Re: Dash-8 incorrect takeoff configuration.

From	Sylvia Else <sylvia@email.invalid>
Newsgroups	aus.aviation
Subject	Re: Dash-8 incorrect takeoff configuration.
Date	2025-01-26 16:29 +0800
Message-ID	<lvma2mFtngU1@mid.individual.net> (permalink)
References	(5 earlier) <op.20vdh9dzbyq249@pvr2.lan> <lvhkmqF8lmsU1@mid.individual.net> <lvihukFd5foU1@mid.individual.net> <lvjmkaFiof3U1@mid.individual.net> <op.20xrlxc5byq249@pvr2.lan>

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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. This is 
something that can be determined from the aircraft's flight performance 
data - the same data that the crew use.

If the flaps are not at the position set for them, that's something that 
should already have been alerted.

> 
> 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?
> 
>>  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.

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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