skybrary - aircraft load and trim

8/7/2019 SKYbrary - Aircraft Load and Trim

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Article Information

Category: Runway Excursion

Content source: SKYbrary

Content control: EUROCONTROL

RE

Tag(s)Overrun on Take Off

Overrun on Landing

Aircraft Load and Trim

Categories: Runway Excursion | Operational Issues | Loss of Control | Ground Operations

From SKYbrary Wiki

Contents

1 Description

2 Loading Procedures

3 Load and Trim Sheets

4 Departure Control Systems (DCS)

5 Manual Load sheets

6 Aircraft Commanders' Acceptance of Load and

Trim Sheets7 Electronic Flight Bag generation of Load and

Trim data

8 Provisional and Final Load Sheets

9 Risks arising from aircraft loading

10 Consequences of actual misloading or incorrect

input of load-related data

11 Related Articles

12 Further Reading

Description

It is crucial to aircraft safety in flight that it is loaded in such a way that the specified maximum allowable weights ar

not exceeded and that the centre of gravity as loaded will be and remain within the permitted flight envelope for all

stages of the intended flight. Once these conditions have been satisfied, it is equally crucial that the flight crew are

aware of the prevailing weight and centre of gravity so that they can set appropriate take off reference speeds,

trailing edge flap settings and pitch trim position so that rotation will be made at the right indicated airspeed and wil

have the desired effect of initiating a successful transition from ground to airborne to meet any restrictions imposed

by the TORA and whilst full control of the aircraft is retained. It is very important that aircraft baggage and freightload complies with the restrictions on carriage of dangerous goods.

Loading Procedures

It is essential that the Dispatcher or other official assigned responsibility for overseeing aircraft loading both specifi

the loading requirement correctly and has a reliable method by which they can be satisfied that their instructions

have been carried out as requested. Whilst modern methods are likely to use automated systems to determine the

seating options for passengers and the disposition of dead load between available loads, effective procedures and

compliance remain the only way of ensuring that what has been specified and passed to the aircraft commander as


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fact has actually been achieved. For Hold Loading, this is usually achieved by the completion of a Loading

Instruction Form (LIF) which is accepted by the designated loading supervisor and signed as complied with after

completion of the task and returned to the person who issued it as verification prior to that person presenting the

completed load and rim sheet to the aircraft commander. The human supervisory function must also have a reliable

means to satisfying themselves that the dangerous goods regulations and any special requirements for securing

unusual items in the holds or in the passenger cabin have been complied with.

Load and Trim SheetsThe traditional requirement, which dates from the days when all load and trim sheets were completed manually on

specific forms designed for use with each aircraft type, is as follows:

the completed document is presented to the aircraft commander

the aircraft commander checks that it is internally consistent by carrying out some simple cross checks of

input and calculated data for gross errors and,

if the cross checks are satisfactory, the commander formally accepts the load and trim sheet by means of a

signature on at least two copies, one being retained by the departure agent and the other by the flight crew.

The process with DCS is slightly different in that only the input data need be checked and the completed documen

may not necessarily be signed by the agent presenting it as he/she may have had no part in its preparation.

In both cases, however, the acceptance of an apparently correct load and trim sheet does not by its existence

provide any assurance that the aircraft has necessarily been loaded as stated.

Departure Control Systems (DCS)

Most Load and Trim Sheets used today in commercial air transport flown by multi crew aircraft are produced by

contracted Handling Agents by making flight-specific inputs to a proprietary DCS. There are a number ofcommercial DCS products available. Some are operated by large airlines for their own use and then also employed

to generate external user business. Others similar DCS are operated independently of any particular airline. Where

DCS systems are used, the data input and electronic generation of the load and trim sheet may be carried out at a

regional centre and merely printed off - together with corresponding Loading Instructions - by the aircraft operator

or the contracted handling agent employees.

Manual Load sheets

Manual Load sheets involve a pro forma calculation of MRW, MTOW and MLW whilst the centre of gravity is

located by marking the requisite aircraft operating weight (vertical scale) on a drop line located on a centre ofgravity index scale which forms the horizontal axis. If the position so found is within the areas shown as the

permitted safe flight envelope, then operation as loaded is possible.

Whilst manual preparation of load and trim sheets used to be the main method, they are now often used so

infrequently that recalling the necessary method for their completion can be challenging to ground staff who rarely

do it and are then presented with preparing one as an unexpected often time-pressured challenge. Many younger

pilots have never been used to either preparing a manual load and trim sheet or checking one for acceptance, and

this unfamiliarity significantly increases the risk of undetected errors with significant consequences.




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Aircraft Commanders' Acceptance of Load and Trim Sheets

It is a requirement that an aircraft commander has a copy of the completed load and trim sheet for their flight and is

given the opportunity to check and accept it by signature before ensuring that a copy is left at the point of departur

The aircraft commander is obliged to accept that the aircraft is loaded as stated in respect of the Hold Loading but

in respect of Passenger Cabin Loading it is usual for there to be a report from the senior cabin crew of the number

of passengers actually on board derived from a headcount after boarding has been completed.

Electronic Flight Bag generation of Load and Trim data

For some flights, especially but not only cargo flights, the flight crew have an EFB which they use to calculate

aircraft performance data which takes account of the completed load and trim sheet. They also use the EFB to

make the load and trim calculations themselves, so that once it has been checked, all that is required is that a copy

be left with the agent at the point of departure. Clearly, it is vital that a rigourous process of cross checking is

included in the preparation of such documentation.

Provisional and Final Load SheetsThe rise of DCS systems and the communication facility afforded by ACARS has allowed aircraft commanders to

be given substantially complete and correct loading documents with provisional status in plenty of time before

STD and final status documents with highlighted minor amendments to be generated as the aircraft leaves the gate

for acceptance via ACARS at any time before take off commences.

Risks arising from aircraft loading

The primary risks arise from the aircraft being set up for take off with pitch, trim and/or take off reference speed

which are not correct. This can arise in one of three ways:

The aircraft is not loaded in the way stated on the accepted load and trim sheet (any load sheet type)

The aircraft load and trim sheet uses correct input data but the output data is wrong (manual load sheets)

The flight crew apply the (correct) load and trim data incorrectly when using it to calculate pitch trim, or

reference speed data.

The hold load is not properly secured or contains prohibited or incorrectly packed items.

Consequences of actual misloading or incorrect input of load-

related dataEither actual misloading of an aircraft or incorrect use of correct load related data for aircraft systems set up can

severely affect aircraft control. Loss of Control may occur during an attempted take off or during subsequent flight

because either:

an attempt (usually inadvertent) is being made to operate the aircraft outside of the AFM limits, or

the actions of the flight crew to control the aircraft are ineffective because the aircraft is not in the condition o

load and or trim which is believed to prevail and/or has been used to set up key aircraft control parameters,

whether manually interpreted e.g Vr on the ASI or automatically taken from erroneous FMS inputs.




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Runway Excursion has been a regular result of errors of both these types in the past, whether or not an RTO has

been attempted.

Related Articles

For a more detailed discussion of the issues arising with hold and cabin loading, see Hold Loading and Passenger

Cabin Loading which also have links to reports of investigations into specific outcomes consequent upon hold or

cabin loading data being incorrectly calculated or applied.

Other articles of interest within SKYbrary include:

Takeoff Weight Entry Error and Fatigue (OGHFA SE)

Further Reading

Analysis of aircraft weight and balance related safety occurrences

(http://www.skybrary.aero/bookshelf/books/1149.pdf) - NLR, 2007.

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Categories: Runway Excursion | Operational Issues | Loss of Control | Ground Operations

This page was last modified on 16 January 2011, at 16:40.

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