Turkish airliner crashes at Schiphol
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"confess to being rather bored by all this poring over and implied criticism of the aircraft systems. It seems that one Radio Altimeter failed - so what?"
So it told the a/c it was on the ground, reduced thrust and crashed and killed people.
So it told the a/c it was on the ground, reduced thrust and crashed and killed people.
The missing factor?
I get the idea that there was likely some other factor that affected the crew performance. Just does not seem to add up otherwise.
Incapacitation has already been mentioned as a posibility, or some other issue that they were dealing with.
That's my guess anyway
Incapacitation has already been mentioned as a posibility, or some other issue that they were dealing with.
That's my guess anyway
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As I said in 1509, we already have the required system to avoid this particular accident - it just requires a tweak in the software to enable it. No 'new' system, we are all used to having it - nothing to anger the Rainboe, nothing to worry the luddites.
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I see we are still well into the blame crew vs. blame aircraft debate. and those who take sides are missing a part of the story and not looking at the whole picture
On the crew blame side we find:
On the other corner
and so on.
When several slices line-up it's a matter of relative position, some will call it hazard, probability whatever, none of the slices is to be blamed individually for their alignment.
I prefer that other approach:
Though it looks like the investigation may possibly and finally highlight training issues, I wouldn't be so quick in playing the blame game.
Regarding the other side of the story, automation:
To
the answer is that automation will never be perfect, just another slice in the equation.
Hopefully designed so that it solves more problems than it creates, I leave that to the Boeing team.
Why? you already have one for the baro altimeter.
Looks pretty sensible at first sight that no system including A/T should use disagreeing RA inputs.
to whatever Boeing considers appropriate.
Well I had second thoughts about the single channel RETARD. If you want alpha floor protection during a "speed deselect" single channel approach then it is wise that those throttles retard during the flare in case you forgot to retard manually as not retarding also has its consequences.
Well I'd reckon the RETARD thing only happens in APP or LNAV/VNAV.
I'll stick with a relatively simple comparator. I'd be happy if it gets implemented. I usually put the gear down but I'm more than happy to have the GPWS yell at me. Rememeber there are those who have landed gear up and those ...
(Edited) To safta: thanks for sharing
On the crew blame side we find:
Remember the old adage:
Power+Attitude=Performance?
The failure of a totally unimportant item did lead to a crash because totally
incompetent pilots could not handle the failure of this totally unimportant item
and fly the aeroplane
Power+Attitude=Performance?
The failure of a totally unimportant item did lead to a crash because totally
incompetent pilots could not handle the failure of this totally unimportant item
and fly the aeroplane
It didn't. It took inept handling to do it.
This accident has happened primarily due to the crew not flying the aircraft.
what you want there is effectively pilotless aircraft
IMHO the blame sits firmly with Boeing
When several slices line-up it's a matter of relative position, some will call it hazard, probability whatever, none of the slices is to be blamed individually for their alignment.
I prefer that other approach:
I wouldn't blame the pilots, or the Turkish system in isolation ....
Yes, the failure of a relatively unimportant piece of equipment should not have led to the accident under discussion, but it did. Yes, the performance of the crew in monitoring the approach appears to have been woeful and well below the standards we as professionals would expect. But guess what, as we all know sh!t happens on a regular basis and under different circumstances I expect this should have been a non event. Just another unremarkable 'save' involving the man/machine interface gone awry yet resulting in a normal landing, leaving no one any the wiser but also leaving the potential for disaster in place for another crew on another day under a different set of circumstances.
in the past 22,700 hours I have missed traps that wore red, and were positioned right in front of my face!! I like to believe that I was fooled for a reason or reasons other than my shear incompetence
Though it looks like the investigation may possibly and finally highlight training issues, I wouldn't be so quick in playing the blame game.
Regarding the other side of the story, automation:
To
'what good is automation if it's not perfect and leads to a crash"?
Beware sugested improvements that may make matters worse
There are dangers in over-engineering systems and other unknown traps can be generated
the added complexities that were designed to make the aircraft safer, merely generated new failure modes that at times were exceedingly hard to diagnose.
To any proposal you have to ask "would this have changed the outcome of the accident", if yes you then have to analyse if you've caused a problem elsewhere in the chain.
More complicated systems, More design errors, increased cockpit confusion.
i would rather have a simple A/T malfunction than someone flashing/shouting 'Radalt Comparator Warning' as well.
if the radalts disagree they should both be discounted and the "system" told to disregard their inputs.
firstly if you want a system with rad alt comparison and rejection of a 'bad' input you need 3 rad alts
No, it is simple: if you crosscheck and notice data does not make sence, bail out ...
Why is it possible to program a Boing 737NG to stall????
My point is that the automation should not be able to cause disaste
In single channel approach the A/T should not RETARD
My point is that the automation should not be able to cause disaste
In single channel approach the A/T should not RETARD
pilots have had the same (-8) RA reading but at altitudes higher than 2.000. So no A/T problem
It would need to be a lot more nuanced than that! You wouldn't want to fly over some of those mountains that have steep enough sides for base jumpers to leap off ...
(Edited) To safta: thanks for sharing
Last edited by ant1; 6th Mar 2009 at 21:24.
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It's not a protection protection system. It's intended as a smarter and more effective airspeed loss alert than today's stick shaker of 1970s design. I've seen others here also consider some pre-warning which kicks in prior to the traditional stick shaker.The actual annunciator may well be a stick shake or nudge. Or some other different implementation, i.e. whatever the Human Factors experts come up with as the best 
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Here's a couple of things for people to consider regarding rad alts and autopliots.
Rad alts are primarly autopilot sensors not primary flight instruments. There is one rad alt per autopilot which is used in the landing phase.
To meet the design requirements for autoland with multiple autopilots, you must have the autopilots operating independantly. Autopilots will be powered from separate electrical busses, utilize separate hydraulic systems and receive information from separate sensors. Because of this requirement, it is not possible to use rad alt info from another side to replace a bad sensor.
Rad alts monitor the aircraft height above ground. Its operates between 0 and 2500feet. Height is determined by bouncing raido signals off the ground. The frequency is in the 4.3Ghz range. Above 2500 feet, it is not used. Each rad alt has 2 antennae. One transmit and one receive. On most of the modern Boeings, the rad alt R/T and both antennae are monitored for faults and will supply fail flags for a hard fault. Intermittent faults are much harder to detect and may not show as a failure.
I spent most of my 30 years in aircraft maintenance working on B747s. I never saw a rad alt stop one from flying. I don't know of any aircraft that doesn't have an MEL to cover the dispatch of an aircraft with an inop rad alt.
Rad alts are primarly autopilot sensors not primary flight instruments. There is one rad alt per autopilot which is used in the landing phase.
To meet the design requirements for autoland with multiple autopilots, you must have the autopilots operating independantly. Autopilots will be powered from separate electrical busses, utilize separate hydraulic systems and receive information from separate sensors. Because of this requirement, it is not possible to use rad alt info from another side to replace a bad sensor.
Rad alts monitor the aircraft height above ground. Its operates between 0 and 2500feet. Height is determined by bouncing raido signals off the ground. The frequency is in the 4.3Ghz range. Above 2500 feet, it is not used. Each rad alt has 2 antennae. One transmit and one receive. On most of the modern Boeings, the rad alt R/T and both antennae are monitored for faults and will supply fail flags for a hard fault. Intermittent faults are much harder to detect and may not show as a failure.
I spent most of my 30 years in aircraft maintenance working on B747s. I never saw a rad alt stop one from flying. I don't know of any aircraft that doesn't have an MEL to cover the dispatch of an aircraft with an inop rad alt.
And why are people still harping on about the system architecture of the RA, A/T and A/P? They simply ran out of airspeed because no-one was looking.
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Maybe it was professional negligence, but assuming nothing else comes out in the report regarding the throttles being closed, do you not agree that in this particular accident, the plane would not have crashed and lives lost had the duff radalt not caused the throttles to be backed off?
As I understand it, the fault with the No.1 RadAlt (LRRA) was a known fault. One must assume therefore that it was a MEL item.
I am not familiar with the 737 MEL, but on the 747 (another Boeing) dispatch with no.1 LRRA inop was 1) not allowed ex-Main Base, and 2) carried a warning that A/T would malfunction on landing, so restricted use to manual throttle only. It seems to me that the 737 may be similar.
So, what are the MEL dispatch limitations associated with a known no.1 LRRA malfunction on the 737? Were they adhered to? Perhaps Boeing's recommendations were that A/T shouldn't have been used anyway ... ?
Yes, I agree, if nothing had gone wrong, the aircraft would probably have landed safely. But that's not the point, is it? We are surely seeking to debate whether the failure of one Radio Altimeter should really have resulted in the consequences it did. My view is that, with competent professional piloting, there is no reason why such a defect should cause this result.
JD
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Originally Posted by ant1
If you want alpha floor protection during a "speed deselect" single channel approach
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AG RVS - The Crash of Flight CI676
Different plane but still shows things can go wrong fast on approach if mistakes are made.
Speed allowed to decay too much, nose allowed to go too high on stall recovery?
Different plane but still shows things can go wrong fast on approach if mistakes are made.
Speed allowed to decay too much, nose allowed to go too high on stall recovery?
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Jumbo Driver
as I understand it, the fault with the No.1 RadAlt (LRRA) was a known fault. One must assume therefore that it was a MEL item.
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I haven't read all the posts and honestly I can't be bothered -- not when 70% are tiresome and utterly useless repetitions of finger pointing at a dead crew. Come on people, how apologetic can you get about the aircraft? Of course it is bad design to couple the A/T auto retard to only the left RA with no cross checking!
People keep mentioning 100 seconds, hands on the throttle etc. But it's very likely the crew were slowing down and configuring as those 100 seconds went by. Not unlikely, the speed trend would have seemed normal for any crew until it passed vref and went into the stall regime. How many seconds does that take with a (almost?) configured a/c? Not long!
Some compare this to a faulty light bulb –- which is almost the exact opposite of what happened here, where the crew did not over focus on the problem, they didn’t register it until it was too late.
Yes, in an ideal world that speed trend should have been noticed – but we don’t know what other things went on in that cockpit, and we don’t know when that speed would appear abnormal, i.e. what the crew was actually expecting the speed trend to be.
Why do I keep thinking that had this happened to a BA crew in an Airbus the blaming choir in this thread would have had quite a different tone?
People keep mentioning 100 seconds, hands on the throttle etc. But it's very likely the crew were slowing down and configuring as those 100 seconds went by. Not unlikely, the speed trend would have seemed normal for any crew until it passed vref and went into the stall regime. How many seconds does that take with a (almost?) configured a/c? Not long!
Some compare this to a faulty light bulb –- which is almost the exact opposite of what happened here, where the crew did not over focus on the problem, they didn’t register it until it was too late.
Yes, in an ideal world that speed trend should have been noticed – but we don’t know what other things went on in that cockpit, and we don’t know when that speed would appear abnormal, i.e. what the crew was actually expecting the speed trend to be.
Why do I keep thinking that had this happened to a BA crew in an Airbus the blaming choir in this thread would have had quite a different tone?
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Originally Posted by JD
One must assume therefore that it was a MEL item.
Originally Posted by JD
It seems to me that the 737 may be similar. So, what are the MEL dispatch limitations associated with a known no.1 LRRA malfunction on the 737?
Failure No.1 Radio Altimeter renders the GWPS inoperative. See MEL Item xx-xx.
2. The Rudder Pressure Reducer valve will remain in the high pressure state if:
(a) There is no valid radio altimeter signal.
(b) There is disagreement between two operating radio altimeters
See MEL xx-xx for following minimum manoeuvre speeds should be used during approach manoeuvring.
3. If the remaining radio altimeter fails the AFDS (both sides) will limit the bank angle to a maximum of 8 degrees in all roll modes. Use of the Autopilot/Flight Director System (AFDS) is at the discretion of the Flight Crew, since the AFDS may not command sufficient bank angle to execute proper departure and/or approach manoeuvres or make enroute course changes within airspace
limitations.
4. Failure of either Radio Altimeter renders the approach mode of the associated autopilot inoperative.
I think it is a 10 day, but cannot check right now.
Originally Posted by ant1
Yes I did, did you see #1485.
If you can point me in the right direction I'll be more tha happy and thankful
If you can point me in the right direction I'll be more tha happy and thankful
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finfly1
There are hundreds, it not thousands of components, on a modern airliner, that if they fail, and the crew just fold their arms and watch, will result in a crash/deaths 
That is why there are 2+ pilots, with Licences and qualifications, sitting at the front. Their job is to manage the aircraft systems, and intervene if/as required to ensure safety.
As I said before, a RA1 failure is so trivial it is probably not trained in the sim (and not even probably replicated in the sim design was stated earlier?), nor are countless other similar trivial failures. We train for serious system failures, and/or multiple failures, where specific knowledge and techniques are required on top of our already extensive training / qualifications.
Watching an aeroplane decelerate to the stall, with the associated RoD and/or high nose attitude, is taught in the PPL syllabus as symptons of the approaching stall. It is rather hoped not to have to revisit that area to airline pilots
For those who want software/warnings added re a RA 1 failure/misreading, the RA is a small part of the big picture. As above, following this line will result in a complete redesign of most modern airliners covering many systems / components - RA1 is just but 1 example.
NoD
"confess to being rather bored by all this poring over and implied criticism of the aircraft systems. It seems that one Radio Altimeter failed - so what?"
So it told the a/c it was on the ground, reduced thrust and crashed and killed people.
So it told the a/c it was on the ground, reduced thrust and crashed and killed people.
That is why there are 2+ pilots, with Licences and qualifications, sitting at the front. Their job is to manage the aircraft systems, and intervene if/as required to ensure safety.
As I said before, a RA1 failure is so trivial it is probably not trained in the sim (and not even probably replicated in the sim design was stated earlier?), nor are countless other similar trivial failures. We train for serious system failures, and/or multiple failures, where specific knowledge and techniques are required on top of our already extensive training / qualifications.
Watching an aeroplane decelerate to the stall, with the associated RoD and/or high nose attitude, is taught in the PPL syllabus as symptons of the approaching stall. It is rather hoped not to have to revisit that area to airline pilots
For those who want software/warnings added re a RA 1 failure/misreading, the RA is a small part of the big picture. As above, following this line will result in a complete redesign of most modern airliners covering many systems / components - RA1 is just but 1 example.
NoD
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First: I do agree that the pilots is responsible for flying.
Gegenbeispiel wrote:
But I've learned that that configuration (single channel approach) is prohibited. If it is (and I do not argue that), why is it possible? It is (and should be unless you like the Airbus design) possible to do something illegal/dangerous to the aircraft, like putting it into a stall. But that is not my piont. My point is that it is prossible to put the aircraft into a configuration that would permit the automation to stall the aircraft. If you want to stall it, do it with the yoke/throttle. The design of the automation system should not allow it.
Rainbow: I do not want to implement another safety system, this is all about removing (or rather alter) a configuration that may cause the aircraft to stall. After all single channel approach is prohibited so why not just remove the AT's ability to RETARD when you do not need it? The only thing you have to do if this feature is removed is to throttle down after touchdown. That is after all a very basic thing to do. You'll apply reverse thrust anyway.
And I cannot think of any excuses to have the AT set power to idle at touchdown instead of let the pilot do it (that is, when you're not on autoland). Moving the levers to idle isn't that much work, is it? Any one using auto-retard in manual flight? Is it perhaps a protection from overshooting the runway? Will we ever see (or have we seen) an accident where the pilots forgot to throttle down to idle after touchdown? Seems weird to me.
If there is a configuration nobody would use, and if that configuration could be dangerous, I would opt for a removal of that configuration. Single channel approach is of course fine. But could anyone please tell me of what use the auto-retard is in that configuration? Being to lazy to pull the levers to idle is not an argument (IMHO).
Gegenbeispiel wrote:
Posts: 15 bobcat4: >"Why is it possible to program a Boing 737NG to stall????"
Because it's possible to program a Boing 737NG to land.
Because it's possible to program a Boing 737NG to land.
Rainbow: I do not want to implement another safety system, this is all about removing (or rather alter) a configuration that may cause the aircraft to stall. After all single channel approach is prohibited so why not just remove the AT's ability to RETARD when you do not need it? The only thing you have to do if this feature is removed is to throttle down after touchdown. That is after all a very basic thing to do. You'll apply reverse thrust anyway.
And I cannot think of any excuses to have the AT set power to idle at touchdown instead of let the pilot do it (that is, when you're not on autoland). Moving the levers to idle isn't that much work, is it? Any one using auto-retard in manual flight? Is it perhaps a protection from overshooting the runway? Will we ever see (or have we seen) an accident where the pilots forgot to throttle down to idle after touchdown? Seems weird to me.
If there is a configuration nobody would use, and if that configuration could be dangerous, I would opt for a removal of that configuration. Single channel approach is of course fine. But could anyone please tell me of what use the auto-retard is in that configuration? Being to lazy to pull the levers to idle is not an argument (IMHO).
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Warning---GIGO?
I have given what I thought happened a few pages back.
Since someone was kind enough to post the graph/chart of the flight I wanted to point a few things out.
I will be the first to admit this is not scientific.And there are a few assumptions in here-namely, ground speed = KIAS which we know is not correct, but close enough for this project.
6.3 miles. 160 kias G/S intercept Vref + 30
5 miles. 150 kias,200 feet above g/s, vref +15
4 miles 150 kias ,100 feet above g/s ,vref +15
3 miles 145kias ,on glide, Vref +10
2 miles 125kias,on glide,Vref-5... Out of cloud. But limited visibility. Perhaps ground visual contact.But no runway. The point here, the aircraft would not have been far off from standard deck angle for an ILS.
1+ miles. Vref-40.
Based on the above speeds,I assume it took about 2 minutes 30 seconds from g/s intercept to impact.
The a/c was hot and high at first. Idle thrust would have helped the situation,
either RA induced or pilot induced.
If the a/c was on A/P, why did it overshoot the g/s intercept by 2/3 of a mile(200 feet).Based on my ruff numbers it had to hit a 4 degree glide to catch the g/s. Are we sure that the a/p was on?
I know we all assume that the initial report was accurate by the board. But, I can't help but feel this was a manual approach based on the overshoot. Maybe they expected the a/p to stay on and it didn't. is it possible that at the same time they wanted idle for this unstabilized approach, they got it via the RA 1 fault, and never knew that the a/t was off?
Did the crew get so fixated on g/s that the lost the scan . Especially as they approached what they thought would be the visual segment, when the bottom fell out? Again, the visual picture at the cloud break would have looked normal. Did all three pairs of eyes go out to find a runway?With the assumption that the A/T would keep the speed?
Anyhow, GIGO. Not too many facts to work with so far.
When will the report come out?Any ideas? The CVR and DFDR didn't get banged up to badly.
Since someone was kind enough to post the graph/chart of the flight I wanted to point a few things out.
I will be the first to admit this is not scientific.And there are a few assumptions in here-namely, ground speed = KIAS which we know is not correct, but close enough for this project.
6.3 miles. 160 kias G/S intercept Vref + 30
5 miles. 150 kias,200 feet above g/s, vref +15
4 miles 150 kias ,100 feet above g/s ,vref +15
3 miles 145kias ,on glide, Vref +10
2 miles 125kias,on glide,Vref-5... Out of cloud. But limited visibility. Perhaps ground visual contact.But no runway. The point here, the aircraft would not have been far off from standard deck angle for an ILS.
1+ miles. Vref-40.
Based on the above speeds,I assume it took about 2 minutes 30 seconds from g/s intercept to impact.
The a/c was hot and high at first. Idle thrust would have helped the situation,
either RA induced or pilot induced.
If the a/c was on A/P, why did it overshoot the g/s intercept by 2/3 of a mile(200 feet).Based on my ruff numbers it had to hit a 4 degree glide to catch the g/s. Are we sure that the a/p was on?
I know we all assume that the initial report was accurate by the board. But, I can't help but feel this was a manual approach based on the overshoot. Maybe they expected the a/p to stay on and it didn't. is it possible that at the same time they wanted idle for this unstabilized approach, they got it via the RA 1 fault, and never knew that the a/t was off?
Did the crew get so fixated on g/s that the lost the scan . Especially as they approached what they thought would be the visual segment, when the bottom fell out? Again, the visual picture at the cloud break would have looked normal. Did all three pairs of eyes go out to find a runway?With the assumption that the A/T would keep the speed?
Anyhow, GIGO. Not too many facts to work with so far.
When will the report come out?Any ideas? The CVR and DFDR didn't get banged up to badly.
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Quote Glob99, regarding my experience of a similar RA failure:
WhipS Post 1510
What was your reasoning for not turning off the RA giving the spurious reading?
The simple fact that there is no ON/OFF switch. It doesn't need one. If the data is erroneous ignore it - it's only useful for autolands, which can't be carried out if the RA fails anyway, and as an input into the air/ground sense system. If you see an erroneous indication, you know that the aircraft could potentially allow ground-only systems in flight, like thrust reverser deployment or extension of ground spoilers, and may prohibit normal in-flight system operation, as I had, so it's handy to see a false indication when you have one.
This shows the problem of non-qualified persons posting on this forum. You are questioning my piloting and command skills without the slightest idea of the aircraft systems. The question may have been asked in a genuinely inquisitive fashion, but other posts on here from people with non-aviation backgrounds have been based on equally flawed assumptions but with severe assertions that they know better than us pilots how to handle aeroplanes.
As has been posted by me and others, the cause of the accident was not the RA error but the crew's inaction in managing the flight. The trend that the pilots on here agree with this, blaming one of our own (not something we like to do) should be an indicator to the techies out there who think automation and wigglyamps are the cause and cure that you are wrong. Pilots fly aeroplanes, electronics are just there to help us do it more easily and safely.
Safta - nice one. The trim element of the stall recovery is one that could be overlooked in a panic, and it appears that it could have made all the difference.
WhipS Post 1510
What was your reasoning for not turning off the RA giving the spurious reading?
The simple fact that there is no ON/OFF switch. It doesn't need one. If the data is erroneous ignore it - it's only useful for autolands, which can't be carried out if the RA fails anyway, and as an input into the air/ground sense system. If you see an erroneous indication, you know that the aircraft could potentially allow ground-only systems in flight, like thrust reverser deployment or extension of ground spoilers, and may prohibit normal in-flight system operation, as I had, so it's handy to see a false indication when you have one.
This shows the problem of non-qualified persons posting on this forum. You are questioning my piloting and command skills without the slightest idea of the aircraft systems. The question may have been asked in a genuinely inquisitive fashion, but other posts on here from people with non-aviation backgrounds have been based on equally flawed assumptions but with severe assertions that they know better than us pilots how to handle aeroplanes.
As has been posted by me and others, the cause of the accident was not the RA error but the crew's inaction in managing the flight. The trend that the pilots on here agree with this, blaming one of our own (not something we like to do) should be an indicator to the techies out there who think automation and wigglyamps are the cause and cure that you are wrong. Pilots fly aeroplanes, electronics are just there to help us do it more easily and safely.
Safta - nice one. The trim element of the stall recovery is one that could be overlooked in a panic, and it appears that it could have made all the difference.
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Sorry BOAC, nothing in my manual, in those last pages about Min Speed Reversion, says alpha floor is not available while on GS. Very last line says "Min speed reversion i not available with A/T OFF" which is what I would expect.
On the other hand as I pointed in #1485, "alpha floor automatically engages the A/T when armed".
bobcat4:
The Auto Flight System acts according to where he thinks the aircraft is. So I would tend to think that what is needed systemswise is preventing the AFS to think he is in on the ground when he is way above.
Comparator would do the job here. There are more complicated solutions but they're made by Airbus and since I am not rated on any bus I won't comment on them.
On the other hand as I pointed in #1485, "alpha floor automatically engages the A/T when armed".
bobcat4:
The Auto Flight System acts according to where he thinks the aircraft is. So I would tend to think that what is needed systemswise is preventing the AFS to think he is in on the ground when he is way above.
Comparator would do the job here. There are more complicated solutions but they're made by Airbus and since I am not rated on any bus I won't comment on them.
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Quote:
The system should have detected:
-1- the impossible change in value
-2- huge difference between values from 2 inputs for the same parameter.
and at least alerted the crew for such a situation and/or
handled it properly by not using the invalid input!!!
1- Who is to say it's impossible?
2- How can a system decide which is the invalid input?
The system should have detected:
-1- the impossible change in value
-2- huge difference between values from 2 inputs for the same parameter.
and at least alerted the crew for such a situation and/or
handled it properly by not using the invalid input!!!
1- Who is to say it's impossible?
2- How can a system decide which is the invalid input?
The simple solution is to have the AT remeber the last reading, and the timestamp this was read. Then it should calculate the sink rate. If it's close to supersonic or some other far out speed it will simply flag the RA as unusable/faulty. What is the aircrafts envelope regarding sink rate? That would be a good limit to set for a sanity check.
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ant1:
should also add
"and the AFDS is in ALT HOLD or after G/S capture.Also not in VNAV path and flying a level segment."
I think your book is missing a bit? NB I think it should say 'or'...?
should also add
"and the AFDS is in ALT HOLD or after G/S capture.Also not in VNAV path and flying a level segment."
I think your book is missing a bit? NB I think it should say 'or'...?