by Alan Sanderson
All repair stations are not alike. Customers have brought balloon systems into our repair station for annual inspections after they were serviced in another shop. The differences in condition were often interesting, and sometimes frightening.
Each balloon manufacturer publishes a document that may be called Maintenance Manual, Manual for Continued Airworthiness, or something similar. This manual must be available in any repair station that is certified to work on a specific brand of balloon. Most of the more recent manuals also contain a checklist for use during an annual or 100 hour inspection. This checklist lists components to be inspected, and the standards each component must meet. More detailed information is included in the maintenance manual section covering the component.
Envelope Condition
In our experience, most repair stations do a reasonable job inspecting envelopes. The manufacturers typically require a visual inspection of fabric, seams, load tapes, and suspension cables. Most require a fabric pull, or tensile tear test, to check for weakened threads in both the warp and fill directions. If a panel fails this test, adjacent panels and other panels of the same color must be tested. We have not seen any unexpected failures, so we believe the other shops are doing a reasonable job. One manufacturer requires a porosity test, and we have not had any surprises with envelope porosity.
Patches are another matter. Each manufacturer has specific requirements for legal patches, including seams, allowing old fabric to remain under a patch (overlay patches), and the distance from a seam or a load tape. Some manufacturers allow self-adhesive patches as a permanent repair. Others allow them only as a temporary repair until the edges are sewn down at the next annual inspection. We have seen some illegal patches installed too close to a seam, improperly stitched, or not properly oriented (the thread directions must line up). Other illegal patches have used unapproved fabric, such as nylon in a polyester balloon, or the reverse. If a repair station discovers an illegal repair, it will not return the aircraft to service until the repair is corrected. If the repair station returns the aircraft without correcting the improper work, a logbook entry will declare it unairworthy.
Suspension Cables
Steel suspension cables lose strength if they have been burned or kinked, and must be replaced. Kevlar cables are covered with a polyester or nylon cover that can melt without damage to the Kevlar fibers. If the covering is damaged, and the Kevlar remains yellow and flexible, it can be repaired.
We received one system with melted cable covering that had been covered with heat shrink tubing, normally an acceptable repair. The cable felt stiff, so we removed the tubing. The melted covering had not been removed, leaving sharp melted crystals to cut through the Kevlar fibers.
Burner
Required burner maintenance varies by manufacturer, including visual and operational checks of the burner's major components. The blast valve is checked or serviced, the coils are inspected for cracks or damage. Valves are checked for smooth operation. The pilot lights are checked for proper flame characteristics. The fuel fittings are checked for leaks, and an operational test is performed. Operation of the aspirator (slurper tube) is verified, and fuel jets are checked for tightness and proper aiming.
Most burner problems result from normal wear and tear. We have received burners that lacked lubrication in the blast valve, and burners with pilot light propane jets so clogged that the flames could be easily blown out. Some of these problems were the result of neglect by the previous repair station. This problem should have been noticed by the pilot, and it was serious enough that it should have been found during the previous annual inspection.
Fuel System
One pilot brought in a system with a complaint of a leak around the stem of the cylinder service valve. He had taken the cylinder out of service. We disassembled the valve to find the stem seal "O"-ring covered with brass powder. The formerly Teflon-coated valve stem had almost no remaining threads. This valve had been developing its condition for some time, possibly from someone with a gorilla grip.
This particular valve design relies on the "O"-ring as the primary stem seal, and it has a secondary stem seal that can be used by opening the valve completely, or "backstopping" it. With the missing threads and the damaged "O"-ring, the pilot could have been in the air with a leaking valve that he could neither open against the stop, nor close to stop the propane flow. Fortunately the pilot detected a problem, and averted a disaster.
We inspected, cleaned, and lubricated all the service valves on that system. We found and replaced two more valves, and determined that the remaining valves were in good condition.
All valves in your fuel system should operate smoothly. If any valve drags, grinds, or has a gritty feel, have it inspected by your repair station or a full service propane dealer. If you have any doubt about the condition of any part of the fuel system, have it checked out before your next flight.
Fuel Cylinders
We encourage our customers to bring the system in with as little fuel as possible so we can inspect the cylinders. Some repair stations open cylinders only on request. We have found enough potential problems that we recommend an internal inspection annually. On one system, some of the fuel level gauges float assemblies had almost separated from the indicator. The indicator needle is a small compass, and the float turns a small magnet under the indicator needle. With the float assembly in the bottom of the cylinder, the fuel level indicators would point to magnetic north.
We frequently find dead flies and metal shavings inside fuel cylinders. Either item can become lodged in a service valve, a blast valve, a burner jet, or a pilot light regulator. We have found them in all of these places, resulting in a cylinder valve that would not shut off, a failed pilot light, or a blast valve that would not turn off completely.
Your Repair Station
Find out what your repair station does during an annual inspection. The inspector should welcome your questions and your help during the inspection. If there is any part of the system that is not covered to your satisfaction, find out why.
Ask other pilots about their experience with different repair stations. Most pilots are generous with their opinions.
Call the manufacturer. They know who does a lot of work on their equipment, and who has attended their training programs. They may not recommend a shop to avoid, but they can suggest shops you should consider.
You should not be going to the repair station just to get a stamp in the aircraft logyou should know that you are launching a safe and airworthy aircraft after your next inflation.
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