View Full Version : High On The Glideslope

29th Aug 2007, 15:05
What are the possible options in getting back to the glideslope of an ILS when you are about 500 ft high? :ugh:

29th Aug 2007, 15:24
If you were once on the glideslope and you deviated from it 500ft above you should have gone around because you have gone beyond half scale deflection of the glideslope bar. If ATC vectored you to the localiser above the glideslope, which does happen sometimes, you could level off and ask ATC to give you a 'box' pattern around the ILS to re-intercept several miles behind you. Also you could try increasing your rate of descent but whether or not that is a good idea depends on how far you are from the runway...its not really recommended.

By the way this isn't really the right forum for this question...it belongs in tech log or maybe flight training.

29th Aug 2007, 15:33
Thank you for your information. Will take note that it should be a flight training matter. :)

29th Aug 2007, 18:37
If you're quite a way out and MSA/Terrain isn't an issue (and making sure you don't bust your airline's SOP regarding max vertical speed below MSA): Gear Down, Speedbrakes and maybe some flap (obviously flap for drag is bad), maintain the speed to get the altitude off before the beam gets any narrower, then reduce when/if you make it back onto the glide. If it's all going pear-shaped get the go-around instructions sorted, and then press the buttons. Establish your bottom line early on.

29th Aug 2007, 19:22

The answer, IMHO, depends on 2 things:- what are your company SOPs and what is your altitude.

Assuming SOPs allow, @ 5000ft it's no big deal but @ 1000ft it can't be done safely.

Sir Donald
29th Aug 2007, 22:24
High at 500 feet,call going around,positive rate,gear up and try again.

29th Aug 2007, 23:44
If I'm working radar and I vector you in such a way so as to intercept the localizer above the glideslope, I fully expect you to tell me, at which time I'll break you out and we'll try it again. I'm paid to set you up properly and I take pride in it. Granted, it's been many years since I've had a problem with this. As you'd guess, one tends to get a feel for this after a few decades. However, I wouldn't ask for a "box pattern" (local vernacular?), but rather, just advise that I'm too high for the glideslope and I'd like to be taken out and vectored for another try.

Of course, one still gives the occasional vector across the localizer for "spacing" :O

29th Aug 2007, 23:58
Try asking for a box pattern anywhere other than US/UK or similar, and see what happens. A lot of places you can't even get a distance to run.

Recently listened to a Chinese crew try to advise a Korean ATC that he could only hold for 10 minutes before diversion to alternate.

By the time he diverted the ATCer was still trying to work out what it was all about.


Capn Bloggs
30th Aug 2007, 00:08
Provided you are established on the Localiser and are still above the G/S, set a lower altitude (still above the ground) say 1000ft AAL (the stabilised approach minimum altitude would be good), set V/S mode to the maximum allowed by your SOPs say 1500ft/min, get as much drag out as possible for the speed you're doing ie slats, flaps, gear and speedbrake if you are allowed and then sit back and see what happens, as you would if high on a LLZ approach. Of course, make doubly sure you have the G/S capture armed!

All bets are off at your company's Stabilised Approach point, naturally.

30th Aug 2007, 00:48
Gear Down, Speedbrakes and maybe some flap (obviously flap for drag is bad)
Actually, flap for drag is NOT "bad"! In some cases, more flaps are the only added drag available (e.g., 747 Classic, where speedbrakes cannot be used with flaps down)! While Boeing may preach that flaps should not be used for drag, they should really preach that they should not be used "primarily" for drag.

If you are on the ILS Localizer, you are likely well below your minimum clean speed (in a 747 that might be 240+). Gear or more flaps may be the only way to add more drag to get down to the G/S. A 747 technique to get down in a hurry in the terminal area is "Flaps 20, 220" (with the gear down), which gives a good rate of descent without building up a lot of airspeed. Once nearing the G/S, decel to 200 and set Flaps 25 to stabilize. Get it done by 1000' AGL, and you may avoid a go-around.

FWIW, we fly into several airports where intercepting from above G/S is very common; ICN and OSN stand out among them. As long as you anticipate and plan for it, it's not a real problem, if not ideal.

For the OP, 500' above G/S is a lot, unless you're "way out there"...

30th Aug 2007, 02:15
500 ft above GS IMC is way too high to salvage the approach unless you know exactly where you are. With no glide slope you could do like my friend and break out after the airport and have to look back at where you intended to land. Quite embarassing. Sometimes it is better to swollow your pride and go around so you can do it right next time. Unless you have DME it is hard to know how close you are to the runway without the glide slope.. I found out one day going into DFW if they don't protect the ILS the glide slope doesn't mean much either. A 747 parked by the glide slope transmitter and gave us a fly down command putting us way below the real glide slope. Tower said they didn't have to protect it if it was better than 800 and 2.

30th Aug 2007, 03:56
You should have a pretty good idea of your distance from the airport, via INS, DME, or FMS... Without those, how are you going to find the FAF if you do not have the appropriate VOR or NDB to triangulate your position?

If you are 500' high, and your normal rate of descent on the G/S is 800 FPM, and your max rate of descent is 2000 FPM down to 1000' AGL, you can get down to the GS in 25 seconds. At 150 KT, that would take just a little over a mile. At 1000' you are about 3.3 mi from touchdown, so you could technically do it from just under 5 mi (with a bit of slack for roundouts). If you intercept the LOC at 7 or 8 mi out (not unusual), there should be no problem making it down.

If you don't have DME, ATC should give you (or you should request) distance from the FAF when you intercept. You should then be able to make a decision to either continue or ask for another approach setup (or a delay vector).

30th Aug 2007, 10:57
set a lower altitude (still above the ground) say 1000ft AAL
Comes with a health warning this one, as it's possible you could go into Alt Capture before catching the glideslope, and make the problem worse.
On the Airbus, the usual method for capturing from above is to select an appropriate v/s, and select an altitude above your present level, and obviously arm the g/s.

30th Aug 2007, 15:36
And the false lobe? I haven't seen any mention...

30th Aug 2007, 18:36
Obviously, recovery other than a go-around should only be attempted in VMC with positive terrain and runway contact, or in IMC if you are absolutely sure about your position relative to the airfield and terrain. And then only if recovery is possible within the SOP boundaries w.r.t. max. V/S and stabilized approach criteria.

In general, speedbrakes are not very effective anymore once you reduce to intermediate and later to final approach airspeeds, and the use of speedbrakes is often restricted to lower flap settings. Since you want to recover the correct glidepath and configure for landing and reduce to final approach speed (be speed and thrust stabilized at least at 1000' or 500' AAL, depending on visual conditions and SOPs) the best strategy is to reduce speed fast (perhaps even flying level for a short while) while configuring to landing flaps and gear (i.e.: high drag configuration) and then try to recover the glidepath. Being configured on speed, drag and lift at least provides you with a bit more time and more spare mental capability to make a proper assessment whether glidepath recovery from that point onward is still feasible. If it's not, go around and fly another approach.

Now if you do it the other way around, i.e. first regaining the glidepath and then trying to reduce airspeed and configure the aircraft while staying on the glideslope, you increase your chances of being trapped in the "snowballing workload" scenarios described in this article (http://www.flightsafety.org/asw/dec06/asw_dec06_p28-33.pdf) ("Pressing the Approach", a highly recommended read!). Been there, done that, except for the smoking hole... things might have been different in less favourable conditions. :uhoh:

Another thing: make an explicit continue/go-around decision, inform your collegue about it, and ask if he/she agrees. It is quite possible that you think the situation is under control while your collegue is in fact tunneling.

Max Angle
30th Aug 2007, 19:28
Ask anyone who flies into Manchester on a regular basis, they will be very good at shedding 500ft+ as they try to get on to the glide.

31st Aug 2007, 06:39
Any ATCOs out there could you pls clarifiy:
I thought that the Intercept heading was supposed to position the aircraft on the Localiser with minimum 2 nm to Glideslope intercept.

2nd Sep 2007, 20:45
if it occurs after full on ILS you have two options:
1.if in VMC and you have RWY in sight you can continue the app, if 1000' AGL
2.if in IMC ,you have to go arround and to perform another app(ILS GS out ,VOR,NDB ) take in account GP failure

3rd Sep 2007, 01:04
to those that say you shouldnt decend on the glideslope due to false lobes, I agree but only to a point. What about ILS approaches into wacky places- Kabul international springs to mind, where every approach you recieve will be down a valley where the only certainty of "getting it in" is in decending on the glideslope. If you think 500' is high, I sugfgest you shoot an approach and see what 3000' high on the localiser decending off a talkdown from the co to intercept the glideslope is like! Would definately not do it on my IRT, but if going around is a bit difficult, a little MDR (300' per mile for 3 degree) will confirm whether you have captured the upper lobe or not. Oh, and the fact the upper lobe is usually found at twice the ILS glideslope, which means your approach is far steeper.

3rd Sep 2007, 08:19
Switch to localiser only proc and rebrief minimums - assuming, of course, that you are localiser established?

3rd Sep 2007, 08:52
Oh yes... don't you just luuuuuv Kabul ... seeing the G/S disappearing southward before being tuned toward the Loc... pulling off the pwr and seeing the descent rate plummeting.... hauling it around as the loc swings rapidly in and calculating like crazy the dme/height in your head and and adding 5800ft to the numberwhile trying to get thru the pre-landing checks, keeping below the gear speed talking to ATC and switching freq's... all at the end of a long day in the dark with the snow falling... and you just KNOW that those rocks are there beneath you...

3rd Sep 2007, 10:14
Roll and pull !

4th Sep 2007, 13:32
where I fly SOP is you must be stable by 1000' AGL or yo must go around.
For A319 to intercept from above you :
a) dial in altitude above current Alt.
b) select V/S -1500 fpm and pull
c) arm approach mode
d)when you get G/S* set missed approach Alt.


Captain Galactic
4th Sep 2007, 14:09
Drop the gear and flaps, if that doesn't work close the throttles and push the nose forward.Stabilised by 1000ft(IMC) of 500ft(VMC) then jobs a good 'un! if not go around.not rocket science is it...