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Question:
I recently flew one of my students 1946 BC12D. It has a quite noticeable
tendency to turn left (or drop the left wing), my student has noticed this
as well. In cruise I have to hold a significant amount of right aileron and
can see the aileron deflected. This apparently causes some adverse yaw to
the left so I have to hold quite a bit of right rudder is well. What is the
easiest way to check and change the rigging of the wing.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Have you checked the wing for any indication of damage at the tip. A friend
just tapped the tip on a building and the long moment of the wing failed the
rear spar. He was lucky to get on the ground in one piece next flight. It
takes VERY little force at the tip to damage the wing attach! Try taking
the wing tips, one at a time and applying a little twisting force to each
and a little up and down. Do both feel the same? Are there any
"interesting" noises?
The next step would be to hold a level on the bottom of the tip rib while
raising the tail up onto a table and shimming it higher with magazines till
you get a level indication. Take the level to the other side and put it in
the same place to see if the tip incidence is the same on both sides.
Repeat this at the strut attach and the fuselage side (you are most likely
to see it at the tip). Have you checked to see if the fuselage is level at
both the seat back tube AND the horizontal stab? I have seen some pretty
twisted fuselages (my 45 for instance). Once you have levelled the fuselage
side to side (magazines under one wheel) check that there is the same
dihedral in each wing (use the level on the wing spanwise this time and
measure the distance from the level to the wing skin at the outboard end of
the level- two people will keep the airport rail birds from laughing so
hard, but it's worth it to see if your plane is straight). Next take a
piece of very light chain or metal tape (NOT STRING!) and measure from the
aileron outboard hinge or the aft strut attach to the back of the fin. The
sides should be the same.
Notice that you haven't RIGGED anything. All you are doing is checking to
see if everything is straight. You really need to resist the urge to start
changing the strut rigging until you really know what is causing the
problem. If the fuselage is twisted or bent it could be a sign of a serious
problem and you may be able to adjust the struts to hide it (at one speed)
but you haven't solved the problem and if you have spar damage you could be
setting yourself up for a "final flight".
If you DO find that the struts are out of rig be VERY careful how you adjust
them. It would be kind of embarrassing to screw one out and only have it
held on by half a thread wouldn't it? It has happened before! You also
want to make sure that you adjust the correct thrust or you will change the
wash-in on the wing and that will change the handling. There is a procedure
for that too but I have rambled too long already.
By the way, you need an IA to be changing the rig on your struts but you can
measure all you want yourself.
HankJ
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
First level the ship as quoted in the manual.
"Levelling Procedure"
"Level in a fore and aft direction by supporting tail on stand and placing
bubble level on the horizontal stabilizer. When bubble is centered, the
aircraft is longitudinally level."
"To level aircraft laterally, place bubble level on one of the top fuselage
cross members or the seat cross tube." When the bubble is centered the ship
is laterally level. This step is not required for weight and balance but
"for rigging wings this step is very necessary."
Okay, now we have a level ship front-to-back and side-to-side but in the
very next paragraph is the "Rigging Information", and this is the kicker -
It says; "To check the rigging of the wings and tail, stretch a cord across
the wings at the front spar and level the ship with a line level placed
over the center of the cabin. Stretch a second cord across the wings at the
rear spar and level with a line level. The rear strut adjustment is used to
accomplish this".
Well, which is the most correct method for lateral levelling? Is the method
that uses the fuselage cross tube and a bubble level the most correct? What
if the line level hanging from the cord stretched above the front spar says
the ship is not level when the bubble level on the fuselage cross tube says
it is level? Do you relevel it? Would not a difference between the two
methods indicate an alignment problem between the wings and the fuselage?
Which is the most correct? Is levelling the fuselage cross tube just a
beginning reference point?
On my airplane we used the method described in the owners manual to check
washout. This requires a 30" level. When the airplane is levelled fore and
aft and laterally, one end of the level is placed up against the bottom of
the rear spar, at it's center point front-to back, and at the "first full
rib from tip - about 26" from tip". While holding the end of the level
against the bottom of the rear spar at the first full rib, pivot the level
upward until the top of the opposite end is exactly 1-5/16" from the bottom
of the first full rib and is at the centre of the front spar, front-to-back.
Is this wing wash adjustment levelling supposed to agree with the bubble
level over the rear spar?
It seems like there are too many places to level the ship and no
explanation of what to do if they do not all agree with each other.
My airplane always flew left wing heavy. At the last annual the airplane
was levelled and the rigging checked. The left wing was found to have only
about 1/2 the wash that the right wing had. Or, in other words, we had a
perfect 1-5/16" on the right wing, but way less on the left wing. So the
left wing wash was increased - the twist was increased - to be closer to
the spec. Now the airplane fly right wing heavy all the time. Let go of the
control wheel and in about 5 seconds you are in a continuously steepening
right turn. In a deliberate right turn of 20-25 degrees, the left aileron
trailing edge is now clearly visible approximately 3/16"-1/4" below the
wing trailing edge. Yes, below.
RandallR
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The manual rigging is the "starting" point that's why God created test pilots,
some ships needed three flights to make right. Remember back then they
built the airplane, THEN drew the drawings and built it to 1/8 of an inch.
"Measure with a micrometer then cut off with an axe"
AFTER setting the wash-out by the manual ( if you can, depends on who
built the wings up last). Then fly it. First have a ball-bank or tape one
in; even my butt is not sensitive enough. Cruise flight, smooth air, center
the ball with the rudder pedals. Wiggle the ailerons and let the wheels find
neutral, look out at the ailerons they should be level with the wing, if not
land and re adjust them...refly it, center the ball with rudder pedals If
the ship banks one way or the other, then wash in the wing that goes low
with the rear strut adjuster..... try two turns max. THEN wash OUT the
other wing if necessary. On the second flight you can start to adjust the
rudder trim tab so YOU do not have to hold the rudder pedals to center the
ball.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~
Does it fly with the ball in the center straight & level hands off in cruise
with you sitting in the middle? If so leave it alone. The weight shift
is that sensitive. If you fly always with no passenger then wash in the
left wing a bit. The aileron trailing down has to do with the wing build up
before cover.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
SOMETIMES the ailerons are not
lined up with the bottom of the wing during recovery ( there are shims under
the aileron attach fittings) this can cause a "fly-up" or fly-down" of the
whole aileron, either figure some clever way to re shim OR put a fixed
aileron trim tab on the ship. The tandems were built with this tab in
place....... when adjusting the carry through cable, the ailerons will
"droop" a bit on the ground, BUT will fly up level in the air. Have a
buddy hold one aileron level with the wing trailing edge and you should be
able to bring the other one up level with hardly any effort.
Another check of correct wash-out is "Minimum trim speed" this is
throttle back to idle , full nose up trim ( make sure THAT degree angle is
correct to the elevator) hands off the ship will glide at 60-70 MPH
indicated airspeed.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~
You need a sawhorse and a 30" level. Now go do this procedure which is
straight out of the owner's manual:
Level the plane. Use the horizontal stabilizers as the level reference
longitudinally and laterally.
Place a 30 inch level under the wing in the following manner:
Put the aft end of the level at the intersection of the FIRST FULL RIB FROM
THE TIP and the Rear Spar,
Put the forward end of the level below the Front Spar,
Hold the level Level (of course).
Measure the distance from the forward end of the level up to the bottom surface
of the wing. This distance should be 1 5/16" One and Five Sixteenths Inches.
Mark J
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Level the aircraft longitudinally (by raising the tail till the horiz stab
is horizontal)
Level the aircraft laterally (by using a level across the horiz stab or the
seat-back tube.
Measure the height of each wingtip from the ground. If they are
significantly different, you have a difference in length of the front
struts.
Tie a piece of string from wingtip to wingtip...this should also be level.
Are the ailerons equal in level flight?
RobL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~
The easiest way to remember might be to think, screw out, washout, screw
in, washin.
RR
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A spirit level across the spars with a known dimension spacer will give you approximately
the correct washout...the final adjustment is done after test flying on the screw
adjusters on the rear struts. The Taylorcraft should glide *without turning* at 60-65 mph
with power off, full up trim, but you need to get trim tab, elevator angles etc correct
first.. The angles for the BC12D are as follows:
Elevators Up 27 degrees, Down 25
Trim tab Up 25, Down 30 (relative to elevator)
Ailerons Up 23, Down 23
Rudder 26 Left and right.
These angles and other useful statistics are available on the Type Certificate,
downloadable in .pdf from www.taylorcraft.org/A-696.pdf
RobL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~
Shortening the rear strut lowers the trailing edge
and increases the angle of attack for the wing panel on that side. This
causes the "heavy" wing to lighten up by the addition of lift on the heavy
side.
Or you could raise the trailing edge of the "light" wing so it creates less
lift with a lower angle of attack.
You don't want to have too much wash in or out. Take good notes!!
ChrisB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~
I adjusted the little threaded sleeve clockwise, which
increased the angle of attack of the wing, and solved the problem. I only
adjusted the threaded sleeve one and one-half turns (it don't take much).
You might wish to make a mental note on this. turning the adjusting sleeve
clockwise increases the lift of the wing, counter clockwise decreases the
wings lift. Also, you must adjust the height of the rear jury strut each
time you change the setting of the threaded sleeve on the rear strut. John
(flying straight and level) in N Fla.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~
Question:
I recently flew one of my students 1946 BC12D. It has a quite noticeable
tendency to turn left (or drop the left wing), my student has noticed this
as well. In cruise I have to hold a significant amount of right aileron and
can see the aileron deflected. This apparently causes some adverse yaw to
the left so I have to hold quite a bit of right rudder is well. What is the
easiest way to check and change the rigging of the wing.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Have you checked the wing for any indication of damage at the tip. A friend
just tapped the tip on a building and the long moment of the wing failed the
rear spar. He was lucky to get on the ground in one piece next flight. It
takes VERY little force at the tip to damage the wing attach! Try taking
the wing tips, one at a time and applying a little twisting force to each
and a little up and down. Do both feel the same? Are there any
"interesting" noises?
The next step would be to hold a level on the bottom of the tip rib while
raising the tail up onto a table and shimming it higher with magazines till
you get a level indication. Take the level to the other side and put it in
the same place to see if the tip incidence is the same on both sides.
Repeat this at the strut attach and the fuselage side (you are most likely
to see it at the tip). Have you checked to see if the fuselage is level at
both the seat back tube AND the horizontal stab? I have seen some pretty
twisted fuselages (my 45 for instance). Once you have levelled the fuselage
side to side (magazines under one wheel) check that there is the same
dihedral in each wing (use the level on the wing spanwise this time and
measure the distance from the level to the wing skin at the outboard end of
the level- two people will keep the airport rail birds from laughing so
hard, but it's worth it to see if your plane is straight). Next take a
piece of very light chain or metal tape (NOT STRING!) and measure from the
aileron outboard hinge or the aft strut attach to the back of the fin. The
sides should be the same.
Notice that you haven't RIGGED anything. All you are doing is checking to
see if everything is straight. You really need to resist the urge to start
changing the strut rigging until you really know what is causing the
problem. If the fuselage is twisted or bent it could be a sign of a serious
problem and you may be able to adjust the struts to hide it (at one speed)
but you haven't solved the problem and if you have spar damage you could be
setting yourself up for a "final flight".
If you DO find that the struts are out of rig be VERY careful how you adjust
them. It would be kind of embarrassing to screw one out and only have it
held on by half a thread wouldn't it? It has happened before! You also
want to make sure that you adjust the correct thrust or you will change the
wash-in on the wing and that will change the handling. There is a procedure
for that too but I have rambled too long already.
By the way, you need an IA to be changing the rig on your struts but you can
measure all you want yourself.
HankJ
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
First level the ship as quoted in the manual.
"Levelling Procedure"
"Level in a fore and aft direction by supporting tail on stand and placing
bubble level on the horizontal stabilizer. When bubble is centered, the
aircraft is longitudinally level."
"To level aircraft laterally, place bubble level on one of the top fuselage
cross members or the seat cross tube." When the bubble is centered the ship
is laterally level. This step is not required for weight and balance but
"for rigging wings this step is very necessary."
Okay, now we have a level ship front-to-back and side-to-side but in the
very next paragraph is the "Rigging Information", and this is the kicker -
It says; "To check the rigging of the wings and tail, stretch a cord across
the wings at the front spar and level the ship with a line level placed
over the center of the cabin. Stretch a second cord across the wings at the
rear spar and level with a line level. The rear strut adjustment is used to
accomplish this".
Well, which is the most correct method for lateral levelling? Is the method
that uses the fuselage cross tube and a bubble level the most correct? What
if the line level hanging from the cord stretched above the front spar says
the ship is not level when the bubble level on the fuselage cross tube says
it is level? Do you relevel it? Would not a difference between the two
methods indicate an alignment problem between the wings and the fuselage?
Which is the most correct? Is levelling the fuselage cross tube just a
beginning reference point?
On my airplane we used the method described in the owners manual to check
washout. This requires a 30" level. When the airplane is levelled fore and
aft and laterally, one end of the level is placed up against the bottom of
the rear spar, at it's center point front-to back, and at the "first full
rib from tip - about 26" from tip". While holding the end of the level
against the bottom of the rear spar at the first full rib, pivot the level
upward until the top of the opposite end is exactly 1-5/16" from the bottom
of the first full rib and is at the centre of the front spar, front-to-back.
Is this wing wash adjustment levelling supposed to agree with the bubble
level over the rear spar?
It seems like there are too many places to level the ship and no
explanation of what to do if they do not all agree with each other.
My airplane always flew left wing heavy. At the last annual the airplane
was levelled and the rigging checked. The left wing was found to have only
about 1/2 the wash that the right wing had. Or, in other words, we had a
perfect 1-5/16" on the right wing, but way less on the left wing. So the
left wing wash was increased - the twist was increased - to be closer to
the spec. Now the airplane fly right wing heavy all the time. Let go of the
control wheel and in about 5 seconds you are in a continuously steepening
right turn. In a deliberate right turn of 20-25 degrees, the left aileron
trailing edge is now clearly visible approximately 3/16"-1/4" below the
wing trailing edge. Yes, below.
RandallR
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The manual rigging is the "starting" point that's why God created test pilots,
some ships needed three flights to make right. Remember back then they
built the airplane, THEN drew the drawings and built it to 1/8 of an inch.
"Measure with a micrometer then cut off with an axe"
AFTER setting the wash-out by the manual ( if you can, depends on who
built the wings up last). Then fly it. First have a ball-bank or tape one
in; even my butt is not sensitive enough. Cruise flight, smooth air, center
the ball with the rudder pedals. Wiggle the ailerons and let the wheels find
neutral, look out at the ailerons they should be level with the wing, if not
land and re adjust them...refly it, center the ball with rudder pedals If
the ship banks one way or the other, then wash in the wing that goes low
with the rear strut adjuster..... try two turns max. THEN wash OUT the
other wing if necessary. On the second flight you can start to adjust the
rudder trim tab so YOU do not have to hold the rudder pedals to center the
ball.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~
Does it fly with the ball in the center straight & level hands off in cruise
with you sitting in the middle? If so leave it alone. The weight shift
is that sensitive. If you fly always with no passenger then wash in the
left wing a bit. The aileron trailing down has to do with the wing build up
before cover.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~
SOMETIMES the ailerons are not
lined up with the bottom of the wing during recovery ( there are shims under
the aileron attach fittings) this can cause a "fly-up" or fly-down" of the
whole aileron, either figure some clever way to re shim OR put a fixed
aileron trim tab on the ship. The tandems were built with this tab in
place....... when adjusting the carry through cable, the ailerons will
"droop" a bit on the ground, BUT will fly up level in the air. Have a
buddy hold one aileron level with the wing trailing edge and you should be
able to bring the other one up level with hardly any effort.
Another check of correct wash-out is "Minimum trim speed" this is
throttle back to idle , full nose up trim ( make sure THAT degree angle is
correct to the elevator) hands off the ship will glide at 60-70 MPH
indicated airspeed.
ForrestB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~
You need a sawhorse and a 30" level. Now go do this procedure which is
straight out of the owner's manual:
Level the plane. Use the horizontal stabilizers as the level reference
longitudinally and laterally.
Place a 30 inch level under the wing in the following manner:
Put the aft end of the level at the intersection of the FIRST FULL RIB FROM
THE TIP and the Rear Spar,
Put the forward end of the level below the Front Spar,
Hold the level Level (of course).
Measure the distance from the forward end of the level up to the bottom surface
of the wing. This distance should be 1 5/16" One and Five Sixteenths Inches.
Mark J
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Level the aircraft longitudinally (by raising the tail till the horiz stab
is horizontal)
Level the aircraft laterally (by using a level across the horiz stab or the
seat-back tube.
Measure the height of each wingtip from the ground. If they are
significantly different, you have a difference in length of the front
struts.
Tie a piece of string from wingtip to wingtip...this should also be level.
Are the ailerons equal in level flight?
RobL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~
The easiest way to remember might be to think, screw out, washout, screw
in, washin.
RR
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A spirit level across the spars with a known dimension spacer will give you approximately
the correct washout...the final adjustment is done after test flying on the screw
adjusters on the rear struts. The Taylorcraft should glide *without turning* at 60-65 mph
with power off, full up trim, but you need to get trim tab, elevator angles etc correct
first.. The angles for the BC12D are as follows:
Elevators Up 27 degrees, Down 25
Trim tab Up 25, Down 30 (relative to elevator)
Ailerons Up 23, Down 23
Rudder 26 Left and right.
These angles and other useful statistics are available on the Type Certificate,
downloadable in .pdf from www.taylorcraft.org/A-696.pdf
RobL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~
Shortening the rear strut lowers the trailing edge
and increases the angle of attack for the wing panel on that side. This
causes the "heavy" wing to lighten up by the addition of lift on the heavy
side.
Or you could raise the trailing edge of the "light" wing so it creates less
lift with a lower angle of attack.
You don't want to have too much wash in or out. Take good notes!!
ChrisB
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~
I adjusted the little threaded sleeve clockwise, which
increased the angle of attack of the wing, and solved the problem. I only
adjusted the threaded sleeve one and one-half turns (it don't take much).
You might wish to make a mental note on this. turning the adjusting sleeve
clockwise increases the lift of the wing, counter clockwise decreases the
wings lift. Also, you must adjust the height of the rear jury strut each
time you change the setting of the threaded sleeve on the rear strut. John
(flying straight and level) in N Fla.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~
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