Yes its for an autopilot , why does it convert an ac voltage into a negative dc voltage?

Because an autopilot needs to change the attitude of the airframe to compensate for an increase in lift to avoid a change in altitude or airspeed. That seems self evident to anyone with a rudimentary knowledge of flight mechanics.

 

Because an autopilot needs to change the attitude of the airframe to compensate for an increase in lift to avoid a change in altitude or airspeed. That seems self evident to anyone with a rudimentary knowledge of flight mechanics.

The airframe isnt the only thing that needs its attitude changing

 

...why does it convert an ac voltage into a negative dc voltage?

Switch the leads on your meter. Voilá, positive voltage.

 

The airframe isnt the only thing that needs its attitude changing

Apparently some schematics want to roll to an inverted attitude. What's next an Immelmann, or maybe a Lumchevak?

http://en.wikipedia.org/wiki/Immelmann_turn
http://www.youtube.com/watch?v=h4ykA7GR7Vo

 

The two op-amps with diodes in the feedback path have different gains for positive- versus negative-going inputs.
Simulate it and see: I'm not going to because I won't work any harder than you do.

 

The airframe isnt the only thing that needs its attitude changing

Spiteful comments disguised as humour are not appreciated. Papabravo indeed stated basic principles of flight mechanics, which should be known to every professional of the field. If you are not a professional of this field, then you should not be offended by that post.

As for the rest of the thread:
DexterMccoy, state clearly your intentions, regarding this circuit/thread. Do you do troubleshooting on it? Are you studying it? Provide context for your question.
In no way will AAC assume the role of a flight engineer/technician and try to repair a real-life aircraft circuit.

 

DexterMccoy, state clearly your intentions, regarding this circuit/thread. Do you do troubleshooting on it? Are you studying it?

Yes I'm troubleshooting the circuit and yes I'm studying it to learn how it works also

Where do you think I got these schematics from? you can't get them from the internet

Spiteful comments disguised as humour are not appreciated.

Really? it happen in all my threads daily and is appreciated on ACC

I don't go into other threads saying spiteful comments to other members on ACC, but it's ok for them to come into my threads and do it and spam my threads, hijack them. etc.

It's an unfair game

 

The two op-amps with diodes in the feedback path have different gains for positive- versus negative-going inputs.

Yes I know that, the diodes are called half wave clippers

My question was why does the circuit convert an AC input waveform/signal into a Negative DC signal on the output of the LIFT COMP

 

Most likely because the output goes to something else that expects the input to be negative. For more info ask the original designer.

 

Yes I'm troubleshooting the circuit and yes I'm studying it to learn how it works also

Where do you think I got these schematics from? you can't get them from the internet

We have done this before: I am going to close this thread, since it is not reasonable, safe or responsible for a collective, online mind to troubleshoot real-world aircraft problems.
We have done this before and we will do so in any future aircraft repair threads you may upload in the future.
Please, for your and our safety and well-being, do not make this kind of questions online.

Really? it happen in all my threads daily and is appreciated on ACC

I don't go into other threads saying spiteful comments to other members on ACC, but it's ok for them to come into my threads and do it and spam my threads, hijack them. etc.

It's an unfair game

You don't only have obligations in this community, you have rights too. If you find a comment/post which you find offensive, please report it and the moderating team will intervene, if we deem it inappropriate.