VI.A.4. Subpart H - Airplane Requirements

For comments and FAA responses to the requirements in

§ 121.157, Aircraft certification and equipment requirements, see the

discussion in Section V. C., Aircraft Certification.

Single-engine airplanes. Section 121.159 prohibits operation of

single-engine airplanes under part 121. No change to this prohibition

was proposed since the FAA does not consider single-engine airplanes

acceptable to part 121 standards. Under the proposal, this section

was amended to delete an obsolete reference to § 121.9. No comments

were received on this issue and the final rule is adopted as proposed.

For a related discussion on the operation of single-engine Otters,

see "Applicability: Alaska," in Section V.B.

Airplane limitations: Type of route. Section 121.161(a)

requires that a two-engine or three-engine airplane except a three-

engine turbine powered airplane must be within 1-hour flying time from

an adequate airport at normal cruising speed with one engine

inoperative, unless otherwise approved by the Administrator. Part 135

does not contain a comparable requirement; however, the FAA proposed

that affected commuters would comply with the requirements of §


Section 121.161(b) contains a separate requirement that (with

some exceptions for certain older airplanes) no person may operate a

land plane in extended overwater operations unless it is certificated

or approved as adequate for ditching. The FAA proposed that affected

commuters would also comply with the requirements of § 121.161(b). In

Notice 95-5, the FAA invited specific comments on the potential impact

of these proposals on operations in Alaska.

Comments: Several comments were received on the § 121.161(a)

requirement to be within 1 hour of an airport with one engine

inoperative. One commenter suggests that § 121.161 be rewritten to

reflect today's environment, since no airport in the U.S. is more than

1 hour away for these commuter airplanes. The commenter also states

that the rule should specify the requirements for two-engine

operations over the water.

Fairchild and AIA both state that § 121.161(a) would require

single-engine cruising speed data and this data is unlikely to be

included in some Airplane Flight Manuals (AFM). The commenters also

state that there appears to be no safety benefit and it will be

difficult to show compliance. According to these commenters, the

final rule should except 10-30 passenger seat airplanes.

Phoenix Air anticipates that its operations with a Grumman G-159

Gulfstream airplane would be disrupted due to the requirements of §

121.161, since they intend to start service between Honolulu and

Midway Island. There are no airports that would be within 1 hour of

the intended flight path.

Jetstream concurs with the requirement that airplane routes

should be within 1 hour of an adequate airport.

Three comments were received on the certification ditching

requirements of § 121.161(b). Fairchild and AIA note an apparent

oversight in that the FAA did not propose to exclude part 23 Normal or

Commuter Category airplanes from the ditching requirements of §


AACA notes that several certificate holders fly affected aircraft

on extended overwater routes in Alaska. Compliance with the part 25

ditching requirements would add certification costs, impose equipment

weight penalties, and reduce payloads. According to the commenter,

the FAA did not calculate these costs. The commenter supplies

information indicating that costs to comply with the ditching

requirements of part 25 are substantial.

FAA Response: Despite the comments to the contrary, the FAA has

decided to adopt its proposal to apply the route limitation

requirements of § 121.161(a) to the 10- to 30-seat airplanes operated

by the affected commuters. Under that section any route flown by a

twin engine commuter type airplane must be flown so that it is within

1 hour of an adequate airport for landing. Part 121 and its

predecessor regulations have applied route limitation requirements to

airplanes operating under those requirements since 1936. While the

specific details of the route limitation requirement have changed over

the years, the underlying safety issue has not; the certificate holder

must show, before operating affected airplanes over a route, that it

can safely continue flight in an emergency situation to an airport

adequate for landing. The FAA understands that some of these

airplanes will require an AFM revision that will provide engine-out

cruise speed data. There are routes in areas outside of the

contiguous U.S. that are more than 1 hour flying time (with one engine

inoperative) from an adequate airport. In accordance with §

121.161(a), the Administrator may authorize a deviation from the

requirement, if the operator can show that the 1-hour flight time

limit is not necessary based on the character of the terrain, the kind

of operation, or the performance of the airplane. Obtaining

authorization to conduct extended range operations with two-engine

airplanes is dependent upon many factors. Some of these factors are a

type design review of the airframe system, a review of the in-service

history of the airplane propulsion system, and an assessment of the

certificate holder's maintenance and inspection program capability for

extended range operations. Advisory Circular 120-42 provides the

guidelines for this authority. Other rules provide the requirements

for extended overwater routes.

The Douglas DC-3 and Curtiss C-46 airplanes excluded from §

121.161(b) were type certificated and manufactured before the present

standards of part 25 were adopted. These aircraft were excluded

because of their previous operating experience which showed, in some

cases through actual ditchings, that these old airplanes could ditch

satisfactorily. The Convair 240, 340, and 440 and Martin 404

airplanes were also type certificated before the present standards

were adopted. They were excluded because tests conducted by the

National Advisory Committee for Aviation showed they would have

excellent ditching characteristics. Unlike current part 25, part 23

contains no standards for ditching approval. Unlike those older

airplanes excluded in § 121.161, none of the part 23 airplanes have

been shown to comply with any ditching standards. Contrary to the

commenter's assumption, requiring part 23 airplanes used in extended

overwater operations to meet the ditching certification requirements

was not an oversight. In Notice 95-5 preamble, the FAA concluded that

these requirements should be applied to the operations that would be

moved from part 135 to part 121.

After considering the comments, the FAA has determined that until

15 years after the date of publication of the final rule a certificate

holder may operate in an extended overwater operation a nontransport

category land airplane type certificated after December 31, 1964, that

was not certificated for ditching under the ditching provisions of

part 25 of this chapter. Section 121.161(c) has been added


Proving tests. Section 121.163 provides proving test

requirements for part 121. In addition to aircraft certification

tests, an aircraft to be operated under part 121 must have at least

100 hours of proving tests for an airplane not previously proven for

use in part 121 operations, and 50 hours of proving tests for an

airplane previously proven for use in part 121 operations. The

number of hours may be reduced by the Administrator. Section 135.145

requires 25 hours of proving tests in addition to certification tests

for certificate holders that operate turbojet airplanes or airplanes

for which two pilots are required for operations under VFR if that

airplane or an airplane of the same make and similar design has not

been previously proved in any operations under part 135. Both

§§ 135.145 and 121.163 require proving tests for materially altered

airplanes. However, under § 121.163, proving tests apply to each

airplane to be operated under part 121. Under part 135 proving tests

apply to each aircraft or to aircraft of similar make and design.

Part 121 also describes three types of proving tests. Under part 121,

the initial operator of a type of airplane must conduct at least 100

hours of proving tests, acceptable to the FAA, which can be reduced in

appropriate circumstances. Moreover, for each kind of operation

(e.g., domestic, flag, supplemental) that an certificate holder

conducts, 50 hours of proving tests are required, which are reducible

in appropriate circumstances.

Comments: Six substantive comments were received. Comair and

RAA concur with the requirement for an air carrier to demonstrate its

ability to perform in accordance with part 121 and company procedures.

However, Comair proposes that carriers currently conducting

operations under part 121 and part 135 (split certificates) should not

be required to conduct this demonstration. Carriers conducting part

121 and part 135 operations have previously proven their ability to

conduct part 121 operations. If the requirement for dispatching is

adopted, flight crewmembers will demonstrate their proficiency with

the new system during their required line check.

RAA comments that proving flight hours should be reduced based on

"experience and performance" factors. To facilitate a reduction in

flight hours, the FAA should identify those specific procedures for

which non-revenue proving flights would be required and specify a

realistic number of flights or flight hours which would be sufficient

to demonstrate those procedures.

ASA believes that the requirement for proving flights will result

in an increase in both initial and recurring costs. United Express

joins ASA in proposing that FAA recognize the experience level of air

carriers operating under part 135 and permit proving tests to be

conducted during revenue service. United Express further proposes

that the required number of hours be reduced for those carriers

currently using a dispatch system.

Big Sky Airlines recommends a waiver of the requirement for a

proving test for airlines that have a good safety record and proven

experience. The commenter justifies its recommendation on the basis

of excessive and unnecessary burden and cost.

Commuter Air Technology requests clarification concerning which

modifications to specific aircraft would require 100-hour initial

proving tests.

FAA Response: Section 121.163 has two main parts. Paragraph (a)

prohibits a carrier from operating an aircraft type in scheduled

service that has never been used in scheduled service until it has

flown 100 hours of proving flights. These hours are in addition to

any aircraft certification tests. For the purposes of this

rulemaking, the FAA recognizes that the current commuter fleet has

established a sufficient history of operations and does not intend to

require the 100 hours of proving flights for aircraft currently being

operated by those carriers affected by this rulemaking. Paragraph (b)

of § 121.163 requires 50 hours of tests for the carrier to show that

not only can it operate and maintain the aircraft, but also that it

has the ability to conduct a particular kind of operation (i.e.,

domestic or flag) in compliance with the applicable regulatory


The FAA agrees that carriers currently conducting operations

under both part 121 and part 135 (split certificates) will be eligible

to apply for a reduction of the number of hours required to conduct

the demonstration required by paragraph (b). In regard to the comment

that flight crewmembers that are new to part 121 operations will

demonstrate their proficiency during accomplishment of a line check,

the FAA does not agree that this could take the place of proving

flights. The primary focus of proving flights is not simply to test

the proficiency of flight crewmembers but to test the company's

operational control procedures for the airplanes that will be operated

in accordance with the requirements for a new kind of operation, i.e.,

flag or domestic. The FAA supports the idea that proving flight hours

should be reduced based on "experience and performance" factors. The

FAA has begun to identify those specific procedures for which proving

flights would be required and to specify a realistic number of flights

or flight hours which would be sufficient to demonstrate those

procedures. This guidance to FAA inspectors will be provided in a

revision to Order 8400.10.

The FAA agrees that proving tests will require an expenditure of

the carrier's financial resources. Safety requires these proving

tests to determine that an operator can conduct operations under part

121 safely, using new procedures, dispatches, etc. The FAA recognizes

the experience level of air carriers operating under part 135 and,

based on the carrier's experience with part 121, will provide FSDO

inspectors with written guidance on approving deviations from the

requirements of § 121.163. The FAA believes that proving tests are an

essential part of the certification process and also provide the

carrier with an opportunity to do some "dry-runs" before beginning

revenue service under a completely new set of regulatory standards.

The FAA's intent is to provide inspectors with the authority to

provide deviations from the proving test requirements. FAA

Headquarters will review each proposed reduction of proving test hours

and will concur or not concur with the proposed number of hours for

each affected commuter.

In response to Commuter Air Technology's request for

clarification concerning which modifications to specific aircraft

would require 100 hour initial proving tests, § 121.163(d) contains

criteria for when a type of aircraft is considered to be materially

altered in design.