 757's, 767's and none of them require you to set the course to follow the ILS. So either those aircraft dont require it, or it just wasn't modeled correctly.

 

Thanks for all your help!

[tkyler]

2 hours ago, lehbird said:

none of them require you to set the course to follow the ILS. So either those aircraft dont require it, or it just wasn't modeled correctly.

I do not think it is not a matter of setting the course in order to FOLLOW the ILS, but rather dialing in the course to fly to INTERCEPT the ILS.  ...at least as I understand it...I admit I didn't code this up, but maybe Jan / Nils can chime in once they see the post here.

-tkyler

[Nils]

50 minutes ago, tkyler said:

I do not think it is not a matter of setting the course in order to FOLLOW the ILS, but rather dialing in the course to fly to INTERCEPT the ILS.  ...at least as I understand it...I admit I didn't code this up, but maybe Jan / Nils can chime in once they see the post here.

-tkyler

Correct. The 737-300 autopilot localizer capture is a two-stage process. When the deviation pointer starts moving and the FMA goes from VOR/LOC ARM to VORLOC, the autopilot will initially command a 30 degree bank towards the dialed in CRS heading. As the localizer deviation pointer comes closer to center, the autopilot switches to commanding the heading that is required to keep the localizer centered, based on deviation error and deviation error rate of change signals.

[lehbird]

OK; you guys are talking well above my paygrade now  All I was trying to say was that on all other AC I have flown, I could have the course set to ANYTHING and as long as the ILS was tuned in, and the approach button depressed, the AC would follow the approach. Thanks again.

[Litjan]

On 13.6.2016 at 6:32 PM, lehbird said:

Just to close the loop on this, not setting the course was my issue. As soon as i did, it followed. As I said before, I have flown many Payware Addons of the 737's, 747's, 757's, 767's and none of them require you to set the course to follow the ILS. So either those aircraft dont require it, or it just wasn't modeled correctly.

 

Thanks for all your help!

I would put some money on the guess that all the many payware add-ons you flew did not simulate the 737 - 300/400/500 series?

If that is so, then it is easily explained by the fact that these "other" Boeings have an autotune feature that will both set the ILS frequency AND also the inbound course (as read from a database). So no dialing of the inbound course is required.

Jan

 

[dr_anthony]

Several months ago such of discussion was at avsim.su, and there was real PIC who tried to set offset LOC course on real aircraft, in this situation airplane flown on LOC path, with selected course, but with crab angle, like with crosswind.

 

[Litjan]

On 11.7.2016 at 6:28 PM, dr_anthony said:

Several months ago such of discussion was at avsim.su, and there was real PIC who tried to set offset LOC course on real aircraft, in this situation airplane flown on LOC path, with selected course, but with crab angle, like with crosswind.

 

 

Yes, this will work if the angle is not too large - the plane will adjust for the drift. But if the set course is grossly wrong, the plane will turn "off" the localizer signal and then have no way of recapturing the centerline.

Jan