Announcement

Collapse
No announcement yet.

Greenland Dash 8 guides Twin Cessna to safety

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by 3WE View Post
    A good procedure when you need to fly kind of slow.

    Increases your margin above stall speed.

    I guess they left that out on the Dash-8 QRH under the heading "Helping a Small, Slow Twin with Navigation Issues", and we cannot refer to QRH's from a 737-200 nor 737-236A for general reference.
    You are mean!!!

    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
    --- Defend what you say with arguments, not by imposing your credentials ---

    Comment


    • #32
      Originally posted by Gabriel View Post
      Flaps do increase drag.
      Exactamundo.
      They didn't extend the flaps to increase the drag, that was a side effect in this case.
      Did you really think I meant that? I used the phrase 'dragging it down' as slang for slowing down with flap extension rather than remaining clean with only thrust reduction and pitch. I am aware of basic aerodynamics and the lift aspect of high-lift devices. Cut me some fricken slack here.

      Comment


      • #33
        Originally posted by Gabriel View Post
        You are mean!!!
        ...nothing like tension between black and white procedures and fundamental over riding concepts...

        Both have their place and I have disdain when the background is dismissed or lacking at the expense of the other being emphasized.

        Full power and pull up aggressively to minimize altitude loss is not the beginning nor end of the procedure.
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

        Comment


        • #34
          Originally posted by Evan View Post
          ...I am aware of basic aerodynamics...Cut me some fricken slack here...
          Originally posted by Evan
          ...they had to bring out significant drag to stay with it...
          No, you are not aware of basic aerodynamics, they most likely deployed a 'takeoff -like" flap setting, which did not cause significant drag.

          Black and white thinking: Flaps = Significant drag. Pretty much where you live...no, not totally, but pretty strongly.
          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

          Comment


          • #35
            Originally posted by 3WE View Post
            No, you are not aware of basic aerodynamics, they most likely deployed a 'takeoff -like" flap setting, which did not cause significant drag.
            Really, a Dash8 matching final approach speed of a twin Cessna whilst maintaining height without getting significant drag out? How is that done? I guess 'significant' is your black and white word.

            This is one of the stupidest conversations we have had in recent memory (cue: ATLCrew). I used 'drag' as an expression for flaps (an expression picked up from pilots btw) and suddenly I don't understand the basic aerodynamic purpose of reconfiguration. Welcome to the hen house.

            Comment


            • #36
              Originally posted by Evan View Post
              Really, a Dash8 matching final approach speed of a twin Cessna whilst maintaining height without getting significant drag out? How is that done?
              Repeating...

              By trimming nose up, and by adding flaps to improve the margin between the slow speed and the stall speed. Drag is not used to make a Dash 8 fly at speeds similar to a light twin.

              And, no I have no problem with numerous meanings of significant.

              Indeed, just about any flap usage will result in a measurable, statistically significant difference in drag.

              However, "takeoff flap settings" are determined by your scientific engineer friends (and maybe even designed into the flap systems), to keep the drag from causing a significant increase in takeoff distance. In fact, they tend to cause a significant decrease in takeoff distance, which would tell me that the drag was insignificant...

              Can you comprehend the term"Practical significance"?
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

              Comment


              • #37
                Originally posted by 3WE View Post
                Repeating...

                By trimming nose up, and by adding flaps to improve the margin between the slow speed and the stall speed. Drag is not used to make a Dash 8 fly at speeds similar to a light twin.
                Repeating...

                Drag is not used to make a Dash 8 fly at speeds similar to a light twin (although it might be used to slow it down in the first place), however a drag penalty is incurred by flap extension. Hence the saying "getting out some drag" when extending flaps, and hence the inference of this statement:

                The Dash 8 followed 3000 feet above the Cessna with flaps extended to slow the aircraft down and match their speed with the Cessna, there was sufficient fuel on board so that this was not a concern to the Dash.
                ..."this" meaning the drag penalty.

                Flaps lower the critical angle of attack, but they also lower the AoA required to maintain level flight by increasing the coefficient of lift, allowing you to fly slower. Thay also add drag which helps to manage stable airspeed.

                Yes, we are talking about significant drag. You are talking about "practical significance"?. I don't know what you are talking about, or what point you are trying to make.

                Comment


                • #38
                  Originally posted by Evan View Post
                  Did you really think I meant that? I used the phrase 'dragging it down' as slang for slowing down with flap extension rather than remaining clean with only thrust reduction and pitch.
                  I don't read minds, especially not in English. I read text, and it seems that I took it too literally.

                  I am aware of basic aerodynamics and the lift aspect of high-lift devices. Cut me some fricken slack here.
                  I am also aware of basics aerodynamics (and a bit beyond basics too) and of the drag aspect of high-lift devices that you were trying to explain to me.

                  Given that you know that I know it, I would have expected that you picked my misunderstanding after my first reply.

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

                  Comment


                  • #39
                    Originally posted by Evan View Post
                    ...I don't know what you are talking about, or what point you are trying to make...
                    And Gabel and I have no idea what you are talking about. (I don't read minds either).

                    As best as I can tell you are seriously fixated on drag, since you keep bringing it up and arguing with Gabriel and I about it.

                    So maybe extending the flaps resulted in a little more fuel burn, so, you have a little academic curiosity about that??? Is this your point?


                    But,

                    1) It's probably minor (for the fifth time) and they probably monitored fuel consumption like always and landed with full legal reserves.

                    2) Ever seen a drag curve? Maybe at a slower speed, the parasite drag is reduced so much that the 'MPG' is equal or even better than at cruise -even with a few flaps out

                    Gabel, I'm thinking this could easily be true. I never added power when I extended 10 degrees of flaps on downwind at 70 kts (a 172s approximate best glide speed)... AND I never noticed speed nor altitude loss. Maybe 1 or 2 knots, but genuinely intangible... contrast that with the 'mpg' of cruising.

                    3) How about speaking English and NOT using the word drag for an operation where the pilots had no need or desire for drag. I know you want to be cool and all, but I've never heard any of our resident pilots refer to flaps (especially a take off setting) as 'getting some drag out.'

                    4) Please get a mirror and do some soul searching that you do have some obsession with drag here... the word and the concept. It's very clear in your posts here or keep arguing with two folks who have every bit as much expertise as you on the subject of flaps and drag.
                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                    Comment


                    • #40
                      Originally posted by 3WE View Post

                      4) Please get a mirror and do some soul searching that you do have some obsession with drag here...
                      That's hilarious. I drop the word 'drag' colloquially to refer to flap deployment, Gabriel points out that drag is not the reason for getting the flaps out (I think he understands this misunderstanding now) and YOU become obsessed with my use of the word 'drag' and then 'drag' this thread through the usual mud... and then you tell ME to look in the mirror. Well played 3WE, I can't top that.

                      Comment


                      • #41
                        Originally posted by LH-B744 View Post
                        And it was a bit of luck, too. Both a/c are twin-engine propellers? So, they operate with approx. the same speed?
                        I'm going to try this again... The Dash 8 had to deploy flaps to slow down to match the Cessna's approach speed. We don't know what is meant by "twin Cessna' but AFAIK both the 310's and the 440's put that speed (on the downwing leg) around 110-120kts. My initial assumption was that this was a Q300-Q400 but I now see that the other aircraft was actually a Dash-8-200. Still, my guess is that a Dash-8-200 is going to need at least 15° of flaps out to safely stay level 3000' above and behind a "twin Cessna" on final. Vfe is 148kts for flaps 15 and 130kts for flaps 35. That will add enough drag to have a significant effect on fuel burn but the report states that the Dash 8 had ample contingency fuel for this maneuver. The fact that they are both twinprops doesn't translate to equivalent approach speeds.

                        Comment


                        • #42
                          Cessna 310 stall speed: 63kts, final approach speed 80/90
                          Cessna 441 stall speed: 75kts, final approach speed 95/110
                          Both planes can easily approach at well above that until short final.
                          And, if you are with an engine out and have a sufficiently long runway, landing with as little flaps as practical is a good practice since you will have less drag, and hence less thrust, and hence less asymmetric thrust.

                          Vfe is how fast you may extend the flaps (or have them extended). It tells you nothing about how slow you can fly.
                          But of course you knew it already, so I don't see why you bring Vfe to the discussion.
                          But it adds some value: If Vfe 15 is 148, it means that even at MTOW you can fly quite slower than that (120 kts or less) with whatever flap position comes before 15. ANd of course they were not at MTOW.

                          From all we know, the Dash 8 may have just extended the flaps to the first position, that I don't know what it is.

                          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                          --- Defend what you say with arguments, not by imposing your credentials ---

                          Comment


                          • #43
                            Originally posted by Evan, multiple times
                            Flaps, drag, fuel burn... flaps, drag, fuel burn...
                            Originally posted by Gabe & 3BS, multiple times
                            Probably not all that significant at lower flap settings
                            But no, we arrive at post number 41, and see this highly detailed but largely fabricated scenario:

                            Originally posted by Evan View Post
                            I'm going to try this again... The Dash 8 had to deploy flaps to slow down to match the Cessna's approach speed. We don't know what is meant by "twin Cessna' but AFAIK both the 310's and the 440's put that speed (on the downwing leg) around 110-120kts. My initial assumption was that this was a Q300-Q400 but I now see that the other aircraft was actually a Dash-8-200. Still, my guess is that a Dash-8-200 is going to need at least 15° of flaps out to safely stay level 3000' above and behind a "twin Cessna" on final. Vfe is 148kts for flaps 15 and 130kts for flaps 35. That will add enough drag to have a significant effect on fuel burn but the report states that the Dash 8 had ample contingency fuel for this maneuver. The fact that they are both twinprops doesn't translate to equivalent approach speeds.
                            Nahhh, no obsession with a largely imaginary drag problem here.
                            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                            Comment


                            • #44
                              Originally posted by Gabriel View Post
                              Cessna 310 stall speed: 63kts, final approach speed 80/90
                              Cessna 441 stall speed: 75kts, final approach speed 95/110
                              Both planes can easily approach at well above that until short final.
                              And, if you are with an engine out and have a sufficiently long runway, landing with as little flaps as practical is a good practice since you will have less drag, and hence less thrust, and hence less asymmetric thrust.

                              Vfe is how fast you may extend the flaps (or have them extended). It tells you nothing about how slow you can fly.
                              But of course you knew it already, so I don't see why you bring Vfe to the discussion.
                              But it adds some value: If Vfe 15 is 148, it means that even at MTOW you can fly quite slower than that (120 kts or less) with whatever flap position comes before 15. ANd of course they were not at MTOW.

                              From all we know, the Dash 8 may have just extended the flaps to the first position, that I don't know what it is.
                              Well, that's what I'm getting at. Can you safely maintain level flight at around 110-115kts and around 3000' in a Dash-8-200 with flaps 5 or even 10? Bearing in mind that 'safely' means with a healthy margin below stall and a healthy speed margin (+10-15 kts) for ice accretion. I figure you would need 15° out to do that safely. Maybe you know better than I do.

                              I mentioned Vfe to show that flaps 35 is also available up to 130kts. If your object was to stay well behind a slower Vref plane while safely maintaining altitude and fuel burn wasn't an issue, why not go full flaps?

                              Comment


                              • #45
                                Originally posted by Evan View Post
                                Well, that's what I'm getting at. Can you safely maintain level flight at around 110-115kts and around 3000' in a Dash-8-200 with flaps 5 or even 10? Bearing in mind that 'safely' means with a healthy margin below stall and a healthy speed margin (+10-15 kts) for ice accretion. I figure you would need 15° out to do that safely. Maybe you know better than I do.
                                May the Cessna 441 have been approaching at 140 kts until short final?

                                We don't know what Cessna twin it was, we don't know how fast it was approaching. We do know that the Dash 8 extended flaps. We don't know how much. Neither of us knows better than the other simply because the info is not out there.

                                I am not saying that they didn't have full flaps. I am just explaining why, with the info available, that is not the only possibility.

                                --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                                --- Defend what you say with arguments, not by imposing your credentials ---

                                Comment

                                Working...
                                X