Today's Message Index:
----------------------
1. 04:54 AM - flap flap again (David Feinstein)
2. 05:35 AM - Cracks in aft fuselage stiffeners: My 2cents (James Grieco)
3. 11:52 AM - Re: flap flap again (Steve Roberts)
4. 05:02 PM - Re: flap flap again (James Courtney)
5. 10:35 PM - Cracks in aft fuselage stiffeners (TeamGrumman@aol.com)
6. 11:28 PM - Re: Cracks in aft fuselage stiffeners (Gil Alexander)
Message 1
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--> TeamGrumman-List message posted by: "David Feinstein" <david@carneyaviation.com>
# AA-1B N9664L @ ILG << has used flaps on T/O and lived to tell about it.
from the manufacturer's Owner's Manuals:
AA1 - flaps UP (pg 11), no change for soft-field takeoff (pg 15)
AA1A - flaps UP (pg 14), * * * modified for soft fields (pg 18) * * *
AA1B - flaps UP (pg 2-4), no change for soft fields (pg 3-3)
AA1C - don't have that book
I have no idea why the recommendation would be different for AA1A and AA1B.
For AA1A, the owner's manual sez
The soft field ground run can be reduced with the use of FULL
flap. The flap extended take-off technique is identical to that
with flaps retracted.
--------------------------------------------------
OK, now who had that formula for The Step?
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Message 2
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| Subject: | Cracks in aft fuselage stiffeners: My 2cents |
--> TeamGrumman-List message posted by: James Grieco <jamesgrieco@yahoo.com>
Gary, I would reconsider doing much to stiffen that panel. From
what I have read on GG, the cause(s) are all speculation. The
basic description some gave of the purpose of those stiffeners
as a frame was completely wrong. They are nothing more than
panel breakers designed to stop the walls of the torque box from
buckling.
That area is bounded by the forward and aft vertical fin
attachment bulkheads and the upper web and lower skin. The ratio
of length to width is roughly 2.5:1 which is fairly typical of
beam webs. As our grummans are made as light weight as possible,
the webs probably fail in shear buckling when subjected to
ultimate loading (presumably torsion from the horizontal and
vertical). The simple and most weight efficient fix is to put
'panel breakers' at mid bay to stiffen the webs and prevent
buckling.
>From all the pictures that I have seen the cracks occur where
the stiffeners overlap each other. This might have been done to
provide some stability to the vertical flange of the stiffeners,
but I suspect it was done simply to allow manufacturing to put
glue on all the surfaces, and it probably aids in fixturing the
stiffeners in place. That the crack would initiate there is not
a real surprise, but they do last many years.
In any event, it does not make those stiffeners act as any real
frame in my opinion, as a frame would require an inner cap. I
would bet that once the crack releases the ends of the two
stiffeners from each other, that is the end of the problem. This
would could be proven if the a/c that have had this problem have
had the condition for a long time (very probable) and they had
no further crack growth. The function of the stiffener as a
panel breaker is not at risk. From my experience on our
Grumman's very big brothers, this is not unusual.
Message 3
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--> TeamGrumman-List message posted by: "Steve Roberts" <aa1bflyboy@msn.com>
Thanks Dave. Actually my experiance with the flaps down on T/O was when I
was still a student pilot. I did a touch-n-go and forgot to raise them right
away. I did notice I left the ground almost imediately but after climbing to
about 100' AGL my climb performance went to shit. I then checked my flaps
and sure enough when raised 64L's climb improved a good bit. She never did
quit climbing though even with full flaps.
Do a lot, get a little;
Do a little, get a lot;
Do nothing, get it all.
Steve Roberts - AA-1B N9664L @ ILG
----Original Message Follows----
From: "David Feinstein" <david@carneyaviation.com>
Subject: TeamGrumman-List: flap flap again
--> TeamGrumman-List message posted by: "David Feinstein"
<david@carneyaviation.com>
# AA-1B N9664L @ ILG << has used flaps on T/O and lived to tell about it.
from the manufacturer's Owner's Manuals:
AA1 - flaps UP (pg 11), no change for soft-field takeoff (pg 15)
AA1A - flaps UP (pg 14), * * * modified for soft fields (pg 18) * * *
AA1B - flaps UP (pg 2-4), no change for soft fields (pg 3-3)
AA1C - don't have that book
I have no idea why the recommendation would be different for AA1A and AA1B.
For AA1A, the owner's manual sez
The soft field ground run can be reduced with the use of FULL
flap. The flap extended take-off technique is identical to that
with flaps retracted.
--------------------------------------------------
OK, now who had that formula for The Step?
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Message 4
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--> TeamGrumman-List message posted by: "James Courtney" <jamey@jamescourtney.net>
I'd be pretty surprised to fly a plane that didn't climb with flaps
deployed. I think the real fear is that you won't climb fast enough to
clear an obstacle rather than you won't climb period. Certainly at high
density altitudes you could presumably aggravate the climb gods enough by
dropping your flaps that maybe you'd be negative on the climb rate but this
should be fairly exceptional for most aircraft I'd think. I refer only to
familiar single and probably multi-engined GA aircraft and make no
assumptions about more exotic fare or anything that reports it's speed in
mach numbers. Are there common aircraft in anyone's experience that will
not climb under near standard conditions with flaps deployed?
Jamey
-----Original Message-----
From: owner-teamgrumman-list-server@matronics.com
[mailto:owner-teamgrumman-list-server@matronics.com] On Behalf Of Steve
Roberts
Sent: Friday, April 14, 2006 11:50 AM
Subject: RE: TeamGrumman-List: flap flap again
--> TeamGrumman-List message posted by: "Steve Roberts"
--> <aa1bflyboy@msn.com>
Thanks Dave. Actually my experiance with the flaps down on T/O was when I
was still a student pilot. I did a touch-n-go and forgot to raise them right
away. I did notice I left the ground almost imediately but after climbing to
about 100' AGL my climb performance went to shit. I then checked my flaps
and sure enough when raised 64L's climb improved a good bit. She never did
quit climbing though even with full flaps.
Do a lot, get a little;
Do a little, get a lot;
Do nothing, get it all.
Steve Roberts - AA-1B N9664L @ ILG
----Original Message Follows----
From: "David Feinstein" <david@carneyaviation.com>
Subject: TeamGrumman-List: flap flap again
--> TeamGrumman-List message posted by: "David Feinstein"
<david@carneyaviation.com>
# AA-1B N9664L @ ILG << has used flaps on T/O and lived to tell about it.
from the manufacturer's Owner's Manuals:
AA1 - flaps UP (pg 11), no change for soft-field takeoff (pg 15)
AA1A - flaps UP (pg 14), * * * modified for soft fields (pg 18) * * *
AA1B - flaps UP (pg 2-4), no change for soft fields (pg 3-3)
AA1C - don't have that book
I have no idea why the recommendation would be different for AA1A and AA1B.
For AA1A, the owner's manual sez
The soft field ground run can be reduced with the use of FULL
flap. The flap extended take-off technique is identical to that
with flaps retracted.
--------------------------------------------------
OK, now who had that formula for The Step?
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email
Message 5
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| Subject: | Cracks in aft fuselage stiffeners |
--> TeamGrumman-List message posted by: TeamGrumman@aol.com
The torque box is made up of the rear bulkhead (where the vertical spar
attaches) and the bulkhead where the forward vertical attachment attaches. This
is also the torque box used by the original Traveler for the attachment of the
forward portion of the horizontal (as well as the forward vertical
attachment).
A couple of years ago, when this whole cracking problem became an issue, I
sent drawings to an engineer to have him come up with a probable cause for the
cracking. It was his opinion that the torque box, still acting as a torque
box, was racking during a sudden input to the rudder (possibly to counter a roll
input, shear, wind gust etc.).
His conclusion was that when the rudder is moved quickly, the vertical moves
(in the opposite direction) and loading the aft bulkhead. Since the rear
horizontal spar is also attached it (the rear bulkhead), it responds to the
rudder input. The inertia in the 12 foot horizontal resists the rudder input
and the forward horizontal spar and it's attachment to the fuselage through the
subject vertical spar support angle and the lower horizontal stiffener respond
slower than the rear bulkhead. Since the torque box is made up of the rear
bulkhead and the forward bulkhead (where the original horizontal attached), it
racks and causes stress risers at the junction (sharp corners) where the
vertical spar support angle and the lower horizontal stiffener are bonded.
He cautioned that once the joint (or the lower horizontal stiffener) cracks,
the load is then transferred through the skin to the forward bulkhead.
Either way, the skin carries a fair portion of the twisting imposed by the rudder.
What you say about the stiffeners being there to prevent the skin from
bucking is true. However, I think the stiffeners also help to act as a frame
to
transmit loads forward. Not a well designed frame, but a frame just the same.
If the frame had been completed up to and under the ELT panel assembly,
tying both vertical spar supports together at the top as well, it would have been
a lot stronger torque box. The double I have in mind would help transmit the
twisitng of the vertical spar support angles to the stronger forward
bulkhead.
I've seen a lot of the horizontal stiffeners buckled. I have only seen one
with a crack in it. Do I think it's a big problem? No. Do I think
debonding, removing and then replacing the the same pieces is the right approach?
No. Do I think adding a double that is radiused in the corner and transmits
the load the the entire portion of the tail assembly is a better idea? Well,
yes, that's why I want to do it. If the DER and structural engineer agree,
I'll do it.
Gary
Message 6
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| Subject: | Re: Cracks in aft fuselage stiffeners |
--> TeamGrumman-List message posted by: Gil Alexander <gilalex@earthlink.net>
Example can be seen here...
I believe my buckling is typical and follows what Gary describes.
http://home.earthlink.net/~gilalex/Tiger/
However, my horizontal showed some hangar rash and denting, and the tail
tie down ring was bent back a bit.
Excess loads could have come from other sources than the one Gary mentions...
It was repaired (?) by replacement of the stiffeners per the SAIB, but
since no-one really knows what did it, can it be called fixed?
It will be interesting to see if any of the repaired ones buckle a second
time.....
gil in Tucson
>I've seen a lot of the horizontal stiffeners buckled. I have only seen one
>with a crack in it. Do I think it's a big problem? No. Do I think
>debonding, removing and then replacing the the same pieces is the right
>approach?
>No. Do I think adding a double that is radiused in the corner and transmits
>the load the the entire portion of the tail assembly is a better
>idea? Well,
>yes, that's why I want to do it. If the DER and structural engineer agree,
>I'll do it.
>
>Gary
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