RNAV Go Around Proceedure

[Guest taylorwass]

Hi everyone just wondering how i go about doing go arounds from RNAV approaches.I'm on the approach and my minumums are 510 feet, i have 500 dialed into the alt select window VNAV and LNAV are on. I hit minimums and don't see the lights. So i hit the TOGA screw and this disconnects the autopilot and the FMC displays "unable crz alt." I then put LNAV back on but VNAV won't go back on. What am I doing wrong and could somebody guide me throught the whole proceedure please. Many thanks!Taylor Wass

[Guest s_L_Y_F_a]

Why did you dial 500 feet into you MCP alt window?The altitude you set up in the MCP alt window should be the next altitude constraint described in your plates under the missed approach procedure section.For example if your approach plate says that you have to hold at xxxxx int at an altitude of 4000 feet, you would dial 4000 into your MCP alt window, if there is no other altitude constraint for this missed approach procedure.

[downscc 1,327]

The "unable next altitude" could also be a quark in the way the procedure is written. Use Speed and Vert Speed on the MCP and fly the missed approach as published. Often, the FMC is calculating the direct distance to the next fix with altitude constraint, which is different from the route that you'll acutally follow.

[Guest taylorwass]

I had 500 in the window so that while on VNAV it will enable me to descend if i had the next altitude constraint dialed in it wouldn't let me descend to get on the approach. I added "OVERFLY AT OR ABOVE 100" to the proceedure so it will overfly the missed approach waypoint above 100. VNAV still disconnected?What do i do if I want to go back and do the approach againThanksSorry for posting again, Firefox trouble

[cowpatz 243]

Check your key assignments. You may have TOGA and the AP disconnect mapped to the same key. The AP should not disconnect when you select TOGA. When on the approach select the MCP altitude to the missed approach altitude. At the MAP if not visual select TOGA and Flap 20. Positive CB gear up. At 400 ft AGL LNAV and 1000ft AGL VNAV. If VNAV is not looking too flash then select FLCH. Clean up to Flap 5 initially and a good speed is 200 kts. Once you are levelled out decide what you want to do. Remeber that one push of the TOGA button gives you 2000 fpm climb. If you want more then press it again to get full TOGA thrust.CheersSteve

[Guest taylorwass]

Hi, thanks for that advice. I used the TOGA screw on the MCP not a key assignment.Just a request, do you recall a while back I was trying to make RNAV approaches for Rockhampton? You mentioned that you were making files for atc to recognise it or something. How did you go?ThanksTaylor

[cowpatz 243]

Oh yeah I remember that. Yes I got it working I fine. I was supposed to send you the files wasn't I? My apologies for that. From memory the GPS approaches were the same as the RNAV approaches. I will find them and send to you. CheersSteve

[cowpatz 243]

Hi Taylor.Try this. Installation instructions are included in the zip file.CheersSteve

[Guest taylorwass]

Thanks a million =D

[zubart 5]

First of all, during a RNAV approach set the MCP altitude window to 600 feet if you minimums are 510 feet just before crossing the FAF. During descent when the airplanes altitude is about 1000 feet above minimums, reset the MCP altitude window to the MAP Altitude. You will problaly be able to get VNAV re-engaged after TO/GA is pushed but it will probably disengage again when the airplane reaches the MAP altitude and may never reengage again.It's normal for the autopilot to disengage during when TO/GA is pushed...no single pilot go-arounds in this airplane, only FD go-arounds.Good luck.Floyd