Trim The Aircraft - One potential consequence of an error in loading or data entry is tailstrike on take off. This will usually lead to fuel dumping and a return to the take-off airfield, without pressurizing the cabin and is not career enhancing for any of the pilots, even the relief crew.
Even more serious, Runway Excursion has been a regular result of errors of both these types in the past, whether or not an Rejected Take Off has been attempted. Given the potential severity of a mistake in loading, of transferring erroneous weight and balance figures however derived, of entering erroneous data into the aircraft management systems (FMS) or miss-setting ASI speed bugs, both pilots should always carry out Gross Error checks.
Trim The Aircraft
Seniority does not imbue data entry infallibility! Amongst other checks, it is vital to confirm that the Zero Fuel Weight is sensible and then that the indicated Take-Off Weight is as expected. There is a maximum allowable change to the number of passengers or hold load as an LMC, which will be specified in the individual operator's Operations Manual for each aircraft type.
Departure Control Systems Dcs
Operators must also specify a similar rule for changes to the balance condition, to be defined in index units. If there are changes to fuel quantities and/or locations, the weight and balance figures should be fully recalculated and new documentation produced because of the significance in terms of the aircraft mass and balance condition.
However, some operators may permit fuel LMCs for lesser quantities, so fuel mass and index data must be made available and should be checked. It is a legal requirement and crucial to the safety and structural integrity of an aircraft that it is loaded in such a way that the specified maximum allowable weights are not exceeded and that the center of gravity as loaded will be within the permitted flight envelope and remain
so for the entirety of the intended operation. Once these conditions have been satisfied, it is equally crucial that the flight crew are aware of the prevailing weight and center of gravity so that they can set aircraft equipments appropriately;
these include take off reference speeds, slat/flap position, and pitch trim or stabilizer position. This is important to ensure that the aircraft will achieve published certified performance and that the aircraft retains expected stability and control characteristics.
Manual Load Sheets
It is also very important that aircraft baggage and freight load comply with the restrictions on the carriage of dangerous goods. By definition, to "trim" an aircraft is to adjust the aerodynamic forces on the control surfaces so that the aircraft maintains the set attitude without any control input.
While all axes of rotation are affected by aerodynamic forces, not all aircraft types are capable of being trimmed in all three axes. Virtually all aircraft designs incorporate some form of pitch axis trim and most have provisions of some description for trimming in the yaw axis.
Roll axis trim exists on many aircraft but it is the least frequently encountered installation of the three. There are several different types of trim systems in use and more than one type may be found on a given aircraft.
Most Load and Trim Sheets used today in commercial air transport operations by multi-crew aircraft are produced by contracted Handling Agents who input flight-specific data into a proprietary DCS. There are a number of commercial DCS products available.
Loading Procedures
Some are operated by large airlines for their own use and then also employed to generate external user business. Other similar DCS are operated independently of any particular airline. Where DCS are used, the data input and electronic generation of the load and trim sheet may be carried out at a regional center and merely printed off, together with the corresponding LIF, by the aircraft operator or the contracted handling agent employees.
Note that DCS will only produce output data as accurate as the inputs, so it is important to guard against input errors. The torque from the tail TT is equal to the lift of the tail T times the distance from the cg to the center of pressure of the tail dt.
The lift of the wing and the lift of the tail are both forces and forces are vector quantities which have both a magnitude and a direction. We must include a minus sign on the lift of the tail because the direction of this force is negative.
On 30 May 2019, a DHC8-200 departing from Nuuk could not be rotated at the calculated speed even using full aft back pressure and the takeoff was rejected with the aircraft coming to a stop with 50 meters of the 950 meter long dry runway remaining.
Tww*Dw
The initial Investigation focus was on a potential airworthiness cause associated with the flight control system but it was eventually found that the actual weights of both passengers and cabin baggage exceeded standard weight assumptions with the excess also resulting in the aircraft center of gravity being outside the range
certified for safe flight. 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.
On 16 April 2014, a pre-flight concern about whether a Boeing 777-200ER about to depart Singapore had been overfueled was resolved by a manual check but an en-route fuel system alert led to close monitoring of the fuel system.
When a divergent discrepancy between the two independent fuel remaining sources became apparent, an uneventful precautionary air turnback was made and overfueling subsequently confirmed. The Investigation found that a system fault had caused overfuelling and that the manual check carried out to confirm the actual fuel load had failed to detect it because it had not been performed correctly.
Consequences Of Actual Misloading Or Incorrect Input Of Load-Related Data
Either actual mis-loading of an aircraft or incorrect use of correct load related data for aircraft systems set up can severely affect aircraft performance, stability and control. Loss of Control may occur during an attempted take off or during subsequent flight because either:
On the Xbox One controller you can change trim by pressing the Y button and up or down on the d-pad. If the plane is going upwards automatically you'll want to press Y + up on the d-pad to balance it out.
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On the other hand, if the plane tends to be drifting downwards you will want to do the opposite. If any LMC occurs after the completion of the mass and balance documentation, it must be brought to the attention of the captain and clearly entered on the documentation.
The captain should amend the mass and balance sheet, but it is essential that it is recorded on the copy kept at the point of departure. 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.
How To Level Plane / Change Trim With Controller
There was no reported effect on aircraft handling during the flight. On most aircraft, the center of gravity of the airplane is located near the center of pressure of the wing. If the center of pressure of the wing is aft of the center of gravity, its lift produces a counter-clockwise rotation about the cg.
The center of pressure for the elevator is aft of the center of gravity for the airliner shown in the figure. A positive lift force from the tail produces a counter-clockwise rotation about the cg. To trim the aircraft it is necessary to balance the torques produced by the wing and the tail.
But since both rotations are counter-clockwise, it is impossible to balance the two rotations to produce no rotation. However, if the tail lift is negative it then produces a clockwise rotation about the cg which can balance the wing rotation.
On 17 December 2017, it was discovered after completion of an Airbus A330-300 passenger flight from Sydney to Bejing that freight loading had not been correctly documented on the load and trim sheet presented to and accepted by the Captain and as a result, the aircraft
Vector Sum
had exceeded its certified MTOW on departure. The Investigation found that the overload finding had not been promptly reported or its safety significance appreciated, that the error had its origin in related verbal communications during loading and noted that the aircraft operator had since made a series of improvements to its freight loading procedures.
On 7 December 2003, a Boeing 737-800 being operated by SAS on a passenger charter flight from Salzburg, Austria to Stockholm Arlanda with an intermediate stop at Goteborg made a high speed rejected take off during the departure from Goteborg because of an un-commanded
premature rotation. There were no injuries to any occupants and no damage to the aircraft which taxied back to the gate. The total lift of the aircraft is the vector sum of the wing lift and the tail lift.
For the airliner, the total lift is less than the wing lift; for the Wright brothers, the total lift is greater than the wing lift. The added lift was important for the Wright brothers because their aircraft had a very small engine and flew at low speeds (35 mph).
Vector Quantities
Since lift depends on the square of the velocity, it is hard to generate enough lift for flight at such low speeds. On 20 February 2014, an ATR 72-600 crew mishandled their response to an intended airspeed adjustment while using VS mode during descent to Sydney and an upset involving opposite control inputs from the pilots caused an elevator disconnect.
The senior cabin attendant sustained a serious injury. After recovery of control, the flight was completed without further incident. Post flight inspection did not discover damage to the aircraft which exceeded limit and ultimate loads on the stabilizers and the aircraft remained in service for a further five days until it was grounded for replacement of both horizontal and vertical stabilizers.
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.
Load And Trim Sheets
On 23 July 2015, an ATR72-600 crew suspected their aircraft was unduly tail heavy in flight. After the flight they found that all passenger baggage had been loaded in the aft hold whereas the load sheet indicated that it was all in the forward hold.
The Investigation found that the person responsible for holding loading as specified had failed to do so and that this failure had not been detected by the supervising Dispatcher who had certified the loadsheet presented to the aircraft Captain.
Similar loading errors, albeit all corrected prior to flight, were found by the Operator to be not uncommon. The torque equation, as written here, is a vector equation. All of the quantities are vector quantities having a magnitude and a direction.
If the distances are both positive (same side of the center of gravity), then the direction of the tail force must be different than the direction of the wing force to produce no net torque or rotation.
Adjustment Of The Last Minute Changes Lmc
However, if the distance to the tail were negative, then the lift of the tail could be positive and there would be no net torque. A negative distance to the tail would imply that the tail is on the front of the aircraft, ahead of the center of gravity.
A tail at the front of the aircraft is called a canard and was the configuration first used by the Wright brothers. 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.
For a more detailed discussion of the issues arising with hold and cabin loading, see Loading of Aircraft with Cargo 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.
Electronic Flight Bag Generation Of Load And Trim Data
Once you've mastered taking off in Microsoft Flight Simulator once you get into the sky you'll have some other things to manage as well. One of the most important things to get a handle on is trim.
Trim allows you to level your plane so that you aren't constantly needing to center, allowing you to effectively fly in a straight line while the plane is leveled. There are many times where you'll notice that you might be fighting with the plane to stop climbing or descending.
This is because you need to add or remove trim. Mastering trim will allow you to fly smoothly and actually enjoy the ride. The traditional method for ensuring load and trim compliance dates from the days when all load and trim sheets were completed manually on specific forms designed for use with each aircraft type, and is as follows:
As described on the forces slide, the aircraft lift is the sum of the lift of all of the parts of the airplane and acts through the aircraft center of pressure. Each part of the aircraft has its own lift component and its own center of pressure.
Fuel Loading And Distribution
The major part of the lift comes from the wings, but the horizontal stabilizer and elevator also produce lift which can be varied to maneuver the aircraft. It is often necessary to adjust the load sheet after completion.
These adjustments are called last minute changes (LMC). The LMC process is a way to enter late alterations/updates to a final manual or electronically produced load sheet, without requiring revisions to the main body or the preparation of a new document.
Guidance material on the LMC is made available by the UK CAA: CAP 1008 Last minute changes (LMC). On 12 January 2003, a Boeing 737-800 being operated by Dutch airline Transavia on a passenger charter flight initially going from Rotterdam to Maastrict-Aachen was obliged to reject its take off on Runway 24 at Rotterdam after it pitched nose-up just after take
-off thrust had been selected. The pitch up movement only stopped when the aft fuselage and the tailskid assembly contacted the runway and only when the flight crew rejected the take-off did the aircraft nose gear regain ground contact.
Provisional And Final Load Sheets
The aircraft was damaged and unfit for flight but able to taxi back to the terminal to allow the uninjured passengers to disembark. On 4 August 2018, a Junkers Ju-52 making a low level sightseeing flight through the Swiss Alps crashed killing all 20 occupants after control was lost when it stalled after encountering unexceptional windshear.
The Investigation found that the pilots had created the conditions which led to the stall and then were unable to recover from it and concluded that the accident was a direct consequence of their risky behavior.
It found that such behavior was common at the operator, that the operator was being managed without any regard to operational risk and that safety regulatory oversight had been systemically deficient. For some flights, especially but not only cargo flights, the flight crew have an electronic flight bag (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.
Center Of Gravity Cg
Clearly, it is vital that a rigorous process of cross-checking is included in the preparation of such documentation to avoid input errors. Crosschecking does not mean simply repeating the numbers selected/presented but also confirming that they make sense in relation to the actual situation.
Let us look carefully at the torques produced by the wing and the tail. The torque from the wing TW is equal to the lift of the wing W times the distance from the cg to the center of pressure of the wing dw.
The DCS (Departure Control Systems) process is slightly different in that only the input data needs to be checked and the completed document may not necessarily be signed by the agent presenting it, as he/she may have had no part in its preparation.
Many swept wing jet transport aircraft use fuel distribution to optimize the center of gravity in cruise to reduce fuel burn. This is achieved by keeping the C of G towards the aft limits of the envelope by utilizing outboard wing, aft body or horizontal stabilizer fuel tanks.
Aircraft Commanders Acceptance Of Load And Trim Sheets
It is the aircraft commander's responsibility to ensure that the fuel load prior to takeoff is correctly distributed and reflected on the load/trim sheet and maintained within the prescribed limits for the remainder of the flight.
DCS and the communication facility afforded by ACARS (Aircraft Communicaitons Addressing and Reporting System) has allowed aircraft commanders to be given substantially complete and correct loading documents with 'provisional' status in plenty of time before STD;
'final' status documents with highlighted minor amendments (also known as Last Minute Changes - LMC) can be generated as the aircraft leaves the gate for acceptance via ACARS at any time before take-off commences. The average location of the weight of the aircraft is the center of gravity (cg).
Any force acting at some distance from the cg produces a torque about the cg. Torque is defined to be the product of the force times the distance. A torque is a "twisting force" that produces rotations of an object.
In flight, during maneuvers, an airplane rotates about its cg. But when the aircraft is not maneuvering, we want the rotation about the cg to be zero. When there is no rotation about the cg the aircraft is said to be trimmed.
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