Asymmetric Commital Height.
Joined: Jan 1999
Aviation Qualifications: CPL
Posts: 899
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From: Slowly decaying (disgracefully)
Chuck, you asked
During initial training for a MEPL rating we feather an engine (usually only once) so that the stude gets to go through the full feather/unfeather drills but this is done at/above 3000ft and within easy reach of an airfield.
The course is 6 hrs min of which 3.5 hrs min is asymmetric, during this period all failures are simulated (except as above). My practise is to either pull mixture (at/above 3000ft), sneakily cut off fuel (in the cruise, at/above 3000ft) or by hiding the throttles and closing one (below 3000ft) - as soon as drills are correctly performed I set zero thrust (net effect equal to a feathered prop, typically around 10" MAP).
Asymmetric approaches are always flown with the inop engine set to zero thrust so that the engine is available if required. The only exception to this is simulating a failure below Ach when a throttle is closed once the stude has committed, it's more important to reach the runway than try to mess around with feathering drills so the engine/prop are windmilling but power is available if required.
whatunion: slightly melodramatic old chap.
As I'm sure you know there is no problem at all controlling "these kites" with an engine feathered providing the minimum control speed is maintained - whether or not the height you can maintain is sufficient, or whether you can gain height, is another matter and depends on a variety of factors.
HFD
Do any of you do this with the non operating engine actually feathered?
The course is 6 hrs min of which 3.5 hrs min is asymmetric, during this period all failures are simulated (except as above). My practise is to either pull mixture (at/above 3000ft), sneakily cut off fuel (in the cruise, at/above 3000ft) or by hiding the throttles and closing one (below 3000ft) - as soon as drills are correctly performed I set zero thrust (net effect equal to a feathered prop, typically around 10" MAP).
Asymmetric approaches are always flown with the inop engine set to zero thrust so that the engine is available if required. The only exception to this is simulating a failure below Ach when a throttle is closed once the stude has committed, it's more important to reach the runway than try to mess around with feathering drills so the engine/prop are windmilling but power is available if required.
whatunion: slightly melodramatic old chap.
As I'm sure you know there is no problem at all controlling "these kites" with an engine feathered providing the minimum control speed is maintained - whether or not the height you can maintain is sufficient, or whether you can gain height, is another matter and depends on a variety of factors.
HFD
Joined: May 2004
Posts: 177
Likes: 0
From: london
whatunion: slightly melodramatic old chap.
As I'm sure you know there is no problem at all controlling "these kites" with an engine feathered providing the minimum control speed is maintained - whether or not the height you can maintain is sufficient, or whether you can gain height, is another matter and depends on a variety of factors.
no problem at all controlling these kites with an engine feathered providing the minimum contol speed is maintained!!!!!!!!!
( you forgot to mention that the gear needs to be stowed +, 5 deg bank and below max weight also)
as im sure i know!!!!!!!!!
i am sure i know that a lot of pilots have been killed trying to do just that.
so you, old chap, would say to your student, never worry about having an engine failure on these a/c because there is NO PROBLEM AT ALL in controlling them providing the minimum control speed is maintained! interesting, i hope you have a very good solicitor who can argue, " ah but he flew into the hill in perfect control!"
its all very well to have a light a/c on a good day and know you are going to feather an engine. its a complely different matter when it happens for real at max weight on the worst day.
take the aztec accident at glenrothes were a very experienced air charter pilot took off with 5 engineers on board on a c of a air test, the front cargo hatch opened and he immeadaitely feathered that side engine. the a/c hit the ground and all 5 engineers were killed.(piper say a/c will fly safely with hatch open and it will not touch prop)
then there was the guy at jersey that had just done his base check took off on 27 had an engine failure lost control and was killed just off the the south of the threshold.
you are putting in the mind of the student that the a/c will always climb away and i know you said whether it will climb is another matter. these a/c should be treated as single engine a/c in some situations. its always better to fly to the scene of the accident rather then to arrive at the scene of the accident wing tip first!
As I'm sure you know there is no problem at all controlling "these kites" with an engine feathered providing the minimum control speed is maintained - whether or not the height you can maintain is sufficient, or whether you can gain height, is another matter and depends on a variety of factors.
no problem at all controlling these kites with an engine feathered providing the minimum contol speed is maintained!!!!!!!!!
( you forgot to mention that the gear needs to be stowed +, 5 deg bank and below max weight also)
as im sure i know!!!!!!!!!
i am sure i know that a lot of pilots have been killed trying to do just that.
so you, old chap, would say to your student, never worry about having an engine failure on these a/c because there is NO PROBLEM AT ALL in controlling them providing the minimum control speed is maintained! interesting, i hope you have a very good solicitor who can argue, " ah but he flew into the hill in perfect control!"
its all very well to have a light a/c on a good day and know you are going to feather an engine. its a complely different matter when it happens for real at max weight on the worst day.
take the aztec accident at glenrothes were a very experienced air charter pilot took off with 5 engineers on board on a c of a air test, the front cargo hatch opened and he immeadaitely feathered that side engine. the a/c hit the ground and all 5 engineers were killed.(piper say a/c will fly safely with hatch open and it will not touch prop)
then there was the guy at jersey that had just done his base check took off on 27 had an engine failure lost control and was killed just off the the south of the threshold.
you are putting in the mind of the student that the a/c will always climb away and i know you said whether it will climb is another matter. these a/c should be treated as single engine a/c in some situations. its always better to fly to the scene of the accident rather then to arrive at the scene of the accident wing tip first!
Joined: Jan 1999
Aviation Qualifications: CPL
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From: Slowly decaying (disgracefully)
whatunion:
control depends on adequate speed, performance, however, requires gear stowed, 5 deg, etc. Min control speed itself depends on CG, weight, drag, power used, leg strength, etc.
I agree that there are times when they should be treated as SE acft but this does not justify your melodramatic comment.
The standard light twin departure brief contains something like this (I haven't got time to type the whole thing):
- eng problem on the ground: close both and stop
- eng problem airborne below Vtoss and ach: close both, lower nose, pick landing area, use power on live as required
- eng problem airborne above Vtoss and ach: control, attitude, power, drag, ident, verify, feather, 5 deg, etc
... this recognises that it isn't always possible to "go" and the stude is left in no doubt of this during their training. The concept of approach ach reinforces this - but this is down to performance and not control.
I prefer not to discuss accidents. We're all capable of getting it wrong and, unless you're in the hot seat at the time you don't know what actually happened.
HFD
control depends on adequate speed, performance, however, requires gear stowed, 5 deg, etc. Min control speed itself depends on CG, weight, drag, power used, leg strength, etc.
I agree that there are times when they should be treated as SE acft but this does not justify your melodramatic comment.
The standard light twin departure brief contains something like this (I haven't got time to type the whole thing):
- eng problem on the ground: close both and stop
- eng problem airborne below Vtoss and ach: close both, lower nose, pick landing area, use power on live as required
- eng problem airborne above Vtoss and ach: control, attitude, power, drag, ident, verify, feather, 5 deg, etc
... this recognises that it isn't always possible to "go" and the stude is left in no doubt of this during their training. The concept of approach ach reinforces this - but this is down to performance and not control.
I prefer not to discuss accidents. We're all capable of getting it wrong and, unless you're in the hot seat at the time you don't know what actually happened.
HFD
Joined: Dec 1998
Posts: 4,282
Likes: 6
From: Escapee from Ultima Thule
Point of accuracy: 5 deg AoB is not about performance. It's a certification limitation related to establishing Vmca. It prevents the manufacturer specifying an unreasonably low Vmca by using an excessive amount of bank.
Best performance is typically at ~2-3 deg AoB.
This has been discussed before on PPRuNe so a search should find the thread.
Best performance is typically at ~2-3 deg AoB.
This has been discussed before on PPRuNe so a search should find the thread.
Joined: May 2004
Posts: 177
Likes: 0
From: london
Vtoss and ach whats that? i like the connection with tossers though!
14 years since i instructed on twins so u need to explain that one to me.
i seemed to remember there was a blue line and a red line on the asi so shouldnt your brief relate to these, as thats whats in front of you. what you learnt in the classroom may not be but it could impress people at the coroners inquest.
whats the problem with discussing accidents. most advances in aviation have been the result of someone else killing themselves.
its always easier and cheaper to learn from someone elses mistakes.
whatunion says, man who never makes mistake never makes anything
14 years since i instructed on twins so u need to explain that one to me.
i seemed to remember there was a blue line and a red line on the asi so shouldnt your brief relate to these, as thats whats in front of you. what you learnt in the classroom may not be but it could impress people at the coroners inquest.
whats the problem with discussing accidents. most advances in aviation have been the result of someone else killing themselves.
its always easier and cheaper to learn from someone elses mistakes.
whatunion says, man who never makes mistake never makes anything
Last edited by whatunion; 29th May 2004 at 13:47.
Joined: Aug 2000
Posts: 1,776
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From: UK
Asymmetric training is potentially lethal. Over decades in the RAF it is a statistical fact that sim or practice asy accidents outstrip real asy accidents by a huge margin.
RAF asy rules are incredibly strict for just this reason. You never bust the asy speeds and heights. For example, the Canberra, perhaps the worst asy ac in recent years, the VCH was 600 feet. And that's genuine - I have been with a trapper who demonstrated just why it is so - and believe me, it was a hair-raising demo. The term 'parting grass' springs to mind.
I am astonished that the CAA and/or manufacturers haven't introduced rigid rules to protect pilots that have no experience or concept of the dangers involved - after all, it is exactly what test pilots are supposed to do, defining the limits to be flown by the average pilot. It should not be a question of the skill level of the pilot - some of the most experienced pilots in the world make mistakes and kill themselves because they break the rules. Rather the rules must be pitched at the average pilot; by all means add additional safety margins to the less experienced, but you have to have a definitive figure from which to start your calculations.
Having experienced years of sim, practice and real asy flying on a variety of 2 and 4 engined pistons and jets, I had developed a healthy respect for the published limits. I, and most of my friends are alive today because of them.
RAF asy rules are incredibly strict for just this reason. You never bust the asy speeds and heights. For example, the Canberra, perhaps the worst asy ac in recent years, the VCH was 600 feet. And that's genuine - I have been with a trapper who demonstrated just why it is so - and believe me, it was a hair-raising demo. The term 'parting grass' springs to mind.
I am astonished that the CAA and/or manufacturers haven't introduced rigid rules to protect pilots that have no experience or concept of the dangers involved - after all, it is exactly what test pilots are supposed to do, defining the limits to be flown by the average pilot. It should not be a question of the skill level of the pilot - some of the most experienced pilots in the world make mistakes and kill themselves because they break the rules. Rather the rules must be pitched at the average pilot; by all means add additional safety margins to the less experienced, but you have to have a definitive figure from which to start your calculations.
Having experienced years of sim, practice and real asy flying on a variety of 2 and 4 engined pistons and jets, I had developed a healthy respect for the published limits. I, and most of my friends are alive today because of them.
Joined: Aug 2000
Posts: 3,648
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From: UK
So what are you proposing FJJP? Mandatory asymmetric commital heights? Let's say we make it 600 ft. That sounds like it has a nice additional safety margin included.
So I'm approaching my destination which is giving 2000m vis, BKN004 in my light twin. Not too challenging for a symmetric ILS approach. I'm solo, and at the end of my flight so I'm light. An engine starts to surge, to the extent that I feel the best strategy is to shut it down. Now what?
Options:
1) Fly the approach, knowing that by 600 ft I probably won't be visual so I'll have to do an asymmetric go around?
2) Fly to my alternate with a non-precision approach, reporting 3000m BKN007 but sufficiently far away that I need to fly for 30 mins on a single engine and I consume all my alternate fuel getting there.
3) Something else?
Your call.
So I'm approaching my destination which is giving 2000m vis, BKN004 in my light twin. Not too challenging for a symmetric ILS approach. I'm solo, and at the end of my flight so I'm light. An engine starts to surge, to the extent that I feel the best strategy is to shut it down. Now what?
Options:
1) Fly the approach, knowing that by 600 ft I probably won't be visual so I'll have to do an asymmetric go around?
2) Fly to my alternate with a non-precision approach, reporting 3000m BKN007 but sufficiently far away that I need to fly for 30 mins on a single engine and I consume all my alternate fuel getting there.
3) Something else?
Your call.
Joined: May 1999
Aviation Qualifications: ATP+Mil
Posts: 27,399
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From: Quite near 'An aerodrome somewhere in England'
Well, I for one certainly think that there should be mandatory Engine Out Allowances and Visual Committal Heights applied to light piston singles......
The alternative? Press on with your approach, try to go-around......and die screaming?
The alternative? Press on with your approach, try to go-around......and die screaming?
Joined: Jun 2001
Posts: 889
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From: Australia
Regarding mandatory visual committal heights - given that ten pilots will collectively have eleven opinions about anything technical, there would end up being so many "exceptions" that the basic rule would be swamped.
Compare the private owner of a well maintained twin in hilly country, with an experienced ME instructor operating at a flat airfield.
A suggested Engine Out Allowance in the POH / FM might work. But from this thread, it seems that most people have 200' - 300' in mind already, assuming no extraordinary circumstances.
O8
Compare the private owner of a well maintained twin in hilly country, with an experienced ME instructor operating at a flat airfield.
A suggested Engine Out Allowance in the POH / FM might work. But from this thread, it seems that most people have 200' - 300' in mind already, assuming no extraordinary circumstances.
O8
Joined: May 2004
Posts: 177
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From: london
sorry not meant to be tasteless especially considering the examiner was killed but its a good lesson for all those instructors who expect their students to replicate training performance when it happens for real.
I cant think of one incident were a pilot has got away with a real engine failure near the ground in a perf c twin.
do you remember the clown who cleared customs at birmingham after a foreign trip and then positioned to wellesbourne. well that was his intention but he was low on fuel and instead of waiting to refuel at bhx he did a quick rolling take off from a taxyway turn and found out the meaning of surge and starvation just as he was getting airborne. the seneca ended up on its back and he was lucky to get away with his life.
this particular individual was an accident waiting to happen and one of the most arrogant and self opinionated amateur pilots i have ever come across. he was however well experienced on twins for a ppl with over 1000 hours and owned his own aircraft.
i believe not enough instructors drive home the point about the danger of light twins and single engine performance. there is a mighty big difference between a planned training simulated engine failure and one for real when you are not expecting it, as our friend above found out, the hard way!
ps the humberside accident detail is current in the uk flying mags
I cant think of one incident were a pilot has got away with a real engine failure near the ground in a perf c twin.
do you remember the clown who cleared customs at birmingham after a foreign trip and then positioned to wellesbourne. well that was his intention but he was low on fuel and instead of waiting to refuel at bhx he did a quick rolling take off from a taxyway turn and found out the meaning of surge and starvation just as he was getting airborne. the seneca ended up on its back and he was lucky to get away with his life.
this particular individual was an accident waiting to happen and one of the most arrogant and self opinionated amateur pilots i have ever come across. he was however well experienced on twins for a ppl with over 1000 hours and owned his own aircraft.
i believe not enough instructors drive home the point about the danger of light twins and single engine performance. there is a mighty big difference between a planned training simulated engine failure and one for real when you are not expecting it, as our friend above found out, the hard way!
ps the humberside accident detail is current in the uk flying mags
Joined: Aug 2000
Posts: 3,648
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From: UK
I cant think of one incident were a pilot has got away with a real engine failure near the ground in a perf c twin
Don't get me wrong: your point is a good one. But it's almost impossible to build any sort of statistical picture.
We've also come a long way from discussing the risks of a planned asymmetric go around to the risks of an unplanned engine outage at low level. While the former is non-trivial, the latter is what seems to kill.
Joined: May 2004
Posts: 177
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From: london
how would i expect to know about them;
same way i get to know about anything in the industry i have worked in for 30 years.
your quite right about statistics but most twin pilots i have spoken to that are ppls have very misunderstood expectations of single engine performance.
i base some of my theory on some advice an ex air force jet pilot and very experienced exec prop jet and piston examiner gave me one day.
why have a higher miinima for a single engine app than an all engine app. the last thing in the world you want to do is do a se go around in a perf c twin, i totally agree.
the one difference i found between the pro flyng of twins in the charter world and the ppl flying of twins is that most pros had a very sceptical disbelief in se performance. whereas most ppl's really believed that a twin with an engine failure was just raring to go, not a problem, just the same as training.
ask yourselves how many ppl twin instructors actually show closing the live engine throttle and landing on the remaining runway as an option.
a suprise engine failure on take off or a low level go around on one engine is beyond the capabilities of most ppls in all but the ideal of conditions, thats my theory.
same way i get to know about anything in the industry i have worked in for 30 years.
your quite right about statistics but most twin pilots i have spoken to that are ppls have very misunderstood expectations of single engine performance.
i base some of my theory on some advice an ex air force jet pilot and very experienced exec prop jet and piston examiner gave me one day.
why have a higher miinima for a single engine app than an all engine app. the last thing in the world you want to do is do a se go around in a perf c twin, i totally agree.
the one difference i found between the pro flyng of twins in the charter world and the ppl flying of twins is that most pros had a very sceptical disbelief in se performance. whereas most ppl's really believed that a twin with an engine failure was just raring to go, not a problem, just the same as training.
ask yourselves how many ppl twin instructors actually show closing the live engine throttle and landing on the remaining runway as an option.
a suprise engine failure on take off or a low level go around on one engine is beyond the capabilities of most ppls in all but the ideal of conditions, thats my theory.
Joined: Jun 2001
Posts: 889
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From: Australia
Nice idea...
ask yourselves how many ppl twin instructors actually show closing the live engine throttle and landing on the remaining runway as an option
EF at low level on a go-around? Yes, done it, student struggled to cope, I took over, student said "ah yes, I'll remember that next time." But human factors says that s/he probably won't in the heat of the moment. Plus, again, I would like to die of old age, and giving engine failures at 200' or less with someone else as PF is not a good way to achieve this...
It would be much easier if we had simulators that accurately reproduced this kind of problem - but how many flying schools have simulators of this calibre with good visuals?
Alternatively, many more things are possible with more dual experience on type - but then all the students will disappear down the road to the school offering ratings at the legal minimum hours.
This last point is perhaps the biggest drawback to improving standards in a highly deregulated industry.
cheers to all,
O8
Joined: Apr 1999
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From: all over the place
Asymetric committal altitude is just normal decision ht 200' plus EOA depending on speed.
When initiating a go around single engine the power has to be increased before the pitch up action to allow an initial accelaration, if pitch is increased first the a/c will decelarate and if you are close to blue line trouble will ensue.
Therefore, the aircraft will continue to descend during this power increase. Typically it takes 80-100' of further descent for this accelaration this is the engine out allowance.
So, the asymetric go around ht is dependent on approach speed.
It should 200' unless 10kts above, at or below blue line in which case 100' should be added making 300' to commit or initiate.
When initiating a go around single engine the power has to be increased before the pitch up action to allow an initial accelaration, if pitch is increased first the a/c will decelarate and if you are close to blue line trouble will ensue.
Therefore, the aircraft will continue to descend during this power increase. Typically it takes 80-100' of further descent for this accelaration this is the engine out allowance.
So, the asymetric go around ht is dependent on approach speed.
It should 200' unless 10kts above, at or below blue line in which case 100' should be added making 300' to commit or initiate.
Joined: Jan 1999
Aviation Qualifications: CPL
Posts: 899
Likes: 42
From: Slowly decaying (disgracefully)
We seem to have a number of different threads going here for the different critical failure situations. This is what I propose (and teach):[list=1][*]At any time that control is not possible: shut both throttles, lower the nose ('tis better to hit the ground erect than inverted)[*]Take off
- Default: throttles shut, stop on the runway ('tis better to be on the ground than in the air)
- If below Vtoss (take off safety speed) and below some height (why not the same as Ach (asymm commital ht): throttles shut, land straight ahead (option to then use power to reach best area)
- If above Vtoss & Ach: control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse[*]Base leg (no fire): control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse.[*]Final approach
- Visual, above Ach (no fire): control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse
- Visual, Below Ach: land straight ahead, use power to reach best area (but lead with rudder!), speed may decrease to normal Vat asymm
- IMC, add Ach to DA/MDA to generate new DA/MDA (because Ach is designed to allow the aircraft to be accelerated, cleaned-up and a climb initiated)[/list=1]
Personally:
Don't get me wrong, I agree wholeheartedly that if you are unable to control the aircraft at any time there is only one answer, become a glider and land the right way up in the best place available. My problem is that it is impractical to teach it at ground level, that's why the full EFATO drill is usually taught and examined at 2000-4000ft.
Health warnings:
1. I haven't got the Seneca POH to hand, these numbers came from some rough notes
2. the wine at lunchtime may have caused some imprecision in the calculatory department
... please don't shout too loud if I've boobed.
HFD
- Default: throttles shut, stop on the runway ('tis better to be on the ground than in the air)
- If below Vtoss (take off safety speed) and below some height (why not the same as Ach (asymm commital ht): throttles shut, land straight ahead (option to then use power to reach best area)
- If above Vtoss & Ach: control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse[*]Base leg (no fire): control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse.[*]Final approach
- Visual, above Ach (no fire): control, lower nose, full power, gear/flaps up, identify/verify/feather, small bank to live, etc at Vyse
- Visual, Below Ach: land straight ahead, use power to reach best area (but lead with rudder!), speed may decrease to normal Vat asymm
- IMC, add Ach to DA/MDA to generate new DA/MDA (because Ach is designed to allow the aircraft to be accelerated, cleaned-up and a climb initiated)[/list=1]
Personally:
- I insist on a full failure brief at the end of the pre-departure checks
- I don't PRACTICALLY teach/examine engine failure on the runway because the margins are just too small and I believe it introduces an unacceptable risk for little benefit
- I don't PRACTICALLY teach/examine EFATO below the commit height/speed for the same reason.
For those that advocate teaching EFATO and land ahead from around 250ft, have you done the sums? Very roughly (assume MAUW, +15C, paved, sea level, nil wind, 0 flap)...
TODR 2200
distance from 50ft to 200ft (9s @ 1000fpm & 85kts): 1300ft
distance from 200ft to 50ft (18s @ 500fpm & 85kts): 2500ft
LDR 1900
Total, without the fiddle factors for grass and dither: 7900ft or 2.4km - does anyone instruct on light singles from a runway this long? Even if you do it at 50ft (staggeringly unsafe in my view) the distance needed is around 4000ft without any faffing about. - I DO practically teach EFATO from a symmetric go-around just above Ach because this is fully representative of the take-off situation but with healthier margins and doesn't upset any NIMBYs at the end of the runway (well not as much, anyway)
Don't get me wrong, I agree wholeheartedly that if you are unable to control the aircraft at any time there is only one answer, become a glider and land the right way up in the best place available. My problem is that it is impractical to teach it at ground level, that's why the full EFATO drill is usually taught and examined at 2000-4000ft.
Health warnings:
1. I haven't got the Seneca POH to hand, these numbers came from some rough notes
2. the wine at lunchtime may have caused some imprecision in the calculatory department
... please don't shout too loud if I've boobed.
HFD