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Aircraft Handling During Manual Reversion

smartt1982 From United Kingdom, joined Nov 2007, 212 posts, RR: 0
Posted (7 months 3 weeks 5 days 21 hours ago) and read 2943 times:

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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?

7 replies: All unread, jump to last

Roseflyer From United States of America, joined Feb 2004, 8737 posts, RR: 52
Reply 1, posted (7 months 3 weeks 5 days 20 hours ago) and read 2909 times:

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.

If you have never designed an airplane part before, let the real designers do the work!

yeelep From United States of America, joined Apr 2011, 526 posts, RR: 0
Reply 2, posted (7 months 3 weeks 5 days 20 hours ago) and read 2905 times:

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 From United States of America, joined Feb 2004, 8737 posts, RR: 52
Reply 3, posted (7 months 3 weeks 5 days 19 hours ago) and read 2863 times:

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.

If you have never designed an airplane part before, let the real designers do the work!

yeelep From United States of America, joined Apr 2011, 526 posts, RR: 0
Reply 4, posted (7 months 3 weeks 5 days 8 hours ago) and read 2753 times:

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 From United States of America, joined Aug 2000, 3952 posts, RR: 36
Reply 5, posted (7 months 3 weeks 5 days 7 hours ago) and read 2736 times:

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.

Chicks dig winglets.

Jetlagged From United Kingdom, joined Jan 2005, 2452 posts, RR: 17
Reply 6, posted (7 months 3 weeks 4 days 18 hours ago) and read 2637 times:

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.

The glass isn't half empty, or half full, it's twice as big as it needs to be.

wingscrubber From UK - England, joined Sep 2001, 834 posts, RR: 0
Reply 7, posted (7 months 3 weeks 3 days 23 hours ago) and read 2549 times:

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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