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Groups > aus.aviation > #27494
| From | "Rod Speed" <rod.speed.aaa@gmail.com> |
|---|---|
| Newsgroups | aus.aviation |
| Subject | Re: Dash-8 incorrect takeoff configuration. |
| Date | 2025-01-28 04:33 +1100 |
| Message-ID | <op.201m1ic8byq249@pvr2.lan> (permalink) |
| References | (10 earlier) <lvma2mFtngU1@mid.individual.net> <op.20y5a4xebyq249@pvr2.lan> <lvofn3FbmkvU1@mid.individual.net> <op.200yyknlbyq249@pvr2.lan> <lvp024Fe19nU1@mid.individual.net> |
On Mon, 27 Jan 2025 19:56:36 +1100, Sylvia Else <sylvia@email.invalid> wrote: > On 27-Jan-25 4:52 pm, Rod Speed wrote: >> On Mon, 27 Jan 2025 15:17:39 +1100, Sylvia Else <sylvia@email.invalid> >> wrote: >> >>> 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? >> Nope, you also need to know the temperature, wind speed and >> direction and there is no way to measure the actual takeoff weight > Vr is an indicated airspeed, so why do you need to know wind-speed or > temperature? You said CALCULATED. Yes you need both to CALCULATE VR. so you can attempt to rotate when the indicated air speed reaches the value that you have calculated that rotation should be attemped. > Do you agree that takeoff weight can be calculated from thrust and > acceleration? Not when you can't be sure that the measured thrust has been measured accurately particularly when the engines are still spinning up after TOGA has been applied, and acceleration is also variable, particularly when the wind direction and speed is changing substantially during the takeoff run Still makes a lot more sense to check that stuff like flaps, engine power, bleed air bypass has actually been set the way the pilots have calculated needs to be set before they are allowed to actually takeoff and that is MUCH easier to do and doesnt require expensive extra equipment in the plane and allows the pilots to check that the checking system hasnt got it wrong and doesnt need a risky attempt to abort the takeoff before V1 Your approach makes no sense at all except to actually measure that the acceleration that should be happening actually is happening during the takeoff run because there is some problem with at least one engine etc. And isnt even possible with the flap setting because you can only measure that the expected lift is being seen once an attempt at rotation has been attempted because its past VR and by then its too late to abort the takeoff because the plane is already past V1
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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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