Chained Lightning

Metal fuel cap retaining chains pose danger of lightning-induced damage


The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts. Click here to view “Airworthiness Directives.”


Some current production aircraft and replacement fuel cap kits include metal retention chains. These aircraft, often not originally equipped with any type of fuel cap retention device, were not certificated to meet the lightning protection rules that are currently required. The current required lightning certification criteria, explained in FAA Advisory Circular 20-53A, recognizes the contribution of metal chains to the potential of fuel tank explosions induced by lightning strikes.Metal fuel cap retention chains should be replaced by nonmetallic, fuel-resistant straps. These nonmetallic fuel cap retainers provide greater lightning protection, especially for float-equipped and high-wing aircraft. Metallic cap retainers installed by the manufacturer may be removed and replaced by a nonmetallic retainer. This action constitutes a minor alteration.

Beech C-12C (B200) King Air
Engine Starting Problem

The flight crew reported starting difficulties with the left engine.While troubleshooting this problem, a maintenance technician noticed an anomaly in the paint coating adjacent to a weld on the fuel flow divider case boss. Upon applying slight side pressure to the boss a crack opened. The technician determined the crack caused the starting problem and he replaced the fuel flow divider.Part time since overhaul – 382 hours.

Beech V35B Bonanza
Severe Corrosion

This aircraft is equipped with an alcohol wing anti-icing system installed in accordance with STC SA2239CE.During an annual inspection, the technician discovered corrosion on the lower exterior surface of the right wing skin. This area is located beneath the alcohol anti-ice tank. The technician removed the wing skin, revealing excessive corrosion on all the surrounding structural members. The technician determined the cause of this damage was moisture trapped in the alcohol tanks insulating liner. The corrosion required replacing the wing skin and installing an aluminum tank liner.

Beech A36 Bonanza
Aileron Tube Chafing

During an annual inspection, the technician discovered severe chafing damage on the right aileron push-pull tube.The aileron push-pull tube had worn almost completely through the wall thickness due to chafing and vibration at the point where it contacted the aft wing spar. This tube connects the aileron to the bell crank and failure could have catastrophic results. The technician reported this was the second similar defect he has found on like aircraft.Part total time – 386 hours.

Beech 58 Baron
Nose Landing Gear Defect

The flight crew reported a nose landing gear defect.Maintenance personnel found the right arm of the nose gear drag aft brace broken just forward of the retraction rod attachment. The drag brace was a steel tube that had suffered severe internal corrosion. The external surface of the tube gave no clue to the severity of the internal corrosion. Part total time – 5,024 hours.

Cessna 172P
Vacuum Hose Failure

The pilot experienced complete vacuum system failure of both the normal and standby systems.Maintenance personnel discovered the hoses to the altimeter and directional gyro were brittle. Bending the hoses resulted in the hose completely breaking.Inspection of three other like aircraft in this operators fleet revealed the same problems. Another report indicated that the inside red liner of the hose was crumbling from age and particles were found in the instrument screens. This report indicates that three of 12 aircraft (Cessna 172P and Cessna 182R) inspected had the same problems. A third report indicates the hose failure occurred on both the inside and outside of the hose.Part total time – 2,450 to 2,680 hours.

Cessna 172R
Fuel System Leak

During an avionics equipment installation, the technician noticed fuel stains around a B nut.The B nut (P/N AN924-6D) connects the fuel line from the left tank to the fuel selector valve. Apparently, the manufacturer applied insufficient torque to the nut when installing the line. After applying correct torque, the leak stopped. Part total time – 20 hours.

Cessna 182G
Wing Lift Strut Fitting Failure

During an annual inspection, the technician discovered a cracked lower lift strut fitting.This finding prompted the inspection of other like aircraft, where technicians found three additional cracked fittings. The cracks were all in the same location, with the crack radiating out of the lowest rivet hole. The cracks are located under the floor boards near the seam of the belly skin and are hard to see. Replacing the fitting requires extensive sheet metal work.

Cessna 210D
Mixture Control Failure

The engine mixture cable failed in flight, causing a forced landing and destruction of the aircraft. Technicians determined the cable was rigged improperly on installation. The mixture cable had been replaced less than 1 year prior to the accident, and had only 99 flight hours since installation. AD 85-03-01 and service letter SE 69-16 pertain to this subject, but are only one-time compliance items. Part total time – 99 hours.

Piper PA-18-150 Super Cub
Wing Strut Corrosion

During an annual inspection, the technician discovered severe corrosion on a wing lift strut fitting.Corrosion from the left wing upper lift strut attachment fitting had migrated to the front wing spar. The corrosion was located under the wing leading edge covering. This area is not accessible for inspection without cutting an inspection hole. This area may have been neglected because of the lack of accessibility for inspection. In this case, the structural integrity of the lift strut fitting, as well as the wing spar, was compromised. AD 99-01-05 deals with this subject.Aircraft total time – 12,934 hours.

Piper PA 31-310 Navajo
Defective Main Landing Gear Axle

While walking on the airport parking ramp, a maintenance technician noticed the left main landing gear wheel tilted in at an abnormal angle.A closer inspection revealed the brake disk contacted the gear fork. After removing the wheel assembly, the technician discovered the axle was cracked around approximately one-half of the lower circumference. It appeared that the crack started at the bottom of the axle in the boss and bearing seam area, and spread upward in both directions. The submitter speculated the defect was caused by stress corrosion associated with age. Part total time – 13,825 hours.

Piper PA 44-180 Seminole
Aileron Travel Interference

During pre-flight, the pilot discovered interference with the aileron travel.Maintenance personnel investigated and found the interference resulted from rivets installed in the left aileron striking the upper wing skin. The technician previously complied with AD 81-10-04 and Piper service bulletin 702 on this aircraft. SB 702 requires the installation of a Piper rework kit that apparently was not installed properly, allowing the rivets to cause interference.

Robinson KR-2
ELT Failure

A fatal aircraft accident occurred in a remote area, and search efforts were hampered when the emergency locator transmitter failed. When investigators recovered the Emergency Beacon EBC-102A ELT, they found the actuating switch arm locked in the off position. A shipping screw, installed by the manufacturer when the ELT was new, had not been removed when the unit was installed. Evidently, this defect was not discovered during the last annual inspection.Aircraft total time – 141 hours.

Turbine fuel contamination
There have been several recent turbine-engine accidents attributed to contaminated fuel.

Every aircraft fuel system and engine have limits to the amount of water and solid contamination they can tolerate. Fuel samples from the accident aircraft were well above the allowable contaminant levels permitted for commercial refueling sources.

The fuel contamination problems seem to originate from refueling sources and sites that are not monitored. Many aircraft manufacturers offer secondary fuel filters as an optional kit, which can provide additional protection from the effects of contamination likely to be introduced by home-made refueling methods.

Off-airport or remote aircraft refueling operations, including aerial application, aerial survey, and national park site-seeing are at risk. Those operators are strongly cautioned to utilize all possible means to preclude the introduction of contaminated fuel.


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