thebigblue88

If you want to disconnect the Fly-By-Wire you can try moving the primary flight computer switch to DISCONNECT (the switch is next to the TAC) now it will effectively fly like a 737. You will lose a lot of features but it will now fly like a more conventional aircraft. The B777 Fly-By-Wire (FBW) system introduces some very new concepts to the art of flying while maintaining the traditional look, and to some extent the feel, of that experience. The B777 Pitch Trim System is unique in the commercial world and if used as intended will not only enhance the pilot’s enjoyment of this remarkable airplane but also reduce his or her workload. Some of the differences from conventional trim systems are not fully understood and the purpose of this paper is to expand on this important area. Throughout this paper it is assumed that the FBW system is operating in the Normal mode and that the pilot is flying manually. The main concept to grasp right from the start is that the pilot only needs to TRIM FOR SPEED CHANGES. Performing maneuvers at constant speed does not call for further change. Once trimmed for a speed, say a 250 kt departure, you can level off, climb, turn, and level off again without ever touching the trim switches. During a Go-around maneuver (which should be flown at a constant speed of Vref + 5 kts) there should be no need to re-trim; perform the maneuver by adjusting the pitch and when flying away at (the same) ‘bug speed’ the aircraft will still be trimmed for this condition. Engine out work makes no change to this concept! Similarly, on takeoff the Pitch Trim System follows the actual speed until stabilized. This means that if the pilot’s rotation is correct, stabilizing between V2 + 15 and V2 + 25 kts for two engines (or V2 and V2 + 15 kts for single engine); there is no need to trim until you change speed at flap retraction. The Pitch Trim System trims at a constant 10 kts per second throughout the flight speed range, unless utilizing the ‘blip’ to trim function when nearly trimmed. Remember from your basic flight training the idea of “Put the aircraft where you want it, then trim out the residual forces?’ Well, it works just as well in the B777 as it did in the light trainer aircraft. If you find yourself flying through the trimmer or constantly ‘blipping’ to find the trimmed condition then you are misusing the system. It is quite possible to put the aircraft directly in trim at a first attempt without using the ‘blip’ facility. The ‘blip’ facility is a difficult one to grasp, especially since there is no direct readout of Trim Reference Speed (TRS) or the 5 kt speed range band. Once the TRS is within 5 kts of ACTUAL speed a ‘blip’ will synchronize the TRS to ACTUAL speed. The ‘blip’ facility cannot sync to bug speed, unless actual and bug speed are co-incidental (again, put the aircraft where you want it, then trim out residual forces). The question is: How do you know when you’re within the 5 kt band? Well, you don’t precisely and this is where some confusion arises. Usually if you feel the aircraft is ‘almost’ in trim then you’ll be within ‘blip’ range. If not, a ‘blip’ will only move the TRS at the 10 kt per second rate, i.e., perhaps 1, 2, or 3 kts. This may or may not be enough to put the aircraft in trim; since if the 1, 2, or 3 kt move puts the TRS within 5 kts of actual speed the system will sync for you. If not then you have only moved the TRS a few kts towards the trimmed condition. By way of example: Previous trimmed speed 180 kts, now flying at 160 kts – It is possible to bring the aircraft back into trim with a 2 second trim input. If however, at first attempt, you achieved say 168 kts TRS a ‘blip’ might only put the TRS to 166 kts, i.e., still not in trim. More likely you might have achieved a TRS of 164 kts at first attempt, and then the next ‘blip’ would sync the trim system. Another important idea to grasp is that once trimmed for speed you should avoid ‘blipping’ the trim switches. At best you will achieve nothing, but you could actually put the aircraft out of trim. Since the TRS moves at a constant 10 kts per second, as mentioned above, the ‘blip’ you give to a trimmed aircraft moves the TRS away from the trimmed condition by ‘a few’ kts. If the TRS remains within 5 kts then the system will re-sync, however if your ‘blip’ was greater than ½ second the aircraft will then be out of trim. This is often observed on final approach, when pilots exacerbate speed and glideslope conflicts.