VMC and bank angle/turns
Thread Starter
Join Date: Jan 2013
Location: Bulgaria
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
VMC and bank angle/turns
In the book Aerodynamics for Naval Aviator it says that for each degree of bank angle towards the good engine your Vmc reduces by approximately 3 kts.
That is, banking towards inoperative engine, your Vmc might get pretty high, right?
Reading some VMC theory, I don't get it how VMC changes so much if you bank. I assume that is if you want to maintain straight and level flight, right and it doesn't apply if you want to turn. That is, if after takeoff, climbing at Vy, you are in a turn 30 degrees bank angle and your top engine failed, your VMC is likely above or at actual speed and thus resulting in an out of control scenario? You can't roll level using opposite aileron or you just can't maintain straight and level using that bank angle? I don't get it at all.
Other example, when your engine fails, you may not be able to arrest the initial roll, that means if the airplane rolls, let's say 20 degrees towards the dead engine, when it fails, your actual Vmc equals your actual speed considering this scenario after takeoff when you are usually about 20 kts above published Vmc. So, again you may lose control at all if the bank angle - Vmc relation is correct.
To be more precise, if it fails and because of course you don't have an instant reaction, the airplane reaches a bank angle towards the dead engine, let's say 25 degrees, if VMC rises in this case it will reach a value maybe even above blue line, in this case the recovery is to reduce all the power on the operating engine and to hope you haven't already strike the ground. That's why i'm strugling to figure it out, I think there is a great difference if VMC changes with bank angle in a manner that you can't go back to wings level using opposite aileron. Maybe VMC is just for straight and level i.e. you still have aileron to control the roll and when you reach wings level you can maintain straight and level, but they seem to be coupled yaw/roll loss of control, don't know, just very confused about it.
Actually where I don't get it is if below Vmc you still have control to oppose the roll and to level the wings back or assume the 5 degrees bank into the operative and so reaching again the attitude where you can maintain straight flight. This is what confuses me at all.
To be more precise: you fly at VMC, banked 5 degress towards good engine, you can maintain straight and level flight using this banked 5 degrees attitude and also using full rudder. But let's say you bank 5 degrees towards dead engine because you want to turn in that direction, you don't have anymore rudder if hypotethical you want to assume straight flight using that banked attitude toward the dead engine, but you still have the possibility to roll back towards the good engine and there you have again the authority to maintain straight flight, right? Or I'm wrong and since you left the 5 degrees attitude towards good engine you lose all control and can recover only if you reduce the power on the good engine?
I also watched some videos where in single engine operation, light twins were banked normally during low and slow flight in single engine flying a normal traffic pattern. If so, they would lose control if VMC would be really increased when banking.
This theory also feeds the old never bank into dead engine rule. I'm not a ME rated pilot, but I hope will start my ME training soon, so at least I would like to be ready at least on the theory part of the issue which actually is the one which confuses me.
So what's the truth?
I hope you could follow me. Thank so much!
That is, banking towards inoperative engine, your Vmc might get pretty high, right?
Reading some VMC theory, I don't get it how VMC changes so much if you bank. I assume that is if you want to maintain straight and level flight, right and it doesn't apply if you want to turn. That is, if after takeoff, climbing at Vy, you are in a turn 30 degrees bank angle and your top engine failed, your VMC is likely above or at actual speed and thus resulting in an out of control scenario? You can't roll level using opposite aileron or you just can't maintain straight and level using that bank angle? I don't get it at all.
Other example, when your engine fails, you may not be able to arrest the initial roll, that means if the airplane rolls, let's say 20 degrees towards the dead engine, when it fails, your actual Vmc equals your actual speed considering this scenario after takeoff when you are usually about 20 kts above published Vmc. So, again you may lose control at all if the bank angle - Vmc relation is correct.
To be more precise, if it fails and because of course you don't have an instant reaction, the airplane reaches a bank angle towards the dead engine, let's say 25 degrees, if VMC rises in this case it will reach a value maybe even above blue line, in this case the recovery is to reduce all the power on the operating engine and to hope you haven't already strike the ground. That's why i'm strugling to figure it out, I think there is a great difference if VMC changes with bank angle in a manner that you can't go back to wings level using opposite aileron. Maybe VMC is just for straight and level i.e. you still have aileron to control the roll and when you reach wings level you can maintain straight and level, but they seem to be coupled yaw/roll loss of control, don't know, just very confused about it.
Actually where I don't get it is if below Vmc you still have control to oppose the roll and to level the wings back or assume the 5 degrees bank into the operative and so reaching again the attitude where you can maintain straight flight. This is what confuses me at all.
To be more precise: you fly at VMC, banked 5 degress towards good engine, you can maintain straight and level flight using this banked 5 degrees attitude and also using full rudder. But let's say you bank 5 degrees towards dead engine because you want to turn in that direction, you don't have anymore rudder if hypotethical you want to assume straight flight using that banked attitude toward the dead engine, but you still have the possibility to roll back towards the good engine and there you have again the authority to maintain straight flight, right? Or I'm wrong and since you left the 5 degrees attitude towards good engine you lose all control and can recover only if you reduce the power on the good engine?
I also watched some videos where in single engine operation, light twins were banked normally during low and slow flight in single engine flying a normal traffic pattern. If so, they would lose control if VMC would be really increased when banking.
This theory also feeds the old never bank into dead engine rule. I'm not a ME rated pilot, but I hope will start my ME training soon, so at least I would like to be ready at least on the theory part of the issue which actually is the one which confuses me.
So what's the truth?
I hope you could follow me. Thank so much!
Last edited by RichPa; 5th Feb 2013 at 14:26.
Join Date: Feb 2005
Location: flyover country USA
Age: 82
Posts: 4,579
Likes: 0
Received 0 Likes
on
0 Posts
Offhand, this sounds like its validity is intended toward propeller aircraft. Turning toward the good engine means the prop is accelerating airflow over that wing. Meanwhile the "outer" wing enjoys more airflow due to its being at the outside of the turn.
Thus the Vmca issue is alleviated by the turn into the good engine, and that meshes with the old "dead engine" rule.
Jets - without powerplant exhaust over the wing airfoil - will behave differently; Only the thrust asymmetry drives Vmca.
Thus the Vmca issue is alleviated by the turn into the good engine, and that meshes with the old "dead engine" rule.
Jets - without powerplant exhaust over the wing airfoil - will behave differently; Only the thrust asymmetry drives Vmca.
Join Date: Mar 2011
Location: Canada
Age: 53
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
There's a very detailed study of engine-out flying, here, which might be useful:
Multi-Engine Flying [Ch. 17 of See How It Flies]
Multi-Engine Flying [Ch. 17 of See How It Flies]
Thread Starter
Join Date: Jan 2013
Location: Bulgaria
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Right, the initial question was about Vmca especially regarding light twins, however, any advice on the issue regarding jets or quads or wahtever is appreciated.
Read it almost entirely, but can't figure it out at all.
There's a very detailed study of engine-out flying, here, which might be useful:
Multi-Engine Flying [Ch. 17 of See How It Flies]
Multi-Engine Flying [Ch. 17 of See How It Flies]
Join Date: Oct 2009
Location: UK
Posts: 1,270
Likes: 0
Received 0 Likes
on
0 Posts
Hi RichPa,
There is a good write up about a B707 accident G-APFK, which crashed due to being below VMCA with level wings.
http://www.aaib.gov.uk/cms_resources...8%20G-APFK.pdf
http://www.aaib.gov.uk/cms_resources...K%20Append.pdf
The 707's VMCA increases by 40 kts (from 5 degs bank into live engines) when wings are level .
If you run out of rudder authority the aircraft yaws. On a swept wing aircraft the outside wing develops more lift, and you can run out of aileron authority.
The VMCA is demonstrated with 5 degs bank into the live engines with full rudder and constant heading. The aircraft will show the slip ball out towards the lower wing. Because the C of G is forward of the C of Lift there will be an additional yawing component helping the rudder.
When the wings are level, that additional yawing couple is reduced to zero.
There is a good write up about a B707 accident G-APFK, which crashed due to being below VMCA with level wings.
http://www.aaib.gov.uk/cms_resources...8%20G-APFK.pdf
http://www.aaib.gov.uk/cms_resources...K%20Append.pdf
The 707's VMCA increases by 40 kts (from 5 degs bank into live engines) when wings are level .
If you run out of rudder authority the aircraft yaws. On a swept wing aircraft the outside wing develops more lift, and you can run out of aileron authority.
The VMCA is demonstrated with 5 degs bank into the live engines with full rudder and constant heading. The aircraft will show the slip ball out towards the lower wing. Because the C of G is forward of the C of Lift there will be an additional yawing component helping the rudder.
When the wings are level, that additional yawing couple is reduced to zero.
Join Date: Jun 2001
Location: Australia
Posts: 889
Likes: 0
Received 0 Likes
on
0 Posts
Hi RichPa.
There is some good stuff above, including the "see how it flies" reference. But don't be distracted by the jets vs. turboprop argument at this stage.
Vmc depends on slip, among other things. The way a pilot adjusts slip in straight flight is by adjusting bank angle while preventing yaw with rudder. The ball will move while doing this. But if you adjust bank for a turn while simultaneously moving the rudder to keep slip constant (so the ball does not move), Vmc won't change much. This means that, for small angles of bank, pilots can turn in either direction without losing control. The important thing is to keep the ball in the correct place!
When books talk about minimising Vmc by maintaining e.g. 5* angle of bank, they are talking about straight flight. So the trick is to look at the ball when in that state, and keep the ball precisely in that position from then on. Turning will cost climb performance, but you won't lose directional control if you control value of slip for a given airspeed.
There is some good stuff above, including the "see how it flies" reference. But don't be distracted by the jets vs. turboprop argument at this stage.
Vmc depends on slip, among other things. The way a pilot adjusts slip in straight flight is by adjusting bank angle while preventing yaw with rudder. The ball will move while doing this. But if you adjust bank for a turn while simultaneously moving the rudder to keep slip constant (so the ball does not move), Vmc won't change much. This means that, for small angles of bank, pilots can turn in either direction without losing control. The important thing is to keep the ball in the correct place!
When books talk about minimising Vmc by maintaining e.g. 5* angle of bank, they are talking about straight flight. So the trick is to look at the ball when in that state, and keep the ball precisely in that position from then on. Turning will cost climb performance, but you won't lose directional control if you control value of slip for a given airspeed.
Last edited by Oktas8; 5th Feb 2013 at 19:52.
Moderator
I think Oktas8 has the story in a reasonable manner.
each degree of bank angle towards the good engine your Vmc reduces by approximately 3 kts
In the right ballpark.
That is, banking towards inoperative engine, your Vmc might get pretty high, right?
Indeed. Banking the wrong way, typically, sees deltas in the 30-40 kt range ... which is why, if you really must be back someone near Vmc, you need to get some favourable bank into the equation VERY promptly .. lest you see the world from an unusual vantage point.
Reading some VMC theory, I don't get it how VMC changes so much if you bank.
Wings level, there will be a residual slip OEI. This can be increased/reduced/removed/made to go the other side according to what bank angle is applied.
Why is slip important ? -
(a) too much might end up putting you in a departure situation and subsequent spin, ergo, let's keep it under some sort of constraint
(b) slip will improve/reduce directional control (ie help/hinder rudder activity) depending from which side the slip happens to come, ie, slip will produce a turning moment in the direction of the slip angle ("further effect of controls" comes to mind from basic training).
(c) wings level, we start with slip towards the dead engine. This is due to the rudder's causing an unbalanced side force .. which accelerates the aircraft slightly to the side ... resulting in a slip in that direction ie the wind now comes from a direction slightly to the dead side of straight ahead
(d) if you were to put full rudder in .. then you can cause yawing in either direction by slip control. I'm not recommending this but, hopefully, you get the idea, ergo, Vmc is VERY sensitive to slip angle (which we, roughly, relate to bank angle)
(e) different consideration to performing a reasonably balanced turn where the slip is kept well under control
in this case the recovery is to reduce all the power on the operating engine and to hope you haven't already strike the ground
Important points to keep in mind for if you get yourself into that situation.
you can't go back to wings level using opposite aileron
That will depend on Type and circumstances on the day. Better to keep a healthy margin above Vmc and leave that regime of flight to the test pilot folks.
Generally, Vmc is determined statically (a bit like the endorsement Vmc demo) and then checked for dynamic effects. Result is that a competent pilot ought to be able to keep the aircraft blue side up and recover to a sensible flight condition
if below Vmc you still have control to oppose the roll and to level the wings back or assume the 5 degrees bank into the operative and so reaching again the attitude where you can maintain straight flight.
Below Vmc you will have great difficulty with directional control at high thrust .. which will cause some difficulty with roll control. Just what you can or can't do, roll-wise, will be Type specific
The 5° limit is a certification consideration. If you happen to be back in real Vmc territory, anticipate that you will need this bank to make things work .. otherwise the real Vmc will vary. Vmc is about not losing control .. climb capability is quite secondary. Once you get back to a speed where climb might be feasible, a bank angle of around 2-3° generally results in the best compromise for climb performance.
I think you mean Vmca
Same deal .. evolving acronyms
Thus the Vmca issue is alleviated by the turn into the good engine, and that meshes with the old "dead engine" rule
Not quite. Vmc is still waiting in the wings to bite you on the tail. However, it is reasonable to opine that things might get away from the pilot more readily with a turn towards the dead engine in the event of mishandling etc. It follows that risk management considerations might dictate the preference to turn to the live engine.
each degree of bank angle towards the good engine your Vmc reduces by approximately 3 kts
In the right ballpark.
That is, banking towards inoperative engine, your Vmc might get pretty high, right?
Indeed. Banking the wrong way, typically, sees deltas in the 30-40 kt range ... which is why, if you really must be back someone near Vmc, you need to get some favourable bank into the equation VERY promptly .. lest you see the world from an unusual vantage point.
Reading some VMC theory, I don't get it how VMC changes so much if you bank.
Wings level, there will be a residual slip OEI. This can be increased/reduced/removed/made to go the other side according to what bank angle is applied.
Why is slip important ? -
(a) too much might end up putting you in a departure situation and subsequent spin, ergo, let's keep it under some sort of constraint
(b) slip will improve/reduce directional control (ie help/hinder rudder activity) depending from which side the slip happens to come, ie, slip will produce a turning moment in the direction of the slip angle ("further effect of controls" comes to mind from basic training).
(c) wings level, we start with slip towards the dead engine. This is due to the rudder's causing an unbalanced side force .. which accelerates the aircraft slightly to the side ... resulting in a slip in that direction ie the wind now comes from a direction slightly to the dead side of straight ahead
(d) if you were to put full rudder in .. then you can cause yawing in either direction by slip control. I'm not recommending this but, hopefully, you get the idea, ergo, Vmc is VERY sensitive to slip angle (which we, roughly, relate to bank angle)
(e) different consideration to performing a reasonably balanced turn where the slip is kept well under control
in this case the recovery is to reduce all the power on the operating engine and to hope you haven't already strike the ground
Important points to keep in mind for if you get yourself into that situation.
you can't go back to wings level using opposite aileron
That will depend on Type and circumstances on the day. Better to keep a healthy margin above Vmc and leave that regime of flight to the test pilot folks.
Generally, Vmc is determined statically (a bit like the endorsement Vmc demo) and then checked for dynamic effects. Result is that a competent pilot ought to be able to keep the aircraft blue side up and recover to a sensible flight condition
if below Vmc you still have control to oppose the roll and to level the wings back or assume the 5 degrees bank into the operative and so reaching again the attitude where you can maintain straight flight.
Below Vmc you will have great difficulty with directional control at high thrust .. which will cause some difficulty with roll control. Just what you can or can't do, roll-wise, will be Type specific
The 5° limit is a certification consideration. If you happen to be back in real Vmc territory, anticipate that you will need this bank to make things work .. otherwise the real Vmc will vary. Vmc is about not losing control .. climb capability is quite secondary. Once you get back to a speed where climb might be feasible, a bank angle of around 2-3° generally results in the best compromise for climb performance.
I think you mean Vmca
Same deal .. evolving acronyms
Thus the Vmca issue is alleviated by the turn into the good engine, and that meshes with the old "dead engine" rule
Not quite. Vmc is still waiting in the wings to bite you on the tail. However, it is reasonable to opine that things might get away from the pilot more readily with a turn towards the dead engine in the event of mishandling etc. It follows that risk management considerations might dictate the preference to turn to the live engine.
Thread Starter
Join Date: Jan 2013
Location: Bulgaria
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
The way a pilot adjusts slip in straight flight is by adjusting bank angle while preventing yaw with rudder. The ball will move while doing this. But if you adjust bank for a turn while simultaneously moving the rudder to keep slip constant (so the ball does not move), Vmc won't change much. This means that, for small angles of bank, pilots can turn in either direction without losing control. The important thing is to keep the ball in the correct place!
That is even in turns you have to keep the ball at the same recommended position for zero-slip which is usually 1/2 ball width into the operative engine side, right? But can you do that in a turn towards the dead engine? I figure out you need more rudder to keep it during turn and if you already were close to Vmc you are close to rudder stop, so, is it possible to do these turns without losing control?
Basically what I want to figure out is if I'm flying 5 kts above Vmc and banking (i.e. moderate bank 30 degrees, no need to do aerobatics on one engine
) the airplane to turn either direction, towards dead or live engine, does Vmc stays the same? Am I able to do that without loss of control due to reaching aileron and rudder stops?
P.S. Read that 707 report and it is said somewhere that even if reaching Vmc, there was still some aileron control to return to wings level or 5 deg toward the live engine and so regaining straight flight, however, it was not applied during that incident.
Still doesn't make sense, for example, another thought on the issue: when the engine fails during takeoff, you are WINGS LEVEL and Vmc is calculated for 5 degrees bank toward dead engine. If so, the Vmc value it is useless because you are in the best case wings level, even not thinking about the fact that usually you get a roll towards dead engine when it fails, so you are actually more than wings level, you are in the best case banked a little towards dead engine, so Vmc would be really high in this case, and if Vmc=loss of control at all, i.e. even roll loss of control, if so, every takeoff would be fatal when you lose one engine. So, it can't be as I figure out. It makes me think that you lose just the ability to maintain a straight track, i.e. rwy centerline during takeoff, but not the ability to roll the aircraft.
That is even in turns you have to keep the ball at the same recommended position for zero-slip which is usually 1/2 ball width into the operative engine side, right? But can you do that in a turn towards the dead engine? I figure out you need more rudder to keep it during turn and if you already were close to Vmc you are close to rudder stop, so, is it possible to do these turns without losing control?
Basically what I want to figure out is if I'm flying 5 kts above Vmc and banking (i.e. moderate bank 30 degrees, no need to do aerobatics on one engine
) the airplane to turn either direction, towards dead or live engine, does Vmc stays the same? Am I able to do that without loss of control due to reaching aileron and rudder stops?P.S. Read that 707 report and it is said somewhere that even if reaching Vmc, there was still some aileron control to return to wings level or 5 deg toward the live engine and so regaining straight flight, however, it was not applied during that incident.
Still doesn't make sense, for example, another thought on the issue: when the engine fails during takeoff, you are WINGS LEVEL and Vmc is calculated for 5 degrees bank toward dead engine. If so, the Vmc value it is useless because you are in the best case wings level, even not thinking about the fact that usually you get a roll towards dead engine when it fails, so you are actually more than wings level, you are in the best case banked a little towards dead engine, so Vmc would be really high in this case, and if Vmc=loss of control at all, i.e. even roll loss of control, if so, every takeoff would be fatal when you lose one engine. So, it can't be as I figure out. It makes me think that you lose just the ability to maintain a straight track, i.e. rwy centerline during takeoff, but not the ability to roll the aircraft.
Last edited by RichPa; 6th Feb 2013 at 11:38.
Join Date: Oct 2009
Location: UK
Posts: 1,270
Likes: 0
Received 0 Likes
on
0 Posts
Hi ,
Correct.
In order to maintain a constant heading at VMCA, you'll need bank into the live engines.
The danger is if you attempt to fly wings level with the ball centered, you may run out of aileron control.
This problem will only occur at very light weights, when V2min = VMCA (or during the GA from an approach when VAPP = VMCL (VMCA in Landing Configuration))
It makes me think that you lose just the ability to maintain a straight track ... but not the ability to roll the aircraft.
In order to maintain a constant heading at VMCA, you'll need bank into the live engines.
The danger is if you attempt to fly wings level with the ball centered, you may run out of aileron control.
This problem will only occur at very light weights, when V2min = VMCA (or during the GA from an approach when VAPP = VMCL (VMCA in Landing Configuration))
Last edited by rudderrudderrat; 6th Feb 2013 at 12:08. Reason: punctuation
Thread Starter
Join Date: Jan 2013
Location: Bulgaria
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
The danger is if you attempt to fly wings level with the ball centered, you may run out of aileron control.
The problem is that you are wings level when the engine failed. You don't attempt voluntary to fly like that after the engine failed. You are wings level because that is the attitude during takeoff. More than that, you get a roll when it fails, so in the best case you are wings level. So how to bank 5 degrees towards live engine to assume best attitude for Vmca if you don't have enough aileron authority?> It seems like a vicious circle or like a trap.
The problem is that you are wings level when the engine failed. You don't attempt voluntary to fly like that after the engine failed. You are wings level because that is the attitude during takeoff. More than that, you get a roll when it fails, so in the best case you are wings level. So how to bank 5 degrees towards live engine to assume best attitude for Vmca if you don't have enough aileron authority?>
It seems like a vicious circle or like a trap.
Last edited by RichPa; 6th Feb 2013 at 12:58.
Join Date: Oct 2009
Location: UK
Posts: 1,270
Likes: 0
Received 0 Likes
on
0 Posts
Hi RichPa,
Then you would simply apply more (full) rudder until you could centralise the ailerons. Since the heading will be changing (with the wings level), then you'd roll in bank towards the live engines, and end up with a constant 5 degs bank to maintain heading and have the ailerons centered.
if you don't have enough aileron authority?
Thread Starter
Join Date: Jan 2013
Location: Bulgaria
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Then you would simply apply more (full) rudder until you could centralise the ailerons.
Yes, but I thought you are reached at full rudder considering you are below (actual) Vmc (which is increased due to the fact that you are banked towards the dead engine.)
Yes, but I thought you are reached at full rudder considering you are below (actual) Vmc (which is increased due to the fact that you are banked towards the dead engine.)
Moderator
Some more thoughts ..
I figure out you need more rudder to keep it during turn and if you already were close to Vmc you are close to rudder stop, so, is it possible to do these turns without losing control?
There'll be a degree of Type specific behaviour involved.
if I'm flying 5 kts above Vmc and banking (i.e. moderate bank 30 degrees, no need to do aerobatics on one engine )
Suggest that is not a good idea. Until you are at normal OEI speeds, bank should be constrained significantly. 10-15° is a suitable ballpark. Too much risk of letting things get away from you at large bank angles.
even if reaching Vmc, there was still some aileron control to return to wings level or 5 deg toward the live engine and so regaining straight flight,
Should generally be the case. The main problem is that, in the few knots near Vmc, things may happen very quickly and, unless the pilot is right on the ball, the risk of departure is high. Back near Vmc, the pilot's immediate actions in the event of failure must include a rapid introduction of some favourable bank.
if Vmc=loss of control at all, i.e. even roll loss of control, if so, every takeoff would be fatal when you lose one engine.
Vmc doesn't necessarily infer loss of control. Rather a competent pilot should be able to control the aircraft within prescribed parameters. Further, it is usual to have a modest margin above Vmc for the min speed takeoff speed schedule. What this all means is
(a) there is NO time to play Monday morning quarterback in the cockpit. Actions need to be well rehearsed and very prompt.
(b) at the very light weights required for min speed schedules, aeroplane acceleration is very high during the failure rundown
(c) the need is for rapid and aggressive pilot control inputs to prevent the situation getting to a point where things do become irrecoverable.
(c) the aeroplane at higher speed schedules (higher weight or overspeed) is a comparative pussycat. At min speed, aft CG, etc., the pussycat very rapidly becomes a raging tiger ..
One of my worries is the case where pilots are not trained in min speed schedule failures, routinely fly (and train) at overspeed, and then (occasionally) are required to fly from airports requiring min speed protocols. As I have seen in the sim environment .. an eye-opening occurrence if the failure is introduced for the latter circumstance. Comparatively easy to train out the problems but, if that is not done, the first real life event, potentially, may be catastrophic due to startle factor time delays.
you lose just the ability to maintain a straight track, i.e. rwy centerline during takeoff, but not the ability to roll the aircraft.
Things are not quite that bad.
Failure will involve yaw .. which can be controlled. Lower skill levels will see drift .. which can be controlled with bank. A modicum of roll control should remain. The pivotal consideration is skill level and that comes down to training to task. There is no room for figuring out what one needs to do at the time .. the responses must be automatic, instinctive, and rapid.
It is not overly difficult, with training, to have a min speed schedule V1 failure and track out accurately.
For instance, my training technique for this was to have the student progressively work up to a nil, or near-nil, vis takeoff, min weight, min speed, max aft CG, worst failure the box had programmed, then have the failure shortly after VR (ie during the rotation flare with nil vis reference), and track out on the LLZ. A few practice runs and, with aggressive initial control inputs, it would work out reasonably well. Great confidence builder when the student then could recover via a hand flown, raw data, landing in 0/0 conditions. The environment would get a tad sweaty but it was all in good humour. Of course, this all required a VERY good standard of I/F scan and manipulation ... that was eminently trainable in the sim, even for 200 hour cadet folks.
So how to bank 5 degrees towards live engine to assume best attitude for Vmca if you don't have enough aileron authority?
There should be adequate roll control left to do that. However, the essence is time .. back at (or close to) Vmc, the pilot just does not have the luxury of scratching his beard for a bit while contemplating the situation during a failure .. the response must be automatic.
Yes, but I thought you are reached at full rudder considering you are below (actual) Vmc (which is increased due to the fact that you are banked towards the dead engine.)
Keep in mind that bank is largely for static considerations and the effect of slip angles. You are having some difficulty separating static and dynamic matters as well as time lags for inertial things to start happening.
The Air North mishap thread is worth a read. More importantly, the BASI animation in the report is very sobering .. (click on the AVI hyperlink under "Related Files".)
I figure out you need more rudder to keep it during turn and if you already were close to Vmc you are close to rudder stop, so, is it possible to do these turns without losing control?
There'll be a degree of Type specific behaviour involved.
if I'm flying 5 kts above Vmc and banking (i.e. moderate bank 30 degrees, no need to do aerobatics on one engine
) Suggest that is not a good idea. Until you are at normal OEI speeds, bank should be constrained significantly. 10-15° is a suitable ballpark. Too much risk of letting things get away from you at large bank angles.
even if reaching Vmc, there was still some aileron control to return to wings level or 5 deg toward the live engine and so regaining straight flight,
Should generally be the case. The main problem is that, in the few knots near Vmc, things may happen very quickly and, unless the pilot is right on the ball, the risk of departure is high. Back near Vmc, the pilot's immediate actions in the event of failure must include a rapid introduction of some favourable bank.
if Vmc=loss of control at all, i.e. even roll loss of control, if so, every takeoff would be fatal when you lose one engine.
Vmc doesn't necessarily infer loss of control. Rather a competent pilot should be able to control the aircraft within prescribed parameters. Further, it is usual to have a modest margin above Vmc for the min speed takeoff speed schedule. What this all means is
(a) there is NO time to play Monday morning quarterback in the cockpit. Actions need to be well rehearsed and very prompt.
(b) at the very light weights required for min speed schedules, aeroplane acceleration is very high during the failure rundown
(c) the need is for rapid and aggressive pilot control inputs to prevent the situation getting to a point where things do become irrecoverable.
(c) the aeroplane at higher speed schedules (higher weight or overspeed) is a comparative pussycat. At min speed, aft CG, etc., the pussycat very rapidly becomes a raging tiger ..
One of my worries is the case where pilots are not trained in min speed schedule failures, routinely fly (and train) at overspeed, and then (occasionally) are required to fly from airports requiring min speed protocols. As I have seen in the sim environment .. an eye-opening occurrence if the failure is introduced for the latter circumstance. Comparatively easy to train out the problems but, if that is not done, the first real life event, potentially, may be catastrophic due to startle factor time delays.
you lose just the ability to maintain a straight track, i.e. rwy centerline during takeoff, but not the ability to roll the aircraft.
Things are not quite that bad.
Failure will involve yaw .. which can be controlled. Lower skill levels will see drift .. which can be controlled with bank. A modicum of roll control should remain. The pivotal consideration is skill level and that comes down to training to task. There is no room for figuring out what one needs to do at the time .. the responses must be automatic, instinctive, and rapid.
It is not overly difficult, with training, to have a min speed schedule V1 failure and track out accurately.
For instance, my training technique for this was to have the student progressively work up to a nil, or near-nil, vis takeoff, min weight, min speed, max aft CG, worst failure the box had programmed, then have the failure shortly after VR (ie during the rotation flare with nil vis reference), and track out on the LLZ. A few practice runs and, with aggressive initial control inputs, it would work out reasonably well. Great confidence builder when the student then could recover via a hand flown, raw data, landing in 0/0 conditions. The environment would get a tad sweaty but it was all in good humour. Of course, this all required a VERY good standard of I/F scan and manipulation ... that was eminently trainable in the sim, even for 200 hour cadet folks.
So how to bank 5 degrees towards live engine to assume best attitude for Vmca if you don't have enough aileron authority?
There should be adequate roll control left to do that. However, the essence is time .. back at (or close to) Vmc, the pilot just does not have the luxury of scratching his beard for a bit while contemplating the situation during a failure .. the response must be automatic.
Yes, but I thought you are reached at full rudder considering you are below (actual) Vmc (which is increased due to the fact that you are banked towards the dead engine.)
Keep in mind that bank is largely for static considerations and the effect of slip angles. You are having some difficulty separating static and dynamic matters as well as time lags for inertial things to start happening.
The Air North mishap thread is worth a read. More importantly, the BASI animation in the report is very sobering .. (click on the AVI hyperlink under "Related Files".)
Join Date: Jan 2012
Location: Not far from the edge of the Milky Way Galaxy in the Orion Arm.
Posts: 510
Likes: 0
Received 0 Likes
on
0 Posts
dying engine during a bank?
Would immediate instinct not make you push forward (a bit, enough) whilst applying left rudder and rolling into the live enginey, screw into the dead engine with - rudder and aileron and lower pitch and power (when you are finally leaning towards the live engine)
(lower pitch leads slightly) ie., fly it in (to S&L) albeit momentarily, assuming you are destined to maintain this horrible turn - like a chunk of rock after t/o needs to be got around. My little point here is to regain perf, you can always get back to banking on one engine, with decidedly more welly (perf) notwithstanding the rock. [ and the terrain below]
Scuze, typical baby lingo - but nobody mentioned pitch forward as you all seemed to be very interested in VMC and the like.
The tendency of the X-box to never exceed x amount of bank angle and within 1g and restricted bank angle after EO sometimes, really does drive home the point that this little baby can`t fly as we can, where sometimes tentative bank angles just won`t cook it [put the aircraft where it needs to be - in this case, away from said rock] and a hands on approach must be the most sensible way.
Not advocating overbanking in the slightest - but, I once had a demo once (not in an A320 full of pax) whereby an engine on this aircraft the, Piper Apache, was cut and we proceeded to do advance turns all over the sky - we were about 5 or six pob, two of whom were fatb
ards The point the instructor was no doubt trying to make is that: most things fly really well even on one engine.
By the way, the aircraft did not falter, shudder, scream the stall warner or anything, it just flew.
My point is obvious: but if not,,,, often a pilot will tread so gingerly as not to make full use of the flying controls in that new terrifying config!! when in fact that is just what is needed, some extra welly on the flying controls.
This also goes for those who complain that they `only just made the takeoff . . ` ` and when asked if they had full elevator, they replied` no`
At slow speeds, greater deflection of the flying control surfaces is what is required. I know you all know this from baby school, and yet, there are many pilots who will simply not apply more than usual flying control when necessary, don`t be shy. You are not flying a performance graph (thank God!) If, if, there would be no response from the max effort you are putting in on the controls, either at all or eventually, then (notwithstanding things you can do with thrust from the engines) you are having a bad day - but until that point, ask of "it" what you want - you are the Driver, the creator of lift and the core reason why the thing is flying in the first place - don`t give up - there is more left in the thing than you are perhaps trained to believe.
and to prove a point; I once flew with a trainee an engine out approach, very nice. coming over the hedge however - floating over the numbers, and heading away from the runway the flying thang had run out of anything close to flying characteristics and well, speed off the clock, the aircraft was re-aligned with the centreline and brought to a neat little touchdown. Why not a go around you ask? Well, at that late stage in the game, a go around would have been a tad interesting.
(lower pitch leads slightly) ie., fly it in (to S&L) albeit momentarily, assuming you are destined to maintain this horrible turn - like a chunk of rock after t/o needs to be got around. My little point here is to regain perf, you can always get back to banking on one engine, with decidedly more welly (perf) notwithstanding the rock. [ and the terrain below]
Scuze, typical baby lingo - but nobody mentioned pitch forward as you all seemed to be very interested in VMC and the like.
The tendency of the X-box to never exceed x amount of bank angle and within 1g and restricted bank angle after EO sometimes, really does drive home the point that this little baby can`t fly as we can, where sometimes tentative bank angles just won`t cook it [put the aircraft where it needs to be - in this case, away from said rock] and a hands on approach must be the most sensible way.
Not advocating overbanking in the slightest - but, I once had a demo once (not in an A320 full of pax) whereby an engine on this aircraft the, Piper Apache, was cut and we proceeded to do advance turns all over the sky - we were about 5 or six pob, two of whom were fatb
ards The point the instructor was no doubt trying to make is that: most things fly really well even on one engine.By the way, the aircraft did not falter, shudder, scream the stall warner or anything, it just flew.
My point is obvious: but if not,,,, often a pilot will tread so gingerly as not to make full use of the flying controls in that new terrifying config!! when in fact that is just what is needed, some extra welly on the flying controls.
This also goes for those who complain that they `only just made the takeoff . . ` ` and when asked if they had full elevator, they replied` no`
At slow speeds, greater deflection of the flying control surfaces is what is required. I know you all know this from baby school, and yet, there are many pilots who will simply not apply more than usual flying control when necessary, don`t be shy. You are not flying a performance graph (thank God!) If, if, there would be no response from the max effort you are putting in on the controls, either at all or eventually, then (notwithstanding things you can do with thrust from the engines) you are having a bad day - but until that point, ask of "it" what you want - you are the Driver, the creator of lift and the core reason why the thing is flying in the first place - don`t give up - there is more left in the thing than you are perhaps trained to believe.
and to prove a point; I once flew with a trainee an engine out approach, very nice. coming over the hedge however - floating over the numbers, and heading away from the runway the flying thang had run out of anything close to flying characteristics and well, speed off the clock, the aircraft was re-aligned with the centreline and brought to a neat little touchdown. Why not a go around you ask? Well, at that late stage in the game, a go around would have been a tad interesting.
Last edited by Natstrackalpha; 11th Feb 2013 at 19:59.
