27 July 2012 IN REPLY, REFER TO: L390-12-1608 U.S Department ofTransportation Docket Operations

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West Building Ground Floor, Room W12-140 1200 New Jersey Avenue, SE Washington, D.C. 20590 REFERENCE: Petition for Exemption

- Stall Speed of61-knots on the Cessna Model T240 CORYALIS. To Whom ItMay Concern: Cessna Aircraft Company requests an exemption to the Stall Speed requirement of 14 CPR §23.1419(a) Arndt 43, as part ofthe Flight Into Known Icing (FIKI) major type design change to the CessnaModel T240 COR VALIS. This type design change is currently OPEN with the Wichita ACO under FAA project TD5550WI-A. The exemption is being requested since the Cessna Model T240 Corvalis will not meetthe 61-knot stall speed requirement with critical ice accretions. In accordance with 14 CPRPart §11.81, CessnaAircraft Company wishes to submit the following information to request a grant ofexemption using the guidance found in AC23.1419- 2D, Paragraph 13a(l)(c). §11.81(a) Your name andmailingaddress and if you wish, other contact information such as a fax number, telephone number, or e-mail address. Carlos Ayala Manager- Airworthiness Cessna Aircraft Company Department 390, One Cessna Boulevard P.O. Box 7704 Wichita, Kansas 67277-7704 Telephone: (316) 517-8575 Fax: (316) 206-6336 §11.81(b) The Specific Section orsections of 14 CFRfrom whichyouseekan exemption; CessnaAircraft Company seeks as exemption to 14 CPR §23.1419(a) with respect to the 61-knot stall speed requirement of§23.49(c). §11.81(c) The extent of relief you seekandthe reasonyou seekthe relief; Specifically, Cessna Aircraft Company seeks an exemption to the following statement of 14 CPR §23.1419(a): "As used in this section, "Capable of operatingsafely", means that airplane performance, controllability, manoeuvrability andstability mustnotbe less then that required in Part23, subpartB. "

Cessna Aircraft Company One Cessna Boulevard, P.O. Box 7704. Wichita, Kansas 67277-7704, W316/517-6000

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This exemption is only requested with respect to the 61-knot stall speed requirement of 14 CFR §23.49(c) for the Model T240 CORYALIS. While the non-contaminated stall speed ofthe T240 CORYALIS meets the 61-knot rule, the T240 CORYALIS with critical ice accretions will not. Thus, this exemption has been requested as described in the FAA guidance provided in AC23.1419-2D, Para 13a(l)(c). This exemption is only requested for aircraft units receiving an initial standard certificate of airworthiness subsequentto the type design certified by FAA project TD5550WI-A. Aircraft units manufactured priorto this project do not include the design requirements for FIKI operations and existing type design does not permit modifications to meetthose design requirements. §11.81(d) The reasons whygrantingyour requestwouldbe in thepublic interest: that is how it wouldbenefit thepublic as a whole; · The Model T240 CORYALIS is primarily used for cross-country travel and has a high probability ofencountering inclement weather- including ice conditions. Increasing the flight envelope of the T240 CORYALIS to include flight into known icing provides a significant increase in safety for operators ofT240 CORYALIS, especially those who inadvertently encounter icing conditions. The associated design features required to make FIKI operations possible add a significant level ofredundancy and increased system capability over the existing design. Also, the flight testing required for this design change has fully proven outthe capability ofthis system and shown that operational safety has increased. However, to maintain compliance with the 61-knot stall speed requirement of§23.49(c) as required by §23.1419(a), the useful load ofthe T240 CORYALIS would need to be reduced to account for the effects ofairframe ice accumulation; i.e. aerodynamic contamination resulting in increased drag and loss oflift combined with the weight ofairframe ice. This useful load reduction would have a considerable negative impact on the utility and safety ofthe T240 as both cabin load and reserve fuel would be potential areas ofreduction. Thus, granting this exemption would be in public interest due to the increased safety associated with the operational envelope expansion without negatively impacting aircraft utility and endurance. §11.81(e) The reasons whygrantingthe exemption wouldnot adversely affectsafety, or how the exemption wouldprovide a level of safety at least equal to thatprovidedby the rulefrom which you seekthe exemption; The following compensating features as described in AC23.1419-2D will ensure the level of safety will not be adversely affected by this exemption. 1. The airplane with no ice accretions meets the 61-knot stallspeedrequirements of §23.49(c). The T240 CORYALIS with no ice accretions stalls at less than 61-knot in the landing configuration at maximum gross weight as documented in the Pilot's Operating Handbook. 2. The airplane with critical ice accretions as defined in theparagraphs 13.b of theAC23.1419- 2D complies with the stall requirements of §23.207.

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The T240 CORYALIS maintains the required stall margin and does not cause nuisance warning as required by §23.207. This has been demonstrated by flight test and will be documented in the flight test reports that will be submitted to the FAA. 3. The AFM performance data in icing conditions reflects the higherstallandoperatingspeeds. The AFM supplement for FIKI equipped aircrafts will include the performance data to be used when flying in icing conditions and/or with known aircraft ice accretions. These speeds have been determined by flight test and will be documented in the flight test reports that will be submitted to the FAA. 4. The airplane with critical ice accretions has acceptable stall characteristics and is safely controllable with normalpilotingsills as requiredby §23.201 and§23.203. Flight Testing with simulated critical ice accretions was accomplished showing acceptable stall characteristics as required by §23.201 and §23.203 and accounting for normal piloting skills as required by §23.141. This will be documented in the flight test reports that will be submitted to the FAA. 5. The tire requirements of §23. 7 33 andbrake requirements of §23. 7 35 are met with the higher stallandoperatingspeeds. Cessna Aircraft Company has determined by analysis thatthe existingtyres and brake system will meetthe requirements of§23.733 and §23.735 respectively. This will be documented in the certification reports that will be submitted to the FAA. 6. The ground handling requirements of §23.231, §23.233 and§23.235 are metwith the higher landing speeds. Cessna Aircraft Company conducted ground handling tests during the simulated ice shape flight tests and found no adverse handling characteristics. 

### 7. All otherairplane system 

### if testing requirements that couldbe affected by higher operating speeds, such as autopilotand flight director gains are evaluated. The autopilot and flight director were evaluated during the flight test program and documented in the natural icing flight test report submitted to the FAA. 8. Each seat/restraintsystem wouldhave to include a safety belt andshoulder harness with metal-to-meta/latchingdevice. The T240 CORYALIS utilises a seatrestraint system that includes safety belts and shoulder harnesses with metal-to-metal latching devices for all four occupant seats. 9. The airplane certification basis wouldhave to include 23.1091 and23.1093 atamendment level 23-51 toprovide the latest regulationsfir engine operation in icing conditions. The FAA project TD5550WI-A certification basis for the Cessna model T240 CORYALIS will reflect the amendment level 23.51.

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10. The airplane certification basis wouldhave to include 23.995 atamendment level23.29. The certification basis for the T240 COR VALIS was established including 23.995 at amendment level23.29. The existing compliance shown for this regulation shall not be affected by this type design change. §11.81 (f) A summary we canpublish in the FederalRegisterstating; (1) The rule.from whichyou seekthe exemption; and (2) A brief description of the nature of the exemptionyou seek; The FAA may publish this letter in its entirety. §11.81(g)Anyadditional information, views or arguments available to supportyour request; In addition to the compensating safety features discussed for 11.81(e) above, Cessna Aircraft Company will be providing a training module specific to flight in icing conditions that will include training related to increased stall speeds associated with airframe ice accretions. This module will be similarto the flight in icing conditions currently in use for the Cessna Model 208 Caravan. Cessna Aircraft Company has an excellent pilot training program that emphasizes the Operational Safety. This module will be made available to call Cessna CORVALIS pilots, including those operating T240 CORVALIS aircrafts equipped with FIKI operations. §11.81(h) lfyou want to exerciseprivileges of your exemption outside the UnitedStates, the reason whyyou needto do so; This petition for exemption is for type certification only. Thus, this item is not applicable to exemption described herein. In conclusion, CessnaAircraft Company requests the FAA grant an exemption to 14CFR §23.1419(a) specific to the 61-knot stall speed requirement. This exemption would be in the public interest by providing increased safety in inclement weather without requiring a significant reduction in useful load. Further, the level ofsafety will be maintained by complying with the compensatingfeatures as described in AC233.1419-2D.

Please feel free to contact me at (316)-517- , ifyou have any questions. Sincerely, 

# Po De--**~?-** Manager ofAirworthiness Cessna Aircraft Company

cc: Linda Dicken- Program Manager, Wichita ACO.