407GX · GXP · GXi

A blocked oil line restrictor in the freewheel lubrication system can cause unsafe conditions. This AD requires inspecting and cleaning the oil supply restrictor to the freewheel assembly.

In-flight tail rotor drive system failures have occurred on Bell 407 helicopters. This AD requires repetitive inspections of the tail rotor driveshaft segment assemblies and torque checks of the tail rotor adapter retention nuts.

Driveshafts on certain Bell helicopters may crack or develop loose fasteners, which could cause loss of main rotor drive and force an emergency landing. This AD requires inspection of affected driveshafts for cracks, loose fasteners, or red powder residue, with replacement if any defects are found.

Cracks have been reported in the upper left-hand longeron of Model 407 helicopters, which could lead to structural failure and loss of control. This AD requires inspecting the aft fuselage upper skin and upper left longeron assembly for cracks, corrosion, or defects, and replacing or repairing affected parts based on inspection results.

Cracks have been found in tailboom skins on certain Bell 407 helicopters, which could lead to tailboom separation and loss of control. This AD requires preflight checking and repetitive inspections of the tailboom, replacement if cracked, modification of certain tailbooms, installation of an improved horizontal stabilizer assembly, and compliance with a 5,000 hour time-in-service limit.

Emergency floats on certain Bell helicopters may fail to deploy due to defective inflation hoses. This AD requires inspecting, labeling, and replacing the float inflation hoses to ensure the emergency flotation system functions properly.

Several Bell 407 helicopters experienced third stage engine turbine wheel failures caused by excessive vibrations at certain engine speeds during steady-state operations. This AD requires installing a placard beneath the NR/NP dual tachometer and revising the rotorcraft flight manual limitations section to alert pilots to avoid those engine speeds.

Certain freewheel aft bearing caps were manufactured without a lubrication channel, which could cause freewheel unit failure and loss of helicopter control. This AD requires replacing or reworking the affected aft bearing caps.

Bearings in certain Bell helicopters may not be properly staked and can migrate from their correct position, potentially causing bearing and assembly failure and loss of helicopter control. This AD requires inspecting each bearing to verify proper staking and replacing any bearing or assembly that is not properly staked.

The tailboom assembly on certain Model 407 helicopters has high-stress areas susceptible to skin cracking, which could lead to tailboom failure and loss of control. This AD requires periodic inspections of the tailboom assembly for cracks, loose rivets, or other damage.

Tailboom-attachment bolts on certain helicopters were over-torqued during manufacturing, risking bolt failure and loss of the tailboom. This AD requires replacement of the attachment hardware and initial and recurring torque checks on all four tailboom-attachment bolt locations.

Certain hydraulic servo actuators in these helicopters may have loose or misaligned internal parts that could cause servo failure and loss of control. The AD requires inspecting all servos to detect potential failures and marking compliant servos with the letter 'V' on the data plate.

Helicopter occupants may not be aware of the location and operation of external liferaft inflation handles, preventing proper deployment during water emergencies. The AD requires adding placards to identify the location and operation of liferaft external inflation handles and replacing liferaft operation placards to state that external liferafts are installed.

Tail rotor blade tip weights can separate from blades during flight, causing vibration and potential loss of control. This AD requires inspection and replacement of affected tail rotor blades to prevent blade loss.

Some hydraulic pump driveshaft assemblies may be missing an internal plug or fastening rivet, which could cause loss of hydraulic pressure and helicopter control. Operators must inspect and correct affected driveshaft assemblies.

The swashplate link assembly bearing may not have been staked correctly during manufacture, causing it to move in the lever race and potentially fail, resulting in loss of helicopter control. Operators must perform a preflight check of the swashplate link assembly bearing and ensure it is properly staked.

A bearing may be incorrectly installed in the cyclic control lever assembly, which could lead to bearing failure and loss of helicopter control. Before further flight, inspect each cyclic control lever assembly with less than 50 hours time-in-service to verify it is correctly installed and properly staked.

Certain tail rotor blade tip weights may depart from the blade during flight due to missing adhesive on the tip weight screw, affecting helicopter controllability and structural integrity. Operators must replace affected blades with airworthy blades that do not have serial numbers listed in the Rotor Blades, Inc. document attached to the applicable Bell Helicopter service bulletins.

Horizontal stabilizers on certain Bell helicopters may have manufacturing flaws that lead to skin cracking and structural failure. The AD requires inspection and correction of these defects to prevent horizontal stabilizer failure.

Fuel nozzle screens can contaminate and collapse, causing sudden loss of engine power and uncommanded shutdown. This AD requires inspection of the fuel nozzle screen for contamination and replacement of affected fuel nozzles with a new design, with cleaning of the aircraft fuel system if contamination is found.

Run-on landings create high stress on landing gear crosstubes and may cause cracking above the skid tube saddle, potentially leading to fatigue failure and loss of control. This AD requires creating component history records for each crosstube assembly and tracking accumulated Retirement Index Numbers to establish maximum limits for affected parts.

Bearing failures have occurred in oil cooler blower assemblies and segmented tail rotor drive shaft assemblies, risking loss of tail rotor drive and directional control. This AD requires modifying inlet ducts and airflow shields, replacing affected bearings, updating rotorcraft flight manual limitations, and revising inspection and lubrication procedures.

Incorrectly installed swashplate drive link cup washers can limit swashplate travel and cause drive link stud failure, leading to loss of helicopter control. Owners/operators must visually check that cup washers are installed correctly; if incorrect installation is found, the swashplate outer ring, cup washers, bearings, liners, and drive links must be replaced.

Cracks have been discovered in tailboom gearbox support castings that could lead to loss of the vertical fin, tail rotor, and helicopter control. Inspect certain tailboom castings for cracks and replace the tailboom assembly if any crack is found.

Cracked brackets on horizontal stabilizer slat assemblies could cause a slat to separate and strike a rotor blade, risking loss of control. The AD requires periodic inspections of slat brackets for cracks, replacement of defective assemblies, and installation of identification plates on certain helicopters.

Breeze Eastern Aerospace rescue hoists have experienced cracked mounting brackets that could separate the hoist from the helicopter. Perform a one-time inspection of mounting brackets for cracks and replace with serviceable parts if necessary.

Electrical bonding of the fuel filler cap assembly may be inadequate, potentially allowing electrical arcs that could ignite fuel vapors and cause an onboard fire. This AD requires shimming and electrical bonding procedures for the fuel filler cap assembly.

Cracks have been found in the forward hanger bearing bracket of certain Model 407 helicopters, which could cause loss of tail rotor drive and control. The AD requires visual inspection of the bracket for cracks.

Pilots have had difficulty distinguishing between different cockpit warning horns, which could lead to inappropriate responses and engine problems. The AD requires replacing certain cockpit warning horns to help pilots properly identify specific warnings.

This AD rescinds previous restrictions on never exceed velocity (Vne) for Model 407 helicopters that were imposed to prevent tail rotor strikes. The FAA determined that accident investigation findings did not support that high-airspeed tail rotor strikes caused the accident, so the Vne restrictions are no longer required.

A manufacturing defect in a hydraulic relief valve can cause intermittent loss of hydraulic pressure to flight controls, risking loss of helicopter control. Replace the affected hydraulic relief valve with a different valve.

Some Model 407 helicopter vertical fins may have reduced skin thickness from production damage, which could weaken the fin and lead to loss of control. The AD requires visual inspection of the fin for reduced skin thickness and repair or replacement if necessary.

The engine-to-transmission driveshaft on Model 407 helicopters has a shorter life limit than stated in the maintenance manual, which could lead to driveshaft failure and loss of control. This AD requires replacing the driveshaft with an airworthy one before 50 hours of engine time-in-service.

BFGoodrich SKYWATCH SKY497 installations with top-mounted antennas can experience internal component failure that changes the antenna configuration, causing target indicators to display on the wrong side of the aircraft. This AD requires verifying correct antenna configuration at power-up and removing from service any installations with incorrect antenna configuration.

Cracking in the tail rotor drive system bearing support arms can lead to excessive vibration and loss of tail rotor drive, risking loss of helicopter control. The AD requires shimming the bearing support structures to prevent failure.

Electronic control units (ECUs) in these engines can develop corrosion on internal connectors, causing hard faults that lead to uncommanded inflight engine shutdowns and potential loss of the helicopter. The AD requires installing ECUs with improved corrosion resistance and implementing other previously mandated modifications including harness replacement, HMU and ECU installation, and flight manual revisions.

The tail rotor drive system on Model 407 helicopters can suffer scratches, cracks, fretting, corrosion, and loose fasteners that may cause loss of tail rotor power and helicopter control. This AD requires inspections of tail rotor drive components, lubrication of hanger bearings, and removal of barrier tape from the tail rotor gearbox.

Allison Model 250-C47B engines have experienced uncommanded inflight shutdowns due to electrical harness and control unit issues. This AD requires replacement of the main electrical harness, disabling the overspeed solenoid, inspecting and replacing defective engine control units, and adding a placard to notify pilots that overspeed protection is disabled.