Honda Aircraft Company October 17, 2014 Mr. Earl Lawrence FAA Small Airplane Directorate 901 Locust Street Kansas City, MO 64106

Honda Aircraft Company 6430 Ballinger Road Greensboro,
NC 27410 USA T e
l : 336

.662

.0246 F ax: 336

.662.0852 GN-9438-14-011 Subject: Honda Aircraft Company Petition for Exemption

to 14 CFR Part 23, §23.181(b) for the Honda Model HA-420 Dynamic Stability Compliance; FAA Project TC9438AT-A Reference:
(1) Honda Letter GN-9438-14-009 dated September

2, 2014 (2) FAA Small Airplane Directorate Letter dated September 24, 2014 Dear Mr. Lawrence, Reference (1) submitted
in accordance with 14 CFR Part 11 Honda Aircraft Company's petition for an exemption

to the requirements

of 14 CFR Part 23, § 23.181 (b) for the Honda Mode

l HA-420
asrelated to dynamic stability compliance. Reference (2) provided comments and request for additional information

. Honda ha s updated our position

,addressed your comments, and discussed this update with Mr. Lowe ll Foster from youroffice. Attached

is our updated position. If youhave any questions

orcomments
onthis request, please feel free to contact Mr. Clay Harden

at (336) 662-0246 ext. 143 3 or myself at (336) 662-0246 ext. 1670. Sincerely

, Randy Griffi th Honda Aircraft Company Division Director, Certification Enclosure Cc: Don Yo ung

,FAA Atlanta ACO HONDASUBJECT: Dynamic Stability Compliance STATEMENT
OF ISSUE: Honda Aircraft Company (Honda) located

in Greensboro, North Carolina would like to use the Dutch roll damping requirements

of 14 CFR Part 25.181(b) Dynamic Stability
to show regulatory compliance
for certification

of the HA-420 airplane during takeoff prior to the initiation

of landing gear retraction and during landing with the airplane configured
for landing. An exemption using

a pilot evaluation

is requested

to confirm that no unsafe condition exists with the airplane's handling characteristics
with the yaw damper disengaged during takeoff and landing. The Dutch roll damping requirements

of 14 CFR Part 23.181 (b) at Amendment 23-62 would be met for the majority
of the envelope including takeoff and landing
at field elevations below approximately 5,000 feet. BACKGROUND: The Part 23 requirement
for Dutch roll oscillations

to be damped
to 1/10 amplitude

in 7 cycles was written,

in part, as a result of few small airplanes having yaw damper systems. In contrast, nearly all current 14 CFR Part 23 jet airplanes are type certificated with yaw dampers since the ride quality must be tailored
to maximize passenger comfort and safety. Part 25 airplanes are typically flown by pilots type rated for that specific airplane. Small, non-turbojet Part 23 airplanes generally do not require

a type rating, and this is the reason that the Part 23 requirements
are and should be more stringent for airplane handling characteristics. Larger aircraft typically employ

a more complex "series" yaw damper that responds without causing rudder pedal motion. Series yaw damper engagement may be employed throughout

all flight phases including landing and touchdown. The HA-420 airplane uses a conventional reversible rudder control system, manually cable-driven
via the rudder pedals. The "parallel" yaw damper utilizes an electronic rudder servo, which generates torque, moving both the pilot's pedals and the rudder
to augment stability. The yaw damper

is typically engaged

in flight to assist
in suppressing
the Dutch Roll mode. However, the yaw damper also tends to suppress pilot crosswind rudder inputs, and increase the rudder pedal forces required

to generate those inputs. Therefore,

the yaw damper

is disengaged during takeoff and landing
to minimize workload. The in-service history
of the 4 flight test aircraft (F1, F2, F3, F4) as well as the first production aircraft (P11) has shown that the airplane handling qualities are not objectionable with the yaw damper off during takeoff and landing. The quantitative analysis showed that the airplane damping

is slightly less than the requirement

to damp to 1/10 amplitude

in 7 cycles at high field elevations. CONCLUSION: The Model HA-420 lateral directional dynamic stability

is positively damped and acceptable during expected operations with the yaw damper off. Operations

of this type are very brief, and are limited to a small fraction
of the operational flight envelope.The reduced damping

of the non-augmented airplane

is mitigated
bythe following compensating features: •Predictable handling qualities withwell harmonized flight control forces. •The Airplane Flight Manual (AFM) will require the yaw damper
tobe engaged for all flight phases excepttakeoff and landing. •The Crew Alerting System (CAS) logicwillalertthe crew,
intheform of CAS messages, anytimethe yaw damper

isnot engaged during flight other thanthe takeoff and landing phases. •The yaw damper

is automatically engaged after takeoff andwill automatically disengage upon landing. TheAFM procedurewill direct the pilotto manually disengage the yaw damper priorto landing. • During the short duration thatthe yaw damper

isnot engaged during each flight, the pilotis fullyinthe airplane control loop. The un-augmented dynamic stability

is positive and anyunwanted residual oscillations are easily controllable

bythe pilot Granting this exemption provides

alevelof safety atleast equaltothat provided under14 CFR Part 23.181 (b) for the following reasons: •The yaw damper

is required byAFM procedure andwill provide

a highly damped Dutch roll responsefor all flight phases when engaged. Thiswill decrease pilot workload and improve safety. • Testing shows that,inthe unlikely eventofa yaw damper failure, the autopilot roll channel provides highly damped Dutch roll response

atall altitudes
uptothe maximum operating altitude. •Inrareinstances when neither autopilot nor yaw damper areavailable, theAFMwill provide

amaximum "retreat" altitude where natural Dutch roll damping meetsthe basic rule (damping

to1/10 amplitude

in13 cycles). Company testshave shown, and certification testingwill verify thatthe aircraft can safely descend

tothis retreat altitude from maximum operating altitude, and also descend from the retreat altitude
to landing. •Relative

tothe objectionable workload with
a parallel yaw damper engaged, disengaging
the yaw damper for crosswind

or gustytakeoffs and landings enhances safety. •As partof flight testing using normal procedures, companytest pilots andDER pilots evaluated numeroustakeoff and landings withthe yaw damper disengaged. Testing consistently showed the natural Dutchroll damping resulted

in acceptable workload anddidnot adversely affect safety. Furthermore,

inthe course
of certification testing,FAA pilotswillhave ample opportunity

toevaluate and confirm workload acceptability acrossthe spectrum

of atmospheric conditions naturally found during flight testing. Granting this exemption

isinthe public interest, for the following reasons: •Forthe airframe
to inherently provide the required damping would result
alessfuel efficient design. The aircraft was designed

tocruise efficiently

at high speed and high altitude. When the necessarylevelof safety canbe provided, maximum efficiency

isinthe public interest •Amore complex and expensive series yaw damper system design

isnot typical for this classof aircraft Yearsof industry fleet experience withthis styleof yaw damper show thatthe necessarylevelof safety canbe achieved. Minimizing expenseand complexity areinthe public interestConsidering these compensating features, safety, and the public interest, Honda believes an exemption

to 14 CFR 23.181 (b) Amdt 23-62
is warranted lor the HA-420. The aircraft

is marketed

to a global customer base. Honda Aircraft Company will pursue foreign certifications shortly alter receiving FAA certification.

It is anticipated that our customers outside the United States will exercise the privileges

of their certified aircraft, including this exemption, when travelling within their country
of origin, as well as internationally. Honda will coordinate with the applicable foreign authorities for validation requirements related with this exemption.