Guys, how about the MOD4 STAR for KSFO, it states that aircraft should expect clearance to cross CEDES intc at 11,000 ft, after that I experience steep descends toward the MEHTA (5000 ft) intc and start of the ILS to rnwys 28L/R? I even followed aircraft on flightaware on that approach Thanks for any clarification!

 

What is the distance between CEDES and MEHTA? What speed are you maintaining at CEDES? And how do the real approaches look like?

LOL well, first distance between CEDES and MEHTA is 18.5 nm, upon reaching CEDES I am at 11.000 and my speed is 240 kts, and then comes steeper descent towards MEHTA where I'm trying to arrive no faster than 210, and then slowing as I turn onto the ILS. In real life it seems they do cross CEDES at 11,000 and start descending to 5000 or 4000 where they turn towards the ILS, if this even makes sense what I wrote

Not easy to steeply descend and reduce speed at one time. Impossible I would say Try crossing CEDES with 220kt or even 210kt, once you cross it, spoilers up and descend to 5000ft to MEHTA.

&$()#*^&$#(*^&)* This sucks big time.

 

I've tried a flight to ENZV 5 times and just now a fligt to ENBR. They both have a waypoint with a FL100 restriction quite nearby and whatever I do, I can NOT get the plane to follow the STAR... First of all VNAV descends way too low at a certain point, something like 100 fpm. I took over control and used V/S a steep as possible without overspeeding and so I went down at 1300 fp, at 250 or so and that was already below 10.000 feet, so as hard as I could. But in the end I am way too high for an intercept of the ILS. And IF I make the intercept the plane is speeding down at 270 in order to chase the GS and I end up with a completely missed approach.

 

*)(@$)(*&@#)(*^ Two days and 6 flights wasted. Screw those STARs. I will go and fly somewhere where there are no such stupid restrictions. :angry: :angry: :angry:

You are using your full speed brake right?

 

Also if you want to maximise your descent rate outside of VNAV with a set speed that is what LVL CHG is for, easier than fooling around with V/S

I think you should stop looking at the ILS charts because I've never seen a 737 fly over my local airport to turn and fly the approach.

Look at the STAR charts, in the FMS choose you RWY and then using EGNX for e.g click ...forgot name it's on the right hand side, the first one is EMA and that would give you like your e.g ILS charts, wrong, click the STAR name. Then drop your speed right down if you see it's going to be asking to much. Look for the point where you think the trouble will start and in the FMC add a speed of around 200 before you see a big VS drop to reach your next way point. Think ahead big time.

GL

 

If you still have problems I will do you a FULL SID/STAR route with everything for you to try. A hard one it is.

&$()#*^&$#(*^&)* This sucks big time.

 

I've tried a flight to ENZV 5 times and just now a fligt to ENBR. They both have a waypoint with a FL100 restriction quite nearby and whatever I do, I can NOT get the plane to follow the STAR... First of all VNAV descends way too low at a certain point, something like 100 fpm. I took over control and used V/S a steep as possible without overspeeding and so I went down at 1300 fp, at 250 or so and that was already below 10.000 feet, so as hard as I could. But in the end I am way too high for an intercept of the ILS. And IF I make the intercept the plane is speeding down at 270 in order to chase the GS and I end up with a completely missed approach.

 

*)(@$)(*&@#)(*^ Two days and 6 flights wasted. Screw those STARs. I will go and fly somewhere where there are no such stupid restrictions. :angry: :angry: :angry:

Screen shots would be great. If there is a steep descent required and the jet is doing 100fpm, something isn't necessarily wrong. Check to see if you're still on path. Check to see what your Vertical Bearing is to the next fix with a hard altitude. Check to see that you are matching configurations with what the plane planned for.

 

I had an instructor tell me there are 3 important questions you should ask before writing up a problem in the logbook:

1. Is it me?
   
2. Is it me?
   
3. Is it me?
   

You are using your full speed brake right?

 

Also if you want to maximise your descent rate outside of VNAV with a set speed that is what LVL CHG is for, easier than fooling around with V/S

 

I used V/S because LVL CHG also didn't descent fast (in feet) enough...

 

I think you should stop looking at the ILS charts because I've never seen a 737 fly over my local airport to turn and fly the approach.

Look at the STAR charts, in the FMS choose you RWY and then using EGNX for e.g click ...forgot name it's on the right hand side, the first one is EMA and that would give you like your e.g ILS charts, wrong, click the STAR name. Then drop your speed right down if you see it's going to be asking to much. Look for the point where you think the trouble will start and in the FMC add a speed of around 200 before you see a big VS drop to reach your next way point. Think ahead big time.

GL

 

I don't look at ILS charts: I only use STARs (the ones that ProATC/X assigns me). Just flew to Heathrow, runway 27R, was assigned the TAWN3A STAR. Even after deleting EVERY restriction I just nearly made it. If I had kept the restriction I never would have.

 

Screen shots would be great. If there is a steep descent required and the jet is doing 100fpm, something isn't necessarily wrong. Check to see if you're still on path. Check to see what your Vertical Bearing is to the next fix with a hard altitude. Check to see that you are matching configurations with what the plane planned for.

 

I had an instructor tell me there are 3 important questions you should ask before writing up a problem in the logbook:

1. Is it me?
    
   
2. Is it me?
    
   
3. Is it me?
   

 

Yes, it must be me but I just don't know how you can fly a STAR by the book if even a STAR without all restrictions is just hardly possible. Like that STAR to EGLL I just described: I had to break every rule in order to make it to the runway...

 

Here is a screenshot from this afternoon but I doubt if it will help. I am already using V/S here. I started the descent BEFORE TOD bus as you (maybe) can see I am only at 11.000 while I should already be somewhere near 7000. It must be me indeed but what use is that knowledge...

 

 

My second suggestion is to make sure you're entering wind speeds on the DESC FORECAST page. In the States right now, we're seeing some pretty insane wind at altitude. If that is left uncompensated by the system, you're going to be off path when the wind speed changes drastically over the altitudes.

 

Kyle, where can I find the wind speeds to enter in the DESC FORECAST page?

Sorry to go off topic!

Everything is going fine, inbound from Malaga on a BAV tracked flight. ProATC has given me descent levels which are well within constraints....And then "Climb to FL 200" WT&!!!. I switched ProATC off and inserted my own STAR....safe landing at EGKK and another 2.5 hrs in the bank.

You are on VS but you only have -1000 FPM set.

 

You should be able to run -1600 or -1700 FPM set without undue use of the spoilers at constant speed or maybe a bit more.

 

VNAV will often take you above that rate of descent and Tutorial 2 talks about -3000 FPM, albeit as being uncomfortable and relating to a descent into Insbruck, which may not be typical.

Well, I just managed to land flying one of those '10.000 feet STARs' to ENZV. I did so by entering my own lower speeds in the FMC and using the speedbrake (almost all the time, which doesn't seem too realistic). The FMC had speeds like 280 and 260 planned above 10.000 and I changed them to 240 and the speeds at the 10.000 I changed to 220 (instead of 250). So getting a lower speed before the steep descent seems to help. I simply thought the FMC was clever enough to figure that out itself... apparently not. I also changed the speed of one of the last points from 220 to 180. Add to that the speedbrake... and I made it... Almost everything with VNAV too. It was a short test however and I used a flight where I already had descended to something like 17.000. Tomorrow I will see what happens when I do the entire flight from A to Z.

Kyle, where can I find the wind speeds to enter in the DESC FORECAST page?

Sorry to go off topic!

 

Fernando,

You can find them using the Flight Plan feature in ActiveSky (scroll down in the weather briefing window below the flight plan window and you'll see a table of them). If you don't use ActiveSky, use the source ActiveSky probably uses: http://aviationweather.gov/products/nws/all

 

Just look for the closest VOR to your T/D and use the winds at various altitudes listed. Look for big variations in speed or direction, and use those altitudes. If there aren't any, I just take even splits (FL240 to 300' would be FL180, 12000 and 6000).

Just FYI guys - the "Unable XXX KTS at XXXXX" type message happens because you're asking the airplane to violate the "monotonic path" concept. The FMC will not slow down, then speed back up, then slow down again etc. Same applies to altitudes too - it will not descend, then climb, then descend etc as part of a procedure. It assumes the speed and altitude are always going to increase (or be held constant for a period) on climbs and always decrease (or be held constant for a period) on descent.

 

Part of the reason this happens is because a lot of restrictions actually say something like "MAX 250 knots at XXXXX" on them, but our navdata format doesn't yet have the ability to code soft speed restrictions, so everything gets treated as a hard restriction and you get the monotonic violation at 250 because the airplane is already predicted to be below 250 due to the global 240/10000 restriction on the DES page. What you can do in these cases is look at the chart and then change the restriction by typing 250B/ (or whatever it actually is) and line selecting it over what's there. That'll change the restriction to a soft one and you shouldn't get the warning.

 

Kyle - you mentioned cost index being a cause for this - I don't believe that's accurate. I will have to check with Vangelis to verify with him, but in our aircraft CI isn't just a speed control like it is in some other addons - it works realistically and everything changes, including the calculation of the VNAV path angles and stuff - it should still create a valid path regardless of what the CI is. Changing the CI in flight to control speed isn't something pilots would really do either - you'd just speed intervene on the MCP or go to LVL CHG most likely.

 

That brings up another point that comes up constantly in real life too - if you don't like what the AP/FMC are doing with the path, take over manually with modes like LVL CHG, V/S (in a descent), HDG SEL etc. This happens ALL the time in real life - the FMC is not perfect even on the most advanced airplanes.

Fernando,

You can find them using the Flight Plan feature in ActiveSky (scroll down in the weather briefing window below the flight plan window and you'll see a table of them). If you don't use ActiveSky, use the source ActiveSky probably uses: http://aviationweath...roducts/nws/all

 

Just look for the closest VOR to your T/D and use the winds at various altitudes listed. Look for big variations in speed or direction, and use those altitudes. If there aren't any, I just take even splits (FL240 to 300' would be FL180, 12000 and 6000).

Thanks Kyle!