Max glideslope Cat 1 apr
Joined: May 2000
Posts: 1,021
Likes: 2
From: Glorious West Sussex
This is what wiki says... usual health warning applies.
The centerline of the glideslope signal is arranged to define a glideslope of approximately 3° above horizontal (ground level). The beam is 1.4° deep; 0.7° below the glideslope centerline and 0.7° above the glideslope centerline.
Joined: Mar 2008
Posts: 22
Likes: 0
From: Europe
@ Tyropicard: Probably not what initial poster was looking for...
I guess he is looking for the maximum permissible GS-deviation during approach (right?!)!
I was recently discussing the same issue with my captain. Our manual states the maximum allowed discrepancies for CAT II/III, but nothing mentioned about CAT I!
My pov: if you stay within the limitations, obey SOPs and are established according to the books, no problem to deviate from the glideslope (to fly above, NOT below the GS) in fair weather. Different thing under "real" Cat I conditions with RVR less than 800m...
Sorry - but i can´t give you a more precise answer, but looking forward to other comments!
Cheers
I guess he is looking for the maximum permissible GS-deviation during approach (right?!)!
I was recently discussing the same issue with my captain. Our manual states the maximum allowed discrepancies for CAT II/III, but nothing mentioned about CAT I!
My pov: if you stay within the limitations, obey SOPs and are established according to the books, no problem to deviate from the glideslope (to fly above, NOT below the GS) in fair weather. Different thing under "real" Cat I conditions with RVR less than 800m...
Sorry - but i can´t give you a more precise answer, but looking forward to other comments!
Cheers
Guest
Posts: n/a
Greetings,
In the cockpit we have behaviors, acquired during training, then after training, the brain remains in the learning mode for a while, so if at that stage you start doing "things your own way" then you replace the behavior acquired during training by this new one.
In other words, my advice fly the ILS CAT I as if the weather is bad, although it is CAVOK.
One dot below is max.
In the cockpit we have behaviors, acquired during training, then after training, the brain remains in the learning mode for a while, so if at that stage you start doing "things your own way" then you replace the behavior acquired during training by this new one.
In other words, my advice fly the ILS CAT I as if the weather is bad, although it is CAVOK.
One dot below is max.
Joined: Dec 2002
Posts: 2,775
Likes: 353
From: UK
The maximum ILS glide-slope angle is probably defined by an aircraft’s aerodynamic capability – e.g. shuttle; for commercial aircraft a steep approach certification.
The original LCY glideslope was 7.5 deg (for noise reasons), and because the only aircraft planned to use the airport was the Dash 7. This aircraft was certificated in the STOL category.
LCY was reduced to 5.5 deg to accommodate the limit of BAe146 / Avro RJ steep approach capabilities (although some 146/RJ’s have a 6 deg clearance)
With increasing angle at constant beam-width, the apparent GS sensitivity decreases (greater altitude deviation for the same GS indication), thus the beam-width may have to be narrowed. If so, then as far as the crew is concerned, they continue to fly within the normal limits to provide adequate obstacle clearance. However, crews should be aware that they may less time to response to a deviation due to the higher descent rate, i.e. with a GS deviation you have less time to recover back to the beam centre. Similar adjustments may be made to LOC instalations on short runways.
IIRC, planning for LCY jet operations considered the use of a Cat 2 quality glideslope installation (beam accuracy, stability, etc) so that a smaller obstacle clearance margin could be claimed to ease some for the problems of close in obstacles.
Also, with failing memory, Plymouth (UK) had a test / trial ILS installation at 7.5 deg, as a switchable alternative to the normal 3 deg beam.
The original LCY glideslope was 7.5 deg (for noise reasons), and because the only aircraft planned to use the airport was the Dash 7. This aircraft was certificated in the STOL category.
LCY was reduced to 5.5 deg to accommodate the limit of BAe146 / Avro RJ steep approach capabilities (although some 146/RJ’s have a 6 deg clearance)
With increasing angle at constant beam-width, the apparent GS sensitivity decreases (greater altitude deviation for the same GS indication), thus the beam-width may have to be narrowed. If so, then as far as the crew is concerned, they continue to fly within the normal limits to provide adequate obstacle clearance. However, crews should be aware that they may less time to response to a deviation due to the higher descent rate, i.e. with a GS deviation you have less time to recover back to the beam centre. Similar adjustments may be made to LOC instalations on short runways.
IIRC, planning for LCY jet operations considered the use of a Cat 2 quality glideslope installation (beam accuracy, stability, etc) so that a smaller obstacle clearance margin could be claimed to ease some for the problems of close in obstacles.
Also, with failing memory, Plymouth (UK) had a test / trial ILS installation at 7.5 deg, as a switchable alternative to the normal 3 deg beam.
Joined: Oct 2001
Posts: 3,832
Likes: 115
From: UK
Some 20 years or so ago, I spent two days with the FAA (on loan) in the Hatfield BAe146 simulator flying lots and lots of approaches into the likes of Aspen, Colorado and Casper, Wyoming. The object of the exercise was to establish the steepest safe approach possible.
If we got everything exactly right at the beginning of the approach, a 7 degree glideslope with everything hanging out at glideslope capture was possible but if you got high or fast then there was absolutely nothing you could do to correct.
It was decided that using a 7 degree slope on an everyday basis could be fraught with disaster.
I believe that was one of the reasons that a slope of 5.5 degrees was decided upon at LCY.
If we got everything exactly right at the beginning of the approach, a 7 degree glideslope with everything hanging out at glideslope capture was possible but if you got high or fast then there was absolutely nothing you could do to correct.
It was decided that using a 7 degree slope on an everyday basis could be fraught with disaster.
I believe that was one of the reasons that a slope of 5.5 degrees was decided upon at LCY.
Per Ardua ad Astraeus
Joined: Mar 2000
Posts: 18,575
Likes: 4
From: UK
Siam - you may want to look at http://www.pcpages.com/njanjua/gs_angles.htm
Joined: Jul 2008
Posts: 2
Likes: 0
From: ROME
Precision approach glide path angle:
1) minimum: 2.5°
2) optimum: 3.0°
3) maximum: 3.5° (3.0° for cat II/III operations).
Procedures involving non-standard glide path angles
Procedures involving glide paths greater than 3.5° or any angle when the nominal rate of descent exceeds 5 m/sec (1000 ft/min), are non-standard and subject to restrictions ("Height loss/altimeter margins"). They are normally restricted to specifically approved operators and aircraft, and are promulgated with appropriate aircraft and crew restrictions annotated on the approach chart.
1) minimum: 2.5°
2) optimum: 3.0°
3) maximum: 3.5° (3.0° for cat II/III operations).
Procedures involving non-standard glide path angles
Procedures involving glide paths greater than 3.5° or any angle when the nominal rate of descent exceeds 5 m/sec (1000 ft/min), are non-standard and subject to restrictions ("Height loss/altimeter margins"). They are normally restricted to specifically approved operators and aircraft, and are promulgated with appropriate aircraft and crew restrictions annotated on the approach chart.
Joined: Mar 2000
Posts: 8,571
Likes: 3
From: Arizona USA
One dot below is max
Remembering that most of these have minimum threshold crossing heights to avoid the main landing gear becoming rather close to the frangible bits of the approach lights....
