Engine out terrain clearance
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And then we still have the complexibility of which engine failed. There is a big difference in flying 15 degrees away from the failed engine, and into the failed engine.
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Hazelnuts, there is.
Your straight ahead path is calculated with a max 5 degree bank into the live engine. This 5 degrees is used to calculate the rudder size.
15 degrees in the turn away from the live engine, banks you 20 degrees away from the V2 to VmcA protection.
Your straight ahead path is calculated with a max 5 degree bank into the live engine. This 5 degrees is used to calculate the rudder size.
15 degrees in the turn away from the live engine, banks you 20 degrees away from the V2 to VmcA protection.
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latetonite,
Max 5 degrees of bank is used for determination of Vmca. OEI climb performance is determined with wings level, except that a small amount of bank is permitted (less than 2 degrees) if rudder capacity is insufficient to maintain heading at V2 (which is not less than 1.1 Vmca).
Max 5 degrees of bank is used for determination of Vmca. OEI climb performance is determined with wings level, except that a small amount of bank is permitted (less than 2 degrees) if rudder capacity is insufficient to maintain heading at V2 (which is not less than 1.1 Vmca).
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An observation or two ...
These are the rules, break them if you must to stay safe
(a) but just make sure you have a damned good story for the enquiry in case it turns to custard in the execution ... ie know what you are doing .. one needs to understand the why of the rules before throwing them away, regardless of the circumstances. And, yes, the (performance) rules apply while the circumstances are constrained to approximate the presumptions inherent. The further the circumstances wander, the more the Commander gets to apply his/her knowledge base and earn his/her paycheck.
(b) or, as a fine checkie once observed to me in the debrief .. "Young John, the Ops Manual has an invisible comment on the front page which says ... To be read with a modicum of commonsense "
bank angle limits to account for the degradation in a turn
Not quite right ...
(a) bank is limited to 15 degrees to put a fence around the performance loss.
(b) there is nothing to prevent a procedure specifying a lesser bank angle .. generally to accommodate a turn radius problem.
(c) the climb degradation is accounted for by routine calculations. For in service application, the AFM will specify a minimum climb gradient penalty to be applied for the particular aircraft, generally around 0.6 - 0.8 or so gradient reduction.
(d) in practice, the ops engineer addresses the penalty artificially by increasing the calculated height of down stream obstacles to provide the same result but permitting the calculation to be performed as a quasi straight ahead climb for calculation convenience.
in case of EO may no even limb at all in a turn
I have never seen a case where a competent ops engineer has not maintained the WAT limit during a turn, having applied the decrement. Not saying it doesn't happen but such would defeat the philosophy of having a WAT limit.
EO procedures clear obstacles and terrain by minimum requirements
That applies to the NFP. As the aircraft gets further away from the end of the TOD, the expected real height progressively increases above the calculated NFP
Hazelnuts, there is.
I know who HN39 is, I suspect you don't. He is quite right on this point (and an acknowledged expert in aircraft performance matters generally). I suggest that his observations and comments ought not to be disregarded lightly.
Your straight ahead path is calculated with a max 5 degree bank into the live engine
Not necessarily .. depends on the speed for the turn.
The 5 degree consideration is at, or close to, Vmc. As the margin increases, the use of a banked climb for Vmc considerations is discarded. Indeed, on some aircraft, due to systems limitations, it is impracticable to maintain a shallow bank angle and the OEI climb is done wings level.
Although some operators do impose such a requirement, it is more a stylistic encumbrance than a necessary requirement. I well recall having to do that exercise to get the tick in the box on AN F27s in a much earlier life ..
On the other hand, if systems permit and you are after the last bit of climb performance, the optimum OEI climb will be achieved somewhere around 2-3 degrees. Generally not worth the effort and we go for wings level.
These are the rules, break them if you must to stay safe
(a) but just make sure you have a damned good story for the enquiry in case it turns to custard in the execution ... ie know what you are doing .. one needs to understand the why of the rules before throwing them away, regardless of the circumstances. And, yes, the (performance) rules apply while the circumstances are constrained to approximate the presumptions inherent. The further the circumstances wander, the more the Commander gets to apply his/her knowledge base and earn his/her paycheck.
(b) or, as a fine checkie once observed to me in the debrief .. "Young John, the Ops Manual has an invisible comment on the front page which says ... To be read with a modicum of commonsense "
bank angle limits to account for the degradation in a turn
Not quite right ...
(a) bank is limited to 15 degrees to put a fence around the performance loss.
(b) there is nothing to prevent a procedure specifying a lesser bank angle .. generally to accommodate a turn radius problem.
(c) the climb degradation is accounted for by routine calculations. For in service application, the AFM will specify a minimum climb gradient penalty to be applied for the particular aircraft, generally around 0.6 - 0.8 or so gradient reduction.
(d) in practice, the ops engineer addresses the penalty artificially by increasing the calculated height of down stream obstacles to provide the same result but permitting the calculation to be performed as a quasi straight ahead climb for calculation convenience.
in case of EO may no even limb at all in a turn
I have never seen a case where a competent ops engineer has not maintained the WAT limit during a turn, having applied the decrement. Not saying it doesn't happen but such would defeat the philosophy of having a WAT limit.
EO procedures clear obstacles and terrain by minimum requirements
That applies to the NFP. As the aircraft gets further away from the end of the TOD, the expected real height progressively increases above the calculated NFP
Hazelnuts, there is.
I know who HN39 is, I suspect you don't. He is quite right on this point (and an acknowledged expert in aircraft performance matters generally). I suggest that his observations and comments ought not to be disregarded lightly.
Your straight ahead path is calculated with a max 5 degree bank into the live engine
Not necessarily .. depends on the speed for the turn.
The 5 degree consideration is at, or close to, Vmc. As the margin increases, the use of a banked climb for Vmc considerations is discarded. Indeed, on some aircraft, due to systems limitations, it is impracticable to maintain a shallow bank angle and the OEI climb is done wings level.
Although some operators do impose such a requirement, it is more a stylistic encumbrance than a necessary requirement. I well recall having to do that exercise to get the tick in the box on AN F27s in a much earlier life ..
On the other hand, if systems permit and you are after the last bit of climb performance, the optimum OEI climb will be achieved somewhere around 2-3 degrees. Generally not worth the effort and we go for wings level.
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Please do not take this as an offence, but have a look at this document:
http://www.avioconsult.com/downloads...20accident.pdf
It is not the climb gradient I worry about. it is the controlability.
http://www.avioconsult.com/downloads...20accident.pdf
It is not the climb gradient I worry about. it is the controlability.
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From FAA Advisory Circular no. 25-7C "Flight Test Guide For Certification Of Transport Category Airplanes":
From the paper linked in #46:
Without consulting the accident report, it would seem that the accident was probably due to failure to maintain correct pitch attitude and airspeed rather than loss of lateral control, use of rudder or bank angle.
17. Climb: One-Engine-Inoperative - § 25.121.
a.(...).
b. Procedures.
(1)(a) (...) These climbs are flown with the wings nominally level. (...)
(2) If full rudder with wings level cannot maintain constant heading, small bank angles of up to 2 to 3 degrees into the operating engine(s), with full rudder, should be used to maintain constant heading. (...).
a.(...).
b. Procedures.
(1)(a) (...) These climbs are flown with the wings nominally level. (...)
(2) If full rudder with wings level cannot maintain constant heading, small bank angles of up to 2 to 3 degrees into the operating engine(s), with full rudder, should be used to maintain constant heading. (...).
According to the accident investigation report, the airplane lost speed progressively, stalled and crashed, (...)
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I will have a looksee at the cited URL shortly.
Indeed, we should all be critically concerned with control around Vmca .. while keeping in mind that civil pilots generally have no reason to be operating at that limit and ought to keep some margin about the real Vmca for the conditions.
Military folks have a fascination with Vmca for reasons which elude me - most likely associated with the military need to be able to exploit the envelope boundaries for sensible military purposes (which makes perfectly good sense for combat vehicles but not so much for transport) - however, that is not a concern here.
In general we are far more concerned with performance and this, of course, requires that folk make very sure that they don't permit the speed to decrease below OEI targets.
Certainly no offence involved but, at this stage, I am not following the reason for latetonite's post ?
Indeed, we should all be critically concerned with control around Vmca .. while keeping in mind that civil pilots generally have no reason to be operating at that limit and ought to keep some margin about the real Vmca for the conditions.
Military folks have a fascination with Vmca for reasons which elude me - most likely associated with the military need to be able to exploit the envelope boundaries for sensible military purposes (which makes perfectly good sense for combat vehicles but not so much for transport) - however, that is not a concern here.
In general we are far more concerned with performance and this, of course, requires that folk make very sure that they don't permit the speed to decrease below OEI targets.
Certainly no offence involved but, at this stage, I am not following the reason for latetonite's post ?
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The reason for posting was that, as operators themselves are responsible for the One Engine Out Procedure for their fleet, I seriously wonder if they take the controllability problem into account.
Many procedures require an immediate turn left or right, at a now standard 15 degrees of bank.
Taken all factors in to the limit, a pilot flying at calculated V2 might run out of rudder while banking, or find himself with a sink rate while increasing the speed to control the aircraft, as VmcA at this bank angle is substantionaly increased.
The referred document explains this very well.
Many procedures require an immediate turn left or right, at a now standard 15 degrees of bank.
Taken all factors in to the limit, a pilot flying at calculated V2 might run out of rudder while banking, or find himself with a sink rate while increasing the speed to control the aircraft, as VmcA at this bank angle is substantionaly increased.
The referred document explains this very well.
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latetonite,
the scheduled speeds provide adequate controllability.
I'll refrain from commenting on the opinions expressed in the referred paper. Boeing's response is entirely appropriate.
IIRC jet transport gradient reduction for 15 degrees of bank is typically of the order of 0.1 - 0.15 % gradient (0.001 to 0.0015 radians).
the scheduled speeds provide adequate controllability.
I'll refrain from commenting on the opinions expressed in the referred paper. Boeing's response is entirely appropriate.
IIRC jet transport gradient reduction for 15 degrees of bank is typically of the order of 0.1 - 0.15 % gradient (0.001 to 0.0015 radians).
Last edited by HazelNuts39; 27th Sep 2013 at 17:27.
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Thanks for your help John T. One final question as you seem to know about this stuff. If you were to do an analysis for a runway at an airport with flat terrain all around except for the extremely high wall of mountains off in the distance that rise up like the Rockies seem to do(and you could never get over)....
How far away would they have to be for you to not have a special procedure requiring a turn.
How far away would they have to be for you to not have a special procedure requiring a turn.
Last edited by JammedStab; 27th Sep 2013 at 15:42.
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How far away would they have to be for you to not have a special procedure requiring a turn.
I presume you are considering the case of flying straight ahead and then clearing the obstacles ? or else running a turning escape
Your question can't be answered simply as it doesn't define the Type and situation geometry.
What we would do is run an analysis for the case and see if we clear the obstruction at the weight for the conditions. If so, OK, if not, then the choice is either to reduce the weight until it is OK .. or turn to make the problem go away.
The minimum distance from the runway head to the obstacle will depend on the V2 which determines turn radius. Run the takeoff to a minimum 50ft NFP clearance and then one can commence the turn. The relevant obstacle consideration splays will then determine how far away the obstacles have to be .. ie the position in the turn where the splay edge sits at a NFP clearance of 50ft is the critical consideration. Simple geometry then gives you your required answer. For an early start turn, the distance to the obstacle is not overly great ..
The process may sound a tad complicated but it really is very straightforward ...
I presume you are considering the case of flying straight ahead and then clearing the obstacles ? or else running a turning escape
Your question can't be answered simply as it doesn't define the Type and situation geometry.
What we would do is run an analysis for the case and see if we clear the obstruction at the weight for the conditions. If so, OK, if not, then the choice is either to reduce the weight until it is OK .. or turn to make the problem go away.
The minimum distance from the runway head to the obstacle will depend on the V2 which determines turn radius. Run the takeoff to a minimum 50ft NFP clearance and then one can commence the turn. The relevant obstacle consideration splays will then determine how far away the obstacles have to be .. ie the position in the turn where the splay edge sits at a NFP clearance of 50ft is the critical consideration. Simple geometry then gives you your required answer. For an early start turn, the distance to the obstacle is not overly great ..
The process may sound a tad complicated but it really is very straightforward ...
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Jammed stab - refer to post #25. Those constructing terrain clearance paths rely on a little commonsense and awareness of area MORA/MSA whatever you wish to call it. If you are entering an area with an MORA/MSA higher than what you have, don't (IMC) and only with extreme caution VMC. I have no idea how far out an obstacle would be included in the study and JT's post has missed your query.
As guesswork I would suggest that obstacles with a 30nm radius of the field would be looked at, but I cannot see anyone warning crews about the Rockies out of Calgary in the case you cited.
As guesswork I would suggest that obstacles with a 30nm radius of the field would be looked at, but I cannot see anyone warning crews about the Rockies out of Calgary in the case you cited.
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I would expect any reputable ops engineer to consider whatever obstacles at whatever distance may be necessary to cover the entire flight. One doesn't run to 1500ft, for instance, and then just leave the pilot with the problem (OK, I know some operators do, but that's not a nice thing to do).
Routinely one might well be looking in excess of 50nm for a critical twin just to get the basic takeoff done .. then it becomes a matter of making sure that the enroute path is OK.
MORA is a very restrictive sledgehammer way of getting around the problem ... but very useful to the Commander if his/her operator doesn't do the work at the ops engineer level ...
Routinely one might well be looking in excess of 50nm for a critical twin just to get the basic takeoff done .. then it becomes a matter of making sure that the enroute path is OK.
MORA is a very restrictive sledgehammer way of getting around the problem ... but very useful to the Commander if his/her operator doesn't do the work at the ops engineer level ...
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JT - in all my time I have never seen any company analyse obstructions at any distance - the only note I have EVER seen is 'ensure en-route MSA achieved' which is pretty logical, really.
It may be a 'very restrictive sledgehammer' but in the absence of anything else to hit it with how are we supposed not to 'hit it'?
As an aside, I once flew with a Captain who INSISTED I refuse the initial clearance to FL60 out of Venice (UK bound) as it was 'not high enough for the Alps'. VCE ATC were slightly surprised and I persuaded him to accept it rather than return to stand.
It may be a 'very restrictive sledgehammer' but in the absence of anything else to hit it with how are we supposed not to 'hit it'?
As an aside, I once flew with a Captain who INSISTED I refuse the initial clearance to FL60 out of Venice (UK bound) as it was 'not high enough for the Alps'. VCE ATC were slightly surprised and I persuaded him to accept it rather than return to stand.
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I have never seen any company analyse obstructions at any distance - the only note I have EVER seen is 'ensure en-route MSA achieved' which is pretty logical, really.
On my watch we made sure that the flight was covered for the entire sector so that I slept comfortably at night. When I flew for AN, their ops eng section were similarly conservative .. TN was much the same.
Clearly, we are all aware of those operators which choose to cut corners .. Centaurus used to fly for one which just didn't bother to worry about some difficult obstacles ...
If a runway is clearly not critical, a general SOP protocol is fine .. but, if that is not the case, then it is appropriate for the operator to do the sums to make it OK.
It may be a 'very restrictive sledgehammer' but in the absence of anything else to hit it with how are we supposed not to 'hit it'?
As per the previous comment
As an aside, I once flew with a Captain who INSISTED I refuse the initial clearance to FL60 out of Venice (UK bound) as it was 'not high enough for the Alps'. VCE ATC were slightly surprised and I persuaded him to accept it rather than return to stand
We have all had our modest burdens to bear ...
On my watch we made sure that the flight was covered for the entire sector so that I slept comfortably at night. When I flew for AN, their ops eng section were similarly conservative .. TN was much the same.
Clearly, we are all aware of those operators which choose to cut corners .. Centaurus used to fly for one which just didn't bother to worry about some difficult obstacles ...
If a runway is clearly not critical, a general SOP protocol is fine .. but, if that is not the case, then it is appropriate for the operator to do the sums to make it OK.
It may be a 'very restrictive sledgehammer' but in the absence of anything else to hit it with how are we supposed not to 'hit it'?
As per the previous comment
As an aside, I once flew with a Captain who INSISTED I refuse the initial clearance to FL60 out of Venice (UK bound) as it was 'not high enough for the Alps'. VCE ATC were slightly surprised and I persuaded him to accept it rather than return to stand
We have all had our modest burdens to bear ...
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According to Wikipedia, Calgary is situated " in an area of foothills and prairie, approximately 80 km (50 mi) east of the front ranges of the Canadian Rockies" (i.e. 43 nm).
And also: "The Canadian Rockies have numerous high peaks and ranges, such as Mount Robson (3,954 m (12,972 ft)) and Mount Columbia (3,747 m (12,293 ft))."
If your planned route is over the Rockies, won't you be 'looking at' those in preflight planning?
And also: "The Canadian Rockies have numerous high peaks and ranges, such as Mount Robson (3,954 m (12,972 ft)) and Mount Columbia (3,747 m (12,293 ft))."
If your planned route is over the Rockies, won't you be 'looking at' those in preflight planning?
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Jammedstab, it will depend on the airline / aircraft and airport. Most paper AFM charts have a maximum distance for distant obstacles of 72,000 feet, and as someone else has pointed out the Type A chart may go out to about 10 miles. So the airline back engineering guys will look at the airport, decide if 10 miles is enough, if not they will take the obstacles out to the maximum that they can by obtaining topographical maps for the airport and surrounding area. If in the event that the obstacles are further than 72,000 feet, they will be scaled down so that they can be used in the AFM chart.
Ideally, all engine failure procedures should have a finish point, some say this should be the MSA, but unfortunately for most aircraft the software doesn't exist to calculate this, so its best to take the aircraft to a fixed point and hold.
The newer digital AFM's allow for further distances to be calculated and with the advances in Google Earth and the fact that collecting terrain data has become a lot easier. the results should be better procedures.
The process isnt always perfect, there was a positing on here a few years ago where someone wrote about an engine failure procedure from a Greek island, the procedure turned out over the sea, but they completely forgot about the next island!
Mutt
Ideally, all engine failure procedures should have a finish point, some say this should be the MSA, but unfortunately for most aircraft the software doesn't exist to calculate this, so its best to take the aircraft to a fixed point and hold.
The newer digital AFM's allow for further distances to be calculated and with the advances in Google Earth and the fact that collecting terrain data has become a lot easier. the results should be better procedures.
The process isnt always perfect, there was a positing on here a few years ago where someone wrote about an engine failure procedure from a Greek island, the procedure turned out over the sea, but they completely forgot about the next island!
Mutt
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Ferzackerly, HN39.
JT - JS asked up to how far out you would prescribe an emergency procedure. EG. West bound from Calgary? In AN?
- I would be interested to know. I prefer my sledgehammer (aka HN39's 'preflight planning').
JT - JS asked up to how far out you would prescribe an emergency procedure. EG. West bound from Calgary? In AN?
If you were to do an analysis for a runway at an airport with flat terrain all around except for the extremely high wall of mountains off in the distance that rise up like the Rockies seem to do(and you could never get over)....
How far away would they have to be for you to not have a special procedure requiring a turn.
How far away would they have to be for you to not have a special procedure requiring a turn.