[Federal Register Volume 61, Number 19 (Monday, January 29, 1996)]
[Rules and Regulations]
[Pages 2705-2706]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-1517]



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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]
BILLING CODE 4910-13-U