# Presentation: 531187

## IA / Public Training Major / Minor Type Design ChangebyMike Heusser, ACE-115N Peter Pupator, ACE-115NMark Wilson, AAL-235 	

- IA / Publicr Training, March  2004

## 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**?

- IA / Publicr Training, March  2004

## INTRODUCTION

- _Goals_
- 2 separate methods for determining major/minor.
- Review 14 CFR 21.93(a);
- Flow of thought...”The Flow”...
- Definitions of critical concepts
- Rules for Alteration vs. STC
- Discussion of Systems Failure Approach
- Review Examples
- Discussion

- IA / Publicr Training, March  2004

## 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

- IA / Publicr Training, March  2004

## 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)*
* *

- IA / Publicr Training, March  2004

## 14 CFR 21.93(a)‘The Flow’

- Is there a
- change to
- Type Design?

- Does the change
- effect (*any* ) of these
- (**critical five**)
- -weight, -balance
- -strength,
- -reliability,
- -operational
- characteristics?

- Is the change
- Appreciable?

- Does the change
- affect
- Airworthiness
- (safe flight) ?

- Is the change
- at the
- Product level?

**NO** answer to _any_ box results in Minor Change to Type Design.

- IA / Publicr Training, March  2004

## 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.

- IA / Publicr Training, March  2004

## What is Type Design? - con’t

- § 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.

- IA / Publicr Training, March  2004

## What is Type Design? - con’t

- 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/n...birth).
- Any major changes to the Type Design must undergo a Certificate process --  §21.97, §21.113.

- IA / Publicr Training, March  2004

## 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*

- IA / Publicr Training, March  2004

## Critical Five – con’t

_*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.*

- IA / Publicr Training, March  2004

## Critical Five – con’t

_*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*
*  *

- IA / Publicr Training, March  2004

## 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 *m*A 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.

- IA / Publicr Training, March  2004

## 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’.

- IA / Publicr Training, March  2004

## 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*_*?*

- IA / Publicr Training, March  2004

## 14 CFR 21.93(a) The Flow – revisitedRemember: A NO answer to any box results in Minor Change to Type Design.  

- Is there a
- change to
- Type Design?

- Does the change
- effect (*any *) of these
- (**critical five**)
- -weight, -balance
- -strength,
- -reliability,
- -operational
- characteristics?

- Is the change
- Appreciable?

- Does the change
- affect
- Airworthiness
- (safe flight)?

- Is the change
- at the
- Product level?

- No

- Yes

- Yes

- Yes

- Yes

- Yes

- Major
- Change
- To
- Type
- Design,
- aTC,
- STC

- Repair/Alteration

- No

- No

- No

- IA / Publicr Training, March  2004

## New Concept for Systems Repairs/Alterations)Effect on Safety Approach

- For Systems Alterations the following may be useful.

- IA / Publicr Training, March  2004

## Effect on Safety Approach

- Define Alteration &
- Determine Failure Type

- Evaluate Outcome
- of Failure

- No / Minor
- Safety Effect

- Major /
- Hazardous/
- Catastrophic
- Safety Effect

- STC

- Minor Change to
- Type Design

- IA / Publicr Training, March  2004

## 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.

- IA / Publicr Training, March  2004

## Effect on Safety Approach – con’t

- See _AC 23.1309-1C_ for definitions of;
- Major
- Hazardous
- Catastrophic
*** ***

- IA / Publicr Training, March  2004

## 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.

- IA / Publicr Training, March  2004

## QUESTION & ANSWER 

**OPEN DISCUSSION**

- IA / Publicr Training, March  2004