Airworthiness Directives; Gulfstream American (Frakes Aviation) Model G-73 (Mallard) and G-73T Series Airplanes

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-141-AD; Amendment 39-11296; AD 99-19-07]

RIN 2120-AA64

Airworthiness Directives; Gulfstream American (Frakes Aviation)

Model G-73 (Mallard) and G-73T Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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

applicable to certain Gulfstream American (Frakes Aviation) Model G-73

(Mallard) and G-73T series airplanes, that requires revising the

Airplane Flight Manual (AFM) to include requirements for activation of

the airframe pneumatic deicing boots. This amendment is prompted by

reports of inflight incidents and an accident that occurred in icing

conditions where the airframe pneumatic deicing boots were not

activated. The actions specified by this AD are intended to ensure that

flightcrews activate the pneumatic wing and tail deicing boots at the

first signs of ice accumulation. This action will prevent reduced

controllability of the aircraft due to adverse aerodynamic effects of

ice adhering to the airplane prior to the first deicing cycle.

EFFECTIVE DATE: December 27, 1999.

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, Rotorcraft Directorate, 1601 Meacham

Boulevard, Fort Worth, Texas.

FOR FURTHER INFORMATION CONTACT: Efran Esparza, Aerospace Engineer,

Airplane Certification Office, ASW-150, FAA, Rotorcraft Directorate,

1601 Meacham Boulevard, Fort Worth, Texas 76137-4298; telephone (817)

222-5130; fax (817) 222-5960.

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 certain Gulfstream American

(Frakes Aviation) Model G-73 (Mallard) and G-73T series airplanes was

published in the Federal Register on July 16, 1999 (64 FR 38355). That

action proposed to require revising the Airplane Flight Manual (AFM) to

include requirements for activation of the airframe pneumatic deicing

boots.

Related Proposals

In addition to the proposed rule described previously, in June

1999, the FAA issued 18 other similar proposals that address the

subject unsafe condition on various airplane models (see below for a

listing of all 19 proposed rules). Those 18 proposals also were

published in the Federal Register on July 16, 1999. (Docket 99-NM-153-

AD, for Fokker Model F-27 Mark 100, 200, 300, 400, 500, 600, and 700

series airplanes, was also issued as a supplemental notice of proposed

rulemaking, and published in the Federal Register on August 6, 1999.)

This final rule contains the FAA's responses to all relevant public

comments received for each of these proposed rules.

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Manufacturer airplane model Number Federal Register citation

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Cessna Aircraft Company Models 500, 99-NM-136-AD 64 FR 38374

550, and 560 Series Airplanes.

[[Page 63577]]

Sabreliner Corporation Models 40, 60, 99-NM-137-AD 64 FR 38358

70, and 80 Series Airplanes.

Gulfstream Aerospace Model G-159 Series 99-NM-138-AD 64 FR 38341

Airplanes.

McDonnell Douglas Models DC-3 and DC-4 99-NM-139-AD 64 FR 38325

Series Airplanes.

Mitsubishi Heavy Industries Model YS-11 99-NM-140-AD 64 FR 38371

and YS-11A Series Airplanes.

Gulfstream American (Frakes Aviation) 99-NM-141-AD 64 FR 38355

Model G-73 (Mallard) and G-73T Series

Airplanes.

Lockheed, Models L-14 and L-18 Series 99-NM-142-AD 64 FR 38338

Airplanes.

Fairchild Models F-27 and FH-227 Series 99-NM-143-AD 64 FR 38322

Airplanes.

Aerospatiale Models ATR-42/ATR-72 99-NM-144-AD 64 FR 38368

Series.

Jetstream Model BAe ATP Airplanes...... 99-NM-145-AD 64 FR 38351

Jetstream Model 4101 Airplanes......... 99-NM-146-AD 64 FR 38335

British Aerospace Model HS 748 Series 99-NM-147-AD 64 FR 38319

Airplanes.

Saab Model SF340A/SAAB 340B/SAAB 2000 99-NM-148-AD 64 FR 38365

Series Airplanes.

CASA Model C-212/CN-235 Series 99-NM-149-AD 64 FR 38348

Airplanes.

Dornier Model 328-100 Series Airplanes. 99-NM-150-AD 64 FR 38332

Lockheed Model 1329-23 and 1329-25 99-NM-151-AD 64 FR 38316

(Lockheed Jetstar) Series Airplanes.

de Havilland Model DHC-7/DHC-8 Series 99-NM-152-AD 64 FR 38362

Airplanes.

Fokker Model F-27 Mark 100/200/300/400/ 99-NM-153-AD 64 FR 42870

500/600/700/050 Series Airplanes.

Short Brothers Model SD3-30/SD3-60/SD3- 99-NM-154-AD 64 FR 38329

SHERPA Airplanes.

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Comments

Interested persons have been afforded an opportunity to participate

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

the following comments received.

1. Support for the Rule

One commenter supports the proposed rule.

2. Request To Withdraw the Proposal: No Unsafe Condition

Several commenters request that the proposal be withdrawn because

no unsafe condition exists on certain airplanes. One of these

commenters states that the FAA is merely speculating that the proposed

Airplane Flight Manual (AFM) revision will improve safety. Further, the

commenter contends that the FAA cannot substantiate that the proposed

AFM revision will prevent ice bridging. This same commenter also asks

if the FAA met its own standards by testing the proposed procedure on

each of the affected airplanes.

The FAA does not concur that no unsafe condition exists. As

discussed in the preamble of the proposed rule, the FAA has reviewed

the icing-related incident history of certain airplanes, and has

determined that icing incidents may have occurred because pneumatic

deicing boots were not activated at the first evidence of ice

accretion. As a result, the handling qualities or the controllability

of the airplane may have been reduced due to the accumulated ice. The

FAA also discussed an accident that occurred as a result of the failure

of the flightcrew to activate the wing and tail pneumatic deicing

boots.

Although there may have been no reported cases of incidents or

accidents on a specific airplane model, the potential still exists for

reduced controllability of all airplanes equipped with pneumatic

deicing boots due to adverse aerodynamic effects of ice adhering to the

airplane. This AD addresses this unsafe condition.

Further, ice bridging of deicing boots was considered during

development of the proposed rule. A broad representation of the

aviation community was consulted, including airframe manufacturers, air

carriers, airline pilot associations, airplane owner associations,

deicing boot manufacturers, and National Aeronautics and Space

Administration (NASA). Also, articles readily accessible by the general

piloting community solicited operational information concerning ice

bridging of deicing boots. The FAA considers that the general consensus

of the aviation community is that little or no evidence exists of ice

bridging of deicing boots with current deicing boot designs, and ice

that is not shed after the initial boot cycle continues to increase in

thickness and sheds during subsequent cycles.

In addition, many airplanes equipped with pneumatic deicing boots

to protect the engine are operated when icing conditions are present,

i.e., visible moisture and a specific temperature are observed. As

discussed in Comment #3 (following this response), at least two

airplane manufacturers have issued AFM's that contain procedures to

activate the deicing boots at the first sign of ice accumulation. The

FAA is unaware of any ice bridging problems associated with early

operations of either the airfoil or engine pneumatic deicing boots.

In response to the commenter's question regarding the FAA meeting

its own standards, the FAA infers that the commenter is requesting the

basis for the FAA's determination that the proposed procedures are

safe. Most aircraft certification programs have not considered the

reduced controllability of the aircraft due to adverse aerodynamic

effects of ice adhering to the pneumatic boots. The requirements of

this AD (activation of the deicing boot system at the first sign of ice

formation anywhere on the aircraft, or upon annunciation from an ice

detector system, whichever occurs first, along with the periodic

cycling of the boots) will minimize the ice accretions and thereby

reduce the adverse aerodynamic effects.

3. Request To Withdraw the Proposal: Possible Adverse Effects of

Residual Ice

Several commenters state that deicing boots do the best job of

shedding ice on a single cycle, if ice is permitted to accrete to \1/4\

or \1/2\ inch before activation of the boots. One of these commenters

further contends that the effect of continuous cycling in auto mode may

not produce a clean shed of ice on each activation, and that residual

ice must be taken into consideration before any revision to the AFM is

required. Another commenter states that, although operation in the

continuous mode upon first indication of ice accretion would eliminate

the problem of identification of accretion, the commenter is concerned

that there would then be a potential for degraded performance due to

residual ice.

The FAA does not concur that the proposal should be withdrawn

because of concerns over residual ice. Operation of pneumatic deicing

boots typically results in persistent ice accretions on the boot

surfaces, even when Except if the AFM otherwise specifies that deicing

boots should not be used for certain phases of flight (e.g., take-

off, final approach, and landing), compliance with the following is

required.

Wing and Tail Leading Edge Pneumatic Deicing Boot

System, if installed, must be activated:

[[Page 63584]]

--At the first sign of ice formation anywhere on the aircraft, or

upon annunciation from an ice detector system, whichever occurs

first; and

--The system must either be continued to be operated in the

automatic cycling mode, if available; or the system must be manually

cycled as needed to minimize the ice accretions on the airframe.

The wing and tail leading edge pneumatic deicing boot

system may be deactivated only after completion of an entire deicing

cycle after leaving icing conditions.

(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, Airplane Certification Office, ASW-

150, FAA, Rotorcraft Directorate. The request shall be forwarded

through an appropriate FAA Operations Inspector, who may add

comments and then send it to the Manager, Airplane Certification

Office, ASW-150 ACO.

Note 1: Information concerning the existence of approved

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

obtained from the Airplane Certification Office, ASW-150 ACO.

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

Secs. 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 December 27, 1999.

Issued in Renton, Washington, on November 10, 1999.

John J. Hickey,

Manager, Transport Airplane Directorate, Aircraft Certification

Service.

[FR Doc. 99-30133 Filed 11-19-99; 8:45 am]

BILLING CODE 4910-13-U