If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user
Loading of Aircraft with Cargo
|Content control:||Air Pilots|
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:
- A332, Sydney Australia 2009 (On 4 July 2009, an Airbus A332 being operated by Jetstar Airways on a scheduled passenger flight from Sydney to Melbourne carried a 750 kg ULD which had been expressly rejected by the aircraft commander during the loading operation without flight crew awareness. There was no reported effect on aircraft handling during the flight.)
- AT43, Madang Papua New Guinea, 2013 (On 19 October 2013, the Captain of an ATR42 on a cargo flight taking off from Madang was unable to rotate the aircraft for take off and was forced to reject the take off from above V1. It was not possible to stop on the runway and the aircraft ended up semi submerged in a shallow creek beyond the airfield perimeter. The Investigation has established that the aircraft had not been loaded as instructed and as stated on the load and trim sheet, in particular in respect of the distribution of the load. The Investigation is continuing.)
- B190, vicinity Charlotte NC USA, 2003 (On 8 January 2003, a B190, operated by Air Midwest, crashed shortly after take off from Charlotte, NC, USA, following loss of pitch control during takeoff. The accident was attributed to incorrect rigging of the elevator control system compounded by the airplane being outside load and balance limitations.)
- B738, Dubai UAE, 2013 (On 6 December 2013, a Boeing 737-800 passenger aircraft was flown from Amman to Dubai out of revenue service with a quantity of 'live' boxed chemical oxygen generators on board as cargo without the awareness of the aircraft commander. The subsequent Investigation found that this was possible because of a wholesale failure of the aircraft operator to effectively oversee operational risk implicit in sub contracting heavy maintenance. As a result of the investigation, a previously unreported flight by the same operator in revenue service which had also carried live oxygen generators was disclosed.)
- B739, Singapore, 2013 (On 26 May 2013, about 20 minutes after arrival at Singapore for a turn round expected to last about an hour and with crew members on board, a Boeing 737-900 was suddenly rotated approximately 30 degrees about its main gear by a relatively modest wind gust and damaged by consequent impacts. The Investigation concluded that the movement had been due to the failure to follow manufacturer's guidance on both adequate chocking of the aircraft wheels and the order of hold loading. It was found that the Operator had not ensured that its ground handling agent at Singapore was properly instructed.)
- B744, Bagram Afghanistan, 2013 (On 29 April 2013, a Boeing 747-400 freighter departed controlled flight and impacted terrain shortly after taking off from Bagram and was destroyed by the impact and post crash fire and all occupants were killed. The Investigation found that a sudden and significant load shift had occurred soon after take off which damaged hydraulic systems Nos. 1 and 2 and the horizontal stabilizer drive mechanism components as well as moving the centre of gravity aft and out of the allowable flight envelope. The Load shift was attributed to the ineffective securing techniques employed.)
- B744, Gardermoen Norway, 2004 (On 21 September 2004, a Korean Air Boeing 747-400F experienced handling difficulties on take off due to the Centre of Gravity (CofG) being aft of the limit as a result of misloading.)
- B744, en-route, East China Sea, 2011 (On 28 July 2011, 50 minutes after take off from Incheon, the crew of an Asiana Boeing 747-400F declared an emergency advising a main deck fire and an intention to divert to Jeju. The effects of the rapidly escalating fire eventually made it impossible to retain control and the aircraft crashed into the sea. The Investigation concluded that the origin of the fire was two adjacent pallets towards the rear of the main deck which contained Dangerous Goods shipments including Lithium ion batteries and flammable substances and that the aircraft had broken apart in mid-air following the loss of control.)
- B763, Manchester UK, 1998 (On 25th November 1998, baggage containers on a B767, moved in flight causing damage to a cabin floor beam and damage to the standby system power supply cable causing electrical arcing. The aircraft landed safely at Manchester, UK, and the damage was only discovered during unloading.)
- DC3, vicinity Yellowknife Canada, 2013 (On 19 August 2013, a fire occurred in the right engine of a Douglas DC3-C on take off from Yellowknife. After engine shutdown, a right hand circuit was made in an attempt to land back on another runway but trees were struck and the aircraft crash-landed south of it. Emergency evacuation was successful. The Investigation found that a pre-existing cylinder fatigue crack had caused the engine failure/fire and that the propeller feathering pump had malfunctioned. It was found that an overweight take off had occurred and that various unsafe practices had persisted despite the regulatory approval of the Operator's SMS.)
- F27, vicinity Guernsey Channel Islands, 1999 (On 12 January 1999, control of a Fokker F27-600 was lost on approach to Guernsey Airport, Channel Islands, as a consequence of the aircraft being operated outside the load and balance limitations.)
- SF34, Kirkwall Orkney UK, 2003 (On 12 September 2003, a Saab 340B being operated by UK regional airline Loganair on a scheduled passenger flight from Aberdeen to Kirkwall experienced a loss of pitch control during landing at destination and the rear fuselage contacted the runway causing damage to the airframe. Once the aircraft had cleared the runway, some passengers and some of the hold baggage was removed before the aircraft was taxied to its parking position because of a suspicion that the aircraft might have been loaded contrary to the accepted load and trim sheet.)
- 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