AFS-14-285-E

Exemption No. 11613

UNITED STATES OF AMERICA

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

WASHINGTON, DC 20591

 

In the matter of the petition of 

 

SPRINGFIELD AIRCRAFT Regulatory Docket No. FAA-2014-0315 

CHARTER AND SALES, INC.

for an exemption from § 135.89(b)(3) 

of Title 14, Code of 

Federal Regulations 

DENIAL OF EXEMPTION

 By letter dated May 14, 2014, Mr. Louie DeSantis, Assistant Director of Operations,

Springfield Aircraft Charter and Sales, Inc., (Springfield Aircraft), 10 Northwest Richards 

Road, Suite 108, Kansas City, MO 64116, petitioned the Federal Aviation Administration 

(FAA) on behalf of Springfield Aircraft for an exemption from § 135.89(b)(3) of Title 14, 

Code of Federal Regulations (14 CFR). The proposed exemption, if granted, would allow 

Springfield Aircraft to operate a pressurized aircraft at altitudes above 35,000 feet mean sea 

level (MSL), [FL350], without requiring the pilot at the controls to wear, secured and sealed, 

an oxygen mask. 

The petitioner requests relief from the following regulation:

Section 135.89(b)(3) prescribes, in pertinent part, that “Whenever a pressurized aircraft 

is operated at altitudes above 35,000 feet MSL, at least one pilot at the controls shall 

wear, secured and sealed, an oxygen mask...”

The petitioner supports its request with the following information:

The petitioner states that, by operating under §121.333(c)(2)(i)(A) instead of § 135.89(b)(3), it

would realize significant savings in on-board oxygen duration, thereby enhancing operational 

safety when conducting extended over water/remote missions. The petitioner contends that 

this reduction in en route oxygen use is paramount when flight planning extended operations 
2

over remote and/or oceanic areas by increasing the amount of available oxygen at the Equal 

Time Point (ETP) for cabin depressurization emergencies.

The petitioner states that, in some cases, the ability to remain at FL250 for extended periods of 

time post loss of cabin pressure is mandatory to prevent incurring a “wet footprint” or for

terrain clearance requirements in areas of exceedingly high terrain.

The petitioner states its current aircraft fleet is such that aircraft system oxygen is available to 

all crew/passengers and the passenger masks are approved for continuous use up to FL250. 

Because of this capability, the petitioner states it is able to improve overall safety by 

descending to FL250 (initially) during an aircraft depressurization, rather than a continuous 

descent to 10,000 feet. According to the petitioner, this strategy serves two purposes:

1) Enhanced terrain separation clearance – The petitioner states that there are few 

geographic areas around the world that would penetrate the FL250 capability of its

aircraft. By limiting the initial descent during a depressurization to FL250, the crew is 

able to regroup and evaluate terrain/obstacle clearance before commencing further 

descent.

2) Extended ETP envelope – The petitioner suggests that most part 121 air carriers plan a 

descent to FL100 after experiencing a depressurization, incurring huge penalties in en

route fuel flow and a drastic increase in diversion times as a result. Additionally, when 

conducting oceanic or remote operations, the aircraft is now limited in diversion 

capability due to the low altitude, high fuel flow, and resultant low true airspeed. 

Conversely, the petitioner states, its aircraft are able to level at FL250, above 

significant terrain and weather, and hold higher Mach/true airspeed, thereby reducing 

diversion times to the alternate airport. The petitioner asserts that the relief from 

§135.89(b)(3) delays, for a short period, the onset of single crewmember oxygen 

depletion while manning the flight deck. The petitioner asserts that part 121 aircraft 

operate predominantly between FL 330-370, whereas corporate aircraft are designed to 

start cruise at FL390 to FL410 and continue optimized climb schedules to as high as 

FL510.

The petitioner states that few corporate aircraft can make designed range profiles below 

FL410, its fleet included. The petitioner points out that the Gulfstream V’s (GV) Quick 

Reference Handbook flight planning chart starts at FL390 and continues up to FL490. The 

petitioner states the difference in hourly fuel burn between FL350 and FL450 is almost 1,000 

pounds per hour and that, over a typical 10-12 hour flight, altitude plays an important role in 

efficiency and range.

The petitioner states that, by its analysis, a mid-size, mid-range, corporate aircraft conducting 

a flight from SFO-HNL with six passengers and two crew (oceanic/remote operations) close

to the limits the aircraft, cannot, under most circumstances, descend to FL100 after a 

depressurization and make land with the required reserves, i.e., incurring a wet footprint. 
3

Under this scenario, once reaching FL100, the aircraft must slow to max range cruise just to 

make land taking roughly 3+51. However, by stopping descent at FL250 to expend on board 

oxygen (120 minutes), then commencing descent to 10,000 feet the aircraft easily makes land 

over 1.7 hours sooner, at roughly 2+10. The petitioner concludes that reducing crew and 

passenger exposure to extended diversion times during emergency situations is paramount to a 

successful (and survivable) outcome to an emergency.

The petitioner states the significance of this scenario is the fact that prior to reaching FL410, 

upon passing FL350, at least one crewmember must be depleting the oxygen system. 

Under the above scenario, the oxygen reserve (fully serviced bottle) at FL250 is 

approximately 161 minutes (3140 liters of O2), minus what the crew consumes prior to the 

ETP. To prevent a wet footprint scenario, the aircraft must arrive at the ETP with 

approximately 2,640 liters of oxygen (120 minutes at FL250 for two crew members and six

passengers). Estimating an average consumption rate of 3 liters/min (per single crew member 

at a typical pressurized cabin altitude) for the 146 minutes it takes to arrive at the ETP, 438 

liters of available oxygen would be depleted, leaving roughly 2702 liters of oxygen remaining 

(3140 liters of fully serviced O2 system). This leaves a difference of only 62 liters of oxygen. 

Keep in mind that these numbers are based on a fully serviced bottle at 1800 pounds per 

square inch.

The petitioner states that where relief from §135.89(b)(3) will come into play is by delaying 

the depletion of oxygen until reaching higher flight levels (above FL410). In this case, they

would expect to be above FL350, but below FL410, for approximately 30 minutes, thereby 

saving roughly 90 liters of oxygen. The petitioner asserts that, for longer-range missions in the 

GV, where initial level off altitudes at high gross weights are below FL410 for several hours, 

it could realize savings of roughly 300 to 500 liters of oxygen. This is a significant factor in

mitigating compound emergencies and reducing risk to those on board. By complying with 

§121.333 (c)(2)(i)(A), flight crews will be better prepared to deal with a loss of cabin pressure 

by having the maximum amount of available oxygen when it is needed the most; to execute a 

rapid descent to a safe altitude and extend diversion cruise capability at a higher altitude. 

The petitioner emphasizes that both fleet aircraft types it currently operates include an 

automatic Emergency Descent Mode designed to augment/protect the initiation of an 

emergency descent should the crew become incapacitated. Both the GV and Cessna 

Citation X (CE750), with autopilot engaged, will initiate a 90 degree left turn, descending at 

maximum operating limit speed (Vmo/Mmo) to 15,000 feet and level off.

The petitioner states that it is important to note the redundancy built into both the GV and 

CE750 pressurization systems, which are certified under part 25 (Airworthiness Standards: 

Transport Category Aircraft). The petitioner describes the redundancies as follows: 

 Both aircraft have two sources of engine bleed air, either of which is sufficient to meet 

the demands of the aircraft. Additionally, both aircraft are equipped with dual air 

conditioning packs, each of which is capable of supplying sufficient pressurization air 
4

in the event one unit fails. Both aircraft are equipped with an isolation valve that will 

allow one engine to supply bleed air to both packs in the event of an engine failure, 

bleed leak, or other cause for single source bleed supply. Both aircraft are equipped 

with dual pressure vessel bulkheads between the cabin and baggage compartments. If 

the baggage door seal were to fail, the secondary pressure vessel and check valves 

automatically isolate the baggage compartment and maintain normal cabin pressure. 

 Both aircraft pressurization controllers are triple redundant with an automatic, manual, 

and emergency mode of control that are supplied power from multiple redundant 

sources. In terms of warning systems available to advise the flight crew of impending

failure or increasing cabin altitude both aircraft are equipped with multiple set points 

for both warning and caution messaging, including aural advisories.

 The passenger oxygen system automatically deploys at approximately 13,500 feet, and 

above a cabin altitude of FL370, crew oxygen masks automatically provide pressure 

breathing rather than just 100 percent oxygen.

The petitioner contends that, as a result of the multiple levels of redundancy in the 

pressurization system, one of the only means of a truly “rapid” or “explosive” decompression 

would be a significant structural failure of a cabin door, cabin or cockpit window, or failure 

the aluminum skin structure or ribbing. The petitioner states that, to date, there has never been 

such a failure on either aircraft since their certification in the late 1990’s.

The petitioner points out that its fleet is equipped with Technical Standard Order (C78a, C89a, 

C99a) quick donning on-demand oxygen masks of the same make/model as those used in 

part 121 air carrier operations. The petitioner states that the same operating procedures for 

both oxygen masks are employed. Furthermore, the petitioner contends that these systems are 

certified under §§ 25.1441 through 25.1453, the same regulations part 121 air carrier aircraft 

are manufactured thereby positively establishing equivalent levels of safety.

The petitioner states that it seeks relief from § 135.89(b)(3) not as a means to circumvent 

regulations but, rather, because it has been deemed vital to flight safety to mitigate oxygen 

depletion to conserve emergency oxygen reserves in the event an aircraft experiences a loss of 

cabin pressure and is forced to descend to lower altitudes.

The FAA’s analysis:

The FAA has fully considered the petitioner’s supporting information. The FAA has 

determined that the circumstances the petitioner presents do not justify a grant of exemption. 

The FAA finds that the petitioner has not shown how a grant of exemption would be in the 

public interest or how it would provide a level of safety equivalent to that provided under the 

current regulation. Our analysis is based on the lack of safety mitigations put forth by the 

petitioner, such as the extent and type of training crew members receive on high altitude 

operations, to include the effects of hypoxia, the procedures that crew members must follow 
5

prior to reaching FL350, and the procedures that address crew members’ actions when 

operating above FL350. We determined the failure to address these concerns overlooks the 

purpose for requiring at least one pilot at the controls to wear an oxygen mask as required by 

§ 135.89(b)(2)(i).

In a decompression event, the pilot’s judgment and motor skills may become impaired almost 

immediately. Because of the possibility of impairment, the proposed exemption poses an 

unacceptable risk to the safety of flight. In gradual decompression situations, crewmembers 

may fail to recognize the effects of hypoxia and a single pilot not wearing an oxygen mask 

may not be able to don the mask due to the effects of hypoxia. The FAA referred to the 

National Transportation Safety Board (NTSB) accident report (CHI96IA157) that involved 

American Trans Air, Flight 406, on May 26, 1996, as an example of the dangers of hypoxia. 

Also see William F. O’Conner, Ph.D. and George E. Pendergrass, Effects of Decompression 

on Operator Performance, DOT/FAAAM 66-10 on page 6, which evaluates decompression 

impairment and its affects, concluding that “The various analyses indicate impairment of the 

operator’s rate of performance for 2 to 4 minutes following rapid decompression with some 

suggestion that the severity of effects increases with increase in decompression altitude. The 

operator’s total time lost from his primary task, at the point of decompression where donning 

is required, has a mean value of some 16 seconds, while the 95th percentile falls at about 

25 seconds.” In Reactions and Performance of Pilots Following Decompression, Aerospace 

Medicine 32, pages 134 to 136, G. Bennett stated that only 36 percent of pilots were able to 

don their masks within 10 seconds following a decompression at 30,000 feet. In addition, it 

was found that all subjects reported hypoxia symptoms, and finally concluded that full 

protection at 40,000 feet could not be guaranteed unless pilots were wearing their masks and 

breathing oxygen at the time of decompression.

The petitioner asserts that given the advances in technology, a rapid decompression event 

would be very rare, and even in the case of such an event, the mask could be easily donned by 

the crewmembers. However, the FAA notes that relative to the potential likelihood of a 

decompression, the Transport Aircraft Directorate (TAD) has developed mathematical 

decompression models for aircraft certification. According to the TAD, an engine rotor burst 

event could cause a very rapid decompression, even in a large volume aircraft. Although such 

an event is rare, the TAD cannot classify the event as “extremely improbable.” In the case of 

such an event, nevertheless, a crewmember must be able to respond quickly and to ensure 

such response, it is necessary for the crewmember to comply with § 135.89.

On August 12, 1982, the FAA published Notice of Proposed Rulemaking (NPRM) 

No. 82-11, Pilot Oxygen Mask Requirements (47 FR 35146) that proposed amendments to 

pertinent sections of parts 91, 121 and 135 pertaining to flightcrew oxygen mask use 

requirements. The proposed amendments would allow the operation of aircraft to higher 

altitudes than presently specified in the regulation without requiring at least one pilot at the 

controls to wear and use an oxygen mask. The NPRM was premised on several 

considerations: (1) the capabilities and limitations of oxygen equipment; (2) pressure vessel 

size and probabilities of depressurization; (3) operational limitations at the maximum 
6

altitudes of modern aircraft; and (4) perceived inequity in the applicability of oxygen 

requirements in part 135 compared to those in part 91. It was noted in the NPRM that the 

proposed amendments, if adopted, would be responsive to industry petitions for exemption 

and alleviate, to some extent, certain burdens perceived by aircraft operators that restrict the 

ease and flexibility of flight operations. Coincidentally, the FAA would be relieved from the 

administrative burden of granting exemptions to the regulation.

The concerns expressed by certain commenters opposed to the proposed amendments 

contained in Notice No. 82-11 prompted the FAA to reconsider the proposed amendments 

and the supporting rationale included therein and also stated in previous grants of 

exemption. Particular attention was directed at the potentially severe physiological 

consequences resulting from high altitude depressurization in both large and small cabin 

volume aircraft that possibly would incapacitate the flightcrew and result in an accident. 

That reconsideration led the FAA to conclusions different from those expressed in Notice 

No. 82-11 and previous grants of exemption. The FAA determined that further grants of 

exemption should be discontinued and the notice withdrawn. Notice No. 82-11 was

withdrawn March 18, 1986 (51 FR 9432) and incorporated by reference in this 

analysis/summary.

Further, the FAA subsequently evaluated the type of operations that you propose. In Denial of

Exemption Nos. 4667 and 8502 (copies enclosed), the FAA cited that it published the 

withdrawal of Notice of Proposed Rulemaking (NPRM) No. 82-11, Pilot Oxygen Mask 

Requirements (47 FR 35146). The FAA further determined that if it found that it could 

grant relief from the current regulation, it would initiate a rulemaking action rather that 

issue grants of exemption.

The FAA’s Decision:

 In consideration of the foregoing, I find that a grant of exemption would not be in the 

public interest. Therefore, pursuant to the authority contained in 49 U.S.C. §§ 106(f), 40113, 

and 44701 delegated to me by the Administrator, the petition of Springfield Aircraft Charter 

and Sales, Inc. for an exemption from 14 CFR § 135.89(b)(3) is hereby denied. 

Issued in Washington, D.C., on May 18, 2015. .

/s/ John S. Duncan

Director, Flight Standards Service