Squawk Box: 03/04


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


Sparring Over Spars
The FAA has reopened public input for a pair of proposed airworthiness directives aimed at preventing wing spar failure in Cessna 401, 402, 411 and 414 series airplanes.The proposed ADs would require repetitive inspections on the wing spar caps and to incorporate a spar strap modification on each wing spar of certain airplanes. Owners groups are concerned that the cost of the required repairs will be economically unviable.The FAA plans to hear public comments in early March to debate the issue and to explore alternative solutions.The FAA cites a service history of cracks in the wing spars dating back 25 years, with the most recent causing a fatal accident in 1999. Stress analysis shows the wing spars could fail if not modified. One major concern is that a crack can grow to a size that threatens failure and still be undetectable by current nondestructive testing methods because of the design of the parts.

Aviat A-1 and A-1B
Fuel Vent System

An operator encountered two occasions when the engine stopped due to a blocked fuel vent.In the first occurrence, the engine on an Aviat A-1 was undergoing a ground run check when it stopped. The technician found that an ice plug had formed on both overboard vents when the airplane was exposed to freezing rain.The same operator found that an Aviat A-1B suffered a loss of engine power after takeoff despite the pilots check for vent tube ice before departure. The pilot made a dead stick landing and opened the fuel tank caps, at which time he heard the sound of inrushing air. That airplane had also been exposed to freezing rain prior to flight.

Cessna 150F
Corroded Wing Tank Skins

During an inspection, the technician noted the lower wing tank skins were corroded through in the strainer assembly sump. Corrosion was also noted in other areas of the lower tank surface.The corrosion was consistent with standing water. The strainer assembly is the low point in the tank and there are no provisions for draining it. Both the left and right tanks were affected. The airplane had been inactive for a year.

Cessna 172M Skyhawk
Broken Door Hinge Pin

During an annual inspection, the technician found the top pilot door hinge pin had been abraded. Only about half of the pin remained and only a small portion was holding the hinge together. The technician said he had found a similar problem on many other like aircraft. Loss of the pin could result in the door departing the aircraft.

Cessna 172N Skyhawk
Burned Voltage Regulator

The pilot complained of smoke in the cockpit that cleared when the master switch was shut off.Inspection revealed there had been a fire inside of the voltage regulator. Apparently the internal overvoltage relay failed, resulting in an overvoltage condition throughout the electrical system. The landing lights, fuel gauge, beacon and all radios were damaged.

Cessna 172RG Cutlass
Pitot Tube Melted

During a routine inspection, the internal pitot tubing was found melted near the heated external tube. The wiring for the pitot tube heating element was apparently misrouted, allowing heat from the element to melt the plastic tubing inside the wing. The pilot had not complained of a malfunctioning pitot system. Aircraft total time was nearly 12,000 hours.

Cessna 206H Stationair
Aileron Control Failure

Immediately after takeoff, the pilot noticed minimal reaction from the aileron control inputs. He was able to land the aircraft safely.The technician discovered the left aileron was disconnected from the control rod. The control rod had broken in the threaded area just forward of the aileron control rod-end jamnut. The break may have been the result of lack of lubrication.

Cessna T210N Centurion
Cracked Wing Spar

During an inspection, the technician found the wing spar web was cracked at the attachment point for a fuel pump associated with the Flint auxiliary wing tip system.Vibration associated with the reciprocating fuel pump apparently caused the spar web to flex and crack at the outside radius of the attachment hardware.

Cirrus SR20
Failed Elevator Cartridge

While on approach, the pilot disengaged the autopilot and found the elevator control to be stuck in a fixed position. The pitch trim control was operating normally. After several attempts to free the control without success, the pilot jerked the control back and it freed enough to provide sufficient up elevator control to make a successful landing. The elevator was initially hard to move in either direction, but as the airplane warmed up it could be moved to full travel in either direction. However, the pitch trim cartridge was making excessive noise, so it was replaced.

Commander 114B
Frozen Gear Actuator

During an annual inspection, the technician cycled the gear and heard a squeal, followed by a pop, from the right main landing gear.Further investigation found that the landing gear hydraulic actuator attach bearing was frozen, causing the housing around the bearing to break and pull apart during the retraction cycle. The left side bearing showed no malfunction, but inspection of a like aircraft found the problem on both sides.

Lancair LC40 Columbia
Flawed Aileron Link

While rigging the aircraft using specs from the manufacturers maintenance manual, the aileron final control threads were destroyed while the technician was trying to reach the specified torque range.The manufacturer supplied different torque specs and a new link was ordered. During the installation, the threads on the link were destroyed again. The torque wrench was checked and found to be correctly calibrated. Further efforts to contact the manufacturer were unsuccessful.

Maule MT-7-235 Rocket
Separated Alternate Air

During an annual inspection, the technician discovered the alternate air intake duct was broken off the left exhaust muffler at the weld. The duct and hose were chafing against the engine mount tubular structure.

Mooney M20J
Worn Gear Actuator Shaft

After a landing gear repair, the pilot complained the actuator was not showing the gear was down and locked.When the actuator was disassembled, the gear was found so worn it would not engage the pinion. The manufacturer had no gear kits available. The worn gear appeared to be a substandard part that was not hard enough.

Piper PA-24-260 Comanche
Cracked Rudder Bellcrank

During an annual inspection, the technician found a crack in the bellcrank bolt hole. On closer inspection, he discovered that all four bolt holes displayed cracks in various stages of progression.The cracks began at the end of the part and proceeded towards the bolt holes. Only one crack proceeded all the way to the bolt hole. The largest crack could be seen clearly, but the remaining three required magnification. A dye-penetrant inspection produced the clearest result. After the initial cleaning, the technician found a crack at one of the holes for the rudder cable attachment hardware. The fifth crack progressed all the way from the hole to the outer edge.The submitter stated that the aircraft has speed modification and is not restricted to 203 miles per hour.

Piper PA-28R-201 Arrow
Broken Nose Gear Actuator

The pilot reported a thumping noise when the nose gear retracted, after which the nose gear extended and locked. The pilot extended the main gear and landed normally.Inspection found the nose gear actuator rod end had sheared at the end of the threads on the bearing end. No other damage was noted.

Piper PA-32-260
Detached Muffler

The exhaust tube on the muffler detached from the muffler during flight and departed the aircraft.The manufacturer recommends replacing the muffler at 1,000-hour intervals, but this muffler had been in service for nearly 1,800 hours.

Piper PA-32R-300T Lance II
Damaged Vac Pump

The overboard air line of the vacuum pump backed out of the pump, perhaps due to damaged threads.When it fell, it apparently became caught in the down lock mechanism of the nose gear. On landing, the nose gear would not fully extend, resulting in a nose gear collapse on the ground.


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