Autoland and CAT 3 landing
 

I have a doubt regarding CAT 3b landings, which is available in all major airports.

1) What are the inputs the pilots gives other than employing flaps and landing gear before landing during an autoland.

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.)

3) What are the visibility conditions during which an autoland is done and how frequently are pilots instructed to do practice autolandings??

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.

I am an Aerospace Engineering Student at IIT Kanpur, India and also request some easy to read references on the same regarding the history of this technology and when it was certified by FAA and the way ahead in CAT 3c Landings.

Sincerely,
Sriram

First, what is your "doubt" concerning CAT 3b?


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.

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.

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).


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

Alder, since you're an -11 guy, and I fly an airplane with no Cat 2/3/autoland capability of any sort, I got a question for you.

I was jumpseating on an FX MD-11 that did an autoland for currency. Light winds, beautiful morning. The landing itself was a thing of beauty...really nice and remarkably soft.

Is that normal? I would have thought autoland would be more of a "get it down, firmly and at the touchdown point so the numbers are valid" sort of thing. Or did I just catch it on a lucky day?

On the 747-400 during an autoland you know you're down when the speedbrakes come up. Hate to say it but day in day out it does better than I do.

Probably a combination of aircraft, conditions and a lucky day. In general, on the -11, I would say they're usually very good landings but not necessarily always perfect. I've never seen one land outside the touchdown zone, so the numbers should be valid.

The worst one I ever saw was on an A320 at ORD for a cat-3 update. The bottom just fell out at about 20 feet and we had to hide in the cockpit while the pax got off because HAL had a bad day.

+1..... and my experience is on the venerable Classic. I have done three.....two in pretty bad snow conditions...the other if very good conditions.... and ALL three where just like Wasp said.... you will know you are down when the speed brake comes up.... and all three well in the zone. Not bad for 40 year old technology.

Thanks, now I have an excuse for my next bad one. :)

Still trying to figure out why this is in the Aviation Law forum....

Thank you sir. That clarified most of my doubts. And was Lockheed Tristar the first to do such a landing as early as 1978. I couldn't get more authentic references from wiki. Could you help me out in tracing the history and evolution of this technology.

The first autoland was a B-247 in 1945. Vulcans were auto landing in 1960. The first in service airliner auto landing was in 1965, a BEA Trident at Heathrow.