Product Issues
Starter Cable Upgrades
We previously touched on cable upgrades. l-Iere is a more
comprehensive look at cables and other available upgrades.
BY
LPM STAFF
nyone reading LPM for a while
knows that we write a lot about
electrical issues such as basic wiring, batteries, starters,
alternators and the like. One big
reason is that reader e-mail is constantly
asking for advice on chronic failures of
these parts, systems, and if there are any
products available that may improve reliability and/or performance. Hint-there
are.
One cause of aircraft problems is that
everything is done with an eye on minimal weight. This has resulted in marginal
sized starting batteries and often low
powered starter designs subject to relatively easy overheating or overuse. While
the availability of lightweight starters
has helped the weight issue, it has placed
increasing demands on starter cables and
components.
With such expensive aircraft component costs we sometimes see owners waiting until a part fails before replacement.
In some cases, owners are doing it with a
cheaper, non-aviation qualified replacement part-a potentially dangerous idea.
A failing part often dies gradually,
which sometimes causes related system
malfunctions, "intermittents" and general
performance degradation while failing.
Contributing to this is sometimes a lack
of comprehensive, ongoing preventative
maintenance or routine parts replacements, particularly in areas that may not
be readily accessible for inspection. This
is also related to some owner efforts at
keeping maintenance costs to a bare minimum, an understandable but often futile
goal for aircraft safety.
This strategy frequently ends up costing much more than good preventative
maintenance. Dealing with part failures is
certainly more inconvenient than planned
maintenance.
A
got these photos recently while a Piper
Cherokee was in for an annual at a local
shop. It was a fortuitous time as it illustrated several common problems, both with
the battery box setup and with wiring
practices.
In our observations this plane needs
additional repair of this system to pass the
annual and to be safe and to start reliably.
The owner was not available for an interview. (See photos.)
What we have is a battery box of the
old Piper style that had the stock undersized aluminum cables replaced between
the starter motor attached to the engine
and the battery relay beside the battery
box. He also replaced the cables from the
relay to the battery box with copper.
Unfortunately, there are still existing
problem issues with the stock setup on the
positive terminal on the side of the battery
box, as well as the alterations done to the
negative terminal cable.
The positive cable from the battery
relay connects to a lug on the side of the
battery box. In turn, this connects to the
battery via the soldered braid to the battery terminal.
This adds an unnecessary additional
terminal connection at the outside of the
battery box. It also tends to reduce starter
current available to the starter motor by
design if the connections are in anything
but ultra pristine condition.
Especially with high current applications you do not want to have any more
terminals or connections than absolutely
necessary. The original design was more
complicated than it needed to be for
reliability and adequate starting power
between the battery and starter motor.
Cable size was marginal.
In this airplane there has been an attempt to add aftermarket cables made of
copper-a good idea with not such good
execution. We were not able to assess the
cables between the starter motor and the
battery relay so we will concentrate on the
battery box wiring, and there is plenty to
address here.
The negative cable was pushed through
a small hole cut in the side of the battery
box. The hole is so small, it almost appears
that the terminal was crimped on after
the fact, but in any event the terminal was
crimped with a lower quality, small cross
section crimper, as opposed to being attached with a professional grade tool.
This results in less optimal crimped
surface area and greater potential for the
infusion of corrosive agents into the terminal. Further promoting corrosion in an
acidic environment is the lack of any heat
shrink protective wrap on the terminal-tocable junction.
The net result is reduced current capacity over what could have been possible and
substantially increased exposure to corroOld-style Piper battery box originally had
aluminum cables to starter. The factory later
recommended upgrading to (opper, but specified undersized cables. There are two sets of
cables involved. Those from the relay to the
starter motor and a separate set from the relay
to the battery box or battery. There are better
options for reliable starting and safety.
ASPECIFIC WMPlE
Let's look at how one Piper owner has
tried to solve his starting cable issues. We
www.lightplane-maintenance.com
APRIl2014 . .
CABLE SPECIFICS
Photo is reversed 180 degrees for a better visual appearance. Note messy braided cable inside box,
which adds an extra connector. Replacement copper negative cable wire was run through the side
of the ragged hole in side of box with no cable protection from chaffing.
sian by-products further reducing current
capacity. The circuit is no more reliable
than the weakest link.
More problems exist here as well. The
wire was run through the side of the box
with no protective grommet or any form
of protection from chaffing on the side
of the ragged hole in the box. Accepted
shop practices require grommets!chaffing
protection for all wiring. This suggests
amateur, unapproved work.
While it may be argued this is only a
ground, as the chaffing progresses the
increasing number of cut strands will re-
duce the whole electrical system effectiveness. Eventually the plane will not start or
other high current devices will not operate
properly.
The ground wire capacity needs to be
the same as the positive wires for the system to work properly. Ifthe ground wire is
chaffed and strands are cut, the system is
compromised.
Even more significant is this hole
without a grommet will not keep acidic
battery box air from infuSing into the
fuselage. Notwithstanding the existence of
a functional vent line, this is still a danger-
Negative cable was crimped with so-so crimper. The entire terminal would greatly benefit in performance from pro-quality crimp of this critical, high current connection. There is no protective plastic
shrink wrap to keep out the battery fumes that will accelerate corrosion into the terminal connection-read early failure. The un-grommeted hole in the box allows add fumes into the fuselage.
The braided terminal is also showing signs of fraying as it is folded at an angle by design.
. . APRIL2014
The aluminum found in most Piper aircraft
(AL-l) was designed to max out at 180 amps.
The 4-gauge copper cable Piper suggested as
the replacement in 1986 in their S.B. 836 is rated
at 135 amps. Though the same physical weight
as AL-1, it does not have nearly enough current
carrying capacity for the average system.
Bogert's Low Loss Cables are rated at 211
amps. This means that Bogert's cables have 50
percent more capacity than 4-gauge copper and
25 percent more than the original AL-1.
Agood way to check if you're getting
adequate voltage to the starter is to use a
voltmeter on the starter while cranking. (Watch
that prop and set the meter up to do the check
remotely with the "voltage hold" function.)
Afully charged battery (12-volt system) that
drops to less than 10 volts at the starter when
cranking indicates that the starter(s) may not
be getting enough voltage. Low voltage equals
slow cranking speed.
Slow cranking speed equals high current
flow and heat buildup in the entire system. The
high current draw at low voltage will reduce the
battery and starter life, as well as increase the
chances for a fire.
As the voltage drops the current goes up
to try to feed the high current needs of the
starter motor, until the voltage drops to a point
that either the relays will not operate or the
starter motor will not tum. Unfortunately, since
the starter is designed to operate down to 9.6
volts or so in a 12-volt system there is a built in
ability for the starter system to overheat with
prolonged cranking if the pilot is not aware of
this potential.
(Cranking time limits are given with starter
motors and are based on adequate wiring and
a good battery.) When the battery is low or the
cables have more resistance than they should
from age or corrosion or being undersized it aggravates an already serious safety problem.
Aspecial note to pilots with lightweight
starters: They can be very useful when carefully
selected for the application. In our view, we
would go for the high-end units for anything
other than very occasional use, as there is a
significant range of quality available.
Lightweight starters are power hungry,and
need high inrush voltage to operate correctly
compared to a standard starter. Please make
sure your battery is in top condition, or you may
have problems. That means using wire that is
large enough and in great condition. If you're
. not willing to make the investment for the best
cables, don't bother with a lightweight starter
in our opinion-it won't live up to its potential.
LIGHT PLANE MAINTENANCE
ous practice. Note that flight control cables
run near the box.
AUTOMOTIVE ROOTS
Some components simply do not hold
up as well as hoped in the tasks they
were asked to perform as they have been
adopted from other industries (read cost
savings) rather than purpose built Earlier
switch gear was adopted from the automotive industry as were voltage regulators
and generators/alternators.
This same principle holds for other
component classes. Early failures generated some part modifications by the
aircraft manufacturers. Over the years
there has been some evolution for greater
ruggedness and reliability, but many
electrical components still have their roots
in automotive technology with attendant
shorter life spans.
Today these components, when
qualified for aviation, are supposed to
be quality controlled more rigidly and
altered/improved to meet aeronautical!
PMA quality standards for reliability
under more demanding conditions. Some
products seem to do pretty well without
any mods. All they need is the extra
quality control checks. Others need more
substantial beefing up in addition to the
individual quality checks.
For example, while your modern aeronautical alternator looks virtually identical
to an automotive version from the auto
parts store, it often has been subtly modified for more severe duty and reliability.
All the above said, there are many
people who believe there is absolutely no
difference between a Chrysler alternator from the auto parts store or from an
aero parts retailer. We disagree. Legally
the point is moot, since it's illegal to put
a non-PMA part on a certified airplane.
(Some small components are not offiCially
stamped PMA but are expected to meet
MIL or SAE or other civilian industrial
standards of accepted quality such as nuts
and bolts and terminals according to the
FARs.)
ALUMINUM WIRE FAILINGS
Sometimes there is simply a bad choice
made with good intentions to save weight
and cut costs. An example is aluminum
starter cables used in some older Piper
aircraft. The aluminum may have looked
OK on paper but just never properly did
the job.
www.lightplane-maintenance.com
Because of the metal mismatch and
25 percent under-sizing for amp needs,
there were accelerated corrosion issues
and starting problems-even fires in
some instances from overheating wires
and battery box connections. There were
subsequent Piper service bulletins recommending replacing the cables but there are
aluminum starter cables or battery box
terminals that still exist (see sidebar for
problems even with copper cables recommended by the factory).
Fortunately; there have been some
independent companies who have made
it their goal to dramatically improve some
of these sub-performing components
with a more robust and effective products. Bogert Aviation is one example of a
company that developed improved copper
starter and battery box connector cables,
and over the years has developed other
improved products over OEM deSigns
that fill an important niche.
They provide both electrical performance improvements as well as added
safety with their electrical products. They
are all STC'd or otherwise qualified for
certified aircraft where required.
Their available wiring products continue to expand since there is a growing
demand, including for experimental
aircraft. Contact them for custom wiring
needs.
Bogert Aircraft also has an eclectic mix
of jacks and associated products as well
as fuselage and wing restoration rotators.
For a more complete set of products go to
Upper left, old style Piper battery box terminal
and Bogert replacement. left, Replacement
Bogert battery box eliminates extra conne(tions. Above, top, dose up of Bogert STC battery
box modification. Above, Bogert has a selection
of custom (abies as well as a number of other
electrically oriented and eclectic products.
www.bogert-av.com.com. phone (800)
627-8088.
OUR FAVORITE REPLACEMENT
Our favorite Bogert STC'd products are
the improved starting cables for Pipers
that had the aluminum cables. The complementary product to the starter cables
for the Piper is the battery box modification to replace the complicated, trouble
prone, OEM design. They also have the
short cables from the relay to the battery
available in high capacity copper.
This STC'd battery box mod makes
for easier battery installation/removal
and eliIninates the extra connection on
the outside of the battery box. It also does
away with the troublesome braided battery box strap, redUCing system complexity. (See photos.) This mod is less expensive than to replace the entire battery
box. However, a complete STC'd Bogert
battery box incorporating all the mods is
also available.
Note that aircraft using Concord CB35A and RG-35A batteries must install
two PN 1-1-6 adapter plates to the battery
posts before completing the Battery Box
Modification. These adapter plates raise
APRIl1014 . .
(Continued from Previous Page)
the battery post height to equal the post
height of standard G-35 series batteries.
Bogert also sells improved starting cables available for many other GA aircraft.
The benefit is improved starting current
flow from low loss cables and properly attached and protected terminals. Wire and
terminals need periodic replaCing as age
and heat and high current does take a toll.
We've seen very old starter cables fall apart
as we started to detach them.
This can help improve starter and
associated relay!contactor life by reducing
heat and improve battery life by reducing
incidents of severe battery drain to overcome higher resistance OEM cables. It can
also help provide a start with a depleted
or partially discharged battery where
an OEM cable would not do it, all other
things being equal.
These cables make a great upgrade for
any airplane, especially older Pipers. One
last note, though-replacing a starting
cable in an airplane can prove to be a real
exercise in gymnastics and frustration.
The wires can be very difficult to access
and replace. Get a mechanic's supervision.
A few of the aviation catalogs sell the
Bogert products or go to their Web site at
bogertaviation.com, ph (800) 627-8088.
HEAVY CRIMPERS
We might note that we have seen (and tested)
several very marginal, low cost cable crimping
devices for heavy gauge cable for sale in aero
catalogs. Some crimpers are hit with a hammer; others use a small crimping surface.
In our opinion, testing and experience,
while these devices can be made to work, they
will absolutely not give the full performance
that your high current cable was designed to
carry. They become the weakest link as well
as the subject of much easier ingress of corrosion-even with a protective wrap.
Aproper set of heavy duty cable crimpers
have huge handles; some are hydraulically
assisted, and will cost several hundred dollars.
The advantage is they crimp most of the terminal surface to, in essence, form a cold weld.
Have your cables properly fabricated by a
professional shop. The result will be years of
optimal use and your battery will be able to
deliver the power your starter or other high
current devices needs to work optimally.·
. . APRIL2014
Tuned Exhausts
Like any speed/pelformance mod) understanding benefitsand costs- is the best way to decide if it suits your needs.
BY
LPM STAFF
hat are tuned exhausts?
Many owners are probably familiar with the term
"headers" with respect
to the automotive world.
Headers are commonly referred to as an
aftermarket, owner purchased replacement part for the exhaust system that
bolts directly to your engine exhaust
ports.
With due deference to possible
oversimplification, the primary use
for tuned headers is for increased
engine power and efficiency. The idea
is to optimize the pipe length, and
diameter and to minimize restrictions in the exhaust header for
performance increases over stock
systems. Usually high rpm is where
the most benefit is seen with tuned
exhausts.
The engineers at Power Flow
describe a stock exhaust system
operation as follows : ''As the spent
fuel air mix ture leaves the cy linder, it
is routed through a set of headers into
a common collector area and pushed
out the tail pipe by the remaining
pressure. Like a garden hose with a
kink in it, (referring to a stock system)
pressure builds up throughout the
exhaust system, making it more difficult for the spent gas mixture from
the next cy cle to leave. So now, the
exhaust isn't flowing as freely as it
should, leaving some exhaust in the
cylinder, taking up space better used
for a clean fu el/air charge."
"Our Power Flow Tun ed Exhaust
System is totally different. When you
break down our exhaust system, you
have two "sets" of pipes; the primary
(header!collector combination) and
the secondary (pipe after the collector). The primary contains four independent tubes that all join at the ''4-1
Collector. " As each "exhaust puff" of
spent fuel travels through the prima-
W
ries, it leaves a vacuum behind."
"In our tuned exhaust system,
we have adjusted the length of each
tube so that the vacuum reaches the
collector just in time to "suck out"
the exhaust from the next cylinder.
The exhaust gases are not only being
pushed out by the cylinder, but "extracted" by the vacuum, so a bigger,
fresher charge will enter the cylinder during the next cycle. A tuned
exhaust system really promotes a
smoother, cooler, and more powerful
running engine. "
At LPM we agree with this assessment; it's only the degree to which
such a system is effective at lower
rpm increases that may be debatable,
considering the limited RPM range
of an aircraft engine and space we
are dealing with in an aircraft engine
and the engine compartment.
HOW WELL DO THEY WORK?
If our airplane engines were higher
revving beasts the effects of tuned
headers would be more dramatic as
they are in high revving auto race
engines. As it is, there is still a measurable benefit. But these systems are
not cheap, and if payback from fuel
effiCiency is your goal it probably
may never happen, since header wear
and tear (as with any stock system)
will take its toll long before the payback time is reached via fuel savings.
What are the claims? Well, they
vary from airplane to airplane, but
a minimum of few hundred feet per
minute and 2 knots or even more
should be expected for a, say, a Cessna 172. (Power Flow claims up to 6.5
knots in fixed-pitch prop engines to
correspond to the typical 30 to 130
RPM increase.) They also claim a
1.19 to 1.9 GPH or even better fuel
improvement is possible.
For some constant-speed props
LIGHT PLANE MAINTENANCE