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Engine Failure Behavior

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    Engine Failure Behavior

    Hi,

    With TAC off and a V1 cut, seems that I only need rudder input on the ground.

    1. I wasn't able to maintain ground track even with full rudder input.
    2. Once in the air, with T/O thrust, the aircraft flies normally at rudder neutral and almost aileron neutral.

    Seems not correctly modelled in my opinion.

    Can anyone verify that happens to you as well, or just my settings?

    Philip Kang

    #2
    I'm not following you Philip. To me, a V1 cut means a RTO and thrust for both engines should be retarded to idle. Once in the air following a V1 cut doesn't make sense to me.
    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 2080Ti

    Comment


      #3
      Originally posted by DDowns View Post
      I'm not following you Philip. To me, a V1 cut means a RTO and thrust for both engines should be retarded to idle. Once in the air following a V1 cut doesn't make sense to me.
      A V1 cut is an engine failure at V1 (on the ground), takeoff continued. If an engine fails at V1, by definition can’t be an RTO. The term “V1 cut” is commonly known in the professional pilot realm and practiced hundreds of time.
      Rafael Cordoves

      Comment


        #4
        Originally posted by Icaruss View Post

        A V1 cut is an engine failure at V1 (on the ground), takeoff continued. If an engine fails at V1, by definition can’t be an RTO. The term “V1 cut” is commonly known in the professional pilot realm and practiced hundreds of time.
        Got it.... however, the FAA defines V1 as the maximum speed at which the rejected takeoff maneuver can be initiated and the airplane stopped within the remaining field length... (FAA Pilots Takeoff Safety brochure). In that context there is an obvious ambiguity. I've got decades of actual non-jet experience so there are areas where I might miss the language of such seasoned pilots as yourself.

        I'm not aware of any PMDG product that provides a realistic simulation of any flight condition after a failure. Stalls: Nope. OEI: Nope. Fires: Nope. Gear Failure: Nope.

        It is possible to "cut" one engine at or below V1 and a fairly realistic RTO will be simulated.
        Dan Downs KCRP
        i7-10700K 32GB 3600MHz 2080Ti

        Comment


          #5
          Originally posted by DDowns View Post

          Got it.... however, the FAA defines V1 as the maximum speed at which the rejected takeoff maneuver can be initiated and the airplane stopped within the remaining field length... (FAA Pilots Takeoff Safety brochure). In that context there is an obvious ambiguity. I've got decades of actual non-jet experience so there are areas where I might miss the language of such seasoned pilots as yourself.

          I'm not aware of any PMDG product that provides a realistic simulation of any flight condition after a failure. Stalls: Nope. OEI: Nope. Fires: Nope. Gear Failure: Nope.

          It is possible to "cut" one engine at or below V1 and a fairly realistic RTO will be simulated.
          Sort of agree. I’m very familiar with this as I work on certifying airplanes. The FAA changed the definition somewhat, however V1 is the last speed where a decision must be made. An engine fails at V1, by the time a pilot reacts, the aircraft will be way past it and flying.

          In fact, as a test pilot when we fail the engine that’s called Vef (Vevent) a second later V1 is determined and the aircraft does flying.
          Rafael Cordoves

          Comment


            #6
            Performance settings are important. Part of the formula for picking a takeoff thrust setting is controllability. Why in some scenarios, when you get to the thrust reduction part, you actually get a thrust increase.
            We use Aerodata for our performance selections.
            If after V1 you have an engine failure, you are going. If you can't maintain directional control with full rudder input and flying at V2, you must reduce thrust. In the 121 world, the thrust setting already accounts for this. In the flight sim world, did you really properly plan for it?
            William Holland

            Comment


              #7
              Originally posted by wjh308 View Post
              Performance settings are important. Part of the formula for picking a takeoff thrust setting is controllability. Why in some scenarios, when you get to the thrust reduction part, you actually get a thrust increase.
              We use Aerodata for our performance selections.
              If after V1 you have an engine failure, you are going. If you can't maintain directional control with full rudder input and flying at V2, you must reduce thrust. In the 121 world, the thrust setting already accounts for this. In the flight sim world, did you really properly plan for it?
              There is no thrust reduction when flying at V2 if directional control can’t be maintained with full rudder deflection like you stated. V2 takes into account Vmc, well technically speaking V2 is never less than V2min and V2min is required to be greater than 1.1 Vmc. So, controllability is not in question if proper speeds and control inputs are applied.

              What you might be thinking is flying close to or below Vmc, in which case yes, reduce power and increase airspeed.

              Reducing thrust during these segments climbs is completely the wrong thing to do when flying at the proper V2 speed, not sure where you got your source.
              Rafael Cordoves

              Comment


                #8
                Originally posted by Icaruss View Post

                There is no thrust reduction when flying at V2 if directional control can’t be maintained with full rudder deflection like you stated. V2 takes into account Vmc, well technically speaking V2 is never less than V2min and V2min is required to be greater than 1.1 Vmc. So, controllability is not in question if proper speeds and control inputs are applied.

                What you might be thinking is flying close to or below Vmc, in which case yes, reduce power and increase airspeed.

                Reducing thrust during these segments climbs is completely the wrong thing to do when flying at the proper V2 speed, not sure where you got your source.
                You just misunderstood me. You're assuming an engine was lost during my example. I was assuming an engine wasn't lost.
                William Holland

                Comment


                  #9
                  Originally posted by Icaruss View Post

                  There is no thrust reduction when flying at V2 if directional control can’t be maintained with full rudder deflection like you stated. V2 takes into account Vmc, well technically speaking V2 is never less than V2min and V2min is required to be greater than 1.1 Vmc. So, controllability is not in question if proper speeds and control inputs are applied.

                  What you might be thinking is flying close to or below Vmc, in which case yes, reduce power and increase airspeed.

                  Reducing thrust during these segments climbs is completely the wrong thing to do when flying at the proper V2 speed, not sure where you got your source.
                  Yup. I would never reduce the thrust when having an engine out. V2 to V2 + 15 is the speed to fly. By definition, if the performance is setup correctly, V2 must be above Vmca.

                  Vmcg >= V1 >= Vmca > Vmca * 1.05 >= Vr

                  The only scenario requiring a thrust reduction is at TO-1 and TO-2, you moved the thrust lever beyond the THR REF setting, then you may have control problem. That said, moving the thrust lever beyond THR REF at derated thrust is not a proper procedure anyway (unless in an absolute emergency situation).

                  If both engines are running, there won't be any directional control problem. The speed to fly is V2 + 15 to V2 + 25.

                  Comment


                    #10
                    The only scenario requiring a thrust reduction is at TO-1 and TO-2, you moved the thrust lever beyond the THR REF setting, then you may have control problem. That said, moving the thrust lever beyond THR REF at derated thrust is not a proper procedure anyway (unless in an absolute emergency situation).
                    Don't know if I got it from the FCTM or the FCOM but I think I saw somewhere that if you have the feeling to be underpowered, you can push TOGA again to have full power available even though it shouldn't be needed as the derated takeoff thrust normally takes into account engine out.

                    I would not understand why this would cause controllability issues unless you overspeed the engines (which is normally impossible with EEC working correctly).


                    Noah Scohy

                    Comment


                      #11
                      Originally posted by wjh308 View Post

                      You just misunderstood me. You're assuming an engine was lost during my example. I was assuming an engine wasn't lost.
                      Ok, well after you made the statement “If after V1 you have an engine failure” it sounded to me you were.
                      Rafael Cordoves

                      Comment


                        #12
                        Originally posted by pshkong View Post

                        Yup. I would never reduce the thrust when having an engine out. V2 to V2 + 15 is the speed to fly. By definition, if the performance is setup correctly, V2 must be above Vmca.

                        Vmcg >= V1 >= Vmca > Vmca * 1.05 >= Vr

                        The only scenario requiring a thrust reduction is at TO-1 and TO-2, you moved the thrust lever beyond the THR REF setting, then you may have control problem. That said, moving the thrust lever beyond THR REF at derated thrust is not a proper procedure anyway (unless in an absolute emergency situation).

                        If both engines are running, there won't be any directional control problem. The speed to fly is V2 + 15 to V2 + 25.
                        Certification is done at max power during segment climbs. There will be no requirements to reduce power during the climb and controllability is not an issue when proper procedures are flown.
                        Rafael Cordoves

                        Comment


                          #13
                          Originally posted by 777-300ER flyer View Post

                          Don't know if I got it from the FCTM or the FCOM but I think I saw somewhere that if you have the feeling to be underpowered, you can push TOGA again to have full power available even though it shouldn't be needed as the derated takeoff thrust normally takes into account engine out.

                          I would not understand why this would cause controllability issues unless you overspeed the engines (which is normally impossible with EEC working correctly).

                          This is because of the way how performance is calculated.

                          For TO-1 and TO-2 derates, the performance (hence Vmcg and Vmca) is calculated based on TO-1 and TO-2 thrust rating. If you move the thrust lever beyond the THR REF position, your Vmcg and Vmcg are no longer valid.

                          For assumed temperature method, i.e. D-TO, D-TO-1, D-TO-2, the performance is calculated based on TO, TO-1, TO-2 respectively. Pushing TOGA will remove the ATM thrust reduction and bring the thrust to TO, TO-1, TO-2 respectively. Vmcg and Vmca are still valid.

                          THR REF (green arrows) always at or below the maximum N1 (amber line, max rated thrust for current atmospheric condition) and N1 limit (red line, engine overspeed limit).

                          Comment


                            #14
                            This is because of the way how performance is calculated.

                            For TO-1 and TO-2 derates, the performance (hence Vmcg and Vmca) is calculated based on TO-1 and TO-2 thrust rating. If you move the thrust lever beyond the THR REF position, your Vmcg and Vmcg are no longer valid.

                            For assumed temperature method, i.e. D-TO, D-TO-1, D-TO-2, the performance is calculated based on TO, TO-1, TO-2 respectively. Pushing TOGA will remove the ATM thrust reduction and bring the thrust to TO, TO-1, TO-2 respectively. Vmcg and Vmca are still valid.
                            Alright so if I understood correctly, increasing the thrust from let's say TO-2 to TO with only one engine operating could cause controllability issue only if you are flying at V2 (and not above) because speeds were calculated based on TO's Vmcg and Vmca and not TO-2's Vmcg/Vmca.

                            Now if you accelerate, you will fly above TO's Vmcg and Vmca wouldn't you?

                            Now I understand that it's not a normal procedure but what I saw in the FCTM was probably in the case of an absolute emergency as you said earlier.

                            Noah Scohy

                            Comment


                              #15
                              Your V2 is based on TO-2 so if you advance thrust lever from TO-2 to TO (i.e. to amber line) your previously calculated speed is incorrect and could be below the Vmca of TO.

                              Comment


                                #16
                                Alright, that's what I understood.

                                Thanks a lot
                                Noah Scohy

                                Comment


                                  #17
                                  It's about controllability on the ground as well as in the air.
                                  William Holland

                                  Comment


                                    #18
                                    Originally posted by pshkong View Post
                                    Your V2 is based on TO-2 so if you advance thrust lever from TO-2 to TO (i.e. to amber line) your previously calculated speed is incorrect and could be below the Vmca of TO.
                                    Your scenario about being below Vmca because of an increase in thrust is 100% incorrect.
                                    Rafael Cordoves

                                    Comment


                                      #19
                                      Originally posted by Icaruss View Post

                                      Your scenario about being below Vmca because of an increase in thrust is 100% incorrect.

                                      How?


                                      From Boeing 777 FCTM

                                      DERATED TAKEOFF THRUST (FIXED DERATE)

                                      Derated takeoff thrust (fixed derate) is a certified takeoff thrust rating lower than full
                                      rated takeoff thrust. In order to use derated takeoff thrust, takeoff performance data
                                      for the specific fixed derate level is required. Derated takeoff thrust is obtained by
                                      selection of TO 1 or TO 2 in the FMC.

                                      When using derated takeoff thrust, the takeoff thrust setting is considered a takeoff
                                      operating limit since minimum control speeds (VMCG and VMCA), stabilizer trim
                                      setting, and Minimum Takeoff Weight are based on the derated takeoff thrust. Thrust
                                      levers should not be advanced unless conditions are encountered during the takeoff
                                      where additional thrust is needed on both engines, such as a windshear condition.

                                      Note:
                                      If an engine failure occurs during takeoff, any thrust increase could result in
                                      loss of directional control. See the section titled “Engine Failure during a
                                      Derated Thrust (Fixed Derate) Takeoff” later in this chapter.


                                      ENGINE FAILURE DURING A DERATED THRUST (FIXED DERATE)
                                      TAKEOFF

                                      During a fixed derate takeoff, a thrust increase following an engine failure could
                                      result in loss of directional control and should not be accomplished unless, in the
                                      opinion of the captain, terrain clearance cannot be assured. This is because the
                                      takeoff speeds consider VMCG and VMCA only at the fixed derate level of thrust.


                                      Comment


                                        #20
                                        The primary benefit of using derated thrust is to lower the Vmcg where surface conditions are marginal, thus allowing operations which could not be accomplished with flex thrust (ATM).
                                        Dan Downs KCRP
                                        i7-10700K 32GB 3600MHz 2080Ti

                                        Comment


                                          #21
                                          Originally posted by pshkong View Post


                                          How?


                                          From Boeing 777 FCTM

                                          DERATED TAKEOFF THRUST (FIXED DERATE)

                                          Derated takeoff thrust (fixed derate) is a certified takeoff thrust rating lower than full
                                          rated takeoff thrust. In order to use derated takeoff thrust, takeoff performance data
                                          for the specific fixed derate level is required. Derated takeoff thrust is obtained by
                                          selection of TO 1 or TO 2 in the FMC.

                                          When using derated takeoff thrust, the takeoff thrust setting is considered a takeoff
                                          operating limit since minimum control speeds (VMCG and VMCA), stabilizer trim
                                          setting, and Minimum Takeoff Weight are based on the derated takeoff thrust. Thrust
                                          levers should not be advanced unless conditions are encountered during the takeoff
                                          where additional thrust is needed on both engines, such as a windshear condition.

                                          Note:
                                          If an engine failure occurs during takeoff, any thrust increase could result in
                                          loss of directional control. See the section titled “Engine Failure during a
                                          Derated Thrust (Fixed Derate) Takeoff” later in this chapter.


                                          ENGINE FAILURE DURING A DERATED THRUST (FIXED DERATE)
                                          TAKEOFF

                                          During a fixed derate takeoff, a thrust increase following an engine failure could
                                          result in loss of directional control and should not be accomplished unless, in the
                                          opinion of the captain, terrain clearance cannot be assured. This is because the
                                          takeoff speeds consider VMCG and VMCA only at the fixed derate level of thrust.

                                          The worst is that I knew that and I have this FCTM at home but I completely forgot.
                                          Noah Scohy

                                          Comment

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