1. FAR 23, Modifications and Flight Test
Tony Morris
Test Pilot, CAA

2. Contents: CAA Test Pilot – Who & Why? The need for testing
Types of modifications
Possible effects on the aircraft
Examples of test programmes
The ‘approaches’ to flight testing
Pilot qualifications
Where to find information
Questions

3. CAA Test Pilot Position – Who & Why?
Required to ensure new/modified aircraft properly tested
RAAF for 13 years
Test flying professionally since 1990
Graduate of the Empire Test Pilots School (UK)
Senior Fixed-Wing Test Pilot RAAF
Civil test pilot since 1995
CAA Test Pilot since 2001
125 types
10,200 flying hours

4. “Why do we need to test this modification”?
Legally required by legislation
Need approval to sell commercially
Need to define new or modified parameters
Need to define new or changed performance

5. Types of aircraft modifications:
External
Internal
Powerplant

6. Possible effects on the aircraft:
Handling qualities
Systems
Performance

7. (How the aircraft ‘flies’)
Handling Qualities
(How the aircraft ‘flies’)
We need to test if any of the following have changed:
Stall speed or characteristics
Lateral/Directional (modified stability – IFR?)
Longitudinal (trim, control, damping)
Minimum control speed (multi-engine)
Takeoff and landing

8. Systems Modifications:
We may need to test if any of the following are modified:
Powerplant
Controls
Displays
Pilot Interface
Lighting
“Cockpit Space and Comfort”
Field-Of-View
Pilot Workload

9. Performance Testing
We will need to test if any of the following have changed:
Takeoff
Climb
Landing
Balked Landing
Inflight
Roll rate
Engine-Inoperative/Abnormal
Restricted vs. Normal Category?

10. Example Flight Test Programmes
Taken from personal test flying
Still current in ‘real’ test flying!
Not just an ‘office’ type with no ‘real-world’ experience!

11. Cessna 182 FLIR Modification
Takeoff and Landing handling qualities
Stall speed verification
Lateral and Directional stability and control
Roll rate confirmation
Systems tests

12. Geosurvey Pods – Cresco
Lateral/Directional handling
Stall speed re-validation
Roll rate and handling
Takeoff, climb and landing performance re-validation

13. Powerplant Change – Air Tractor 301
Takeoff and landing performance
Takeoff and landing handling
Longitudinal, Lateral Directional handling
Engine handling and in-flight restart
Stall speed re-validation

14. Asymmetric Stores Carriage – Lear 35
Takeoff and landing handling (crosswind and trim limit)
Climb performance decrement
High-speed handling, stability and control (M 0.78)
Low speed handling and AoA stability
Single-engine handling and minimum control speed
Flutter
Lateral/Directional handling, roll rate
Qualified personnel?

15. Where do I find out what I need to test?
FAR 23 Subpart B - Flight
Flight Test Resources:
CAA – we are here to help!
FAA Regulatory & Guidance Library (RGL)
( > Regulations and policies > RGL)
Advisory Circulars support FAR 23
You are not alone!
Ask for help – earlier rather than later!

16. The two approaches to flight test:
The ‘easy way’:
Ask for help, take advice, do the tests ‘right’ first time in accordance with the regulations
The ‘hard way’:
Don’t ask, hire the wrong people, get it wrong, complain when CAA fails to approve your mod – spend more money!
Quick check – is the CAA tough?
CAA is probably the most ‘user-friendly’ regulatory authority going around!
Engineering support ‘as good as it gets’

17. Planning a Flight Test Programme
‘Go it alone’; find out later?
What can CAA offer?
CAA Test plan review
Flight test ‘oversight’
CAA Flight Test ‘witness’
Test pilot approval (where required)
Report submission – quality?
CAA Audit?
Required in certain cases
Scope will depend on report, results and task
Could range from 10% - 100%

18. Getting the ‘right’ test pilot
Hire the RIGHT pilot, not just the one who’s there
Not every pilot or engineer can perform flight test
Correct background/experience
Disciplined, methodical, thorough
Able to anticipate and understand FAR 23 requirements
Willing and able to take advice and direction
Reliable and consistent test techniques
Able to convert what they have ‘seen’ to a readable, coherent format
Interface between you and the CAA
Audit?

19. Some Useful Advisory Circulars
AC 23-8B: Flight Test Guide for Certification of Part 23 Airplanes
AC 23-14: Type Certification Basis for Conversion from Reciprocating Engine to Turbine-Powered Part 23 Airplanes
AC 23-17B: Systems and Equipment Guide for Certification of Part 23 Airplanes and Airships
AC C: Equipment, Systems, and Installations in Part 23 Airplanes
AC BInstallation of Electronic Display in Part 23 Airplanes

20. Helicopters? Part 27 Normal category Part 29 Transport category
Associated AC’s

21. FAR 23 Subpart B - Summary General Performance Flight Characteristics
Controllability and Manoeuvrability
Trim
Stability
Stalls
Spinning
Ground and Water Handling Characteristics
Miscellaneous Flight Requirements

22. Performance
23.45 General Stalling period Takeoff speeds Takeoff performance Accelerate-stop distance Takeoff path Takeoff distance and takeoff run Takeoff flight path Climb: general Climb: all engines operating Takeoff climb: one-engine inoperative Climb: one engine inoperative Enroute climb/descent Glide: Single-engine airplanes Reference landing approach speed Landing distance Balked landing.

23. Controllability and Maneuverability
General Longitudinal control Directional and lateral control Minimum control speed Acrobatic maneuvers Control during landings Elevator control forces in maneuvers Rate of roll.
Trim
Trim.

24. Stability Stalls Spinning
General Static longitudinal stability Demonstration of static longitudinal stability Static directional and lateral stability Dynamic stability.
Stalls
Wings level stall Turning flight and accelerated turning stalls Stall warning.
Spinning
Spinning.

25. Ground and Water Handling Characteristics
Longitudinal stability and control Directional stability and control Operation on unpaved surfaces Operation on water Spray characteristics.
Miscellaneous Flight Requirements
Vibration and buffeting High speed characteristics.

26. Questions?
“But it’s only a MINOR modification!!!!”