Turbine engines are among the heaviest, most precisely engineered assemblies on any aircraft. A modern turbofan destined for a regional jet can weigh anywhere from several hundred to several thousand pounds, and even a smaller turboprop powerplant can weigh several hundred pounds with accessories attached. Moving these assemblies safely from storage to airframe — or from airframe to overhaul shop — is a task governed by strict engineering principles, manufacturer-specified tooling, and FAA-accepted maintenance practices. For the Aviation Maintenance Technician (AMT) working on the powerplant rating, understanding hoisting and positioning techniques is not simply a matter of knowing which bolt goes where; it is about protecting personnel, protecting costly hardware, and ensuring the engine is installed in a condition that is airworthy from the first moment of operation.
This article covers the fundamental principles behind turbine engine hoisting and positioning, the equipment involved, the sequencing of operations, critical safety rules, and the most commonly tested knowledge items on the FAA AMT Powerplant knowledge exam.
The Role of Manufacturer Data and Maintenance Manuals
Before any engine is lifted, the governing document is the aircraft manufacturer's Aircraft Maintenance Manual (AMM) and the engine manufacturer's Engine Build-Up and Installation Manual. These documents specify the exact sling assembly, adapter fittings, lift points, and weight-and-balance considerations for each specific engine model. The FAA requires that maintenance be performed in accordance with manufacturer's instructions or FAA-approved data under 14 CFR Part 43. No generic procedure overrides the specific engineering data provided for that powerplant. The AMT must locate and review the correct revision of the manual before rigging any hoist.
The AMM will identify approved lift points — typically threaded bosses or structural lugs built into the engine case or mounting structure specifically to accept hoisting hardware. Using unapproved lift points (such as accessory cases, fuel manifolds, or inlet guide vane structures) can crack castings, bend flanges, or introduce hidden damage that may not appear until engine test or flight.
Hoisting Equipment: Slings, Adapters, and Hoists
The primary interface between the hoist and the engine is the engine sling assembly. Slings are typically fabricated from high-strength steel or certified nylon strapping and are designed to accept the specific lug spacing of the engine. Many manufacturers supply dedicated sling kits as special tools, and these kits are listed in the Illustrated Tool and Equipment Manual (ITEM). Using a sling from a different engine family — even one that looks physically similar — is improper because the load geometry, attachment angles, and rated capacity may differ.
The hoist itself is most commonly a mobile engine stand hoist (sometimes called a shop crane or cherry picker) or an overhead runway crane in a well-equipped hangar. Regardless of type, the hoist must have a rated capacity that exceeds the weight of the engine assembly by a meaningful safety margin — most shops and manufacturers call for a hoist rated to at least the total lift weight plus the weight of all slings, adapters, and any accessories still attached to the engine. Never operate a hoist at its rated limit; select a hoist whose rated capacity provides an adequate margin above the total lift weight, per general guidance in FAA maintenance handbooks.
A spreader bar is frequently required when the sling attachment points are far apart or when vertical sling legs would otherwise pull inward at an angle that could damage case flanges or create bending loads on lift lugs. The spreader bar keeps the sling legs parallel to the engine's vertical axis, maintaining pure tensile loading in each attachment point. The manufacturer's manual will specify whether a spreader bar is required and, if so, its minimum length.
Engine Stands and Dollies
Once removed, a turbine engine must be immediately secured to a certified engine stand or shipping cradle. Engine stands are designed to accept the engine's mount points — typically the same forward and aft mount pad locations used on the airframe — distributing the engine's weight through its structural frame rather than through its cases or accessories. Engine stands are rated for specific models; an undersized or incorrect stand can tip, collapse, or allow the engine to shift and sustain FOD-type internal damage from impact.
During positioning in the shop or for transport across the ramp, engine dollies (low-profile wheeled cradles) allow the engine stand to be rolled. These must be secured against rolling whenever the engine is being hoisted onto or off the stand, and wheel brakes or chocks must be set. A rolling dolly under a suspended engine is a serious hazard because movement changes the geometry of the lift and can allow the engine to swing.
Rigging and Balancing the Engine Before the Lift
A critical but sometimes overlooked step is pre-lift balancing. A turbine engine is not a uniform cylinder; accessories, gearboxes, and components cluster on specific sides of the core, making the engine's center of gravity (CG) offset from its geometric center. If the sling is rigged symmetrically without accounting for CG offset, the engine will hang at an angle once lifted. This tilt can make it impossible to align mount points in the airframe and can place unequal loads on the lift lugs.
To address this, manufacturers design adjustable sling assemblies with turnbuckle or leveling mechanisms, or they specify the attachment positions that produce a nominally level hang. The technician should always perform a trial lift — raising the engine only slightly off its stand or pallet, per the applicable AMM procedure — and observing whether it hangs level longitudinally and laterally. Any unacceptable tilt should be corrected by adjusting the sling attachment positions or the leveling device before the engine is raised to work height. This trial lift also confirms that all attachment hardware is properly engaged and that no binding or abnormal loading is present.
Clearance Planning and Spotting
Large turbofan installations — particularly wing-mounted podded engines — require the hoist and engine to be precisely spotted (positioned horizontally) beneath the pylon before the lift begins. Many AMMs specify a detailed sequence: position the engine stand at a specified lateral offset from the wing centerline, align a reference mark on the engine inlet with a reference on the pylon, and then raise the engine along a defined vertical path that keeps the fan case clear of cowl tracks and pylon fairings. Any deviation from this path risks scoring the fan case on pylon structure or catching inlet hardware on the airframe.
In nacelle installations on business jets or turboprop aircraft, the procedure may require tilting the engine nose-up or nose-down to clear the firewall or forward bulkhead as it slides into the nacelle. The AMM will specify the angle and the sequence of motion. The use of guide pins — temporary alignment pins installed in one or more mount holes before the engine reaches final position — is standard practice; guide pins accept lateral loads during final approach so that the mount bolts do not carry shear forces while being inserted.
Connecting and Torquing Mount Hardware
Once the engine is in position with all mount pads aligned, mount bolts are installed finger-tight, guide pins are removed and replaced with the remaining bolts, and then all hardware is torqued in the sequence and to the values specified in the AMM. Torque values for engine mount hardware are critical: under-torque allows fretting and fatigue; over-torque can yield the bolt or damage the mount fitting. All safety wiring or cotter pinning of mount hardware must be completed before any load is transferred from the hoist. The hoist should not be disconnected until the engine is fully mounted and all primary structure is secure.
Key Numbers and Rules
- Hoist capacity: Always select a hoist rated above the total suspended weight; operating a hoist at its rated limit is not safe practice — use a hoist with adequate margin above the total lift weight.
- Trial lift height: Lift the engine only slightly off its stand or pallet — the exact height is not a fixed FAA figure but is set by the applicable manufacturer's AMM — for the initial check of sling geometry and balance before proceeding.
- Approved lift points only: Using unapproved attachment points violates 14 CFR Part 43 and manufacturer data requirements.
- Guide pins: Guide pins are used during final positioning to prevent shear loading on mount bolts during alignment; the specific number required is specified by the applicable AMM and varies by aircraft/engine type.
- Torque sequence: Always follow the AMM-specified torque sequence; random torquing of multi-bolt mounts creates unequal stress distribution.
- 14 CFR Part 43: All maintenance must be performed per approved or acceptable data; no improvised rigging substitutes for manufacturer-specified tooling.
Common Test Traps
- Assuming any lift point is acceptable: FAA test questions often probe whether the technician knows to use only manufacturer-specified lift points. Accessory cases and inlet structures are never approved lift points.
- Ignoring the trial lift: Test scenarios may describe skipping the trial lift and proceeding directly to the full hoist. This is incorrect procedure — a trial lift is always required to verify balance and hardware engagement.
- Confusing hoist rating with working load: A hoist's rated capacity is not the load you should routinely apply; always select a hoist with capacity exceeding the lift weight to maintain a safety margin.
- Removing the hoist before all mount hardware is torqued and safetied: The hoist must remain attached and supporting engine weight until primary mount structure is fully secure — not just until the first bolt is finger-tight.
- Using the wrong sling assembly: Test questions highlight that sling kits are engine-model specific. A sling that fits physically is not necessarily approved for that engine's load geometry or weight.