Squawk Box 10/03: Turbo Troubles

Clamp on some Mooney exhaust systems proves troublesome for turbo engines


The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.


The FAA is encouraging owners of turbocharged Mooneys to inspect the V-band clamps attached to the turbochargers.The FAAs special airworthiness information bulletin cites a recent fatal accident of a Mooney M20M Bravo in which the tailpipe apparently separated from the turbochargers, allowing hot exhaust gases to be expelled into the engine compartment. The pilot reported smoke and fire in the cockpit before the aircraft crashed short of the airport, killing both aboard.Mooney recommends replacing the multi-segmented V-band clamps at 2,000 hours – the engines TBO – as well as inspecting it at every 100-hour or annual inspection. The clamp should also be inspected any time maintenance is performed on the exhaust system.The FAA also emphasized the need to comply with the torque procedures recommended in the Mooney Service and Maintenance Manual when installing the clamp following maintenance or inspection.

Beech B36TC Bonanza
Improper Clamp Installation

The owner reported he was unable to achieve gear down and locked on approach for landing. He extended the landing gear manually and landed the aircraft without incident.Inspection found an improper heat duct clamp located under the copilot seat had been installed. The larger clamp was tightened and created a pigtail that caught on the landing gear door rod/bellcrank assembly. The assembly forced the clamp off the duct and onto the landing gear relay, shorting the relay and rendering the landing gear inoperative.

Beech 95-B55 Baron
Worn Rudder Pedal

When a broken rudder pedal was found on one of the operators airplanes, technicians investigated other like airplanes in the operators fleet.In one of the other airplanes, the attachment point for the rudder pedal was found excessively worn in the same location as the failure occurred in the original airplane. The failure occurred at the pivot points, and proper inspection requires removing the attachment hardware.

Beech 95-B55 Baron
Contaminated Fuel Cell

The pilots reported consistently finding water in the sumps during preflight inspections, even after theyd been drained on the previous flight.Technicians cleaned and resealed all fuel caps and seat seals, without correcting the problem. Further investigation revealed multiple large wrinkles in the fuel bladders that trapped large amounts of water.The technician complained that there is no way to completely flatten the bladders, as they are physically larger than the wing section where they reside.

Beech C90 King Air
Electrical Terminal Block Failure

The pilot reported that smoke was coming into the cabin from the copilots instrument panel.The technician discovered that the primary wires to the belly terminal block below the center pedestal were loose. The securing nut on the block had backed off and caused the wires to get hot and burn the insulation. He replaced the terminal block and the four wires. Two of the wires went to the number 1 buss and two wires went to the max heat 150-amp circuit breaker at the pilots feet.

Boeing A75N1 Stearman
Cracked Propeller Hub

During an inspection, the propeller was found to be cracked between laminations inside the hub. The manufacturer said the problem may have been caused by fluctuations in the moisture content, which would cause inconsistent torque in the attach bolts. There was no indication the prop was loose. It was also characterized as quite old.

Cessna 172RG
Cracked Landing Gear Actuator

The pilot reported hearing a loud pop when he tried to retract the gear. When he selected gear down, the left main gear dangled. The emergency extension system was ineffective.Upon inspection, technicians determined the left main gear actuator had cracked through its forward mounting bold hole, causing the pinion gear to separate from the rack gear.The failure occurred after complying with an AD that requires new bushings to be installed. Similar cracks were found on two other like airplanes in the operators fleet. The technician speculated that the new bushings may be increasing the stress on the actuators.

Cessna 182N
Cracked Aft Bulkhead

An inspection of the aft bulkhead to comply with AD 72-07-09 found two small cracks at the top of the rudder cable cutout and flange. The inspection had last been done 901 hours earlier. Inspection of the fin spar bolts and the attach fittings found no other damage.The airplane had once been fitted with a banner tow hitch in accordance with an STC, but the hitch had been removed at an unknown time.

Cessna 182S
Loose Vacuum Pump Check Valve

The pilot reported the right vacuum pump warning light was on.The technician disconnected the hose from the right side of the check valve manifold to connect the test kit and discovered two missing rivets, two rivets that were about to fall out, and two rivets that were loose. All of the affected rivets were on the right side, allowing air to leak around the valve diaphragm.

Cessna T206H
Leaking Engine Seal

After a test flight following engine installation, the pilot noticed an oil leak. The engine had just returned from overhaul. Investigation revealed that an oil seal had not been installed.

Cessna 310P
Nose Gear Bellcrank Failure

During a scheduled training flight, the pilot placed the landing gear selector in the up position and heard a loud pop/bang, after which there was no up-and-locked indication for the nose landing gear.However the main landing gear did reveal an up-and-locked indication. He recycled the landing gear with the same results and landed the aircraft with the nose gear retracted.The technician discovered the broken bellcrank idler was causing the nose gear to be disconnected from the gearbox. The FAA Service Difficulty Reporting Program database revealed 17 reports of similar failures.

Cessna 337G Skymaster
Damaged Flap Actuator Control

After receiving an SDR alert, technicians inspected the airplanes flap system and found two cables on both sides were damaged. The cable damage was at the sharp bend of the bellcrank.The cables had to be removed to allow for inspection, which is one reason why they are not inspected more frequently.

Cessna 402C Businessliner
Avionics Master Switch Failure

During climbout, the pilot smelled smoke in the cockpit area. An investigation revealed the smoke was coming from the avionics master switch. He notified the tower before shutting down the avionics master switch.The technician stated the same problem was found on two additional aircraft in their fleet. The FAA Service Difficulty Reporting Program database revealed 29 reports of avionics master switch failures.

Piper PA-28-151 Warrior
Cracked Stabilator Brace

During an inspection, the technician found the diagonal trim brace on the horizontal stabilizer was cracked. It appeared it had been bent out of the way for access. In addition, the stabilizer hinge bolts were missing spacer washers. There was no indication in the logs of the identity of the last person to perform repairs in the area.

Piper PA-28-236 Dakota
Restricting Fuel Selector Cover

The submitter stated that the fuel selector cover is currently secured with three MS24693-39 No. 6 100-degree countersink screws and three FCW6 interior finishing cup washers.According to the submitter, the selector handle will actually chafe across the cup washer when the selector is placed in the left tank position. He feels that it is possible that the handle may become restricted and not allow maximum fuel flow from the left tank.Replacing the cup washer with DW06SS or an equivalent countersunk washer may allow for greater clearance between the cover and the bottom of the selector handle.

Piper PA-31 Navajo
Leaking Fuel System Solenoid

The pilot reporting smelling fuel in the cockpit during a preflight inspection. Further inspection narrowed the smell to the combustion heater area in the right side of the nose section. Technicians found the heater fuel shut off solenoid leaking fuel from the housing.

Piper PA-31 Navajo
Corroded Propeller Blade

The propeller was removed for inspection due to excessive rotational blade movement.Visual inspection revealed extensive corrosion on the blade bearing area and the blade knob was worn beyond limits. In addition, the bearings were corroded and the pitch change fork and blocks were worn. All other parts were found to be acceptable.

Piper PA-34-200T Seneca II
Nose Gear Steering Assembly Failure

After takeoff, the pilot heard a strange noise coming from the nose gear area and noticed the nose gear did not fully retract. After several attempts to lower and raise the landing gear, he elected to land the aircraft knowing that the nose gear was not fully extended.Investigation found the tiller ball had come out of the steering track assembly and locked up on the side of the track.

Zlin 242L
Broken Muffler Baffle

During an inspection, technicians found a broken internal baffle inside the No. 1 exhaust silencer.Thereafter, the shop inspected the silencer every 100 hours and the baffle was found to be completely broken at the next inspection. The problem may have been the result of excessive priming having caused a backfire during engine start.

Inspection Call
Extra Wing Loads

Extra 200 and 300 series aircraft have come under a new airworthiness directive that requires operators to inspect the fuel selector valve for leakage and the wing for structural damage.Although critics of the AD said it should apply only to those aircraft with long-range tanks, the agency disagreed and made it applicable to all models. The weight of the fuel in the wings, when combined with the airplanes ability to generate extremely high G-loading, led Extra to conclude there was a danger of damage to the structure of the wings.


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