Re: Dash-8 incorrect takeoff configuration.

From	Sylvia Else <sylvia@email.invalid>
Newsgroups	aus.aviation
Subject	Re: Dash-8 incorrect takeoff configuration.
Date	2025-01-27 16:56 +0800
Message-ID	<lvp024Fe19nU1@mid.individual.net> (permalink)
References	(9 earlier) <op.20xrlxc5byq249@pvr2.lan> <lvma2mFtngU1@mid.individual.net> <op.20y5a4xebyq249@pvr2.lan> <lvofn3FbmkvU1@mid.individual.net> <op.200yyknlbyq249@pvr2.lan>

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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?

Do you agree that takeoff weight can be calculated from thrust and 
acceleration?

Sylvia.

Thread

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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