SMOKE SYSTEM

Thick white smoke billowing from an airplane in flight really Looks Great ...    Unless, of course, your plane does not have an on-board Smoke System!

I’ve put together a few smokers that have actually worked, so hopefully, I can pass on some useful tips for installation and operation.

First, answer this: Is there enough room inside your airplane for these added smoke system components?

Then consider, what once was your stable and predictable airplane will suddenly behave “differently” with the added system weight, possibly even downright unpleasant to fly!

So if your plane is a “60” size or smaller, a 2 or 3 pound weight gain (which includes a full tank of smoke oil), will probably be too much.   I’ve owned a few "heavyweights" in the past, and I couldn’t sell or give them away quickly enough!

In addition, the Center of Gravity will likely change with the new components.   Although, a “shifty” CG is not always bad:   the oil tank in my CAP is several inches behind the wing tube carry-through so that with a full tank the CG is at the Aft limit for certain maneuvers, then with an empty oil tank the CG has shifted forward for a more stable approach and landing.

Ok, so you’ve decided to make your "Slaschurfingerren Spittinflygen" smoke on purpose.

The next step is parts procurement:   Smoke Oil, Smoke Pump, Tygon and Neoprene tubing, Tubing clamps, One-way Valve, Smoke Muffler or your (attached) muffler drilled and tapped for a "Pressure Fitting," a Fuel Tank with an optional tank stopper for OIL -- Do Not use the stopper and silicon tubing supplied with the tank, these parts are for glow fuel use only. A standard Servo linked to a micro-switch is required for on/off control of the pump, although an optional “Programmable” pump or an Electronic Switch can eliminate the need for a micro-switch and servo.

The Pump:

There are two types of on-board oil pumps to use: The most common is an Electric motor-driven unit, and the other is a Mechanical pump that uses engine crankcase pressure for pump operation.

The mechanical pump is simpler and less costly -- it would seem to be the right choice, however I recommend the electric pump because it performs better. Engine performance can be adversely affected when using a mechanical pump since it has to rob some of the engine's case pressure for pump operation.

Either pump is a “guzzler!” A 24 oz. tank full of smoke oil will be emptied in less than 2 minutes if you allow the pump to run continuously! Of course you don't need, and you wouldn't want to have the smoke on continuously, so transmitter controlled on/off “switching” of the pump is needed (mentioned above).

The Switching:

If your transmitter has mixing capability, a Programmable electric smoke pump with built-in circuitry and battery pack is a preferred option.    This pump unit “thinks” it is a servo, therefore you can program your transmitter to slave the pump motor rpm with the throttle position -- it also has wiring with a connector that can be plugged directly into a receiver spare channel. I have my CAP’s smoke system setup for No oil flow below ¼ throttle, then above that point the pump begins an increasing flow as the throttle is advanced. Manual on/off control of the pump is still needed, especially if a problem occurs.

More Stuff:

If your electric smoke pump does not have it’s own battery pack, I recommend using a separate pack rather than tapping into the receiver’s battery pack. This will help keep electrical noise and voltage spikes out of the on-board radio equipment - and - if the pump motor decides to seize or short circuit, the radio components will be unaffected, (* see precaution note at end).

If you install an oil pump that is not programmable, a restrictor device is usually needed for 'tweaking' the pump’s flow rate. Unrestricted oil pump output will be too high and will only cause an unburned residual mess! This overabundance can even stop your engine!

A one-way check valve should be installed in the oil line forward of the firewall within about 3 or 4 inches of the muffler. From the check valve to the muffler, use only neoprene tubing since it is heat resistant.

From time to time inspect all the plumbing, especially tubing and fittings behind the firewall. The neoprene tubing attached to the muffler will deteriorate from heat and vibration over time. As a precaution, I like to replace the neoprene after about ten flights regardless of how it looks; 4 inches of tubing is not expensive.

The Smoke Oil:

Smoke oil will cost about the same as glow fuel, although it’s not usually stocked at all hobby shops.

I know what you’re thinking: "I don’t want to pay for special-made smoke oil, I’ve heard the guys talk about using some other 'oil' such as transmission fluid, diesel fuel, or prune juice mixed with Old Spice," just to mention a few.

I like the “Super Dry” Aviation Smoke Oil, (the pro’s use this at the air shows).   Fox manufacturing makes a special smoke oil -- I plan to try their brew very soon.

Now trust me on this one: Don’t Mess with a creative concoction, pay a few bucks more for the good stuff.

Some Important Points:

• Glow engines do not generate smoke as well as Gas burners, because of lower exhaust gas temperature.



• Mount the Electric Pump and it’s battery pack as far away from any radio equipment as the center of gravity and space will allow.



• A switch controlling servo (for the electric pump), that is plugged into the receiver is of course, part of the on-board radio “Loop.” Therefore, this servo should not be mounted close or attached to any component of the smoke system. I.e.: Do not use a metal rod to link the servo to the pump on/off switch.



• Mount the smoke pump slightly lower and as close as possible to the oil tank. A short suction line to the pump will help insure a positive oil flow and quick priming.



• Try to mount the oil tank at or close to the airplane’s CG, (a good starting point).



• Use tubing clamps especially on plumbing aft of the firewall, and double-clamping on the pressure line from the smoke pump. If you use nylon ties for clamping, do not over tighten -- they will “pinch” the tubing and possibly cause a leak. In addition, when double-clamping with nylon ties, don’t line up the tie “tighteners” -- secure them so that tighteners “oppose” each other when close together.



• Before flying your airplane with the new smoke system, perform a radio range check while you are testing the smoke components with engine running.



• If during flight you switch smoke on and nothing -- no smoke! Switch Smoke OFF Immediately! Do Not switch smoke on again for some in-flight troubleshooting, until you land your plane and investigate the cause. It may be a minor problem (such as a detached wiring connector), but it could also be a detached oil pressure line inside the fuselage!



• Some optional smoke mufflers have built-in pre-heat coils which will help the oil “burn” more thoroughly.



• Fly The Airplane! Do Not let a new gadget or anything else divert your attention while you are Flying!

Let me know if I can help you with your new SMOKER, and ...

"Keep 'em Flying"
       Brad