Airworthiness Directives; General Dynamics (Convair) Model 240 Series Airplanes, Including Model T-29 (Military) Airplanes; Model 340 and 440 Series Airplanes; and Model C-131 (Military) Airplanes; Including Those Modified for Turbo-Propeller Power

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 95-NM-19-AD; Amendment 39-9501; AD 96-03-04]

Airworthiness Directives; General Dynamics (Convair) Model 240

Series Airplanes, Including Model T-29 (Military) Airplanes; Model 340

and 440 Series Airplanes; and Model C-131 (Military) Airplanes;

Including Those Modified for Turbo-Propeller Power

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD),

applicable to various General Dynamics (Convair) airplanes, that

requires revising the Airplane Flight Manual to require that the flight

crew limit the flap settings during certain icing conditions and air

temperatures. This amendment is prompted by reports indicating that

incidents involving uncommanded pitch excursions have occurred due to

ice contaminated tailplane stall (ICTS) that occurred during or

following flight in icing conditions. If flap settings are increased

for landing when conditions for ICT S are present, elevator control

could be affected adversely and the airplane could descend

uncontrollably. The actions specified by this AD are intended to ensure

that the flight crew is advised of the potential hazard related to

increasing the flap settings when conditions for ICTS are present, and

the procedures necessary to address it.

EFFECTIVE DATE: February 28, 1996.

ADDRESSES: Information pertaining to this rulemaking action may be

examined at the Federal Aviation Administration (FAA), Transport

Airplane Directorate, Rules Docket, 1601 Lind Avenue SW., Renton,

Washington; or at the FAA, Los Angeles Aircraft Certification Office,

Transport Airplane Directorate, 3960 Paramount Boulevard, Lakewood,

California.

FOR FURTHER INFORMATION CONTACT: Andrew Gfrerer, Aerospace Engineer,

Systems and Equipment Branch, ANM-130L, FAA, Transport Airplane

Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount

Boulevard, Lakewood, California 90712; telephone (310) 627-5338; fax

(310) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal

Aviation Regulations (14 CFR part 39) to include an airworthiness

directive (AD) that is applicable to various General Dynamics (Convair)

airplanes was published in the Federal Register on June 16, 1995 (60 FR

31648). That action proposed to require revising the FAA-approved

Airplane Flight Manual (AFM) to require that the flight crew limit the

flap settings during certain icing conditions and air temperatures.

Interested persons have been afforded an opportunity to participate

in the making of this amendment. Due consideration has been given to

the comments received.

One commenter supports the proposed rule.

One commenter supports the proposed rule, but believes that an

allowance should be made for using a setting of greater than flaps 30

after icing conditions have been encountered if outside air

temperatures in the landing area are well above freezing. The commenter

indicates that icing conditions may be encountered at cruising

altitudes, but the ground temperatures could be much warmer. The

commenter believes that there is virtually no chance that ice would

remain on the tail. From the commenter's experience, all ice that has

collected on the wing leading edges, engine nacelles, windscreens, and

windshield wipers will have disappeared by the time the indicating

outside air temperature has reached +5 degrees Celsius on descent.

In light of these remarks, the commenter suggests that the AFM

revision required by paragraph (a) of the proposed rule be reworded as

follows:-

``Flap selection is limited to a maximum of 30 degrees after icing

conditions have been encountered if the indicated OAT on approach is +5

degrees Celsius or lower; or if icing conditions are anticipated during

approach and landing; or when the outside air temperature is +5 degrees

Celsius or below and any visible moisture is present.''

The FAA does not concur with the commenter's suggestion. Operators

cannot generally assume that accreted ice will not be present on wings

and tailplanes if the outside air temperatures are above +5 degrees

Celsius on approach. Ice sublimation, melting, and shedding are not

only functions of temperature, but also are dependent upon other

factors such as the nature, size, and extent of ice accretion;

operation of ice protection systems; time of flight in temperatures

above freezing; and airplane speed.

The commenter's concern regarding incurring a flap extension

limitation after encountering, and then departing, icing conditions has

merit. However, the airplane must be free of ice before the flaps are

extended to greater than 30 degrees. Since ice can accrete on

tailplanes with a small leading edge radius when there is no evidence

of ice accretion on the wings, a method of visual inspection of the

wings, tailplanes, and/or proven ice detectors or ice evidence probes

would be necessary to assure clean surfaces.

One commenter requests that the proposed AD be withdrawn. The

commenter states that the airplane can be operated quite safely within

the environment to which it is certified when the anti-icing system is

operational and functioning, and when that system is used in the manner

in which it was intended.-

The FAA does not concur with the commenter's request. Test pilots

of Convair Model 5800 series airplanes actually experienced evidence of

ice contaminated tailplane stall (ICTS) during pushover maneuver flight

tests. (Model 5800 series airplanes are similar to Model 340 series

airplanes equipped with turbo-prop engines.) For this reason the type

certificate holder agreed with the FAA that a flap extension

restriction during operation in icing conditions is necessary. The

specific flight test used to determine susceptibility to ICTS is a

pushover maneuver to generate an increased angle of attack on the

horizontal tailplane. This maneuver is performed with ice shapes on the

tailplane and flaps in approach and landing positions, at speeds from

near approach to maximum for the configurations. The test procedure

requires a push force throughout the maneuver to zero load factor. A

force reversal would be indicative of an elevator hinge moment reversal

caused by airflow separation due to accreted ice and an increased angle

of attack due to pitch rate, and would define the aircraft as

susceptible to ICTS. Because all affected Convair airplane models have

tailplane designs that are similar to the model tested, this AD

requires a flap limitation.-

The FAA has revised this final rule to clarify that the unsafe

condition

[[Page 2706]]

specified in this AD can occur if the flap settings are increased when

conditions for ICTS are present.

After careful review of the available data, including the comments

noted above, the FAA has determined that air safety and the public

interest require the adoption of the rule as proposed.

There are approximately 282 Model 240 series airplanes, including

Model T-29 (military) airplanes; Model 340 and 440 series airplanes;

Model C-131 (military) airplanes, and those models modified for turbo-

propeller power; of the affected design in the worldwide fleet. The FAA

estimates that 197 airplanes of U.S. registry will be affected by this

AD, that it will take approximately 1 work hour per airplane to

accomplish the required actions, and that the average labor rate is $60

per work hour. Based on these figures, the cost impact of the AD on

U.S. operators is estimated to be $11,820, or $60 per airplane.-

The cost impact figure discussed above is based on assumptions that

no operator has yet accomplished any of the requirements of this AD

action, and that no operator would accomplish those actions in the

future if this AD were not adopted.

The regulations adopted herein will not have substantial direct

effects on the States, on the relationship between the national

government and the States, or on the distribution of power and

responsibilities among the various levels of government. Therefore, in

accordance with Executive Order 12612, it is determined that this final

rule does not have sufficient federalism implications to warrant the

preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is

not a ``significant regulatory action'' under Executive Order 12866;

(2) is not a ``significant rule'' under DOT Regulatory Policies and

Procedures (44 FR 11034, February 26, 1979); and (3) will not have a

significant economic impact, positive or negative, on a substantial

number of small entities under the criteria of the Regulatory

Flexibility Act. A final evaluation has been prepared for this action

and it is contained in the Rules Docket. A copy of it may be obtained

from the Rules Docket at the location provided under the caption

ADDRESSES.

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the

Administrator, the Federal Aviation Administration amends part 39 of

the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES -

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by adding the following new

airworthiness directive:

96-03-04 General Dynamics (Convair): Amendment 39-9501. Docket 95-

NM-19-AD.

Applicability: All Model 240 series airplanes, including Model

T-29 (military) airplanes; Model 340 and 440 series airplanes; and

Model C-131 (military) airplanes; including those models modified

for turbo-propeller power (commonly referred to as Model 580, 600,

and 640 series airplanes); certificated in any category.

Compliance: Required as indicated, unless accomplished

previously.

To ensure that the flight crew is advised of the potential

hazard associated with increasing the flap settings when ice

contaminated tailplane stall (ICTS) conditions are present, and the

procedures necessary to address it, accomplish the following:

(a) Within 30 days after the effective date of this AD, revise

the Limitations Section of the FAA-approved Airplane Flight Manual

(AFM) to include the following procedures, which will limit the flap

settings during certain icing conditions and air temperatures. This

may be accomplished by inserting a copy of this AD in the AFM.

``FLAP LIMITATION IN ICING CONDITIONS

Flap selection is limited to a maximum of 30 degrees after icing

conditions have been encountered; or when icing conditions are

anticipated during approach and landing; or when the outside air

temperature is +5 degrees Celsius or below and any visible moisture

is present.''

(b) An alternative method of compliance or adjustment of the

compliance time that provides an acceptable level of safety may be

used if approved by the Manager, Los Angeles Aircraft Certification

Office (ACO), FAA, Transport Airplane Directorate. Operators shall

submit their requests through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Los Angeles ACO.

Note: Information concerning the existence of approved

alternative methods of compliance with this AD, if any, may be

obtained from the Los Angeles ACO.

(c) Special flight permits may be issued in accordance with

sections 21.197 and 21.199 of the Federal Aviation Regulations (14

CFR 21.197 and 21.199) to operate the airplane to a location where

the requirements of this AD can be accomplished.

(d) This amendment becomes effective on February 28, 1996.

Issued in Renton, Washington, on January 23, 1996.

Darrell M. Pederson,

Acting Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 96-1517 Filed 1-26-96; 8:45 am]

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