Brand new Boeing unreliable airspeed procedure

[Philemon]

Hello to all of you,

Recently, Boeing has changed its Unreliable airspeed procedure, asking now as first items to take 4° pitch and 70% N1 while the normal parameters for cruize are around 2°5 and 85%.

Does somebody know the reasons which have motivated this strange change, most of all after the AF447 accident ?

[vinayak]

We airbus pilots would to welcome you to the group :cool:

[Capn Bloggs]

asking now as first items to take 4° pitch and 70% N1 while the normal parameters for cruize are around 2°5 and 85%.

Asking for those is asking for trouble.

What aeroplane are you claiming this applies to?

[Lookleft]

The 777 didn't have an unreliable/airspeed checklist, the QRH only had a condition statement! Interesting that the 787 does have one.

[Wizofoz]

The 777 didn't have an unreliable/airspeed checklist

Eh? We've always had one! Just finished a Sim Phase in which we used it- a big take-away was that it didn't provide sufficient information for low level flight and approach- addressed with the current update.

HOWEVER- 4deg and 70% N1 as a memory item?

That DOES concern me.

It sounds lie a recipe for AF447 Mk2!!

[SMOC]

It's for use when it's subtle and unobserved and it finally dawns on you that "it's bad" and you are already exploring the edge of the envelope but your instruments are apparently supplying confusing "valid" data.

It's simply a ball park figure to give you time to get the QRH out and find the (performance inflight) real figures! It's not a permanent fix! The plane may climb/descend/accelerate/slow down but it won't get out of control in the time it takes to as said find the real figures and use them.

Read some unreliable airspeed etc accident reports most are very subtle and the aircraft is either nose high low thrust because they "think" they are overspeeding or nose low high thrust as the "think" they are stalling, either case when you apply the "memory items" that will slow/stop the situation escalating in the wrong direction.

If it's a simple immediate loss of data, don't change pitch and power and go straight to the inflight perf as it's obvious.

[SMOC]

It sounds lie a recipe for AF447 Mk2!!

Perhaps if they'd gone for 4deg and 70% things may have been different, seeing they spent most of the incident above 12deg.

[Capn Bloggs]

It's simply a ball park figure to give you time to get the QRH out and find the (performance inflight) real figures! It's not a permanent fix! The plane may climb/descend/accelerate/slow down but it won't get out if control in the time it takes to as said find the real figures and use them.

Come off the grass. Yes, it will climb (at over 1000ft/min) and it will slow down, a lot, in the time it takes to pull out the QRH. And yes, I suspect it'll go very close to going out of control (an Upset, at least) if you try 4°/70% up high (as is indicated by the OP's "normal cruise"of 2.5°/85%).

That's why I asked for some more details.

[Intruder]

Let's see... If already at cruise, why not Autothrottles OFF, retain last N1 setting, Autopilot to Altitude Hold?

70% N1 isn't going to keep a 747 at a reasonable airspeed at any reasonable cruise altitude, so it's a worthless "memory item"...

[nitpicker330]

Autopilot will most likely drop out. It will on the Airbus as the controls laws revert to Alternate. Manual flight it is until you exit the area and the probes clear. In the last few events it lasted only a couple of minutes.

[SMOC]

Clearly in the cruise, pitch and power are set and not changing and common sence would dictate not changing anything (ie maintain pitch and power).

It is for an unrecognised air data malfunction where the aircraft is now probably no longer at the correct pitch or power, cruise is probably the easiest one to spot it'll be the climb or descent where the A/P or F/D has gotten the aircraft in an excessively high or low nose attitude for the phase of flight chasing an unreliable speed for example.

757 crash "349kts" 15deg nose up, max thrust, and then reduced thrust to idle and pitched up to 18deg, by the A/P. It stalled.

727 crash 405kts climbing 6,500fpm FL230 Capt "no pull her back let her climb" stall warning / overspeed warning F/O there's Mach buffet, both agreed pull up, aircraft stalled descended 24,800' in 83 sec.

after a pilot's startled reflex reaction to an overspeed alarm sent an Air France Airbus A340-300 into a rapid climb, unnoticed by the crew.

[Lookleft]

Wizofoz- It does now but there was a time when the 777 did not have an Unreliable checklist:

B777 checklists
The aircraft manufacturer provided checklists for UNRELIABLE AIRSPEED in
the quick reference handbooks (QRH) of its other aircraft types. Those procedures contained references to various indications that were available to the flight crew as evidence of unreliable airspeed. Examples of those indications included:
– speed or altitude information not consistent with pitch attitude and thrust setting
– airspeed/Mach failure flags
– blank or fluctuating airspeed displays
– variation between pilot in command and copilot airspeed displays
–10– – amber line through one or more primary flight display or Attitude Direction Indicator flight mode annunciations
– overspeed indications
– simultaneous overspeed and stall warnings.
The aircraft ADIRU was designed with system redundancy to prevent those
malfunctions from occurring, so no checklist such as UNRELIABLE AIRSPEED was provided for B777 flight crews. With only one erroneous input, the system was designed to automatically stop accepting that input and divert to another input source for information. That event would not require any action by the flight crew, and was intended to minimise the number of checklist items that a crew would need to action. With multiple erroneous sources of information or internal failures in the ADIRU, the EICAS message NAV AIR DATA SYS would be displayed. That
would direct the crew to the appropriate checklist and the unreliable airspeed table.
The nature of the accelerometer failure in this occurrence meant that the NAV AIR DATA SYS message was not displayed on the EICAS during the occurrence.
The B777 QRH Section 10 Flight Instruments18, displayed non-normal items. The checklists within the section related to messages displayed on the EICAS, and only consisted of condition statements. Those statements briefly described the condition which resulted in the respective EICAS messages, and did not contain procedural steps for the flight crew to action.
The AIRSPEED LOW status message, which was displayed on the EICAS at the start of the occurrence, was referred to in Section 15, Warning Systems, of the QRH, but required no crew response or action, as it was a condition statement.
The QRH preamble on non-normal checklist operation stated:
While every attempt is made to provide needed non-normal checklists, it is
not possible to develop checklists for all conceivable situations, especially
those involving multiple failures. In some unrelated multiple failure
situations, the flight crew may combine elements of more than one checklist or exercise judgement to determine the safest course of action. The captain must assess the situation and use good judgement to determine the safest course of action.
The only non-normal checklist available to the crew was the UPSET RECOVERY procedure which was specified in the non-normal manoeuvres section of the QRH.

This was from the ATSB report into the MAS 777 upset: 200503722.

So my statement is correct, the 777 didn't have an Unreliable Airspeed checklist, it does now.

[parabellum]

In the back of the Vol 3 of every Boeing I have flown there was a complete page of numbers for flight with unreliable airspeed, most of us would have had it copied, laminated and secured to our clip boards for quick and easy reference.

[Wizofoz]

So my statement is correct, the 777 didn't have an Unreliable Airspeed checklist, it does now..

Well, your statement also said "Interesting that the 787 does" which made it seem as if you thought the 777 STILL didn't.

But you're quite right, and instead of "Always" I should have said "For quite some time".

[sleeve of wizard]

The Airspeed Unreliable checklist is a new and improved Airspeed Unreliable checklist.
This check-list has been revised to account for recent accidents. There are pitch and thrust memory items for flaps extended and flaps up configuration. These values may not seem ideal for the B777 but they are identical for all Boeing models.

[Jwscud]

There are no attitude or thrust targets in the NG QRH (very recently revised too). Simply "adjust attitude and thrust. Maintain airplane control" in the memory items and pitch/power tables.

[PPRuNeUser0190]

There is in the NG and its the same values. As said by sleeve of wizard they are identical for all Boeing models.

The numbers are a bit odd because of mixed fleet flying, but you'll won't crash. I'll try to find the Boeing wording.


PS: not agreeing with the new checklist, if you fly the thing you should know approx pitch & trhust settings.

[PPRuNeUser0190]

The following is some information, not all, from the Boeing symposium (can't find the document online). It talks about meetings between different manufacturers and how they will design their new unreliable airspeed checklists:

"...Procedures need to include memory items for initial pitch attitude and thrust setting:
• Settings need to maintain the airplane within the flight envelope until the checklist can be accessed
• Settings are valid at all weights and all altitudes
• Provide settings for Flaps Up and Flaps Extended
• Settings for climb with flaps are valid for all takeoff flap settings
• Settings should be standardized across all models as much as possible
• Do not change configuration while stabilizing the airplane with memorized settings
• If in a descent, stop the descent to accomplish the checklist...

....All models, all engine combinations, both heavy weight and light weight, high, medium and low altitudes, climb with all takeoff flap settings and flaps up cruise were analyzed. Best fit across all models was chosen to simplify the memory items....."

They then show a table of all Boeing models: the pitch is the same on all models, thrust varies:
Flaps up: 4° pitch, N1 between 75 and 90 %
Flaps extended: 10° pitch, N1 between 70 and 80 %

[FullWings]

Flaps extended: 10° pitch, N1 between 70 and 80 %
I wouldn't have thought that would be helpful in the landing config, given the normal pitch attitude is 0-1° and 60-70% N1 on the 777 and that's on a descending 3° glidepath. I haven't tried it out to see what happens but from inspection you'd get rather slow fairly quickly.

This seems to be taking "one size fits all" to extremes. Like rvblyky7 says, better to know a few more likely pitch/power settings or use what was working before the airspeed became unreliable.

[latetonite]

Before issuing this new procedure, Boeing, their pilots, and their lawyers probably thought about this seriously.

[FullWings]

You'd have hoped so. The recent battery fiasco on the 787 doesn't give much encouragement to the principle, however...

[zlin77]

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...

[BARKINGMAD]

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?!?! :suspect:

[mustafagander]

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.

[framer]

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.

[Jwscud]

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.

[Tee Emm]

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?

[Jwscud]

I'm afraid these are NG numbers, but:

FCOM & QRH Rev 23 25/4/13 (but only just now issued to us - go figure)

FCTM Rev 12 30/6/13

[latetonite]

I am amazed nowadays so called pilots want to learn, or buy, their knowledge from a FCTM.

[framer]

What do you mean latetonite?

[kwstas]

Hi,
latest FCOM QRH revisions are No33 December 2013 and for FCTM is rev12 June 2013.

[Becalmed]

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....... :}

[Capn Bloggs]

This seems to be one of those problems.
No, we're just querying the numbers, which obviously wouldn't work up high. Be nice if the thread starter would come back and give us all the information and not just 4/70.

the 787-8 GE is "Flaps Extended - 10 degrees, 85% N1. Flaps Retracted - 4 degrees, 70% N1".
At what altitude??

PS: Got your username under control there? ;)

[Becalmed]

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! :D

[italia458]

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. :ok:

[gas path]

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.

[Capn Bloggs]

Anything above that is arguably too high to start panicking anyway so touch nothing and refer to the QRH or ECL.
That's the point; down low it doesn't matter much what you set, with a large margin between Vmin and Vmax.

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...

The 787 can calculate airspeed from gross weight, flap and slat position, AofA and GPS altitude.
What airspeed? It's unreliable. :cool:

[Becalmed]

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!

[sleeve of wizard]

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.

[sleeve of wizard]

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

[Becalmed]

Hi Sleeve,
See my post above for the 787 memory item. Updated on the 3rd of April and now identical to the 777's.

[sleeve of wizard]

Thanks Becalmed,

expecting an update to the QRH imminently.

[BARKINGMAD]

Bearing in mind the accidents/incidents where the discovered (inadvertent) setting of the stab trim caused handling difficulties, surely this item should be included in any revised memory items or recall actions or whatever is this weeks buzzphrase???

I await the incoming, tin hat is on............... :confused:

[BARKINGMAD]

Yet another conversation stopper...........

Is there ANYBODYout there, from the professional pilot community, who agrees or disagrees with my suggestion?

Otherwise I may take the lack of discussion as silent assent, hardly a valid conclusion. :)