Comments on proposed Airworthiness Directive affecting Bellanca Viking
17-Series aircraft

Background:

The total unit production of aircraft under Type Certificate 1A3 and
A18CE was comprised of six (6) different models with 31 production years
spanning calendar years 1966-2005 with approximately 1358 total aircraft
produced, of which 1041 remained in the U.S registry as of the 1st
quarter 2007. These aircraft are not production aircraft similar to
Beech, Cessna, Piper or other volume produced aircraft, but rather hand
crafted aircraft with many minor, and some major, variations over the 39
year production history to date.

Please note that there have been a total of only eight (8) NTSB reported
accidents relating to exhaust system and/or P-lead failures. This
represents less than 1% of the total aircraft produced and has occurred
only to the 17-30A model. Of these eight failures, and unlike stated in
the NPRM, only three (3) occurred after the issuance of AD 76-23-03 R1
Amendment 39-5454 effective November 7, 1986, each separated by \~10
years. Three (3) additional accidents occurred in 1985, just prior to
the effective date of amendment 39-5454. One additional in 1977, one
year after amendment 39-2772 became effective on November 23, 1976, and
the first, on October 1976, just one month prior to the effective date
of 39-2772.

All of these accident aircraft were early year, 1970-1974; production
17-30A normally aspirated Continental powered aircraft. This is
significant, as will be shown below.

The proposed AD addressed in this NPRM should not, in its current form,
be issued for the following reasons.

\* The proposed AD includes models of aircraft not demonstrated to
possess, due to differences in design and construction, failure modes of
any accident aircraft.

\* The proposed AD is overly broad in scope of issues addressed, exhaust
systems and P-lead routing, and includes unaffected model aircraft of
substantially different design.

\* The proposed AD relies upon inaccurate and conflicting data.

\* The proposed AD provides inaccurate and conflicting data and
references, while omitting other pertinent data.

As exhaust system design and construction of Rajay turbo normalized
Lycoming powered models is substantially different from normally
aspirated Lycoming and Continental models:

The Model 17-31TC was not included.

The Model 17-31ATC should be excluded.

As electrical harness and P-lead routing are substantially different in
Rajay turbo normalized Lycoming powered models 17-31TC and 17-31ATC from
all other aircraft models, and identified exhaust system deficiencies
and failures, whether design or maintenance related, causal to
subsequent P-lead failure are non-existent and not likely to develop in
either of these model aircraft, the 17-31ATC should also be excluded.

As ALL NTSB documented exhaust and subsequent P-lead failures have
occurred in normally aspirated model 17-30A aircraft, Rajay turbo
normalized Lycoming powered model 17-31ATC should also be excluded.

Airworthiness Concern Sheet comments

Reason for Airworthiness Concern ***incorrectly*** states:

\"Seven other similar accidents occurred since 1986 when AD 76-23-03 was
amended to solve this problem\"

Comment - This is a factually incorrect statement. Five (5) accidents
occurred prior to this amendment, three (3) in 1985, two (2) prior to
that date, with only three (3) accidents following the issuance of the
amendment. Of the following three, they were separated by eight (8) and
eleven (11) years respectively; clearly a dramatic reduction in reported
accident incidence and frequency, and likely directly attributable to
the existing amendment. Of these accident aircraft, ALL were pre 1985
production model 17-30A and shared potential design and weld defects
common to these exhaust systems, with subsequent P-lead failure likely,
being routing directly aft of the exhaust system failure point.

Models 17-31TC (not included in this NPRM) and 17-31ATC (included) share
none of these attributes, as the exhaust system is of an entirely
different design.

Reference attached \"Viking Accident Reports.pdf\" for substantiating
details.

NPRM comments

1\) SUMMARY incorrectly states:

\"Airworthiness Directive (AD) 76-23-03- R1, which applies to certain
Alexandria Aircraft, LLC (Bellanca) Models 17-30, 17-31, 17-30A, 17-31A,
and 17-31ATC.\"

Comment - Model 17-31ATC is NOT included in (AD) 76-23-03- R1

2\) SUMMARY states:

\"AD 76-23-03-R1 currently requires you to inspect the muffler and
tailpipe assemblies for cracks and inspect the exhaust assembly for
freedom of movement at the ball joints.\"

Comment - Models 17-31TC and 17-31ATC DO NOT HAVE \'ball joints\' as any
part of their exhaust system.

3\) SUMMARY states:

\"This proposed AD would also require rerouting of the magneto \"P\"
leads.\"

Comment - This requirement should not be applicable to turbo normalized
models due to substantial design differences and lack of failure prone
components and welds. These models, 17-31TC and 17-31ATC, should be
exempted from this requirement; or\...

This portion of the proposed AD should be proposed in a separate AD
specific to only those models affected.

4\) SUMMARY states:

\"We are proposing this AD to detect and correct cracks in the exhaust
system\...\"

Comment - This is already addressed in AD 76-23-03-R1 and should be
addressed by revising the inspection techniques required, as an
amendment to the existing AD, not as a new, expanded in scope of items
addressed, AD.

5\) DISCUSION incorrectly states:

\"Several reports of exhaust system failures, \... on Bellanca Model
17-30 and 17-30A airplanes caused us to issue AD 76-23- 03-R1, Amendment
39-5454.\"

Comment - There are eight (8) NTSB accident reports, ALL for model
17-30A aircraft of early production year (prior to 1978-1979), when an
exhaust system design change was implemented. There are no NTSB reported
failures for late, (post 1978-1979) model 17-30A or any other model
aircraft.

6\) Relevant Service Information states:

\"We have reviewed Bellanca/Alexandria Aircraft, LLC Service Letter
B-110 \... SK1072 \... The service information describes procedures for:
\... \* rerouting the magneto \"P\" leads.\"

Comment - The Instructions provided by Alexandria Aircraft LLC are
unique and specific for other than 17-31TC and 17-31ATC aircraft, as
they detail P-lead routing not found in either of these type aircraft
and specifically only to Continental powered aircraft. Model 17-31ATC
should, as model 17-31TC, be excluded from this portion of this proposed
AD.

7\) FAA\'s Determination and Requirements of the Proposed AD states:

\"We are proposing this AD because we evaluated all information and
determined the unsafe condition described previously is likely to exist
or develop on other products of the same type design. \... This proposed
AD would also require rerouting of the magneto \"P\" leads.\"

Comment - It does not appear ALL information was evaluated, as NTSB
reports detail failures ONLY with model 17-30A. Both 17-31TC and
17-31ATC have substantially different exhaust systems lacking the \'ball
joint\' prone to failure. Further, 17-31TC (excluded) and 17-31ATC
aircraft do not have a muffler assembly, subject to internal weld
failure and inspection, on the left side of the engine. Additionally,
electrical harness routing, including P-leads, in Lycoming powered
models is up and away from exhaust system components, not down and
toward exhaust system components as are early model year 17-30A accident
aircraft. These aircraft (17-31TC and 17-31ATC), while covered under the
same Type Certificate, are not of the same \'type design\' with respect
to either exhaust system or P-lead routing. Model 17-31ATC should, as
model 17-31TC, be excluded from this AD.

8\) Costs of Compliance incorrectly states/estimates:

\"We estimate that this proposed AD would affect 1,350 airplanes in the
U.S. registry.\"

Comment - As of early 2007 there were a total of 1041 aircraft in the US
registry from a total production run of all models totaling \~1358
aircraft.

9\) Costs of Compliance incorrectly states/estimates:

\"We estimate the proposed inspection of the exhaust system would affect
1,200 airplanes \... Total cost on U.S. operators \$384,000\"

Comment - As of early 2007 there were a total of 921 aircraft in the US
registry comprised of models 17-30, 17-30A, 17-31 and 17-31A subject to
Action (1) inspections. The cost is based on 1200 aircraft and should be
revised downward to \~\$294,720.

10\) Costs of Compliance incorrectly states/estimates:

\"We estimate the proposed rerouting of the magneto \"P\" wires would

affect 1,050 airplanes \... Total cost on U.S. operators \$861,000\"

Comment - No basis is provided for the estimated quantity of aircraft
requiring the proposed P-lead Service Kit. Action (3) compliance based
on (i) 17-30A S/N 30263 through 30998, (ii) 17-31A all S/N and (iii)
17-31ATC all S/N would include a total of 972 aircraft in the US
registry as of early 2007. Whereas (iii) 17-31ATC aircraft are of
substantially differing exhaust system design and no \'unsafe condition
described previously is likely to exist or develop\' should be excluded,
this estimate should be revised downward to 854 aircraft for a total
cost on U.S. operators of \$700,280.

11\) PART 39\--AIRWORTHINESS DIRECTIVES, Sec. 39.13 \[Amended\],
Applicability

\(c\) This AD applies to the following airplane models and serial
numbers that are certificated in any category: Model 17-31ATC \... all
serial numbers.

Unsafe Condition states:

\"(d) This AD results from several accidents caused by exhaust system
failures. We are proposing this AD to detect and correct cracks in the
exhaust system, which could result in heat damage to magneto electrical
wiring and smoke in the cockpit. This failure could lead to loss of
engine power and/or a fire in the engine compartment.\"

Comment - Whereas 17-31ATC aircraft are of substantially differing
exhaust system design from those four (4) aircraft shown to have design
and/or maintenance deficiencies, and is of similar design as 17-31TC
which has not shown deficiencies and was not included in this proposed
AD, model 17-31ATC should also be excluded from applicability.

12\) Compliance states:

\"(e) To address this problem, you must do the following, unless already
done:

\(3\) For aircraft models and serial numbers listed below that do not
have Bellanca/ Alexandria Aircraft, LLC Service Kit 1067: Rerouting
Service Kit 1067: Rerouting Right Magneto \"P\" Lead installed, reroute
the magneto \"P\" leads.

\...

\(iii\) Model 17-31ATC, all serial numbers.\"

Comment - Whereas 17-31ATC aircraft are of substantially differing
exhaust system design from those aircraft shown to have design and/or
maintenance deficiencies, and is of similar design as 17-31TC which has
not shown deficiencies and was not included in this proposed AD, Model
17-31ATC should also be excluded from the proposed AD.

Submitter Commentary:

This AD proposes to include model 17-31ATC aircraft in a required P-lead
installation addressed in Service Letter B-110 requiring installation of
Service Kit SK1072, while superseding Service Letter B-104 and Service
Kit SK-1067.

SL B-104 and SK-1067 appear to be in response of eight exhaust system
failures in type 17-30A aircraft, which along with model 17-30 have been
the subject of three additional Service Letters for a total of five; all
addressing exhaust system design and/or maintenance deficiencies
possibly leading to an exhaust system failure directing gasses toward an
electrical harness containing both left and right magneto P-leads.

The first Service Letter, SL-54 dated February 2, 1970, applied to model
17-30 aircraft S/N 30006-30139 from production years 1966-1969 and
addressed muffler failure due to tight tailpipe attachment.

The second Service Letter, SL-78 dated March 15, 1973, applied to model
17-30A and 17-31A aircraft S/N\'s 73-30515 thru 73-30539 and 73-32-103
thru 73-32-111 from production year 1973. This SL addressed flexibility
of the connection of the tailpipe to engine mount with possible tailpipe
mount breakage.

The third Service Letter, SL B-101 dated May 29, 1979, applied to model
17-30A aircraft S/N\'s 79-30906 thru 79-30944 from production year 1979,
addressing a hanger bracket weld failure, after a design modification
was made to the muffler and tailpipe routing from nearly horizontal to a
more inclined angle presumably so a failed exhaust system weld would no
longer direct exhaust gasses directly toward the electrical harness, as
had happened in two prior NTSB reported cases resulting in P-lead
failures.

The fourth Service Letter, SL B-104 dated February 6, 1984, applied to
all model production aircraft prior to the SL release date. This SL, and
SK-1067, recommended replacement of both, and rerouting of the right,
P-leads to enhance ignition system redundancy. This SL and SK included
models 17-31TC and 17-31ATC aircraft; however, the instructions on the
SK drawing were specific to Continental powered aircraft where magnetos
are located in front of an air baffle, and detailed a P-lead routing
through an air baffle. The instructions were not appropriate for
Lycoming powered aircraft with rear accessory plate mounted magnetos.

The fifth and current Service Letter, SL B-110, Service Kit SK-1072 and
this proposed AD expand and combine SL B-104 and AD 76-23-03 R1
effective November 7, 1986 into a single document covering all 17 series
aircraft, exclusive of model 17-31TC. However, again the Instructions
provided with SK-1072, as with SK-1067 of SL B-104, are very specific to
Continental powered aircraft, as steps E-4, E-5, E-9 and step F are
specific to Continental engine assemblies. (Reference included SK-1072
instructions.)

Again it must be stressed that this proposed AD seems to be in response
to eight NTSB reported exhaust system failures of muffler and/or \'ball
joint\' assemblies and/or welding resulting in exhaust gasses being
directed towards an electrical harness directly aft of the point of
failure containing both left and right P-leads. All these failures were
on early, pre 1978-1979, production year aircraft. None were on 17-31 or
17-31A aircraft that share a similar exhaust system. None were on later,
post 1979, production year aircraft sharing a similar, but modified,
exhaust system also utilizing \'ball joint\' assemblies.

Failure of early year systems would direct exhaust gasses towards an
electrical harness exiting a \'Cannon\' connector parallel to the
firewall and oriented inboard and downward. Failure of later production
year systems (none yet reported) would not direct gasses directly
towards the electrical harness, as it exits the \'Cannon\' connector
perpendicular to the firewall and above the point of failure.

Both the Lycoming powered 17-31TC (not included in either AD) or the
17-31ATC (not included in AD 76-23-03 R1, but proposed for this AD)
Rajay turbo-normalized aircraft have an entirely different exhaust
system that includes neither the left side muffler or ANY \'ball
joints\' shown to be failure prone and exhibit an \"unsafe condition
described previously \[is\] likely to exist or develop on other products
of the same type design\" as the exhaust system IS NOT OF THE SAME TYPE
DESIGN.

SL-54, SL-78, SL B-110, AD 76-23-03-R1 and this proposed AD all address
some failure mode of hanger, mount, support, muffler, tailpipe,
resonator, ball joint, weld, or crack formation in the exhaust system of
ALL AIRCRAFT MODELS EXCEPT THE 17-31TC AND 17-31ATC; neither of which
have any NTSB reported failures. Particular stress is placed on
inspection of internal welds in affected models. The exhaust systems of
17-31TC and 17-31ATC models contain no internal welds.

Attached are a number of jpg\'s of various model year 17-30A and
17-31ATC aircraft. Following comments reference these jpg\'s to allow
visual reference of engine and exhaust system component locations and
construction details.

72-1730A -- Full left engine and exhaust view (tailpipe removed). Note
general horizontal orientation of muffler/heat exchanger assembly. Note
downward and inboard orientation of Cannon connector and cable exit
parallel to firewall, lack of firesleeve on connector or fuel supply
line just below Cannon connector.

72-1730A-1 -- Partial left view of engine and exhaust system. Note
general horizontal orientation of muffler (no heat exchanger) assembly
with ball joint attached tailpipe. Note downward and inboard orientation
of Cannon connector and cable exit parallel to firewall, firesleeve on
Cannon connector and unshielded fuel supply line just below Cannon
connector. Note proximity of electrical system components to exhaust
system.

72-1730A-2 -- View of same aircraft as above showing spring attached
tailpipe to allow flexibility of tailpipe to muffler assembly at ball
joint.

72-1730A-3 - View of same aircraft as above showing ball joint
construction details.

72-1730A-4 - View of same aircraft as above right side full engine and
exhaust system with muffler/heat exchanger, ball joint and tailpipe.

72-1730A-5 - View of same aircraft as above left side muffler assembly
with internal exhaust pipe weld to manifold.

79-1730A - Full left engine and exhaust view of later model (post
1978-1979 production change) showing muffler/heat exchanger at an
increased downward angle. Note cable harness exit perpendicular to
firewall and axially with Cannon connector to increase spacing between
muffler-tailpipe ball joint assemble. Note too a failure of a muffler or
ball joint weld would direct exhaust gasses down and away from
electrical harness. Here all welds are external.

75-1731ATC -- Oblique full left engine and exhaust system view. Note
downward orientation of exhaust manifold to mate with waste gate
assembly below Rajay turbo assembly. Note orientation of fireshielded
harness exit from Cannon connector, parallel to firewall and upward,
away from exhaust system components. P-leads are contained within this
harness. Note additional protection provided by shielding of fuel supply
line below Cannon connector.

73-1731ATC-2 -- Detail of tailpipe external flange weld at exit of Rajay
turbo.

73-1731ATC-4 -- Detail of external welds of tailpipe to waste gate
assembly.

73-1731ATC-5 -- Detail of external welds of exhaust manifold assembly
and transition to waste gate assembly inlet.

73-1731ATC-8 -- Detail of external welds on rear of right side heat
exchanger and transition to waste gate assembly inlet.

73-1731ATC-9 -- Detail of external welds of right side exhaust pipes to
heat exchanger assembly.

From these pictures it should be quite clear there is little similarity
between Model 17-31ATC and all other model aircraft subject to recurrent
inspections detailed in SL B-110, required by AD 76-23-03 R1 and
proposed in this NPRM. It should also be clear there is a substantial
increase of separation of the electrical harness from any exhaust system
component. Note too that the exhaust system for the 17-31ATC is
completely independent of the airframe, moving with and supported
entirely by the engine, thus eliminating the need for an articulated
tail pipe. This is not a system prone to failure, especially at a point
near critical electrical system components. Contrast this with other
models requiring a ball joint to allow for continuous motion of the
muffler assembly, attached to the engine, relative to the tailpipe,
attached to the airframe.

The data provided in this NPRM and available NTSB data do not support
the inclusion of any production year model 17-13ATC aircraft in this AD.

This model should be excluded.

Attached please find the following 21 supporting documents:

SL-54.pdf, SL-78.pdf, SL B-101.pdf, SL B-104.pdf, SL B-110.pdf,
SK-1072.pdf, Viking Accident Reports.pdf,

72-1730A.jpg, 72-1730A-1.jpg, 72-1730A-2.jpg, 72-1730A-3.jpg,
72-1730A-4.jpg, 72-1730A-5.jpg, 79-1730A.jpg, 75-1731ATC.jpg,
73-1731ATC-2.jpg, 73-1731ATC-4.jpg, 73-1731ATC-5.jpg, 73-1731ATC-8.jpg,
73-1731ATC-9.jpg