AD 94-25-03

This amendment adopts a new airworthiness directive (AD) that is applicable to all Fokker Model F28 series airplanes. This action requires a revision to the Airplane Flight Manual that prohibits takeoff in certain icing conditions unless either a tactile inspection is performed or specific takeoff procedures are followed. This amendment is prompted by several accidents in which Fokker Model F28 series airplanes lost aerodynamic lift when attempting takeoff with ice contamination on their wings. The actions specified in this AD are intended to prevent degradation of aerodynamic lift during takeoff when icing conditions exist.

Final rule; request for comments

94-25-03 FOKKER: Amendment 39-9087. Docket 94-NM-174-AD.

Applicability: All Model F28 series airplanes (all Marks and all serial numbers), certificated in any category.

Compliance: Required as indicated, unless accomplished previously.

To prevent degradation of aerodynamic lift during takeoff when icing conditions exist, accomplish the following:

(a) Within 10 days after the effective date of this AD, incorporate the following into the Limitations Section of the FAA-approved Airplane Flight Manual (AFM). This may be accomplished by inserting a copy of this AD in the AFM.

"Wing De-Icing/Anti-Icing Prior To Takeoff

CAUTION
The Model F28 series airplane has a wing design with no leading edge high
lift devices, such as slats. Wings without leading edge high lift devices are
particularly susceptible to loss of lift due to wing icing. Minute amounts of
ice or other contamination (equivalent to medium grit sandpaper) on the
leading edges or upper wing surfaces can cause significant reduction in
the stall angle-of-attack. This can increase stall speed up to 30 knots. The increased stall speed can be well above the stall warning (stick shaker)
activation speed.

Takeoff shall not be attempted unless the pilot-in-command has ensured that the
aircraft surfaces are free of ice, frost, and snow accumulation, as required by
sections 91.527 and 121.629 of the Federal Aviation Regulations (FAR).

In addition, takeoff shall not be attempted when the Outside Air Temperature (OAT)
is below 6 degrees C (Centigrade) [42 degrees F (Fahrenheit)]; and either the
difference between the dew point temperature and OAT is less than 3 degrees C (5
degrees F), or visible moisture (rain, drizzle, sleet, snow, fog, etc.) is present,
unless the operator complies with either OPTION 1 or OPTION 2, below:

OPTION 1
The leading edge and upper wing surfaces have been physically checked forice/frost/snow and the flight crew verifies that a visual check and a physical
(hands-on) check of the leading edge and upper wing surfaces has been
accomplished and that the wing is clear of ice/frost/snow accumulation.

OR
OPTION 2
The following takeoff procedure is used:

WARNING:
The following technique cannot be used unless the pilot-in-command has ensured
that the aircraft surfaces are free of ice, frost, and snow, as required by sections
91.527 and 121.629 of the FAR.

(All Marks, except Mark 0100 and Mark 0070) When using flight director for takeoff, select HDG mode and 10 degrees pitch attitude.

Select the largest flap setting that is permissible for the takeoff weight / altitude / temperature conditions.

(All Marks, except Mark 0100 and Mark 0070) Use rated takeoff thrust.

(Mark 0100 and Mark 0070) Use takeoff/go-around (TOGA) thrust.

Do not use FLEXIBLE thrust.

At VR rotate slowly (less than 3 degrees per second) to10 degrees pitch attitude.

When positively climbing, select gear UP.

DO NOT EXCEED 10 DEGREES PITCH UNTIL AIRSPEED IS ABOVE V2 + 20 KTS.

When above V2 + 20 KTS, slowly increase the pitch attitude, keeping the speed above V2 + 20 KTS.

Retract the flaps at or above VFR + 20 KTS.

NOTES TO OPTION 2:
1. The available field length must be greater than or equal to 120 percent of the takeoff distance required by regulation for the actual gross weight. Also, the 20 percent increase in takeoff distance must be accounted for in the obstacle clearance analysis. WEIGHT MUST BE OFF-LOADED, IF NECESSARY, TO MEET THESE CONDITIONS.

2. (Mark 0100 and Mark 0070) Do not follow the Flight Director pitch command during rotation for takeoff and initial climb, as this will result in exceeding the recommended maximum pitch angle of 10 degrees before reaching the speed of V2 + 20 KTS.

3. (Mark 0100 and Mark 0070) Do not engage the auto-pilot until leaving the Automated Flight Control and Augmentation System (AFCAS) takeoff (TO) mode.

4. For the case of an engine failure, refer to the applicable procedure in Section 4.17.01 SINGLE ENGINE OPERATION of the F28 Mark 0100 (Fokker 100) and F28 Mark 0070 (Fokker 70) AFM, or Section 1.7.4 OPERATION UNDER ABNORMAL CONDITIONS of the F28 FHB, as applicable.

5. During takeoff, the first indication of wing contamination will probably be airframe buffet when the pitch angle is increased above 10 degrees, followed by wing drop and insufficient climb rate. DO NOT EXCEED 10 DEGREES PITCH UNTIL AIRSPEED IS ABOVE V2 + 20 KTS."

NOTE 1: If an operator elects to implement in its fleet only one of the two OPTIONS specified in this paragraph, the other OPTION does not have to be included in the Limitations Section of the AFM. However, the OPTION that is implemented must be incorporated in the AFM verbatim as it appears in this paragraph.

(b) Modification of the thermal anti-ice system so that it can be operated on the ground, in accordance with a method approved by the Manager, Standardization Branch, ANM-113, FAA, Transport Airplane Directorate, constitutes terminating action for the requirements of this AD.

NOTE 2: Incorporation of the leading edge thermal anti-ice modification and associated operating instructions does not relieve the requirement that aircraft surfaces are free of ice, frost, and snow accumulation as required by sections 91.527 and 121.629 of the Federal Aviation Regulations (14 CFR 91.527 and 121.629).

(c) 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, Standardization Branch, ANM-113. Operators shall submit their requests through an appropriate FAA Principal Operations Inspector, who may add comments and then send it to the Manager, Standardization Branch, ANM-113.

NOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Standardization Branch, ANM-113.

(d) 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.

(e) This amendment becomes effective on December 21, 1994.

The FAA has received reports of at least three accidents involving Fokker Model F28 series airplanes in which the probable cause has been attributed to wing ice contamination prior to takeoff. The FAA has determined that airplanes with wings that do not have leading edge high lift devices, such as the Fokker Model F28 series airplanes, are particularly susceptible to loss of lift when attempting to take off with minimal amounts of ice accumulation (contamination) on the wings. Further, the FAA finds that airplanes with this configuration account for a disproportionate number of the total number of accidents attributable to wing ice contamination. In light of this, the FAA has determined that, for airplanes with this configuration, an extra degree of protection is necessary beyond reliance solely on operation in accordance with the current requirements specified in section 121.629 ("Operation in icing conditions"), amendment 121-231, of the Federal Aviation Regulations (14 CFR 121.629).

The FAA has determined that one acceptable (interim) method of addressing icing problems associated with airplanes having this configuration is a physical (tactile) and visual check of the leading edge and upper wing surfaces to verify that there is no accumulation of ice, frost, and snow prior to takeoff. The FAA previously issued AD 93-11-01 [amendment 39-8593 (58 FR 33898, June 22, 1993)], which requires such a tactile check of McDonnell Douglas Model DC-9-10 series airplanes; those airplanes, like the Model F28, do not have leading edge high lift devices. The intent of checks such as these is to prevent takeoff with wing ice contamination, which can result in the degradation of wing lift, and can result in the airplane stalling at lower than normal angles-of-attack during takeoff.

Additionally, the Rijksluchtvaartdienst (RLD), which is the airworthiness authority for the Netherlands, issued Netherlands Airworthiness Directive (BLA) 93-167/2 (A), dated April 29, 1994, applicable to Fokker Model F28 series airplanes operating in the Netherlands. This BLA describes an "alternative" takeoff procedure that can be followed to improve stall margins whenever icing conditions exist. [This "alternative" takeoff procedure was developed in response to the U.S. National Transportation Safety Board's (NTSB) Safety Recommendation A-93-023.] The "alternative" takeoff procedure requires the availability of 120 percent of the minimum takeoff distance for the actual gross weight. Additionally, the 20 percent increase in takeoff distance must be accounted for in the obstacle clearance analysis. The BLA specifies that the "alternative" takeoff procedure is an optional procedure that is available for use when sufficient runway length and obstacle clearance margin are available.

The FAA has reviewed and approved this "alternative" takeoff procedure as an interim measure that will acceptably address the problems associated with takeoff and operation of Model F28 series airplanes in icing conditions. Although the RLD has classified the procedure as optional, the FAA has determined that it must be mandated as one method to ensure that these airplanes have adequate lift to effect a safe takeoff when icing conditions exist.

As indicated previously, the FAA has determined that the accomplishment of these types of additional actions is necessary in order to provide an extra degree of protection for Model F28 series airplanes, beyond that provided by the current operating requirements specified in part 121 of the FAR.

Fokker has advised the FAA that it is currently developing a modification to the thermal anti-ice system on all Fokker Model F28 series airplanes. This modification would allow the thermal anti-ice system to operate on the ground, which would prevent reformation of ice on the wing leading edges after ground equipment has been used to properly de-ice/anti-ice the airplane, and would minimize the effect of undetected ice/frost/snow contamination. Fokker has indicated that this proposed modification will be similar to the one required by AD 93-11-01 for McDonnell Douglas DC-9-10 series airplanes. (That AD requires a modification of the wing leading edge bleed air anti-ice system on so that it can operate on the ground to prevent the reformation of ice after de-icing procedures have been accomplished.) However, because this proposed modification for Model F28 series airplanes currently is under development, any associated modification instructions or required parts are not available at this time.

This airplane model is manufactured in the Netherlands and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. The FAA has determined that AD action is necessary for products of this type design that are certificated for operation in theUnited States.

Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent degradation of the aerodynamic lift during takeoff due to wing ice contamination, which could result in the airplane stalling at lower than normal angles-of-attack during takeoff. This AD requires a revision to the Limitations Section of the FAA-approved Airplane Flight Manual (AFM), which requires that, whenever icing conditions exist, one of the following actions must be accomplished:

1. A physical (tactile) check to detect ice, frost, and snow accumulation on the leading edge and upper wing surfaces must be performed prior to takeoff. (This check is similar to that required by AD 93-11-01 for McDonnell Douglas Model DC-9-10 series airplanes). Or

2. The airplane must be operated in accordance with the "alternative" takeoff procedure developed by Fokker that improves stall margins. Use of the "alternative" takeoff procedure would require weight to be off loaded, if necessary, to meet the revised takeoff distance and obstacle clearance requirements.

This AD also provides for the termination of these requirements if the airplane's thermal anti-ice system is modified and operated in accordance with a method approved by the FAA.

This is considered to be interim action. As stated previously, Fokker currently is developing a design modification that will positively address the unsafe condition that is the subject of this rulemaking action. Once this modification, as well as its associated operating procedures and an implementation schedule, are developed, approved, and available, the FAA may consider additional rulemaking action.

Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for makingthis amendment effective in less than 30 days.

Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules

Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 94-NM-174-AD." The postcard will be date stamped and returned to the commenter.

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 determinedthat this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: