Tom,

 

I've got to find the wiring diagram.  If I remember correctly, part of the circuit is to provide reverse power to instantly stop the motor so it doesn't drift.  The magnetic reed switches that sense the up/down limits merely remove power much like the flap switch.  In order for the limit switch to fail, you would have had to hold the flap switch in the down position (unless it is not a snap-back switch).  Perhaps someone else can explain why the relay contacts would be arcing (stuck) and if that was the cause of the flap motor continuing.  There are ways to protect the contacts.  I've got to dig out the wiring diagram.

 

The flap pix are interesting as they indicate you were performing as a test pilot.  Your judicious use of power certainly saved the day.  The nose down pitch would have been increased along with extreme drag and probably no additional lift.  I think if you would have fire walled the throttle, control might have been compromised.  Side note: I use partial flaps (3 degrees from 160 to 140 KIAS and 10 degree take off flaps from 140 to 110 KIAS) to assist in slowing down and to keep the nose down at those slower speeds.

 

I'm glad the rods weren't bent.  I'm sure there would have been some skin damage if this had happened with the flaps going up - and I have no idea about what control issues would have been introduced - especially at slow speed and high AOA.

 

The trim tab looks like it is fully effective at cruise (tab deflected up to keep the nose trimmed down), but the air flow might not work as well when the tab is deflected down (elevator up) because of the disturbed airflow around the screws and over the hinge.  Maybe.  Of course, the tab could be extended aft if more control is needed.

 

It will be very interesting to learn where the CG is located.  Hmmmm, even minor equipment changes often require that the moment be recalculated and logged.  The airplane should have been re-weighed when the engine was changed.  LNC2's seem to benefit from a more forward CG, especially if they go faster than normal.  As such, it could have an effect on trim with the flaps extended that requires adjustment to trim effectiveness as mentioned above.  BTW, I have a 12 pound harmonic damper on my flywheel that moved my empty weight CG a bit forward of the recommended range.

 

Anyway, nice flying in that you were sensitive to the control distortions and carefully corrected them with power, etc. 

 

Scott Krueger

 

 

In response to Scott Krueger I have come up with a few answers to his well thought out questions.  If I could only be as articulate as he is. (My Holiday Inn Express stay is way over due)

** It would be nice to know why the relay got stuck (contacts fused?) so that the cause can be eliminated.

It seems that one of the contacts has some sort of buildup on it.  This buildup was half way across the intended gap of the contacts.  I can only assume this was from the relay arcing. 

** Did you later measure the actual flap angle since it was probably larger than 45 degrees if the motor reached its mechanical limit?  Such a deployment could explain the lesser effect of the elevator. 

Yes, sort of.  The book calls for 8 or 8.5 inches travel (can't remember) measured from the inner most point of the flap.  My flaps were at 11 inches.  Not sure what angle that is yet.  Pics below:
http://www.n54sg.com/stuff/flap01.jpg
http://www.n54sg.com/stuff/flap02.jpg

** Were the flap to bell crank push rods bent as the hole thru the rear spar might not have been big enough to handle such an extreme?

No  That does seem to be the limiting point of the travel, but the breaker popped before any damage was done.  In flight I was very concerned about flap limit speed.  VFE (Maximum Flap Extended Speed) is 120 MPH, assuming you only have 45 degrees of flaps extended.  One can only assume that more flaps equals a lower VFE.  Had I firewalled the throttle I think I would have found out what the true VFE is for that amount of flaps.  I do know they held up to about 100 MPH indicated.  Any slower and I lost pitch up.  I was to chicken to go any faster.  This was the main reason I DID NOT want to go around.

** Do you trim the elevator with a tab or spring load the whole elevator?  If by tab, it might not be as effective at slower speeds.

Tab, but a bit bigger than stock tab I think.  Pics below:
http://www.n54sg.com/stuff/trimtab01.jpg
http://www.n54sg.com/stuff/trimtab02.jpg

** What do you estimate as the location of the CG (I assume you still have that heavier engine up front)?  It might be too far forward when low on fuel. 

I have no idea...  And this worries me.  I was told this engine was +35lbs.  But I have also switched from the composite intake to the aluminum, adding a few lbs.   I am on the hunt for some scales and someone that knows how to use them.  At least get some idea of where the CG is.  The log books showing the engine install does not have that information.

Tom McNerney
www.N54SG.com

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