Author: Jim Hiller
Edition: Model Aviation - 2011/02
Page Numbers: 122,123,125
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Radio Control Jets

Jim Hiller [[email protected]]

Teamed up for the Jet World Masters in Dayton, Ohio

Qualifications for the US team that will compete in the International Jet Model Committee (IJMC) Jet World Masters are complete. The members were selected in September at Litchfield, Illinois, two days before the Route 66 Jets event held at the Litchfield Municipal Airport.

Team members:

  • David Shulman
  • Scott Harris
  • Ron Snyder
  • Jason Bauer
  • Kim Foster
  • Lewis Patton

Alternates:

  • Bob Bush
  • Andy Andrews

They are a good mix of experienced jet modelers who have a lot of experience in World Masters, Top Gun, and Scale Masters competition. The team should do well.

The IJMC Jet World Masters will take place in Dayton, Ohio, at the National Museum of the US Air Force, July 24–August 6. This promises to be quite an event, with the best scale jet modelers from around the world attending. It might be the largest World Masters yet; 125 pilots are expected to represent 50 countries. For additional information, check out the Web site.

At the September qualifier I participated as a judge. It was a different role for me, but it allowed me to appreciate the variations in model types and setups for competition; those factors do make a difference. Using a gyro on all axes can greatly help pilots even out their flying, although that wasn’t a major issue on the calm flying day on which the qualifier was held. Throw in some wind and turbulence, and the advantages of gyros become obvious. If your competitors have them and you don’t, you lose.

My experiences with gyros have been limited to nose-gear steering quite a while ago, and lately on rudder only. My Bob Violett Models BobCat has a gyro on the rudder—what an improvement on a bumpy day! Wing rock, which is especially noticeable when flying past trees where the model gets bumped around a lot, is almost eliminated when I’m flying low. I wouldn’t consider even setting up a scale swept-wing model such as an F-86 Sabre without a gyro on the rudder to eliminate wing rock on landing and the tail waggle that takes place during high-speed flight on windy days. I believe in a gyro on the rudder that much. I guess it’s time to step up and experience a jet flying with three-axis gyro support—maybe on my old T-33. They might make flying on a windy day as smooth as it is on a calm evening. We’ll see.

Winter maintenance and prep

Winter is upon us here in the North, and it’s our time for maintenance and building. Last summer I flew my jets hard and often, and they performed flawlessly the whole time, thanks to good preparation. I put more than 140 flights on my old BobCat and 25-plus hours on the turbine, during which time the only maintenance I performed was brake and axle lubing. My T-33 didn't get quite as many flights, but it performed equally well. So how does one get these results?

My basic winter plan for the BobCat is simple. I start by pulling the turbine, which is a JetCentral Rabbit; 25 hours means that it's time for a trip back to the company for inspection. While it's there I'll have it updated with the kerosene-start option.

Take good care of your power plant; reliability is everything. This turbine ran all summer with no issues. All dead-stick landings were by choice—either deliberate shutdown or plain running out of fuel while flying with friends.

Dang you, Larry, Goose, and Frosty; I just noticed a pattern there! You all had bigger turbines and bigger fuel tanks. Wait until next year!

The only time I remove the tailbooms and the center wing section on the BobCat is when I pull the turbine, so now is my chance to inspect the internals. I start with the long servo extensions running the length of the tailbooms; there are plenty of opportunities for those to chafe against fiberglass along that run.

I pull on the hinges, check the linkages, and perform a solid visual inspection. I go over the stuff that is normally hidden, such as the turbine pump, solenoid valves, and smoke pump. Then I check wires and fuel tubing for issues.

The smoke pump got extremely weak toward the end of the flying season because it's getting old. Time for a new quality replacement.

While I'm in there I check out all of the fuel tanks. I pull them out and visually inspect them for issues, leaks, wear spots, and fuel-tubing condition. Then I put the tanks back in and check the plumbing carefully. I check all of the fittings on the pumps and lines for wear or cracks. I check the tank straps and the mounting bolts for tightness. I check the wing center section for signs of stress and repair, and I check the safety of the tailbooms and fin attachments.

I also remove the servos, clean them and the linkages, and blow out the bellcranks to make sure nothing is loose. Any servo with sluggish performance gets replaced. I also check the battery and its mounting. Battery connectors get replaced if there is any sign of wear.

Then I move forward to the pneumatics, again looking for chafing and loose items, and I review any operation issues I had during the flying season. I like to finish by putting a couple drops of air-tool oil in the retract air system and the brake system; I believe in lubrication. Be careful on your oil selection; many will damage the O-rings. Be sure to use only a proper air-tool oil. If in doubt, order it from a quality jet supplier; it knows our needs.

I basically pull out all servo extensions during this inspection, because I have to remove the boards on which my radio equipment is mounted to get to the nose gear, steering servo, brake servo and valve, and retract servo and valve. A good inspection is necessary every so often.

That silly little nut holding the retract valve in place came loose the first summer I had the BobCat, which resulted in its only gear-up landing. Fortunately the grass belly landing ended well; I never want to experience that again. The only way to inspect this is to remove the equipment board; the servo and retract valve are located under the main board.

Last I install new tires, clean and grease the axle bushings, apply lube on the brake O-rings, and then reassemble everything. I take great care to properly route all wires, air tubing, and fuel hoses, and secure them as required. If I take my time and do it right, I won't have to do it again until next winter. I should get more than 25 hours of flying.

After all that I finish off with a good preflight and taxi test. That way I know everything is working before the first flight of the season.

I can hardly stand that it's too cold to fly; once this BobCat is ready, I will be too. Let's plow the snow off of the runway and go fly!

Maverick turbine-conversion project

On the subject of shop work, the Maverick turbine-conversion project is finally flying. It's fun! This model has stepped up for the Wren MW-54 Mk III; it displays good speed, good vertical performance, and reasonable weight. This older-generation Wren has only 14 pounds of thrust, and the model weighs just more than 16 pounds empty—not a bad power-to-weight ratio.

I put time and effort into making the Maverick a reliable and durable sport jet. Some of that included exchanging the original landing gear system for slightly heavier retract units on the mains, upgrading to 7/16-inch-diameter Robart Robo Struts on the main gear, and installing an all-metal nose gear retract unit from Sierra Giant Scale, with one of its trailing link struts. I hate marginal landing gears.

The original Bob Violett Models wheels and brakes are still in place. The small 2-1/4-inch main tires and brakes are performing well at the model's heavy weight.

Total fuel onboard is just short of 2 liters; a comfortable six-minute flight is working out well with this jet/turbine setup. However, all didn't start well; four of the first six flights resulted in dead-stick landings. It turns out that I had reversed the main tank lines between the fill line and the clunk line. No harm was done, and now the system runs great. That main tank is hidden under the inlets, making access and visibility to it limited. Don't make my mistake; the turbine will shut down in flight.

I have only roughly five flights on the model, so it isn't dialed in yet. With the increased wing sweep compared with a stock Maverick, I am backing up the CG until I get a comfortable setup for landing approaches. With that, every flight gets mix adjustment on landing gear extension, flap extension, and general yaw and pitch for knife-edge flight, but this is a true-flying aircraft.

I plan to fly it some more during the next two months and dial it in, and then I should be able to share my experiences with you. Setting up a model for maximum flying enjoyment is an important process.

Until next time, let's get out and fly!

Sources

Contact

Jim Hiller 6090 Downs Rd. Champion, OH 44481 [email protected]

Transcribed from original scans by AI. Minor OCR errors may remain.