IA Public Training Major Minor Type Design Change by Mike Heusser, ACE115N Peter Pupator, ACE115N Ma

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IA / Public Training Major / Minor Type Design
ChangebyMike Heusser, ACE-115N Peter Pupator,
ACE-115NMark Wilson, AAL-235
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Major or Minor - Design Change?
The I/A is responsible Major/Minor (change in
Type Design) decision (per 14 CFR 21.93(a)) in
the FAA Order 8300.10, CHG 16. How does an IA
make the decision for an Major or Minor change to
Type Design?
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INTRODUCTION

• Goals
• 2 separate methods for determining major/minor.
• Review 14 CFR 21.93(a)
• Flow of thoughtThe Flow
• Definitions of critical concepts
• Rules for Alteration vs. STC
• Discussion of Systems Failure Approach
• Review Examples
• Discussion

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Major / Minor Design Changes

• FAA Order 8300.10 CHG 16, Vol.2, Page 1-13,
  Figure. 1-2, Flow Chart.

Is this a Major Design Change per CFR 21.93(a)?
YES - STC
NO Alteration
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14 CFR 21.93(a)
21.93 Classification of changes in type
design. (a) In addition to the changes in type
design specified in paragraph (b) of this
section, changes in type design are classified as
minor and major. A minor change is one that
has no appreciable effect on the weight, balance,
structural strength, reliability, operational
characteristics affecting the airworthiness of
the product. All other changes are major
changes (except as provided in paragraph (b) of
this section. (b) Part 36 of this chapter.
(Acoustical change) (c) Part 34 of this
chapter. (Emissions change)
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14 CFR 21.93(a)The Flow
Is there a change to Type Design?
Is the change Appreciable?
Is the change at the Product level?
Does the change effect (any ) of these (critical
five) -weight, -balance -strength,
-reliability, -operational characteristics?
Does the change affect Airworthiness (safe
flight) ?
NO answer to any box results in Minor Change to
Type Design.
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What is Type Design?
21.31 Type Design The type design consists of
(a) The drawing and specification and a
listing of those drawings and specification,
necessary to define the configuration and the
design features of the product shown to comply
with the requirements of that part of the
subchapter applicable to the product ( CAR 3,
Part 23, , 33, etc) (b) Information on
dimensions, materials, and processes necessary to
define the structural strength of the product.
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What is Type Design? - cont
21.31 Type Design (c) The Airworthiness
Limitations section of the Instruction Continued
Airworthiness (ICA). (Life Limited parts,
Inspection Intervals, Replacement Intervals,
Lubrication Intervals, Installation / Removal
Methods etc.) (d) not germane to discussion.
(e) not germane to discussion.
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What is Type Design? - cont

• Type Design is the body of information (drawings,
  manuals, specifications, etc) developed (during
  the Certification process) by the OEM, to show
  compliance to the (cert. basis) regulations.
• It is unique for each aircraft make/model.
• The physical aircraft is not the Type Design.
• The physical aircraft conforms to Type Design
  when it receives its Airworthiness Certificate
  (S/nbirth).
• Any major changes to the Type Design must undergo
  a Certificate process -- 21.97, 21.113.

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Critical Five
Weight Is there an increase or decrease to the
weight limitations? - minimum flying weight,
minimum fuel weight, landing weight, take-off
weight. Balance Is there an increase or
decrease to the CG limitations? (including
maximum forward, and aft limits, or the shape of
a variation between weights. - the
doghouse. - functional use for
(typical/minimum) payload applications
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Critical Five cont
Structural strength Is there a change to the
product strength, either by a material change, a
geometry change or a change in the load magnitude
or path? - large cutouts in semi-monocoque
structure. - geometry change in rag/tube
structure. - stiffness changes for stronger
material (spring rate). Reliability Is there a
change in the failure mode, lifetime or ability
of the product to meet its intended function. -
brake / pad and rotor combinations. - shear
coupling (weak point) in engine accessory.
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Critical Five cont
Operational characteristics Is there a change
to performance, stability control, take-off and
landing, or handling of the aircraft. -
unusual pilot skill - stall / spin
characteristics - airspeeds
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What is Appreciable?

• Use Judgment, be Flexible and be Rational.
• Requires intimate knowledge and experience with
  the Type Design (make/model).
• Change for the better (conservative) may be
  minor!
• Cross tube addition on landing gear (not
  effecting landing loads) makes it stronger.
• Regarding measurements appreciable must be
  determined with the appropriate measuring tool.
• Inch / feet tape wing span Dial Calipers
  sheet metal thk.
• Do not use mA precision for appreciable
  determinations in power consumption for a radio
  change.
• Determine tolerances prior to measurement.
• Use gauges accuracy supplied in the aircraft
  (temperature, ammeter, pressure, RPM etc.) to
  determine change.
• All that counts cannot be counted, all that is
  countable does not count.

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What is Airworthiness?
Q1 Is the Aircraft in a condition for safe
flight? (Flight - includes taxi, take-off, climb,
cruise, descent and landing, including a crash
landing) Q2 Does the aircraft meet its current
approved Type Design? Any modification (to Type
Design) will invalidate Q2 ? Only Q1 needs to be
asked in the flow.
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What is Product?

• Product is
• Aircraft, Engine, or Propeller for which a Type
  Certificate has been issued.
• Also includes Parts, materials, and appliances,
  approved under the TSO system/.
• Must be taken as a whole, . At the product
  level!
• Must take into account the intended use. (VFR
  day, IFR day night, Operations Rules etc)
• May take into account all variant model and
  serial numbers under that TCDS.
• - Include optional equipment.
• - What is the change to type data?

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14 CFR 21.93(a) The Flow revisitedRemember A
NO answer to any box results in Minor Change to
Type Design.
Is there a change to Type Design?
Is the change at the Product level?
Is the change Appreciable?
No
No
Yes
Yes
Yes
Yes
Yes
Major Change To Type Design, aTC, STC
Does the change effect (any ) of these (critical
five) -weight, -balance -strength,
-reliability, -operational characteristics?
Does the change affect Airworthiness (safe
flight)?
No
No
Repair/Alteration
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New Concept for Systems Repairs/Alterations)Eff
ect on Safety Approach
For Systems Alterations the following may be
useful.
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Effect on Safety Approach
Define Alteration Determine Failure Type
Evaluate Outcome of Failure
No / Minor Safety Effect
Minor Change to Type Design
Major / Hazardous/ Catastrophic Safety Effect
STC
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What is the impact on safety when the
modification fails?
No Safety Effect Failure Conditions that would
have no affect on safety (that is, Failure
Conditions that would not affect the operational
capability of the airplane or increase crew
workload). Minor Failure Conditions that would
not significantly reduce airplane safety and
involve crew actions that are well within their
capabilities. Minor Failure Conditions may
include a slight reduction in safety margins or
functional capabilities, a slight increase in
crew workload (such as routine flight plan
changes), or some physical discomfort to
passengers or cabin crew.  
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Effect on Safety Approach cont

• See AC 23.1309-1C for definitions of
• Major
• Hazardous
• Catastrophic
•  

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Discussion

• Examples
• Radio change (5 W to 10 W transmit) in a CAR 3
  aircraft.
• Paint a Cirrus SR-22 with another paint (color
  and type)?
• Addition extended baggage.
• Installation of larger alternator and
  consumables.
• Installation of electrical system in aircraft
  that had none prior. VFR day/night.
• Fabrication of a 24 wing tip extension.

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QUESTION ANSWER OPEN DISCUSSION