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 

Page 2 

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 

Page 3 

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