767 Question

[Hobo]

Today I flew in a BA767 FCO-LHR - in seat 24A right at the trailing edge of the wing. I noticed that throughout flight the port inboard aileron was deflected up so its trailing edge was about 50-75mm above the faired position with the trailing edge of the retracted flaps and the rest of the wing. The starboard inboard aileron was deflected a similar amount down.

If this had been a one off, I would have put it down to a 'bent airframe', although it does, on its face, seem quite a large deflection to keep the A/C in trim.

But in January this year, I had occasion to fly in a similar seat from NRT to AKL on an ANZ 767 - approximately 11 hours. The inboard ailerons were deflected exactly as on today's BA flight.

So the questions:

Is this normal for the 767? If it is it seems a huge amount of fuel must be being used worldwide to facilitate flying in trim like this.

What is the trimming technique on the 767? I have not flown it but on the 737(200) which I have, the technique was to take any 'bent airframe' or turning tendency out with rudder trim so the ailerons were faired with the wing.

[The Dominican]

What is the trimming technique on the 767? I have not flown it but on the 737(200) which I have, the technique was to take any 'bent airframe' or turning tendency out with rudder trim so the ailerons were faired with the wing.

Same, some are just too lazy to be bothered with the position of the flight controls I guess:ugh:

[piratepete]

Its not normal but it is quite common.If you were at 24a on a brand-new 767 you will most likely see the inboard ailerons nicely faired, however on very old models its common that the control rigging has not been kept up thus items like AILERONS and SPEED BRAKES can be in an un-faired state.The action of re-rigging is quite a specialised skill, takes time and money and many second/third tier operators cant be bothered with it but yes it does cost a lot of fuel.

[EEngr]

But if the rigging is 'off', that would result in a discrepancy between the wheel position and the ailerons. Given an aircraft with a straight frame, the control surfaces being in a trimmed position would result in straight and level flight. But that's not what Hobo described. The control wheel would have to be held off center to achieve a faired trim given a rigging problem. Similar to an auto's steering wheel being out of line to hold the wheels straight ahead. But wheels straight would still result in a straight course.

There could be some other mis-adjustments at work here (in Hobo's case) to require ailerons set as observed. A flap on one side not fully retracted (symmetrical with its opposite) for example might require a compensating roll input to maintain level flight. Other aerodynamic asymmetries may account for this as well. Or a fat guy sitting on one side.;)

[Fratemate]

Same, some are just too lazy to be bothered with the position of the flight controls I guess

I don't really understand the assertion that some pilots are lazy because they don't check the position of the flight controls.

If you mean they haven't bothered to look at the control column and notice the displacement of the wheel then I'm in agreement. If you mean they haven't brought up the Status display and then trimmed using those indications then we disagree. I've seen a few pilots doing this and they think they're being very clever (especially as in all cases we've been in LNAV) but the aircraft ends up a complete mess. Sure, the controls look pretty on the Status page but the wheel ends up at some weird angle and totally contrary to Mr Boeing's technique, which I prefer to use. There is no requirement to check the position of the controls on the Status page and, quite the opposite, Boeing don't recommend it at all.

Just in case anyone is bored:

Recommended Rudder Trim Technique

This section describes two techniques for properly trimming the rudder. It is assumed that the airplane is properly rigged and in normal cruise. The primary technique uses rudder trim only to level the control wheel and is an acceptable and effective method for trimming the airplane. It is approximately equal to a minimum drag condition. This technique is usable for normal as well as many non-normal conditions. For some non-normal conditions, such as engine ailure, this technique is the preferred method and provides near minimum drag.
The alternate technique may provide a more accurate trim condition when the roll is caused by a roll imbalance. In addition, this technique outlines the steps to be taken if the primary trim technique results in an unacceptable bank angle or excessive rudder trim. The alternate technique uses both rudder and aileron trim to neutralize a rolling condition using the bank pointer as reference.
Note: Large trim requirements may indicate the need for maintenance and should be noted in the airplane log.

Drag Factors Due to Trim Technique
If the control wheel is displaced to the point of spoiler deflection a significant increase in aerodynamic drag results. Additionally, any rigging deviation that results in early spoiler actuation causes a significant increase in drag per unit of trim. These conditions result in increased fuel consumption. Small out of trim conditions affect fuel flow by less than 1%, if no spoilers are deflected.
Note: Aileron trim may be required for significant fuel imbalance, airplane damage, or flight control system malfunctions.


Primary Rudder Trim Technique
It is recommended that the autopilot remain engaged while accomplishing the primary rudder trim technique (using rudder trim only). After completing this technique, if the autopilot is disengaged, the airplane should maintain a constant heading.
The following steps define the primary rudder trim technique:
• set symmetrical thrust
• balance fuel if required
• ensure the autopilot is engaged in HDG SEL and stabilized for at least 30 seconds
• trim the rudder in the direction corresponding to the down (low) side of the control wheel until the control wheel indicates level. The indices on top of the control wheel should be used to ensure a level wheel condition.
The airplane is properly trimmed when the control wheel is level, (zero index). As speed, gross weight, or altitude change, trim requirements may also change. In a proper trim condition, there may be a slight forward slip (slight bank angle indicated on the bank pointer) and a slight deflection of the slip/skid indicator, which is acceptable.

Alternate Rudder Trim Technique
The alternate rudder trim technique is used if the primary trim technique results in an unacceptable bank angle, excessive rudder trim, or if a more accurate dual axis trim is required.
The following steps define the alternate rudder trim technique:
• set symmetrical thrust
• balance fuel if required
• verify rudder trim is zero
• ensure the autopilot is engaged in HDG SEL and stabilized for at least 30 seconds
• trim the rudder in the direction corresponding to the down (low) side of the control wheel until the bank indicates level (no bank angle indicated on the bank pointer). Apply rudder trim incrementally, allowing the bank to stabilize after each trim input. Large trim inputs are more difficult to coordinate. The airplane is properly trimmed when the bank angle on the bank pointer indicates zero. If the airplane is properly rigged, the control wheel should indicate approximately level. The resultant control wheel condition indicates the true aileron (roll) trim of the airplane being used by the autopilot.
After completing the alternate rudder trim technique, if the autopilot is disengaged the airplane may have a rolling tendency. Hold the wings level using the bank pointer as reference. Trim out any control wheel forces using the aileron trim switches. If properly trimmed, the airplane holds a constant heading and the aileron trim reading on the wheel/column agrees with what was seen while the autopilot was engaged. Aileron trim inputs require additional time and should be accomplished prior to final approach.

[The Dominican]

Ok, so we agree then! Add to my assertion of the laziness of some, the fact that they trim once after they level off and don't bother to notice the trim requirement changes as the A/C gets lighter:ugh: