Hi all, just a quick question.

I was perorming (or trying to perform) an autoland at Linate (LIML) and couldn't engage the second A/P on landing to enabke the autoland. Now I know this topic has been discussed over and over again but what happened twice still puzzles me. The approach from the south at LIML gets you lined up with rwy36 crossing DIXER about 20 nm out. The vor/loc is alive straight away but the gs interception occurs about 9nm out. I tried to activate CMD B immediatelly after the APP changes from ARM to ACT but with no results (it just disconnects the other a/P). Now I know this is usual when the engagement of the second A/P is not done correctly, but I don't understand what I do wrong.

Any thoughts?

Hi all, just a quick question.

I was perorming (or trying to perform) an autoland at Linate (LIML) and couldn't engage the second A/P on landing to enabke the autoland. Now I know this topic has been discussed over and over again but what happened twice still puzzles me. The approach from the south at LIML gets you lined up with rwy36 crossing DIXER about 20 nm out. The vor/loc is alive straight away but the gs interception occurs about 9nm out. I tried to activate CMD B immediatelly after the APP changes from ARM to ACT but with no results (it just disconnects the other a/P). Now I know this is usual when the engagement of the second A/P is not done correctly, but I don't understand what I do wrong.

Any thoughts?

 

Not an expert on this subject, but make sure both Flight Director switches are on, both nav radios tuned to the localizer freq. I ususally hit the Approach button first after lining up on the Localizer and then click on the Comand B. I've never really had any issues. I know there are some limitations due to distance, height, etc, If I'm remembering correctly from wading through those threads in the past.

Hi, thanks for your reply. Yeah I'm aware of the limitations and requirements. Height wise you need to engage the second A/P above 1000ft RA, I'm not aware of any distance limitations besides that the second A/P must be engaged AFTER GS capture, so that's the limitation. Since I've never had this problem since I've started using the correct procedure, but it's always been a standard intercept at about 10 nm I wonder whether the long lined up approach take a part in it?

HI Matteo!

The correct procedure is to make sure both FD are on with PF side active. Secondly tune both Nav's to the ILS frequency and set both to inbound course setting. When cleared for approach tune the ND to approach setting so that you can observe the localizer needle. One you are receiving a solid localizer signal as indicated by the readout across the top of the PFD unit. Counter verify that you are receiving DME readout (if available) and then press "APP" on the MCP and if it arms (green light) then you can immediately select the second CMD and it should also arm. There is no requirement to intercept localizer or glideslope first. If you are a distance from the station sometimes the readout on the annunciator (top line of the PFD) will indicate ILS and GP instead of GS. In that case wait until closer to the station and then de-select, re-select APP again and you should get ILS and GS indicators. If this little action disconnects one of the CMD units, simply re-select it. If you can only get one CMD to operate at a time then either you are not following the above sequence and setup or you may have an alignment issue with one of the IRS units. They both must be aligned for autoland.

New to the 737ngx, but why do you have to put freq into the radio.

 

Freqs in other planes are enter with the navigraph or some other source.

New to the 737ngx, but why do you have to put freq into the radio.

 

Freqs in other planes are enter with the navigraph or some other source.

 

I would make a guess that since the 737 was designed in the mid 60s' that was the procedure then and Boeing has never updated the design to automatically tune ILS frequencies thru the FMC based upon the runway selected to land on.

 

Michael Cubine

Yep, 737s dont have radios with automated tuning like newer planes do. Have to do it by hand...

Yep, 737s dont have radios with automated tuning like newer planes do. Have to do it by hand...

 

737 classic can autotune.

737 classic can autotune.

Proof?

Proof?

 

Download this part of real FCOM - http://www.smartcock...Navigation.html

Pages 11.20.6, 11.31.5, 11.10.13 contain proof.

I don't think FCOM is saying that the NAV radios are automatically tuned to the approach in the FMC. Ii is saying that the aircraft's position is obtained in some cases from DME radios which are tuned to the strongest signal which may or may not be the ILS transmitter. The referenced FCOM pages don't say that the NAV radios are automatically tuned.

I'm sorry, I didn't understand the question. NAV radios must be manually tuned for approach.

Yes, yes, rsvit is right in that 737CL radios will, of course, autotune to keep up with DME updating (the NG does this as well, but the DME updating radio sets dont have an interface to look at - the frequencies can be found in CDU though).

 

However neither CL nor NG will autotune approach frequency unlike, say, 744.

Just wondering if it's possible that you had an autopilot failure. I had that happen on only my 5th or 6th flight in the bird. My first autopilot stopped working when I stepped away for a few minutes. Came back to an aircraft that was diving and climbing LOL. I tried turning it on and it just wouldn't. Finally tried the second autopilot and it turned on and took over. Then I started looking at everything, the FMC, MCP and nothing. Just couldn't figure out why it wouldn't engage. Finally went into the PMDG options under the aircraft and failures and found out that one decided to stop working. Surprised me too because I hadn't enabled failures. It was just automatically enabled to happen randomly at any time and I didn't luck out on that one.

Probably you bumped into your controls on your way out and broke the AP.