ASAP Parts 360 Blog

how and why: aircraft engine preheating

If it's cold enough, shortly after take off, a single cold start can cause severe aircraft engine problems. The degree to which a cold start will damage an engine depends upon factors like the type of engine, the engine’s age and condition, whether the engine has steel or chrome cylinders, and what kind of engine oil is being used. As a general rule, a “cold start” occurs when the engine is at a temperature below freezing (32F or 0C). Any start below 20F or -7C is very dangerous to a power plant.

The cause of “cold-start” damage is due to dissimilar metals used in aircraft engines and their reaction to cold weather. When cooled, aluminum alloy parts like the crankcase, pistons and cylinder heads, contract twice as much, as the contraction of steel parts like the crankshaft, camshaft, connecting rods and cylinder barrels. When these parts contract at the same time, there is no room left between metals for oil to lubricate and avoid friction and therein is a recipe for disaster. This point is why the myth of warming up the engine oil to avoid “cold start” damage is a false hope. Even with warm oil, if there is no clearance between metal parts for oil to go, it doesn’t matter how warm the oil is. With this being said, it is absolutely essential that preheating occur prior to the start of the engine.

The best way to preheat an aircraft engine is to leave the aircraft overnight in a heated hangar. 8 to 12 hours in a 40F hangar will heat every part of the airplane at an even temperature and ensure a safe start and proper functionality. Currently, most Fixed Base Operators (FBOs) charge anywhere between $20 to $50 to store a 310 aircraft overnight. An alternative to overnight hanger heating is multipoint electric heaters. These heaters attach directly to the oil pan, the crankcase, and each cylinder. A few hours plugged into a 115V or 230V power supply and you can at least be assured to have warm cylinders, a warm case, and warm oil when you start up.

In extreme cold, or if you have to preheat outside - particularly if its windy - engine and prop covers are a great way to insulate the engine compartment and keep most of the heat generated by your multipoint electric heater from escaping. One compelling advantage of insulated engine and prop covers is you may be able to get away with not preheating at all. Covering the engines right after landing and only staying on the ground for four hours or less, the covers can retain the natural heat from the engine. Lastly, some FBOs use large forced-air preheating units that are readily accessible for use to preheat an aircraft before departure.

At ASAP Parts 360, owned and operated by ASAP Semiconductor, we can help you find the aircraft engine solutions you need, new or obsolete. As a premier supplier of parts for the aerospace, civil aviation, and defense industries, we're always available and ready to help you find all the parts and equipment you need, 24/7x365. For a quick and competitive quote, email us at sales@asapparts360.com or call us at +1-708-387-7800.

pumped up: hydraulic systems in aircraft

No matter their size, all aircraft require some kind of mechanism to power systems like landing gear, brakes, flaps, and various flight controls. All mechanical systems require some sort of medium through which they apply force and pressure, and in a hydraulic system, that medium is a liquid or oil. For comparison, pneumatic systems rely on compressed air or gas. In this blog, we’ll break down some of the most common applications for hydraulic systems, and how exactly they work.

Hydraulic systems enjoy several benefits over pneumatic systems: because they rely on liquids that are non-compressible, there is no delay in their movement, whereas a pneumatic system often has a delay as gasses are compressed. Additionally, because hydraulic oil is non-compressible, hydraulics can offer more weight, whereas air and gas can cause a device to shake and move around when the air pressure fluctuates.

Hydraulic fluid must act as a coolant, lubricate parts of the system, and accurately transmit pressure. Hydraulic fluid comes in three different types:

Mineral oil, dyed red and made from kerosene petrochemical products. Mineral oil inhibits foaming and corrosion, is chemically stable, and handles temperature changes well.
Synthetic oil, made from phosphate ester and is typically dyed purple (can also be amber or green). The biggest drawback of synthetic oil is that it can eat away at insulation and degrade wiring, so safe storage is absolutely necessary.
Vegetable oil is colored blue and made from alcohol and castor oil. Vegetable oil is only seen in older aircraft, as it can cause corrosion and sludge to build up.

Small aircraft will typically use mineral oil, but manufacturers will have their own recommendations.

The core of hydraulics revolves around Pascal’s Law, which states that if pressure is applied to liquid anywhere in a system, this action causes equal pressure to be distributed throughout the entire system. This means that a small device applying pressure in one area of the system can be transferred to other areas.

In aircraft, hydraulics are used in Aircraft landing gear, both to raise and lower them from deployment, in braking systems, in manipulating flight control surfaces like ailerons, flaps, and elevators, to control thrust reversers, and a wide range of other tasks.

At ASAP Parts 360, owned and operated by ASAP Semiconductor, we can help you find all the hydraulic systems and parts for the aerospace, civil aviation, and defense industries. We’re always available and ready to help you find all the parts and equipment you need, 24/7-365. For a quick and competitive quote, email us at sales@asapparts360.com or call us at +1-708-387-7800.

torque tools for helicopter maintenance

Aircraft fasteners are incredibly important components of any machine, and helicopters are no different. The main rotor of main helicopters is held in place by a so-called “Jesus nut,” called such by flight crews because to lose it was to have the main rotor detach completely and come face to face with him. While some helicopters do not feature a Jesus nut, all of them require fasteners that are precisely secured to ensure safe and controlled flight operations. This is why precision torque tools are so critical for helicopter maintenance, as every single nut, bolt, and screw must be tightened to exact specifications. If left loose, one can come free and damage the engine, propeller blades, or other components while in flight. If tightened too far, they can stress the housings and cause them to crack from the pressures and vibrations of flight.

The most critical components for fastening are the helicopter engine’s shafts connecting to the main and tail rotor, and the swashplate assembly. The shafts that power the main and tail rotor spin at extremely high rates per minute, and must be thoroughly secured. The swashplate assembly, meanwhile, connects the pilot’s control inputs to the main rotor and allows them to fly the helicopter. Therefore, any errors in fastening the swashplate will cause the controls to not work properly.

For all these reasons, using the right tools is essential. Torque wrenches, torque screwdrivers, and calibrated power assembly tools are best for when repairing helicopters and conducting preventative maintenance. The heavy-duty bolts on helicopter engines and transmissions and the screws on airframes must be tightened to very precise specifications, so pulse tools and air screwdrivers with an automatic shut-off are perfect for these requirements, speeding up assembly and disassembly, reducing operator fatigue, and delivering precise torque control throughout the process.

Mechanical systems like engine interiors, power transfer systems, and transmission rebuilds are more variable in their torque needs. Adjustable hand operated torque screwdrivers torque wrenches, and click wrenches signal to the operator when they are reaching the torque limit through physical and auditory means, while cam-over and breakover wrenches physically stop the user from over-tightening.

On the smaller and more precise level of controls and control linkages, dial torque screwdrivers and adjustable torque screwdrivers can precisely monitor and adjust the torque applied to aviation fastener components. Both types have memory functions that allow mechanics to precisely verify that everything is functioning and tightened properly.

importance of proper bearing mounting

Aircraft bearings are a very useful type of fastener, allowing for constraint of movement to specific motions, all while reducing friction between the moving parts. This requires that bearings be accurately installed, lest the bearing’s life expectancy be cut short along with other problems. If a bearing is too loose, movement between components is less restricted, leading to problems such as wear, fretting, scoring, fracturing, and more. When a bearing is too tight on the other hand, increased force for mounting may be required, also leading to possible bearing fractures. According to estimates, about 16% of premature bearing failures are caused by poor installation of bearings. So what are some of the methods to correctly install a bearing, and what are things to avoid?

The two main methods of bearing mounting is through what is referred to as “cold” and “hot” mounting. Cold mounting, otherwise known as mechanical mounting, is mostly used for bearings that range from small to medium. Hot mounting utilizes hydraulics for installation and is more recommended for larger bearing mounting. By utilizing these techniques and using the right fitting tools, correct installation can be done easily, and will help to avoid problems that may arise in the future, extend the life expectancy and performance of the bearings, as well as decrease the amount of downtime for machinery due to repair caused by improperly installed bearings.

With cold mounting, using the correct fitting tools can protect the bearing from receiving force damage and ensure a proper amount of force is used during aircraft mounting. With cold mounting, the mistake many people make is to use hammer and pipes, which can lead to damage of the raceways, as well as allows for contamination, such as dirt, to enter the bearing and lead to friction. The bearing’s rolling element can also face damage if the pipe slips during installation.

With hot mounting, preheating the bearing can be very beneficial as it allows the inner ring to expand, thus making installation easier. This method also avoids dirt contamination as well as serves as a quick method of mounting. Mistakes that lead to improper hot mounting is through utilizing hot oil baths, which can lead to contamination of the bearing, or by using open flames which can be dangerous in itself. Standard protocol recommends heating through the use of induction before the bearing is installed, allowing for efficiency, safety, and control during the mounting process.

comparing aircraft maintenance quotes the right way

When reviewing a quote or an invoice, it’s understandable to want to scrutinize every item and every price down to the final number. But when revising a quote presented to you for MRO (Maintenance Repair Overhaul) or other types of aircraft maintenance manual, you have to ask “what does this quote include?” If you are getting maintenance done, then you want to make sure that nothing is missed, which is why you ought to start questioning if any item not included with your quote should be. For a better idea on what items you need to check on, read the discussion points below. If you bring these up to your sales representative, you’re not only avoiding sticker shock, you’re also enabling more transparent communication between you and your supplier.

Paint

There are many variables that can influence your quote when it comes to applying paint to an aircraft’s exterior. Be sure to ask if stripes and stripe colors are included in the paint job, along with paint on the wheels and landing gear. Some people might assume that they are included but as each repair station is operated differently, that is not always the case.

Engine

In order to get the most accurate quote for engine work, it’s crucial that you promptly provide your logbook. The logbook gives the repair station all the details and history they need to ensure that they cover every sector of the aircraft, including required airworthiness directives, service bulletins, and life-limited component replacements. Before any work starts, it’s also important to note the level of service that you’re being quoted for the base engine overhaul manual price because if you’re being quoted the lowest minimum for an engine, then you’ll probably be paying more towards the end of service work.

Landing Gear

A landing gear quote will often come in different price packages, the most popular being the Not To Exceed (NTE). When you get an NTE price structure, that means you receive the assurance that the final number you pay will not exceed your quote. There is also Standard and Firm Fixed. The former refers to all the labor that will be necessary to perform inspection or overhaul, while the latter entails that you be handed a final bill before gear arrival. For Firm Fixed, your quote will often come with a no bill back guarantee. Before finalizing and agreeing to a quote, you should also be sure to note any contract exclusions, the labor flat rate, and if your quote includes shipping costs for outsourced components.