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Old 01-31-2012, 09:07 AM
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Adlerdriver
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Originally Posted by sriram View Post
I have a doubt regarding CAT 3b landings, which is available in all major airports.
First, what is your "doubt" concerning CAT 3b?


Originally Posted by sriram View Post
1) What are the inputs the pilots gives other than employing flaps and landing gear before landing during an autoland.
Each aircraft capable of autoland has unique procedures and systems used during autoland. However, in basic terms, the pilot’s inputs are:
- Engage the aircraft autopilot/auto-throttles
- Follow air traffic control (ATC) instructions to put the aircraft on an intercept heading to the runway’s instrument landing system (ILS).
- Arm the aircraft’s approach mode to capture the localizer (for runway line-up) and glideslope (for vertical guidance to the runway).
- Configure the aircraft for landing (extending flaps/slats, landing gear, arming auto wheel brakes and auto ground spoilers)
Once these basic steps are complete, the aircraft will capture the ILS, fly to the runway and land. After landing, the pilot must engage the engine thrust reversers manually but wheel brakes should engage automatically.

Originally Posted by sriram View Post
2) When does the pilot take full control of the aircraft. (Is it after touchdown or before touchdown) in autoland. (I heard from a pilot that it is usually 2-3 seconds after touchdown.)
If the approach is a Cat-3 autoland, the pilot normally will take control during the landing roll once the aircraft is on the runway. He may choose to wait until the aircraft has slowed significantly, especially if the visibility is very low. Until he takes control (disengages the autopilot), the aircraft will track the center of the runway. So, 2-3 seconds after landing would probably be the earliest a pilot would take control. The latest would be after slowing to taxi speed and at a point where he must turn the aircraft off the runway. I’ve never timed the roll out of my aircraft but my guess would be 20-30 seconds.

Originally Posted by sriram View Post
3) What are the visibility conditions during which an autoland is done and how frequently are pilots instructed to do practice autolandings??
Each airline has a set of operational specifications that have been approved by regulators. So each airline’s requirements may be a little different depending on their opspecs and the capabilities of the various aircraft they operate.
Southwest airlines (a domestic US carrier) uses a heads-up-display (HUD) for their cat-3 approaches and their pilots manually fly the aircraft to landing without the use of autopilot or autoland. They must see the runway environment to land and thus, have higher visibility requirements than those carriers that use cat-3 autoland and don’t need to see the runway environment.

Normally a category 3 approach with autoland is required if the visibility is less than 1200 feet (350 meters). Many carriers require or at least recommend their pilot autoland if the visibility is less than 1600 feet (500 m). The lowest visibility the most capable aircraft is allowed to autoland is in is 300 feet (75 m).


Originally Posted by sriram View Post
4) What is the step by step procedure followed during autoland of large passenger airplanes such as Boeing 737, 747, 777 and Airbus 320, 330 and 380.
Of the aircraft you’ve listed, I have flown the 737 and A320. I have also flown the 757, 767 and MD-11/MD-10. Each aircraft has unique procedures, so it would really be impossible to give you step by step procedures. The general answer I provided in your #1 question is probably the best I can do regarding procedural steps of an autoland.

The only other procedural steps that are accomplished are specific duties followed by the Captain and Co-pilot during the approach. This involves ensuring the aircraft systems are providing the required guidance and redundancy to safely accomplish the autoland. There are specific points in the approach where certain system cues will indicate that the aircraft is operating properly. If at any point in the approach, these systems indicate a problem then the crew will abandon the approach.

Perhaps I’ll see if I answered your questions so far and you can follow up if you need to do so.

As far as history of autoland, I’m sure there is plenty of info on the internet. Here’s a link to a wiki entry:
http://en.wikipedia.org/wiki/Autoland
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