AVIATOR pOinls - American Bonanza Society

N ElL'S NOT E S
Neil's Notes are from ASS Technlcol AdviSor Neil Pobanz unless otherwise noled.
TOGGLE-TYPE CiRCUIT BREAKERS - Many members are
already aware that ABS has had multiple meetings with the FAA,
conversations wi th switch manufacturer Tyco Electronics, discussions
with electrical DERs and conversations with Hawker
Beechcraft about circuit breakers addressed in AD 2008-13-17.
We have disassembled new breakers from RAPID and compared
them to Tyco breakers with the same Tyco pan number but
without the Beech pan number or switch cover. We opened newout-of-the-box
old breakers (those the AD says must be replaced)
and used breakers. We have surveyed reports of failed breakers
and asked ABS members for more information.
At the time of this writing-in early September- the bottom
line is: There were very few Service Difficulty Repons
(SDRs), all from the same operator. We have discovered very
few other instances that indicated internal breaker failure. none
of which resulted in any precautionary landings.
You can detect a problem by the feel of the toggle (it no
longer snaps crisply on and off), and if it gets hot to the touch.
There is an improvement to the switch sold through Hawker
Beechcraft. The original design is what is being sold through
other sources. with the same Tyco part number but without the
design change of the RAPID part.
Tyco has tested the improved Beech pan through 50.000
cycles, so even though it is a simple fix , the only way to comply
with the AD at this time is by obtaining breakers through
RAPID. We have other meetings planned wi th the FAA and
Hawker Beechcraft to continue discussing the AD.
For more information and updates, see the Members Only
page of www.bonanza.org.
EXHAUST-STACK CLAMPS - The exhaust-stack clamps on
Bonanzas with the three-bolt spring-loaded clamps should be
tightened enough to avoid stacking the springs, so that with two
hands you can flex the clamp or move it around with some effon.
CHROMED SPINNERS & POLISHED PROP BLADES -
Chroming spi nners and polishing propeller blades both create
an airwol1hi ness issue. OEMs, the FAA and ABS techs all feel
that this is an unairwonhy action . First, there is no approved
data covering these app lication s. Second, the processes can
contribute to fai lures. Minute scratches in the prop face resulting
from polishing can stan a corrosion crack. Molecular
structure changes to metal that results from the chroming
process can damage spi nners. In short, paint propeller blades,
and paint or polish spinners.
E GINE TO AIRFRAME GROUNDS - Again we have heard
of prop, mixture and throttle controls becoming substitute
engine grounds when the engine-mount grounds are absent.
This does not help their operation.
EARLY AfRPLANE IGNITION SWITCHES - Mark Givens
(870-25 1-2533) has an approval to install a late-model ignition
switch with minor wiring changes. This lets the subpanel battery
switch become the master switch and prevents cycl ing the
avionics when checking magnetos during run-up.
GEAR-DRNEN ALTERNATORS - The gear is cri tical, so
don't clamp it in a vise. When sending alternators for repair, it
is best to send along the gear, to be NDT inspected. The installation
of the gear is covered in great detail in TCM service
publications, and is imponant to prevent engine fa ilure.
GROUNDS ON FUEL LINES - Many Beech aircraft ground
the metal tubing carrying fuel through the wing and fuselage
via a bonding strap tied to the tube with a clamp (see picture).
These clamps sometimes become areas for corrosion as moisture
gets between the fuel line and the clamp.
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A bonding strop attached to the fuel tube with a clomp to ground it. These clamps
con become areas for potential corrosion.
It has now been brought to our atten tion that Adel clamps
have been used with the rubber still on the clamp. When investigati
ng how that could make a conductor to ground, technical
suppon people at Beech advised us that the new clamps have a
slit in the rubber to allow contact with the rube. I'm not SUfe
what that is going to do for moisture between the clamp and the
tube, or if it will always provide contact for electrical grounding.
We have had corrosion on aluminum fuel lines that was
severe enough to cause pinhole leaks. Combine that with
strobes that may not be grounded well. and a few wings having
blown up on the ground when the pilot turned on the
strobes. Note: There have been no injuries. @
ASS October 2008 www.bonanza.org Page 10995