great instrument cross checks!!!!!
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Under what circumstances would you be 3150' above airfield elevation on slope at 13 DME?
Under what circumstances would your altimiter read 3150' if you were on slope at 13 DME to an airfield 763' above sea level?
QNH you'd have 4663' on the altimeter
QFE you'd have 3900' on the altimeter
QNE you'd have 4663' +/- correction for local pressure.
In all cases you'd be 3900' above the airfield.
QFE you'd have 3900' on the altimeter
QNE you'd have 4663' +/- correction for local pressure.
In all cases you'd be 3900' above the airfield.
where does 3150' come into it?
With 1013 set on a standard day, at an altitude of 3900' or a flight level of 139, you will be 3150 feet above the aerodrome. If you them correct for altitude/pressure you get your check height. Why is that so hard to understand?
The point about a gross error check is that it should be arrived at in a different way to the normal way. Ever do a gross error check on a loadsheet after it is delivered to your flight deck? Same thing.
And do you agree that a simple altimeter check can be made in error in the heat of the moment?
So if you want to say "it was an error made in the heat of the moment, and therefore excusable", be my guest. I'd rather not fly with you, though.
RTFQ
Here's the question you originally answered:
How quickly can you work out a 13nm check with a runway elevation of 763ft.
13x3(00) = 3900
3900 - 750 = 3150
3900 - 750 = 3150
So if you want to say "it was an error made in the heat of the moment, and therefore excusable", be my guest. I'd rather not fly with you, though.
I like to fly with people who admit their mistakes rather than trying to fly themselves out of (or in to) a hole.
Last edited by AerocatS2A; 4th Feb 2007 at 11:04.
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I give up. If you can't see it, I can't help you. The math is correct, as explained. If you don't understand how it works, I recommend a good textbook. If you don't understand the concept of a gross error check, I have trouble believing that you are a professional aviator of any sort. If you don't understand the math... well... 
I'm willing to learn, you just need to explain it so I can understand it. At the moment there's obviously a basic missunderstanding between what we are saying.
Here is my idea of a gross error check for a glideslope at 13 DME, please, in all honesty, show me where you differ:
There's two ways of doing it, either at the distance, or at the altitude.
If done at the distance we say:
At 13 DME I want to be 13 x 300 = 3900' above the airfield, that equals 4650' given a field elevation of 750' (rounded.)
Then, passing 13 DME we have a look at our altimeter, see that it reads 4625' and we know we are in the ball park.
Or, if done at the altitude we say:
At 13 DME I want to be 13 x 300 = 3900' above the airfield, that equals 4650' given a field elevation of 750' (rounded.)
Then passing 4650' we look at our DME and read 13.1, we see we are in the ball park and therefore safe.
If we were using QFE, the above would all be the same except we'd use 3900' instead of 4650'.
If we were using QNE for some reason we'd use 4650' and make an adjustment for the local pressure.
Please, explain, because I'm not getting it, how you would use your figure of 3150'.
P.S., in case it's not clear, there is no sarcasm intended in any of what I've just written, I honestly want to understand what you're talking about.
Here is my idea of a gross error check for a glideslope at 13 DME, please, in all honesty, show me where you differ:
There's two ways of doing it, either at the distance, or at the altitude.
If done at the distance we say:
At 13 DME I want to be 13 x 300 = 3900' above the airfield, that equals 4650' given a field elevation of 750' (rounded.)
Then, passing 13 DME we have a look at our altimeter, see that it reads 4625' and we know we are in the ball park.
Or, if done at the altitude we say:
At 13 DME I want to be 13 x 300 = 3900' above the airfield, that equals 4650' given a field elevation of 750' (rounded.)
Then passing 4650' we look at our DME and read 13.1, we see we are in the ball park and therefore safe.
If we were using QFE, the above would all be the same except we'd use 3900' instead of 4650'.
If we were using QNE for some reason we'd use 4650' and make an adjustment for the local pressure.
Please, explain, because I'm not getting it, how you would use your figure of 3150'.
P.S., in case it's not clear, there is no sarcasm intended in any of what I've just written, I honestly want to understand what you're talking about.
With 1013 set on a standard day, at an altitude of 3900' or a flight level of 139, you will be 3150 feet above the aerodrome. If you them correct for altitude/pressure you get your check height. Why is that so hard to understand?
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Remoak,
I did look in a couple of my textebooks, heres what they say.
QNE. Is ot an altimeter setting, but is the height shown at touchdown on the altimeter with 1013.2 mb set on the subscale. QNE is used at very high aerodromes where the QFE pressure is so low it cannot be set on the subscale.
763 is not very high.
QNE. Common usage accepts QNE as the ISA standard pressure setting of 1013.2 hpa. However another definition of QNE is the altitude displayed on the altimeter at touchdown with 1013 set on the altimeter subscale. Also referred to as the landing altimeter setting.
Within the latter meaning QNE is only likely to be used when an extremly low QNH is outside an aircrafts altimeter sub-cale range, and the pilot requests QNE from ATC.
Again very unlikely unless your in a cyclone/hurricane. In 22 years of flying I have never had to use it.
So we're only going to use it in 2 instances unless your on your on your own time in your own aircraft on a nice visual day and fancy giving it a go for a giggle.
I did look in a couple of my textebooks, heres what they say.
QNE. Is ot an altimeter setting, but is the height shown at touchdown on the altimeter with 1013.2 mb set on the subscale. QNE is used at very high aerodromes where the QFE pressure is so low it cannot be set on the subscale.
763 is not very high.
QNE. Common usage accepts QNE as the ISA standard pressure setting of 1013.2 hpa. However another definition of QNE is the altitude displayed on the altimeter at touchdown with 1013 set on the altimeter subscale. Also referred to as the landing altimeter setting.
Within the latter meaning QNE is only likely to be used when an extremly low QNH is outside an aircrafts altimeter sub-cale range, and the pilot requests QNE from ATC.
Again very unlikely unless your in a cyclone/hurricane. In 22 years of flying I have never had to use it.
So we're only going to use it in 2 instances unless your on your on your own time in your own aircraft on a nice visual day and fancy giving it a go for a giggle.
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All 3 video's now on youtube
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I do however now see were you get 3150 from. Its your height above the airfield with 1013 set on a standard day if you fly at 3900 or if you prefer fl 39.
However to be on a 3 degree slope at 13nm you have to be 3900 above the airfield not 3150 so your still not relating 3150 to a crosscheck on glide at 13nm.
Plus why on earth give your answer in QFE & QNE and then move on to say its all very simple math. QNE is not simple math.
Lets look at an example.
QNH 960 hpa, airfield elevation 763 feet, pressure setting(on altimeter) 1013. We want to find out what it would read at touchdown and at 13nm.
QNE = 1013 - 960 = 53 times 27 = 1431 + 763 = 2194.
So at touchdown the altimeter would read 2194 feet.
At 13 nm it would read 2194 + 3900 = 6094 feet.
So are you saying thats really simple mental arithmatic under pressure ? Clearly it is not.
However to be on a 3 degree slope at 13nm you have to be 3900 above the airfield not 3150 so your still not relating 3150 to a crosscheck on glide at 13nm.
Plus why on earth give your answer in QFE & QNE and then move on to say its all very simple math. QNE is not simple math.
Lets look at an example.
QNH 960 hpa, airfield elevation 763 feet, pressure setting(on altimeter) 1013. We want to find out what it would read at touchdown and at 13nm.
QNE = 1013 - 960 = 53 times 27 = 1431 + 763 = 2194.
So at touchdown the altimeter would read 2194 feet.
At 13 nm it would read 2194 + 3900 = 6094 feet.
So are you saying thats really simple mental arithmatic under pressure ? Clearly it is not.
I did manage to pass some maths courses in uni, but I don't do arithmetic calculations in the cockpit excepting time and distance with the help of the fancy watch or whiz wheel.
The main reason being that the office is moving at a great rate of knots and I have only one brain that is good for only one thing at a time - - a matter of great dissatifaction with the ex who wanted to discuss deep relationship issues while I was driving at 70+ mph in traffic
The profile view of an approach makes it plain how high I have to be where.
The main reason being that the office is moving at a great rate of knots and I have only one brain that is good for only one thing at a time - - a matter of great dissatifaction with the ex who wanted to discuss deep relationship issues while I was driving at 70+ mph in traffic
The profile view of an approach makes it plain how high I have to be where.
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My Dad once asked me to keep asking myself, when the time came:
"Who's the bigger idiot? The guy who argues with the idiot, or the idiot?"
I guess we could replace the word idiot with 'guy who is wrong', to make everyone comfortable.
Thing is, the point is moot.
The issue about altimeters is over.
It was a nice little game, but it's over.
The real-deal is the video.
Kind of balls'y to make that, don't you think?
I guess you have to give credit to the Air NZ pilots for allowing it to be filmed in the first place.
"Who's the bigger idiot? The guy who argues with the idiot, or the idiot?"
I guess we could replace the word idiot with 'guy who is wrong', to make everyone comfortable.
Thing is, the point is moot.
The issue about altimeters is over.
It was a nice little game, but it's over.
The real-deal is the video.
Kind of balls'y to make that, don't you think?
I guess you have to give credit to the Air NZ pilots for allowing it to be filmed in the first place.
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in post 32 you related your math directly to my 13nm check question. You quoted the question above your math. You then produced an answer for all to see of 3150. The wrong answer to a 13nm check given the airfield elevation of 763.
If you say its QNE on a standard day 3150 is still wrong as you cannot then relate it to a 13nm check which was the question you yourself quoted. At 13nm it would be 4650 when related to 13nm.
Its also unprofessional to challenge someones credentials just because they ask a question. My view is that a professional should ask a question if he/she is unsure about something. It is also professional, and good crm, to encourage crew to ask and challenge. That is how we learn.
On the subject of gross error checks it was the investigators view that the altitude crosscheck/approach fix on an ILS is primarily there to confirm that you have the correct pressure on your altimeter not that the glidslope is correct. News to me so I learnt about gross error checks from that after 22 years of professional aviation. Same result though if it does'nt tie up and imc go-around.
So there you go remoak whichever way I slice it I can't agree with you. The charitable might say your original answer was just a bit esoteric or mischevious, to me it was just plain wrong.
Sorry about the seperate posts but my computer keeps wiping them if I write too much or spend too long doing it and I'm too dim to figure it out.
If you say its QNE on a standard day 3150 is still wrong as you cannot then relate it to a 13nm check which was the question you yourself quoted. At 13nm it would be 4650 when related to 13nm.
Its also unprofessional to challenge someones credentials just because they ask a question. My view is that a professional should ask a question if he/she is unsure about something. It is also professional, and good crm, to encourage crew to ask and challenge. That is how we learn.
On the subject of gross error checks it was the investigators view that the altitude crosscheck/approach fix on an ILS is primarily there to confirm that you have the correct pressure on your altimeter not that the glidslope is correct. News to me so I learnt about gross error checks from that after 22 years of professional aviation. Same result though if it does'nt tie up and imc go-around.
So there you go remoak whichever way I slice it I can't agree with you. The charitable might say your original answer was just a bit esoteric or mischevious, to me it was just plain wrong.
Sorry about the seperate posts but my computer keeps wiping them if I write too much or spend too long doing it and I'm too dim to figure it out.
Gentlemen
Un f*^#ing believable. How to make a simple job hard in one easy lesson.
In the past 40 years of flying I do not recall ever hearing of or having a discussion about QNE.
QFE is used as a reference in a very small percentage of the flying world.
QNH is the norm, and it makes the whole dist alt question one of basic primary school arithmetic. (QFE no harder but awareness needs to be a bit greater.)
Pray tell what is difficult about 13 x 300+ 750 (GOTAB)
If your limited brain power cannot work that one out whilst simultaneously trying to chew gum, go away and find a more suitable line of work.
Ashling. You refer to this as a basic (minor) error /incident. I suggest to you you take the circumstances to lightly. In another very similar scenario 300 odd Koreans failed to come home. There are doubtless several other incidents that have come perilously close, in similar circumstances.
To come below the minimum glideslope intercept altitude without a verified/xchecked glideslope is as criminal as busting a minimum descent altitude or passing a minimum decision altitude in less than minimum conditions without making that decision.
Do you get my drift. It is a minimum and is no less inviolable than any other minimum.
And sunshine if you do it while I am checking you, you will be travelling somewhere behind row 1 on the way home, I couldn't give a **** about your ego.
minimumly yours
maui
Un f*^#ing believable. How to make a simple job hard in one easy lesson.
In the past 40 years of flying I do not recall ever hearing of or having a discussion about QNE.
QFE is used as a reference in a very small percentage of the flying world.
QNH is the norm, and it makes the whole dist alt question one of basic primary school arithmetic. (QFE no harder but awareness needs to be a bit greater.)
Pray tell what is difficult about 13 x 300+ 750 (GOTAB)
If your limited brain power cannot work that one out whilst simultaneously trying to chew gum, go away and find a more suitable line of work.
Ashling. You refer to this as a basic (minor) error /incident. I suggest to you you take the circumstances to lightly. In another very similar scenario 300 odd Koreans failed to come home. There are doubtless several other incidents that have come perilously close, in similar circumstances.
To come below the minimum glideslope intercept altitude without a verified/xchecked glideslope is as criminal as busting a minimum descent altitude or passing a minimum decision altitude in less than minimum conditions without making that decision.
Do you get my drift. It is a minimum and is no less inviolable than any other minimum.
And sunshine if you do it while I am checking you, you will be travelling somewhere behind row 1 on the way home, I couldn't give a **** about your ego.
minimumly yours
maui
Last edited by maui; 5th Feb 2007 at 01:00.
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Maui I may have called it a basic error but were did I call it a minor one ?
I have tried to look at the reasons behind their error by suggesting conditioning, capacity overload, poor prioritisation and fixation as contributing factors. I think those are fair things to look at and are all mentioned in the report.
Looking for reasons does not mean I absolve the crew from their professonal resposibility. They made a serious of potential fatal errors from capture onwards but they at least dug themselves out of it, albeit late on, and did the correct things to sort it from then on.
The written report records the high degree of professonalism the crew displayed and the incident is all the more significant because of the crews professonalism. This was not a gash crew throwing caution to the wind. If it could happen to them it could happen to any of us so best to try to understand how and why they got it wrong. Surely that is the purpose of the videos.
I would urge all to take the time to read the report, ratherbeflying has given us a link to it in an earlier post.
Yes Maui I do have an ego, I rather suspect you do too. Your last sentence is one that tends to be used by a bully, thats the impression you give me of yourself.
I have tried to look at the reasons behind their error by suggesting conditioning, capacity overload, poor prioritisation and fixation as contributing factors. I think those are fair things to look at and are all mentioned in the report.
Looking for reasons does not mean I absolve the crew from their professonal resposibility. They made a serious of potential fatal errors from capture onwards but they at least dug themselves out of it, albeit late on, and did the correct things to sort it from then on.
The written report records the high degree of professonalism the crew displayed and the incident is all the more significant because of the crews professonalism. This was not a gash crew throwing caution to the wind. If it could happen to them it could happen to any of us so best to try to understand how and why they got it wrong. Surely that is the purpose of the videos.
I would urge all to take the time to read the report, ratherbeflying has given us a link to it in an earlier post.
Yes Maui I do have an ego, I rather suspect you do too. Your last sentence is one that tends to be used by a bully, thats the impression you give me of yourself.
Ashling
Not a bully by any means. Just someone who has seen a lot and is sick and tired of do-gooders trying to see the best in situations/people and downgrading the serious nature of some occurences.
Dear heart, if the crew had not breached the minimum glideslope intercept altitude without first verifying the integrity of the glideslope, by the designated means, we would not be having this discussion. That they did, is not a small oversight that could happen to anyone. It is a fudemental and deliberate breach of a requirement, just as breaching an MDA/DA. There but for the grace etc only applys to other crews who equally disregard required procedures.
By your reasoning driving through a red light or a compulsory stop sign is equally a small oversight, and never a deliberate act.(by the way I recommend license suspension for that one too)
Don't get me wrong, I commend the crew for detecting and acting on their stuff up, but that indeed is what it was, a stuff up either by ommission or commission.
When are we going to get away from patting people on the back for fixing up their own creations.
Politically incorrect? Too old to care!
Maui
Not a bully by any means. Just someone who has seen a lot and is sick and tired of do-gooders trying to see the best in situations/people and downgrading the serious nature of some occurences.
Dear heart, if the crew had not breached the minimum glideslope intercept altitude without first verifying the integrity of the glideslope, by the designated means, we would not be having this discussion. That they did, is not a small oversight that could happen to anyone. It is a fudemental and deliberate breach of a requirement, just as breaching an MDA/DA. There but for the grace etc only applys to other crews who equally disregard required procedures.
By your reasoning driving through a red light or a compulsory stop sign is equally a small oversight, and never a deliberate act.(by the way I recommend license suspension for that one too)
Don't get me wrong, I commend the crew for detecting and acting on their stuff up, but that indeed is what it was, a stuff up either by ommission or commission.
When are we going to get away from patting people on the back for fixing up their own creations.
Politically incorrect? Too old to care!
Maui
This incident is another reminder of the problem of complacency in our industry. We easily forget that systems are rarely perfect and thus require some human intervention to mitigate design weaknesses. ILS’s have always required a component to check that the GS is correctly positioned or that a false beam has not been intercepted. Historically this component used markers or a locator beacon; more recently these have been replaced with a distance (DME) check; both require the crew to check the altitude a predetermined point. With the advent of FMS/EFIS maps, RNAV, and very reliable ILS, there are many opportunities to overlook this important check.
IIRC there was a similar incident involving an incorrect ILS test mode at Rio. In this incident the EGPWS alerted the close proximity of terrain. Interestingly the following aircraft, unaware of the problem, crosschecked the marker (DME?) altitude and then checked the QNH with ATC to resolve the apparent altitude error; the QNH was correct, thus a GA flown.
Other examples of error provoking situations (human factors) encountered in low approach incidents can bee seen in ‘TAWS Saves’.
All of these incidents provide examples of the often unavoidable human error (particularly where both crew experience the same error at the same time), which with the failure to use simple crosschecks or safety tools such as altitude-range tables result in hazardous situations.
Note the importance of always checking the altitude element before range, and in referencing distance to the threshold – beware offset DMEs. There is also merit in always displaying EGPWS terrain on at least one EFIS display to avoid a surprise alert or warning.
Situation awareness is a major factor, but not necessarily that it was lost, more likely that it was never adequately gained or provisioned. SA is our understanding of the combination of the real world and our mental model, we have to perceive the world correctly and maintain a good mental model (memory, experience, planning ahead). The latter commences with the approach briefing – the procedure, nav aids, check altitudes, etc. Our understanding is updated as the approach progresses; the mental model must be compared with the real world by the use of crosschecks and monitoring. If a crosscheck fails or the real world does not agree with the mental model (the briefed plan), then most probably an error exists; a normal (SOP) response would be a GA and then the source of the error/discrepancy can be determined at a safe altitude. Avoid the error of making the data (real or memory) fit the picture – confirmation bias.
“The approach briefing is the flight plan for the mind” FSF presentation Phoenix May 06.
"We (pilots) are children of the magenta line" Don Bateman, Chief Designer GPWS/EGPWS, Honeywell.
The NZ video is available on CD from Flight Safety Foundation.
IIRC there was a similar incident involving an incorrect ILS test mode at Rio. In this incident the EGPWS alerted the close proximity of terrain. Interestingly the following aircraft, unaware of the problem, crosschecked the marker (DME?) altitude and then checked the QNH with ATC to resolve the apparent altitude error; the QNH was correct, thus a GA flown.
Other examples of error provoking situations (human factors) encountered in low approach incidents can bee seen in ‘TAWS Saves’.
All of these incidents provide examples of the often unavoidable human error (particularly where both crew experience the same error at the same time), which with the failure to use simple crosschecks or safety tools such as altitude-range tables result in hazardous situations.
Note the importance of always checking the altitude element before range, and in referencing distance to the threshold – beware offset DMEs. There is also merit in always displaying EGPWS terrain on at least one EFIS display to avoid a surprise alert or warning.
Situation awareness is a major factor, but not necessarily that it was lost, more likely that it was never adequately gained or provisioned. SA is our understanding of the combination of the real world and our mental model, we have to perceive the world correctly and maintain a good mental model (memory, experience, planning ahead). The latter commences with the approach briefing – the procedure, nav aids, check altitudes, etc. Our understanding is updated as the approach progresses; the mental model must be compared with the real world by the use of crosschecks and monitoring. If a crosscheck fails or the real world does not agree with the mental model (the briefed plan), then most probably an error exists; a normal (SOP) response would be a GA and then the source of the error/discrepancy can be determined at a safe altitude. Avoid the error of making the data (real or memory) fit the picture – confirmation bias.
“The approach briefing is the flight plan for the mind” FSF presentation Phoenix May 06.
"We (pilots) are children of the magenta line" Don Bateman, Chief Designer GPWS/EGPWS, Honeywell.
The NZ video is available on CD from Flight Safety Foundation.
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Maui
I agree with you on the fundamental nature of the error and, as I have said before, the necessity of following minimums at whatever level. However I cannot agree with you that it was a deliberate error, I just don't see that at all. Yes they should have realised at glidescope capture that what was happening no longer fitted with the plan or the chart and either executed a go-around, especially as their speed was high, at that point or focused on resolving that discrepancy. In particular the 3rd pilot should have had enough spare to see what was going on. Clearly they did'nt do this but for it to be deliberate they would have to be aware they were doing it and I don't see this.
I agree too that however well you do to recover from your stuff up its still a stuff up and should be seen as such. If the stuff up is bad enough then clearly appropriate action would need to be taken. This incident would certainly merit action being taken.
As far as my driving goes I have bust several stop signs but thankfully the cop that once pulled me over had a bleeding heart so I kept my clean license. Sadly for me the speed camera did'nt have a bleeding heart so its no longer a clean license. Both acts of criminality were deliberate on my part. Getting caught was'nt.
Do you speed ? Or have you already self suspended your license ?
I agree with you on the fundamental nature of the error and, as I have said before, the necessity of following minimums at whatever level. However I cannot agree with you that it was a deliberate error, I just don't see that at all. Yes they should have realised at glidescope capture that what was happening no longer fitted with the plan or the chart and either executed a go-around, especially as their speed was high, at that point or focused on resolving that discrepancy. In particular the 3rd pilot should have had enough spare to see what was going on. Clearly they did'nt do this but for it to be deliberate they would have to be aware they were doing it and I don't see this.
I agree too that however well you do to recover from your stuff up its still a stuff up and should be seen as such. If the stuff up is bad enough then clearly appropriate action would need to be taken. This incident would certainly merit action being taken.
As far as my driving goes I have bust several stop signs but thankfully the cop that once pulled me over had a bleeding heart so I kept my clean license. Sadly for me the speed camera did'nt have a bleeding heart so its no longer a clean license. Both acts of criminality were deliberate on my part. Getting caught was'nt.
Do you speed ? Or have you already self suspended your license ?
Ashling
You have a very cavalier approach to the road rules. Having a daughter with serious injury and a destroyed vehicle from a clown like you running a red light, I do not treat such an offence lightly. But we digress.
A minima is published on the chart. You read it before the approach,and you have the chart visible for reference during the approach. You brief for the entire approach and missed approach. If you go lower than the minima without the appropriate reference, according to your philosophy, that is not a deliberate act. My last word. Bollox
Maui
You have a very cavalier approach to the road rules. Having a daughter with serious injury and a destroyed vehicle from a clown like you running a red light, I do not treat such an offence lightly. But we digress.
A minima is published on the chart. You read it before the approach,and you have the chart visible for reference during the approach. You brief for the entire approach and missed approach. If you go lower than the minima without the appropriate reference, according to your philosophy, that is not a deliberate act. My last word. Bollox
Maui
