flying-rebels Digest for 1 Jan 2000
Posted: Fri Feb 17, 2012 5:39 pm
An open letter to the Rebel Builders group on behalf of the Technical
Department of Murphy Aircraft Manufacturing.
Generally speaking it has been the policy of the Technical Department to
monitor but not interfere with the open and at times somewhat frank
discussions that form the main body of dialogue between builders involved in
this group. It is only when we see an improper precedence or dangerous trend
being established that we do interject. Recent concerns addressed by some
builders perhaps not fully involved in the events being discussed has led to
this interjection.
A builder had recently commented that it had not been brought to the
attention of all builders that some changes had been made to the Rebel
Series of aircraft by Murphy Aircraft Manufacturing.
Of particular concern, it was stated that one of our builder's completed
Rebel aircraft had been involved in an incident that had resulted in a
significant amount of damage occurring to the aircraft. This was in fact a
correct statement, however the next statement attributed this incident as
being caused by a failure of the bungee landing gear system that this
particular aircraft was equipped with. This aircraft incident was
investigated by Murphy Aircraft manufacturing in as much detail as the
evidence and available information allowed. (as are all such incidents) On
completion of the investigation it was found that although the bungee gear
had indeed failed, it had done so in excess of its design load limits and as
with all such physical devices the obvious next event occurred. The landing
gear collapsed and the aircraft ended up inverted on a grass field with the
expected secondary damage. To the aircraft and not the occupants, fortunately.
As such the second part of the comment was incorrect. This incident was a
result of actions taken in the air and the gear failure was a result of the
incident not its predicator
The drop tests, which were conducted on the Rebel, take into consideration
decent rates and forward speeds. These tests were performed with a real
loaded and fit out aircraft. The tests proved conclusively that the Rebel
not only met but also exceeded certified aircraft standards.
It has been stated by some that evidence exists which indicates this to be a
common problem to all bungee equipped Rebel aircraft. Again this statement
is incorrect. In fact evidence suggests just the opposite, the bungee gear
versions of the Rebel have proven to be quite robust even in adverse
conditions. No aircraft is totally immune to misuse or even extreme use if
not maintained and inspected on a regular basis. No aircraft will tolerate
excessive decent rates more than once with out some form of damage occurring.
In regard to Mr Allister Yeoman's Rebel based in New Zealand I have
personally worked with Allister to help resolve some of the issues his
particular style of flying has brought to light relative to his Rebel.
It should be further noted that a lot of the Allisters requirements are both
extreme and unique. Gross weight wheel landings on dirt trails so narrow
that he can not put his tail down with out hitting the debris on the side of
the strips he has been known to use. This requires extraordinary pilot skill
and aircraft design to meet his criteria. Because of this Allister has
served to provide Murphy Aircraft with some rather unique insights as to
what may or may not pose a problem in both current and future Rebel
aircraft. On the other hand fixes for Allisters aircraft not all of which
are Murphy Aircraft's suggested fixes have not been made generally available
to the other builders. The reasons for this are two fold. 1) Allisters case
is unique and we have cooperated with him and vise versa for the benefit of
all. However until more data is gathered and properly correlated the results
of his testing and fixing can not be put forward as gospel or even suggested
gospel. 2) Some of the fixes incorporated into Allisters aircraft are based
on time and money issues rather pure safety issues. This does not equate to
Allister having conserved money at the cost of safety. It does equate to
Allister excepting the fact that his spring gear system as installed in his
aircraft will severely damage the fuselage before failing in the event of a
excessively hard landing. As such Murphy Aircraft manufacturing cannot and
will not at the present time recommend this method of attachment to other
builders. It was suggested to Allister as his aircraft landing gear system
was already damaged and as such had to ether be replaced or modified. As to
whether Allister has been given special treatment over other builders the
answer is no. Allister was willing to pay the total cost in time and money
himself and was one of the few builders with the background, abilities, and
opportunities unfortunate as some of them were to test a Rebel to the degree
he has. As such everyone owes him a dept of gratitude.
Our job in the Technical department is to learn from his experiences and
disseminate what is learned to the other builders. This we do but not before
knowing all the facts.
Some other issues brought to light in regard to the Rebel aircraft concern
triangular tail wrap gussets etc. being used by builders. The use of these
gussets has been suggested to all the builders via bulletins posted on our
web page, they are also incorporated in the current Rebel manuals. As are
the firewall reinforcements and upper wing attach fuselage doublers for
float equipped aircraft. This bulletin is commonly referred to as the float
fix bulletin and has been posted on our web site for some time. So there are
no secrets here. As far as the current bungee and spring gear systems are
concerned both systems are well proven and tested. The European distributors
Rebel had in excess of 750 hrs of hard demonstration work all over Europe.
The gear system never failed during that time and has not done so to date.
Both the tricycle and standard version of the factory Elite aircraft which
are heavier and faster than the Rebel have a high number of hard hrs on
them doing the demonstrations all over North America and have suffered no
landing gear failures. Hundreds of high time Rebels using the conventional
bungee gear continue to do so with no evidence of or emanate evidence of
failure.
As to the matter of the Rebel door sill reinforcement that some builders
chose to incorporate into their aircraft. The reason this is done is to
prevent denting of the doorsill while loading and unloading cargo etc. It is
not a safety issue. This is done at the builders discretion not Murphy
Aircraft's suggestion or emphasis. Where weight reduction is at the top of a
builder's list such as in a float equipped 912 Rebel UL the heavier sill in
not a prime desire.
To summarize some of the key points of this long dissertation I would like
to make it known that
1)The Rebels landing gear is considered to to be a tested and tried system
both in the bungee gear version and the spring gear version.
2) In service failures of the Rebels landing gear are documented and
investigated. To date not one these gear failures have been the result of
the landing gear design or structure.
3) Improper installation of the landing gear and its associated systems has
caused failures. The landing gear bolts cannot be properly torqued by feel,
a torque wrench must be used. The landing gear and torque values must be
checked again after the first few cycles.
4) Murphy Aircraft's Technical Department is made up of experienced
engineers and pilots. We have to balance in service problems against
aircraft which show no such problems. Obviously it is to everyone's best
interest to solve problems as soon as they become known legitimate problems.
We can not however adapt the Rebel to test it self. As problems become
known, documented, averaged against realistic expectations, and solved we do
our best to insure the builders get the right story the whole story and the
right fix. We are proud of our products and want our builders to be also.
Sincerely,
Grant McDaniel
Technical Support Department/ Murphy Aircraft Manufacturing.
Wishing you and yours all the best in this holiday season.
Murphy Aircraft Mfg. Ltd
Manufacturers of the Renegade, Renegade Spirit, Rebel,
Maverick, Rebel Elite & the 4/6 place Super Rebel
mursales@murphyair.com
Web Site http://www.murphyair.com
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Department of Murphy Aircraft Manufacturing.
Generally speaking it has been the policy of the Technical Department to
monitor but not interfere with the open and at times somewhat frank
discussions that form the main body of dialogue between builders involved in
this group. It is only when we see an improper precedence or dangerous trend
being established that we do interject. Recent concerns addressed by some
builders perhaps not fully involved in the events being discussed has led to
this interjection.
A builder had recently commented that it had not been brought to the
attention of all builders that some changes had been made to the Rebel
Series of aircraft by Murphy Aircraft Manufacturing.
Of particular concern, it was stated that one of our builder's completed
Rebel aircraft had been involved in an incident that had resulted in a
significant amount of damage occurring to the aircraft. This was in fact a
correct statement, however the next statement attributed this incident as
being caused by a failure of the bungee landing gear system that this
particular aircraft was equipped with. This aircraft incident was
investigated by Murphy Aircraft manufacturing in as much detail as the
evidence and available information allowed. (as are all such incidents) On
completion of the investigation it was found that although the bungee gear
had indeed failed, it had done so in excess of its design load limits and as
with all such physical devices the obvious next event occurred. The landing
gear collapsed and the aircraft ended up inverted on a grass field with the
expected secondary damage. To the aircraft and not the occupants, fortunately.
As such the second part of the comment was incorrect. This incident was a
result of actions taken in the air and the gear failure was a result of the
incident not its predicator
The drop tests, which were conducted on the Rebel, take into consideration
decent rates and forward speeds. These tests were performed with a real
loaded and fit out aircraft. The tests proved conclusively that the Rebel
not only met but also exceeded certified aircraft standards.
It has been stated by some that evidence exists which indicates this to be a
common problem to all bungee equipped Rebel aircraft. Again this statement
is incorrect. In fact evidence suggests just the opposite, the bungee gear
versions of the Rebel have proven to be quite robust even in adverse
conditions. No aircraft is totally immune to misuse or even extreme use if
not maintained and inspected on a regular basis. No aircraft will tolerate
excessive decent rates more than once with out some form of damage occurring.
In regard to Mr Allister Yeoman's Rebel based in New Zealand I have
personally worked with Allister to help resolve some of the issues his
particular style of flying has brought to light relative to his Rebel.
It should be further noted that a lot of the Allisters requirements are both
extreme and unique. Gross weight wheel landings on dirt trails so narrow
that he can not put his tail down with out hitting the debris on the side of
the strips he has been known to use. This requires extraordinary pilot skill
and aircraft design to meet his criteria. Because of this Allister has
served to provide Murphy Aircraft with some rather unique insights as to
what may or may not pose a problem in both current and future Rebel
aircraft. On the other hand fixes for Allisters aircraft not all of which
are Murphy Aircraft's suggested fixes have not been made generally available
to the other builders. The reasons for this are two fold. 1) Allisters case
is unique and we have cooperated with him and vise versa for the benefit of
all. However until more data is gathered and properly correlated the results
of his testing and fixing can not be put forward as gospel or even suggested
gospel. 2) Some of the fixes incorporated into Allisters aircraft are based
on time and money issues rather pure safety issues. This does not equate to
Allister having conserved money at the cost of safety. It does equate to
Allister excepting the fact that his spring gear system as installed in his
aircraft will severely damage the fuselage before failing in the event of a
excessively hard landing. As such Murphy Aircraft manufacturing cannot and
will not at the present time recommend this method of attachment to other
builders. It was suggested to Allister as his aircraft landing gear system
was already damaged and as such had to ether be replaced or modified. As to
whether Allister has been given special treatment over other builders the
answer is no. Allister was willing to pay the total cost in time and money
himself and was one of the few builders with the background, abilities, and
opportunities unfortunate as some of them were to test a Rebel to the degree
he has. As such everyone owes him a dept of gratitude.
Our job in the Technical department is to learn from his experiences and
disseminate what is learned to the other builders. This we do but not before
knowing all the facts.
Some other issues brought to light in regard to the Rebel aircraft concern
triangular tail wrap gussets etc. being used by builders. The use of these
gussets has been suggested to all the builders via bulletins posted on our
web page, they are also incorporated in the current Rebel manuals. As are
the firewall reinforcements and upper wing attach fuselage doublers for
float equipped aircraft. This bulletin is commonly referred to as the float
fix bulletin and has been posted on our web site for some time. So there are
no secrets here. As far as the current bungee and spring gear systems are
concerned both systems are well proven and tested. The European distributors
Rebel had in excess of 750 hrs of hard demonstration work all over Europe.
The gear system never failed during that time and has not done so to date.
Both the tricycle and standard version of the factory Elite aircraft which
are heavier and faster than the Rebel have a high number of hard hrs on
them doing the demonstrations all over North America and have suffered no
landing gear failures. Hundreds of high time Rebels using the conventional
bungee gear continue to do so with no evidence of or emanate evidence of
failure.
As to the matter of the Rebel door sill reinforcement that some builders
chose to incorporate into their aircraft. The reason this is done is to
prevent denting of the doorsill while loading and unloading cargo etc. It is
not a safety issue. This is done at the builders discretion not Murphy
Aircraft's suggestion or emphasis. Where weight reduction is at the top of a
builder's list such as in a float equipped 912 Rebel UL the heavier sill in
not a prime desire.
To summarize some of the key points of this long dissertation I would like
to make it known that
1)The Rebels landing gear is considered to to be a tested and tried system
both in the bungee gear version and the spring gear version.
2) In service failures of the Rebels landing gear are documented and
investigated. To date not one these gear failures have been the result of
the landing gear design or structure.
3) Improper installation of the landing gear and its associated systems has
caused failures. The landing gear bolts cannot be properly torqued by feel,
a torque wrench must be used. The landing gear and torque values must be
checked again after the first few cycles.
4) Murphy Aircraft's Technical Department is made up of experienced
engineers and pilots. We have to balance in service problems against
aircraft which show no such problems. Obviously it is to everyone's best
interest to solve problems as soon as they become known legitimate problems.
We can not however adapt the Rebel to test it self. As problems become
known, documented, averaged against realistic expectations, and solved we do
our best to insure the builders get the right story the whole story and the
right fix. We are proud of our products and want our builders to be also.
Sincerely,
Grant McDaniel
Technical Support Department/ Murphy Aircraft Manufacturing.
Wishing you and yours all the best in this holiday season.
Murphy Aircraft Mfg. Ltd
Manufacturers of the Renegade, Renegade Spirit, Rebel,
Maverick, Rebel Elite & the 4/6 place Super Rebel
mursales@murphyair.com
Web Site http://www.murphyair.com
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