Aircraft jacking is one of the most mechanically straightforward but potentially catastrophic maintenance operations performed on the flight line or in the hangar. Lifting an aircraft off the ground exposes it — and anyone working nearby — to the risk of structural failure, tip-over, or collapse if any single element of the procedure goes wrong. For AMT candidates, understanding the principles of safe jacking goes far beyond knowing where to place a jack stand: it means understanding load distribution, jack point identification, environmental hazards, and the procedural discipline required to protect both the aircraft and the people around it.
FAA handbooks and aircraft manufacturer maintenance manuals establish the authoritative framework for jacking operations. The Aviation Maintenance Technician Handbook – General (FAA-H-8083-30) addresses jacking as part of ground handling and servicing, while specific structural data is always provided in the aircraft's approved Maintenance Manual (MM). Both sources must be consulted before any jacking operation begins.
Types of Aircraft Jacks
There are two primary jacking configurations used in general aviation and transport-category maintenance:
- Axle jacks (wheel jacks): Low-profile hydraulic jacks placed directly under the landing gear axle or strut to raise a single wheel or gear assembly. They are used for tire changes, brake work, and gear inspections without lifting the entire aircraft.
- Tripod jacks: Three-legged hydraulic jacks placed under designated fuselage or wing jack points to lift the entire aircraft clear of the ground simultaneously. Three-point jacking is the most common method for retraction tests, gear rigging, and major structural inspections.
Some large transport-category aircraft use four-point or specialized belly jacks. Regardless of type, every jack used must have a rated capacity that meets or exceeds the load it will bear, including an appropriate safety margin as specified by the manufacturer.
Identifying Approved Jack Points
This is the most critical step in the entire jacking process. Jack points are defined exclusively by the aircraft manufacturer and documented in the approved Maintenance Manual. There is no universal standard location — jack points vary dramatically between aircraft types and even between variants of the same model.
Jack points are typically marked on the aircraft structure itself, often with a stenciled symbol, a small access panel, or a distinctive structural fitting. Common jack point locations include:
- Reinforced wing spar fittings or hard points on the wing lower surface
- Dedicated structural fittings on the forward and aft fuselage belly
- Main landing gear axles or inboard strut jacking pads for axle jack operations
- Nose gear axle or steering collar for nose gear lift
Placing a jack anywhere other than a designated point risks punching through aircraft skin, collapsing a fuel cell, damaging control cables, or deforming primary structure. Even a brief, seemingly gentle lift at an unapproved location can introduce invisible cracks or permanent deformation that compromises airworthiness. Always cross-reference the aircraft MM, the illustrated parts catalog if needed, and the physical markings on the aircraft itself.
Pre-Jacking Preparation
Thorough preparation prevents most jacking accidents. Key steps include:
- Consult the Maintenance Manual: Identify the exact jack points, maximum allowable jack loads, and any weight-and-balance restrictions such as required fuel quantity or removal of heavy components before lifting.
- Inspect the jacks: Verify hydraulic fluid level, condition of ram seals, locking collar or safety lock function, and the condition of the jack pad or adapter that interfaces with the aircraft fitting. Damaged, leaking, or uncertified jacks must not be used.
- Check the jack pad adapters: Many aircraft require a specific adapter between the jack head and the aircraft fitting. Using the wrong adapter or no adapter can damage the fitting and cause slippage.
- Assess the surface: Jacks must rest on a firm, level, and clean surface. Jacking on soft asphalt, gravel, or uneven concrete is hazardous. Use spreader plates if the floor has any give.
- Evaluate environmental conditions: Wind is a major hazard during jacking. Many manufacturers specify a maximum wind speed — commonly around 25 knots or less — above which jacking operations must not be performed. High winds can tip an aircraft off jacks with little warning. Jacking operations should be conducted inside a hangar whenever possible.
- Remove or secure personnel and equipment: Clear the area beneath and around the aircraft. Ensure no one is inside the aircraft unless the Maintenance Manual specifically authorizes it, since occupant weight can shift the center of gravity unpredictably.
- Install wheel chocks and safety locks: Chock all wheels that remain on the ground before any lifting begins. Landing gear downlock pins or safety locks should be installed during jacking to prevent inadvertent gear retraction if electrical power is present.
The Jacking Procedure
When all preparation is complete, position the jacks at the approved points and verify the jack pads are properly seated. Raise all jacks simultaneously and evenly — never raise one side significantly higher than the other, as this can overload the lower jacks or induce structural twisting. A typical three-point jacking operation requires at least two technicians: one operating the jacks in sequence and one monitoring the aircraft attitude and the security of each jack.
Raise the aircraft only as high as necessary for the task. The higher an aircraft is raised, the less stable the system becomes, and the longer the moment arm for any tipping force. Once the desired height is reached, engage the mechanical safety locks on each jack's ram — these locks prevent the aircraft from descending if a hydraulic seal fails. Never rely solely on hydraulic pressure to support an aircraft. If a seal leaks or a hose ruptures, an unsupported aircraft will descend rapidly.
While the aircraft is on jacks, the work area should be treated with extreme caution. Prohibit unnecessary personnel from entering the area. Post warnings or barriers. Never allow anyone to rock the aircraft, operate heavy equipment nearby, or open large hangar doors if wind could destabilize the setup.
Lowering and Post-Jacking Checks
Lowering is performed by releasing jacks evenly and slowly, once again in a coordinated fashion across all three (or more) points. As the aircraft settles onto its gear, verify all gear is fully extended and locked before the full aircraft weight is transferred. After the aircraft is back on the ground, remove gear pins and safety devices only after confirming the aircraft is stable, then return them to their proper storage location and log their removal and reinstallation appropriately.
Inspect each jack point for any signs of damage, paint cracking, or structural deformation. If any anomaly is found, the area must be inspected further per the Maintenance Manual before the aircraft returns to service.
Why It Matters
Jacking accidents are a documented cause of serious aircraft damage and technician injury. An aircraft that tips off jacks — even a small general aviation aircraft — can cause fatal crush injuries and write the airframe off entirely. For AMT candidates, the underlying principle is this: the aircraft structure is engineered for flight loads, not arbitrary point loads from ground equipment. Only the manufacturer-specified jack points have the reinforcement to safely accept lifting loads, and the approved procedure exists to distribute those loads safely across the entire airframe.
Key Numbers and Rules
- Jack capacity must equal or exceed the load at each jack point per the aircraft MM — never improvise with undersized equipment.
- Wind limits for outdoor jacking are typically specified in the MM; a common guideline is operations should cease above approximately 25 knots, but always defer to the aircraft-specific manual.
- All jack rams must be mechanically locked before work begins under or around the raised aircraft — hydraulic pressure alone is not a safe support.
- Jack points are aircraft-model specific — no universal location applies across types; always verify in the approved MM.
- Fuel and weight configurations required during jacking (e.g., minimum or maximum fuel) are specified per the MM and must be followed to keep the center of gravity within the safe jacking envelope.
Common Test Traps
- Assuming jack points are universally located: FAA knowledge test questions may imply a standard location. The correct answer is always that jack points are specified by the manufacturer in the Maintenance Manual.
- Relying on hydraulic pressure: A common distractor suggests that as long as the hydraulic jack holds pressure, the safety lock is optional. It is never optional — mechanical locks are mandatory once the aircraft is raised.
- Neglecting environmental conditions: Wind speed limits for jacking are testable. Outdoor jacking in high winds is explicitly hazardous and must be avoided per manufacturer guidance.
- Wrong jack type for the task: Axle jacks and tripod jacks serve different purposes. Using an axle jack under a fuselage jack point or vice versa is incorrect and potentially damaging.
- Ignoring fuel and weight requirements: Test questions may present a scenario where components have been removed or fuel has been drained before jacking — an action that could shift the CG outside the jacking envelope and tip the aircraft, which is why the MM must be consulted for weight requirements before lifting.