Aircraft Jacks are a common tool used in aircraft maintenance. Aircraft jacks allow maintenance technicians to elevate the aircraft for maintenance, inspection, and repairs.
There are two main types of aircraft jacks, the axle jack and tripod jack. The axle jack is mainly used for brake service and maintenance involving tire and wheel repairs or replacement which requires the lifting of the landing gear. Axle jacks are placed directly under or in an area close to the landing gear.
The tripod jack is used in routine maintenance procedures that requires raising the nose, wing or tail section to allow maintenance personnel to work on those parts of the aircraft. Multiple tripod jacks placed in the correct locations under an aircraft will allow the entire aircraft to be lifted off of the ground. Some jacks are able to be used on many different aircraft provided the correct aircraft jack pads are used. Jack pads allow jacks to make contact with the aircraft without damaging the surface.
Most aircraft jacks, especially those used with larger aircraft, are hydraulic, however, mechanical jacks are still in use on some lighter aircraft. One main advantage of using the hydraulic jack is that a small piston pump is able to generate the large pressures required to move the jack ram and aircraft upwards with minimal effort on the part of the operator. Although they both have similar mechanical structures, the hydraulic principle which the hydraulic jack uses makes it a more complex system and as such needs additional maintenance to maintain its operation.
Choosing the correct aircraft jack and ensuring that it is properly maintained allows proper maintenance of the aircraft to be carried out, prevents the aircraft from being damaged during maintenance and also protects maintenance technicians harm as a result of the aircraft collapsing while supported by the jacks.
General Aircraft Jack Maintenance and Schedule
It is very important to pay attention to the maintenance procedure and schedule of the aircraft jack in order to prevent damage or failure that could happen as a result of negligence, to use the jack safely and efficiently, and to prolong its lifespan.
Every 90 days, certain maintenance procedures need to be completed that checks the basic condition of the aircraft jack. Some of the items that are checked are:
Inspecting aircraft jack structures such as the base plate, hydraulic cylinder assembly, the mechanical extensions, jack pads and landing gear adapters, the retaining ring and spacer blocks.
Tightening bushings on the jack frequently to prevent jack damage.
Checks for fluid leaks from the jack cylinders, seals and fittings.
The smooth movement of the jack is also checked. The ram should be able to smoothly raise to full extension. All valves should be able to open and close smoothly as well as the hand pump.
Inspecting the ram when fully extended ensures that the jack will operate correctly and extend to its full operating range. Dirt, corrosion and any wear on the ram can also be noticed while extended.
Every 12 months a proof load test is to be performed to check the load capacity of the jack. A load equal to 110% of the jack’s rated capacity is used to perform the test to ensure that the jack can lift the capacity that it is rated for without damage to the jack.
Aircraft Jack Repairs
While proper inspections and maintenance are necessary and can prevent damage, there are times when significant repairs are required on the jacks
Mechanical repairs involve repairs to the physical structure of the jack, such as replacing bent or stressed components and hardware and repairing welded joints as a result of stress or fatigue, especially to the legs for if the legs are not properly balanced, the jack may shift and cause structural damage to the aircraft.
The main repair for hydraulic components is typically to repair leaks. Disassembly and replacement of various O-rings, seals or valves is required to keep the jack operating properly. A malfunction of the ram can be caused by air build up in the reservoir, contamination of the hydraulic fluid, or the ram may have been bent by overloading or by a misalignment between the load and the ram cylinder.
AIRCRAFT JACK PROOF LOAD TESTING GUIDE
The ultimate guide to understanding aircraft jack proof load testing. Read it here.
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