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

Autoland wind limitations

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

Autoland wind limitations

Old 1st Oct 2023, 02:35
  #1 (permalink)  
Thread Starter
 
Join Date: Mar 2013
Location: 36,000'
Posts: 176
Likes: 0
Received 0 Likes on 0 Posts
Autoland wind limitations

Why do we have a head wind limitation for auto land ?
B737NG_Pilot is offline  
Old 1st Oct 2023, 03:42
  #2 (permalink)  
 
Join Date: Apr 2009
Location: Phoenix, AZ
Posts: 549
Received 15 Likes on 12 Posts
Originally Posted by B737NG_Pilot
Why do we have a head wind limitation for auto land ?
It's a very long time since I was involved with autoland flight test and certification. My recollection is that the systems I worked on were limited to the maximum values that were actually demonstrated during certification flight test. It's surprisingly hard to find suitable airports with the winds that one would like to have for certification demonstration.
EXDAC is offline  
Old 1st Oct 2023, 13:07
  #3 (permalink)  
 
Join Date: Oct 2006
Location: Ankh Morpork, DW
Posts: 646
Likes: 0
Received 0 Likes on 0 Posts
Probably the same reason we have a 20,000' flap limitation, "That's where we stopped testing, so that's your limit."
ImbracableCrunk is offline  
Old 1st Oct 2023, 13:59
  #4 (permalink)  
 
Join Date: Apr 2009
Location: Phoenix, AZ
Posts: 549
Received 15 Likes on 12 Posts
I said it had been a long time since I was involved with autoland development but I was curious enough to dig a bit into those distant memories. AC 120-28 is the "bible" for autoland systems development. The current version is D and it, and the related appendices, can be found here - https://www.faa.gov/regulations_poli...cumentid/22750

Autoland certification uses simulation to demonstrate performance under a huge range of conditions. The flight test program has to produce sufficient data to show that the performance of the aircraft matches the performance of the simulation. One of the inputs to the simulation is the wind model that is defined in Appendix 4. If my interpretation is correct that wind model does not produce headwinds that exceed about 26 kts.

It seems likely that the autoland wind limits are set by the wind model.

Last edited by EXDAC; 1st Oct 2023 at 21:24.
EXDAC is offline  
Old 1st Oct 2023, 14:27
  #5 (permalink)  
 
Join Date: Apr 2009
Location: Phoenix, AZ
Posts: 549
Received 15 Likes on 12 Posts
I found the Type Inspection Authorization for the DC-9 Series 80 autoland system. Included in the required conditions for the aircraft demonstration:

Conduct 100 autolands with the following wind component criteria:
1. Headwinds - At least 10% at 12.5 knots or higher with a minimum of 2 landings at 20 knots or higher.
2. Crosswinds - At least 10% at 7.5 knots or higher with a minimum of 2 landings at 12 knots or higher.
3. Tailwinds - At least 2 landings at 5 knots or higher.

It was finding these TIA required wind conditions that was difficult, not finding certification limit winds.
EXDAC is offline  
Old 2nd Oct 2023, 04:20
  #6 (permalink)  
Thread Starter
 
Join Date: Mar 2013
Location: 36,000'
Posts: 176
Likes: 0
Received 0 Likes on 0 Posts
Thank you EXDAC... Makes sense
B737NG_Pilot is offline  
Old 11th Oct 2023, 10:10
  #7 (permalink)  
 
Join Date: Jun 2014
Location: Village of Santo Poco
Posts: 847
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by B737NG_Pilot
Why do we have a head wind limitation for auto land ?
Who is "we" and what airplane are "we" flying this week?
Amadis of Gaul is offline  
Old 11th Oct 2023, 12:06
  #8 (permalink)  
 
Join Date: Jun 2001
Location: FNQ ... It's Permanent!
Posts: 4,263
Received 155 Likes on 78 Posts
Originally Posted by ImbracableCrunk
Probably the same reason we have a 20,000' flap limitation, "That's where we stopped testing, so that's your limit."
Mach number limitation.
Capt Fathom is online now  

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.