Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NM-07-19
March 14, 2007
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) advises you,
owners and operators of Boeing Company Model 707 airplanes, to inspect
the freeplay of the outboard aileron tabs.
Background
Service history has shown that unbalanced flight control surfaces are
susceptible to limit cycle flutter after excessive wear and corrosion
of certain components of the surface control system. Boeing has issued
Service Bulletins to address this issue with most of their models, but
there has not been one issued for the 707 model. This SAIB will address
the recommended procedure to check the freeplay of the outboard aileron
tabs to ensure it is within specification according to Military
Specification MILA-8870A Section 3.2.7.3.2.
Recommendations
Required tools and equipment:
Dial indicator with magnetic base and adjustable rods (0.001 inch resolution, 1 inch range minimum)
Push/pull force scale (0-10 pound minimum range, 0.5 pound resolution or better, and 10% minimum accuracy)
Scissor lift (or other lifting device) positioned under the left or right outboard aileron tab
Ferrous plate
Speed tape (to hold ferrous plate onto surface of outboard aileron)
Set up:
Verify that Aileron system has been rigged correctly.
Mark locations (using
masking tape and pen/pencil) for force application and position
measurements as identified in procedure below.
Install ferrous metal plate
to outboard aileron just inboard of the outboard tab using speed tape.
Ensure plate cannot move even slightly with 5-10 pounds of force in any
direction.
Ensure flaps are retracted fully (so ailerons are locked out).
Immobilize the outboard
aileron by clamping the aileron to the adjacent wing near the trailing
edge using wooden plates. Some spacers may be necessary between the
blocks and the surface due to the flap not being exactly in-line with
the aileron.
Attach dial indicator to ferrous plate using magnetic base.
Test Procedures:
Apply 10 +/- 0.5 pound
downward force to outboard aileron tab opposite the outboard tab rod
and 1.0 +/- 0.25 inches forward of trailing edge. (Note: If using
push/pull scale, be sure to use fitting on end of scale to distribute
force and prevent damage to tab.)
Hold force for 5 seconds.
Remove downward force.
(Note: Use care not to touch tab until step 7 below. If the outboard
aileron tab is touched before step 7, restart this test.)
Adjust dial indicator so the
plunger makes contact with aileron tab at location 1.00 +/- 0.25 inches
forward of trailing edge and 1.00 +/- 0.25 inches outboard of corner at
inboard trailing edge.
Zero the dial indicator. Ensure plunger is still in contact with control surface per above.
Take measurements by recording dial indicator readout at specified trailing edge location.
Apply 10 pound upward force
at the same location 1.0 +/- 0.25 inches forward of trailing edge in
line with the inboard row of rivets corresponding to the tab rod
support structure.
Hold/maintain specified
force until position readings have remained unchanged for 5 seconds (If
reading won’t stabilize, find source of instability before continuing).
Record dial indicator readout at trailing edge.
Max freeplay is 0.1 inches.
If freeplay is greater than 0.1 inches, then remove, replace and
recheck parts until freeplay is less than 0.1 inches.
Repeat the freeplay check for the opposite aileron tab.