Tuesday, October 21, 2008
The Go/No-Go Decision In Winter
The rules change when the weather turns cold
|Winter Weather Protection |
What follows is a brief guide to some companies that have a proven track record for keeping aircraft safe from ice, snow and all cold-weather conditions.
Working on the principle that the best way to warm an airplane engine is in a heated hangar, AeroTherm has developed its Aircraft Engine Heater System to recirculate heat continuously into the engine compartment, warming up the engine, its cylinders and the oil evenly.
Bruce’s Custom Covers
For those of us who aren’t lucky enough to have access to a heated hangar, Bruce’s Custom Covers offers an extensive line of aircraft covers that are equipped with a microfiber lining to prevent an airplane’s paint and glass from scratching.
The TKS anti-ice system from CAV Aerospace is an ice-protection system that keeps ice at bay while maintaining aircraft performance in a frigid environment. An antifreeze solution is pumped from panels mounted on the horizontal and vertical stabilizers and leading edges of the wings.
Available for multiple engines, E-Z Heat’s Aircraft Engine Preheater System consists of a flexible synthetic pad that conforms to the contours of an oil pan and heats 12 quarts of oil from minus-40 degrees F to 60 degrees F in an hour (while using approximately 300 watts of electricity). The heaters are thermostatically controlled, so leaving them plugged in overnight means the airplane will be ready to go in the morning.
Kelly Aerospace’s thermoelectric Thermawing Air Foil Protection employs a laminate in which a flexible, expanded graphite foil acts as an electrical and heat-conducting layer. Thermawing Propeller Protection utilizes a standard prop timer with an Ice Shield prop heater.
Kennon Aircraft Covers
Kennon produces aircraft covers, engine covers, preheaters and cowl plugs to protect your aircraft from the elements in winter conditions. Shut down your engine, plug in the heaters, cover the engine with Kennon’s insulated engine cover and leave it plugged until you’re ready to fly again.
Reiff Preheat Systems
Reiff’s multipoint systems heat all of an airplane’s cylinders and don’t conflict with CHT sensors. The modular system allows aircraft owners to tailor a preheat system to meet their specific needs and budget.
In addition to flight jackets, compact engine preheaters, and DVDs and books about flying in inclement weather, Sporty’s offers its own carbon monoxide detector. This simple device can save your life—especially during the winter when you use your aircraft’s heater.
Tanis Aircraft Products
The Tanis product line is dedicated to preflight cold-weather operation. Its pioneering engine-preheater system directly heats the cylinder head and oil, thoroughly preheating an aircraft’s engine.
|The Importance Of Preheating In Cold-Weather Flying By Jeff Jorgenson |
|WEB EXCLUSIVE! |
Preheating is important for three reasons:
1. To protect the engine from damage during cold starts.
2. For easier starting.
3. To reach operating temperatures faster.
What type of damage occurs during cold-weather starts?
A cold-soaked aluminum case contracts more than the internal steel parts, causing excessive engine wear. The cold engine won’t have proper clearances between the case and the bushings, and will experience excessive wear or even a “spun bushing.” Air-cooled engines usually have a built-in cylinder choke to allow for expansion during operation; the cold affects the choke built into the cylinders. This is why it is important to preheat the entire engine and not just the oil.
Why is a cold engine hard to start?
The oil is thicker and the aluminum case constricting the crank and camshaft means the starter has to work harder. Spark-plug frosting may occur if air is introduced into the cylinder but it doesn’t fire right away. A cold engine is also subject to fuel streaming due to the cold temperatures, which is another reason to heat the cylinder heads. Just heating the oil or heating the cylinder base is typically not enough because the design of the cylinder, with aluminum cooling fins around a steel insert, inhibits proper heat transfer to the cylinder head.
In addition to the heads, warming the oil is essential for proper viscosity and proper lubrication of internal moving parts. It can take several minutes for oil to flow to the rocker covers in a cold-soaked engine. Imagine the amount of wear this alone might cause! Some propellers or other gearboxes, such as those on turbine engines and helicopters, are also dependent on warm oil for proper operation.
To properly preheat an engine, an internal electric preheater that addresses both the oil and the cylinder heads is best. “Flame throwers” use indirect heat so they’re far less energy efficient when comparing watts to BTUs; additionally, they’re not portable and may be dangerous to use. Many people don’t wait long enough to heat the entire engine, and only heat the heads so it starts easier, but the damage potential may still exist. In cold, windy areas, aircraft owners should use an insulated cowl cover for more efficient, uniform heating of the engine. A propeller cover is also advisable as the propeller is a large heat sink attached directly to the heart of the engine.
In addition to engine preheat, cabin and instrument preheat is also recommended in more extreme conditions to prevent bearing damage in gyros.
Preheaters don’t cause corrosion. Corrosion may occur over an extended period due to improper engine storage. This is because water exists in an internal combustion engine as a natural byproduct of combustion. In a warm engine, the oil coatings thin out over time, whether from the sun or from preheat. For this reason, leaving a preheater plugged in continuously isn’t advised unless the aircraft flies at least once weekly. Cycling a preheat on and off with a thermostat or timer isn’t advised due to the potential to “drive” water into undesirable areas. Plug them in at least four hours prior to flight or overnight for best results. A dehydrator product would work well in conjunction with the preheater for prolonged periods between flights.
For 35 years, Tanis Aircraft Products of Glenwood, Minn., has been providing cold-weather protection for aircraft.
The company offers summer and winter covers to protect aircraft from the elements and to complement preheat systems. Additionally, Tanis provides a dehydrator product for those airplanes that don’t at least once a week; for long-term storage, Tanis produces a “pickle” kit. To learn more, visit www.tanisaircraft.com or call (800) 443-2136. Jeff Jorgenson has accumulated hundreds of flight hours in experimental aircraft, Pipers, Cessnas and vintage taildraggers over the last dozen years, about half of which have been spent in the cold winters of the Midwest. He has worked in various weather, technology and aircraft industries.
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