EGLL Director Answer...
 

I was Capt. on a 777-300ER today. LAM 3 Arr, 09L. Heading 265 after LAM, cleared down to 90. Then 80, with 27 track miles to run. Then, a couple of nice left vectors for a final intercept.

I was all set up for a nice CDA to final, 09L.

Now, if I remember the terminology correctly, we were 'Cleared to 3000 ft, intercept the glide slope, cleared the ILS approach, 09L.

Shortly thereafter, I was given clearance to descend to 2500 ft, intercept the glide slope, cleared the ILS approach, 09L.

I rolled final and intercepted, both localizer and G/S simultaneously, however; that was at about 3500 feet.

My question is this...Do you want me down at 3000 feet, then intercept the glidepath or is the CDA all the way through, the proper procedure. When done correctly, a CDA with both captures are really nice. It works slick, but to have descended down to the cleared altitude would have necessitated using either more flap or extending spoilers.

Whats your take on this, guys and gals from the Director chair?

Thanks!

In my opinion, keep the CDA going all the way down. If I need you to go down quicker than the glideslope (which is sometimes the case if we are establishing traffic on the other runway and it is passing close behind you) I will ask you to go down quicker.

I'm sure others will have other opinions though :)

Thanks for that!

Agreed, keep the CDA going as much as possible. There are several different altitude limits to separate you from low-level traffic/LC deps (westerlies)/heli-routes/to keep you inside CAS. Most controllers will give you as low as possible as soon as possible to both help you fly the CDA and negate the need for you to either level off or jump in requesting lower.

As stated, if your level is needed for separation from other traffic you'll probably get 'expedite descent' or 'vacate ..A now'

Regards.

Thats great...
 

Thats what I kind of thought. I wasn't sure if I was understanding the terminology quite correctly, so thats why I was asking. Its kind of fun to play with the airplane again, using some old math techniques and its working! The 777 has some nice features to help, but the brain still does better! I've always enjoyed flying into LHR. Kind of refreshing to have some professional controlling, aside from what some people say.

Keep up the great work, guys and gals.

Call me Mr. Thickie, but if you'd have intercepted the glide at 3000' as oppose to 2500', are you still not maintaining a CDA?

Ok Mr Thickie:ok:,

..at 10 miles, 3000' would still be on a CDA but 2500' wouldn't as there would be a portion of level flight until catching the glide at 8 miles so it depends on the range.

CDA...
 

Not actually. A CDA assumes a continuous descent, all the way through the initial maneuver for the approach...say passing LAM on the 265 heading, downwind for 09L. The director gives you 'track miles' to run, I confirm that with my FMS progress page. Having done that, have a look at my altitude and do some quick math, to determine if I'm going to be high or low on the slope intercept. The trick is to continue a nice, uninterrupted descent all the way through and intercept the localizer AND glideslope at the same time, without having to level off. Its efficent, economical and comfortable.

My question had been to query if the controllers actually wanted me AT 3000, THEN cleared for the approach. But it appears that my initial understanding is correct..which is continue with the CDA, but if the controller needed me at 3000 or 2500, THEN intercept, I would be so cleared to do so.

We can have all the fancy vertical path information, etc, but nothing beats using 3:1 on track miles to run and keep a running computation with the DME and progress page. Then, adjust the descent rate using V/S or speed brakes. One also has to comply with speed restrictions coming around the corner as well.
When it works out its a lot of fun and kind of breaks the monotony of fully automatic approaches and hustling down to an intercept altitiude and dragging the airplane in, on final approach. When it doesn't, it gives cause to think how to do it better next time!

...mind games in airplanes:ok:

777AV8R

It is definitely good fun to do CDA's, if the workload is under control. What kind of kit do you use to judge your profile in the CDA descent apart from the basic maths that we use?

We do CDA's into STN. STN director will tell us '25 miles rw 23, descend....' when we are typically at FL80. That is close to 3 deg (3 * ht) :ok: We then descend at 5* groundspeed all the way down and look at the DME when on the final vector for the LOC, then G/S. A second track mile call is usually given to us, more maths are done and VS adjusted as req'd. The VS is reduced to avoid level off and director give us a further descent to help us also.

We have a Flight Path Angle indicator on the HSI to set up a rough 3deg descent but it is too small to be accurate. (Not all modern a/c have this)

D

Fun with CDAs..
 

Right on 'Dumble'...
Well, I start the same way as you...8000 ft=24 miles to run.
Assuming you are on the downwind, start looking at the ILS DME, assuming that there is one..most airports do, for a while the position on the turn is almost like doing a DME arc and it is quite accurate for the CDA.

OK..so far, so good...as soon as 'vector voice' starts to turn us towards the final course...another glance at the DME...do the math...glance at the flight path vector. Your descent rate is similar to what I use..I take the first 2 numbers of the CAS (220K=22..divide those in half=11 put 00 behind it and get 1100 ft. per minute for a 3 degree path. It sounds like a lot of figuring, but I've been doing it for a while and I don't realize it any more...

So then...we start to do the speed reductions, which is why I usually descend slightly below the slope to account for a reduced descent rate somewhere in there...

And, if its all done just right...simultaneous 'green localizer , green g/s' on the FMA.

Of course, if the cockpit load isn't high, this works out really well. But, if we've got wx or like one of our ATC people said, if they need to change the descent rate for planning, things get messed up. But..its fun!

Good stuff guys but just remember that we usually only "Flight Check" (calibrate) Glideslopes to 10nm from touchdown....can't remember if LHR is a Calibrated to longer range, i'll check when i get a chance.

We had a situation a while ago at a major UK airport where controllers were routinely vectoring onto the glide at around 14 miles....It's now a requirement for us to check that one out to 15.

Unfortunately just because it's ok at 10 doesn't mean it will be at longer range...i've seen all sorts of weird things out there! :\

Cheers

Ah, haaa...
 

Right you are, Conjam..sooooo....Mr. Boeing gave us (some of us) a nice VNAV path vector...so, if the approach is 'coded', which they all are, there will be a crossing altitude at the FAF, which, if the aircraft has the feature of VNAV guidance, one can 'cheat' outside the 10 mile fix, because its mathematical.
..or..I could just engage VNAV until 10 miles, then capture the ILS all the while, making a CDA.
To be honest, I'm more apt to doing all of this fun CDA during reasonable weather, anyway.

Absolutely...we've been doing the same thing on our Falcon 20's for the last several years.

However, less "clever" aircraft might not have that ability.

How's the MLS working out anyway? :)

MLS?
 

Never used it and not in the data bases of our aircraft.

Off the top of my head, our GPs have a checked range of 15nm, but I stand to be corrected.

LHR LOC is calibrated to 25NM and GP to 15NM.

MLSs doing fine, going to be able to use them in LVPs imminently from what I remember.

Excellent, I was impressed with the MLS when I last flew it.

Thanks for the confirmation on the checked Glideslope range, been about 18 months since I did a Calibration at LHR...can't remember ALL the airfields :}

Cheers

777AV8R,

Sounds like we do it the same way maths wise. By the way, my 5* Groundspeed is the same as your way. (i.e. 5 *180kt = 900fpm). I work it out the same way as you anyway! :ok:

The director never says 'this is a CDA approach' That would help. The track miles given with the descent clearance is the cue to fly a CDA, but they are not always possible due to traffic and procedure design. Am I right? You can end up levelling of somewhere on the DW vector (at STN), but you can do the CDA from the next descent point.

Lhr Cda..
 

Actually, I believe that the LHR Jepp. briefing pages tell us that the CDA procedures are preferred, although not many of us take the time to have some fun see if we can drive ourselves onto the final approach course, all 'hooked up'.

Interesting discussion, though.. Now we've found out how far the ILSs in London have been tested to.

Thanks for the input!

You can be cleared for descent on the glidepath at LL from five thousand feet which ties with a range of 15nm.

CDAs are expected to be flown from minstack - usually 70 or 80 depending on high/low pressure. Hence the track miles given with descent below minstack. It's not practical in busy traffic from higher levels as minstack is used to ensure vertical separation between traffic off the stacks and traffic holding. And on easterlies off LAM/BIG you're sandwiched between departures and the BNN/OCK holds respectively.

That said, we will attempt to give continuous descent whenever possible.

Quick question - how does the 773ER cope with the 'standard' speeds on intermediate/final approach? 180 or 190 kts on base? 160 to 4 or 170 to 5, or does it depend on the weight on the day/SOPs?