On a vacation in the Maldives my girlfriend and I were ferried in a de Havilland Twin Otter seaplane from the main island to the resort island where we were staying. This was my first water landing experience and I tell you these guys had a landing approach that basically just dived at the water at an angle that felt like 45 degrees and flared at the very last minute for a nice gentle landing. I guess a water landing allows this kind of approach?? Don’t know if it was standard procedure or they were just playing with us…the bastards:dubious:
Oh yes, and pilots who flew the F-8 say that when you first fly it you have the really weird feeling that you are going to stall out on take off when you “lower” the variable incidence. In fact, what happens is that the wing continues to fly at nearly the same angle of attack while the fuselage greatly increases its angle. This gives the first-time pilot the feeling that his climb angle has increased greatly and it is quite a striking experience.
OK, airline pilot checking in here.
The discussion so far has not put out any incorrect information, but I think I know what the OP was specifically asking about.
The main difference between an airliner approach to a busy airport and a small GA aircraft at the home field is the speed and the number of airplanes. The controllers try to get as many planes on the ground as quickly as possible, and this usually results in precise spacing and assigned speeds throught the approach. The most common clearance for an approach is something like “Maintain 180 to the marker, contact tower on…etc”. This means to maintain 180 knots until the Outer Marker on the ILS, and after that start slowing to your approach speed. The result is that we cross the marker at 180 knots, gear up and the flaps at 11 or 15. Once across the marker the power comes to idle, the flaps come to 28 or 40 and the gear comes down.
Thus the airplane is slowing down rapidly (feeling like you are being pushed forward in your seat) and as the flaps come out the pitch changes (higher lift, nose comes down), also making you feel like you are being pushed forward. The combination can sometimes feel like an anchor has been thrown out. Once the speed gets near approach speed, the power comes back up to maintain the new speed. The deceleration stops, and you feel like you’ve been pushed back in your seat (like when you release the brakes in your car after heavy braking). If we are late with applying the power and overshoot our approach speed you might feel some actual acceleration for a few seconds.
All of this is much more noticable when going into a busy airport where the spacing is tight. If the airport is not busy and we are the only ones on approach I’ll do a much more gradual slowdown, but you can always feel those flaps coming all the way down!
As for the Automatic Landings, yes our airplanes and crews can do them. How often are they done? Only when required by weather (a Cat III ILS down to 600 RVR MUST be an Autoland) or by the airplane (the airplane must do one every 90 days to remain certified). Why let the airplane land itself when I can do such a better job?
The systems have limitations, though: only 10 knots of crosswind, it cannot be used on an engine-out landing (except on the 777), and it can only be used on a Cat II or better ILS. Yes, the airplane will couple to and fly to landing a Cat I ILS, but the ILS itself is not certified for that - mainly because the airplane uses the localizer for runway alignment during touchdown and rollout. If the localizer suddencly goes screwy when flaring, you don’t want the airplane chasing it all over the place.
Hope this helps!
Okay, I have a couple of questions for you, please.
What rule prevents you from using autoland on a Category I ILS? I mean, I know there are lots of things in aviation that are not a good idea but still legal. Is a Category I autoland specifically prohibited by the FARs, or is it maybe a company rule?
My understanding is that a Category I ILS autoland is ok. It isn’t certified for autoland, but it isn’t prohibited either. Cat I minimums still apply, of course.
Thanks!
This is a complete hijack but …
On the subject of commercial airliners landing it seems to me that we all need to appreciate the great job that the air traffic controllers and the air crews do in maintaining air traffic.
For example, the volume of traffic at Los Angeles LAX is so great that Las Vegas, NV is in the traffic pattern! The timing and spacing of incoming flights has to start there, at least, or else things won’t work. In fact, it is my understanding that if a plane doesn’t have an assured spot in the landing sequence at LAX it isn’t allowed to take off from, say, New York.
My son lives in Crestline in the San Bernardino mountains, about 80 miles west of LAX. When I go home from his house at night down the north side of the mountains I can see the landing lights of as many as five or six planes in line coming from Las Vegas to LAX and there are more behind them that are to far away to see.
It isn’t necessary for the plane to speed up again for the sensation of being pushed forward to stop, it only need stop decelerating. Furthermore, your muscles may have been resisting the feeling of being pushed forward to the extent that when it stopped, you actually felt like you were being pushed back (like that kids game where you all press down on a chair for a minute, then try to lift it).
Yes, that describes exactly what I assumed I was experiencing.
Thank you for the detailed explanation.
And thanks to everyone else for their input.
-Photog
Joey G , now that you mention it, the restriction may be a company rule or it may an “air carrier” restrictive FAR.
From our Flight Manual Part I:
No elaboration on where the restriction comes from, and I don’t have a copy of the FARs handy. My guess would be that somewhere in the certification process of airplanes and crews, the FAA inserts something into our Ops Specs that says “Only do this on Cat II/III runways”.
BTW, I can’t BELIEVE that I actually got into my kitbag and looked up “Autoland” on my days off!
You can take the boy out of the airplane…
Thank you for looking it up.
Nah, it actually gave me something useful to do!
However, I think I will enjoy the rest of this beautiful spring day by…goofing off.