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Loading of Aircraft with Cargo
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Revision as of 11:40, 25 October 2017 by Editor1
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Safe operation of aircraft requires all hold cargo and baggage to be weighed (or an accurate estimate of weight provided by using “standard” values), it must be loaded correctly and secured to prevent movement in flight.
Loading should be in full accordance with the generally applicable regulations and limitations, the operators loading procedures and in accordance with the instructions given by the person with overall responsibility for the loading process for a particular flight. These loading instructions must match the requirements for baggage/cargo distribution stated within the aircraft load and trim sheet.
The Operational Safety Issues
In recent years security considerations have led to rigorous procedures to ensure ‘baggage reconciliation’, which ensures only accompanied baggage is loaded, unless a special additional validation process for each unaccompanied bag has been followed.
Weight distribution between holds has a considerable effect upon the C of G of the aircraft; load distribution will be specified on the Loading Instruction Form by hold, or by hold compartment in the case of larger under floor hold areas..
Many narrow body short haul aircraft are bulk loaded with loose individual items of baggage and cargo. In this case, baggage loading will be by item count, with prescribed assumptions about the average weight per bag used to complete the load and trim sheet; precise figures will often vary according to NAA regulations or be more restrictive to meet the aircraft operator’s own checked baggage rules. Average checked baggage standard weight assumptions usually vary depending on whether the flight is domestic, international, charter (holiday flight) or scheduled. Standard baggage weights must be applied with care. Incidents have occurred where standard weights have seriously under-stated the actual mass of the loaded baggage causing both an error in the total mass of the aircraft and a centre of gravity outside the approved safe envelope.
Netting is used to restrain bulk loaded loose baggage items within holds so that they do not move in flight. Any load that shifts in flight will move the aircraft’s centre of gravity and can cause control difficulties (in extreme cases causing loss of control) and prevent baggage door opening post flight. Cargo netting may also be used to divide larger holds into sections.
Bulk Loading is usually accomplished by delivery of items to the aircraft in a baggage train of towed trailers. To help ensure each hold compartment is loaded correctly, a particular trailer may only contain the baggage destined for only one designated compartment. The trailer is unloaded into the aircraft hold via conveyor belts and finally positioned in the hold by loaders working within it. Usually, bulk loading of baggage items uses a system whereby loading crews are informed that the last bag for loading on a particular flight has arrived by use of an ‘End Bag’ identification tag - the tag is applied to the last checked bag sent to the aircraft. A system of stickers and a reconciliation sheet may also be used, where each printed baggage tag has a bar-coded sticker, which is removed and stuck onto the re-conciliation sheet as the bag is loaded. This helps ensure that all checked baggage for that flight has been loaded and accounted for.
Unit Load Devices
Most wide bodied aircraft, and increasingly some narrow bodies, are able to use the much simpler system of aluminium containers called Unit Load Devices (ULDs). These can be used to consolidate baggage or cargo items before being loaded into the aircraft hold by specialised hydraulic lift equipment. The ULDs are then manoeuvred manually to a final position on board by use of a roller floor, before being finally secured in position.
ULDs must either be weighed, or the number of baggage items per container must be within a specified range and standard baggage unit weights applied.
Under either system, special procedures may be prescribed for abnormal loads such as:
- those covered by Dangerous Goods Regulations
- heavy items
- oversize items
- items with have unusual dimensions/proportions.
Heavy objects which exceed the hold floor-loading limit published in the AFM may be able to be carried if prescribed arrangements for load spreading are available and applied.
Mass and Balance Gross Error Checks
A load instruction/report form will be issued for every aircraft departure to instruct loading teams on the quantity of baggage/cargo to be loaded into each hold. Where a computerised or electronic load and trim sheet is prepared on behalf of the operating crew, usually the handling agent or airline will produce the Load Instruction/Report Form with reference to the load and trim sheet. The Load Instruction/Report form will then be given to the loading supervisor to instruct the load team how the aircraft needs to be loaded and to record formally the actual loading and any deviations.
When the operating crew produces a manual load and trim sheet, the crew, in consultation with the loading supervisor, may also complete the Load Instruction/Report Form.
Once the aircraft is loaded, the Load Instruction/Report Form is generally provided to the crew for cross-checking against the load and trim sheet, though sometimes the crew are provided with a certificate stating that the baggage/cargo has been loaded in accordance with the load and trim sheet instructions.
With numerous mass and balance documentation formats and different industry procedures, it is very difficult to provide definitive details of how to conduct gross error checks. In line with the best industry practices, UK CAA guidance material - CAP 1009: Gross Error Checks provides information on how any significant discrepancies in the loading process can be identified and corrected before departure.
As with the load and trim sheet, there are a number of key entries on the Load Instruction/Report Form that must be checked for accuracy:
- Flight details (Routing, Flight number and Date)
- Aircraft type, variant and registration
- Distribution of hold loads (including baggage, cargo, ballast, spares, COMAT, and mail etc.)
- Void/nil fit positions
- Bags per ULD/hold
- Weight allocation to each compartment does not exceed limits
- Document edition number (if applicable)
Principal Hold Loading Risks
The principal risks associated with loading of aircraft holds are as follows:
- Holds are not loaded by the loading crew in accordance with the Loading Instructions provided - and the Load Instruction/Report Form is not amended to reflect these changes.
- Where the loading has been different to the original Loading/Report Form and the Loading/Report form is updated, the last minute change (LMC) has not been correctly applied to the original loadsheet calculations and checked for mass and balance limits.
- The load is not secured or restrained appropriately
- Unauthorised items are loaded (e.g. dangerous goods).
- Aircraft structure (or propeller blades if applicable) is damaged by unintended impact from mechanised loading equipment. Such impacts may go unnoticed by the loading team or in some cases is noticed but not reported. This may happen when the load team can see no apparent damage so consider reporting the impact unnecessary. Where the aircraft structure is formed using composite materials, all impacts must be reported. While evidence of significant damage to a metal structure is usually clearly visible, this is not necessarily true for composite materials. Although the skin may appear to be undamaged, the core of a composite structure may have deformed or have been significantly weakened.
Consequences of Mis-loading
- Loss of Control in flight
- Runway Excursion during take off or landing
- Aircraft Hold Damage during flight
Accidents and Incidents
The following events listed on SKYbrary are related to Cargo Loading:
- A124, Zaragoza Spain, 2010 (On 20 April 2010, the left wing of an Antonov Design Bureau An124-100 which was taxiing in to park after a night landing at Zaragoza under marshalling guidance was in collision with two successive lighting towers on the apron. Both towers and the left wingtip of the aircraft were damaged. The subsequent investigation attributed the collision to allocation of an unsuitable stand and lack of appropriate guidance markings.)
- A319 / UNKN, Stockholm Arlanda Sweden, 2011 (On 5 February 2011, an Airbus A319-100 being operated by Air Berlin on a passenger flight departing Stockholm inadvertently proceeded beyond the given clearance limit for runway 19R and although it subsequently stopped before runway entry had occurred, it was by then closer to high speed departing traffic than it should have been. There was no abrupt stop and none of the 103 occupants were injured.)
- A319, Ibiza Spain, 2016 (On 19 June 2016, an Airbus A320 failed to follow the clearly-specified and ground-marked self-positioning exit from a regularly used gate at Ibiza and its right wing tip collided with the airbridge, damaging both it and the aircraft. The Investigation found that the crew had attempted the necessary left turn using the Operator’s ‘One Engine Taxi Departure’ procedure using the left engine but then failed to follow the marked taxi guideline by a significant margin. It was noted that there had been no other such difficulties with the same departure in the previous four years it had been in use.)
- A319, London Heathrow UK, 2007 (On 12 February 2007, an Airbus A319-100 being operated by British Airways on a scheduled passenger flight into London Heathrow made unintended contact in normal daylight visibility with the stationary airbridge at the arrival gate. This followed an emergency stop made after seeing hand signals from ground staff whilst following SEGS indications which appeared to suggest that there was a further 5 metres to run to the correct parking position. There was no damage to the aircraft, only minimal damage to the airbridge and there were no injuries to the aircraft occupants or any other person)
- A320, Auckland New Zealand, 2017 (On 27 October 2017, an Airbus A320 returned to Auckland after advice from ATC that the right engine may have been affected by ingestion of FOD during engine start - a clipboard and paper left just inside the right hand engine by an employee of the airline’s ground handling contractor acting as the aircraft loading supervisor. The subsequent inspection found paper throughout the engine and minor damage to an engine fan blade and the fan case attrition liner. The Dispatcher overseeing the departure said she had seen the clipboard inside the engine but assumed it would be retrieved before departure.)
- A320, Dublin Ireland, 2017 (On 27 September 2017, an Airbus A320 being manoeuvred off the departure gate at Dublin by tug was being pulled forward when the tow bar shear pin broke and the tug driver lost control. The tug then collided with the right engine causing significant damage. The tug driver and assisting ground crew were not injured. The Investigation concluded that although the shear pin failure was not attributable to any particular cause, the relative severity of the outcome was probably increased by the wet surface, a forward slope on the ramp and fact that an engine start was in progress.)
- A320, Lisbon Portugal, 2015 (On 19 May 2015, an Airbus A319 crew attempted to taxi into a nose-in parking position at Lisbon despite the fact that the APIS, although switched on, was clearly malfunctioning whilst not displaying an unequivocal ‘STOP’. The aircraft continued 6 metres past the applicable apron ground marking by which time it had hit the airbridge. The marshaller in attendance to oversee the arrival did not signal the aircraft or manually select the APIS ‘STOP’ instruction. The APIS had failed to detect the dark-liveried aircraft and the non-display of a steady ‘STOP’ indication was independently attributed to a pre-existing system fault.)
- A320, London Heathrow UK, 2006 (On 26 June 2006, after an uneventful pre-flight pushback of a British Airways Airbus A320-200 at London Heathrow Airport, the aircraft started moving under its own power and, shortly afterwards, collided with the tractor that had just performed the pushback, damaging both the right engine and the tractor.)
- A321 / B734, Barcelona Spain, 2015 (On 25 November 2015, an Airbus A321 taxiing for departure at Barcelona was cleared across an active runway in front of an approaching Boeing 737 with landing clearance on the same runway by a Ground Controller unaware that the runway was active. On reaching the lit stop bar protecting the runway, the crew queried their clearance and were told to hold position. Noting that the event had occurred at the time of a routine twice-daily runway configuration change and two previous very similar events in 2012 and 2014, further safety recommendations on risk management of runway configuration change were made.)
- A321, Daegu South Korea, 2006 (On 21 February 2006, an Airbus A321-200 being operated by China Eastern on a scheduled passenger flight from Daegu to Shanghai Pudong failed to follow the marked taxiway centreline when taxiing for departure in normal daylight visibility and a wing tip impacted an adjacent building causing minor damage to both building and aircraft. None of the 166 occupants were injured.)
- A332, Karachi Pakistan, 2014 (On 4 October 2014, the fracture of a hydraulic hose during an A330-200 pushback at night at Karachi was followed by dense fumes in the form of hydraulic fluid mist filling the aircraft cabin and flight deck. After some delay, during which a delay in isolating the APU air bleed exacerbated the ingress of fumes, the aircraft was towed back onto stand and an emergency evacuation completed. During the return to stand, a PBE unit malfunctioned and caught fire when one of the cabin crew attempted to use it which prevented use of the exit adjacent to it for evacuation.)
- A332/A345, Khartoum Sudan, 2010 (On 30 September 2010, an A330-200 was about to take off from Khartoum at night in accordance with its clearance when signalling from a hand-held flashlight and a radio call from another aircraft led to this not taking place. The other (on-stand) aircraft crew had found that they had been hit by the A330 as it had taxied past en route to the runway. The Investigation found that although there was local awareness that taxiway use and the provision of surface markings at Khartoum did not ensure safe clearance between aircraft, this was not being communicated by NOTAM or ATIS.)
"Cargo Loading" is not in the list of possible values (Taxiway collision, On gate collision, Aircraft / Aircraft conflict, Aircraft / Person conflict, Aircraft / Vehicle conflict, Aircraft / Object or Structure conflict, ATC clearance error, Ground de/anti icing ineffective, Ground de/anti icing not available, Failure to De/anti Ice, Jet Blast / Prop wash, Surface Friction, Towed aircraft involved, Aircraft Push Back, Incorrect Parking Position, Airbridge Positioning, Both objects moving, Wingtip clearance, Centreline obscured, Accepted ATC clearance not followed, Surface Lighting control, Passenger Loading, Fuel Loading, Dangerous Goods, Engine Ground Running, Engine Powered Systems Test, No Flight Crew on Board, Charting Error, Passenger Aircraft Hold Loading, Cargo Aircraft Loading, Flt Deck/Ramp crew comms, Non-active runway take off/landing, Closed Runway take off/landing, Maintenance work in progress, Non Active Runway FOD, Ramp crew procedures, Taxiway Take Off/Landing) for this property.
- UK CAA CAP 1008 Last minute changes (LMC) - Guidance document, February 2014
- UK CAP 1009 Gross error checks - Guidance document, February 2014
- UK CAA CAP 1010 Ramp/ Aircraft Loading Operations Checklist, February 2014
- FAA AC 120-85A 'Air Cargo Operations', June 2015
- ISAGO Standards Manual 5th Edition, March 2016
- FAA SAFO on 'Cargo Restraint Strap Assemblies', July 2016
- FAA SAFO 17004: Cargo Retention Methods Using Pallets Straps, March 2017