16 February 2015 ._

1N REPLY, REFER TO: L390-15-0296

U.S Departinent of Transportation Docket Management Facility West Building ground floor Room W12-140 1200 New Jersey Avenue, SE Washington, DC 20590

ATTENTION: Docket Operations

SUBJECT: Cessna Aircraft Cornpany, Model 750, Request for Exemption

from the Reqtitirements of 14 CFR 25.1447(c)(1)

REFERENCE: FAA Project Cessna-075769

To Whom it May Concern:

Cessna requests relief from the following regulations for the Model 750 to allow takeoff and landing at elevations up to 15,000 ft:

Section 25.1447(e)(1) Amdt 41 states: "There must be an oxygen dispensing tmit connected to oxygen supply terminals immediately available to each occupant, wlierevec seated. If certification for operation above 30,000 feet is requested, the dispensing units providing the required oxygen flow must be automatically presented to the occupants before the cabin pressure altitude exceeds 15,000 feet and the crew must be provided with a manual means to make the dispensing units inunediately available in the event of failme of the automatic system. The total number of dispensing units and outlets must exceed the nttmber of seats by at least 10 percent. The extra units must be as uniformly distributed thronghout the cabin as practicable."

An exemption is reqtiested to the portion requiring the dispensing ttnits to be automatically presented to the occupants before tlhe cabin pressure altitude exeeeds 15,000 feet.L390-15-0296

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The present aircraft uses Transport Airplane Directorate (TAD) Equivalent Level of Safety (ELOS) Memo TC0002WI-T-SG-8 to address suppression of the 10,000 foot cabin presstn•e altitude warning required by 25.841(b)(6) when operating to and from airports with a field elevation between 8,000 and 14,000 feet.

To avoid nuisance warnings when operating to and from airports with a field elevation greater than 14,000 feet, an exemption is requested to allow use of an"Elevation >'14k" button to shift the cabin altitude warning to 14,700 feet.

The petitioner supports its request with the following:

China cuiTently contains four airports with elevations in excess of 14,000 feet, including Daocheng Yading Airport at 14,472 feet. It is requested that the aircraft be capable of operations at these and other aitports witlh field elevations above 14,000 feet (with anticipated barometric pressure variations) and up to 15,000 feet. In order for the Model 750 Citation X+ to provide the additional capability for operation at these airports, the Cabin Pressure Control System (CPCS) and Passenger Oxygen Control System (POCS) will be modified to allow the eabin pressure altitude to reach as high as 15,150 t 150 feet. Manual control of the oxygen system is not affected and can be activated at any time the crew deems necessary.

Public Interest Statement:

Cessna's leadership position in the global business jet market is due to the efforts of its nearly 8,000 employees in manufacturing plants, completion cent'ers, and service centers across the United States. This furtlier includes the many vendors loeated across the United States that provide the ntimerous aircraft pieces such as avionics, oxygen components, as well as the modified CPCS components that would be used for the aircraft to operate at this high elevation. Cessna competes for new business all over the world. Although the current economy has slowed, Cessna is striving to gain intemational marlcets for its business jets. This increased market directly affects the viability of Cessna and would aid in the stabilization of the job rnarket, as well as the growth of the American economy, which is directly in the interest of the public.

Supporting Information:

A requirement for automatic presentation of masks for airplanes certified to operate above 30,000 feet originated in §4b.651(d)(3)(i) of the Civil Aviation Regulations (CAR) and was carried over as §35.1447(c)(1) when part 25 was codified. The CAR requirement did not specify the maximum cabin pressure altitude allowed prior to presentation. The requirement that oxygen equipment be automatically presented before the cabin pressure altitude reaches 15,000 feet was added at Arnendment 25-41, effective September 1, 1977. This additional requirement recognized the hazard of oxygen deprivation on the average human being and its effect on carrying out actions under stressful conditions. It should be recognized that in travel requiring use of the Elevation > 141c mode, the persons on the aircraft will be disembarking at an altitude near 15,000 feet. Therefore, the cabin altittide conditions are coinparable to the environnlental conditions to which they will be exposed.L390-15-0296

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The oxygen mask presentation at 15,750 t 250 feet is only selected when an"Elevation > 14k" button is activated by the pilot. The button will remain illmninated and an advisory ELEV > 14K inessage will be displayed to indicate that the plane is in Elevation > 14k mode. These features assist in limiting the use of this mode to conditions when the airplane will be operating at airflelds with an elevation greater than 14,000 feet. The activation point for the cabin altitude warning is also shifted to avoid nuisanee alerts. Appropriate procedures will be provided in the Airplane Flight Manual to address proper operation of the Elevation > 14k mode. These procedures will instruct the flight crew to select this mode when deseending to land at an airfield with an elevation greater than 14,000 feet, and to reset the "Elevation > 14k" button back to the "nonnaP' mode while climbing after takeofl: These procedures will minimize the duration of the elevated cabin altitudes. These procedures are for China-based aircraft and will be similar to those for the previously certifled Model 680 high altitude option.

If 

### you require additional infonnation or have any questions, please do not hesitate to contact Travis Tyler at (316) 517-3029 or tltvlerlFi)txtav.com

.

Sincerely,

B~ rian Ricliardet Manager, Airwoi

- Chiness Cessna Aircraft Company

Cc: Tina Miller, Prograin Manager, Wichita ACO