Light twin asymmetric decision heights
Thread Starter
Light twin asymmetric decision heights
Anywhere between 500 and 300 ft agl appears to be popular dogma taught in flying schools. There are no decision height figures in the various POH that I have read - just a caution in some to avoid going around on one engine where possible.
That's fine - but chances are that you might have to do a one engine feathered go-around due a myriad of reasons. Which is why landing with one prop feathered is a high risk training exercise.
From a full flap Vref go-around, a reasonably competent pilot can go around successfully from 200 ft and lose 100 ft in the clean up procedure. No different from an engine failing at 100 ft after take-off except the prop is already feathered.
Would you really truly honestly deliberately elect to crash the aircraft straight ahead if the choice was a go-around or not, below a decision height of 3-500 ft in a Seminole, Baron, Chieftain or what have you? Because that is what is taught as dogma in many flying schools.
Surely the decision to execute a single engine go-around depends on variables such as current airspeed, how much flap is down if any, density altitude, pilot proficiency and so on. Teaching absolutes in these matters makes it easy for the instructor to wash his hands and put the subject into the too hard tray.
Meanwhile reasoned argument on the subject is avoided and the student (or experienced pilot) is left wondering if maybe it is just possible to carry out a successful go-around below a flying school stated decision height, with the flaps already up for example.
Any discussion on the matter is welcome to this writer.
That's fine - but chances are that you might have to do a one engine feathered go-around due a myriad of reasons. Which is why landing with one prop feathered is a high risk training exercise.
From a full flap Vref go-around, a reasonably competent pilot can go around successfully from 200 ft and lose 100 ft in the clean up procedure. No different from an engine failing at 100 ft after take-off except the prop is already feathered.
Would you really truly honestly deliberately elect to crash the aircraft straight ahead if the choice was a go-around or not, below a decision height of 3-500 ft in a Seminole, Baron, Chieftain or what have you? Because that is what is taught as dogma in many flying schools.
Surely the decision to execute a single engine go-around depends on variables such as current airspeed, how much flap is down if any, density altitude, pilot proficiency and so on. Teaching absolutes in these matters makes it easy for the instructor to wash his hands and put the subject into the too hard tray.
Meanwhile reasoned argument on the subject is avoided and the student (or experienced pilot) is left wondering if maybe it is just possible to carry out a successful go-around below a flying school stated decision height, with the flaps already up for example.
Any discussion on the matter is welcome to this writer.
Confectionary Transfer Technician
Join Date: May 2001
Location: South Island
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
I teach it in a Seneca & a Courger, I get them to come in with only 10 degrees till the decision height which we use 300 feet, if you aren't happy then go around, then if happy put in the seneca put the 2nd notch down ( 25 degrees). Once that 25 degrees is down & with the gear out even if you went to full power you would still have to lose height simply because the hourse power required curve is above the hourse power available curve till you get rid of the flap.
I wouldnt call myself a flying school mushroom
at all , if theres two ways to skin the cat, I'll look for a third.
But if I was in the real deal one engine feathered, in the planes I fly if you are much below 300 ft you are committed to landing no matter what, not sure bout the bigger boys
But also remember, better to go thru the end fence slowly & live rather than try to do a go-around from 100 ft, ****** it up, smash it in & kill your self, just a thought.
I wouldnt call myself a flying school mushroom
at all , if theres two ways to skin the cat, I'll look for a third.But if I was in the real deal one engine feathered, in the planes I fly if you are much below 300 ft you are committed to landing no matter what, not sure bout the bigger boys
But also remember, better to go thru the end fence slowly & live rather than try to do a go-around from 100 ft, ****** it up, smash it in & kill your self, just a thought.
Confectionary Transfer Technician
Join Date: May 2001
Location: South Island
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
Also just another thought, if In doubt go up to 3500 feet, feather the engine, real or just symulated, go down to 3300 feet ( hard deck of 3000 ) & see how much height you lose doing the go aorund from the simulated 300 ft.
Join Date: Mar 2002
Location: san diego
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
in the majority of scenarios i have experienced no more than 1st stage of flap should be selected "until landing is assured" then and only then should you put down the last stages of flap any earlier and they could prove to be the nail in your coffin -remember the lift drag demo?
Moderator
This one is always going to be a vexed subject for which there are few satisfactory "canned" solutions.
I presume that Centaurus' question is directed at the typical light twin training or similar situation.
There is no certification requirement for a basic normal category twin to demonstrate or possess any OEI missed approach capability. With gear and flap down, except under the most favourable conditions, the only reasonable expectation is that the aircraft is going to keep going down. If the pilot wishes to do something different, then he/she will have to take positive steps to improve the drag situation and turn the approach into something similar to a takeoff .. ie a missed approach.
The manufacturer is not going to be so silly as to put too much in the POH due to the potential for a litigation field day. In general I suggest that it is a reasonable assessment to presume that the manufacturer will include only that which is necessary from either a legal or commercial viewpoint. Hoping for useful, competent hangar talk over and above the minimum ... while understandable .. is a bit optimistic.
This leaves the pilot with not too many reasonable options during the OEI approach.
Presuming a satisfactory level of manipulative competence on the part of the particular pilot, the main problem relates to assessing a reasonable decision height (ie whatever height on the day the pilot considers to be the lowest for which the combination of the aircraft's and his/her own capabilities to execute a successful OEI missed approach is reasonably anticipated).
Perhaps the aircraft owner (or flying school) has a reasonable case for dictating a policy minimum decision height ... you don't like my decision height policy .. you get your aircraft from someone else. Certainly, history suggests that there is a high probability for less competent pilots to get themselves into missed approach difficulties, especially the Vmca departure crash-burn-die scenario, if the situation becomes too critical from a manipulative point of view. Of course, regardless of competence, there comes a point (height) where the aircraft cannot be flown successfully through a missed approach in many cases and a landing as best as can be effected might be the preferable decision.
In the absence of some dreadful imperative requiring a landing regardless of other considerations, it would be silly for the pilot to continue an OEI approach below his/her decision height unless the probability of requiring a missed approach was very, very small.
One can do a variety of things to improve the situation ...
(a) consider the possible advantages of a diversion to a better airport/runway
(b) declare an emergency to maximise assistance and co-operation (essential),
(c) negotiate with other traffic, etc, in an OCTA environment
(d) hold until whatever adverse conditions abate somewhat ?
(e) if the runway distance is adequate and the aircraft handling acceptable, consider conducting the approach with reduced or nil flap.
(f) perhaps one might even consider a higher approach path to a mentally displaced threshold if the runway is of substantial length ?
(g) consistent with handling considerations and available runway length, consider approaching with a measure of additional speed appropriate to the aircraft. In a favourable situation (ie long runway), this might result in an approach with nil flap and at a speed approximating blue line, the combination of which greatly simplifies the missed approach transition.
Perhaps other posters can add to this list those considerations which I have undoubtedly overlooked ?
My concern would be with the pilot who didn't think about any of these matters but merely gave it a go and hoped for the best ....
I presume that Centaurus' question is directed at the typical light twin training or similar situation.
There is no certification requirement for a basic normal category twin to demonstrate or possess any OEI missed approach capability. With gear and flap down, except under the most favourable conditions, the only reasonable expectation is that the aircraft is going to keep going down. If the pilot wishes to do something different, then he/she will have to take positive steps to improve the drag situation and turn the approach into something similar to a takeoff .. ie a missed approach.
The manufacturer is not going to be so silly as to put too much in the POH due to the potential for a litigation field day. In general I suggest that it is a reasonable assessment to presume that the manufacturer will include only that which is necessary from either a legal or commercial viewpoint. Hoping for useful, competent hangar talk over and above the minimum ... while understandable .. is a bit optimistic.
This leaves the pilot with not too many reasonable options during the OEI approach.
Presuming a satisfactory level of manipulative competence on the part of the particular pilot, the main problem relates to assessing a reasonable decision height (ie whatever height on the day the pilot considers to be the lowest for which the combination of the aircraft's and his/her own capabilities to execute a successful OEI missed approach is reasonably anticipated).
Perhaps the aircraft owner (or flying school) has a reasonable case for dictating a policy minimum decision height ... you don't like my decision height policy .. you get your aircraft from someone else. Certainly, history suggests that there is a high probability for less competent pilots to get themselves into missed approach difficulties, especially the Vmca departure crash-burn-die scenario, if the situation becomes too critical from a manipulative point of view. Of course, regardless of competence, there comes a point (height) where the aircraft cannot be flown successfully through a missed approach in many cases and a landing as best as can be effected might be the preferable decision.
In the absence of some dreadful imperative requiring a landing regardless of other considerations, it would be silly for the pilot to continue an OEI approach below his/her decision height unless the probability of requiring a missed approach was very, very small.
One can do a variety of things to improve the situation ...
(a) consider the possible advantages of a diversion to a better airport/runway
(b) declare an emergency to maximise assistance and co-operation (essential),
(c) negotiate with other traffic, etc, in an OCTA environment
(d) hold until whatever adverse conditions abate somewhat ?
(e) if the runway distance is adequate and the aircraft handling acceptable, consider conducting the approach with reduced or nil flap.
(f) perhaps one might even consider a higher approach path to a mentally displaced threshold if the runway is of substantial length ?
(g) consistent with handling considerations and available runway length, consider approaching with a measure of additional speed appropriate to the aircraft. In a favourable situation (ie long runway), this might result in an approach with nil flap and at a speed approximating blue line, the combination of which greatly simplifies the missed approach transition.
Perhaps other posters can add to this list those considerations which I have undoubtedly overlooked ?
My concern would be with the pilot who didn't think about any of these matters but merely gave it a go and hoped for the best ....
Last edited by john_tullamarine; 3rd Apr 2002 at 05:45.
This is definately a curly one...
I certainly don't agree that...
On one engine.
I strongly agree with Blue Line. Go and try this at altitude to see the result and remember the weight difference.
I certainly don't agree that...
...a reasonably competent pilot can go around successfully from 200 ft and lose 100 ft in the clean up procedure.
I strongly agree with Blue Line. Go and try this at altitude to see the result and remember the weight difference.
Some aircraft, the Barron 58 specifically prohibit doing an asyymetric go-around after full flap is selected. Asymmetric roll here is the problem, insufficient aileron authority prefents the roll leading to a loss of control.
I demo this in a Duchess on initial multi endorsements, lots of aileron to keep the roll under control while cleaning up, usually takes 200' to 300' feet alt loss before any climb is achieved.
I demo this in a Duchess on initial multi endorsements, lots of aileron to keep the roll under control while cleaning up, usually takes 200' to 300' feet alt loss before any climb is achieved.
Join Date: Jan 2002
Location: Melbourne
Posts: 102
Likes: 0
Received 0 Likes
on
0 Posts
This subject has stirred debate for many years. How many instructors actually carry out engine out landing practice with one actually feathered? Should this be left to practice at an appropriate altitude rather than in the circuit where an error in judgement can create a greater risk factor.
The age and condition of our aircraft should also be taken into consideration as how many will actually be capable of a missed approach at Maximum Take-off Weight? A colleague put two new props on his aircraft and gained eight knots. What sought of climb out would this aircraft had at Max weight on one?
Students should be made aware of these problems because the decision to go around may not be an option in some aircraft. Even an EFATO on some aircraft should possibly be handled the same way as a single engine aircraft.
The age and condition of our aircraft should also be taken into consideration as how many will actually be capable of a missed approach at Maximum Take-off Weight? A colleague put two new props on his aircraft and gained eight knots. What sought of climb out would this aircraft had at Max weight on one?
Students should be made aware of these problems because the decision to go around may not be an option in some aircraft. Even an EFATO on some aircraft should possibly be handled the same way as a single engine aircraft.
Ozgrade3
No such thing, think about it!
Aileron? Sorry RUDDER controls YAW .
Students are to be discouraged from using aileron to prevent YAW!!!
Only approaching Vmca will rudder be ineffective in preveting adverse yaw.
Single engine ops in a twin are all about RUDDER .
Do YOU actually teach this stuff?
?
Asymmetric roll here is the problem
insufficient aileron authority prefents the roll leading to a loss of control.
Students are to be discouraged from using aileron to prevent YAW!!!
Only approaching Vmca will rudder be ineffective in preveting adverse yaw.
Single engine ops in a twin are all about RUDDER .
Do YOU actually teach this stuff?
Barron 58
Join Date: Apr 2001
Location: Camden, NSW, Australia
Posts: 271
Likes: 0
Received 0 Likes
on
0 Posts
Comprehensive training will show you what it can and cannot do. There is no point crashing it if you could have flown away. There is also no point crashing it when you can't fly away. You need to learn the difference. Your decision height should be SAFE and REALISTIC. Why do you have to go around? Another aircraft on the runway? Land beside him rightside up. That's safer than landing beside him upside down. When you apply the power to do the go around it will want to yaw and roll strongly. The question really is can you control that or not. Try it out at height but keep in mind, at height the live engine is producing less power, so it will yaw and roll less.
My idea is. By 300' agl you should know if you can achieve a safe landing or not - if in doubt go around and try again.
My idea is. By 300' agl you should know if you can achieve a safe landing or not - if in doubt go around and try again.
I fly, I agree with your other comments, however...
Control is only one part of the equation. Absolutely you must prevent YAW which will in itself prevent ROLL. However, the other BIG issue is Performance . Not much point having the beast under control as it slowly descends onto/into the trees, ground, building...other hard immovable object.
Practising a go-round at altitude will give you less yaw as the live engine will produce less thrust as you said but the aircraft will also perform less well compared to sea level.
The point of the exercise is to see how much altitude, or more importantly height
, is lost from the point the decision is made to abort the landing.
will want to yaw and roll strongly. The question really is can you control that or not.
Practising a go-round at altitude will give you less yaw as the live engine will produce less thrust as you said but the aircraft will also perform less well compared to sea level.
The point of the exercise is to see how much altitude, or more importantly height
, is lost from the point the decision is made to abort the landing.
Trashie,
You are correct in one point, rudder does control yaw. But in an asymmetric go-aeound condition, full flap and gear down, there is a significant amount of roll that accompanies the yaw. It does happn in the airoplane, I have demonstrated it more than 50 times in the last 6 months. Go look up the books, asymmetric roll is mentioned in every book on multi-engine flying and is specifically mentioned in the Barron Flight manual. I was specifically told to address this in my Multi-Engine Training Approaval by the ATO.
As for the performance of a fully feathered approach as part of an initial multi endorsement, I am lead to believe it a requirment as laid down by the CAAP.
Prior to this, usually on the last circuit before the end of the endorsement, the conditions are checked, VMC, etc light traffic in the circuit and not more than 10 knots crosswind. A clearence is required for this sequence from the Tower. The engine is feathered on mid downwind. This manouver is safe if carried out prudently. I believe it is necessary so that the student is familiar with the characteristics of the aircraft in a real engine out configuration, zero thrust is not allways a true representation of an engine out.
You are correct in one point, rudder does control yaw. But in an asymmetric go-aeound condition, full flap and gear down, there is a significant amount of roll that accompanies the yaw. It does happn in the airoplane, I have demonstrated it more than 50 times in the last 6 months. Go look up the books, asymmetric roll is mentioned in every book on multi-engine flying and is specifically mentioned in the Barron Flight manual. I was specifically told to address this in my Multi-Engine Training Approaval by the ATO.
As for the performance of a fully feathered approach as part of an initial multi endorsement, I am lead to believe it a requirment as laid down by the CAAP.
Prior to this, usually on the last circuit before the end of the endorsement, the conditions are checked, VMC, etc light traffic in the circuit and not more than 10 knots crosswind. A clearence is required for this sequence from the Tower. The engine is feathered on mid downwind. This manouver is safe if carried out prudently. I believe it is necessary so that the student is familiar with the characteristics of the aircraft in a real engine out configuration, zero thrust is not allways a true representation of an engine out.
Are you addressing me?
And you have done your ME training approval?
I am lead to believe it a requirment as laid down by the CAAP.
Last edited by Icarus2001; 4th Apr 2002 at 07:24.
Join Date: Mar 2001
Location: Three Tors
Posts: 405
Likes: 0
Received 0 Likes
on
0 Posts
Smile Icarus, your face might crack! 
Don't be so serious all the time, mkay?
My bolding.
.... and I would ask what might be one of the main effects of thrust (ie: go around power) over one wing surface, while the other has only the IAS of the aircraft with which to play? Flap settings here are another trap, serving to throw another wildcard in to the mix, which OG3 was (I believe) trying to allude to, not saying that he teaches with one (B58). The higher-energised airflow over the wing and flap surfaces on the side of the live engine, I would think would give significant rise to an assymetric lift condition as part of the overall equation, thus making the decision (moreso especially in a high desity alt day) a one to make earlier than later. As to calculating the point at which to call it a miss, I'm leaning more towards 500'+, but that is just me.
Have a fantastic day, mkay!
Don't be so serious all the time, mkay?
.....Absolutely you must prevent YAW which will in itself prevent ROLL .....
.... and I would ask what might be one of the main effects of thrust (ie: go around power) over one wing surface, while the other has only the IAS of the aircraft with which to play? Flap settings here are another trap, serving to throw another wildcard in to the mix, which OG3 was (I believe) trying to allude to, not saying that he teaches with one (B58). The higher-energised airflow over the wing and flap surfaces on the side of the live engine, I would think would give significant rise to an assymetric lift condition as part of the overall equation, thus making the decision (moreso especially in a high desity alt day) a one to make earlier than later. As to calculating the point at which to call it a miss, I'm leaning more towards 500'+, but that is just me.
Have a fantastic day, mkay!
Join Date: Oct 2001
Location: Vancouver Island
Posts: 2,517
Likes: 0
Received 0 Likes
on
0 Posts
Landing a twin engine piston airplane with the engine feathered for the purpose of demonstration during flight training is nothing short of wreckless endangerment in my opinion.
The argument that a feathered engine gives you a more realistic flight demonstration is being intellectually dishonest.
With a feathered engine only one drag configuration can be experienced, conversely you can simulate not only the feathered drag but a higher drag by reducing power below the simulated feathered condition.
Safety is compromised for no good reason when landing with a feathered engine, when simulating you have the option of adding power to the simulated engine to fly out of a dangerous condition.
I will not employ any instructor who teaches in such a needlessly risky manner.
Cat Driver
.............................
The hardest thing about flying is knowing when to say no.
The argument that a feathered engine gives you a more realistic flight demonstration is being intellectually dishonest.
With a feathered engine only one drag configuration can be experienced, conversely you can simulate not only the feathered drag but a higher drag by reducing power below the simulated feathered condition.
Safety is compromised for no good reason when landing with a feathered engine, when simulating you have the option of adding power to the simulated engine to fly out of a dangerous condition.
I will not employ any instructor who teaches in such a needlessly risky manner.
Cat Driver
.............................
The hardest thing about flying is knowing when to say no.
Confectionary Transfer Technician
Join Date: May 2001
Location: South Island
Posts: 137
Likes: 0
Received 0 Likes
on
0 Posts
I have to agree with Chuck, there is no need to actually feather it it in the circuit, the person who instructed me for my Multi Instructors - Ex RAAF told me of several stories of people feathering engines in the circuit & then it all turning to custard.
In my opinon , its not needed & If you want the student to experience what it flies like with one feathered again do it at altitude - which i do.
In my opinon , its not needed & If you want the student to experience what it flies like with one feathered again do it at altitude - which i do.
In the training environment, instructors have a duty to maintain a safe flying operation. It is simply not acceptable if the decrease in safety from a training operation exceeds the value of the training being offered. This becomes sadly obvious when training accidents in any particular scenario exceed the number of accidents under the real emergency condition - such as two engine shutdowns in four engine aircraft, or other multiple failure examples.
Given that many training scenarios will reduce the safety of the flight from "normal" conditions, you have to compensate for that by increasing safety in other areas - which is why you don't carry passengers in training, you fly at lower than MTOW, use longer than necessary runways, leave adequate height recovery margins and have an instructor experienced in the operation on board etc.
The safety reduction in a full feathered landing simply cannot be adequately compensated for, and as such should never be used as a training scenario - simulated one engine inop is more than adequate.
I do, however agree that a full feather and unfeather in flight should be demonstrated. (I know that Cat Driver and I disagree on this.)
Given that many training scenarios will reduce the safety of the flight from "normal" conditions, you have to compensate for that by increasing safety in other areas - which is why you don't carry passengers in training, you fly at lower than MTOW, use longer than necessary runways, leave adequate height recovery margins and have an instructor experienced in the operation on board etc.
The safety reduction in a full feathered landing simply cannot be adequately compensated for, and as such should never be used as a training scenario - simulated one engine inop is more than adequate.
I do, however agree that a full feather and unfeather in flight should be demonstrated. (I know that Cat Driver and I disagree on this.)
Last edited by Checkboard; 5th Apr 2002 at 05:58.
Checkboard, well put.
When I did my multi years ago it was common to land with one feathered on the last sortie. It seems to have been phased out. I remember doing it with some students when I gained ME training approval 8 years ago but the instructional value is marginal and as you say reduces safety margins with no compensation.
I think the time used in this procedure could be better employed.
The CAAP 5.23-1 seems vague on this. CASA regulating for safety...
When I did my multi years ago it was common to land with one feathered on the last sortie. It seems to have been phased out. I remember doing it with some students when I gained ME training approval 8 years ago but the instructional value is marginal and as you say reduces safety margins with no compensation.
I think the time used in this procedure could be better employed.
The CAAP 5.23-1 seems vague on this. CASA regulating for safety...
Join Date: Mar 2002
Location: san diego
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
to answer the original question -i encountered an interesting scenario yesterday in a be 76 duchess (on finals 320ft agl gear down 1st stage flap) when some construction equipment made a runway incursion the asymetric go around from that altitude was conducted with a height loss of aprox 50ft -i know not all twins have that performance and was quite surprised at the duchess aint that great performance wise but there you go!