# ""'**CUBCRA~TERS**

cubcraFters.com

U.S. DepartmentofTransportation DocketOperations West Building Ground Floor Room W12-140 1200 NewJersey Avenue, SE. Washington, DC 20590
Re: Petition for Exemption from 14 CFR 23.629

To Whom It MayConcern: 1

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### April 28, 2014

In Mayof 1998, the Gavilan model EL-1 was awarded itstype certificate, A00002NY. Itwas certified as a day, VFR airplane with a4,200 MTOW and aVNE of 155 knots. In March of2008, theType Certificate was revokeddue to the then-current holder's inabilityto complywith 14CFR 21.99(a). Ownership ofthe airplane and its relevant engineering and manufacturing data was purchased by Cub Crafters ofYakima Washington in 2012. Cub Crafters is in the process of re-establishing the type certificateforthe Gavilan model EL-1 under Project NumberTC6535NY-A. The projectwas started with the NewYork Aircraft Certification Office and is in the process ofbeingtransferred to the Seattle Aircraft

The original certification basis was 14CFR Part 23 amendments 23-1 through 23-46 and 14CFR Part 36 Appendix G, including amendments36-1through 36-20. The certification basis forthe current projectto re-establish the Type Certificate has been agreed on and includes all amendments up to23-59. Cub Crafters is working with the Seattle ACO to show compliance through that amendment. By agreementwith the FAA, all ofthe original data thatwas approvedis valid and applicable underthe newapplication. As such, compliance has effectively been shown forany regulation which has not been amended since 23-46, orany regulation that has been amended in a mannerthatwill not impactthe Gavilan EL-1.
The purpose ofthis letter is to petition the FAA to exemptthe Gavilan model EL-lfrom the revised requirement of 14 CFR 23.629 amendments 23-48 and 23-62. These amendments specifically require the airplane to have additional flight testingthatwas not required under its original certification. Cub Crafters requests exemption from both amendments because:

1. The change between amendment 23-48 and 23-62 is not applicable to the Gavilan EL-1, so for the purpose of this project, exemption to amendment 23-62 is equivalentto amendment 23-48. 2. The current determined certification basis to re-establish the Type Certificate forthe Gavilan EL-1 is amendment 23-59. This basis will expire on August 8, 2014, a date which may arrive before afinal position on this exemption request becomes effective. In case the certification basis changes, an exemption to both amendments will save Cub Crafters and the FAA the burden of reapplying and reconsidering this exemption request. The Gavilan EL-i is atwo-occupant, day, VFR airplane with a maximum gross weightof4,200 lb. It is a slowairplane with
a maximum cruise speed of 123 knots and a neverexceed speed ofonly 155 knots.
Cub Crafters is petitioningforthis exemption in accordance with 14CFR 11.81 under Petitionsfor Rulemaking. Cub Crafters onlyrequests exemptionfrom the requirementto flighttestthe airplane in 23.629(a) and asserts thatthe original compliance (by analysis) shall suffice.

Cub Grafters, Inc. 1 1918 South 161 h Avenue 1 Yakima, Washington 98903 1 p 509.248.9491 1 cubcrafters.com**~­** 

## CUBCRAJ:TERS

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Rationale
Cub Crafters proposes the following as mitigatingfactors regarding safety in supportofthis exemption request:

1. Design cruise speed 

### (Vc) is 140 knots, never exceed speed 

### (VNd is 155 knots, and the demonstrated dive speed (V0

### F} is 180 knots. Therefore, it is a slow airplane. 2. The design has high drag. The aircraft was designed to haul large volumes ofcargo. It has a large square section fuselage. The landing gearis fixed and the wings are supported by external struts. 3. The fuselage uses proven and predictable construction ofa steel tube frame with aluminum skin. The wings and tails both use thick airfoils (12% thickness to chord ratio). The wings use a NACA 4412 airfoil and the vertical and horizontal tails use a NACA 0012 airfoil. The wings and tails are constructed of aluminum with two spars, ribs, stringers and skins. The structure is very stiff. 4. In its original certification, compliance was demonstrated by performing a ground vibration survey and by analysis. This was carried out byJohn Baker, a Flutter DER who had over 35 years ofexperience when he didthis analysis. This conservative analysis had ample margins and itwas accepted fortype certification. 5. The EL-l is ofagroup ofairplanes forwhich compliance by analyses forfreedom from flutter is applicable due to its methods of construction, high drag, and slow speed. The examples used in the preamble for amendment 48 tojustifythe requirementforflighttests differsignificantlyfrom this case. 6. 23.629(i) (amendment 48) states (emphasis added): "For modifications to the type design that could affect the flutter characteristics, compliance with paragraph (a) ofthis section must be shown, 

### except thatanalysis based
on previously approved data may be used alone to showfreedom from flutter, control reversal and divergence, forallspeeds up to the speedspecifiedforthe selectedmethod". This application fortype certification 

### ofthe ELl is unique in the sense that it is a Type Certificate that had been issued previously and then revoked for the
reasons mentioned above. It is, strictly speaking, not a modification 

### of an existing design, but rather a new application based on a design which has not been modified since it was issued a Type Certificate. Therefore, while not applicable according to the letter ofthe law, Cub Crafters posits that the intent ofthe law is met and 23.629(i) providestechnicaljustificationfor not havingto conduct aflighttest. 7. The airplane was designed and built for a maximum gross weight of4,800 lbs and all certification analyses and ground tests were performed using this weight. In flight test, with the exception of the Part 36 noise certification, the airplane was flown at a maximum weight of 4,500 lbs. The noise certification was done at 4,200 lbs and hence the limitation on the type certificate. 8. In flight tests, the airplane was safely flown at speeds up to VoF = 180 kts. At this speed, the pilot performed controllability and maneuverability checks. There was no trend towards control reversal and no tendency of divergent behavior. Furthermore, while flutter exciters were not employed, the pilot did perform "stick raps"

- sharply striking the elevator, aileron, and rudder pilot controls- in an attemptto excite flutter. In all three axes the airplane demonstrated adequate structural damping and no fluttertendency. 9. Cub Crafters intends to recertify the airplane to the same speed, altitude, and weight envelope as the original Type Certificate. 10. The test article was manufactured over 15 years ago for the original certification. It was not outfitted to accommodate flutter exciters and retrofitting it now would be a significant (and prohibitive) burden on Cub Crafters. As discussed in 6, above, this burden would not be placed on Cub Crafters (or other manufacturer) if this were a modification. For commercial reasons, such a retrofit may not make sense for Cub Crafters and could terminate the program. 11. The Type Certificate was revoked per the letter dated March 7, 2008 (Case number2007EA580002). The reason for the action was that the holder demonstrated that it lacked the qualifications necessary to hold the Type

Cub Grafters, Inc. 1 1918 South 1611' Avenue 1 Yak1ma, Washington 98903 1 p 509.248.9491 I cubcrafters.com

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### certificate. Itwas notdue to an airworthiness issue. Had that notoccurred, this airplane would be grandfathered and still eligible for production and commercial sale today.

Public Interest Grantingthis exemption forthe Gavilan EL-1 will serve the public interestforthe following reasons:


### 1. Itwill provide a path for safely establishing compliance with 14CFR 23 ata costwhich makes the projectviable. 2. As a single-engine, non-turbine cargo airplane, this airplane serves an important niche that is not well represented in the market. It will have lower acquisition and operating costs than a turbo-prop cargo plane. Some communities**i~** 

### our country (and other parts of the world) depend upon airplanes as a sole or primary
means to transport goods and supplies. This airplane will enable operators to cost-effective-ly serve those communities. 3. This airplane has a sizeable payload and fuel capacity. As such, it is an excellent platform for missions that may require long durations with some specialized equipment, such as search & rescue missions and law enforcement patrol missions. It is clearly in the public's interestthatthese missions can be conducted cost effectively. 4. The manufacture, sales, and operation of this airplane will provide jobs for many people. Skilled laborers will manufacture the airplanes. Salespeople will broker deals to buy and sell these airplanes. The EL-1 is intended for small commercial operators in rural communities where ground transport is difficult, such as Alaska. Therefore, it has the potential to bring significant economic benefit to these areas. Pilots and A&P mechanics will be needed to operate the aircraft. And owners will no doubt create additional jobs in the support and conduct of their business activities. These jobs and income will enhance the local, state, and national economies.

Exercise of Exemption Outside ofthe United States Regarding the desire ofCub Crafters to exercise the privileges ofthe exemption outside the United States, we wish to reserve the rightto marketand exportthe Gavilan EL-1 to customers in countries outside the United States. We understand thatthe exemption to a Part 23 regulation is acertification issue (notan operational issue) and that itwill be listed on the Gavilan EL-l'sType Certificate and Data Sheet, which will be reviewed by otherCivil Aviation Authorities in theirvalidation ofthe EL-l's certification basis.

Daniel Glaser Certification Manager Cub Crafters Gavilan EL-1 Project

Cub Crafters, Inc. 1 

### 1918 South 16111 

### Avenue 1 

### Yakima, Washington 98903 I 

### p 509.248.9491 I 

### cubcrafters.com