Aircraft Jacks – Maintenance & Repairs

Jacks are used if the aircraft needs to be lifted off the ground for maintenance or repair. On the aircraft, specific jack locations are designated (based on the CG – Center of Gravity) to indicate where they should be used and how much force to use. To prevent composite surface damage, jacks should be utilized to raise or support the plane. Hoisting, on the other hand, is another method of lifting planes. However, because the plane can sway, hoisting should be avoided for maintenance tasks.

 

Aircraft Jacks – Types and Selection:

There are three main types of aircraft jacks: hydraulic, pneumatic, and screw. Each type has its own advantages and disadvantages that should be considered when selecting a jack. Hydraulic jacks are the most common type of jack used in aviation due to their precision and ability to lift heavy loads. Pneumatic jacks are powered by compressed air and are typically used for lighter loads and screw jacks are the most basic type of jack and use a screw mechanism to raise or lower the load.

 

  1. Hydraulic: Hydraulic jacks are driven by a pressurized liquid, such as oil, and are by far the most common type of jack. They can lift weights ranging from a few tonnes to hundreds of tons. There are four types of hydraulic jacks: bipod, tripod, quadrupod, and axle. Tripod and axle jacks are the most prevalent among hydraulic jacks.
  1. Tripod Jacks: The Tripod jacks (three-legged hydraulic jacks) are portable hydraulic jack that stands on three legs. Steel tripod, caster wheels, hydraulic pump assembly, and hydraulic cylinder are included in these jacks. Tripod jacks may be used to service and maintain the nose and fuselage sections.
  2. Axle Jacks: They are most often used to keep tires, wheels, and struts operating well. They are attached to the nose gear or main landing gear to raise the aircraft. A bypass valve is built into the jack for safety. If the applied load exceeds 10% over the specified load capacity, the bypass valve will open fluid flow to avoid damage if required. Hand-carried, horseshoe and outrigger are three types of axle jacks commonly seen in aviation, all of which satisfy varying loading needs.
  1. Pneumatic: Pneumatic jacks are powered by compressed air and are typically used for lighter loads. However, they are less precise than hydraulic jacks and tend to leak air, which can be dangerous. For this reason, they are not as commonly used as hydraulic jacks.
  2. Mechanical / Screw: Screw jacks are the most basic type of jack and use a screw mechanism to raise or lower the load. They are simple to use and maintain but can only be used for smaller loads. These jacks are operated manually with a hand crank and are often used for smaller aircraft or in tight spaces.

 

Aircraft Jacks – Naming and Selection:

Jacks are identified using a specific labeling system to ensure proper care and maintenance. For example, a model may be labeled A25-1HS. The “A” indicates axle, the number 25 represents the maximum load capacity in tons, and the following two letters identify whether the jack is outrigger (OR), hand-carried (HC), or horseshoe (HS). Tripod jacks are similarly labeled as axle jacks. Consider the tripod label “T20-1VH5,” for example. The only difference is the “T” and the last three items are identical. A tripod is classified as a fixed height (FH) or flexible height (VH). A number at the end of the model designation indicates how many leg extension kits may be added; in this instance, there are five.

 

The selection of an aircraft jack should depend on the application and the following factors:
  1. Capacity or weight that needs to be lifted (in tonnes)
  2. Aircraft components / section to be lifted
  3. Space availability in which the jack needs to be used
  4. Construction of Jack – Hydraulic, Pneumatic, and Screw type
  5. Aircraft composite surface on which the jack shall be pointed
  6. Terrain or ground conditions in which the aircraft jack will be used
  7. Lifting power of the jack
  8. Portability – Hand-held or fixed jack

 

Hydraulic Jacks – Maintenance and Operational Guidelines:

Preoperational maintenance is critical to ensure that aircraft jacks are safe to operate. Depending on the type of hydraulic jack, OEM (Original Equipment Manufacturer) maintenance guidelines should be studied before using the jack:

 

  1. Inspect the jack for damage and make sure all parts are in good working condition.
  2. Be aware of the weight and balance limitations of the aircraft.
  3. Make sure the surface on which the jack will be used is level and firm.
  4. Use chocks on all wheels that the jack will not lift.
  5. Never get under an aircraft that is supported by only a jack.
  6. Never exceed the rated capacity of the jack.
  7. Do not use the jack in an environment that could present a fire or explosion hazard.

 

Aircraft Jacks – Proof Load Testing:

An aircraft jack calibration is also known as a Jack Proof Load Test. Manufacturers recommend that aircraft jacks be proof tested regularly, which is why FAA auditors inspect whether MROs and FBOs comply. The FAA says that Part 145 repair stations should use manufacturer-specified maintenance and testing procedures.

Proof load testing is a technique for determining the fitness of the load-bearing structure (the jack) to ensure that it can sustain structural integrity under normal usage. In other words, proof load testing ensures that the jack meets the manufacturer’s design specifications.

All jacks must be load tested before being used on an aircraft. The load test should be conducted at the maximum possible weight that the jack will lift. This will ensure that the jack is in good working condition and will not fail while in use. The following steps can be followed to conduct a load test:

 

Step 1: Set the jack on a firm, level surface and extend the ram to its full length.

Step 2: Securely attach a weight equal to the maximum lifting capacity of the jack to the ram.

Step 3: Slowly raise the weight off the ground and hold it in place for the time specified by the OEM, in general, at least for two minutes.

Step 4: Lower the weight to the ground and remove it from the jack.

Step 5: Inspect the jack for any signs of damage or leakage.

Step 6: Repeat the load test with a weight that is half of the maximum lifting capacity of the jack. If the jack fails at any point during the load test, it should be removed from service and repaired or replaced.

 

Although the Federal Aviation Administration does not require that all jacks be tested regularly, hydraulic jack manufacturers recommend doing so. Tronair, for example, a major producer of both axle and tripod jacks, advocates proof load testing on an annual basis. The FAA requires repair stations to identify hazards and safety concerns and maintain the effectiveness of safety risk controls in accordance with Part 145 rules (as mentioned in the above sections). A faulty jack might lead to dangerous situations. Aircraft jack-proof load testing verifies the jack’s dependability. Quality Control and Safety Assurance Systems have an obvious overlap with these regulations.

 

Proof Load Testing – Benefits:

The proof load testing verifies that the outer and inner components of the device meet the manufacturer’s standards to minimize the chance of failure. Internal or external quality compliance demands may be met through frequent proof load testing. As a high-quality aircraft maintenance provider, practicing good jack maintenance and testing adds to operators’ value.

By contract, aviation maintenance businesses may be required to provide proof of annual aircraft jack proof load testing in addition to other quality procedures. Incorporating manufacturer-suggested preventative maintenance and proof load testing into your internal quality assurance program can help customers feel more secure. Following are certain benefits of Proof Load Testing:

 

  1. Meets internal quality control systems
  2. Enhance internal Safety Management Systems
  3. Meet or exceed FAA safety and quality regulations
  4. Confidence in the staff of equipment reliability
  5. Prolonged life of aircraft jacks as well as the aircraft it is being used on
  6. Quality and safety procedures communicate value to customers
  7. Increased competitive advantage over other facilities that do not elect to follow recommended jack maintenance and testing schedules

 

Need for Preventative Maintenance of Jack – Why is it necessary?

There is no way for AMTs to tell if a jack is trustworthy until it is too late, when only testing is based on proof. Numerous variables can influence the function of the jacks. Still, the most typical issues include a seal failing, contamination (particularly rust) causing flaws in the cylinder, a check ball valve not seating firmly, and other factors causing hydraulic fluid to leak, resulting in underperformance or total failure of the jack. This is why hydraulic system overhauling plans include a check of the system.

Equipment can also suffer integrity loss if subjected to Outer structural damage. Structural failure may result from mishandling, damage, or years of wear and tear. When used to lift a plane, for example, a tripod jack’s dented leg might easily collapse due to structural weakness. Therefore establishing a Preventative maintenance plan for jacks is of utmost importance.

 

Preventative Maintenance and OEM Maintenance Recommendations:

Maintenance Schedule: Manufacturers recommend that hydraulic jack(s) be maintained and tested once every 12 months. Testing may also be required outside of the usual time if an event takes place that might harm the jack. Being dropped, for example, or anything being placed on the jack that can damage the structure or hydraulic system. Following is an example of manufacturer-recommended maintenance and testing procedures. Note that these techniques may differ somewhat based on the type of jack you are using.

90-Day preventative maintenance checklist:

Leaks in the hydraulic system should be investigated:
Check for corrosion, bending, cracking, excessive wear, and other problems with the jack’s structure.
Fluid levels should be checked after the rams are fully retracted.
Examine rams for corrosion, foreign material, excessive wear, or leaks around the seal to extend them.
Examine the paint for signs of deterioration and fix any exposed flaws.
Raise the ram to full extension at least once after actuating the hand pump.
Add Buna N-compatible DoAll, RPM, LPS, or equivalent water repellant (for tripod jacks) to the rams.
Verify that the release valve is open and that rams fully retract.
Lubricate the casters (if applicable).

 

All of the above servicing may be accomplished without the manufacturer’s help or a third-party service provider. The only distinction is that if you do it yourself, the maintenance will not be certified, which might or might not meet your internal or external compliance requirements.

Annual load test Procedure: All of the items on the 90-day maintenance checklist are included in addition to:

  1. Checking the hydraulic fluid for contamination (dirt or water) and then draining and refilling it if required.
  2. Ensure that the jack’s rated capacity is tested to 105-110% of its capacity. This means that the tester will apply a strain higher than what is typical in real-world applications to ensure complete safety and trustworthiness.

 

Note:

 

Re-certification of Aircraft Hydraulic Jack:

Within the nation of usage, re-certification of the jack must be done regularly per locally applicable/country-specific aircraft regulations. In addition, re-certification can be carried out under the following conditions (for axle hydraulic jacks):

  1. When the jack’s integrity has been lost (for example, owing to incorrect application or usage with apparent damage).
  2. Repairs on structural/load-bearing components (such as the base plate and/or ram-set) and all hydraulic elements (valves, tubes, etc.).
  3. After the ram-set seal is replaced.

 

For re-certification, the following criteria must be observed/checked:
  1. All components are tested for functionality.
  2. Overpressure check: Check the overpressure valve, which must engage between 110 and 125 percent of the jack’s nominal capacity. Between the ram-set and the test stand, verify that the ram-set is driven against a suitable test stand while utilizing the jack’s motor pump (air-hydraulic pump). If outside parameters are exceeded, reset the overpressure valve on the motor-pump assembly.
  3. Hydraulic system/tightness check: Check the tightness of the hydraulic system by driving the ram-set against a suitable test stand with a load measuring device between the ram-set and the test stand, up to the jack’s nominal capacity. Leave the system alone for 10 minutes before running the motor pump and observe how much weight is on the test stand. When comparing two jacks, look for one that has an acceptable drop in load/pressure of less than 2% within 10 minutes.

 

Selection of On-site or Off-site Jack Proof Load Testing:

Jack proof load testing can be done onsite, at a calibration lab, or at the manufacturer (OEM). Each choice comes with advantages and disadvantages. Downtime, shipping charges, and convenience must all be considered by MROs and FBOs. The most appropriate solution for a particular company should be selected based on the application and inventory available.

Offsite Testing (OEM Site): Due to the size of the jack, repairs, overhauls, and calibrations onsite at the manufacturer’s facility may require significant transportation effort and expense. Also, while the jacks are transported for maintenance at OEM facilities, this critical ground support equipment is unavailable to aircraft operators or maintenance providers for some time. To avoid this waste of time and money, the on-site Proof Load Testing service allows maintenance organizations to have their jacks fixed and calibrated on-site.

On-site Proof Load Testing: The testing system may be used to test a variety of aircraft tripod jacks and axle jacks. On-site Proof Load Testing is built on a modular basis to match the various OEM needs. As a result, it meets the need for rigorous tests on a wide range of jacks in a pressured environment. In terms of quality and sustainability, On-site Proof Load Testing is tailored to meet the demands of operators. Following are the commercial and operational benefits of On-site Proof load Testing:

 

 

Aircraft jacks are a type of aviation equipment designed to lift the aircraft safely for inspections and maintenance activity that would otherwise be challenging to reach out to various aircraft components. Therefore investing in preventive maintenance of your Aircraft Jacks (GSE) can prevent you from schedule breakdowns, ensure high aircraft up-time, and extend the life of the equipment. Ground personnel must thoroughly study the operation and service manuals supplied by the equipment manufacturers and maintain a maintenance log, which must be completed at each servicing interval, detailing all work on the system.

 

e2b calibration offers industry-leading consultancy and certified PM services for your aircraft jacks. At e2b Calibration, we maintain and troubleshoot your jacks so that you can concentrate on maintaining your aircraft. Our labs are ISO/IEC accredited and operated by a team of qualified experts providing training and consultancy services on GSE Maintenance and inspection. Our verifiable services are unmatched in the industry. Contact e2b calibration for all your equipment calibration needs.

 

AIRCRAFT JACK PROOF LOAD TESTING GUIDE

The ultimate guide to understanding aircraft jack proof load testing.
Read it here
March 15, 2022 GSE, Tronair Joshua Gilstrap