Brand new Boeing unreliable airspeed procedure
Attended a meeting last week, chaired by a Boeing Technical Pilot, the new QRH unreliable airspeed checklist was discussed….the intent of the new memory items for power/attitude is to provide a safe flight regime while the QRH Performance Inflight data is referred to and more accurate power/attitude data is then applied...
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Having trawled through the AF447 thread, l paid a little more attention to the -700/800 NG figures in the cruise.
After a total of 9 years on the 'frame, for cruise l would use 2.5 or 3 degrees nose-up, depending on weight, 90 on the N1s and ensure the stab trim is 6ish. I would hold that, or request PF to maintain, until PM completed the QRH actions and the path was reassembled.
The suggested figures, if applied to this type, would almost certainly result in a climb, unhealthy in the RVSM environment?!?!
After a total of 9 years on the 'frame, for cruise l would use 2.5 or 3 degrees nose-up, depending on weight, 90 on the N1s and ensure the stab trim is 6ish. I would hold that, or request PF to maintain, until PM completed the QRH actions and the path was reassembled.
The suggested figures, if applied to this type, would almost certainly result in a climb, unhealthy in the RVSM environment?!?!
I have been reading this thread and I strongly doubt that it is a pan-Boeing procedure. The B744 would be wildly out of safe flight at any sensible CRZ altitude using these numbers.
According to the QRH, at CRZ altitudes not too far from optimum, 2.5* NU & 93% N1 will give a safe speed and close to level flight while you sort out the problem from the QRH. It is worth keeping in mind that the aircraft was flying along nice and stable until whatever the warning was is displayed. Doing nothing is a good strategy for the short term.
I await to see what Boeing actually publishes, if anything, to change the current B744 procedures.
According to the QRH, at CRZ altitudes not too far from optimum, 2.5* NU & 93% N1 will give a safe speed and close to level flight while you sort out the problem from the QRH. It is worth keeping in mind that the aircraft was flying along nice and stable until whatever the warning was is displayed. Doing nothing is a good strategy for the short term.
I await to see what Boeing actually publishes, if anything, to change the current B744 procedures.
Talk about dumbing it down.
I have thought a lot over the years about what pitch and power settings I will use if my airspeed is unreliable. I've a combination in mind for every phase of flight. If they introduce this to our QRH it will be the first checklist memory item that I will purposefully not follow.
How about the airlines spend some money training up pilots to a descent standard? .....Nah didn't think so.
I have thought a lot over the years about what pitch and power settings I will use if my airspeed is unreliable. I've a combination in mind for every phase of flight. If they introduce this to our QRH it will be the first checklist memory item that I will purposefully not follow.
How about the airlines spend some money training up pilots to a descent standard? .....Nah didn't think so.
Indeed framer - my company only updated their 737 QRH last week and this isn't in it.
Climb, cruise, descent, approach are the ballpark settings I have in kind. I also use the FPV the whole time too which is a big help.
Climb, cruise, descent, approach are the ballpark settings I have in kind. I also use the FPV the whole time too which is a big help.
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With all these changes, and as a matter of topical interest, would greatly appreciate if someone can state the latest Revision numbers and dates for the suite of Boeing 737 Classic manuals ie FCOM, QRH, FCTM, please?
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As a group of professionals, pilots are very resistant to change. This is not always a bad thing as our entire skills-set comes from a combination of repeatable experience and repetitive learnings. It does become a problem, though, when a good idea gets shot down out of stubborness before it can even be explained or understood. This may be one of those problems.
To be clear, Airbus (I speak for the A319, 320, 321 and A330) has always had a series of at most three pitch and thrust settings to be recalled in the event of Unreliable Airspeed. The intent of these simple numbers was to allow the crew to put the aircraft in a safe state while the appropriate checklist was accessed and more specific data determined. In particular, the "TOGA, 15 degrees" combination was designed to get the aircraft away from the ground if the airspeed became unreliable after V1 or in a go-around. If encountering such a problem in the cruise it has only ever been necessary to sit on your hands and touch nothing until reading the checklist. Common sense applies.
The PF onboard AF447 arguably tried to achieve the first pitch and thrust setting when seeing confusing indications on his speed-tape (TOGA and full backstick - hard to get to 15 degrees ANU in coffin-corner). It was this misunderstanding and misapplication of the memory item which precipitated the crash, not the presence of the memory item itself.
The same approach to the Airspeed Unreliable situation applies to Boeing aeroplanes, only now the addition of two pitch and thrust settings (replacing vague wording along the lines of "set pitch and thrust appropriate to the phase of flight") gives more easily recallable numbers to fly to in the event that the aeroplane encounters speed display problems close to the ground. If encountering Airspeed Unreliable in the cruise? Sit on your hands and touch nothing until reading the checklist. Common sense applies.
Airspeed Unreliable is a scenario which we all train for infrequently and can be quite insidious and very threatening in nature. Both Airbus and Boeing acknowledge that it is likely that a very high pilot workload may exist at the time it occurs (departure, go-around, manoeuvring of any nature, be it around thunderstorms or as Etihad found out when leaving Brisbane recently, due to wasp nests in the pitot tubes!) and so I think it is far better to give pilots a simple set of "time-buying" numbers to recall and execute when under duress than to ask them to create their own mental model for a range of thrust settings and speeds dependent upon a raft of external factors which differ on every flight.
I think it is good, responsible information to be added to a memory item and, if understood and applied correctly, should NEVER lead to an AF447-like scenario. Quite the opposite, in fact. In any event change is inevitable and not always bad.
ps - can't speak for other Boeings, but the 787-8 GE is "Flaps Extended - 10 degrees, 85% N1. Flaps Retracted - 4 degrees, 70% N1". I'm sure it has been tailored to type.
pps - I agree that we should ideally be flying to develop skill and not using the FCTM as a substitute for basic airmanship, but the sad truth is this; The almighty dollar, "world's best practice" and aggressive commercial risk-management are reducing the emphasis on inherent skill and development while increasing emphasis on automation-reliance and training-to-standard. It is what it is and having a set of numbers like this in a memory item is somewhat of an insurance policy against those who occupy the bottom-left of the bell-curve. If skilled pilots on this forum know better then ignore the memory item! Just make sure you can explain why you did so at the subsequent Board of Inquiry.......
To be clear, Airbus (I speak for the A319, 320, 321 and A330) has always had a series of at most three pitch and thrust settings to be recalled in the event of Unreliable Airspeed. The intent of these simple numbers was to allow the crew to put the aircraft in a safe state while the appropriate checklist was accessed and more specific data determined. In particular, the "TOGA, 15 degrees" combination was designed to get the aircraft away from the ground if the airspeed became unreliable after V1 or in a go-around. If encountering such a problem in the cruise it has only ever been necessary to sit on your hands and touch nothing until reading the checklist. Common sense applies.
The PF onboard AF447 arguably tried to achieve the first pitch and thrust setting when seeing confusing indications on his speed-tape (TOGA and full backstick - hard to get to 15 degrees ANU in coffin-corner). It was this misunderstanding and misapplication of the memory item which precipitated the crash, not the presence of the memory item itself.
The same approach to the Airspeed Unreliable situation applies to Boeing aeroplanes, only now the addition of two pitch and thrust settings (replacing vague wording along the lines of "set pitch and thrust appropriate to the phase of flight") gives more easily recallable numbers to fly to in the event that the aeroplane encounters speed display problems close to the ground. If encountering Airspeed Unreliable in the cruise? Sit on your hands and touch nothing until reading the checklist. Common sense applies.
Airspeed Unreliable is a scenario which we all train for infrequently and can be quite insidious and very threatening in nature. Both Airbus and Boeing acknowledge that it is likely that a very high pilot workload may exist at the time it occurs (departure, go-around, manoeuvring of any nature, be it around thunderstorms or as Etihad found out when leaving Brisbane recently, due to wasp nests in the pitot tubes!) and so I think it is far better to give pilots a simple set of "time-buying" numbers to recall and execute when under duress than to ask them to create their own mental model for a range of thrust settings and speeds dependent upon a raft of external factors which differ on every flight.
I think it is good, responsible information to be added to a memory item and, if understood and applied correctly, should NEVER lead to an AF447-like scenario. Quite the opposite, in fact. In any event change is inevitable and not always bad.
ps - can't speak for other Boeings, but the 787-8 GE is "Flaps Extended - 10 degrees, 85% N1. Flaps Retracted - 4 degrees, 70% N1". I'm sure it has been tailored to type.
pps - I agree that we should ideally be flying to develop skill and not using the FCTM as a substitute for basic airmanship, but the sad truth is this; The almighty dollar, "world's best practice" and aggressive commercial risk-management are reducing the emphasis on inherent skill and development while increasing emphasis on automation-reliance and training-to-standard. It is what it is and having a set of numbers like this in a memory item is somewhat of an insurance policy against those who occupy the bottom-left of the bell-curve. If skilled pilots on this forum know better then ignore the memory item! Just make sure you can explain why you did so at the subsequent Board of Inquiry.......
Last edited by Becalmed; 7th Apr 2014 at 14:52.
Originally Posted by Becalmed
This seems to be one of those problems.
Originally Posted by Becalmed
the 787-8 GE is "Flaps Extended - 10 degrees, 85% N1. Flaps Retracted - 4 degrees, 70% N1".
PS: Got your username under control there?
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I agree, Capn Bloggs, that some are just querying the numbers. Others have suggested that it will cause AF447 to repeat or that they intend to ignore the items altogether so they're the ones I hope see the benefits to understanding and applying the memory item.
4 degrees and 70% N1 (type specific) will work at any altitude where the PIC feels that the flight is placed in imminent danger by NOT adopting the settings and with the Flaps Up. Looking at the 788, 4 degrees and 70% N1 is level flight at 250 KIAS between FL150 and FL200 at up to MTOW (227-ishT).
Anywhere below that in height or weight will clearly give you a climb, albeit at a reducing angle approaching those numbers above. Anything above that is arguably too high to start panicking anyway so touch nothing and refer to the QRH or ECL.
Nothing removes the power of the PIC to vary any of this but if applied it simply buys time to get away from the rocks and start trouble-shooting.
As for my usernames, I was really hoping no-one noticed that. My muck-raking alter egos were just the wrong platform for this discussion!
4 degrees and 70% N1 (type specific) will work at any altitude where the PIC feels that the flight is placed in imminent danger by NOT adopting the settings and with the Flaps Up. Looking at the 788, 4 degrees and 70% N1 is level flight at 250 KIAS between FL150 and FL200 at up to MTOW (227-ishT).
Anywhere below that in height or weight will clearly give you a climb, albeit at a reducing angle approaching those numbers above. Anything above that is arguably too high to start panicking anyway so touch nothing and refer to the QRH or ECL.
Nothing removes the power of the PIC to vary any of this but if applied it simply buys time to get away from the rocks and start trouble-shooting.
As for my usernames, I was really hoping no-one noticed that. My muck-raking alter egos were just the wrong platform for this discussion!
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Can we use some common sense?
If you're already established in cruise and everything is working fine.... don't touch it!
The unreliable airspeed procedure calls for less power than cruise but more pitch. That sounds about right for stabilizing at a lower airspeed. Basically, the procedure is designed to apply under most circumstances—i.e., if you're on approach, on climb out, maneuvering in the terminal environment, etc.
This is a VERY generic procedure. Why are you trying to get specifics about when and where and how you should apply this? Just do it! The airspeed can be "unreliable" for many reasons. If you think it's unreliable, then follow the procedure. It's simple. Boeing has already done the work for you, Mr. Captain, just put the airplane at 4 degrees pitch and 70% N1 and that will stabilize the airplane so that you can use your exceptional thinking and experience to determine what you'll do next.
If you're already established in cruise and everything is working fine.... don't touch it!
The unreliable airspeed procedure calls for less power than cruise but more pitch. That sounds about right for stabilizing at a lower airspeed. Basically, the procedure is designed to apply under most circumstances—i.e., if you're on approach, on climb out, maneuvering in the terminal environment, etc.
This is a VERY generic procedure. Why are you trying to get specifics about when and where and how you should apply this? Just do it! The airspeed can be "unreliable" for many reasons. If you think it's unreliable, then follow the procedure. It's simple. Boeing has already done the work for you, Mr. Captain, just put the airplane at 4 degrees pitch and 70% N1 and that will stabilize the airplane so that you can use your exceptional thinking and experience to determine what you'll do next.
Usual disclaimers apply!
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the 787-8 GE is "Flaps Extended - 10 degrees, 85% N1. Flaps Retracted - 4 degrees, 70% N1
The 787 can calculate airspeed from gross weight, flap and slat position, AofA and GPS altitude.
The 787 can calculate airspeed from gross weight, flap and slat position, AofA and GPS altitude.
Originally Posted by Becalmed
Anything above that is arguably too high to start panicking anyway so touch nothing and refer to the QRH or ECL.
Up high, speed is far more critical, and I cannot see that those numbers will cause anything but severe grief. Still, nobody has actually said what the Memory Item says...
Originally Posted by Gas Path
The 787 can calculate airspeed from gross weight, flap and slat position, AofA and GPS altitude.
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Hi Bloggs,
The logic behind the Airpspeed Unreliable checklist is not only related to speed margins. Down low it is absolutely critical what you set because that's where the ground is. If I ignored the memory item in IMC at say 4000' AGL because I couldn't believe Boeing's numbers and set, say 2 degrees ANU and 80% N1 I'd be descending toward the terrain instead of getting away from it. No biggie at Singapore, for example, but maybe fatal at Hong Kong
I acknowledge that up high the choice of pitch attitude and thrust setting is more critical to stabilised flight because of the reduced margin between Vmin and Vmax, but the memory item is designed to place the aircraft in a safe state while you ferret around for the QRH or ECL and apply it. If you're cruising at FL350 or even climbing to it or descending from it in the flight levels, you're already safe. Touch nothing, get out the checklist and start solving the problem.
The B787 memory item is;
Autopilot Disconnect Switch................ PUSH
Both A/T Arm Switches.......................OFF
Flight Director Switches (both).............OFF
Set the Following Gear Up Pitch and Thrust:
Flaps Extended------------------ 10 degrees and 85% N1
Flaps Up------------------------- 4 degrees and 70% N1
Were I to detect Airspeed Unreliable in the cruise, I would call the memory item, action the first three and then verbalise to the FO that I won't touch the pitch and thrust as we're already in stable and level flight, well above terrain and ask him or her to access the Airspeed Unreliable checklist. To blindly apply the 4 degrees and 70% N1 at FL430 would certainly cause severe grief and this is where common sense steps in.
As for the B787 Airspeed Unreliable, another function of the pitch and thrust settings are to create a near-enough to stable state of flight. Once safely away from the ground (be it on departure having used 10/85 or in the cruise at FL430 having left the pitch and thrust unchanged), the crew can then use the flight state and checklist to identify the dodgy speed source.
Where Airbus has the Back Up Speed Scale (BUSS), the 787 has a function where speed calculated by GW, AoA, Config & GPS altitiude replaces indicated airspeed on the PFD: this is what Gas Path refers to & the point of it is to get the beast back on the ground while minimising pilot workload.
I'm really with Italia458 on this one. Boeing has designed this procedure because they know a lot more about it than we do and they want us to just do it, not to argue with it. Understanding the logic is great (get out your FCOM/QRH performance numbers and see what it gives you) but just keep it simple!
The logic behind the Airpspeed Unreliable checklist is not only related to speed margins. Down low it is absolutely critical what you set because that's where the ground is. If I ignored the memory item in IMC at say 4000' AGL because I couldn't believe Boeing's numbers and set, say 2 degrees ANU and 80% N1 I'd be descending toward the terrain instead of getting away from it. No biggie at Singapore, for example, but maybe fatal at Hong Kong
I acknowledge that up high the choice of pitch attitude and thrust setting is more critical to stabilised flight because of the reduced margin between Vmin and Vmax, but the memory item is designed to place the aircraft in a safe state while you ferret around for the QRH or ECL and apply it. If you're cruising at FL350 or even climbing to it or descending from it in the flight levels, you're already safe. Touch nothing, get out the checklist and start solving the problem.
The B787 memory item is;
Autopilot Disconnect Switch................ PUSH
Both A/T Arm Switches.......................OFF
Flight Director Switches (both).............OFF
Set the Following Gear Up Pitch and Thrust:
Flaps Extended------------------ 10 degrees and 85% N1
Flaps Up------------------------- 4 degrees and 70% N1
Were I to detect Airspeed Unreliable in the cruise, I would call the memory item, action the first three and then verbalise to the FO that I won't touch the pitch and thrust as we're already in stable and level flight, well above terrain and ask him or her to access the Airspeed Unreliable checklist. To blindly apply the 4 degrees and 70% N1 at FL430 would certainly cause severe grief and this is where common sense steps in.
As for the B787 Airspeed Unreliable, another function of the pitch and thrust settings are to create a near-enough to stable state of flight. Once safely away from the ground (be it on departure having used 10/85 or in the cruise at FL430 having left the pitch and thrust unchanged), the crew can then use the flight state and checklist to identify the dodgy speed source.
Where Airbus has the Back Up Speed Scale (BUSS), the 787 has a function where speed calculated by GW, AoA, Config & GPS altitiude replaces indicated airspeed on the PFD: this is what Gas Path refers to & the point of it is to get the beast back on the ground while minimising pilot workload.
I'm really with Italia458 on this one. Boeing has designed this procedure because they know a lot more about it than we do and they want us to just do it, not to argue with it. Understanding the logic is great (get out your FCOM/QRH performance numbers and see what it gives you) but just keep it simple!
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Memory Items from the 777 QRH
1 Autopilot disengage switch. . . . . . . . . . . . .Push
2 A/T ARM switches (both) . . . . . . . . . . . . . . . OFF
3 F/D switches (both) . . . . . . . . . . . . . . . . . . OFF
4 Set the following gear up
pitch attitude and thrust:
Flaps extended . . . . . 10 degrees and 85% N1
Flaps up . . . . . . . . . . . 4 degrees and 70% N1
as stated by Zlin77 these are immediate actions, pitch and power settings. The Unreliable Airspeed checklist directs you to the Performance Inflight section to refine these figures.
1 Autopilot disengage switch. . . . . . . . . . . . .Push
2 A/T ARM switches (both) . . . . . . . . . . . . . . . OFF
3 F/D switches (both) . . . . . . . . . . . . . . . . . . OFF
4 Set the following gear up
pitch attitude and thrust:
Flaps extended . . . . . 10 degrees and 85% N1
Flaps up . . . . . . . . . . . 4 degrees and 70% N1
as stated by Zlin77 these are immediate actions, pitch and power settings. The Unreliable Airspeed checklist directs you to the Performance Inflight section to refine these figures.
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The 787 Memory Items for Airspeed Unreliable
1 Check the pitch attitude and thrust for the phase of flight.
2 If the pitch attitude or thrust is not normal for the
phase of flight:
Autopilot disconnect switch . . . . . . . . . . .Push
Autothrottle disconnect switch . . . . . . . . .Push
F/D switches (both) . . . . . . . . . . . . . . . . OFF
Adjust the pitch attitude and thrust.
- - - - - - - - - - - - - - - - - - - - - - -
3 Captain’s AIR DATA/ATT
source selector. . . . . . . . . . . . . . . . . . . . . ALTN
The captain’s airspeed and altitude indications
change to AOA SPD and GPS ALT
1 Check the pitch attitude and thrust for the phase of flight.
2 If the pitch attitude or thrust is not normal for the
phase of flight:
Autopilot disconnect switch . . . . . . . . . . .Push
Autothrottle disconnect switch . . . . . . . . .Push
F/D switches (both) . . . . . . . . . . . . . . . . OFF
Adjust the pitch attitude and thrust.
- - - - - - - - - - - - - - - - - - - - - - -
3 Captain’s AIR DATA/ATT
source selector. . . . . . . . . . . . . . . . . . . . . ALTN
The captain’s airspeed and altitude indications
change to AOA SPD and GPS ALT