The 80 knot call - potential for confusion?
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The 80 knot call - potential for confusion?
In the B737 simulator the instructor can feed an airspeed error into the captain's or first officer's ASI. 25 knots is a fair and reasonable figure.
During take off the PNF calls 80 knots on his own ASI. By the time he actually annunciates the words his ASI is probably around 87 knots depending on speed of acceleration - especially if he had called a fraction late. I have never seen a call made when the ASI is less than 80 knots.
The PF who is steering the aircraft down the centre line glances at his own ASI to check the reading and sees a reading of 70 knots and accelerating. It might even be 98 knots and accelerating.
What to do? Abort or go? It is not a serious problem in itself as there is not only a standby ASI for comparison, but also various ground speed read-outs. It could be argued that as Boeing recommend that one should not abort for a Master Caution above 80 knots, then as the ASI problem is not serious (it just needs time to sort out the problem), the pilot should not abort because of an ASI discrepancy during the take off run above 80 knots.
We often see momentary confusion in the simulator when an ASI difference is picked up as the aircraft is accelerating quickly past 80 knots. Sometimes an abort is initiated and sometimes the PF will rotate on the "Rotate" call regardless of what his own ASI is reading. Quick thinking is needed.
Seems to me that by continuing the take off roll, there is more time available for the PNF to read the three ASI's and compare groundspeeds as well, and have a pretty good idea which one is wrong by the time the VR speed is reached. Much safer than a hasty abort that is not warranted? Any thoughts?
It is difficult to assess which ASI reading is faulty in the time available and often the best solution is to keep the aircraft on the ground longer than normal - but to always continue the take off roll rather than abort.
During take off the PNF calls 80 knots on his own ASI. By the time he actually annunciates the words his ASI is probably around 87 knots depending on speed of acceleration - especially if he had called a fraction late. I have never seen a call made when the ASI is less than 80 knots.
The PF who is steering the aircraft down the centre line glances at his own ASI to check the reading and sees a reading of 70 knots and accelerating. It might even be 98 knots and accelerating.
What to do? Abort or go? It is not a serious problem in itself as there is not only a standby ASI for comparison, but also various ground speed read-outs. It could be argued that as Boeing recommend that one should not abort for a Master Caution above 80 knots, then as the ASI problem is not serious (it just needs time to sort out the problem), the pilot should not abort because of an ASI discrepancy during the take off run above 80 knots.
We often see momentary confusion in the simulator when an ASI difference is picked up as the aircraft is accelerating quickly past 80 knots. Sometimes an abort is initiated and sometimes the PF will rotate on the "Rotate" call regardless of what his own ASI is reading. Quick thinking is needed.
Seems to me that by continuing the take off roll, there is more time available for the PNF to read the three ASI's and compare groundspeeds as well, and have a pretty good idea which one is wrong by the time the VR speed is reached. Much safer than a hasty abort that is not warranted? Any thoughts?
It is difficult to assess which ASI reading is faulty in the time available and often the best solution is to keep the aircraft on the ground longer than normal - but to always continue the take off roll rather than abort.
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If an 80kts airspeed call shows an out of limits difference between the PF and PNF ASI then it is a Command call to abort, gently, no rush, no need for reverse thrust above idle, or RTO brakes, yes?
What the standby ASI is reading is often not relevant in todays modern aircraft as it is possible to dispatch, according to the MEL, without it, it is no longer considered vital in, for instance, the B747-400 due to the amount of Independence and backup that goes in to the two main systems.
This is my humble opinion!
So I would suggest that building anything more than an instrument failure into this situation in the SIM is departing reality.
If you really want to roll a grenade into the 'box', when all the checking is over, then a generator failure at about V1 minus 10kts should do! This may result in a high speed abort, a wheel well fire and a pax evacuation, thus bringing the session to a successful close!
What the standby ASI is reading is often not relevant in todays modern aircraft as it is possible to dispatch, according to the MEL, without it, it is no longer considered vital in, for instance, the B747-400 due to the amount of Independence and backup that goes in to the two main systems.
This is my humble opinion!
So I would suggest that building anything more than an instrument failure into this situation in the SIM is departing reality.
If you really want to roll a grenade into the 'box', when all the checking is over, then a generator failure at about V1 minus 10kts should do! This may result in a high speed abort, a wheel well fire and a pax evacuation, thus bringing the session to a successful close!
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Although not a line pilot whilst doing the MCC course we used the 80kts call as a "are you still alive" call not an error check.
This may have just been simplified for the course though.
This may have just been simplified for the course though.
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It's a Captain's decision, if you know what to do, both an abort or a Go are valid decisions. No absolute thruth. Whatever you decide, do it convincingly.
Personally I would continue, using the STBY one.
But actually, I would have preferred if the Birgenair' donkey had aborted in S. Domingo, instead of killing everybody in his 757
Personally I would continue, using the STBY one.
But actually, I would have preferred if the Birgenair' donkey had aborted in S. Domingo, instead of killing everybody in his 757
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It's quite simple - you do what you briefed to do.
If your brief states "Up to nn kts we will stop for any malfunction - above nn kts up to V1 we will stop only for engine failure, fire, smoke indication, blocked runway <flood, famine> ...." then you stop. Woe betide the captain who goes against briefing without a good reason.
IMHO an ASI disagreement is a very good reason to stop, since you are well below V1.
I can't think of a good reason to continue the takeoff.
If your brief states "Up to nn kts we will stop for any malfunction - above nn kts up to V1 we will stop only for engine failure, fire, smoke indication, blocked runway <flood, famine> ...." then you stop. Woe betide the captain who goes against briefing without a good reason.
IMHO an ASI disagreement is a very good reason to stop, since you are well below V1.
I can't think of a good reason to continue the takeoff.
The 80 knots call is also a prompt to check the autothrust is in the correct mode. On the 747, if THR HLD is not annunciated, this should prompt a disconnect of the autothrust. (Both 744 and classic with FFRAT). Also, it's areminder to set the trust manually to GA power should take off power not be set by then.
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"there is no reason the PNF cant check both ASI's and the STBY to make sure they are both reading the same value prior to the 80kt call"
This might be a problem on the newer glass cockpit aircraft with LCD displays, where the angle of view may not provide the PNF a clear view of all the instruments.
I'm also thinking that the "window" to check all three indicators may be limited if the displays don't start moving until 35 or in some cases 45 kts. As an example, the captain of a 747-400, in a recent incident, didn't notice his airspeed indicator was completely U/S until the F/O called 80kts (An engineer had not hooked up the pitot/static plumbing to the Left Air Data Computer). The takeoff was safely aborted before the aircraft reached much higher speeds.
The very latest 747-400's use a single tiny standby instrument which the average person might find difficult to read, let alone fly an aircraft with.
I'm sure aborting on the ground at low speeds would be far safer than only having one pilot who can see only some of the instruments.... and having a half-serviceable aircraft where any number of systems may be degraded as a result of the faulty airspeed data (Engines, FMC, Stall warning, Flap Load Relief, Aileron Lockout, Autopilot, etc).
Where there's smoke, there may be fire. Who's to say that the F/O's ADC plumbing might suddenly come adrift also?
Hope this helps.
Regards.
Q.
P.S. Don't forget the accident where the pilot-statics had been taped over on a 757(?) and the pilots didn't have a clue how fast or how high they were flying, resulting in the deaths of all those on board.
This might be a problem on the newer glass cockpit aircraft with LCD displays, where the angle of view may not provide the PNF a clear view of all the instruments.
I'm also thinking that the "window" to check all three indicators may be limited if the displays don't start moving until 35 or in some cases 45 kts. As an example, the captain of a 747-400, in a recent incident, didn't notice his airspeed indicator was completely U/S until the F/O called 80kts (An engineer had not hooked up the pitot/static plumbing to the Left Air Data Computer). The takeoff was safely aborted before the aircraft reached much higher speeds.
The very latest 747-400's use a single tiny standby instrument which the average person might find difficult to read, let alone fly an aircraft with.
I'm sure aborting on the ground at low speeds would be far safer than only having one pilot who can see only some of the instruments.... and having a half-serviceable aircraft where any number of systems may be degraded as a result of the faulty airspeed data (Engines, FMC, Stall warning, Flap Load Relief, Aileron Lockout, Autopilot, etc).
Where there's smoke, there may be fire. Who's to say that the F/O's ADC plumbing might suddenly come adrift also?
Hope this helps.
Regards.
Q.
P.S. Don't forget the accident where the pilot-statics had been taped over on a 757(?) and the pilots didn't have a clue how fast or how high they were flying, resulting in the deaths of all those on board.
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Historically, the 80 Knot call was a check that the Pitot Static system was functional - i.e. the probes weren't blocked. Since then it seems to have developed into a cross check for an IAS discrepancy and perhaps other things, but it doesn't do any harm to consider the original intention for some of the SOPs that are in daily use.
I would hope that most pilots would wish not to go aviating if the Pitot Static system is not functional. I can think of two occasions in recent history when B757s became airborne with blocked pitot probes and one of them didn't make it back to the airport...
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I would hope that most pilots would wish not to go aviating if the Pitot Static system is not functional. I can think of two occasions in recent history when B757s became airborne with blocked pitot probes and one of them didn't make it back to the airport...
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AFAIK the 80kts (or 100kts - depending on type) call serves three purposes:
1. ASI serviceability check.
2. Incapacitation check.
3. End of 'Low Speed Regime'.
In the High Speed Regime (up to V1) an abort should only be carried out for:
1. Engine Fail/Fire (a non-supressed Master Warn)
2. Any event/failure which might make the aircraft unsafe/unable to fly.
Number 2 is a general getout clause...and I think the ASI failure in the High Speed Regime would come under that heading.
1. ASI serviceability check.
2. Incapacitation check.
3. End of 'Low Speed Regime'.
In the High Speed Regime (up to V1) an abort should only be carried out for:
1. Engine Fail/Fire (a non-supressed Master Warn)
2. Any event/failure which might make the aircraft unsafe/unable to fly.
Number 2 is a general getout clause...and I think the ASI failure in the High Speed Regime would come under that heading.
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If modern pilots had the ATTITUDE/POWER basic skill like back in the time, a blocked pitot would not be such a big deal, and certainly not a reason to die.
Very sad, but the Birgenair 757 cockpit was manned by three *******
Very sad, but the Birgenair 757 cockpit was manned by three *******
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On the 747-400 there is an EICAS message "IAS DISAGREE". It comes up as a CAUTION along with a aural beeper.
This comes on when the Captains and F/O's airspeed indicators differ by five knots or more. It is inhibited until the disagreement lasts for more than five seconds.
This comes on when the Captains and F/O's airspeed indicators differ by five knots or more. It is inhibited until the disagreement lasts for more than five seconds.
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I agree with LEM. Even in the air when there is a difference between ASI's, B737 first recall items : disconnect automatics.
So fly manually thrust and attitude.
I am not saying that it would not be a reason to abort TO. All depends on the current speed I guess (pilot's reaction time).
However, a lot of people apparently elect to abort. A few months ago during our yearly Flight Safety course, we were shown a video made by the Boeing cy in which it was said that for the moment the highest number of incidents/accidents happen as a result of an aborted Take-off. We were taught to be GO minded after 80 kts and especially nearing V1 .
Good subject, hope to get some more feedback.
All the best.
So fly manually thrust and attitude.
I am not saying that it would not be a reason to abort TO. All depends on the current speed I guess (pilot's reaction time).
However, a lot of people apparently elect to abort. A few months ago during our yearly Flight Safety course, we were shown a video made by the Boeing cy in which it was said that for the moment the highest number of incidents/accidents happen as a result of an aborted Take-off. We were taught to be GO minded after 80 kts and especially nearing V1 .
Good subject, hope to get some more feedback.
All the best.
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As mentioned above by many, the 80 kts call is also for incaptication. Let's elaborate on that a little bit, shall we? Skipper's leg, at 80 kts he blacks out, in which case, a second call from the FO, a look over to the left, then he takes control....what would you suggest the airspeed is then? At least 110/120 kts? What should he do then? A perfectly good airplane...go flying...only to try and come back alone? Most would suggest stay on the ground.
The same goes for the airspeed. I believe the objective is that PM (pilot monitoring-no longer PNF which implies doing nothing!) should compare speeds, or the annunciators if in glass flight deck, then make the call so that it is finished as the airplane passes 80 kts.(there is no reason for this call to happen much later) Still well below V1, and thus stopping safely should be no problem. Let's not forget the airplane normally touches down much faster at about the same area it reaches 80 kts on TO and still stops quite normally. Also, launching into the air with unreliable airspeed could mean a faulty ADC which will cripple a whole lot of other instruments. Electing to abort would seem more logical.
They say it's much better to be on the ground wishing to be in the sky as opposed to the other way around!
As for training in general, I believe the objective is to enhance every one's ability and confidence by making handling emergencies second nature. Creativity should not be a gross departure from reality.
The same goes for the airspeed. I believe the objective is that PM (pilot monitoring-no longer PNF which implies doing nothing!) should compare speeds, or the annunciators if in glass flight deck, then make the call so that it is finished as the airplane passes 80 kts.(there is no reason for this call to happen much later) Still well below V1, and thus stopping safely should be no problem. Let's not forget the airplane normally touches down much faster at about the same area it reaches 80 kts on TO and still stops quite normally. Also, launching into the air with unreliable airspeed could mean a faulty ADC which will cripple a whole lot of other instruments. Electing to abort would seem more logical.
They say it's much better to be on the ground wishing to be in the sky as opposed to the other way around!
As for training in general, I believe the objective is to enhance every one's ability and confidence by making handling emergencies second nature. Creativity should not be a gross departure from reality.
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A little bit off topic: I have always laughed at those "incapacitation checks".
They don't make sense to me.
First of all, an heart attack can happen at any time , and the other pilot must guarantee the proper trajectory of the airplane, incapacitation check or not.
Second, when my copilots brief for the 80 kts incapacitation check, I often reply "Ok, let's hope you are a PILOT and know what to do if my heart attack comes at 81 knots".
In other words, an 80 knots or a 500ft incapacitation check don't guarantee anything: you've been alive till a second before, you answer "checked", then comes the heart attack...
It really seems to me the equivalent of the sheep sacrifice of the ancients to the Gods
Isn't that ridiculous?
They don't make sense to me.
First of all, an heart attack can happen at any time , and the other pilot must guarantee the proper trajectory of the airplane, incapacitation check or not.
Second, when my copilots brief for the 80 kts incapacitation check, I often reply "Ok, let's hope you are a PILOT and know what to do if my heart attack comes at 81 knots".
In other words, an 80 knots or a 500ft incapacitation check don't guarantee anything: you've been alive till a second before, you answer "checked", then comes the heart attack...
It really seems to me the equivalent of the sheep sacrifice of the ancients to the Gods
Isn't that ridiculous?
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Lem and Visualappr. As you point out it becomes a question of basic instrument skills. I have had the opportunity to see an ASI fault inserted in a 737-300 simulator on several occasions with different crews. This is preceded by a full discussion on the pros and cons of an abort or continue - so its not just another bit of chicanery by an enthusiastic simulator instructor.
Despite the ideal situation of PNF spotting an ASI reading difference at the 80 knot call and advising the captain who then purses his lips and decides stopping or going it hasn't worked out that simple.
If the flight crew are not on the look-out for the fault (despite having been given the good gen at the briefing) there is several seconds of uncertainty and all the time the aircraft is accelerating fast.
To compound the problem I have also seen the PF commence rotation not on the bugs on his own ASI, but on the actual call "Rotate" by the PNF when in fact it was the PNF ASI that had the erroneous reading at the 80 knot call. The call "Rotate" when given in a firm manner is almost an instruction - not as it is meant to be, an airspeed reading like V1. "Rotate" used to be called "VR" in some airlines and still is in some.
High energy aborts are sometimes the cause of an accident and historically it is usually safer to continue a take off unless the aircraft will not fly for some reason. An ASI problem actioned well after the 80 knot call due to momentary confusion at which ASI is faulty has all the potential for a cock-up if an abort is decided. This is the advantage of simulator training - you can see the indecision that occurs when a mysterious erroneous ASI reading is discovered on the take off run. This is where good airmanship comes into play.
Despite the ideal situation of PNF spotting an ASI reading difference at the 80 knot call and advising the captain who then purses his lips and decides stopping or going it hasn't worked out that simple.
If the flight crew are not on the look-out for the fault (despite having been given the good gen at the briefing) there is several seconds of uncertainty and all the time the aircraft is accelerating fast.
To compound the problem I have also seen the PF commence rotation not on the bugs on his own ASI, but on the actual call "Rotate" by the PNF when in fact it was the PNF ASI that had the erroneous reading at the 80 knot call. The call "Rotate" when given in a firm manner is almost an instruction - not as it is meant to be, an airspeed reading like V1. "Rotate" used to be called "VR" in some airlines and still is in some.
High energy aborts are sometimes the cause of an accident and historically it is usually safer to continue a take off unless the aircraft will not fly for some reason. An ASI problem actioned well after the 80 knot call due to momentary confusion at which ASI is faulty has all the potential for a cock-up if an abort is decided. This is the advantage of simulator training - you can see the indecision that occurs when a mysterious erroneous ASI reading is discovered on the take off run. This is where good airmanship comes into play.
From personal experience (I didn’t stop); this topic, and my incident, raises some very interesting operational and human issues. The circumstances of my incident included corporate attitude, peer pressure, macho, and desire to help. However the primary issue was that the company procedure was ill-defined. After a full and frank debrief and self initiated investigation, the following was concluded:
The purpose of procedure - NFP calls 80kts - was twofold:
a) To crosscheck the ASI for errors. (N.B. PF assumed to check his ASI, but not written in the procedure).
b) To define the point beyond which an RTO is not required for a single system failure.
The investigation found that the crosscheck was a hang over from a previous operation with an older ASI sysyem and CAA inspector suggestion – it seemed to be a good thing to have. Whereas a risk assessment of the ASI / pitot static system (should be available from most manufacturers) suggested that there was a low probability of failure. (This was a modern aircraft, but with conventional instrument system).
During take off the PF would be able to check his ASI; although slightly later than 80 kts, thus at a higher speed, but training and experience enabled an accuracy check of +- 2 kts, enough for any gross error. However there was no procedure guidance as to what to do in the event of an error. The assumption was that it was a single system failure, and above 80 kts no RTO was required.
The technical debate re continuing the take off considered the issue of flight with an ASI error. Excluding the obvious gross error or total failure, the only way to determine the serviceable ASI was by comparison with the third / standby system – but there wasn’t one! The certification standard of the aircraft did not require it; later variants of the aircraft are fitted with ADCs / EFIS and have a standby ASI/Altimeter.
The certification basis of the aircraft protects the aircraft from an early rotation, limited elevator effectiveness (Vmu), and there was some protection for over-speed by the aircraft self-rotating; I also expect the end of the runway appearing would assist. For climb-out and subsequent flight the certification requires the aircraft to be in trim at V2+10; thus the PF, without over-reacting, could achieve a safe altitude to asses the situation. However nothing was found in the regulations as to how the crew would establish which ASI was correct; no doubt many assumptions based on airmanship and experience – noise, feel, trim, and power. An excellent simulator exercise for CRM and problem solving (MEL flight without the stand by ASI – the MEL assumes that the risk of ASI disagreement is low, but not impossible).
I could not find any certification requirements for an incapacitation check; this seems to be yet another of those items that could be introduced (operator or CAA inspector) because they seem to be a good thing to do i.e. without rationale. I suspect that the probability of PF being incapacitated is far less that a multiple systems failure that could have far more serious consequences.
The current SOP on an EFIS aircraft requires an 80kt call; this is a check that power is set and that thereafter an RTO is not required for a single system failure. ASIs are checked for gross error / failure. In the event of an ADC error the EFIS comparator gives a low-level ADC alert; if time permits the third ASI/Altimeter system is checked. The aircraft is flown to a safe altitude and the situation re-evaluated using the third ASI to resolve any ambiguity. The certification of a low-level alert suggests that the CAA condone continuing the takeoff; this may be due to the alert being an ADC comparator, the error could be in the ASI, VSI, or altimeter. Thus at 80 kts the Captain can still decide to abort, his call: if so this may be the safest option overall. Aircraft certification does not take into account, poor weather, inexperienced crew, complex ATC scenarios, high terrain, and all of those airframe systems that use ADC input (which we all know well, at least on examination day).
Epilogue:
Company procedures rethought, judged against the quantifiable risks for the aircraft type / operation, and now rewritten. Captains are in command; have a no blame / fair safety culture. Personal self-assessment / de-brief complete, studying for CRM instructor ticket. Beware of introducing procedures without a risk assessment and any well thought out rationale. Always ask the inspector ‘why’, and get a full justification for any request to introduce additional procedures (requirements etc); there are enough vital activities to do with more clutter.
The purpose of procedure - NFP calls 80kts - was twofold:
a) To crosscheck the ASI for errors. (N.B. PF assumed to check his ASI, but not written in the procedure).
b) To define the point beyond which an RTO is not required for a single system failure.
The investigation found that the crosscheck was a hang over from a previous operation with an older ASI sysyem and CAA inspector suggestion – it seemed to be a good thing to have. Whereas a risk assessment of the ASI / pitot static system (should be available from most manufacturers) suggested that there was a low probability of failure. (This was a modern aircraft, but with conventional instrument system).
During take off the PF would be able to check his ASI; although slightly later than 80 kts, thus at a higher speed, but training and experience enabled an accuracy check of +- 2 kts, enough for any gross error. However there was no procedure guidance as to what to do in the event of an error. The assumption was that it was a single system failure, and above 80 kts no RTO was required.
The technical debate re continuing the take off considered the issue of flight with an ASI error. Excluding the obvious gross error or total failure, the only way to determine the serviceable ASI was by comparison with the third / standby system – but there wasn’t one! The certification standard of the aircraft did not require it; later variants of the aircraft are fitted with ADCs / EFIS and have a standby ASI/Altimeter.
The certification basis of the aircraft protects the aircraft from an early rotation, limited elevator effectiveness (Vmu), and there was some protection for over-speed by the aircraft self-rotating; I also expect the end of the runway appearing would assist. For climb-out and subsequent flight the certification requires the aircraft to be in trim at V2+10; thus the PF, without over-reacting, could achieve a safe altitude to asses the situation. However nothing was found in the regulations as to how the crew would establish which ASI was correct; no doubt many assumptions based on airmanship and experience – noise, feel, trim, and power. An excellent simulator exercise for CRM and problem solving (MEL flight without the stand by ASI – the MEL assumes that the risk of ASI disagreement is low, but not impossible).
I could not find any certification requirements for an incapacitation check; this seems to be yet another of those items that could be introduced (operator or CAA inspector) because they seem to be a good thing to do i.e. without rationale. I suspect that the probability of PF being incapacitated is far less that a multiple systems failure that could have far more serious consequences.
The current SOP on an EFIS aircraft requires an 80kt call; this is a check that power is set and that thereafter an RTO is not required for a single system failure. ASIs are checked for gross error / failure. In the event of an ADC error the EFIS comparator gives a low-level ADC alert; if time permits the third ASI/Altimeter system is checked. The aircraft is flown to a safe altitude and the situation re-evaluated using the third ASI to resolve any ambiguity. The certification of a low-level alert suggests that the CAA condone continuing the takeoff; this may be due to the alert being an ADC comparator, the error could be in the ASI, VSI, or altimeter. Thus at 80 kts the Captain can still decide to abort, his call: if so this may be the safest option overall. Aircraft certification does not take into account, poor weather, inexperienced crew, complex ATC scenarios, high terrain, and all of those airframe systems that use ADC input (which we all know well, at least on examination day).
Epilogue:
Company procedures rethought, judged against the quantifiable risks for the aircraft type / operation, and now rewritten. Captains are in command; have a no blame / fair safety culture. Personal self-assessment / de-brief complete, studying for CRM instructor ticket. Beware of introducing procedures without a risk assessment and any well thought out rationale. Always ask the inspector ‘why’, and get a full justification for any request to introduce additional procedures (requirements etc); there are enough vital activities to do with more clutter.
