Usind the Assumed Temp/Thrust Derate - the Engine failure scenario
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Not aware of any delay with rudder control inputs (in a Vmcg limited situation any delay would be "interesting" .. the usual delays are built in to give some pad for distance schedules.
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groundfloor,
As John_T correctly states (or opines), there is no time lag (e.g. 1 to 2 seconds) allowed for in Vmcg certification. Such a wait, in my experience, would result in the aircraft departing the runway laterally!
All certification test flying, and normal operations, expects that the pilot will, without delay, continue to positively control the aircraft within normal parameters. In this context, it is expected that the pilot will immediately apply appropriate control inputs (rudder) to keep the aircraft on the runway centre-line. It IS recognised that there is inevitably a time lag between pilot input and the desired results, and this leads to such things as minimum runway width for aircraft types (controlling the swing after engine failure), and initial yaw from Runway Heading following engine failure airborne requiring immediate return to within 5° of Runway Heading. You would be familiar with the latter case from Instrument Rating Issue and Renewal standards.
Perhaps you're confusing the "built in" 1 or 2 second delay with the certification rules requiring this delay for Engine Failure recognition, which directly impacts upon the V1 calculation, Accelerate-Stop Distances, and Accelerate-Go Distances. This is a distance consideration, NOT a control consideration.
I don't know if you've seen any video clips of Vmcg testing, I don't have any, but they are available. These were done by test pilots expecting the failure, and in every case, lead to significant and alarming departure from the Runway Centre-Line. When involved in this same line of work (in a past life), one of my colleagues put the aircraft into a snow bank beside the runway, thank goodness that it was snow. In my own experience, I've had some very close encounters with the runway edge, and that was always after taking IMMEDIATE action to control the situation without any time delay.
Thanks for the PM groundfloor, regrettably I cannot provide you with the identity of the PPrune contributor who has significant experience in this area. He values his anonymity as I do. (At least you know the gender, that's a start).
Best Regards,
Old Smokey
As John_T correctly states (or opines), there is no time lag (e.g. 1 to 2 seconds) allowed for in Vmcg certification. Such a wait, in my experience, would result in the aircraft departing the runway laterally!
All certification test flying, and normal operations, expects that the pilot will, without delay, continue to positively control the aircraft within normal parameters. In this context, it is expected that the pilot will immediately apply appropriate control inputs (rudder) to keep the aircraft on the runway centre-line. It IS recognised that there is inevitably a time lag between pilot input and the desired results, and this leads to such things as minimum runway width for aircraft types (controlling the swing after engine failure), and initial yaw from Runway Heading following engine failure airborne requiring immediate return to within 5° of Runway Heading. You would be familiar with the latter case from Instrument Rating Issue and Renewal standards.
Perhaps you're confusing the "built in" 1 or 2 second delay with the certification rules requiring this delay for Engine Failure recognition, which directly impacts upon the V1 calculation, Accelerate-Stop Distances, and Accelerate-Go Distances. This is a distance consideration, NOT a control consideration.
I don't know if you've seen any video clips of Vmcg testing, I don't have any, but they are available. These were done by test pilots expecting the failure, and in every case, lead to significant and alarming departure from the Runway Centre-Line. When involved in this same line of work (in a past life), one of my colleagues put the aircraft into a snow bank beside the runway, thank goodness that it was snow. In my own experience, I've had some very close encounters with the runway edge, and that was always after taking IMMEDIATE action to control the situation without any time delay.
Thanks for the PM groundfloor, regrettably I cannot provide you with the identity of the PPrune contributor who has significant experience in this area. He values his anonymity as I do. (At least you know the gender, that's a start).
Best Regards,
Old Smokey
groundfloor, to reinforce the replies by J T and O S.
Vmcg is primarily concerned with ‘Go’. The flight test interest is in recognizing and controlling the asymmetric condition.
Inability to control the aircraft’s deviation within limits defines the ‘Stop’ boundary; reaction times are only considered in this situation.
Re Vmcg testing – see AC25-7A Flight test guide for certification of transport category airplanes.
AC25-7A Chapt 2, para 23, circa page count 115/118
For the ‘Stop’ aspects see page 44 onwards, and Appx 2 ‘Historical development of accelerate-stop time delays’, circa page 406.
For Vmcg and accelerate / stop, see CS 25 Large Aircraft, Amendment 4, CS 25.149 (page 27) and AMC CS25.149 (page 267). Also CS25.107 and AMC CS25.101 – 107 page 243 - (fig 1 accel/stop time delays).
Vmcg is primarily concerned with ‘Go’. The flight test interest is in recognizing and controlling the asymmetric condition.
Inability to control the aircraft’s deviation within limits defines the ‘Stop’ boundary; reaction times are only considered in this situation.
Re Vmcg testing – see AC25-7A Flight test guide for certification of transport category airplanes.
AC25-7A Chapt 2, para 23, circa page count 115/118
For the ‘Stop’ aspects see page 44 onwards, and Appx 2 ‘Historical development of accelerate-stop time delays’, circa page 406.
For Vmcg and accelerate / stop, see CS 25 Large Aircraft, Amendment 4, CS 25.149 (page 27) and AMC CS25.149 (page 267). Also CS25.107 and AMC CS25.101 – 107 page 243 - (fig 1 accel/stop time delays).
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A very big thankyou to all the respondants!
In a "previous life" I was involved at Sqn level with the Test Flight fraternity - boy did they open my eyes! Speaking with someone who has actually experienced these scenario`s is priceless. They will quickly point out the difference between a "hard" limit be it controllability or structural strength and "legal parameters".
Thanks.
In a "previous life" I was involved at Sqn level with the Test Flight fraternity - boy did they open my eyes! Speaking with someone who has actually experienced these scenario`s is priceless. They will quickly point out the difference between a "hard" limit be it controllability or structural strength and "legal parameters".
Thanks.
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taking IMMEDIATE action to control the situation without any time delay
.. and, with some of the older Types .. that included full aileron to take advantage of some drag asymmetry ... delays were never intentional and sweaty was he who delayed more than a millisecond or two in getting the feet and hands into the right places .... I have fond memories of visual tours of the grass on the Electra in years gone by ...
.. and, with some of the older Types .. that included full aileron to take advantage of some drag asymmetry ... delays were never intentional and sweaty was he who delayed more than a millisecond or two in getting the feet and hands into the right places .... I have fond memories of visual tours of the grass on the Electra in years gone by ...
