### Exemptio n No. 11123 UNITED STATES OF AMERICA DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRAT ION KANSAS C I TY , MO 64106

In the matter of th e petition of HONDA AIRCRAFT COMPANY for an exemption from 

### § 23.181 

### (b) of Title 14 , Code of Federal Regulations 

### Regulatory Docket No. FAA 2014-0700

GRANT OF EXEMPTION By letter dated October 17 , 2014 , Mr. Randy Griffith , Certification Division Director, Honda Aircraft Company (Honda), 6430 Ballinger Road, Greensboro , NC 274 10 petitioned the Federal Aviation Administration (FAA) on behalf of Honda for an exe mption from 

### § 23.18l(b) ofTitle 14, Code of Federal Re g ul ations (14 CFR). The proposed exemp tion , if granted, would a ll ow the Honda Model HA-420 to be certified to use the Dutch roll damping requirement s of 14 CFR 25.181(b), Dynamic Stabi li ty. 

### The petitioner requests relief from the following regulation: Section 23.181 (b) states: "Any combined lateral-directional oscillations (Dutch roll) occurring between the stalling speed and the maximum allowable speed (V

### F E

, V

### LE, V

### No , V

### FciMFc) appropriate to the configuration of the airp l ane w ith the prim ary contro l s in both free and fixed position, must be damped to 

### 1/1 0 amplitude 

### in: ( 1) Seven (7) cycles below 18 , 000 feet and (2) Thirteen (13) cycles from 18 , 000 feet to the certified maximum altitude." 

### The petitioner supports its request with the following information: The petitioner states:

'The Part 23 requirement for Dutch ro ll osc ill ation s to be damped to 1 / 10 amplitude 

### in 7 cycles was written , in part, as a result of few small a irpl anes having yaw damper systems
. In cont rast , nearly all current 14 CFR Part 23 jet
ACE-14-487-E

### 2 

### airplanes are type certificated with yaw d ampers 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 spec ific airplane. Small, nonturbojet Part 23 airp l anes generally do not require a type rating , and thi s 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 witho ut causing rudder pedal motion. Series yaw damper e ngagement may be employed throughout all flight phases including landing and touchdown. The HA-420 a irplane uses a conventional reversib le rudder control sys tem , manually cable-driven v ia the rudd er pedals. The "parall el" yaw damp er utili zes an elect ronic rudd e r servo, which generates torque , moving both the pilot 's pedal s and the rudde r to augment stab ili ty
. The yaw damper i s typically e ngage d in flight to assist in s uppressing the Dutch Roll mode. Ho wever, th e yaw damper also tends to suppress pilot crosswin d rudder inputs , and increase the rudder pedal forces required to generate those inputs. Therefore , the yaw damper is di se ngaged during takeo ff and landing to minimize workload

. The in-service history of the 4 flight test aircraft (Fl, F2, F3, and F4) as well as the first production aircraft ( P 11) ha s shown that the airplane handling qualities are not objectionable with the yaw damp er off during takeoff and landing. The quantitati ve analysis showed that the airplane damping is s li ghtly less than the require ment to damp to 1/10 amplitude in 7 cycles at high field e levations. " The FAA ha s determined that good cause exists for waiv in g the requirement for Federal Register publication because the exemption, if grante d , would not set a precedent , and any del ay i n acti ng on thi s petition wou ld be detrimen tal to Honda. 

### The petitioner offers the following: "The Model HA-420 lateral-directional dynamic stab ility 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 enve lope. " Mitigation discussion:

• " Predi ctable handling qualities with well harmoni zed flight control forces.

• The Airplane Flight Manual (AFM) will require the yaw damper to be engaged for all flight phases except takeoff and landing.3
• The C r ew A le ttin g System (CAS) l og ic w ill alett the c rew , in the form of CAS messages , any ti m e the yaw damper is not engaged during flig ht o th er than the takeoff and landing p h ases.
• The yaw damper is a u tomati call y engaged after takeoff a nd w ill a utom at ica lly di se n gage up o n landin g. The AFM pro ce dure w ill di rec t the pilot to manually disengage the yaw damper prior to landi ng.
• During the short duration that the yaw d amp er is n o t engaged durin g eac h flight , the pilot is fully in the airp l ane contro l loop. The un -augmen ted dynamic s t ability i s po s itiv e and any unw ante d re s idu a l oscillations are easi ly contro ll able by the pilot." The l eve l o f safety:

• " The yaw d amper i s re quire d b y the AFM procedure and w ill provide a h

ighl y damped Du tc h roll r esponse for all flight phases w he n engaged. T hi s w ill decrease pilot work lo a d

.
• Test ing s h ows tha t, in the unlikel y event of a yaw d a m pe r failure , th e a u topilot roll c hannel provides hi g hly damp ed Dut c h roll res pon se at all a lt itud es up to the maximum o p e rat in g al titud e.
• In rare instances w h en neither autopilot nor yaw damper are avail ab le, the AFM will provide a m ax imum " retreat' altitude where natural Dutc h ro ll d ampin g m eets the ba si c rul e (damping to 1110 amplitude in 1 3 cyc les). Co mp an y test have shown , and certi ficat io n testing w ill veri fy that the ai rcraft can safe l y desce nd to this retreat altitude fro m maximum operating a ltitude, and a l so descend from the retreat a ltitude to landin g.
• Relative to the objectionabl e wo rk load w ith a p arallel yaw damp e r engaged, disengaging the y a w damper fo r crossw ind o r gusty takeoffs and landin gs e nh a n ces safety

.
• As part of flight t esti n g u s ing normal procedu res, company te st pilots and D E R pilots evalu ated numerou s takeoff and landings with the yaw damp e r di se n gaged. Testing cons i sten tl y s h owe d that natural Du tch roll damping res ul ted in acceptable wo rklo a d and did not adverse ly affect safety. Furthe rmore, in the course of certification testing , FAA pilots wi ll have amp le op portunity to evalu ate and confirm workload acceptability across th e spectrum of atmospheric co nd itions n a turally found durin g flight tes ting. "4 Public interest and g l oba l considerations:

• "For the a irframe to inherently provid e th e required dampin g would res ult in a les s fue l effic ie nt d esign. The aircraft was d es i g ned to cruise effic ie ntl y at high spee d a nd high altitu de. When the necessary l evel of safety can be provided, m ax imum ef fi c ien cy i s in the public interest.

• A more comp l ex a nd expensive series yaw damper system design i s not typical for thi s cla ss of aircraft. Years of indu s try fleet experience with this style o f yaw d a mp e r show that the necessary l eve l of safety can be ac hi e ved. Minimi z ing ex p e n se and complexity are in th e public intere s t.

• The aircraft i s marke ting to a global c u sto m er base. Hond a Ai rc raft Company will pursue foreign ce rtification s s hortl y afte r receiv in g FAA cert ific at ion. It i s anticip ated that o ur c u sto mers outside the U nited States wi ll exercise the privileges o f their certified aircraft , includin g this exemption, when tra ve lli ng within their country of origin, as we ll as internationally. Hond a w ill coo rdinate with th e applicab le fore ign authorities fo r validation requirement s re la ted with this exemption." 

### The FAA's analysis is as follows: T he FAA finds th at some part 25 and part 23 a irpl anes have been exem p ted from u se of the yaw damper for t akeoff and landin g b ecause the yaw damp er can inte rf e re w ith co ntrollabi lit y in crosswinds. The FAA agrees wi th the petiti o n er's po i nt s a nd believes this i s a reasonable exceptio n to the Dutch roll r eq uireme nt s . Add iti onally , se rvice experience of s imilar airplanes s upport s thi s exemption requ est. 

### The FAA's Decision In consideration of the foregoing, I find that a g rant of exemption i s in the public intere st an d will not adve rsely affect safety

. T herefo re, pursuant to th e authority co nta ined in 49 U.S.C. 

### §§ 10 6(f), 4011 3, and 4470 1 , d e legated to me b y the Administrator, Honda Aircraft Compan y is granted an exemption from 14 CFR 23.181 (b) to th e exte nt necessary to u se 14 CFR 25.18l(b), Dynamic Stability Dut ch roll damping requireme nt s for their Model HA420 airplane certification basis, subject to th e conditions and lin1 itations li s ted below. 

### Conditions and Limitations 1. The Hond a Mode l HA-420 yaw damp e r may be disabled for takeoff an d landing , using part 25.181 (b) require ments in stead of part 23 .181 (b) requ irements o nl y for this pha se of flight.

### Project No.: ACE-14-487-E Project Officer: Lowe ll Foster ACE-111 :Tiompkins: 11 /26/14: Do c#xxxx (Insert Stylewriter Score Here] Randy Griffith Division Director, Certification Honda Aircraft Company 6430 Balling er Road Greensboro, NC 27410 65 2. A pilot evalu ation mu s t be made , with the yaw damper disabl e d during landing and takeoff , to verify that no un safe condition exists with th e airplane's handling c h aracteri stics. At leas t two Aircraft Certification test pilots and at least one Aircraft Eva luation Group (AEG) pilot shou ld conduct th e evalu ation

. I ssued in Kan sas Ci ty, MOon December 16

. 2014

.



# w~ Earl La wrence Manage r, Sma ll Aircraft Direc torate Aircraft Certifi cation Service

• I(

### 5 2. A pilot evaluation mu st be mad e, w ith the yaw damper di sab led during landing and takeoff, to verify that no un safe condition exists with th e airplane's handling characteristics. At l east two Aircraft Certification test pi lots and at l east one A ircraft Eval uation Group (AEG) pilot shou ld conduct the evaluation. Iss ued in Kansas City, MOon December 16 2014.



# w~ Earl Lawrence Manager, Small Aircraft Directorate Aircraft Certification Service