Hello,

 

Can someone chime in and provide me with a "how to" or "tutorial" on flying an RNAV approach in the PMDG 737NGX?  Is it as easy selecting an RNAV approach within the FMC and then selecting the APP button prior to crossing the would be localizer?  I believe this procedure only works for IAN integrated approaches.  If IAN is not integrated then a LNAV/VNAV coupled approached is required correct?  With either case, how is speed controlled?  Does the speed need to be programmed into the FMC as well or can you select the SPD button and control it yourself?  Also, will the speed automatically "click off" once the wheels touch the ground like with a normal ILS approach? 

 

Thanks,

James

 

With either case, how is speed controlled?  Does the speed need to be programmed into the FMC as well or can you select the SPD button and control it yourself?  Also, will the speed automatically "click off" once the wheels touch the ground like with a normal ILS approach? 

 

I'll let others answer the rest, but just a head's up (if you care):

LNAV/VNAV is not an approved method to put you on the ground via automation.  That is to say, RNAV is not approved for autoland operations, though it's being evaluated.

 

In the sim, it's probably possible, but I figured I'd point it out.

 

Speed would likely be controlled via SPD INTV if still on VNAV, unless I'm mistaken.  You would take over the aircraft in full (APP or LNAV/VNAV off, A/T off) to land it, so speed at that point would be hands-on-throttle.

I typically manually fly all approaches by following the flight director to the ground.  I control speed with the A/T using SPD INTV but leave the A/T connected as it will shut off by itself once the mains touch the ground (I think this is only available on ILS approaches though...not sure).  Leaving the A/T connected ensures the aircraft maintains Vref + 5 through touchdown.  

 

I started flying RNAV approaches recently but don't seem to have the perfected just yet.  SPD INTV does not seem to be available with RNAV approaches unless I'm doing something wrong.   

 

Thanks,

James

Leaving the A/T connected ensures the aircraft maintains Vref + 5 through touchdown.

 

Typically (generic here - I'm sure operators and even the Boeing FCOM may have slight variances):

You want to be at VREF+5 all the way up to short final.

VREF at 50 over threshold

Let speed bleed from VREF as you flare to arrest descent rate

If you fly IAN LNAV/VNAV will control your path and speed based on criteria you put in approach ref page. It defaults to VREF + 5, but you can edit your gross weight, speed or wind correction value. when you are within 300 feet of DH you reset the MCP altutude to your go around altitude. Youre suppodes to be stable by 1000ft agl and diconnected by 500 usually and manualy fly to landing. If you press APP before your FAF it will guide you down but you will be about 50 ft above your glidepath. My rw pilot buddy says thats how the real bird runs and there is somewhere you can enter in weather related data to make that more accurate.

The FCOM explains it with diagrams but I still get confused about what is the difference between RNAV and IAN. It seems you can fly both if your approach is labeled RNAVXXX in the FMC.

Also I notice that some approaches say RNAV31Y and RNAV31Z for the same runway , they just have different waypoints, not sure what thats about

First, know thy buttons: SPD (don't touch it!) vs SPD INTV (use as necessary).

 

Here's how we typically do it: LNAV/VNAV on autopilot. When you break out, you can go to manual flight, but still you'd have the LNAV/VNAV for guidance.

 

As for speed, if you look at the legs, you can see what speeds the FMC thinks you should be at. If you follow those speeds with your configuration, you should be okay. Eg. If the jet says you should be at 200kts at FUZZY, you should probably at Flaps1, etc. The FMC will try to slow you down gradually and you need to keep configuring with it. You can force it to slow by simply adding flaps.

 

Some approaches can get fast due to tailwinds. If you're 10 out and the plane is on VNAV PATH, but it wants to speed up, simply drop the gear, and you can stay on speed. Or add enough flaps.

 

Notice you haven't needed to touch the SPD INTV button once. If you've put your wind correction in, the FMC knows what speeds you need. If you need to change it, you can rebug, or SPD INTV.

 

I think Boeing has you at Vref+wind until flaring and then you bleed of the steady state wind. So Vapp to ~20-30 feet and then bleed of the last 5+ knots in the flare.

 

And say it with me, "Autolands are not the norm, Autolands are not the norm, Autolands are not the norm. . . " and exhale.

Also I notice that some approaches say RNAV31Y and RNAV31Z for the same runway , they just have different waypoints, not sure what thats about

Not sure about RNAV, but ILS(rwy)Y and ILS(rwy)Z usually have DME distances based on either the ILS DME (one letter ie Y) and the other based on the Airfield VOR or Reference Point DME (other letter ie Z)

 

There is only 1 type of approach that is a precision approach with proper vertical guidance (ie not based on distance based decent profiles). It's the ILS. Everything else uses distance and/or position to derive vertical profile. Autoland is currently not approved for these (though you can get down to pretty low minimum altitudes on some of them).

 

And say it with me, "Autolands are not the norm, Autolands are not the norm, Autolands are not the norm. . . " and exhale.

 

I never do autolands...what's the fun in that?  I just want the flight director/HUGS for guidance when flying manually.

Skysurfer007 is flying a RNAV Approach (he is a real co-pilot on some german airline):

Here is a quick how to that I use in the real world in gulf streams. The G550 has a similar option like the IAN. We use the approach button on the RNAV approach.

First perform a SCAR check.

S-elect it from the FMS.

C-heck it against the chart. ensure the altitudes, course and glide path match.

A-ctivate the approach. check the map and FMS and make sure it looks right.

R-aim. check if you will have RAIM. this is a real world thing. Ensures you will have GPS coverage during the time of the approach.

 

There are a few ways to fly RNAV. You can shoot it in LNAV, LNAV/VNAV/DDA and IAN.

Big thing is to set your minimums for the type of RNAV you are flying.

LNAV-if you choose to use LNAV, you will have to set LNAV mins. You will also set the step down altitudes in the ALT window progressively. Autopilot use and vert speed is recommended. Autopilot use gives you the ability to closely monitor the approach and crossing restrictions. Biggest mistakes while shooting LNAV manually are missing altitudes and dipping below them.

LNAV/VNAV-sometimes will give you lower minimums. This is the preferred method because of the constant descent, but LNAV/dive and drive allows you to get to minimums sooner with a better chance of seeing the runway. Set minimums in the altitude window(the closest highest number you can set). At minimums the autopilot will level off and wait for you to initiate the go. If using DDA, add 50ft to the minimums(most aircraft), set dirt or missed approach alt when 300 ft below it,  and initiate the go at the minimums call.

IAN-fairly the same as LNAV/VNAV flown with a DDA. Big thing i've learned from real world in the 550 is to wait till the FAF is in front of you before arming it. For example lets say you are on a downwind to the IAF on a T procedure. The 550 has been known to get confused and start descending if you get close to the FAF. As a technique, we wait until we are past the FAF and on our way back to FAF before arming.

Quick crash info, hope I don't confuse you. I don't fly the NG real world but RNAV procedures are similar between aircraft. These procedures may not entirely match the NG.

Big thing is to check the training manual and follow that procedure.

Here is a quick how to that I use in the real world in gulf streams. The G550 has a similar option like the IAN. We use the approach button on the RNAV approach.

First perform a SCAR check.

S-elect it from the FMS.

C-heck it against the chart. ensure the altitudes, course and glide path match.

A-ctivate the approach. check the map and FMS and make sure it looks right.

R-aim. check if you will have RAIM. this is a real world thing. Ensures you will have GPS coverage during the time of the approach.

 

There are a few ways to fly RNAV. You can shoot it in LNAV, LNAV/VNAV/DDA and IAN.

Big thing is to set your minimums for the type of RNAV you are flying.

LNAV-if you choose to use LNAV, you will have to set LNAV mins. You will also set the step down altitudes in the ALT window progressively. Autopilot use and vert speed is recommended. Autopilot use gives you the ability to closely monitor the approach and crossing restrictions. Biggest mistakes while shooting LNAV manually are missing altitudes and dipping below them.

LNAV/VNAV-sometimes will give you lower minimums. This is the preferred method because of the constant descent, but LNAV/dive and drive allows you to get to minimums sooner with a better chance of seeing the runway. Set minimums in the altitude window(the closest highest number you can set). At minimums the autopilot will level off and wait for you to initiate the go. If using DDA, add 50ft to the minimums(most aircraft), set dirt or missed approach alt when 300 ft below it,  and initiate the go at the minimums call.

IAN-fairly the same as LNAV/VNAV flown with a DDA. Big thing i've learned from real world in the 550 is to wait till the FAF is in front of you before arming it. For example lets say you are on a downwind to the IAF on a T procedure. The 550 has been known to get confused and start descending if you get close to the FAF. As a technique, we wait until we are past the FAF and on our way back to FAF before arming.

Quick crash info, hope I don't confuse you. I don't fly the NG real world but RNAV procedures are similar between aircraft. These procedures may not entirely match the NG.

Big thing is to check the training manual and follow that procedure.

 

This is more or less how the RNAV procedures are flown in Airbus. Use of autopilot is recommended (or mandatory acc. SOP), just do not use AP2. LNAV mins are mandatory as well.

gnomegemini, on 13 Mar 2013 - 15:14, said:

Skysurfer007 is flying a RNAV Approach (he is a real co-pilot on some german airline):

What a great video.

Thought this was interesting , from the FCTM, page 222,

"When appropriate, make cold temperature altitude corrections by applying a correction from an approved table to the waypoint altitude constraints. The FMC obtains the GP angle displayed on the LEGS page from the navigation database. This GP angle is based on the standard atmosphere and is used by the FMC to calculate the VNAV path which is flown using a barometric reference. When OAT is lower than standard, true altitudes are lower than indicated altitudes. Therefore, if cold temperature altitude corrections are not made, the effective GP angle is lower than the value displayed on the LEGS page. When cold temperature altitude corrections are made, VNAV PTH operation and procedure tuning function normally; however, the airplane follows the higher of the glide path angle associated with the approach (if available) or the geometric path defined by the waypoint altitude constraints."

 

Eric W.

Thought this was interesting , from the FCTM, page 222,

"When appropriate, make cold temperature altitude corrections by applying a correction from an approved table to the waypoint altitude constraints. The FMC obtains the GP angle displayed on the LEGS page from the navigation database. This GP angle is based on the standard atmosphere and is used by the FMC to calculate the VNAV path which is flown using a barometric reference. When OAT is lower than standard, true altitudes are lower than indicated altitudes. Therefore, if cold temperature altitude corrections are not made, the effective GP angle is lower than the value displayed on the LEGS page. When cold temperature altitude corrections are made, VNAV PTH operation and procedure tuning function normally; however, the airplane follows the higher of the glide path angle associated with the approach (if available) or the geometric path defined by the waypoint altitude constraints."

 

Eric W.

Could cause an issue too. Good to let ATC know if you are using this correction. In my OPS, we apply it when below 0C. Some FMS system will apply it automatically. This is when the issues with ATC can happen. The approach plate will usually have a note in areas that cold weather altimeter settings have a big impact(mountains). In some areas you have to disable the auto enhanced adjustment in the FMS to prevent it from changing.

Thanks for the update G550!