From flight data to a hard-landing inspection

Data, not impressions

When a flight crew reports a "firm" or "heavy" arrival, subjective impressions are not enough to determine aircraft airworthiness. Modern airframes rely on digital flight data to objectively evaluate landing severity, prevent unnecessary groundings, and guide structured inspection procedures when structural limits are exceeded.

Objective flight data vs. crew perception

Pilot perception of landing impact can vary with weather, seat position and flare technique. To remove the ambiguity, the aircraft condition monitoring system (ACMS), hosted on Airbus aircraft in the data management unit (DMU), continuously evaluates flight parameters sampled from the aircraft's sensors and flight controls, for example eight times a second (every 125 ms) around touchdown.

The DMU checks these values against threshold limits. If the landing is within limits, operations continue normally. If a limit is exceeded, it automatically produces a load report, and a Phase 1 inspection is required.

Key parameters recorded at touchdown

• Vertical acceleration (g): the peak load factor measured at the aircraft center of gravity.
• Sink rate (radio altitude rate): descent velocity at the instant of main gear touchdown, in feet per second or feet per minute.
• Aircraft gross weight: the total mass at touchdown, used to assess the energy the structure had to absorb.
• Pitch, roll and yaw: an asymmetric touchdown, such as single-gear contact or a crabbed landing, significantly alters load distribution across the airframe.

Load reports: an A330 example

When peak parameters cross specific threshold envelopes, the DMU automatically generates a dedicated load report, such as the Airbus LOAD REPORT <15>, or the Boeing equivalent. It is printed automatically and can be transmitted to the ground.

The limits below are illustrative only, based on typical Airbus A330 training values. Maintenance personnel must always consult the aircraft maintenance manual (AMM chapter 05) applicable to the specific tail number.

• Hard landing: vertical acceleration above 1.75 g at the center of gravity, or a sink rate above 10 ft/s (600 ft/min) below 155 tonnes, or above 9 ft/s (540 ft/min) at or above 155 tonnes.
• Overweight landing: landing mass above the maximum landing weight (MLW) combined with vertical acceleration above 1.4 g or a sink rate above 6 ft/s (360 ft/min). This evaluates combined mass and descent energy at touchdown.

The golden rule of data availability

If a hard or overweight landing is reported or suspected, but the load report is unavailable or corrupt, maintenance personnel cannot assume the landing was safe. The hard-landing inspection must be performed.

The phased inspection strategy

Hard-landing inspections in AMM chapter 05 are structured in progressive phases so that maintenance scope and labor match the physical evidence. Phase 1 is an external visual inspection. If it finds no damage, the aircraft is signed off and returned to service. If it does, Phase 2 inspects the internal structure. If Phase 2 finds no further damage, the aircraft is returned to service; if it finds secondary damage, Phase 3 follows.

Phase 1: primary visual and external inspection

Phase 1 focuses on accessible exterior structures that absorb the primary impact loads:

• Landing gear and wheel wells: check shock struts for bottoming, fluid leaks, structural deformation and cracking, and wheels and brakes for thermal or mechanical stress.
• Engine pylons and nacelles: inspect pylon attachment fittings, engine cowlings and thrust reverser structures for wrinkles, sheared rivets or popped fasteners.
• Fuselage and wings: examine skin panels for shear buckling (diagonally wrinkled skin), loose or missing fasteners, and cracks around wing-to-body fairings and door cutouts.
• Avionics bay: inspect electronics racks, shock mounts and heavy units for displacement or failure of structural supports.

Phase 2: detailed internal structural inspection

Phase 2 is triggered only if Phase 1 reveals damage such as structural distortion or sheared fasteners.

• Opening access panels and cargo liners to inspect frames, stringers and wing spars.
• Nondestructive testing, such as eddy current or ultrasonic inspection, around fastener holes, pylon mounts and landing gear attachment pins.

Phase 3: component removal and major work

Phase 3 is triggered if Phase 2 reveals secondary structural deformation or significant cracking.

• Removal of engines or landing gear assemblies for detailed shop-level alignment checks and testing.
• Structural replacement or heavy structural repairs in accordance with the structural repair manual (SRM).

Integration with flight data monitoring

The connection between engineering maintenance and flight data monitoring (FDM) programs ensures continuous safety verification. AviationDevy's Flight Data Analysis tool works with these kinds of parameters.

• Safety engineering correlation: raw data recorded by onboard units is fed into flight data analysis software used by safety departments.
• Trend monitoring: safety teams analyze long-term trends in touchdown sink rates across the fleet to refine crew training and detect localized runway or approach path issues.
• Objective engineering record: recorded data gives engineers an objective record of the event, protecting airframe integrity while preventing unnecessary groundings. FDM programs themselves are run as confidential, non-punitive safety programs.

Key takeaways

• Data over impression: recorded parameters (g load, sink rate, gross weight) determine whether a structural check is required, not pilot memory.
• No data means inspect: if flight data cannot be retrieved to show the landing was within limits, the AMM requires the inspection.
• Phased escalation saves time: Phase 1 visual checks keep aircraft moving, and escalation to Phase 2 or 3 occurs only when damage is found.