smartt1982
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Aircraft Handling During Manual Reversion

Mon Sep 24, 2012 5:59 pm

I was recently instructing a student on a type rating course on the 737 NG and part of the lesson was handling the aircraft during a manual reversion. I was surprised that the student was constantly pulsing or twitching at the control column with not much apparent effect on the aircraft. It was my understanding that although more force is needed you should still fly the airplane with smooth and positive inputs. The student who has done a lot of unofficial hours in a Challenger 300/737 sim from being a body on a number of type rating courses stated that an instructor had told him that this was the best method to control the airplane.

Any ideas?
 
roseflyer
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RE: Aircraft Handling During Manual Reversion

Mon Sep 24, 2012 6:52 pm

The only differences when flying with manual reversion is that higher control forces will be felt, standby rudder should be used to assist roll control and landing distance goes up due to degraded flare capability.

The pilot should not fly the airplane differently with manual reversion. Snapping and jerking the controls will have a jerking motion on the flight control surfaces. They can handle it, but it increases stress on the airplane. If you have already lost A and B hydraulic system, then I wouldn't think you would want to be jerking the airplane around. I see no reason why he should fly the airplane like that.
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yeelep
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RE: Aircraft Handling During Manual Reversion

Mon Sep 24, 2012 7:01 pm

There is also a deadband at neutral input that isn't there normally. Don't know if its really noticeable during manual reversion in flight, but its obvious when playing pilot during maintenance.

[Edited 2012-09-24 12:02:18]
 
roseflyer
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RE: Aircraft Handling During Manual Reversion

Mon Sep 24, 2012 8:15 pm

Quoting yeelep (Reply 2):
There is also a deadband at neutral input that isn't there normally. Don't know if its really noticeable during manual reversion in flight, but its obvious when playing pilot during maintenance.

Are you talking roll or pitch? Without an elevator feel computer, your pitch is going to feel off.
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yeelep
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RE: Aircraft Handling During Manual Reversion

Tue Sep 25, 2012 7:01 am

I primarily feel it in roll. With the yoke centered, it will take three degrees movement in either direction before the PCU input arms hit the mechanical stops on the actuator body and begin moving the ailerons. The same condition exists on the elevators, except the amount of control column movement is one degree each way.

Another reason for increased landing distance would be a decrease in braking ability due to the loss of spoilers.
 
XFSUgimpLB41X
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RE: Aircraft Handling During Manual Reversion

Tue Sep 25, 2012 7:34 am

He might have been "feeling" out the controls.

I tend to do this regardless of control law, and it actually proves to provide highly accurate control when done right as well as quick adaptation to abnormal control response.... at least in the real airplane. Your butt can feel energy change pretty dang well when cross checked with the instruments. A pulsing motion with the fingertips combined with normal longer phase control movements (what I do) is incredibly accurate.
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Jetlagged
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RE: Aircraft Handling During Manual Reversion

Tue Sep 25, 2012 8:40 pm

Quoting smartt1982 (Thread starter):
The student who has done a lot of unofficial hours in a Challenger 300/737 sim from being a body on a number of type rating courses stated that an instructor had told him that this was the best method to control the airplane.

It's possible the instructor meant for him to move the wheel rapidly through the servo valve deadband if he needed to reverse his input. Or maybe the instructor didn't properly understand how manual reversion works on a 737.

Quoting XFSUgimpLB41X (Reply 5):
A pulsing motion with the fingertips combined with normal longer phase control movements (what I do) is incredibly accurate.

This wouldn't work in manual reversion because of the large hysteresis deadband. Small pulses wouldn't move the surfaces.
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wingscrubber
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RE: Aircraft Handling During Manual Reversion

Wed Sep 26, 2012 3:58 pm

I remember talking to a pilot who suffered a total hydraulic failure on a manual-reversion aircraft I used to support (Non-FBW), he simply described it as being 'very difficult'. I imagine the pulsations occur because continuous deflection requires extra exertion from the pilot, it's just physically more fatiguing.
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