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Groups > aus.aviation > #27491
| From | Sylvia Else <sylvia@email.invalid> |
|---|---|
| Newsgroups | aus.aviation |
| Subject | Re: Dash-8 incorrect takeoff configuration. |
| Date | 2025-01-27 12:17 +0800 |
| Message-ID | <lvofn3FbmkvU1@mid.individual.net> (permalink) |
| References | (7 earlier) <lvihukFd5foU1@mid.individual.net> <lvjmkaFiof3U1@mid.individual.net> <op.20xrlxc5byq249@pvr2.lan> <lvma2mFtngU1@mid.individual.net> <op.20y5a4xebyq249@pvr2.lan> |
On 26-Jan-25 5:14 pm, Rod Speed wrote: > On Sun, 26 Jan 2025 19:29:10 +1100, Sylvia Else <sylvia@email.invalid> > wrote: > >> On 25-Jan-25 11:21 pm, Rod Speed wrote: >>> On Sat, 25 Jan 2025 19:44:58 +1100, Sylvia Else >>> <sylvia@email.invalid> wrote: >>> >>>> On 25-Jan-25 6:19 am, Daryl wrote: >>>>> On 25/1/2025 12:59 am, Sylvia Else wrote: >>>>>> On 24-Jan-25 4:21 pm, Rod Speed wrote: >>>>>>> Sylvia Else <sylvia@email.invalid> wrote >>>>>>>> Rod Speed wrote >>>>>>>>> Sylvia Else <sylvia@email.invalid> wrote >>>>>>>>>> Rod Speed wrote >>>>>>>>>>> Sylvia Else <sylvia@email.invalid> wrote >>>>>>> >>>>>>>>>>>> https://www.atsb.gov.au/publications/investigation_reports/2025/ report/ao-2024-038 >>>>>>> >>>>>>>>>>>> It's time all public transport aircraft had takeoff >>>>>>>>>>>> performance monitoring, no matter the size. >>>>>>> >>>>>>>>>>> That isnt going to result in the problem being >>>>>>>>>>> fixed quickly enough to stop an accident >>>>>>> >>>>>>>>>> Well before an abort becomes risky, the system has enough >>>>>>>>>> informationto determine whether the crew calculated v1 and vr >>>>>>>>>> are correct, >>>>>>> >>>>>>>>> Bullshit with that incorrect flaps setting. >>>>>>> >>>>>>>>>> and whether the aircraft will be able toboth continue a >>>>>>>>>> takeoff, and stop, at v1. >>>>>>> >>>>>>>>> Bullshit with that incorrect flaps setting, let alone >>>>>>>>> tell the pilots that the flaps setting is wrong. >>>>>>> >>>>>>>>> It would make much more sense to compare the >>>>>>>>> actual settings with that has been entered at the >>>>>>>>> preflight config calculations and tell the pilots >>>>>>>>> that they have not set what was required with >>>>>>>>> flaps and boost etc before they actually applied >>>>>>>>> takeoff power and not allow takeoff power to be >>>>>>>>> applied before those were set correctly. >>>>>>> >>>>>>>>>> It can issue an abort alert if not. >>>>>>> >>>>>>>>> See above >>>>>>> >>>>>>>>>> This covers at least miscalculated v1, miscalculated vr, wrong >>>>>>>>>> thrust settings, wrong flap settings, starting from the wrong >>>>>>>>>> intersection, takeoff from the wrong runway, and no doubt >>>>>>>>>> others that I haven't even thought of. >>>>>>> >>>>>>>>> It would be stupid to try to measure that while taking off >>>>>>>>> instead of doing that before takeoff power is applied >>>>>>> >>>>>>>>> Yes, there is also a different problem with the engines >>>>>>>>> not being able to deliver the power they were assumed >>>>>>>>> to be able to deliver the power they were supposed to >>>>>>>>> be able to deliver in the preflight calculations, but that >>>>>>>>> was not the case in the incident being discussed and >>>>>>>>> it would be much easier to discover than much earlier >>>>>>>>> in the takeoff run than V1 or VR >>>>>>> >>>>>>>> The question the system needs to ask is "In the current >>>>>>>> configuration, with the measured acceleration [*], current >>>>>>>> airspeed, and current position on the current runway, can the >>>>>>>> aircraft reach the specified V1 at a point where it can continue >>>>>>>> the takeoff or abort, and will it be able to rotate at the >>>>>>>> specified Vr. >>>>>>> >>>>>>> The problem with that approach is that is far too late >>>>>>> during the takeoff run to be doing that by measurement >>>>>>> when its much too late for the pilots to be fixing what >>>>>>> the problem is, particularly when the engines arent >>>>>>> actually performing the way they were meant to when >>>>>>> the prefight calculations were done >>>>>> >>>>>> There would be no expectation that the pilots would fix it. The >>>>>> idea is to abort the takeoff while that can still be done safely. >>>>> I assume that you are talking about some sort of automated system >>>>> to alert pilots of a configuration error? >>>>> If so wouldn't that rely on data input by the pilots prior to >>>>> takeoff so the system would be only as good as the data therefore >>>>> it doesn't completely eliminate the chances of an error? >>>>> In this incident did the pilots self report? >>>>> If they didn't why would the ATSB investigate? >>>>> >>>> >>>> My thinking is that the system has access to the settings for flap, >>>> thrust, mass, V1 and Vr. None of these is assumed to be correct. >>>> >>>> Also access to GPS and airspeed. >>>> >>>> In the following, the system would allow some level of discrepancy >>>> so as not to cause unnecessary aborts. >>>> >>>> Once the aircraft is accelerating, its direction together with the >>>> GPS calculated position allows the system to determine which runway >>>> the aircraft is on (position alone may not be sufficient, where >>>> runways intersect). >>> >>>> The acceleration to be expected from a given thrust setting depends >>>> on the aircraft's mass, and its airspeed. So the system waits until >>>> there is a reliable airspeed. It then can calculate the mass from >>>> the expected thrust, the acceleration and the airspeed. The result >>>> should match the setting. If it doesn't this means that either the >>>> mass is set wrong, or the expected thrust, based on the thrust >>>> setting, is not being achieved. Either of these aborts the takeoff. > >>> Not possible to MEASURE that the flaps haven't been set correctly >>> before V1 because you can only measure the effect of that after VR >>> when rotation has been attempted and it can measure that it doesnt >>> see the weight leaving the wheels in the way that it should have, > >> The issue is only whether the aircraft will take off at the set Vr, >> which is a function of the flap setting, and aircraft mass. > > Yes > >> This is something that can be determined from the aircraft'sflight >> performance data - the same data that the crew use. > > That isnt MEASUREMEMT of the plane's performance during the takeoff run > >> If the flaps are not at the position set for them, that'ssomething >> that should already have been alerted. > > What I said right from the start > >>> And given that it is already past V1, no way to abort by then >>> Makes a lot more sense to enter all the paramaters that will >>> be used like thrust settings and flaps etc and them before >>> takeoff power can be applied, check that that has been done. > >>>> Vr can now be calculated based the mass and flap setting. If the >>>> calculated Vr differs from the set Vr, this aborts the takeoff. > >>> Too late by then, its already past V1 so it can't be aborted > >> Why is it already past v1? > > Because that's the only time you know that it can't rotate at the time > that it should have been able to, because the flap setting is wrong. > >>>> From the current position, the acceleration and the mass, the >>>> braking distance can be calculated [*], and from that V1. If the >>>> calculated V1 is lower than the set V1, then abort take off. > >>>> [*] This is one area of uncertainty, since braking distance depends >>>> on runway condition (wet, dry, etc.). > >>> And can't be measured during the takeoff run > >> No, it cannot, hence the uncertainty. But if the system assumes good >> braking, and the calculated v1 is less than the set v1, then the set >> v1 is wrong regardless of the actual braking conditions. > > So its too late to abort the takeoff > > So the only thing that makes any sense is to check that the pilots > have actually set stuff like flaps and takeoff power they way they > have calculated needs to be BEFORE the takeoff can happen. > > No point in measuring anything once the takeoff run has started except with > the engine performance and that isnt what is being discussed with this > incident. Do you agree that, knowing only the aerodynamic properties of the air-frame, the actual flap position and the actual takeoff weight, the correct Vr can be calculated? If not, what else is needed? Sylvia.
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Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-21 13:28 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-23 04:21 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-23 12:50 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-23 20:09 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-24 14:14 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-24 19:21 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-24 21:59 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-25 03:46 +1100
Re: Dash-8 incorrect takeoff configuration. Daryl <dwalford@westpine.com.au> - 2025-01-25 09:19 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-25 13:17 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-25 19:34 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-25 16:44 +0800
Re: Dash-8 incorrect takeoff configuration. Daryl <dwalford@westpine.com.au> - 2025-01-25 22:36 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-25 22:12 +0800
Re: Dash-8 incorrect takeoff configuration. Daryl <dwalford@westpine.com.au> - 2025-01-26 09:36 +1100
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-26 10:07 +1100
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-26 02:21 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-26 16:29 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-26 20:14 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-27 12:17 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-27 19:52 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-27 16:56 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-28 04:33 +1100
Re: Dash-8 incorrect takeoff configuration. Sylvia Else <sylvia@email.invalid> - 2025-01-28 11:52 +0800
Re: Dash-8 incorrect takeoff configuration. "Rod Speed" <rod.speed.aaa@gmail.com> - 2025-01-28 15:57 +1100
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