Go Back  PPRuNe Forums > Flight Deck Forums > Tech Log
Reload this Page >

High glideslope interception altitude

Tech Log The very best in practical technical discussion on the web

High glideslope interception altitude

Old 20th Dec 2009, 11:22
  #1 (permalink)  
Thread Starter
 
Join Date: Oct 2009
Location: Kiyv
Age: 51
Posts: 15
Likes: 0
Received 0 Likes on 0 Posts
High glideslope interception altitude

Is it possible to start autopilot coupled ILS approach from altitude more than 2500 ft with non-ready data from radio altimeter (RA out of range)?

Thanks.
Andrew_Flora is offline  
Old 20th Dec 2009, 11:49
  #2 (permalink)  
 
Join Date: Feb 2006
Location: UK
Posts: 112
Likes: 0
Received 0 Likes on 0 Posts
yep...
though the approach might have some limitations...
ie normal GS range is 10 nm unless more is required...
plain-plane is offline  
Old 20th Dec 2009, 12:07
  #3 (permalink)  
Thread Starter
 
Join Date: Oct 2009
Location: Kiyv
Age: 51
Posts: 15
Likes: 0
Received 0 Likes on 0 Posts
I mean - Is an APP mode of AP operational while rad alt out of range?
(For example - with Collins ALT-4000 radio altimeter)
Andrew_Flora is offline  
Old 20th Dec 2009, 12:46
  #4 (permalink)  
 
Join Date: Aug 2006
Location: On the move
Posts: 940
Likes: 0
Received 0 Likes on 0 Posts
Nagative the AP will continue searching (flashing) until signal is obtained , yes if you keep the AP on engage APP and line it up it will continue the app as soon as intercept has occured
ab33t is offline  
Old 20th Dec 2009, 13:39
  #5 (permalink)  
 
Join Date: Jul 2006
Location: 'tween posts
Posts: 197
Likes: 0
Received 0 Likes on 0 Posts
false glideslope

Automation will pick up the glide, but with no valid RA cat2 and cat3 is not possible.as you fly along and once RA input gets validated it will upgrade to autoland capability. caution watch out for false glideslope intercept !!!
gearpins is offline  
Old 20th Dec 2009, 14:35
  #6 (permalink)  
 
Join Date: Dec 2002
Location: Where the Quaboag River flows, USA
Age: 71
Posts: 3,407
Received 3 Likes on 3 Posts
I have seen many guys try this and not successfully. KLAX has a long drawn out arrival that intercepts the G/S about 25 miles out, if you want to. But, using the VNAV profile works much better. The signal is too erratic beyond 10 nm.

Gf
galaxy flyer is online now  
Old 20th Dec 2009, 14:45
  #7 (permalink)  
Registered User **
 
Join Date: Mar 2009
Location: USA
Age: 49
Posts: 480
Likes: 0
Received 0 Likes on 0 Posts
Of course it all depends on the aircraft you are speaking of. Normally LOC allways captures first and will do so as long as it is within the beam, having said beam think of it as a weaker but wider signal at distance from the ground equiptment. GS capture will occur as the same, just expect more hunting at further distance.

Aircraft are usually set up to adjust gain to finer tolerances as you get closer to the threshold, this is usually done first for the loc on gs cap, sometimes marker beacons trigger stages and RA.

RA input to most autoland systems is not much more than a valid at altitudes but the aircraft w/o it will still fly the ils to the ground, just will not flare in it's absence.

Really any ILS coupled A/P is more or less cat III w/o flare.
muduckace is offline  
Old 20th Dec 2009, 18:31
  #8 (permalink)  
 
Join Date: May 2000
Location: Seattle
Posts: 3,195
Likes: 0
Received 0 Likes on 0 Posts
On the 744 GS will capture as long as LOC is captured. On the 742 in ILS mode, some will capture GS even before LOC; again, RadAlt altitude is not considered.
Intruder is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.