When winter weather extremes hit you and your aircraft with frigid temps, snow, ice and wind, even preventive maintenance (PM) defensive measures may be too little, too late. That’s why it’s important to plan, prepare and train now for cold-weather operations using your aircraft-specific TMs.
For general cold weather information, check out Chapter 10 of TM 1-1500-204-23-1 (Jul 92, w/Ch 11, Dec 18), General Aircraft Maintenance. Because PM in sub-zero temperatures is critical to readiness and keeping aircraft flying, ensure your unit’s SOP for cold-weather operations is always current.
Aircraft, weapons systems, aviation ground support equipment (AGSE), aviation life support equipment (ALSE), and cold weather clothing all need preventive maintenance services (PMS) before the deep freeze hits.
When the deep freeze hits, moving aircraft inside the hangar for maintenance is best. If this is not practical, a shelter will work for equipment that’s out in the cold for extended periods of time.
In bitter cold, make sure you work in shifts and use the buddy system. Long periods outside can affect your body. Fingers are especially vulnerable to frostbite.
Wear gloves in cold
Break the maintenance up into small periods with one person working while another warms up in a hangar or shelter. If you use a temporary shelter made out of canvas or a parachute, use an authorized heater to warm it. However, make sure you follow all safety regulations to prevent a fire or carbon monoxide poisoning.
Wintry weather can affect fuel, seals, tires, batteries and airframes. Here are some valuable tips that will keep your aircraft operational when things turn really cold.
Tip 1: Cold Fuel
Ice can form in fuel lines from condensation. Limit that problem by keeping your aircraft topped off.
Even after topping off, there will be a gap between the top of the tank and the fuel. That’s where air condenses and water mixes with your fuel. So when you take a fuel sample each day, drain enough fuel to get rid of all the water. Always drain from the lowest point of the fuel cell. Water is heavier than fuel and will accumulate in the bottom of the fuel cell.
Refuel outside before moving inside
If refueling is done outside in freezing temperatures, always check the aircraft’s fuel level before moving it inside. Fuel expands in warmer temperatures, so taking a full aircraft inside could give you a fuel spill to clean up. When single-port refueling, make sure the port shuts off at appropriate levels.
Be extremely careful about static electricity during refueling. Static electricity increases when the temperature and humidity drop.
When dealing with cold fuel and aircraft, keep these grounding pointers in mind:
- Ground aircraft to the ground.
- Ground aircraft to the fuel tanker. Make sure the fuel tanker is grounded to the ground too.
- Ground aircraft to fuel nozzle before removing the cap and make sure all doors are closed. So to clarify, ground everything before removing the fuel cap.
If you’re not using a closed-circuit nozzle, put the regular nozzle in all the way. That lessens the danger of static and reduces the chance for a fuel spill.
It’s also important to reinstall the fuel cap before removing the ground wire from an aircraft. Otherwise, sparks can shoot between the grounding cable and the aircraft. Beef up your grounding knowledge by checking out your aircraft TMs for information. Grounding information can also be found in Army Technical Publication (ATP) 4-43, Petroleum Supply Operations (Aug 15).
Finally, spilling cold fuel on bare skin can lead to instant frostbite, as well as create an environmental hazard. Protect your skin by wearing gloves and being extra vigilant when handling fuel.
Tip 2: Cold Oil and Grease
Nothing is immune to cold, not even oil and grease. As the mercury dips, oil gets thicker and grease gels. Using the right oil, lube and grease minimizes those problems.
For example, when servicing a stone-cold aircraft’s oil systems, never fill to the brim. That’s because oil expands as it heats up and you’ll be cleaning up an overflow mess. Because oil leaks are a bigger problem in the winter, regularly eyeball connections, joints and seals.
Tip 3: Cold Seals
Speaking of seals, when cold weather hits, seals contract, increasing the chances for leaks.
Even worse, moisture can seep in and around seals and freeze. Cold turns moisture into ice and ice cuts the seals. Cold makes seals brittle and subject to cracking so check them regularly to see if they need replacing. Cold can shrink seals allowing them to leak, so allow aircraft system to get to operating temperatures before moving controls. Keeping seals and cylinders clean will prolong seal life.
Tip 4: Cold Batteries
Cold can affect batteries, but unless the temperatures drop to sub-freezing levels, sealed lead-acid batteries (SLAB) or nickel-cadmium (NI-CAD) batteries should continue to do their job. However, frequent cold starts will shorten battery life.
The H-60M has two SLAB batteries in the nose compartment and the UH-60A/L battery is located in the cabin behind the pilot seat. It could be either a NI-CAD or SLAB battery. Your best bet is to bring batteries inside from the cold when sub-freezing temperatures are forecasted.
Before starting your aircraft engines, turn on the searchlight, landing lights or some other component for 30 seconds. That warms up the batteries and helps get the engine started.
Keep SLABs warm. The cold can drain their charge much faster than it does a NI-CAD battery. When bringing either SLAB or NI-CAD batteries inside, store them in separate areas. Fumes from a SLAB battery can cause a NI-CAD battery to discharge.
Always store batteries on a shelf or on top of dunnage because bare floors will drain them.
H-60M SLAB batteries work better when warmed
If you’re using an aviation ground power unit (AGPU), the load will warm up the battery before starting the engine.
It’s always best to use an AGPU for an aircraft’s first start of the day. That helps prevent battery drain from the cold.
Tip 5: Cold Tires
Cold can reduce tire air pressure, so check your helicopter’s tire pressure often like it says in each airframe’s TM.
When tires freeze to the ground, you can use liquid deicer to break them loose. Avoid parking aircraft in wet or slushy areas. For example, if you park your aircraft on mud, the next day you may find the tires frozen in place. Whenever possible, use a platform surface of some kind under the tires to keep them off snow and ice.
Keep aircraft tires off wet ground
Tip 6: Cold Airframes
Keeping your aircraft covers and flyaway gear handy is essential in the winter. Use aircraft covers to protect every part of your aircraft.
Remove snow from aircraft…
…and make sure covers are used
If you can’t cover the entire aircraft, at least cover:
- the engine inlets.
- exhaust openings.
- pitot tubes.
- the main rotor head and tail rotor.
Never take cold weather for granted! Prepare now for the cold weather to come. Follow all guidance and precautions in the -10. And in addition, wear proper clothing when doing maintenance to keep warm so the job gets done right.