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737-800 is hard to rotate

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    #1

    737-800 is hard to rotate

    I'm completely new to the 737 and relatively new to airliners that are this detailed, so please forgive me if this is a silly question.

    As the title says, the 738 feels weirdly difficult to get in the air. I'm having the aircraft calculate V speeds and trim for me as I go through all of the PERF INIT setup, so I don't think speed is the issue. It feels as if the trim is pitched lower than it should be, but I'm not sure why this would be since I'm setting the trim to whatever is calculated in the FMC. Maybe I'm just not used to the 738 yet, and it needs a little more convincing than other aircraft, but I figured I'd ask if it's possible that I'm messing something up.

    Thanks - Alex Smith
    Tags: 737, msfs
    #2
    Did you set the trim in the aircraft to what the FMC showed on the Takeoff page?

    Also, from your wording, the FMC does NOT "set up the Vspeeds and trim" for you. It calculates them. You have to set V2 in the FMC and set the trim in the aircraft.
    Mark "Crabby" Crabtree AAL311 | PHL
    I7-9700KF | 2070 Super | Honeycomb Alpha/Bravo | MFG Crosswind

    Comment

      #3
      Originally posted by Crabby View Post
      Did you set the trim in the aircraft to what the FMC showed on the Takeoff page?

      Also, from your wording, the FMC does NOT "set up the Vspeeds and trim" for you. It calculates them. You have to set V2 in the FMC and set the trim in the aircraft.
      Yes, I’m setting the trim wheel based on the trim it calculates. I’m also accepting the V speeds that it calculates for me.

      Alex Smith

      Comment

        #4
        I agree with Alex. The 738 requires considerable amount of up elevator to start rotating. Could be true to life, but it seems like you really need to pull a lot. Once airborne the trim seems correct for the config and weight, but the initial force required seems high.
        Tero Partanen

        Comment

          #5
          https://youtu.be/xxBvsq44GM0
          Tim Smith

          Comment

            #6
            Originally posted by TimS View Post
            https://youtu.be/xxBvsq44GM0
            What is your point?
            Tero Partanen

            Comment

              #7
              The 737-800 specifically is quite a special aircraft to rotate. The reason is that the elevator enters the turbulence from the wings when the nose is approx 8° up and leaves it again at approx 10° pitch. This is due to the lengh of the airplane and requires the pilot to amand for during rotation.
              Initially you need to pull a bit to make the nose rise, once the nose starts coming up you need to adapt for the difference between the trim calculated from your loadsheet and the actual trim state of the plane (not every pax and bag weight exactly what is on the loadsheet which uses average values, so your real trimstate will not be exact for the conditions). Also take into account that takeoff trim is calculated for single engine operation in V2+10 conditions, so it doens't even aim for perfect dual engine conditions.
              Once you adapted for that difference in trim you will approach the elevator deadband already. At 8° pitch you loose quite a bit of elevator effectiveness for which you'll need to adjust by pulling back stronger. At 10° you leave the deadband and your elevator becomes more effective again so you need to relax your control column again a bit to maintain a constant rate of rotation.

              All of that happens while you're flying a plane which has only 50cm of tailclearance with a flap 5 takeoff and even just 30cm on a flap 1 takeoff and that's in ideal conditions.

              So yes, I fully agree with the OPs original statement that the 737-800 is "hard to rotate". In fact it takes the whole type rating, plus base training plus 80 sectors of linetraining and then another some 500 hours or so until most cadets are fully accustomed to rotating the plane.
              • Likes 2

              Comment

                #8
                Emi I think the point was simply that the force/ amount of up elevator to start rotation seems excessive
                Tero Partanen

                Comment

                  #9
                  Originally posted by teropart View Post
                  Emi I think the point was simply that the force/ amount of up elevator to start rotation seems excessive
                  What sensitivity setting are you using in pitch? The default MSFS means you need more pitch input for the required elevator position. Try setting it to zero, which gives a linear response. I find that much better.

                  Comment

                    #10
                    This is basically impossible to simulate. Everyone has a different controller. Some people are using XBOX controllers, some are using cheap joysticks and some are using high end winwing sticks... They're all crap when compared to the real thing so you just need to get used to how it works with your own controller.

                    Like Emi said the 737-800 is a "special" airplane. It's longer than the initial design accounted for (737-100). In the real airplane we have to be very careful with how we rotate because a tailstrike is incredibly easy to do. In the 757 for example I could pull the yoke like a hooligan and the airplane would start flying long before the tail came close to hitting the ground. So it's a good thing that your controller is requiring a lot of input to start rotation. Just get used to your controller and look for consistency.
                    Last edited by Aeromar; Yesterday, 12:36.
                    Omar Josef
                    737 FO
                    757/767 rated
                    Spain
                    • Likes 5

                    Comment

                      #11
                      Thanks for the responses everybody. I still feel like the aircraft almost refuses to pitch up for at least a couple of seconds after I hit my rotation speed, and I don’t think that should be the case. It’s good to know that the aircraft is a bit unique with regards to rotation, so I’ll try just being more forceful initially next time.

                      Alex Smith

                      Comment

                        #12
                        Originally posted by AerMingus View Post
                        Thanks for the responses everybody. I still feel like the aircraft almost refuses to pitch up for at least a couple of seconds after I hit my rotation speed, and I don’t think that should be the case. It’s good to know that the aircraft is a bit unique with regards to rotation, so I’ll try just being more forceful initially next time.

                        Alex Smith
                        You are right in that there is little delay when commanding pitch nose up and the nose actually pitching up. What you see is probably due to lack of pitch authority. Like Kevin, my pitch and roll response curves are linear without null zones using a Thrustmaster Warthog HOTAS. I have been flying the PMDG product for so long that rotation is basically just muscle memory but I'm probably commanding pitch up at about half full deflection. I always use the HUD if available because it gives me the tail strike symbol that is to be avoided. Initial rotation is about 8 deg NU until clear (tail strike symbol disappears) and then pitch increases to 15 deg NU until V2+20 then additional pitch up to maintain that speed until acceleration height. Takeoff's are a string of events.
                        Dan Downs KCRP
                        i7-10700K 32GB 3600MHz 3080Ti
                        • Likes 1

                        Comment

                          #13
                          Just messed around with it during a few take-offs, and I think it was simply that I severely underestimated the amount I’d have to pull. Sharply pulling back on the stick and then slowly relaxing it seems to get it off the ground in a more timely manner without a tail strike. I guess the 738 is unique, and it just takes more convincing than other aircraft that I’m used to.

                          Thanks again for the replies; they’ve been very informative. - Alex Smith

                          Comment

                            #14
                            Originally posted by AerMingus View Post
                            Just messed around with it during a few take-offs, and I think it was simply that I severely underestimated the amount I’d have to pull. Sharply pulling back on the stick and then slowly relaxing it seems to get it off the ground in a more timely manner without a tail strike. I guess the 738 is unique, and it just takes more convincing than other aircraft that I’m used to.

                            Thanks again for the replies; they’ve been very informative. - Alex Smith
                            Ah, from what you wrote there it now appears that you have wrong expectations on how airplanes behave. You have to realize that when you're rotating you're not yet at a speed where the airplane is fully responsive in pitch. Of course it requires a lot of elevator deflection to raise the nose at 140kts as opposed to 220kts. This isn't something completely unique to the 737. When in flight high and fast the amount that we move the control column to cause a pitch change is a lot smaller than on rotation or even at landing speeds.
                            Omar Josef
                            737 FO
                            757/767 rated
                            Spain
                            • Likes 1

                            Comment

                              #15
                              Originally posted by AerMingus View Post
                              Just messed around with it during a few take-offs, and I think it was simply that I severely underestimated the amount I’d have to pull. Sharply pulling back on the stick and then slowly relaxing it seems to get it off the ground in a more timely manner without a tail strike. I guess the 738 is unique, and it just takes more convincing than other aircraft that I’m used to.

                              Thanks again for the replies; they’ve been very informative. - Alex Smith
                              Just to be sure, Vr is the speed where you - initiate - the rotation, it's not the speed where the nose needs to come off the ground. Be gentle, don't force it up.
                              You're looking for 2-2.5°/sec during rotation, not more. Yank it up and your tail hooks up with the asphalt. And soon thereafter you will hook up with the chief pilot.

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