The Murphy Builders Site

Hi Bob & Brampton area Rebelers

Great meeting yesterday with a lot of good information.

Based on our discussions, I checked my elevator trim tab. I could see no
sign at all of any flexing or fatique. The paint was perfect here as
well. It does have 3 rivets - 1 into the front tab spar & 2 into a
fore/aft rib. Still, I am going to fab up a new piece to reinforce it.

It would really be helpful for MAM to publish this stuff on their site. It
was quite a shock to find this out this weekend. I am not sure I would
have been able to handle such an ordeal re: the flutter incident! Way to
go Bob.

I feel much the same way about the spring gear i.e. their approach has been
underwhelming but do not want to criticize. I do feel I went out of my way
to submit CAD drawings of all my tank improvements - many of which are
incorporated into their present design. In return, it would have been
quite easy to supply some of the basic information. It would not do their
reputation much good to lose a builder/pilot to a flutter incident.

I also checked my elevators & found the left one to be quite tight i.e. no
lateral movement but the right one does have some (1/16" approx). Again, a
little thought would have gone a long way to resolve this design
weakness. I will address this over the winter as it is not serious but
left on its own, it will not get better no matter how much wishing I do.

If everyone works together we can make this a truly great aircraft design
with outstanding operational histories.

Just my thoughts

Brian #328R




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----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Monday, September 15, 2003 11:11 PM
Subject: Sunday Meeting

Hi Bob & Brampton area Rebelers

Great meeting yesterday with a lot of good information.

snip

We need to find some way of sharing this good information with the rest of
the list!



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You are right Lonnie and once again my thanks to Bob and Anna P. for
hosting these meetings. They do enough so I'll try to summarize a bit.

Well you know about the trim tab horn ripping out of the trim tab.
Result was large, violent, and life threatening elevator oscillations.
Elevator would move up, tab would violently force it back down and vica
versa. This is a large and powerful trim tab and it is difficult to
control an aircraft if you can't hold onto the stick... The tab is
probably large to enable getting the aircraft onto the ground with trim
if the elevator cables were to become disconnected. The reinforcing
bracket that was applied in bulletin 080520Reb to the vertical stab
rudder post was apparently cracked in half during this.

The thing is though, the horn that ripped out was not fastened according
to the manual, nor was the bulletin calling for a doubled horn
completed. As I understand it the original builder somply riveted the
horn to the twenty thou skin so it is no surprise that it failed. It was
not rivetted to a rib and the forward rivet did not even pick up the
spar in the original installation. MAM's design is certainly not at
fault here in any way. I can't imagine why they don't have the horn
doubling bulletin on the web site though.

Someone made a comment that they put a circuit breaker on their SR
because a runaway trim was uncontrollable. I would bet money that their
is little chance of getting a breaker pulled before full trim deflection
if the trim runs away. IMO there should be mechanical stops to limit
deflection if the aircraft is uncontrollable with full trim deflection.

As an aside, commercial aircraft often require two switches to be
activated to move a trim device that could destroy the aircraft.
Typically two switches side by side. Both must be activated together and
a short or failure in one switch can't move the trim. You sometimes see
switches that are not even rated for DC current in homebuilts and one
failure mode for these switches is contact welding or sticking. Anyway
two switches won't help if the short causing the runaway is in the servo
or wiring after the switch of course. This is way outside the scope of a
Rebel, but another thing you see is sensors that prevent trim movement
opposite to stick force. ie up trim is automatically deactivated if you
are pushing forward on the stick.

It was also suggested that pogs or nylon washers should be used to make
sure the elvators have no side to side movement. An example of badly
worn elevator bearings in 200 hours was given. It was suggested that
side to side vibration of the elevator may have contributed to the wear
by setting up an in an out sawing motion. One gentleman mentioned that
he had used some of MAM's bronze bushings for these bearings. Another
mentioned no problems at all on a high hour rotax powered machine that
that had the bearings regularly oiled.

Don't recall anything else but I had to leave the meeting early.

Ken


Lonnie Benson wrote:

----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Monday, September 15, 2003 11:11 PM
Subject: Sunday Meeting

Hi Bob & Brampton area Rebelers

Great meeting yesterday with a lot of good information.

snip

We need to find some way of sharing this good information with the rest of
the list!

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Hi Ken & Bob

I assume that Bob's Rebel did not have the SB 080520 applied to this
aircraft. The SB tells us that we should have 2 of these angle pieces
riveted back to back to form an inverted 'T' shape per your earlier
post. If this were the case then the new piece would have 1 rivet into the
forward spar of the trim tab & the other 1 or 2 rivets into the skin
only. This would not double the strength or stiffness but would most
definitely be an improvement over the existing set up.

It is odd that on my airplane, there is no evidence of fatigue
cracking. Or is that what would happen, it would just suddenly fail
when a certain load is generated on the control surfaces. If that is the
case, all Rebels should be grounded until the fix is in place.

Brian #328R


RebAt 09:09 AM 9/16/2003 -0400, you wrote:

You are right Lonnie and once again my thanks to Bob and Anna P. for
hosting these meetings. They do enough so I'll try to summarize a bit.

Well you know about the trim tab horn ripping out of the trim tab.
Result was large, violent, and life threatening elevator oscillations.
Elevator would move up, tab would violently force it back down and vica
versa. This is a large and powerful trim tab and it is difficult to
control an aircraft if you can't hold onto the stick... The tab is
probably large to enable getting the aircraft onto the ground with trim
if the elevator cables were to become disconnected. The reinforcing
bracket that was applied in bulletin 080520Reb to the vertical stab
rudder post was apparently cracked in half during this.

The thing is though, the horn that ripped out was not fastened according
to the manual, nor was the bulletin calling for a doubled horn
completed. As I understand it the original builder somply riveted the
horn to the twenty thou skin so it is no surprise that it failed. It was
not rivetted to a rib and the forward rivet did not even pick up the
spar in the original installation. MAM's design is certainly not at
fault here in any way. I can't imagine why they don't have the horn
doubling bulletin on the web site though.

Someone made a comment that they put a circuit breaker on their SR
because a runaway trim was uncontrollable. I would bet money that their
is little chance of getting a breaker pulled before full trim deflection
if the trim runs away. IMO there should be mechanical stops to limit
deflection if the aircraft is uncontrollable with full trim deflection.

As an aside, commercial aircraft often require two switches to be
activated to move a trim device that could destroy the aircraft.
Typically two switches side by side. Both must be activated together and
a short or failure in one switch can't move the trim. You sometimes see
switches that are not even rated for DC current in homebuilts and one
failure mode for these switches is contact welding or sticking. Anyway
two switches won't help if the short causing the runaway is in the servo
or wiring after the switch of course. This is way outside the scope of a
Rebel, but another thing you see is sensors that prevent trim movement
opposite to stick force. ie up trim is automatically deactivated if you
are pushing forward on the stick.

It was also suggested that pogs or nylon washers should be used to make
sure the elvators have no side to side movement. An example of badly
worn elevator bearings in 200 hours was given. It was suggested that
side to side vibration of the elevator may have contributed to the wear
by setting up an in an out sawing motion. One gentleman mentioned that
he had used some of MAM's bronze bushings for these bearings. Another
mentioned no problems at all on a high hour rotax powered machine that
that had the bearings regularly oiled.

Don't recall anything else but I had to leave the meeting early.

Ken


Lonnie Benson wrote:

----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Monday, September 15, 2003 11:11 PM
Subject: Sunday Meeting

Hi Bob & Brampton area Rebelers

Great meeting yesterday with a lot of good information.

snip

We need to find some way of sharing this good information with the rest of
the list!

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Brian, this piece will not fail suddenly and will take time to work the
rivets loose and or crack things, as I have shown in the pics I posted to
the archives. As you can see in the picture my rivets were loose, the skin
was cracked and the front tab spar flange was cracked for over an inch. It
was still holding in and doing it's job in this state. It's just a neglected
place for pre-flight inspections, when the airplane is on wheels! To check
for fatigue just push down on your tab and watch to see if the skin lifts at
the front spar of the trim tab right in front of the tab horn. With Howard's
it has finally showed up as what looks like a line of mold between the skin
and spar in this location and will be one of the first fall annual items to
be tackled. This isn't a new problem and not the first time it's been
discussed here. Everyone just needs to keep a good eye on what they are
flying and remember areas like this get punished at flyins etc with PARENTS
having to touch and feel our tin machines!

Cheers,
Wayne



----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Tuesday, September 16, 2003 10:41 PM
Subject: Re: Sunday Meeting

Hi Ken & Bob

I assume that Bob's Rebel did not have the SB 080520 applied to this
aircraft. The SB tells us that we should have 2 of these angle pieces
riveted back to back to form an inverted 'T' shape per your earlier
post. If this were the case then the new piece would have 1 rivet into

the

forward spar of the trim tab & the other 1 or 2 rivets into the skin
only. This would not double the strength or stiffness but would most
definitely be an improvement over the existing set up.

It is odd that on my airplane, there is no evidence of fatigue
cracking. Or is that what would happen, it would just suddenly fail
when a certain load is generated on the control surfaces. If that is the
case, all Rebels should be grounded until the fix is in place.

Brian #328R


RebAt 09:09 AM 9/16/2003 -0400, you wrote:

You are right Lonnie and once again my thanks to Bob and Anna P. for
hosting these meetings. They do enough so I'll try to summarize a bit.

Well you know about the trim tab horn ripping out of the trim tab.
Result was large, violent, and life threatening elevator oscillations.
Elevator would move up, tab would violently force it back down and vica
versa. This is a large and powerful trim tab and it is difficult to
control an aircraft if you can't hold onto the stick... The tab is
probably large to enable getting the aircraft onto the ground with trim
if the elevator cables were to become disconnected. The reinforcing
bracket that was applied in bulletin 080520Reb to the vertical stab
rudder post was apparently cracked in half during this.

The thing is though, the horn that ripped out was not fastened according
to the manual, nor was the bulletin calling for a doubled horn
completed. As I understand it the original builder somply riveted the
horn to the twenty thou skin so it is no surprise that it failed. It was
not rivetted to a rib and the forward rivet did not even pick up the
spar in the original installation. MAM's design is certainly not at
fault here in any way. I can't imagine why they don't have the horn
doubling bulletin on the web site though.

Someone made a comment that they put a circuit breaker on their SR
because a runaway trim was uncontrollable. I would bet money that their
is little chance of getting a breaker pulled before full trim deflection
if the trim runs away. IMO there should be mechanical stops to limit
deflection if the aircraft is uncontrollable with full trim deflection.

As an aside, commercial aircraft often require two switches to be
activated to move a trim device that could destroy the aircraft.
Typically two switches side by side. Both must be activated together and
a short or failure in one switch can't move the trim. You sometimes see
switches that are not even rated for DC current in homebuilts and one
failure mode for these switches is contact welding or sticking. Anyway
two switches won't help if the short causing the runaway is in the servo
or wiring after the switch of course. This is way outside the scope of a
Rebel, but another thing you see is sensors that prevent trim movement
opposite to stick force. ie up trim is automatically deactivated if you
are pushing forward on the stick.

It was also suggested that pogs or nylon washers should be used to make
sure the elvators have no side to side movement. An example of badly
worn elevator bearings in 200 hours was given. It was suggested that
side to side vibration of the elevator may have contributed to the wear
by setting up an in an out sawing motion. One gentleman mentioned that
he had used some of MAM's bronze bushings for these bearings. Another
mentioned no problems at all on a high hour rotax powered machine that
that had the bearings regularly oiled.

Don't recall anything else but I had to leave the meeting early.

Ken


Lonnie Benson wrote:

----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Monday, September 15, 2003 11:11 PM
Subject: Sunday Meeting


snip

We need to find some way of sharing this good information with the

rest of

the list!

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Ken, I appreciate your effort to keep us outlanders in the loop.

----- Original Message -----
From: <klehman@albedo.net>
To: <murphy-rebel@dcsol.com>
Sent: Tuesday, September 16, 2003 9:09 AM
Subject: Re: Sunday Meeting

You are right Lonnie and once again my thanks to Bob and Anna P. for
hosting these meetings. They do enough so I'll try to summarize a bit.

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We try our best Lonnie !! Will always pass on important
stuff like this reminder to modify the elevator trim tab.

......bobp

---------------------------------orig.---------------------------
At 07:41 AM 9/16/03 -0400, you wrote:

We need to find some way of sharing this good information with the rest of
the list!


----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Monday, September 15, 2003 11:11 PM
Subject: Sunday Meeting

Hi Bob & Brampton area Rebelers

Great meeting yesterday with a lot of good information.

snip

We need to find some way of sharing this good information with the rest of
the list!

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Hi Wayne

Thanks very much for your detailed advice. Greatly appreciate that. I
will try what you suggested. I just did a visual check & could see
nothing. I would obviously far rather find a problem than pretend it is
not there. Life is toooo good for that!

THanks again

Brian #328R

At 10:53 PM 9/16/2003 -0400, you wrote:

Brian, this piece will not fail suddenly and will take time to work the
rivets loose and or crack things, as I have shown in the pics I posted to
the archives. As you can see in the picture my rivets were loose, the skin
was cracked and the front tab spar flange was cracked for over an inch. It
was still holding in and doing it's job in this state. It's just a neglected
place for pre-flight inspections, when the airplane is on wheels! To check
for fatigue just push down on your tab and watch to see if the skin lifts at
the front spar of the trim tab right in front of the tab horn. With Howard's
it has finally showed up as what looks like a line of mold between the skin
and spar in this location and will be one of the first fall annual items to
be tackled. This isn't a new problem and not the first time it's been
discussed here. Everyone just needs to keep a good eye on what they are
flying and remember areas like this get punished at flyins etc with PARENTS
having to touch and feel our tin machines!

Cheers,
Wayne



----- Original Message -----
From: "Brian Cross" <bcross2160@rogers.com>
To: <murphy-rebel@dcsol.com>
Sent: Tuesday, September 16, 2003 10:41 PM
Subject: Re: Sunday Meeting

Hi Ken & Bob

I assume that Bob's Rebel did not have the SB 080520 applied to this
aircraft. The SB tells us that we should have 2 of these angle pieces
riveted back to back to form an inverted 'T' shape per your earlier
post. If this were the case then the new piece would have 1 rivet into

the

forward spar of the trim tab & the other 1 or 2 rivets into the skin
only. This would not double the strength or stiffness but would most
definitely be an improvement over the existing set up.

It is odd that on my airplane, there is no evidence of fatigue
cracking. Or is that what would happen, it would just suddenly fail
when a certain load is generated on the control surfaces. If that is the
case, all Rebels should be grounded until the fix is in place.

Brian #328R


RebAt 09:09 AM 9/16/2003 -0400, you wrote:

You are right Lonnie and once again my thanks to Bob and Anna P. for
hosting these meetings. They do enough so I'll try to summarize a bit.

Well you know about the trim tab horn ripping out of the trim tab.
Result was large, violent, and life threatening elevator oscillations.
Elevator would move up, tab would violently force it back down and vica
versa. This is a large and powerful trim tab and it is difficult to
control an aircraft if you can't hold onto the stick... The tab is
probably large to enable getting the aircraft onto the ground with trim
if the elevator cables were to become disconnected. The reinforcing
bracket that was applied in bulletin 080520Reb to the vertical stab
rudder post was apparently cracked in half during this.

The thing is though, the horn that ripped out was not fastened according
to the manual, nor was the bulletin calling for a doubled horn
completed. As I understand it the original builder somply riveted the
horn to the twenty thou skin so it is no surprise that it failed. It was
not rivetted to a rib and the forward rivet did not even pick up the
spar in the original installation. MAM's design is certainly not at
fault here in any way. I can't imagine why they don't have the horn
doubling bulletin on the web site though.

Someone made a comment that they put a circuit breaker on their SR
because a runaway trim was uncontrollable. I would bet money that their
is little chance of getting a breaker pulled before full trim deflection
if the trim runs away. IMO there should be mechanical stops to limit
deflection if the aircraft is uncontrollable with full trim deflection.

As an aside, commercial aircraft often require two switches to be
activated to move a trim device that could destroy the aircraft.
Typically two switches side by side. Both must be activated together and
a short or failure in one switch can't move the trim. You sometimes see
switches that are not even rated for DC current in homebuilts and one
failure mode for these switches is contact welding or sticking. Anyway
two switches won't help if the short causing the runaway is in the servo
or wiring after the switch of course. This is way outside the scope of a
Rebel, but another thing you see is sensors that prevent trim movement
opposite to stick force. ie up trim is automatically deactivated if you
are pushing forward on the stick.

It was also suggested that pogs or nylon washers should be used to make
sure the elvators have no side to side movement. An example of badly
worn elevator bearings in 200 hours was given. It was suggested that
side to side vibration of the elevator may have contributed to the wear
by setting up an in an out sawing motion. One gentleman mentioned that
he had used some of MAM's bronze bushings for these bearings. Another
mentioned no problems at all on a high hour rotax powered machine that
that had the bearings regularly oiled.

Don't recall anything else but I had to leave the meeting early.

Ken


Lonnie Benson wrote:

rest of

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