Annual Inspections

RC Jets

By Jim Hiller | [email protected]

As seen in the March 2023 issue of Model Aviation.

HAVE YOU PERFORMED an annual inspection yet on your frequently flown models? It’s amazing the things you will find when you do. Our complex models have many points for failure, and it’s best to find problems on the ground instead of in the air.

Sergio Testa (L) is shown with his impressive IA-63 Pampa that he flies in an incredibly smooth, scalelike manner. Sergio hails from Argentina, yet he travels to the US to attend numerous jet modeling events.

When I finished last season, my older Xtreme ARF Vixen had a surprising issue. I had to pull out the one-piece stabilizer and found a thin coat of smoke oil lying on top of it. This wasn’t a big deal until I examined the insulation on the elevator servo wires. It was hard and brittle. The insulation actually broke as I flexed the servo wires to unplug the servo connectors. That ended my day of flying.

I was frequently using the smoke system on this model when the issue came forward. In this case, the vent system on the smoke tanks, combined with hard aerobatics, resulted in smoke oil being pushed out through the smoke tank vent, which is flush-mounted on the bottom of the Vixen. The oil coated the outside bottom of the model and was getting sucked into the fuselage at the split line where the fuselage separates for maintenance, slightly aft of the wing’s trailing edge. The inside bottom of the fuselage had a thin coat of smoke oil from the split line aft to the tailpipe opening.

The repair was complicated by the aft part of the fuselage being tricky to remove. The bolts are quite difficult to reach, so I seldom separate this fuselage into two halves. This time, though, I replaced the hardened insulated servo wires with new ones made from PowerBox’s premium servo leads, which should be more tolerant of chemical damage.

The next item was to address the root cause—the smoke vent system—and why it overflowed during aerobatic flying. The smoke tanks are located under the inlets on the bottom of the aircraft, and the vent line extends immediately from the top of the last tank to the belly-mounted, flush overflow vent.

Two things were against me with this simple setup. The air blowing across the flush vent line creates a vacuum, pulling from the smoke tank. That, in combination with the line filling with smoke oil during inverted flight, created the problem. Roll right-side-up and the oil in the vent line pulls right out. The quick fix I made was to loop the smoke vent tubing up over the inlets and back down to the vent line. This long, vertical path makes it more difficult for smoke oil to vent out during aerobatics.

Another area to always keep a watchful eye on is the landing gear. It tends to be hidden on the bottom of the airplane and really doesn’t get the attention it deserves. Taxiing, taking off, and landing vibrate things loose on the landing gear, so inspect it regularly. Look at the gear struts when disassembling at the end of a flying day— you never know what you will find. The C-clips on the landing gear struts might pop off, leaving a scissor-link pivot pin to work its way out. A quick visual inspection and you can find it before it ends a day of flying.

One strange occurrence that I regularly found on my DerJet Vampire was loose nose-gear retract mounting bolts. I had to retighten them once or twice a year. The nose-gear retract unit was mounted on 1/4-inch thick G-10 with the mounting bolts threaded into the plate. It’s a nice, rigid system, but during normal use, the mounting bolts tended to work loose for unknown reasons.

The E-flite 90mm Viper is proving to be a popular model for turbine conversions. A 30- to 45-newton turbine makes this a wonderful flying machine. Conversion kits are available from Paul Applebaum, or you can go at it alone with a custom tailpipe and standard fuel tanks.

My annual inspections include a close-up of the turbine bay. Be on the lookout for loose screws. I once even found the turbine mounting screws to be loose and took care of that immediately. Look for loose wires or air lines that are no longer held clear of hot areas, such as the turbine case or tailpipe, and, at risk of being sucked up into the inlet of the turbine. That can be an expensive occurrence because the compressor blades are easily damaged.

Another area to watch on open installs is the area between the turbine’s exhaust and the bell mouth. This is not a cool area, so secure items such as servo leads, smoke lines, or air lines so that they remain clear of it.

IA-63 Pampa

We fly a variety of Scale airplanes, and one that has caught my eye throughout the years is an IA-63 Pampa flown by Sergio Testa. Let me elaborate. It’s extremely well flown in a very smooth, precise, scalelike manner—on every flight.

Sergio is a truly dedicated international jet modeler who hails from Argentina, yet he travels to enjoy the company of fellow enthusiasts, attending events in the US. At Jets Over Kentucky 2022, I finally had a chance to meet with Sergio, and he was happy to fill me in on the details of his Scale IA-63 Pampa jet.

This model is produced in Argentina in both 1/5 scale and the larger 1/3 scale that Sergio flies. It’s a unique Scale model that is seldom seen, yet it appears to be a very straightforward, nice-flying airplane.

Check out Sergio’s website, Sergio Testa Jets Design, for an international look at our hobby. The link is listed in "Sources." There you will find that he is not only an avid flier but also markets some unique jet kits, including the IA-63 Pampa.