VI.A.5. Subpart I--Airplane Performance Operating Limitations.

Subpart I contains airplane performance operating limitations

that apply to all part 121 certificate holders; however, not every

section in subpart I applies to every certificate holder. For

example, §§ 121.175 through 121.187 apply to reciprocating engine-

powered transport category airplanes and §§ 121.189 through 121.197

apply to turbine engine- powered transport category airplanes (with an

exception for certain reciprocating-powered airplanes that have been

converted to turbo-propeller-powered). Sections 121.199 through

121.205 apply to nontransport category airplanes.

In part 121 the term "nontransport category airplane" is

currently used to refer to older airplanes like the Curtis C-46, that

were type certificated before the transport category was established,

i.e., the early 1940's. However, many airplanes type certificated

over the last 20 years used by affected commuters (e.g., commuter

category and SFAR 41 airplanes and predecessor categories), are also

nontransport category. Therefore, the FAA proposed to delete the term

"transport category" throughout subpart I and to include language

where appropriate to except airplanes type certificated before January

1, 1965, that were not certificated in the transport category. This

would have the effect of requiring airplanes type certificated in the

commuter category or a commuter category predecessor to be operated

under the performance operating limitations of §§ 121.175 through

121.197, as applicable.

Comments: ALPA states that all requirements of part 121 subpart I

should be complied with by all turbo-propeller airplanes with a

passenger capacity of 10 or more.

AACA concurs that airplanes with 10-to-19 seats should be

required to comply with all of the proposed modifications (in Table 1

of Notice 95-5) except for part 121 performance and obstruction

clearance and floor proximity lighting. (See later discussion of

floor proximity lighting.)

Jetstream, RAA and ALPA support the overall proposals concerning

the higher level of performance requirements. However, they join with

Commuter Air Technology, Raytheon and an individual to point out that

additional performance data/charts would need to be developed (for

example: accelerate-stop and obstacle clearance data). RAA also

recommends a 2-year time frame instead of the proposed 1- year

performance compliance date.

Jetstream states that Notice 95-5, in conjunction with other

proposed rules and changes, will introduce more weight to the

aircraft. In addition to this, AC 120-27D, Aircraft Weight and

Balance Control, will increase standard average passenger weights used

for calculations. The combined effect is that these aircraft will no

longer be allowed to carry 19 passengers due to reduced payload

capacity. According to the commenter, the combined effect of the

weight changes is about two passengers.

Jetstream and Raytheon comment that current FAA policy should be

revised to allow manufacturers to increase the maximum takeoff weights

for aircraft certificated under SFAR 41. They justify their comments

by stating that the increase in maximum takeoff weight will provide a

mitigation of the additional equipment weights incurred under this


One commenter states that better weight and balance control by

the FAA is necessary because many operators are flying over maximum


Fairchild, Jetstream, and AIA propose that the FAA incorporate

the language of § 135.181(a)(2) into § 121.191, which would provide,

in their view, a more conservative approach to one engine inoperative

enroute operations. Jetstream also notes that there is no requirement

for commuter airplanes to show Net En Route Flight Path data in their


One commenter suggests that part 121 be written to specify the

exact performance requirements for nontransport category airplanes to

be included in their performance manuals so there would be no

confusion with other FAA performance requirements.

Fairchild and AIA suggest deleting all references to "transport

category" in §§ 121.189 through 121.197.

FAA Response: Section 121.135(b) requires that the manual

contain methods and procedures for maintaining the aircraft weight and

center of gravity within approved limits. Approved weight and balance

control procedures are the only means for an operator/applicant to

authorize the use of other than known weights for crew, passengers,

baggage, or cargo. The weight and balance control program, including

loading schedules and charts, are approved on operations

specifications by the FAA. This program must be included in the

operator/applicant's policies and procedures manual.

Section 121.189(c)(1) states, for turbine engine powered takeoff

limitations, that "(c) No person operating a turbine engine powered

category airplane certificated after August 29, 1959, may take off

that airplane at a weight greater than that listed in the Airplane

Flight Manual (AFM) at which compliance with the following may be

shown: (1) The accelerate-stop distance must not exceed the length of

the runway plus the length of any stopway."

The FAA agrees that new or additional performance data would need

to be developed for certain airplanes, and that this data would need

to be acceptable to the FAA Aircraft Certification Office and

incorporated into the Airplane Flight Manual (AFM). At the present

time, some AFM's (for Beech 99, certain Metroliners, and the Twin

Otter) do not have accelerate-stop distance data, only accelerate-slow

data. In order for the airplane operator to comply with §

121.189(c)(1), the operators would have to request an AFM supplement

from the airplane manufacturers showing this required data. The FAA

has not required the manufacturers to develop this data. If they have

developed the data, it would still have to be certificated by the FAA

as a revision to the AFM. If the manufacturer does not have

accelerate-stop data, it will have to flight test, simulate, or

analytically prove accelerate-stop distance data to the FAA. This

process could be expensive to the operators who would pay for the

manufacturer's support.

This rulemaking does not require the affected airplanes that are

currently in service or airplanes that will be manufactured under an

existing type certificate to meet the engine-out climb gradient

performance required by part 25. These airplanes will, however, be

required to meet the obstacle clearance limitations of §


Section 121.189(d)(2) states for turbine engine powered takeoff

limitations, that "(d) No person operating a turbine engine powered

category airplane may take off that airplane at a weight greater than

that listed in the Airplane Flight Manual --(2) In the case of an

airplane certificated after September 30, 1958, that allows a net

takeoff flight path that clears all obstacles either by a height of at

least 35 feet vertically, or by at least 200 feet horizontally within

the airport boundaries and by at least 300 feet horizontally after

passing the boundaries." AFM's for some older airplanes with seating

capacity of 10-to-19 passengers do not have data to show the required

climb gradient or the certification basis to clear obstacles after

takeoff with an engine-out at a specified weight. As one commenter

suggests, additional certification requirements would have to be

identified in part 121 or in a new Appendix to 121 for nontransport

category airplanes, except for the commuter category or SFAR 41, ICAO

Annex 8 airplanes, before these airplanes could comply with

§ 121.189(d)(2) requirements.

As with accelerate-stop data, the FAA agrees that new or

additional performance obstacle clearance data for certain airplanes

would need to be developed, and that this data would need to be

approved by an FAA Aircraft Certification Office and incorporated into

the Aircraft Flight Manual. Raytheon estimates that to provide

obstacle clearance data, testing would have to be done on all Beech 99

models and the price per each airplane for the new performance data

would be $63,000 ($53,000 for the Beech 1300). This cost must be

incurred by the manufacturer and then passed on to all the operators.

The FAA recognizes the significant problems in developing the

necessary performance data for airplanes type certificated under a

wide range of standards over the past 30 years, including part 23 (or

its predecessor, part 3 of the Civil Air Regulations) normal category,

plus additional standards in the form of special conditions, SFAR 23,

SFAR 41C, or part 135, appendix A, or part 23 commuter category.

Development of the additional performance data for airplanes

certificated under older standards may be developed by conducting

actual flight tests, data analysis, or any other methods acceptable to

the Aircraft Certification Office. The FAA believes that the

performance requirements of § 121.189(d)(2), obstacle clearance with

an engine-out after takeoff, contribute to an increased level of

passenger and crew safety.

The FAA also understands that the requirements for accelerate-

stop and obstruction clearance may, in fact, remove certain airplanes

from service in part 121. It may also affect the operational

capability of some operators, depending on the location and height of

obstacles, and may terminate air carrier service to some communities

if airplanes are removed from service.

Because of the difficulty that affected commuters would face in

meeting the part 121 performance operating limitations with their

existing fleet, the FAA has decided to provide delayed compliance for

these requirements. Subpart I has been amended to state different

requirements for aircraft used by affected commuters that were

certificated under different certification standards, as follows:

1. Airplanes certificated under commuter category can meet all of

the airplane performance requirements of part 121 within 15 months of

the publication of the final rule.

2. Airplanes certificated under SFAR 41 or earlier certification

standards will be allowed to continue to comply with the part 135

Subpart I and other airplane performance operating limitations

requirements for 15 years. The FAA anticipates that some of the SFAR

41 airplanes will be able to meet the part 121 requirements within the

15-year period so they have the choice of either continuing to

operate under the performance requirements of part 135 for the 15-year

compliance period or complying with the performance requirements of

part 121 during the 15-year compliance period. Some of the airplanes

certificated under earlier certification standards, such as under part

135, Appendix A, part 23, with special conditions, and SFAR's 23 and

41C, will probably never be able to meet the part 121 standards. For

affected commuters operating these airplanes, the 15-year period

allows the operators sufficient time to plan for and obtain

replacement airplanes or to modify them.

Although the FAA encourages affected commuters to comply with the

performance operating requirements earlier than 15 years after

publication of the final rule, it is allowing that length of time to

ensure that there will be an adequate supply of replacement airplanes

available for purchase. The current rate of production of new

commuter category airplanes is approximately 30 per year. But most

importantly, if the FAA were to impose a shorter compliance period and

affected commuters were not able to obtain new airplanes from

manufacturers, they might replace their equipment with airplanes

configured for fewer than 10 passengers. This airplane group is not

covered by this rulemaking and has a higher accident rate than the 10-

19 passenger airplanes. Therefore, an unintended effect of this rule

could be an increase in the accident rate.

In response to Jet Stream's comment, current FAA policy prohibits

revisions to airplanes certificated under SFAR 41 that would increase

the maximum weight or the number of passengers. This SFAR was

terminated on September 13, 1983.

While the FAA understands that some of the older airplanes (i.e.,

normal category predecessors of commuter category airplanes) may not

be able to meet certain performance requirements, the FAA has

determined that some performance requirements, such as the maintaining

of an altitude with an engine-out, are important safety enhancements

that provide for a higher level of safety. This level of safety

required in part 121 should be available to all passengers flown on

carriers operating under part 121.

Section 121.191 requires that the AFM show a one-engine

inoperative net en route flight path which would provide a positive

slope at an altitude of at least 1,000 feet above the terrain (2,000

feet in mountainous terrain) within 5 statute miles of the intended

track. Section 121.191 also provides for a net flight path that would

allow continued flight from the cruising altitude to an airport

clearing all terrain and obstructions. Section 135.181(a)(2) requires

airplanes to maintain a 50 feet per minute rate of climb when

operating at the MEAs or 5,000 feet MSL whichever is higher. It does

not provide for the continuation of the flight below the MEA.

Section 121.191 has continuously provided for safe engine out en

route operations while allowing some flexibility. The flexibility

allows the certificate holder to calculate maximum weights for

maintaining a constant engine out altitude, a continuous flight path

drift down to an airport when an altitude cannot be maintained, and

provides off airways direct routing engine out performance

requirements. The FAA understands that net en route flight path data

must be provided by the manufacturer; however, the FAA believes that

part 121 air carriers deserve the additional flexibility of § 121.191

and that commuters adopting the § 121.191 requirements may gain a

flexible benefit with a continued higher level of safety.

In response to comments, the FAA points out that Notice 95-5

proposed to remove the words "transport category" wherever they appear

in subpart I.

In reviewing part 121 to resolve comments, the FAA noted that

several formulas are printed incorrectly. In the rate of climb

formula for reciprocating engine powered transport category airplanes

certificated under parts other than part 4a of the Civil Air

Regulations (CAR), the parentheses are misplaced. This formula has

been printed correctly in the corresponding part 135 section of §

135.371(a) and (c)(1). Also, in the rate-of-climb formula for

transport category airplanes certificated under CAR 4a [§ 121.181(a)

and (c)(1) and § 121.183(a)(2) and (c)(1)] it is not clear as printed

that the subscript So is to be squared. Appropriate corrections are

made to both formulas.