ILS Capture from Above False GS
Is there a current IRE out there....
There is no "choice" about intercepting ILS glidepath from above. Or, there was not when I was flying. It was a prohibited manoeuvre then and surely it still is. As I said, for good and sensible reasons it was considered dangerous practice.
Maybe a current IRE would care to quote chapter and verse.
Maybe a current IRE would care to quote chapter and verse.
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With our company SOP's we are NOT allowed to capture the GS from above. If it's looking to head that way then call go-around or ask for vectoring to come back around and try again. My opinion is that if you are kinda 'forced' to capture from above than you might be flying a rushed approach and seriously consider breaking it off to try again after a quick DODAR session. Nothing wrong with that IMHO.
I've had false LOC captures before (particulary at MAD) but no false glideslope's yet. ZRH is one of those places that tries to keep you high and fast as well. So that's in our descent briefing and what action to take if your mentioned scenario happens.
I've had false LOC captures before (particulary at MAD) but no false glideslope's yet. ZRH is one of those places that tries to keep you high and fast as well. So that's in our descent briefing and what action to take if your mentioned scenario happens.
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Descents for glide slope...
I cannot recall an incident of being on a false glide slope.
Above the glide slopè, that is. Many years, many countries.
One thing I always did, was to maintain a "normal profile" for descent.
That is to be at some 10,000' some 30 NM away from runway, at 250 KIAS...
To be at 6,000' some 20 NM away, start flaps, and be 3,000' some 6 NM away.
Then follow the glide slope, and x-check altitude at the OM or FAF.
And see that all that does not bring you below terrain.
No need to fly acrobatics to get to a glide slope.
xxx
I can recall intercepting GS for LAX 24R/25R some 70-80 NM out (profile).
However would first maintain the profile with my distance/height rule above.
Glide slope itself...? Would wait until some 10 DME to ARM the GS.
Looks like I did ok... Now retired and safely in my rocking chair...
xxx
Happy contrails
Above the glide slopè, that is. Many years, many countries.
One thing I always did, was to maintain a "normal profile" for descent.
That is to be at some 10,000' some 30 NM away from runway, at 250 KIAS...
To be at 6,000' some 20 NM away, start flaps, and be 3,000' some 6 NM away.
Then follow the glide slope, and x-check altitude at the OM or FAF.
And see that all that does not bring you below terrain.
No need to fly acrobatics to get to a glide slope.
xxx
I can recall intercepting GS for LAX 24R/25R some 70-80 NM out (profile).
However would first maintain the profile with my distance/height rule above.
Glide slope itself...? Would wait until some 10 DME to ARM the GS.
Looks like I did ok... Now retired and safely in my rocking chair...
xxx
Happy contrails
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One of my Boeing TREs told me it is ok to arm and capture a glideslope from above. I have discouraged this practice on the flight deck of every aeroplane I have flown for risk of false glideslope capture so begged to differ. He stood his ground saying it was not an unsafe practice.
Would any other trainers care to comment?
Would any other trainers care to comment?
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Antennas....
There is no perfect antenna. If it's supposed to be omnidirectional or directional or whatever....it's not perfect. Whatever antenna you have, it'll have undesired lobes. (In this case, we're talking about the
glide slope transmitter antenna.)
BelArgUSA is totally correct in his method. Not only will this circumvent
tracking one of these undesired lobes, it also usually keeps you from hitting mountains.
Your company's SOPs should address this issue. If not, the manufacturer of your aircraft should have a procedure for such a situation.
Fly Safe,
PantLoad
glide slope transmitter antenna.)
BelArgUSA is totally correct in his method. Not only will this circumvent
tracking one of these undesired lobes, it also usually keeps you from hitting mountains.
Your company's SOPs should address this issue. If not, the manufacturer of your aircraft should have a procedure for such a situation.
Fly Safe,
PantLoad
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Originally Posted by Greybeard
In the early 1970s, a DC-8 freighter captured a false LOC beam into Cold Harbor(?), Alaskan Aleutian chain, and hit a mountain.
Read the report and especially take a look at the map with the aircraft path compared to the transition route and approach. They weren't even in the same ballpark.
accident report
Cold Bay has a back course LOC approach so he may have read the course bar incorrectly?? Dunno
As to capturing G/S from above, for goodness sake fellas its not something to aim for all the time!!! But we all should now how to capture from above, what our particular Aircraft can/cannot do and still maintain a safe operation......
Hence my Airline trains for it in the Sim and where it happens during line training WHILST still maintaining SOP's with regard to stabilized criteria..
As to capturing G/S from above, for goodness sake fellas its not something to aim for all the time!!! But we all should now how to capture from above, what our particular Aircraft can/cannot do and still maintain a safe operation......
Hence my Airline trains for it in the Sim and where it happens during line training WHILST still maintaining SOP's with regard to stabilized criteria..
I've seen plenty of false LOC indications but not very many for the GS.
Our SOPs don't restrict whether you capture from above or below.
I'd have thought being on a 6 or 9deg glideslope would make the subsequent approach 'interesting' in terms of stability, unless your aircraft type was designed for it, like those that go into LCY (5.5deg).
As other posters have said, there are many ways to check the authenticity of a GS (RoD, height vs. distance, etc.). It doesn't strike me as particularly dangerous (unlike a false LOC), as it will be difficult to follow and actually give you increased terrain clearance. Probably not a good idea for sub-CAT-I Ops, though...
Our SOPs don't restrict whether you capture from above or below.
I'd have thought being on a 6 or 9deg glideslope would make the subsequent approach 'interesting' in terms of stability, unless your aircraft type was designed for it, like those that go into LCY (5.5deg).
As other posters have said, there are many ways to check the authenticity of a GS (RoD, height vs. distance, etc.). It doesn't strike me as particularly dangerous (unlike a false LOC), as it will be difficult to follow and actually give you increased terrain clearance. Probably not a good idea for sub-CAT-I Ops, though...
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false glides...
I have only seen them briefly when overflying the airport, in a very slow old turbo prop...
I have never been too worried about false glides, my descent planning take me right to the point where i intercept the correct G/S.
Also I would expect of most of my fellow pilots that before arming the autopilot/ FD system, they pause for one second and think are the parameters looking good... and then monitor the descent rate following the G/S.
Where I fly most G/S are normally only certified to 10 NM, which makes the math very simple... for your standard 3 DEG G/S expect to be just 3000 above the airport...
So yes I have intercepted "many" glides from above, and are "happy" to do...
I have only seen them briefly when overflying the airport, in a very slow old turbo prop...
I have never been too worried about false glides, my descent planning take me right to the point where i intercept the correct G/S.
Also I would expect of most of my fellow pilots that before arming the autopilot/ FD system, they pause for one second and think are the parameters looking good... and then monitor the descent rate following the G/S.
Where I fly most G/S are normally only certified to 10 NM, which makes the math very simple... for your standard 3 DEG G/S expect to be just 3000 above the airport...
So yes I have intercepted "many" glides from above, and are "happy" to do...
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Originally Posted by nitpicker330
Cold Bay has a back course LOC approach so he may have read the course bar incorrectly?? Dunno
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Capturing a false glide slope is not that rare once away from the relatively low lying ground most pilots are accustomed to. A classic example is Kabul... it's not uncommon to be vectored in from the very high MSAs surrounding KBL and given a late turn to intercept the localiser and a descent that will take you down onto the glide-slope.. (pull & roll) you need to be calculating your height above the a/f (5,800ft apx) so 16 miles out times 3 = 4,800 + 5,800 = 10,600 ft if you're on the correct lobe.. not that tricky unless you find yourself getting kicked around in a night-time blizzard, struggling to hear the checklist over an indecipherable ATC instruction and partial radio failure due to ground jamming of cell-phone signals.. if it's then end of a long 6 sector day then it can become quite challenging.
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Above Glide Slope
In today's world, ATC for whatever reason will from time to time keep you high till you find yourself above the GS. The Airbus FCOM directs the pilot to wind the alt alert above the aircraft altitude, (to prevent a level-off at ALT*), select 1500 fpm down, arm the ILS button and capture the slope. This works well if your ground speed is 140 kts.
Since the groundspeed and rate of descent are linked and affects each other, a good method to determine the rate down is to note the ground speed then add a one to the first two digits. e.g. GS 150, ROD 1600 FPM. GS 160, ROD 1700 FPM. GS 170, ROD 1800 fpm, NOT to exceed 2,000 fpm. The above table represents a 6 degree slope (a 3 degree angle to capture a 3 degree GS). It works very well indeed and takes the terror out of the exercise. Try it, you'll like it.
p.s. When capturing from above with the alt alert above the aircraft altitude, make darn sure the ILS / GS button is active (on), if not you'll fly through the GS. If you check the front of the Jepp approach manual you'll find the table of GS/angles/rate of descent. Research is king.
Since the groundspeed and rate of descent are linked and affects each other, a good method to determine the rate down is to note the ground speed then add a one to the first two digits. e.g. GS 150, ROD 1600 FPM. GS 160, ROD 1700 FPM. GS 170, ROD 1800 fpm, NOT to exceed 2,000 fpm. The above table represents a 6 degree slope (a 3 degree angle to capture a 3 degree GS). It works very well indeed and takes the terror out of the exercise. Try it, you'll like it.
p.s. When capturing from above with the alt alert above the aircraft altitude, make darn sure the ILS / GS button is active (on), if not you'll fly through the GS. If you check the front of the Jepp approach manual you'll find the table of GS/angles/rate of descent. Research is king.
Its no problem although not ideal to intercept from above, happens every now and then. Those occassions are probably a 50/50 split between ATC induced and Pilot induced. I find it best to just correct as early as possible and I just don't mess around. I arm the LOC and GS, lower the gear, select a V/S 0f -1800 fpm and get myself onto the GS as soon as possible. The times I have seen it become a total mess is were there is only a half ass effort to capture with the pilot then just continuing all the way down high on the slope just within stable limits, I have never understood why you don't just correct early and be done with it.
Yes Ollie wise words indeed, some Pilots leave it way too late to correct safely.
Its not something we aim for day today but we should all know the correct way to recover back down to the GS if needed. Hence my company gives the required info in out FCTM. As they do with Rejected Landings and Sidestep to parallel runways on approach.
And we practice in the Sim where things like this should be trained.
Its not something we aim for day today but we should all know the correct way to recover back down to the GS if needed. Hence my company gives the required info in out FCTM. As they do with Rejected Landings and Sidestep to parallel runways on approach.
And we practice in the Sim where things like this should be trained.
If you're doing a barometric RNAV intermediate approach to an ILS, there are often times when you will *have* to intercept the GS from above, due to temperature error, even though the altitude constraints at the intercept point are theoretically on the glideslope.
A good example of this is the RNAV transition to RW15 at GIG (SBGL).
In fact, any hard altitude restriction nominally coincident with an ILS GS will produce this scenario in >ISA temps. We tend not to notice because we are usually intercepting from below and GS capture takes precedence over ALT hold and FMC constraints, so the descent will start before you actually get to the waypoint/distance on the chart.
A good example of this is the RNAV transition to RW15 at GIG (SBGL).
In fact, any hard altitude restriction nominally coincident with an ILS GS will produce this scenario in >ISA temps. We tend not to notice because we are usually intercepting from below and GS capture takes precedence over ALT hold and FMC constraints, so the descent will start before you actually get to the waypoint/distance on the chart.
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Hey mods I just realized there are 2 basically identical threads running in here at the same time!!! Can you merge them please?
Originally Posted by Belarg
To be at 6,000' some 20 NM away, start flaps, and be 3,000' some 6 NM away.
9k at 30nm, 5k at 20nm, 3k at 10nm is good for me/GS.
Captured and flew the 6 degree glideslope during conversion onto DC9 51.
FD app, mod turbulence and icing on to 05 at GVA.
ROD wasn't always the clue as the alps are known for odd winds and shear -once lost 25 knots at 1200 ft on departure (with huge temp inversion), Heavy and rising terrain at night - not nice.
Outer marker check got it but initially thought it was an altimeter setting problem as flying QNH but had grown up on QFE.
Closed throttles, ordered FD off and intercepted the correct one.
broke cloud around 500ft.
Might sound hairy for the times but the company I was entering had abilities that did exist in my previous employer.(all of the training guys were ground attack/ fighter jet jockeys).
FD app, mod turbulence and icing on to 05 at GVA.
ROD wasn't always the clue as the alps are known for odd winds and shear -once lost 25 knots at 1200 ft on departure (with huge temp inversion), Heavy and rising terrain at night - not nice.
Outer marker check got it but initially thought it was an altimeter setting problem as flying QNH but had grown up on QFE.
Closed throttles, ordered FD off and intercepted the correct one.
broke cloud around 500ft.
Might sound hairy for the times but the company I was entering had abilities that did exist in my previous employer.(all of the training guys were ground attack/ fighter jet jockeys).
