# HondaAircraft Company HondaAircraft Company**'~'.,:: ,--~r:**  6430 Ballinger Road 1 ·

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### 3\ GN-9438-14-009 U.S. DepartmentofTransportation DocketOperations WestBuildingGround Floor,Room W12-140 1200NewJerseyAvenue, SE Washington,DC 20590 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 ProjectTC9438AT-A Towhom itmay concern, Inaccordancewith 14 CFRPart 11, please find attachedbasis and informationfor Honda AircraftCompany'spetitionfor anexemptionto therequirements of14t:FR

.. Part-23,:·- ·:. §23.181(b) forthe HondaModel HA-420 as relatedto dynamic stabilitycompliance. TheModel HA-420 is currentlyundergoingType Certification, withtheprojectmanaged bytheAtlantaACO. Ifyou have any questions or comments on this request, please feel free to contact Mr. Karl Berg at (336) 662-0246 ext. 1022 ormyselfat (336) 662-0246 ext. 1670. Sincerely,

Randy Griffith HondaAircraftCompany DivisionDirector, Certification Enclosure Cc: DonYoung, FAAAtlantaACO



## HONDA

# ---------------------------------- SUBJECT: Dynamic Stability Compliance (Requestfor Exemption). 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 takeoffand landing atfield 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 offew 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. The HA-420 airplane uses a conventional reversible rudder control system, manually cable-driven via the rudder pedals. The yaw damper utilizes an electronic rudder servo, which generates torque that is in-series with the pilot's pedal inputs to drivethe rudder and 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. Many Part 23 and Part 25 airplanes equipped with a yaw damper do not allow its use during takeoff and landing because the yaw damper can interfere with controllability in crosswinds. Therefore, the yaw damper is disengaged during takeoff and landing to facilitate crosswind control inputs. The in-service history of the 4 flight test aircraft (F1, F2, F3 and 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 ofthe operational flight envelope. The reduced damping of the non-augmented airplane is mitigated by the following compensating features: • Predictable handling qualities with well harmonized flight control forces.

### • The Airplane Flight Manual (AFM) will require the yaw damperto be engaged for all flight phases except takeoffand landing. • The Crew Alerting System (CAS) logic will alert the crew, in the form of CAS messages, any time the yaw damper is not engaged during flight other than the takeoffand landing phases. • The yaw damper is automatically engaged after takeoff and will automatically disengage upon landing. The AFM procedure will direct the pilot to manually disengage the yaw damperat 50 feetjust priorto reducing thrust to idle. • During the short duration that the yaw damper is not engaged during each flight, the pilot is fully in the airplane control loop. The un-augmented dynamic stability is positive and any unwanted residual oscillations are easily controllable bythe pilot. Based upon these compensating features, Honda believes an exemption to 14 CFR 23.181(b) Arndt 23-62 is warranted forthe HA-420.