Glideslope capture from above

[BigHairyBum]

I am on a fleet which has just changed its policy on what alt we set in the fcu (alt selector) whilst intercepting the g/s from above. We have gone from 1000` aal to above current a/c alt. Seems to me that this has nasty implications if the g/s is not armed first, ie, missed out because of high workload etc....

Yes, in an ideal world we would always intercept from on or underneath!

Would like to hear any other views and sops.

[LEM]

You should realise as early as possible that you'll need to descend further to capture the glide.

Request a lower altitude to ATC as soon as that becomes evident, and set it in the MCP.

Extend flaps and gear early in order to be able to dive when cleared to do so.

But you can do that only if later on you'll be able to check the glide with another fix.

Be very careful!
:ooh:

:ouch:

[BigHairyBum]

Thanks. It is the bit after the "descend with the glide" clearance I am talking about. When you are above it, with no further alt clearances. Do you wind the alt sel out the way or use it as further protection?

[OPEN CLB]

Altitude selection will depend a little on how high above glide you are.
Just slightly above glide, set something below as a safety net. Normally no problem.
Glideslope WELL below will require a higher V/S, resulting in a fairly early altitude capture-phase of the FD, not really getting you close to the GS. So altitude selection above your current level simply works better, avoiding nuisance action of the auto flight system. But your safety net is gone....

[BOAC]

BHB - why is your 'GP' not 'armed' in the situation you describe? If it is you have a 'safety net' and you WILL always g/a at the DA/DGH or earlier if things are not right, no?

You can either wind it down to ?DA? or put it 1000' above current and use v/s. As long as you are LOC established, you are safe down to the LOC only DA, but LEM has a better idea.:D

[Ojuka]

I am making the assumption from your posting that you haven't managed to get a "localiser established" call in on time due to ATC workload, so correct me if I am wrong there. In this case, and assuming (again) you are fairly close in eg 2000', personally I would take the glide anyway and descend from the assigned altitude. This gets you out of the "having to capture the glide from above" trap which is a pain. Many people will tell you that "this is not permitted in the UK, only in other european countries" which may be true, but then capturing the localiser from above is frowned upon also.

Every NATS radar controller I have spoken to, and my superiors have had the same feedback, is that they fully expect you to take the glideslope if they are busy with other r/t. OK, probably best not to do this from 4000' or 5000' where you have time to accept further assigned descents for glide capture, as ATC may be moving VFR traffic around underneath you. But close in, say 2000', I would never want to be in the late position of trying to capture from above.

I know this goes off the point of your thread and doesn't answer your question, but my operators have no such alt arming settings published for "capturing from above". All we would have in the window is the go around stop altitude.

Hope the assumptions I've made are not too far off the mark!

[LEM]

if the g/s is not armed first, ie, missed out because of high workload etc....

Maybe now I see what you mean...

First of all, you should always call "GLIDE ALIVE".

I once forgot to arm the glide (!), and since then I always call "GLIDE ALIVE AND ARMED".

If the scenario is the opposite, eg the controller forgets you and gets too busy, I go with Ojuka.

:ok:

[Intruder]

I am on a fleet which has just changed its policy on what alt we set in the fcu (alt selector) whilst intercepting the g/s from above. We have gone from 1000` aal to above current a/c alt.
How about the minimum altitude (per your policy) for a "stabilized approach" for an ILS? If you haven't intercepted by that altitude, you should go around...

FWIW, I have found that the 744 is very unlikely to intercept the G/S from above in a reasonable manner in any automatic mode. Hand-flying it down is the best way. FLCH or V/S may give useful Flight Director info, though.

[BigHairyBum]

Thank you for your thoughts. I agree that it is a situation which is best avoided, a go-around would be a better course of action for the more extreme cases. Better still an early clearance.

Perhaps it is worth mentioning that the background for this change of sop is to avoid the early alt capture as mentioned by Open Climb.:)

[Intruder]

Once you are cleared for the approach, on the LOC, and above G/S, your altitude setting will likely be at the previously cleared altitude. That altitude is no longer applicable, though, once established and cleared.

IMO, at that time you should consciously reset the MCP altitude; it could be either the Missed Approach Altitude, the MDA, or the min altitude for "Stabilized Approach" per your SOP. Our SOP has us set the Missed Approach altitude AFTER the G/S is captured, so I would recommend the "Stabilized Approach" altitude until the G/S is captured. That will give you a level-off command if you do not get to the G/S in time, as well as prevent the early altitude capture. Then you can make the go-around decision.

If the G/S is captured prior to min altitude, call "Set Missed Approach" and the Landing Checklist (if not already done).

[False Capture]

Perhaps it is worth mentioning that the background for this change of sop is to avoid the early alt capture as mentioned by Open Climb

Also, in the subsequent Go-Around following this early alt capture you don't have a go-around altitude selected. Bags of fun on RWY 18R at AMS with a 2000'AA and someone just airborne from RWY24.:eek:

I like the idea of selecting an altitude above your aircraft as opposed to 1000'AAL. To take it a step further it would be even better if you're able to select the GA altitude.

[Intruder]

I like the idea of selecting an altitude above your aircraft as opposed to 1000'AAL. To take it a step further it would be even better if you're able to select the GA altitude.

I disagree with a "random" altitude above the airplane. You have thus eliminated one of the warnings that you are too low for the conditions. Even the Missed Approach altitude setting is a bit premature...

"GA altitude" (i.e., DA) is reasonable IF you are in a reasonable configuration -- speedbrakes in, power up, V/S <1000 FPM. If you're still trying to achieve the G/S from above, that's too low!

The min SOP "stabilized approach" altitude gives you the margin of safety for virtually all unplanned situations -- at 1000' AAL, you can recover from any reasonable configuration. It carries the bonus of being "legal" if you are ever officially questioned.

[BOAC]

Intruder - your idea of the 'Stab' altitude setting - probably around 1000'AAL for most - has merit...but...
"GA altitude" (i.e., DA) is reasonable IF you are in a reasonable configuration -- speedbrakes in, power up, V/S <1000 FPM. If you're still trying to achieve the G/S from above, that's too low!
Is anyone else getting prickles on the back of their neck here? What on earth could ANY crew be doing at LOC only DA, without the necessary gear/flap/speedbrake/power settings AND STILL not on the GP - that needs an 'automatic' reminder to go-round? :eek: Surely they have already sailed through the first 'gate' for a stabilised approach WELL OUTSIDE the parameters and are now patently NOT going to achieve the next. The setting of LOC only DA is MERELY to enable descent without the annoying a/p habit (Boeing anyway) of early alt acquire. It is not a safety net. Likewise setting '0' or G/A altitude should NOT degrade 'safety'.

Whatever happened to airmanship, situation awareness, tightnening of the sphincter muscle?:D Things seem to have gone the wrong way to me! This particular aspect of the approach should not even be considered. There are plenty of other safeguards in the system first.

[BigHairyBum]

So who would have the chance to look up localiser MDA whilst all this is going on? Do you commit that to memory??

Just say it really wasn`t your day, if alt sel was set above a/c alt (new sop) and during the dive in vert speed to try and establish the glide the airbus has a momentary overspeed, the FD would revert to open climb. Fine, almost an automatic go-around you might say.... Except if you are at EHAM the missed approach alt may still be beneath you...

The only option I can see is to close the thrust levers and use vert speed or disconnect a/p and athr to sort out the mess. Not forgetting that in order to sequence the flight plan for a missed approach on a bus you need to select toga....

AAAAAAaaaaaarrrrggghhhhhh!!!!!

Will stop having nightmares now.:\

[BigHairyBum]

The nightmare gets worse!!

[BOAC]

Well, if it were to happen, my PERSONAL preference would be to set G/A alt, disconnect and fly manually:eek: and go-round if it looks dodgy or PNF calls for it. That does not need anything 'looking up':D Why this obsession with automatics? Mind you, I know nowt 'bout t'bus:D
Or at Stockholm Arlanda where a typical GA altitude is only 1500 ft ...and look what happened there!

[Intruder]

Is anyone else getting prickles on the back of their neck here? What on earth could ANY crew be doing at LOC only DA, without the necessary gear/flap/speedbrake/power settings AND STILL not on the GP - that needs an 'automatic' reminder to go-round?

I share your concern here. Anyone that desperate to get it on the ground may do so in a less-than-suitable manner.

However, I also believe that when automation in the form of alerts and reminders is available, it is ridiculous to disable them when you are scrambling to get from "outside normal parameters" to "in the box." A crew still attempting to intercept the G/S from above while approaching MDA or DA is already way outside the "safety box," and probably needs all the help and further reminders they can get BEFORE they bend metal!

Certainly there are degrees of deviation. If the crew consciously makes the "big play" for the G/S above 2000' AGL, keeps the V/S below 2000 FPM down to 1000' AAL, and is able to make the final adjustment with power applied and less than 1000 FPM after that, it may well be a reasonable approach. However, if the power is still at idle and/or the speedbrakes are still out below 1000', the ONLY sane option is a go-around! If it takes an automated alert to convince the crew of that fact, it's better than smearing rubber and aluminum all around the runway...

[BOAC]

Sorry, MJ - you are right - it was OSL. The low altitude lead me astray!!

Intruder - you say "If it takes an automated alert to convince the crew of that fact, it's better than smearing rubber and aluminum all around the runway" - full agreement, but what have we come to in 100 years of aviation when this sort of flying is even considered? I think that anyone who gets into situation (a) is probably going to ignore the alert at (b) anyway, so they would simply crash with extra noise:{

What are the training departments NOT doing, and where is 'PNF' in all this?

[LIMA OR ALPHA JUNK]

Tricky call. Older Boeings have no speed protection in V/S and the Airbus goes into open climb if too high a rate of V/S is selected.

V/S is probably the safest method with the go around altitude dialled in the window, but beware of alt captures and watch speed would be my suggestion.

[Clickclick]

Go around it self is a risky business.

10 hours flight, early morning landing, charge down to save 5 minutes is not worth it.


:}

[montys ex teaboy]

Need to be very careful.

The false G/S is there lurking at 6° and 1.5°

[False Capture]

Need to be very careful.

The false G/S is there lurking at 6° and 1.5°.


We fly Avro RJ100 into LCY where the glideslope is 5.5 degrees - most of our a/c being modified to carry-out steep approaches up to 6 degrees. The modification incorporates a 'STEEP APPROACH' button which when pressed (before the approach is commenced) de-sensitises the Mode 1 (Excessive Descent Rate) GPWS envelope. Despite the a/c being able to fly a steep approach we can still expect a "SINK RATE" followed by a "WHOOP WHOOP PULL UP" warning if the crew forget to press the steep approach button.

The GPWS will still protect your a/c from the excessive descent rate - should you fail to notice you're not on a 3 degree approach. If you're on a 6 degree glideslope (either false or approved steep approach) you have a hell of a battle slowing the a/c down (full airbrake is required on the BAe146/Avro RJ and final approach speed achieved before descending with the steep glideslope). The DME versus height/altitude/rad alt looks quite surreal and then there's the picture out of the window!:uhoh:

Do you "need to be very careful" about the false glideslope lurking at 6 degrees? The GPWS will protect you, but it will be embarrassing at the subsequent investigation following a very unstable approach(having missed all the signs) and then the inevitable "WHOOP WHOOP PULL UP" Go-Around. :sad: