Propeller Change

1
Propeller Change

• Fully define alteration
• Aviat A-1B Husky, TCDS A22NM, Part 23 dated
  February 1, 1965 as amended by 23-1 thru 23-31
  (Normal Category) and FAR 36 amended thru 36-12,.
  FAR 21 amended thru 21-57. )
• Modification to Propeller, Spinner, Engine Crank,
  governor, and prop control cable, Flight Manual
  Operating Limitations.
• Specifics
• Increase from 80 to 82 inch prop, no reduction
  in RPM.
• Change from constant speed to fixed pitch.
• Must modify crank to plug orifices (search find
  ADs on crank)
• Remove governor and install plate.
• Remove Placard Limitation
• Add FMS for Limitation, Normal, Emergency Ops,
  Etc

2
Major/Minor Design Change Issues

• Is it a Major Change in Type Design?
• Is this change appreciable?
• Yes the prop governor is removed, the control is
  no longer in the cockpit. No Manifold Pressure
  gauge on panel. This is an appreciable change at
  Product level. Effect on operational
  characteristics (Take-off performance)
• It could also be an Acoustical change per FAR
  21.93
• Was aircraft registered and flown prior to
  January 1, 1955
• Is the aircraft being altered as part of a float
  mod (temporary)
• Under some instances Float planes and ski planes
  may be exempt from Noise rules.
• Is there a change in the dB level output of the
  aircraft.
• Tip Mach Number
• Performance
• Weight

• Directorate may flag this as a significant
  project.

3
Certification Issues

• Changes that detrimentally affect takeoff
  performance are probably Major (STC).
• Is there a change in engine operating limits,
  like RPM or avoid continuous operation
  limitations.
• Placard required "AVOID CONTINUOUS OPERATIONS
  BETWEEN 2000-2250 RPM" (On original Prop instl.)
• If there is a change in the basic engine
  configuration outside of previously approved
  data?
• Engine and Propeller Combination should be
  certified on a previous installation.

THIS SPECIFIC MODIFICATION SHOULD BE A STC
4
STC(Points of Discussion)

• Determine if the STC will be one-time or
  multiple.
• Level of Documentation (photos vs. drawings)
• Multiple STCs will require production quality
  drawings
• STC Application
• Send to the Geographical ACO (FAA Form 8130-12)
• Anchorage ACO in the case of Juneau applicants
• Cover Letter submitting application
• Draft Project Specific Certification Plan (PSCP)
• Compliance Checklist.

5
STC(Points of Discussion)

• Project Specific Certification Plan
• Define project (Make/Model/TCDS/Change
  description)
• Serial No. if one-time
• Use of Designees
• Compliance Checklist
• Multiple STCs will require production quality
  drawings
• One-time is okay with photos
• Schedule and responsibilities
• Compliance Checklist
• Larger more in-depth version of checklist
  provided.
• Define method of compliance with regulations
  (Analysis, Drawings, Tests)

6
STC(Points of Discussion)

• Typically Requires Flight Test
• Performance
• Noise
• Flutter (test VD)
• Cockpit layout (removal of manifold gauge)
• Obtain Type Inspection Authorization.
• ICA
• Would need to address the AD on the crank.
• Alternate Method of Compliance (AMOC)
• Needs approval by AD issuing ACO
• Flight Manual Supplement (needs ACO Approval)
• Change in Limitations.
• Change cockpit layout.
• Change in Normal / Emergency procedures.

7
Acoustical Issues(Points of Discussion)

• If we have a acoustical change it may be possible
  using the appendix G handbook to determine what
  the acoustical impact is without a noise test in
  many cases. (is there a dB level quoted in TCDS
  or Flight Manual)
• If not, a Noise Test needs to be proposed and
  scheduled. Usually a Noise DER is required (In
  Alaska there are times of the year that noise
  tests are difficult due to the cold weather)
• If performance is affected, a flight test will
  be required
• The flutter characteristics can be checked by
  testing to Vd or by a flutter analysis and a test
  to redline (Vne).
• If the prop is longer, we need to check ground
  clearance. (two conditions)
• If the Propeller DER imposes a limitation on
  certain RPM ranges those limits will have to be
  imposed using placards in the cockpit.

8
QUESTION ANSWER OR OPEN DISCUSSION