Max approach angle for CATII/III
Thread Starter
Joined: Aug 2000
Posts: 444
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From: Leeds
Max approach angle for CATII/III
Would anyone be so kind as to confirm the maximum permitted glideslope angle for both CATII and CATIII approaches.
My local field has a 3.5 degree approach due to highish ground 1.5nm from the threshold. This was established back in the 80s after a runway extension and although the ground is no lower (or higher) than it was then, I am led to believe the CAA have now approved a reduction in the g/s to allow the ILS to be upgraded to CATII.
My conclusion from this is that (a) CATII/III not approved at 3.5 degrees, (b) CATII approved at somewhere between 3.0 and 3.49 degrees, but not CATIII. Interested to know whether there is any definitive guidance on this and, if the above hypothesis is correct, why CATIII is limited to 3 degrees.
Thanks
My local field has a 3.5 degree approach due to highish ground 1.5nm from the threshold. This was established back in the 80s after a runway extension and although the ground is no lower (or higher) than it was then, I am led to believe the CAA have now approved a reduction in the g/s to allow the ILS to be upgraded to CATII.
My conclusion from this is that (a) CATII/III not approved at 3.5 degrees, (b) CATII approved at somewhere between 3.0 and 3.49 degrees, but not CATIII. Interested to know whether there is any definitive guidance on this and, if the above hypothesis is correct, why CATIII is limited to 3 degrees.
Thanks
Joined: May 2003
Posts: 198
Likes: 1
From: france
cat2 & 3 glide path angle
hello 682 amsl,
performance criteria for ils cat2 & cat3 are contained in icao document annex 10 & ecac document n° 17.
a summary of these requirements is as follows:
ils system is approved : beam bends within limits.
glide path angle between 2.5 & 3.25 degrees.
satisfactory power & transmission back-ups, with correct switch over time to standby system.
automatic signal-in-space monitoring.
the ils reference datum height is at least 49ft.
rwy width min. 45m & satisfactory length.
approach terrain profile checked & satisfactory.
in order to prevent electromagnetic interferences, establish ils critical area's etc... . ( cat2/3 holding positions, eg.)
performance criteria for ils cat2 & cat3 are contained in icao document annex 10 & ecac document n° 17.
a summary of these requirements is as follows:
ils system is approved : beam bends within limits.
glide path angle between 2.5 & 3.25 degrees.
satisfactory power & transmission back-ups, with correct switch over time to standby system.
automatic signal-in-space monitoring.
the ils reference datum height is at least 49ft.
rwy width min. 45m & satisfactory length.
approach terrain profile checked & satisfactory.
in order to prevent electromagnetic interferences, establish ils critical area's etc... . ( cat2/3 holding positions, eg.)
Joined: Nov 2005
Aviation Qualifications: PPL
Posts: 12,458
Likes: 368
From: Wildest Surrey
ICAO Doc 8168 para 3.5.6.1 sub para e):
glide path angle:
minimum 2.5 deg
optimum 3 deg
maximum 3.5 deg (3 deg for cat II/III operations)
And to add to Blackmail's list:
supplementary approach lighting and touchdown zone lighting.
glide path angle:
minimum 2.5 deg
optimum 3 deg
maximum 3.5 deg (3 deg for cat II/III operations)
And to add to Blackmail's list:
supplementary approach lighting and touchdown zone lighting.
Joined: Apr 2013
Posts: 10
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From: The Clacker
Max angle for cat 1 ILS?
I've seen 3.5 degrees quoted all over the place for maximum ILS angle, but Marseille 31R is 4.0 deg, and LCY is 5.5!
Are these special exemptions or what is the actual max angle? (cat 1 not cat 2/3)
Are these special exemptions or what is the actual max angle? (cat 1 not cat 2/3)
Joined: Jan 2000
Posts: 860
Likes: 0
From: FL410
Approach minima's need to be adjusted higher to take account of the increased vertical closure rate and proximity to ground in case of missed approach execution at minimums. Hence a steeper angle can be constructed if required due terrain for instance, but with higher then normal (200' AGL) minima
