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The Ground Handling Blog

Mototok's blog for Hangar Professionals

Written by Mototok on June 21, 2019 // 10:34 AM

Impacts of Extreme Environmental Conditions on Aircraft & GSE

aircraft cold
Line maintenance on aircraft is full of extremes; very few aircraft or technicians are likely to work in ideal, temperate climates all of the time. Some locations are afflicted with high heat and humidity, or a combination with grit and sand. Others enjoy mild summers but brutal cold. Other climates yet draw the shortest straws and are very hot and very cold. We know how it makes our bodies feel, but what are the true mechanical effects on machines? Let’s take a look at how extreme environmental conditions affect flight and ground operations.

Effects of Heat on GSE and aircraft

A lot of the busiest hub airports in the world are located in hot, humid, or hot and humid environments. In fact, the busiest airport in the world, Hartsfield-Jackson Atlanta International (KATL), is located in the extremely hot and very humid Atlanta, Georgia. Dubai International (#3 busiest) is even hotter, and Dallas-Fort Worth (#15 busiest) is subject to all sorts of extremes, the least of which is high heat and humidity. So obviously heat alone is not going to shut flight operations down, but it certainly does pose challenges to operations.

Environmentally, heat has a powerfully negative effect on machinery. Heat draws the moisture out of soil, creating dust and loose dirt, which permeates equipment. Heat also draws moisture from seals and gaskets, allowing the aforementioned dust and dirt to enter equipment systems.

For the sake of aircraft systems, the hydraulic systems and components are particularly susceptible to damage. Seals in the landing gear shrink and “roll”, causing hydraulic fluid to leak along the cylinder. Then, loose dust and dirt stick to the fluid, which then is pulled up into the seals causing further damage.

Heat causes components to expand, which is particularly detrimental to hydraulic junctions and swages. Heat when swages and compressed hydraulic fitting and junctions expand, they begin to leak and they may be weakened for future use, and tend to fail in catastrophic manners.

Your ground support equipment is not impervious to heat, not by a long shot. All equipment is different and reacts in different ways. Non-powered age, mostly stands and lifts, are not all that bothered by the temperate itself but are bothered extensively by the byproducts of high heats, namely dust and dirt, or just grit in general.

Powered GSE are a different story. The myriad ways high heat affects powered GSE include damage to electronics, and damage to many different areas of the power plant. High heat breaks down lubricants faster, and contributes to boiling coolant and overheating engines. A gas or diesel powered aircraft tug is highly susceptible to these environmental extremes since they never go fast enough to have strong airflow over the radiator; idling engines in extreme heat struggle to keep within safe operating ranges. Electric tugs are a good solution to this problem, but they do need to be a sealed unit to mitigate the effects of grit and grime.

How your equipment can survive high humidity environments

High humidity environments are not necessarily extremely hot as well, but a whole lot of them are. Heat is tough on engine, hydraulic systems (including automatic transmissions), but highly humid environments wreak absolute havoc on machines. The ill effects are particularly bad if it happens to be near saltwater, where the humid air contains the most pervasive, corrosive salt known to mankind. Okay, that might be a stretch but it is not an exaggeration to state that saltwater air makes up about the very worst environment for aircraft and equipment.

The structural detrimental effect of high humidity is oxidation of metals, especially pervasive when salt is in the air acting as a catalyst. “But aluminum doesn’t rust”. Technically, corrosion is a chemical or electrochemical reaction between the material and its environment. According to the FAAs Aviation Maintenance Technician Handbook-Volume 1, interior corrosion on an aircraft is caused by humidity and salt in the air.

Rivet stems, which often employ steel cores, are a hotbed of corrosion in aircraft structures. They have a tendency to oxidize which can actually cause dissimilar metals to oxidize along with it.

Since most of an aircraft’s actual airframe structure is aluminum or aluminum alloy, the effects of high humidity are generally limited to certain areas and components. However, your GSE fleet is a very different story. GSE structures are built almost exclusively from mild steel, generally depending on paint and regular wash cycles to keep the grit, grime, and effects of extended moisture away. Frankly, these methods do work pretty well if the operator is diligent in the employment. The same holds true for automobiles owned and operated in extreme cold and snowy locations where roads are salted; good paint and frequent washing to remove deposits of salt and grime do a marvelous job protecting mild steel if you do it.

If you do not keep machinery sealed with industrial grade paints, and do not run it through the wash rack routinely, it is going to rust. Also, there is this issue of treated materials. Coated and electroplated bolts and associated hardware hold up to the rigors of salty and humid environments with excellent results, but they can actually be a catalyst of further corrosion when salty, moist air is locked between threads of the treated fastener and the female threads of mild steel which must remain unpainted. This is when it is imperative that a high quality lubricant is used prior to fasting items which will treat the unpolluted metal and keep water from entering at all. General purpose grease is a good place to start, so long as it is not being used in a high-heat application.

Extreme Cold and what GSE can survive it

There is little conclusive evidence that extreme cold environments are enjoyed by a single living organism; extreme heat and high humidity generally indicate the presence of an equatorial location, along with a body of saltwater; i.e. an ocean. This is, of course, a little joshing at the frosty climates of the world. But the negative impact of extreme cold is no joke; it breaks machinery left and right.

High heat expands seals and gaskets, and swells rubber hoses and fittings. Conversely, deep cold temperatures contract rubber and other gasket materials (cork, paper, etc.), shrinking them and causing leaks. But not only do they contract, the cold then makes them brittle. Seals, gaskets, hoses, fitting, rubber clamps, and anything else using rubber to seal will fail under prolonged exposure. Fuel bladders in aircraft, made exclusively from rubber, are not impervious to the effects of extended cold; they can contract and crack as well, causing leaks just about anywhere in the wings, fuselage, and etcetera. Fuel will then leak from rivets, bulkheads, wherever; it can be a real mess when bladders start to leak.

Let us not forget how frigid temperatures impact engines themselves, speaking mostly to GSE. Internal combustion engines, most notably diesels, are not at their best in sub-zero temperatures, and require extra care and attention. If the antifreeze/coolant is not rated for the low temperature on location, it can and will actually freeze. When it freezes, it expands, and when it expands, it pushes outward on the surface containing it. In the case of an engine, that is the radiator and water jackets in the engine block. It is not uncommon for frozen antifreeze in water jackets to expand and crack the engine block, a very costly repair (or mistake).

Cold weather might well be where the electric tug shines brightest; it is a sealed unit which is functionally impervious to external environmental influences. It has no antifreeze to freeze, no startup/warmup timetable to achieve operating temperature prior to use; no wasteful burning of fuel staying warm between uses. For the sake of personnel, the remote control tug is a wonderful invention where only one or two technicians need be in the poor elements rather than an entire team. Or moreover, if the team must be in the elements, they can be at work on more technical projects than aircraft movements.

Conclusion to extreme environmental conditions and their impact on aircraft and GSE

This is not an all-inclusive itemized list of all the negative effects of extreme environments. It is, instead, a rundown on the most impactful ways which extreme heat, cold, and humidity can damage your very costly investments. Modern manufacturing and engineering have created means to mitigate these effects considerably, particularly in aircraft movements through the implementation of a sealed, electric tug. A sealed unit offers so many advantages over old school, internal combustion machinery which are so sensitive to environmental conditions and changes. Take the plunge, modernize your GSE and start with a high quality tug which is practically impervious to Mother Nature!

Are you looking for resistant aircraft tugs that can withstand the harshest conditions? Get in touch with us today and request a free consultation on our electric, remote controlled tugs!

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