Air North Brasilia Crash in Darwin (Merged)
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Reference: Giancoli's "Physics" IED 6th edition.
Acceleration: "An object whose velocity is changing is said to be accel. For instance a car whose velocity changes from 0 to 80 kph is accel. Accel specifies how rapidly the velocity of an object is changing". pg 23.
As the car is unlikely to be undergoing the same accel throughout it is called average acceleration. Av Accel = change of velocity/time elapsed. Instantaneous accel is the accel during a very short period.
Inertia: Newtons 1st Law. What's at rest will want to remain at rest, what's moving will want to remain moving; unless a force is applied to it, and we're talking about a frictionless situation.
Momentum: A measure of an objects mass and velocity. A 100T truck will require a greater force to stop it than a 50T truck, both traveling at the same spd due its momentum.
F.Nose unless I'm missing something and I'd say this thread is difficult to track, there is nothing " a little bit bullsh@t" about a turboprop accel after losing an engine. How else does it get from V1 to V2 to enroute clb spd, but by accel?
This is my take on a V1 Cut:
Jet: Failure @ V1, a/c accel to VR while dead engine winds down (we're assuming complete failure i.e. no fuel flow), I'd guess it'd be a very short period before it's just drag (measured in seconds), @ VR a/c rotates and continues to accel to V2. V2 should be attained sometime while you're rotating to your engine out attitude, clb out @ V2 until terrain clr height, lvl out and accel to your enroute clb spd. END. Nothing new there!
Turboprop
MTOW) Same as above, except you now have a huge drag generating device! So with a failure at V1/VR (only turboprop I flew > 5700kg V1/VR were the same) with the Autofeather/NTS doing its job and end up at its minimum drag position i.e. feathered. However if it doesn't due to a failure of some sort and you have complete failure, that is no SHP applied you have a windmilling prop in fine pitch acting as a barn door. It's windmilling due to its areodynamic properties and while you may argue it's generating lift off the prop its got to be bloody minimal compared to the drag it produces. As to momentum of the prop, forget it. Its momentum is a product of its velocity and mass and without any force acting on it, it'll come to a stop (other than windmilling) pretty bloody quick. If an a/c can clb away with an unfeathered prop it aint going far, just to the scene of the accident! Maybe the ace of the base can keep it up, but can he accel, clean up and get it around to land? Remember , the margins in 20.7.1b aren't great.
The certification provides for the average pilot, not Chuck Yeager. I'd be more interested in wanting to fly the a/c as accurately as possible and in accordance with your training, not thinking about knocking off spd for V1, let the performance engineers work that out. If you cannot control yaw you have two options, lower the nose to get your spd above VMCA and /or reduce pwr on the live engine. I don't know about 'real world figues' verses book figures, just that they are all you have, the rest is just a stab in the dark. If it isn't doing what it should, check your config, it is embarrassing when in the sim you hear all this noise and it isn't until you do the after t/o c/l that you find you have left the gear dwn, thank god for a light TOW! Maybe if things aren't going to plan it, and you cannot see the reason and it's turning to ****e, it might be an idea to use your remaining time to select an area to put it down in a controlled fashion instead of aerodynamics choosing an uncontrolled crash site for you. (this is not a comment on the accident, it seemed to unravel pretty bloody quick)
For my thinking Remoak is the one mostly on the money.
Acceleration: "An object whose velocity is changing is said to be accel. For instance a car whose velocity changes from 0 to 80 kph is accel. Accel specifies how rapidly the velocity of an object is changing". pg 23.
As the car is unlikely to be undergoing the same accel throughout it is called average acceleration. Av Accel = change of velocity/time elapsed. Instantaneous accel is the accel during a very short period.
Inertia: Newtons 1st Law. What's at rest will want to remain at rest, what's moving will want to remain moving; unless a force is applied to it, and we're talking about a frictionless situation.
Momentum: A measure of an objects mass and velocity. A 100T truck will require a greater force to stop it than a 50T truck, both traveling at the same spd due its momentum.
F.Nose unless I'm missing something and I'd say this thread is difficult to track, there is nothing " a little bit bullsh@t" about a turboprop accel after losing an engine. How else does it get from V1 to V2 to enroute clb spd, but by accel?
This is my take on a V1 Cut:
Jet: Failure @ V1, a/c accel to VR while dead engine winds down (we're assuming complete failure i.e. no fuel flow), I'd guess it'd be a very short period before it's just drag (measured in seconds), @ VR a/c rotates and continues to accel to V2. V2 should be attained sometime while you're rotating to your engine out attitude, clb out @ V2 until terrain clr height, lvl out and accel to your enroute clb spd. END. Nothing new there!
Turboprop
MTOW) Same as above, except you now have a huge drag generating device! So with a failure at V1/VR (only turboprop I flew > 5700kg V1/VR were the same) with the Autofeather/NTS doing its job and end up at its minimum drag position i.e. feathered. However if it doesn't due to a failure of some sort and you have complete failure, that is no SHP applied you have a windmilling prop in fine pitch acting as a barn door. It's windmilling due to its areodynamic properties and while you may argue it's generating lift off the prop its got to be bloody minimal compared to the drag it produces. As to momentum of the prop, forget it. Its momentum is a product of its velocity and mass and without any force acting on it, it'll come to a stop (other than windmilling) pretty bloody quick. If an a/c can clb away with an unfeathered prop it aint going far, just to the scene of the accident! Maybe the ace of the base can keep it up, but can he accel, clean up and get it around to land? Remember , the margins in 20.7.1b aren't great.The certification provides for the average pilot, not Chuck Yeager. I'd be more interested in wanting to fly the a/c as accurately as possible and in accordance with your training, not thinking about knocking off spd for V1, let the performance engineers work that out. If you cannot control yaw you have two options, lower the nose to get your spd above VMCA and /or reduce pwr on the live engine. I don't know about 'real world figues' verses book figures, just that they are all you have, the rest is just a stab in the dark. If it isn't doing what it should, check your config, it is embarrassing when in the sim you hear all this noise and it isn't until you do the after t/o c/l that you find you have left the gear dwn, thank god for a light TOW! Maybe if things aren't going to plan it, and you cannot see the reason and it's turning to ****e, it might be an idea to use your remaining time to select an area to put it down in a controlled fashion instead of aerodynamics choosing an uncontrolled crash site for you. (this is not a comment on the accident, it seemed to unravel pretty bloody quick)
For my thinking Remoak is the one mostly on the money.
Quote:
Thus if at any time the speed (velocity) is increasing, the aircraft is accelerating.
Thus if at any time the speed (velocity) is increasing, the aircraft is accelerating.
Not in physics it isn't.
Acceleration being a measure the rate of change of velocity, not the change of velocity.
Acceleration being a measure the rate of change of velocity, not the change of velocity.
Any time the speed of anything (in this case an aircraft) changes, it's accelerating (positively when it goes faster, negatively slower). That's it.
Velocity is in miles per hour, metres per second etc, and acceleration is measured in things like metres per second per second, for example, as I'm sure you know.
Say I was doing 10 m/s and I then went faster, to 20 m/s - I've accelerated by 10 m/s. If I did that steadily over 5 seconds, I accelerated at a rate of 2 m/s per second. My average rate of acceleration was 2 m/s squared, or 2 metres per second per second.
The upshot of all this is that any time the speed of an aircraft increases (or in fact changes), it is accelerating.
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3 Eng T/off in 4 Eng aeroplane
Simple make sure MTOW not above 3 Eng MTOW.and enough runway.
Sit on end of runway with 3 operative engines at 60% T off POWER.
Advance the 2 symetrical engines to T Off power.
Apply full rudder to the the side with the most operative engines
Release brakes and keep the aircraft straight by applying power to the remaining engine usually get T off power just before V1
Pray you dont lose an engine on the same side as the inoperative engine.
Similar to a technique used by WW2 Me 109 Fighter pilots to counter torque effect on T off.
Sit on end of runway with 3 operative engines at 60% T off POWER.
Advance the 2 symetrical engines to T Off power.
Apply full rudder to the the side with the most operative engines
Release brakes and keep the aircraft straight by applying power to the remaining engine usually get T off power just before V1
Pray you dont lose an engine on the same side as the inoperative engine.
Similar to a technique used by WW2 Me 109 Fighter pilots to counter torque effect on T off.
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Boeing slide show on V1.
SmartCockpit - Airline training guides, Aviation, Operations, Safety
From SmartCockpit - Airline training guides, Aviation, Operations, Safety. See link for full article.
Inconsistent terminology has caused confusion about the V1 concept. An important assumption in the V1 concept today is that the decision to continue the takeoff or reject the takeoff is made before reaching V1. The accelerate-stop performance data in AFMs are based on the pilot flying taking the first action to reject the takeoff at V1.
[For airplane-certification purposes, the actions required to reject a takeoff include applying the wheel brakes, reducing thrust, and deploying the speed brakes or spoilers. The manufacturer establishes the order in which these actions are taken.]
Previous definitions of V1 did not state clearly that V1 is the maximum speed at which the pilot flying must take the first action to reject the takeoff. “[There is] a great deal of misunderstanding and disagreement regarding the definition and use of the V1 speed,” said FAA. “In general, inconsistent terminology used over the years in reference to V1 has probably contributed to this confusion.”
Before 1978, Part 1 defined V1 as the critical-engine failure speed. In 1978, the definition of V1 was changed to takeoff decision speed, and VEF was established as the critical-engine failure speed. V1 also is referred to as the engine failure recognition speed in the FAA Flight Test Guide for Certification of Transport Category Airplanes (Advisory Circular 25-7). FAA currently is revising the circular. FAA’s 1998 redefinition of V1 responded to a 1990 recommendation by NTSB based on a study of accidents that occurred during high-speed rejected takeoffs.
In its report on the study, NTSB said, “Runway overruns following high-speed [RTOs] have resulted and continue to result in airplane incidents and accidents. Although most RTOs are initiated at low speeds (below 100 knots) and are executed without incident, the potential for an accident or an incident following a high-speed (at or above 100 knots) RTO remains high.”
SmartCockpit - Airline training guides, Aviation, Operations, Safety
From SmartCockpit - Airline training guides, Aviation, Operations, Safety. See link for full article.
Inconsistent terminology has caused confusion about the V1 concept. An important assumption in the V1 concept today is that the decision to continue the takeoff or reject the takeoff is made before reaching V1. The accelerate-stop performance data in AFMs are based on the pilot flying taking the first action to reject the takeoff at V1.
[For airplane-certification purposes, the actions required to reject a takeoff include applying the wheel brakes, reducing thrust, and deploying the speed brakes or spoilers. The manufacturer establishes the order in which these actions are taken.]
Previous definitions of V1 did not state clearly that V1 is the maximum speed at which the pilot flying must take the first action to reject the takeoff. “[There is] a great deal of misunderstanding and disagreement regarding the definition and use of the V1 speed,” said FAA. “In general, inconsistent terminology used over the years in reference to V1 has probably contributed to this confusion.”
Before 1978, Part 1 defined V1 as the critical-engine failure speed. In 1978, the definition of V1 was changed to takeoff decision speed, and VEF was established as the critical-engine failure speed. V1 also is referred to as the engine failure recognition speed in the FAA Flight Test Guide for Certification of Transport Category Airplanes (Advisory Circular 25-7). FAA currently is revising the circular. FAA’s 1998 redefinition of V1 responded to a 1990 recommendation by NTSB based on a study of accidents that occurred during high-speed rejected takeoffs.
In its report on the study, NTSB said, “Runway overruns following high-speed [RTOs] have resulted and continue to result in airplane incidents and accidents. Although most RTOs are initiated at low speeds (below 100 knots) and are executed without incident, the potential for an accident or an incident following a high-speed (at or above 100 knots) RTO remains high.”
FOCX wrote.
[QUOTE]F.Nose unless I'm missing something and I'd say this thread is difficult to track, there is nothing " a little bit bullsh@t" about a turboprop accel after losing an engine. How else does it get from V1 to V2 to enroute clb spd, but by accel?/QUOTE]
FOCX
I'm afraid you missed my argument completely. I wasn't for a minute doubting that a turbo prop (or any other AC) can accelerate on One engine. JT made the assertion (on more than One occasion) that a turbo prop/Jet would keep accelerating for a while after One engine had failed and the live engine retarded to Ground Idle. That was what I was referring to as 'a little bit bullsh@t'.
[QUOTE]F.Nose unless I'm missing something and I'd say this thread is difficult to track, there is nothing " a little bit bullsh@t" about a turboprop accel after losing an engine. How else does it get from V1 to V2 to enroute clb spd, but by accel?/QUOTE]
FOCX
I'm afraid you missed my argument completely. I wasn't for a minute doubting that a turbo prop (or any other AC) can accelerate on One engine. JT made the assertion (on more than One occasion) that a turbo prop/Jet would keep accelerating for a while after One engine had failed and the live engine retarded to Ground Idle. That was what I was referring to as 'a little bit bullsh@t'.
Moderator
I think that one should read what was written rather than making it up as you go along and then ascribing it to a prior post ....
The point about continued acceleration is only relevant to the initial (short) rundown period ... thereafter, the engine provides drag. So far as a failed, as against a throttled back, engine, the only difference is the time history of the rundown and the steady state thrust situation .. the general characteristics are similar.
The pertinent point is that the thrust doesn't disappear instantaneously and, as a consequence, one usually sees a short speed overrun associated with the thrust rundown.
The point about continued acceleration is only relevant to the initial (short) rundown period ... thereafter, the engine provides drag. So far as a failed, as against a throttled back, engine, the only difference is the time history of the rundown and the steady state thrust situation .. the general characteristics are similar.
The pertinent point is that the thrust doesn't disappear instantaneously and, as a consequence, one usually sees a short speed overrun associated with the thrust rundown.
[QUOTE]I think that one should read what was written rather than making it up as you go along and then ascribing it to a prior post ..../QUOTE]
Whilst I have better things to do than get involved in a pointless argument I believe that I have indeed carefully read what you have written. I agree with most of your comments and have found them educational however....
These are your words.
[QUOTE]During the rundown period, the thrust progressively reduces, resulting in a speed overrun with a hump such as shown generically in the Boeing sketch. Just the way the real world works, I'm afraid./QUOTE]
Can you please explain where this hump is because I see a very small horizontal line... representing Inertia, followed by a marked down curve...deceleration.
I agree that an engine will not go from T/O power to ground idle instantaneously when the throttle is cut... However the power required to keep an AC accelerating on 1 engine will be very quickly lost (as near a damn it to instantaneously) once the throttle is slammed shut. It does not have to get anywhere near ground idle.
Whilst I have better things to do than get involved in a pointless argument I believe that I have indeed carefully read what you have written. I agree with most of your comments and have found them educational however....
These are your words.
[QUOTE]During the rundown period, the thrust progressively reduces, resulting in a speed overrun with a hump such as shown generically in the Boeing sketch. Just the way the real world works, I'm afraid./QUOTE]
Can you please explain where this hump is because I see a very small horizontal line... representing Inertia, followed by a marked down curve...deceleration.
I agree that an engine will not go from T/O power to ground idle instantaneously when the throttle is cut... However the power required to keep an AC accelerating on 1 engine will be very quickly lost (as near a damn it to instantaneously) once the throttle is slammed shut. It does not have to get anywhere near ground idle.
(ix) Any residual acceleration that occurs after V1, while the airplane and its systems become stabilized in the braking configuration, must be accounted for in the expansion of accelerate-stop performance data for presentation in the AFM. The effects of system transients, such as engine spin-down, brake pressure ramp-up, spoiler actuation times, etc., should be accounted for in this time period.
F.Nose - this is straight from the certification guidlines and indicates that acceleration may occur after V1, included in the factors is engine spin-down.
Engine spin/run/spool-down acceleration is allowed for in the ASDR calculation. This means someone has measured it and proved it exists in at least one aircraft.
JT is just providing a reason as to why this is.
Moderator
These are your words.
Indeed .. I definitely wrote that ... however, my words didn't include ..
would keep accelerating for a while after One engine had failed and the live engine retarded to Ground Idle.
.. the bean counters would love such an aircraft .. one could forget about fuel hedging and like sleepless night matters ..
Can you please explain where this hump is because I see a very small horizontal line
.. it would appear that one man's hump is another man's horizontal line ?
Indeed .. I definitely wrote that ... however, my words didn't include ..
would keep accelerating for a while after One engine had failed and the live engine retarded to Ground Idle.
.. the bean counters would love such an aircraft .. one could forget about fuel hedging and like sleepless night matters ..
Can you please explain where this hump is because I see a very small horizontal line
.. it would appear that one man's hump is another man's horizontal line ?
[QUOTE] This means someone has measured it and proved it exists in at least one aircraft./QUOTE]
If that is the case (and I still believe it to be negligible) it is not depicted in the Boeing performance graph that JT provided and claimed proved it's existence. In fact the Boeing graph clearly shows a deceleration prior to even the application of brakes.
[QUOTE]
.. it would appear that one man's hump is another man's horizontal line ?/QUOTE]
In my books a hump is a hump. A horizontal line is when you just fall asleep.
If that is the case (and I still believe it to be negligible) it is not depicted in the Boeing performance graph that JT provided and claimed proved it's existence. In fact the Boeing graph clearly shows a deceleration prior to even the application of brakes.
[QUOTE]
.. it would appear that one man's hump is another man's horizontal line ?/QUOTE]
In my books a hump is a hump. A horizontal line is when you just fall asleep.
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Not really wanting to get back into this, but just for the sake of clarity...
This is a detail of that graph. I have added emphasis lines to show more clearly, vertically, the line that represents "ground run to engine failure recognition", and horizontally, in red, "Takeoff decision speed" and in green, the plane where the vertical "ground run to engine failure recognition" line intersects the acceleration curve.
It should be pretty obvious from this detail that the acceleration curve does not go any higher than the point where it intersects the "ground run to engine failure recognition" line, although of course it does go slightly above the "Takeoff decision speed" line.
So... from this graph, it would appear that acceleration does NOT increase above the point where the failure is recognised.
The only real question in my mind is what kind of acceleration Boeing are talking about, because that looks more like a raw speed curve to me...
Anyway... back into my hole now...
Now whether that is what the graph is trying to tell us, and how much might have been lost in the scanning/copying process, I leave to you...
This is a detail of that graph. I have added emphasis lines to show more clearly, vertically, the line that represents "ground run to engine failure recognition", and horizontally, in red, "Takeoff decision speed" and in green, the plane where the vertical "ground run to engine failure recognition" line intersects the acceleration curve.
It should be pretty obvious from this detail that the acceleration curve does not go any higher than the point where it intersects the "ground run to engine failure recognition" line, although of course it does go slightly above the "Takeoff decision speed" line.
So... from this graph, it would appear that acceleration does NOT increase above the point where the failure is recognised.
The only real question in my mind is what kind of acceleration Boeing are talking about, because that looks more like a raw speed curve to me...
Anyway... back into my hole now...
Now whether that is what the graph is trying to tell us, and how much might have been lost in the scanning/copying process, I leave to you...
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Maybe, but one assumes that it is meant to represent the situation with it's own products... and whichever way you slice it, it simply doesn't show an acceleration past the point of the recognition of the failure.
Do you have any other info on this?
Do you have any other info on this?
Sorry but the certification requirement is that the first action to abort be commenced at V1, engine failure recognition occurs before v1 not after.
The graph might be slightly in error to fit the wording in.
If you recognised an engine had failed after v1 would you stop?
The graph might be slightly in error to fit the wording in.
If you recognised an engine had failed after v1 would you stop?
Last edited by 43Inches; 3rd Apr 2010 at 11:10.
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V1 Efato Emb120
Having undergone Sim training in the Emb120 sim and having experienced an engine failure just after V1 without autofeather operating, I can vouch for the need for prompt and correct actions from the PNF. I would not agree to doing this in the aircraft EVER! My sim buddy and I crashed in the sim trying this the first time.
Using the Sim is cheap if you save lives and a hull and as others have said here you can learn so much more after a couple of sim hours than 2 hours in the aircraft.
Very sad for the families involved. All Emb120 operators should in my opinion use a Sim for EFATO and control malfunctions training. At least Asymmetric flap cannot be simulated in the aircraft, as that is a potential killer too along with windshear and upset recovery.
Using the Sim is cheap if you save lives and a hull and as others have said here you can learn so much more after a couple of sim hours than 2 hours in the aircraft.
Very sad for the families involved. All Emb120 operators should in my opinion use a Sim for EFATO and control malfunctions training. At least Asymmetric flap cannot be simulated in the aircraft, as that is a potential killer too along with windshear and upset recovery.
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As a Type Rated Emb120 pilot with Check & Training approval I can confirm that this aircraft performs very well following an engine failure. If the dead emgine Autofeathers it is all easy and nothing much to do until reaching acceleration altitude. At moderate weights it will climb away at 1500fpm. If it fails to autofeather then the PNF must feather the windmilling (high drag) prop immediately. If it still fails to feather (now it gets nasty) the electric feather pump must be activated immediately. If this is not dome you have very high drag from the dead engine and 1800shp from the good one. Soon you run out of rudder and the aircraft will roll to the dead engine as you are still at a relatively low speed and VMCa now becomes an issue. The rest you can imagine.
Hence my comment that this type of training (all engine failures during/after takeoff and control failures/abnormals ) should only be done in the Sim. This policy is a published international airline standard for good reason.
Hence my comment that this type of training (all engine failures during/after takeoff and control failures/abnormals ) should only be done in the Sim. This policy is a published international airline standard for good reason.