AD 95-04-13 Airworthiness Directives; Robinson Helicopter Company Model R44 Helicopters

Makes named: robinson. Models named: R44. Read the applicability below — it usually turns on serial or part numbers too.

Model R44 helicopters, certificated in any category.

Required before further flight, unless accomplished previously. To prevent main rotor (M/R) stall or mast bumping, which could result in the M/R blades contacting the fuselage causing failure of the M/R system and subsequent loss of control of the helicopter, accomplish the following: (a) Insert the following information into the Model R44 Rotorcraft Flight Manual, revised September 6, 1994. Compliance with the Limitations section is mandatory. The Normal Procedures and Emergency Procedures sections are informational. Limitations Section (1) Flight when surface winds exceed 25 knots, including gusts, is prohibited. (2) Flight when surface wind gust spreads exceed 15 knots is prohibited. (3) Flight in wind shear is prohibited. (4) Flight in moderate, severe, or extreme turbulence is prohibited. (5) Adjust forward airspeed to between 60 knots and 0.7 V ne but no lower than 60 knots upon inadvertently encountering moderate, severe, or extreme turbulence. Note: Moderate turbulence is turbulence that causes: (1) Changes in altitude or attitude; (2) variations in indicated airspeed; and (3) aircraft occupants to feel definite strains against seat belts. Normal Procedures Section Note Until the FAA completes its research into the conditions and aircraft characteristics that lead to main rotor blade/fuselage contact accidents, and corrective type design changes and operating limitations are identified, R44 pilots are strongly urged to become familiar with the following information and comply with these recommended procedures. Main Rotor Stall: Many factors may contribute to main rotor stall and pilots should be familiar with them. Any flight condition that creates excessive angle of attack on the main rotor blades can produce a stall. Low main rotor RPM, aggressive maneuvering, high collective angle (often the result of high-density altitude, over- pitching [exceeding power available] during climb, or high forward airspeed) and slow response to the low main rotor RPM warning horn and light may result in main rotor stall. The effect of these conditions can be amplified in turbulence. Main rotor stall can ultimately result in contact between the main rotor and airframe. Additional information on main rotor stall is provided in the Robinson Helicopter Company Safety Notices SN-10, SN-15, SN-20, SN- 24, SN-27, and SN-29. Mast Bumping: Mast bumping may occur with a teetering rotor system when excessive main rotor flapping results from low ``G'' (load factor below 1.0) or abrupt control input. A low ``G'' flight condition can result from an abrupt cyclic pushover in forward flight. High forward airspeed, turbulence, and excessive sideslip can accentuate the adverse effects of these control movements. The excessive flapping results in the main rotor hub assembly striking the main rotor mast with subsequent main rotor system separation from the helicopter. To avoid these conditions, pilots are strongly urged to follow these recommendations: [[Page 11613]] (1) Maintain cruise airspeeds greater than 60 knots indicated airspeed and less than 0.9 V ne, but no lower than 60 knots. (2) The possibility of rotor stall is increased at high density altitudes; therefore, avoid flight at high density altitudes. (3) Use maximum ``power-on'' RPM at all times during powered flight. (4) Avoid sideslip during flight. Maintain in-trim flight at all times. (5) Avoid large, rapid forward cyclic inputs in forward flight, and abrupt control inputs in turbulence. Emergency Procedures Section (1) RIGHT ROLL IN LOW ``G'' CONDITION Gradually apply aft cyclic to restore positive ``G'' forces and main rotor thrust. Do not apply lateral cyclic until positive ``G'' forces have been established. (2) UNCOMMANDED PITCH, ROLL, OR YAW RESULTING FROM FLIGHT IN TURBULENCE. Gradually apply controls to maintain rotor RPM, positive ``G'' forces, and to eliminate sideslip. Minimize cyclic control inputs in turbulence; do not over control. (3) INADVERTENT ENCOUNTER WITH MODERATE, SEVERE, OR EXTREME TURBULENCE. If the area of turbulence is isolated, depart the area; otherwise, land the helicopter as soon as practical. (b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used when approved by the Manager, Rotorcraft Standards Staff, FAA, Rotorcraft Directorate. Operators shall submit their requests through an FAA Principal Operations Inspector, who may concur or comment and then send it to the Manager, Rotorcraft Standards Staff. Note: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Rotorcraft Standards Staff. (c) Special flight permits, pursuant to sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199), will not be issued. (d) This amendment becomes effective on March 17, 1995. Issued in Fort Worth, Texas, on February 23, 1995. Eric Bries, Acting Manager, Rotorcraft Directorate, Aircraft Certification Service. [FR Doc. 95-5096 Filed 3-1-95; 8:45 am] BILLING CODE 4910-13-P