Jump to content

Question of the day <----------------------


Recommended Posts

  • Aerosoft

This is one that does not have a absolute answer, but I got three airline pilots with in total over 50.000 hours logged to help me find the answer that makes most sense and is most complete.

Aircraft fly on autopilots, they even land automatically. Why don't these aircraft take-off automatically?

Link to comment
Share on other sites

Because for the case of a rejected or aborted Take Off the pilot has to respond as quick as possible to the situation , and as these situations may be very complex the pilot should be the last one (meaning to act as the first one here) to make a decision in that phase of flight.

Link to comment
Share on other sites

  • Developer

There is no guiding system to keep the aircraft on the runway. ILS don't be exact at this distance, GPS maybe could help in future, but at the moment not implemented with the needed solution.

Link to comment
Share on other sites

Because it is not necessary. For the take-off the pilot only has to monitor speeds etc, and pull the yoke. And when in the air the aircraft does the rest. For a landing it is necessary, as bad weather could trouble the sight really bad for the pilots, and so the pilots have to completely trust on the aircraft that's actually following a virtual pathway in any conditions.

Link to comment
Share on other sites

The autopilot doesnt know how much the plane weighs, So having an auto takeoff could result in too early rotation and end up in a stall, or rotation too late and run off runway.unsure.gif am i close?

Link to comment
Share on other sites

It´s not possible for any autopilot-logic to compensate the inertia of ground steering done by the tiller

and later by the rudder and stay exactly on the centerline. This has to be done manually (or pedually :D )

Even more because the surface marks and the conditions on runways are different. (Compare Punta Cana and Frankfurt :rolleyes: ).

Timo

Link to comment
Share on other sites

One might argue that some Airshoves already do feature a partial autopilot-on-take-off system for their FBW code. The system on certain A340's has active tailstrike prevention system that prevents over-rotation.

Before someone starts the usual Airshove-hard-versus-Boring-soft computer control, the system is also fitted to some Boeings...

However, to answer the question ( I assume this one is open to pilots as well as non-pilots? If not, please remove the post):

In both the Airbus A320 series and the Boeing 777, control laws are not fully activated until after the aircraft becomes airborne because the sensors used for feedback would sense a lot of vibration and spurious ‘noise’ during the take off roll and this could corrupt the accuracy of the data. Also there may be outside factors on the ground that are not considered by the flight laws, or directly sensed and acted upon by the system. There is no FBW command law for a runway incursion, or a pothole-induced 2g suspension compression for a brief moment...

Link to comment
Share on other sites

There is no reason to have an automated take-off. Autoland was designed to help pilots land the plane in low vis, and thus has an economical benefit for the airlines because it grately reduces the number of diversions. Now why would you actualy need automatic take off capability? And what happens in case of a freak occurence that both pilots become incapacitated after thay have initiated an automatic take-off in such way that they can not disengage it anymore? The plane flies to the skies without anyone in control? I just think that altough it would be possible to create such system it would probably be to costly for the airlines to implement and the airlines are doing just fine without it. I think if there was a real need for such a system the aviation world would have come up with it a long time ago. So my final conclusion is: there is probably no practical need for it.

rgds,

flyhigh

Link to comment
Share on other sites

There are some things that the autopilot cannot prevent and handle, like birds that can suddenly appear in the middle of the runway (even with anti-bird security) or anything like that.

Link to comment
Share on other sites

because it would be a lot more complicated to set-up auto-takeoff instead of just doing it yourself.

and actually you could say some aircraft use semi-auto takeoff, because the aircraft sets takeoff thrust automatically, so the pilot only need to keep the aircraft on the runway and pull back the stick.

Link to comment
Share on other sites

Localiser beacons get unstable close to the end of the runway.

Decisions to abort have to be taken in a slit second.

Pilot Unions / Plane designers won't allow the pilot to be automated out of the cockpit.

There are multiple factors which require monitoring on takeoff.

It's more flexible and easy for a pilot to take off.

Autothrottle is so advance all the pilot has to do is pull up and keep the airplane centered.

If an engine fails the pilot makes the decision to abort or not.

Autopilots can't sence foirengn objects on the runway.

Link to comment
Share on other sites

  • Aerosoft

There are some things that the autopilot cannot prevent and handle, like birds that can suddenly appear in the middle of the runway (even with anti-bird security) or anything like that.

And exactly how does this apply to take-offs and not landings? It's more or less accepted that landing is by far the most dangerous stage in any flight.

Link to comment
Share on other sites

  • Aerosoft

Localiser beacons get unstable close to the end of the runway.

Decisions to abort have to be taken in a slit second.

Pilot Unions / Plane designers won't allow the pilot to be automated out of the cockpit.

There are multiple factors which require monitoring on takeoff.

It's more flexible and easy for a pilot to take off.

Autothrottle is so advance all the pilot has to do is pull up and keep the airplane centered.

If an engine fails the pilot makes the decision to abort or not.

Autopilots can't sence foirengn objects on the runway.

But again. most of these things are the same on landing as they are in a take-off.

Link to comment
Share on other sites

  • Aerosoft

because it would be a lot more complicated to set-up auto-takeoff instead of just doing it yourself.

and actually you could say some aircraft use semi-auto takeoff, because the aircraft sets takeoff thrust automatically, so the pilot only need to keep the aircraft on the runway and pull back the stick.

I do not agree. landing or take-off most of the things the pilot needs to do are the same (different decisions to make, but very simular, go/nogo etc) and yet landings are fully automated and departures are not. In a landing the pilot just needs to keep the aircraft straight, flare and brake, right?

Link to comment
Share on other sites

  • Aerosoft

There is no reason to have an automated take-off. Autoland was designed to help pilots land the plane in low vis, and thus has an economical benefit for the airlines because it grately reduces the number of diversions. Now why would you actualy need automatic take off capability? And what happens in case of a freak occurence that both pilots become incapacitated after thay have initiated an automatic take-off in such way that they can not disengage it anymore? The plane flies to the skies without anyone in control? I just think that altough it would be possible to create such system it would probably be to costly for the airlines to implement and the airlines are doing just fine without it. I think if there was a real need for such a system the aviation world would have come up with it a long time ago. So my final conclusion is: there is probably no practical need for it.

rgds,

flyhigh

I think you got a few very good points. Yet the question was WHY is there no practical need for it?

The fact low vis landings can not be made manually is for sure a reason it was needed for landings.

Link to comment
Share on other sites

  • Aerosoft

There is no FBW command law for a runway incursion, or a pothole-induced 2g suspension compression for a brief moment...

Good points in your mail Snave, but these last two comments should also prevent a autoland/autobrake procedure. And clearly it's not.

Link to comment
Share on other sites

Along the lines of an earlier reply - there are precision landing aids, but no precision takeoff aids. The concern was aiding getting the plane on the ground in bad weather / visibility, so, technology has worked toward that end. There is one hands off take off - I believe - the F/A-18 is hands off when launching from a carrier (the only AC that is that way, I think).

Joe

Link to comment
Share on other sites

There is no practical need for it. As you said, the landing-part is the most dangerous part of the flight, and so pilots need to rely in their instruments so they can get the aircraft safely on the ground. This is a great benefit economically but also concerning safety. Regarding the take-off... If visibility would be so bad, then all flights would be canceled anyway. Preferably a delay of a few hours, than pilots not seeing the end of the runway and not being able to ainticipate on their decision. 'Go' or 'NO go'

Link to comment
Share on other sites

The pilot's Union lobbies against such technology because, after all - once you automate the take offs, what would you need pilots for, LOL? :D

Heck, even the computer could automate phrases like:

"Cabin crew please prepare for landing"

Also, I think people would be reluctant to fly a jetliner with no discernible cockpit with some humans in control!

Link to comment
Share on other sites

When auto landing you can't see the runway until the very last milisecond, when on takeoff you can see the runway even if it is only just 5-15M they can still see the centerline. You are able to follow it on takeoff because you are only a metre or two above it but on landing you are moving too fast to see the centerline or runway until your on the ground.

The auto pilot also doesn't control the wheel only the rudder which doesn't work at slow speeds.

(In Low Vis Conditions)

Link to comment
Share on other sites

Because:

Everything in the plane is already done automatically.

If you make the aircraft take off automatically, there is no need for a pilot anymore. Theoretically you can, but the human factor wouldn't match into this image...

Really, you guys; What would then happen with the "dream of flying" a plane?

Pilots should be aware that they are NOT flying the aircraft, they are not the ones dominating the aircraft! The computers are dominating the pilots!

This is a scary thought...but it is, the way it is!

And therefore the takeoff phase should not be given into the hands of "cyber-technologies"..

Link to comment
Share on other sites

I do not agree. landing or take-off most of the things the pilot needs to do are the same (different decisions to make, but very simular, go/nogo etc) and yet landings are fully automated and departures are not. In a landing the pilot just needs to keep the aircraft straight, flare and brake, right?

Autolands are almost never made, and only when needed due to EG low visibility. It's not as if an aircraft always lands itself, manual landings are more common. Autolanding is a feature introduced to be able to get to the ground in less than perfect WX circumstances.

Point is: During landing at low vis, you have to align the aircraft to something you aren't able to see. This is not possible, that's why we have autoland. When taking off, you can always see the runway. (if you can't, you just don't TO, for various reasons)

So it is not needed, so why spend any money on it?

Link to comment
Share on other sites

Because:

Everything in the plane is already done automatically.

If you make the aircraft take off automatically, there is no need for a pilot anymore. Theoretically you can, but the human factor wouldn't match into this image...

Really, you guys; What would then happen with the "dream of flying" a plane?

Pilots should be aware that they are NOT flying the aircraft, they are not the ones dominating the aircraft! The computers are dominating the pilots!

This is a scary thought...but it is, the way it is!

And therefore the takeoff phase should not be given into the hands of "cyber-technologies"..

Have you ever flown an airliner, or even an aircraft at all? I'm sorry blow your bell mate, but I think that what you are saying here is quite nonsense. I don't want to be impolite, but I hate it when people say flying airliners is just like being a system manager at an IT-company. It's just not true. However workload varies from aircraft to aircraft and between long- and shorthaul, pilots are not there just to watch the systems. They are there to fly the aircraft, and the systems are able to take over some workload while they still have to be supervised and controlled by the pilot.

Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. Privacy Policy & Terms of Use