20180002829 · X-57 and Whirl Flutter Discussion

NASA · 2018

Open the PDFPublic domain · NASATechnical Reports

Overview

No abstract available

Pages: 11

Key points

Whirl flutter is a phenomenon historically linked to the Lockheed Electra mishap and remains a topic of research due to its implications in propeller propulsion.
The X-57 project aims to achieve a 5x reduction in energy use compared to the original Tecnam P2006T at 175 mph, with propulsion efficiency increasing from 28% to 92%.
The X-57 project has secondary objectives including a 30% reduction in total operating costs and zero in-flight carbon emissions.
Challenges in whirl flutter research include the effects of variable propeller dynamics on flutter margins and the need for advanced testing methods to characterize engine mount damping.
The X-57 project involves multiple modifications to validate distributed electric propulsion technologies through ground and flight testing.

Frequently asked questions

What is whirl flutter?

Whirl flutter is a phenomenon associated with propeller propulsion that can affect flight safety, historically linked to the Lockheed Electra mishap.

What are the primary objectives of the X-57 project?

The primary objective of the X-57 project is to achieve a 5x lower energy use compared to the original Tecnam P2006T at 175 mph, along with improved propulsion efficiency.

What are the secondary objectives of the X-57 project?

Secondary objectives include a 30% reduction in total operating costs, zero in-flight carbon emissions, and a 15 dB reduction in community noise.

What challenges does the X-57 project face regarding whirl flutter?

Challenges include understanding variable propeller effects on whirl modes, the need for environmental chamber testing to characterize engine mount damping, and the complexities of flight test planning.

Who are the key partners involved in the X-57 project?

Key partners include NASA Armstrong Flight Research Center, NASA Langley Research Center, Empirical Systems Aerospace, and Xperimental LLC.

Document

X - 57 and Whirl Flutter Discussion

Kia Miller and Roger Truax Aerostructures Branch NASA Armstrong Flight Research Center Edwards, CA Aerospace Flutter & Dynamics Council Spring 2018 Savannah, GA

Whirl Flutter Background

• Whirl flutter is most commonly associated with

Lockheed’s Electra fatal mishap

• Research, testing and new analysis techniques

seemed to solve the issue (1960s)

• Propeller propulsion is still an area of interest today

– Advanced propellers a current area of CFD research

– Electrically enhanced propulsion seems to be an area of

interest in the industry

• Whirl flutter research seemed to cap out in the

1960s, yet our computational capabilities have

greatly increased

Photo Credit: NASA

X - 57 Objectives and Tecnam P2006T/Wing Overlay

Primary Objective Cruise Motor • Goal: 5x Lower Energy Use (Compared to Original P2006T @ 175 mph) X - 57 Wing • Internal Combustion Engine vs Electric Ribs/Spars Propulsion Efficiency changes from 28% to 92% (~3.3x) • Synergistic Integration • Propulsion airframe integration provides higher cruise motor efficiency and cruise optimized wing Hi - lift Motors Pod Structure Derivative Objectives • ~30% Lower Total Operating Cost • Zero In - flight Carbon Emissions P2006T Wing Secondary Objectives • 15 dB Lower community noise P2006T Fuselage • Flight control redundancy and robustness (As Delivered) • Improved ride quality X - 57 Key Partners: • Certification basis for Distributed Electric NASA ARFC, NASA LaRC Propulsion (DEP) technologies Empirical Systems Aerospace ( ESAero ) Xperimental LLC, CA.

X - 57 Project Approach

Mod 1 Mod 3 DEP wing development and Mod 2 fabrication Ground validation of DEP high lift system Mod 4 Ground and flight test validation of electric Flight testing of motors, battery, and Flight test electric motors baseline Tecnam Flight test with integrated DEP instrumentation.

relocated to wingtips on P2006T motors and folding props DEP wing including (cruise motors remain in wing - nacelles (but no DEP Goals: tips).

motors, controllers, or Goals: • Establish Baseline folding props).

• Establish Electric Power Tecnam Performance System Flight Safety • Pilot Familiarity • Establish Electric Tecnam Retrofit Baseline Mod 1 Achieves Secondary Objectives Achieves Primary Objective of • DEP Acoustics Testing High Speed Cruise Efficiency Mod 2 • Low Speed Control Robustness • Certification Basis of DEP Technologies Mod 3 Mod 4

Challenges Involving Whirl Flutter

• Variable prop effects on whirl

modes and flutter margins

• Electric motors have less

vibrations, but motor mount

dampers tend to stabilize whirl

flutter

• Should blade frequencies

effect flutter results?

Challenges Involving Whirl Flutter

acquires pitch and yaw of prop

system

• Gyroscopic whirl modes not

included in ground testing

• Characterizing the damping of

the engine mount requires

environmental chamber testing

Challenges Involving Whirl Flutter

• Flight test planning with

variable speed motors and

variable blade pitch

• Monitoring flight data with

harmonics

• Monitoring flight data with EMI

Challenges Involving Whirl Flutter

• Are there future needs in the

field?

• Can the aircraft industry benefit

from active suppression or

smart materials?

Discussion: Challenges Involving Whirl Flutter

Thank you.

Kia Miller Roger Truax kia.d.miller@nasa.gov roger.a.truax@nasa.gov 661.276.3712 661.276.2230 Aerostructures Branch NASA Armstrong Flight Research Center Edwards, CA