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yanrair
24th May 2019, 23:36
There have been a few comments about the usefulness or otherwise of GPS ground speed to safely fly when Unreliable airspeed, speed disagree and stick shakers rattling , at the same time as crazy high (or low) IAS indications are present. I.e. to resolve apparent chaos. AF447 and ET /LIONAIR are but three examples.

i contend that not only is G/S useful- it is the solution in most cases.

Let the conversation begin!
For start, I hope nobody disagrees that you can fly a perfect circuit using GPS only with ALL pressure instruments including IAS and altimeters not working. ?
Happy flying
Y

FlyingStone
24th May 2019, 23:58
Personally, I'd stick with the approved procedures for unreliable airspeed.

Your GS is 500kts. Are you safe? Could be TAS of either 650 or 350 with a 150kt wind. Neither of which will keep you flying for long at cruising FL.

Slatye
25th May 2019, 01:05
For start, I hope nobody disagrees that you can fly a perfect circuit using GPS only with ALL pressure instruments including IAS and altimeters not working. ?I'm not sure how you define "perfect", but for me it would include following the manufacturer's recommendations on airspeed - especially during takeoff and landing. Say you're in a C172 or PA28 with a 20kt headwind straight down the runway. If you just assume that airspeed = ground speed, then you're going to be taking-off 20kts faster (airspeed) than recommended - except that you won't be able to because the plane will insist on flying before that point. Then you turn downwind, and instead of the normal 80kts-ish downwind you're doing more like 60kts - which is not a stall, but is not much fun either. More challenging is landing; if you come in at 20kts above recommended approach speed, it's going to happily fly straight off the other end of the runway. That is, if you haven't already torn the flaps off and crashed by lowering full flap at 20kts above the maximum flap speed...

Of course, if you know your power settings then you can fly a perfectly acceptable circuit without any air or ground speed indication, and in either of those planes you can feel your airspeed just in the control response. Or if you have accurate wind readings and a bit of time to do the maths then you can convert ground speed into airspeed. However, assuming that the pilot knows the power settings, can feel the response, or has accurate wind readings and spare time may be a mistake.

stilton
25th May 2019, 01:18
Display of AOA is the best possible back up

Pilot DAR
25th May 2019, 01:49
Well, I've had my airplane flying 11 MPH backward, according the GPS groundspeed (It was a windy day), so with that in mind, I'll continue to use the airpseed indicator for airspeed information.

I do remember test flying a Tiger Moth following maintenance. It had three airspeed indicators, one in each cockpit, and a vane device on the wing strut. They all differed by about 10 MPH to each other, so I ignored them all, and just flew by feel, it was fine. In hindsight, I think the vane on the wing seemed the most accurate.

I really like the GPS for pointing me home, and telling me when I should expect to be there.

Capn Bloggs
25th May 2019, 01:59
Your GS is 500kts. Are you safe? Could be TAS of either 650 or 350 with a 150kt wind. Neither of which will keep you flying for long at cruising FL.
Hang on. Nobody is suggesting you suddenly find yourself plopped into a scenario with now idea how you got there or what the current conditions were and now had use the GPS.

You will obviously be happily flying along, knowing you are doing the right speed, then the pressure instruments go awry. The GPS GS is a great indicator in that case to keep you flying until you descend or otherwise sort out the problem.

The other scenario is after takeoff. You are starting from a relatively accurate known point: get it cleaned up and maintain 250 GPS GS, allow for the low level wind if you like. Safe as houses.

GPS GS is a fantastic aid if you have no IAS. You could even use your phone GPS speed.

Display of AOA is the best possible back up
In my aeroplane, the FPA is not reliable during a UAS event. I assume that AOA (unless it was just a raw readout from the vane) would also be dodgy.

ShyTorque
25th May 2019, 06:47
What's wrong with the tried and tested method of: "The correct attitude + correct power setting = correct speed?"

Having said that, at very low speeds landing away from an airfield (helicopter) I monitor the GPS groundspeed against the IAS to determine/confirm into wind or downwind on the approach.

Capn Bloggs
25th May 2019, 06:57
What's wrong with the tried and tested method of: "The correct attitude + correct power setting = correct speed?"
In your 737 at 40t or your 737 at 60t, if you set your UAS parameters at slow speed or high speed the speed outcome will be completely different.

FlyingStone
25th May 2019, 07:21
In your 737 at 40t or your 737 at 60t, if you set your UAS parameters at slow speed or high speed the speed outcome will be completely different.

And yet, it's safe, which is what matters in the end, not how accurately you can fly the speed you can't even see or whether you will climb or descent.

This is Boeing's take on this:

The memorized pitch and thrust setting for the current configuration (flaps
extended/flaps up) should be applied immediately with the following
considerations:
• The flaps extended pitch and thrust settings will result in a climb.
• The flaps up pitch and thrust settings will result in a slight climb at light
weights and low altitudes, and a slight descent at heavy weights and
high altitudes.
• At light weight and low altitude, the true airspeed will be higher than
normal, but within the flight envelope. At heavy weight and high
altitude, the same settings will result in airspeed lower than normal
cruise but within the flight envelope.
• The goal of these pitch and thrust settings is to maintain the airplane
safely within the flight envelope, not to maintain a specific climb or
level flight.
• The current flap position should be maintained until the memory pitch
and thrust settings have been set and the airplane stabilized. If further
flap extension/flap retraction is required refer to PI-QRH Airspeed
Unreliable table.

In my aeroplane, the FPA is not reliable during a UAS event. I assume that AOA (unless it was just a raw readout from the vane) would also be dodgy.

If installed, AOA readout normally is directly from the vane.

ShyTorque
25th May 2019, 07:29
In your 737 at 40t or your 737 at 60t, if you set your UAS parameters at slow speed or high speed the speed outcome will be completely different.

But aren't pilots paid to know the difference?

Capn Bloggs
25th May 2019, 07:41
Let me guess, child of the magenta line?
Let me guess, a luddite that has never actually tried a full-blown "I have no idea what my speed is" approach?

You lot should try to fly an approach in a jet based solely using the speed/power/attitude tables. Then fly it using the GPS speed and the wind from the tower. Chalk and Cheese.

And yet, it's safe, which is what matters in the end, not how accurately you can fly the speed you can't even see or whether you will climb or descent.
Not IMO. Those numbers and procedures are obviously designed for the heat of the moment to prevent you from stalling. A light jet at low level will still accelerate quickly at the recommended UAS parameters and could well end up like the Ethiopians. What's your power setting for 250KIAS at low level?

But aren't pilots paid to know the difference?
Are you a 737 pilot? Do you know the difference?

Icarus2001
25th May 2019, 08:38
https://support.garmin.com/en-AU/?faq=QPc5x3ZFUv1QyoxITW2vZ6

Flying a circuit on GPS altitude bears no resemblance to "altitude".

Capn Bloggs
25th May 2019, 08:41
What next? Engine fire ... go look for a big rain cloud just in case the fire extinguishers don’t work when they are initiated?
Whatever.

I'll use the GPS down final, you use your tables.

wiggy
25th May 2019, 09:03
My two pence worth if, as I understand it, there's an argument here about setting the gross pitch power Boeing figures vs. "simply" setting well remembered pitch power immediately you recognise an unknown airspeed situation..

As I read it (from our FCTM and other documentation) Boeing's logic behind not wanting ace pilots setting their committed to memory pitch and power figures for, e.g. for 250 knots 'cos they think they are at 250 knots and S&L is because by the time they recognise the situation they might not be at 250 knots and they might not be in level flight....so that's why they came up with the "it's safe" figures

Of course after the trouble shooting is done we usually arrive by way of a checklist to the weight/pitch/ power etc tables and then fly the machine that way.... so eventually you get to use both techniques (and so honour is satisfied, magenta line, old school or both).

F-16GUY
25th May 2019, 09:28
Hang on. Nobody is suggesting you suddenly find yourself plopped into a scenario with now idea how you got there or what the current conditions were and now had use the GPS.

Well, I got the impression that the crew of AF447 did get plopped into their scenario without any idea of how they got there. Trucking along for 10 hours straight, do you constantly keep track of your GND speed? It can change with values that exceed your A/C limits or stall speed, over a very short period of time i you are flying close to the coffin corner.


In my aeroplane, the FPA is not reliable during a UAS event.


Thats because the relation between FPA (INU/INS), Pitch and AOA is only perfectly constant and reliable in a no wind environment, flying in a straight line (1g). However, the FPA is a very reliable means of showing level flight regardless of the status of the AS indicators.


I assume that AOA (unless it was just a raw readout from the vane) would also be dodgy.


AOA is raw readout in either units or degrees. It is only dodgy if the vane is broken like on the MAX. AOA is most useful for aircraft where the total mass can vary a lot during flight, since it will always show you how far you are from stalling. Aircraft with AOA indicators normally have a fixed AOA value to be flown during approach regardless of their weight, thereby changing the status of the AS indicator to a B/U instrument only (during approach).

GPS is nice to point you home, give military pilots great weapon precision and such, but my suggestion is always to be able to fly your aircraft via the control and performance concept, as its the only proven concept that will get you safely on the ground. But there is a catch. It requires propper skills and sufficient training, a thing that magenta pilots probably don't have/get.

Vilters
25th May 2019, 10:03
While AOA is one of the best alternatives, remember that the latest crashes are due to failing AOA sensors triggering the events that end up flying the aircraft into the ground.

The very best alternative is to equip all aircraft with a crazy stupid alternative that is completely disconnected from the aircraft like a Dynon D3 pocket panel and revert back to basic flying skills..

FlyingStone
25th May 2019, 11:11
Not IMO. Those numbers and procedures are obviously designed for the heat of the moment to prevent you from stalling. A light jet at low level will still accelerate quickly at the recommended UAS parameters and could well end up like the Ethiopians. What's your power setting for 250KIAS at low level?

A 737 will go to Vmo at 10deg pitch and 80% N1 with flaps extended? Or 4 deg pitch and 75% N1 in clean configuration? Even at OEW and a bit of fuel to run the engines, I very much doubt it.

Why do you want to fly exactly at 250 KIAS? It is safe, for sure, but so are UAS pitch/power settings.

I would be very cautios when operating the aircraft outside of manufacturer's recommendations and procedures, especially when it directly contradicts them. A lot of work in the aviation industry went into developing robust UAS procedures post AF447, and they are much better now that they used to be. And despite all the media propaganda, I still believe Boeing engineers and test pilots have more (abnormal) aircraft/sim time and know more about UAS than many of us together.

Boeing FCTM says (my bold):
Memory items for target pitch and thrust must be accomplished as soon as it is suspected that airspeed indications are incorrect.

Good luck explaining to a lawyer why your pitch/thrust settings were better than manufacturer approved procedure, if things end up sideways.

oggers
25th May 2019, 11:23
As I read it (from our FCTM and other documentation) Boeing's logic behind not wanting ace pilots setting their committed to memory pitch and power figures for, e.g. for 250 knots 'cos they think they are at 250 knots and S&L is because by the time they recognise the situation they might not be at 250 knots and they might not be in level flight....so that's why they came up with the "it's safe" figures

Wiggy is correct plus they also state "at any and all weight/altitude combinations, the aircraft will accelerate from low speeds, and slow from a high speeds.... At light weight and low altitude, the true airspeed will be higher than normal, but within the flight envelope ".

Busdriver01
25th May 2019, 11:25
Call me old fashioned (I could easily be defined as a child of the magenta, in fact) but there’s a reason why the manufacturer put in the QRH a procedure for UAS and make it a memory item.

Setting a sensible pitch / power setting, and then following the QRH procedure for trouble shooting has to be the safest option.

Capn Bloggs
25th May 2019, 11:51
Wiggy, I agree.

Trucking along for 10 hours straight, do you constantly keep track of your GND speed?
No, what's the point? When you go UAS, then note your GPS GS. Maintain it until you work out what's going on. If you pull up to 4° and pull the power back to 75% (Flying Stone/737 UAS?) at FL370, you'd better watch that GPS GS closely because it'll be reducing!

At light weight and low altitude, the true airspeed will be higher than normal, but within the flight envelope
Precisely, and where the Ethiopians found themselves immediately prior to the final dive: at Vmo. I wonder what the GPS GS was then...

In my aeroplane, the FPA is not reliable during a UAS event.
Thats because the relation between FPA (INU/INS), Pitch and AOA is only perfectly constant and reliable in a no wind environment, flying in a straight line (1g). However, the FPA is a very reliable means of showing level flight regardless of the status of the AS indicators.
Just telling you what my FCOM says.

Why do you want to fly exactly at 250 KIAS? It is safe, for sure, but so are UAS pitch/power settings.
I didn't say anything about "exactly" 250KIAS. 230-270 GPS GS who cares? At least it's not Vmo with full nose down MACS trim while maintaining the UAS "it's safe" memory numbers while your PM comes up with some numbers from the back of the QRH...

Setting a sensible pitch / power setting, and then following the QRH procedure for trouble shooting has to be the safest option.
I agree. My point is that GPS GS is an invaluable aid while doing that, especially down low on approach or after TO when wind effect is low/known.

FlyingStone
25th May 2019, 12:08
No, what's the point? When you go UAS, then note your GPS GS. Maintain it until you work out what's going on. If you pull up to 4° and pull the power back to 75% (Flying Stone/737 UAS?) at FL370, you'd better watch that GPS GS closely because it'll be reducing!

Sure it will be decresing. But the aircraft will start descending at a safe speed/AoA to keep the wing flying. As you are at FL370, no problem with terrain clearance, and the ATC will get the other traffic out of your way. Plenty of time to have a look at the QRH, which is not that difficult to find anyway, as it's always the first thing under the Performance Inflight tab.

The flaps up pitch and thrust settings will result in a slight climb at light
weights and low altitudes, and a slight descent at heavy weights and
high altitudes.
• At light weight and low altitude, the true airspeed will be higher than
normal, but within the flight envelope. At heavy weight and high
altitude, the same settings will result in airspeed lower than normal
cruise but within the flight envelope.


At least it's not Vmo with full nose down MACS trim while maintaining the UAS "it's safe" memory numbers while your PM comes up with some numbers from the back of the QRH...

Now, to be fair, the ET302 did not apply UAS memory items (not suggesting they did a mistake, as it was a tremendously difficult situation and remains to be investigated). MCAS activated with flaps up, so should they have elected to perform UAS memory items, the pitch/thrust would be 4deg pitch.75% N1.

During takeoff roll, the engines stabilized at about 94% N1, which matched the N1 Reference recorded on the DFDR. From this point for most of the flight, the N1 Reference remained about 94% and the throttles did not move.

Last time I checked there is a significant thrust difference between 75% N1 and 94% N1.

Next time you're in the sim, ask the instructor for couple of UAS scenarios at various weights/altitudes and you'll see Boeing's pitch/thrust settings tend to give decent results.

Pilot DAR
25th May 2019, 14:01
Posters, the discussion is okay (though let's keep working at being courteous), but this forum may not be the best place for it. Would someone like to suggest the best forum for it, and I'll move it there?

Bergerie1
25th May 2019, 15:43
Pilot DAR, Tech Log?

YYZjim
25th May 2019, 16:00
1. Fly in any direction for five minutes
2. Fly the reverse course for five minutes
3. Divide displacement over ground (from GPS device) by ten minutes
4. Result is wind velocity

YYZjim

oggers
25th May 2019, 16:27
1. Fly in any direction for five minutes
2. Fly the reverse course for five minutes
3. Divide displacement over ground (from GPS device) by ten minutes
4. Result is wind velocity

YYZjim

........hmm. Might draw some comments with that one.

hans brinker
25th May 2019, 16:37
Well, I got the impression that the crew of AF447 did get plopped into their scenario without any idea of how they got there. Trucking along for 10 hours straight, do you constantly keep track of your GND speed? It can change with values that exceed your A/C limits or stall speed, over a very short period of time i you are flying close to the coffin corner.



Thats because the relation between FPA (INU/INS), Pitch and AOA is only perfectly constant and reliable in a no wind environment, flying in a straight line (1g). However, the FPA is a very reliable means of showing level flight regardless of the status of the AS indicators.



AOA is raw readout in either units or degrees. It is only dodgy if the vane is broken like on the MAX. AOA is most useful for aircraft where the total mass can vary a lot during flight, since it will always show you how far you are from stalling. Aircraft with AOA indicators normally have a fixed AOA value to be flown during approach regardless of their weight, thereby changing the status of the AS indicator to a B/U instrument only (during approach).

GPS is nice to point you home, give military pilots great weapon precision and such, but my suggestion is always to be able to fly your aircraft via the control and performance concept, as its the only proven concept that will get you safely on the ground. But there is a catch. It requires propper skills and sufficient training, a thing that magenta pilots probably don't have/get.

Agree, but I do think if the pilots on AF447 had looked at their groundspeed (I think it went down to 107 kts towards the end) it might have rung a bell?

ShyTorque
25th May 2019, 17:29
Are you a 737 pilot? Do you know the difference?

No, I'm not a 737 pilot. The subject title doesn't say the discussion is exclusively about the B737.

But I certainly do know the difference between IAS and G/S because wind velocity awareness is critical to carrying out my present job safely.
I was taught from square one to learn power/attitude settings that give a safe baseline to work from when flying jet powered aircraft and for all other types. For a couple of decades I was responsible for teaching others to do the same. It appears from some accident reports that more recent training might unfortunately not be so comprehensive. :(

RAD_ALT_ALIVE
25th May 2019, 19:56
Other than encouraging debate, the assertion that GS (GPS-derived or otherwise) is better than AoA (essentially what the manufacturers are directing the pilots to concentrate on with their ‘pitch/power’ tables) is so flawed as to be laughable.

Using Airbus FBW procedures as an example, the onset of unreliable speed during steady-state cruise requires no immediate action from the pilots. Most likely, thrust will be locked as the FMS detects the anomaly, and the AP will disconnect. This is the aircraft ‘telling’ the pilots that it can’t figure out what to do, but that the last thing that it WAS doing was working, so now it’s over to the pilots. Hopefully then, neither pilot will do ANYTHING; the aircraft FBW will keep the aircraft flying at 1G, at a power that was safe.

Then it’s either a matter of calmly and methodically checking the QRH for the suggested pitch and power (if cruising at high levels - Airbus’ take being that at high levels, these events are short term in duration), or - if at lower levels - following the procedure to activate the BUSS (Back Up Speed Scale), where the PFD changes it’s presentation to a very easily interpreted AoA scale. This presentation allows very intuitive operation in all regimes, and during configuration for approach and landing.

There is no mention anywhere, in any of our manuals, about accessing the GPS data to determine GS. There is no mention about asking ATC what our GS is. No mention of GS, full stop!

Jet performance is so great, that their climb and descent capabilities (ie resulting in significant change in TAS and wind velocity over relatively short periods of time) as well as their high cruising speeds at high altitudes (with it’s possible significant change in wind velocity over short to medium distances) make any use of GS in UAS events unwise, ineffective and downright dangerous.

For those who might think Bloggs’ assertion is a good idea, I would instead encourage that they just follow the specific manufacturer’s procedures.

Junkflyer
25th May 2019, 20:04
GS is a good tool in the box.
Can be used for reference, but in no way should it take precedence over pitch/power.

yanrair
25th May 2019, 23:32
Let me guess, child of the magenta line?

When you learnt to fly were you taught somewhere around lesson 1 that in each aircraft configuration the airspeed achieved will be as a result of the power + attitude? Was it not demonstrated too?

That’s why the manufactures provide “unreliable airspeed” procedures based upon configuration/weight/altitude/attitude and power setting required.
OK. Having started this thread- it’s an interesting one, let me try a reply. First we are talking big planes here and no visual reference. And of course at the time of IAS failure you know your groundspeed. As stated earlier this doesn’t apply to a situation akin to a blindfold pilot , at an unknown altitude, airspeed or wind suddenly being unblindfolded, with no instruments. He is in stable flight prior to the failure. He knows the current wind and GS and also has accurate winds for all altitude on the flight plan. Within 5
So.........,,,
1. Not magenta line guy ! Actually navigated by Astro sextant on passenger jets until 1978! And have flown 737 all variants, 757. 767. l1011. 747-400.
2. Pitch And power were the only way to fly UAS prior to G/S readout. Still the primary source of info. But GPS refines that info and guarantees that you are in the right safe zone
3 captain bloggs above has it right. We are seeking a safe flight and approach which keeps you well away from
stall or excess speed. Guaranteed
4. For years say 1985-1995 many types especially. Tristar used GS on every approach in heavy winds to refine IAS. It then fell out if common use but I’ve seen it used up to recently.
Over, but not out...,,,
its a fascinating thing that there is one readout on the flight deck- actually three- GS that don’t fail and ensure safe flight but very few believe it. One major airline teaches it- maybe others too.
Y

yanrair
25th May 2019, 23:43
Simple example if AF447 had maintained existing pitch at 3 deg. NU, 70%N1 power (approx) and GS 460 kts (whatever it was at the time of failure) nothing would have happened. Safe flight for the foreseeable future. If GS fell by 30 kts say, then apply thrust back to 460 GS and readjust power to 72% and so on.
If anyone thinks this wouldn’t work perfectly please say why.
Cheers and thanks for keeping this thread calm.
Y

itsnotthatbloodyhard
26th May 2019, 02:48
Simple example if AF447 had maintained existing pitch at 3 deg. NU, 70%N1 power (approx) and GS 460 kts (whatever it was at the time of failure) nothing would have happened. Safe flight for the foreseeable future. If GS fell by 30 kts say, then apply thrust back to 460 GS and readjust power to 72% and so on.
If anyone thinks this wouldn’t work perfectly please say why.


Because the thrust required would’ve been more like 95% N1 than 70%, and because any changes in the wind would have you chasing the GS in a way that could be quite detrimental. Still better than what happened, though!

ACMS
26th May 2019, 02:53
A330-300 normal cruise is 2.5 degrees pitch and 78% N1

GPS Altitude and GS is very handy BUT use carefully the GS....

Pilot DAR
26th May 2019, 03:24
Okay Posters,

As suggested, here in Tech Log now, continue along as you wish, while new rumours and new news populates the R&N forum...

Pilot DAR

2992
26th May 2019, 03:37
So, I have read this debate many times over the years. It always leads to a hot discussion then degrades to an argument. But I have learned a lot from them.

I am a firm believer of looking at all the available data (in the cockpit) to try and form a picture. There really should not be a one-size-fits-all approach to this. Saying that, luckily I (as pretty much everybody else here) have never been in this type of situation aside from the standard recurrent Sim sessions where we are thoroughly briefed on what is going to happen and how to get out of it in the Sim world. And I hope I never do.

My issues with the GPS speed thing, is two fold. First, pitch/power should always be first. In many of the transport and corporate aircraft I fly, there are no tables to memorize - a good pilot gains a feel of each type. I am not saying that I remember the exact power numbers that equal airspeed for the various aircraft I fly to maintain an altitude, but I guarantee I know what settings would keep me from stalling or pointing at the ground. Rarely do all the engine indication instruments fail, but I have had ADC (and AHRS) issues in a variety of types.

In the C172 pattern/circuit example: I would never fly it looking at the GPS, but I can and have flown/taught visual patterns/circuit without any instruments (covered up) or GPS. Pitch/power/feel of the butt. I have taught many a 15 hr student pilot to do so, but have flown with many 2500 hr pilots who cannot fly a visual approach without some sort of VNAV giving them a profile.

The second is the problem with the 3rd dimension. Image a situation where the IAS is decreasing (malfunction), so the pilot pushes down. As the aircraft’s path moves further into the vertical, the 2D GPS GS will decrease. Look at the curve of the hypothetical: strait nose down will theoretically give you zero GS (wind aside). So after maybe about 30’ nose down, as the IAS decreases (malfunction), the pilot pushes nose down and the GS keeps decreasing as the 2D flight path has less of the forward component. Of course the pilot should “sense” the noise and other clues to say he/she is speeding up - but that might be what is missing in this black/white discussion.

Again, I really hope I will never encounter a situation such as the AF folks. But I also hope that I would have the experience and wherewithal to not put the aircraft in a nose-dive towards the ground. But at a low-level - man - that would be a really hard situation to live through.....

Smythe
26th May 2019, 04:50
A330-300 normal cruise is 2.5 degrees pitch and 78% N1

Just curious..when you state 2.5 degrees, Is this the AoA of the fuselage or the wings?

On the A333. what is the AoA delta between the fuselage and the wings?

FlightDetent
26th May 2019, 05:08
? Are you asking about the angle of incidence between the wing chord and fuselage longitudinal axis?

itsnotthatbloodyhard
26th May 2019, 05:22
A330-300 normal cruise is 2.5 degrees pitch and 78% N1

Not in any A330 I’ve ever flown, unless your ‘normal cruise’ is down around F200. For F350, M0.8, ISA+10, 205t (as per AF447), the tables I’m looking at indicate about 95.5% N1. That’s for the CF6 - would the RB211 be that much different?

Capn Bloggs
26th May 2019, 05:59
Jet performance is so great, that their climb and descent capabilities (ie resulting in significant change in TAS and wind velocity over relatively short periods of time) as well as their high cruising speeds at high altitudes (with it’s possible significant change in wind velocity over short to medium distances) make any use of GS in UAS events unwise, ineffective and downright dangerous.
Let's not get carried away. I never said use GPS GS to the exclusion of everything else. Thanks for the lecture on TAS/Wind/Altitude. I didn't know that.

fdr
26th May 2019, 06:25
Whether you use GPS GS, TAS, FPA, ATT/PWR is essentially purely a technique to retain SA. Heck, you can use Sound power level, (did that for an accident investigation...) Whatever your preference, FCTM guidance, there are numerous sources of data that can be used.

B777's have lost everything at least twice in operations, and have got close to that a number of other occasions. The B744 has gone blank, for transferred faults, and for idiots in charge of the plane.

A B767 and a B757 (condor/Aeroperu) dumped themselves in an untidy heap, while all manner of data sources were available, including external to the aircraft. I have an attitude display on my iphone, ipads, and android phone, and all are better than that offered by any OEM airframer. My android phone gives accurate AH info for 48 hours, which is longer than my interest, but is certainly better than the 30 minutes that is certified by the OEM. If you are driving your shiny new A or B brand with 138 minutes, you already exceed your ISFD endurance by enough to be annoying, unless you have your string, glass, cat etc. At modest Mach, the current crop of nav charting on the ipad give enough info to fly level and nearly straight, slower is better, just like the early Garmin 3 pilot displays used to give a pseudo 6 pack.

AOA is great to have, and I fly donuts every day, did in the military and do on corporate jets. HUD was nice, but all sensors can have a bad day, and a loss of electrical power will leave the argument back to simple subjects, your GPS, AOA, EIS/ECAM are giving info that look rather poorly without ergs.

So, huff n' puff about how many angels can fit on the pin head, and then consider what you do when you cannot find the pin.. it all becomes moot.

Any comprehension of correlation of performance, attitude, and any associated data source increases the likelihood that you can recognise a problem in the first place, and history shows that the problem isn't actually doing it, it is recognising that you need to do it.

GPS (or other) ground speed is handy to have in mind at all times, it gives a nice idea of what sink rate to target on finals, it gives an idea of your wind component (think about stopping before going into rivers or oceans at the EOR.... like Mach number, it gives a nice idea of pitch changes needed to get a particular rate of climb or descent... or attitude adjustment to level off etc.

If it helps, use it. if not, don't.

The B777 AOA still generally gives a good backup to UAS cases, however TBC realised that there was an input from the ADC output that could give erroneous output. If you have an PFD/AI etc, and a VSI of any sort, (or an altimeter, GPS altitude... whatever, Cat, string, cup of soup in a glass...) then you can determine the difference between the effective flight path and the attitude, and thereafter, you don't need AOA at all, you have it from the AI. If that is accurate. The greater your comprehension of the data presented in your unique case, the higher likelihood that the outcome is a yawn not a headline making smoking hole in the ground. Due to some frustrating luck In the last 12 months, I have had over 2 dozen ADC failures, so pretty much take the position that understanding what is happening around you is paramount, not what the book demands. In the same period, at least 2 major hull losses have resulted from a single ADC failure, so some level of understanding is probably a good thing.

If a loss of an AI/PFD, ASI or ALT is worrisome, then the time in cruise looking at the relationships of the data/performance needs to be ramped up.

Cat/rope/cup, AOA, ATT/Pwr whatever it takes to float your boat.

Note: the only AOA probes I have had fail are two on the B737... and a stuck one on a B747. They do fail, but so does eveything else on occasion

vilas
26th May 2019, 06:54
AF447 should not be brought in because the crew was overwhelmed. They didn't see anything not even the pitch that resulted fro their actions forget the GPS GS. UAS procedure is based on a philosophy to manage the aircraft speed within a safe band, accuracy is not the purpose nor is it possible. It is similar in Boeing or Airbus. After having applied recommended procedure GPS GS may be referred for awareness but it won't be wise to fine tune anything. Airbus has come out with back up speed(different from B/U SS) obtained by applying lift equation to GW, AOA, CG. It's there in A350 and optionally available on other models. If fitted then it's as simple as AP/FD TCAS. You do nothing. Just Say thank you.

Outtahere
26th May 2019, 11:20
Not in any A330 I’ve ever flown, unless your ‘normal cruise’ is down around F200. For F350, M0.8, ISA+10, 205t (as per AF447), the tables I’m looking at indicate about 95.5% N1. That’s for the CF6 - would the RB211 be that much different?



ACMS quotes accurate numbers above for the RR Trent 700 powered A333 in cruise around F370.

scifi
26th May 2019, 11:59
It seems as if we are assuming we don't know the actual windspeed, when this can be found by asking the nearest ATC unit for their ground windspeed, then adding the correction of twice that and add 30 degrees to find the wind velocity above 1000 ft.
.

pineteam
26th May 2019, 12:17
Just have an idea of the pitch and power you need, it’s not rocket science. Plus on Airbus the thrust would be locked so you don’t even need to worry about it unless you are in a climb or descent.
A320: Above FL 300: 80% N1 pitch 2 degrees up
between Fl200 and Fl300 : 70% N1 & same pitch
Below Fl200 60%: N1 pitch 3 degrees up then 4 up below Fl100.
Just some rough value from what I saw during flights. With these I might climb or descent gently but I won’t stall nor overspeed and it gives me time to reach the QRH to do fine tunning.

FlightDetent
26th May 2019, 12:22
scifi, that's pushing too far, it is not a hot air baloon.

The best solution is to at first do nothing and check all the remaining parameters, to be used later as a reference and self-check over and over again.

This thread inspires me to include GS in that scan the next time, and it might had prevented a ckup I managed to create in the last session. Having said that, anything additional must be included carefully not to compromise the original underlying skill.

Pilot DAR
26th May 2019, 13:44
The best solution is to at first do nothing and check all the remaining parameters

I like that answer! I observe too often that in cruise flight something will appear to "happen" or change, and a pilot thinks that they need to apply their cat like reflexes to compensate for it. Sometimes it's better just to have already been aware, and then continue to be aware, perhaps with an added element to consider. As time passes, and other factors require a change, then maybe compensation, or a changed plan is going to be needed. Maybe, nothing (other than a written up snag) will be required.

Which reminds me of one of my learning events. I was first time left seat ferrying a Twin Otter with a very experiences mentor pilot friend. We were leaving Cairo southbound, and low altitude nav aids were few and far between. This particular Twin Otter did not have a DG at all, it had two slaved RMI's and the magnetic compass (which is not remarkably useful for flying a heading in a Twin Otter). We had noticed on previous legs that the RMI's would drop a flag an quit, seemingly randomly, so becoming useless for flying a heading. We agreed that whomever had a working RMI would fly (no auto pilot, hand flying the whole trip anyway). So, when a half hour into a 9 hour leg, my RMI dropped a flag, I wasn't really eager to surrender flying just yet, I was enjoying myself! My mentor friend was consumed with a marine "Sat Nav" device he had brought on the trip. This was before the days of GPS - the time before magenta lines, so it was charts and heading indicators, other than Bill's occasional fixes on his Sat Nav. He was happy watching the Sat Nav, and probably had little interest in flying anyway, so I kept flying... but how was I going to hold a heading? I could look across at his RMI, but that was not a really good long term solution. As it was a very clear day, I could fly by ground reference for a while, but in that part of the world, sand is sand, so there were not many features to pick on the horizon.

So I flew on, taking my time, and thinking. During this period, I found a solution. I considered it, verified it with occasional glances to Bill's RMI, and applied it. I flew a perfect track. Eventually, Bill noticed that my RMI had dropped a flag, he commented without alarm. He asked if I was okay continuing flying, and I said I was. Over the next number of hours, he used the Sat Nav to confirm that my track was right on, and eventually asked me how I was doing it. I told him I'd tell him later.

25 flying hours later, (all but the final leg of which I was offered left seat), and many more RMI failures, I had kept my technique to myself, and he seemed content to ride along, confirming my track, and perfecting his use of the Sat nav for sailing (which interested him more than flying a Twin Otter). We arrived in Maseru and delivered the plane to Air Lesotho. At dinner he finally said: "Okay, you gotta tell me how you were doing that, you were flying perfect tracks for hours with no practical heading indicator." I explained that while flying with the RMI card stopped, I noticed that the RMI slaving meter would show the failing attempts of the remote compass to slave the card. As long as the RMI failed on the heading I wanted to fly, and I kept the slaving meter centered, to plane followed the heading. He quietly smiled. I learned to determine if something was a problem, before doing something to solve it.

hans brinker
27th May 2019, 00:29
It seems as if we are assuming we don't know the actual windspeed, when this can be found by asking the nearest ATC unit for their ground windspeed, then adding the correction of twice that and add 30 degrees to find the wind velocity above 1000 ft.
.

Yeah, I'm sure they would have had an accurate ground wind reading for AF 447.


Never mind that I've seen wind speed over 150kts without hurricane warnings on the ground.


https://www.pprune.org/professional-pilot-training-includes-ground-studies-14/

ACMS
27th May 2019, 08:30
Yes I should have said A330-300 RR powered is 2.5 degrees and 78% N1
I don’t know anything about the P and W or GE 330’s

Smythe—-I’m quoting Pitch attitude on the ADI......not AOA or anything else.

DaveReidUK
27th May 2019, 10:21
Just curious..when you state 2.5 degrees, Is this the AoA of the fuselage or the wings?

On the A333. what is the AoA delta between the fuselage and the wings?

Wing root incidence on the A330 is, I believe, +4.5°.

Capn Bloggs
27th May 2019, 11:17
Using Airbus FBW procedures as an example,...

There is no mention anywhere, in any of our manuals, about accessing the GPS data to determine GS. There is no mention about asking ATC what our GS is. No mention of GS, full stop!

I would instead encourage that they just follow the specific manufacturer’s procedures.
Interestingly, today I was reading the report into an A320 Pitot Blockage (https://www.atsb.gov.au/publications/investigation_reports/2015/aair/ao-2015-107/) event, which included a stall warning on final approach. Page 64 and on (a copy of the Airbus FCOM Abnormal procedure for UAS) references using GPS altitude and speed:

"GPS Altitude...Display on MCDU"
"Refer to GPS Altitude..." to the extent that it can be used to maintain level flight.
"Crosscheck all speed indications..."
"Alternate sources may be used to evaluate the data (from the reliable ADR):
-GPS altitude
-GPS and IRS ground speeds, taking into account altitude and wind effects".

Full stop indeed.

sleeve of wizard
27th May 2019, 15:43
The airspeed unreliable memory items and checklist were developed by Boeing from recommendations / guidelines published by Flight Safety Foundation.
These guidelines included,
Procedures should provide information on altitude and power settings that enable crew to maintain the aircrafts flight parameters within normal limits during flight with unreliable airspeed events for all phases of flight.
Procedures should address the availability and use of independent alternate sources of airspeed information (e.g. GPS, inertial, angle of attack etc.)
Procedures should include memory items for critical immediate action steps

The recommendations also provided an Airspeed Unreliable Generic Template,
1. Disconnect Automation - Rationale: automation may be reacting to airspeed indications that may not be correct, so it must be disconnected
2. Stabilse the aircraft with the provided pitch attitude and thrust - Rationale: setting memorised pitch attitude and thrust settings stabilise the aircraft in climb or cruise as applicable. if in a descent, the aircraft should be levelled off and the cruise setting used.

There in ends the recommended memory items, reference items of the checklist then direct the amongst other items to set an applicable attitude and thrust. Boeing aircraft this information is found in the QRH PI section.

In summary
The initial pitch and power settings of the memory items on a Boeing aircraft are designed to keep the aircraft "safe" until such time as the accurate Pitch and Power setting s can be extracted from the QRH
PI section.

Regarding GPS ground speed, the elephant in the room is GPS jamming, it is becoming more and more prevalent in particular regions of the world so much so that IATA has recently issued an operator alert on the subject.

iceman50
27th May 2019, 16:17
Capn Bloggs
"GPS Altitude...Display on MCDU"
"Refer to GPS Altitude..." to the extent that it can be used to maintain level flight.
"Crosscheck all speed indications..."
"Alternate sources may be used to evaluate the data (from the reliable ADR):
-GPS altitude
-GPS and IRS ground speeds, taking into account altitude and wind effects".

Full stop indeed.
Why did you not quote the full Airbus Procedure as what you quoted would be after the stabilization of the aircraft. You can twist anything to make a point!

wiggy
28th May 2019, 11:46
Regarding GPS ground speed, the elephant in the room is GPS jamming, it is becoming more and more prevalent in particular regions of the world..

Good point, yes it is.

dook
28th May 2019, 18:47
Can GPS measure dynamic pressure ?

Did you say no ?

There's your answer then.

Pilot DAR
28th May 2019, 22:30
Can GPS measure dynamic pressure ?

Hold the touchscreen out the window into the airflow? Hmmm, a new app for phones, the touch screen is the pitot tube!

pineteam
29th May 2019, 04:57
Guys if it was a good idea to use GPS or IRS ground speed for unreliable airspeed it would already have been implemented in the unreliable airspeed procedure.
In my home base, it's common to have on final a tail wind of more than 20 kt around 2500 feet AGL and a headwind on landing... The wind speed and direction change dramatically.
GPS is a great tool, I used it as my primary nav instrument back in the days flying in the bush; But I would definitely not use it as a primary tool to recover from an unreliable airspeed.

yanrair
29th May 2019, 23:40
Wiggy, I agree.


No, what's the point? When you go UAS, then note your GPS GS. Maintain it until you work out what's going on. If you pull up to 4° and pull the power back to 75% (Flying Stone/737 UAS?) at FL370, you'd better watch that GPS GS closely because it'll be reducing!


Precisely, and where the Ethiopians found themselves immediately prior to the final dive: at Vmo. I wonder what the GPS GS was then...


Just telling you what my FCOM says.


I didn't say anything about "exactly" 250KIAS. 230-270 GPS GS who cares? At least it's not Vmo with full nose down MACS trim while maintaining the UAS "it's safe" memory numbers while your PM comes up with some numbers from the back of the QRH...


I agree. My point is that GPS GS is an invaluable aid while doing that, especially down low on approach or after TO when wind effect is low/known.
dear Captain Bloggs
i started this thread to see what proportion of readers realized that GS is not just useful, but makes UAS.an easy exercise.
You seem to be one of “ the few” believers!
Y

yanrair
29th May 2019, 23:47
Personally, I'd stick with the approved procedures for unreliable airspeed.

Your GS is 500kts. Are you safe? Could be TAS of either 650 or 350 with a 150kt wind. Neither of which will keep you flying for long at cruising FL.

but since you know your wind speed to within 5 knots this doesn’t happen. Your flight plan is accurate +/- 5 kts and even synoptic chart within say 15. And anyway you know the GS at time of failure and it ain’t going to change in the next ten minutes which is how long it too AF447;to lose all sense of speed ending up at less than 110 kts. If they had set pitch power or even left pitch power at existing settings and maintained GS 450 kts ,:it would have been time to ding for a cup of tea while considering further actions. Ok perhaps no tea.
Y

yanrair
30th May 2019, 00:03
Guys if it was a good idea to use GPS or IRS ground speed for unreliable airspeed it would already have been implemented in the unreliable airspeed procedure.
In my home base, it's common to have on final a tail wind of more than 20 kt around 2500 feet AGL and a headwind on landing... The wind speed and direction change dramatically.
GPS is a great tool, I used it as my primary nav instrument back in the days flying in the bush; But I would definitely not use it as a primary tool to recover from an unreliable airspeed.

Perfect.
2500 ft tailwind 20
airfiel wind headwind 20
So your landing GS will be 20 kts less than V Ref. Say VRef 100, then fly whole approach at 120 GS. Your IAS will be 140 at 2500 and 100 on landing. Just what you were looking for- no? A perfect touchdown speed. Not approx.
more commonly one has reducing headwind during final descent. Say 30 kts HW at 1000 ,and 5 kts at touchdown. VRef 100.
Fly whole approach at 105 kts. GS. You will land at EXACTLY 100 VRef!
this is precision flying- not guesswork. Clearly you use manufacturer Pitch/power tables too to give you a clue but then refine the outcome using GS.

yanrair
30th May 2019, 00:06
Good point, yes it is.
GPS has jammed very rarely and if it does every plane airborne is going to be in some difficulties.. but for the GPS To fail just as your failed instruments is unthinkable statistically
Y

yanrair
30th May 2019, 00:09
Capn Bloggs
Why did you not quote the full Airbus Procedure as what you quoted would be after the stabilization of the aircraft. You can twist anything to make a point!
No twist. Stabilize plane setting sensible pitch power for conditions. You are now safe. Then refer to GS to ENSURE that your previous setting have achieved a safe airspeed and keep it there.
y

yanrair
30th May 2019, 00:22
You are not going to get a gps jam just as your birds or ice or whatever it is disables your air data systems. Not going to happen.
Its a cinch
TAS INCREASES BY 50 kt per 10000. So if the following are at a safe speed at MSL you have all you need is this knowledge

MSL
250:kts IAS AND GS
FL 100. 250 kts IAS= 300 GS
FL200 250 IAS = 350:GS
etc etc
At FL350 250:kts IAS = 450 kts.

If you fly these GS in still Air you are safe. OK - then +/- the wind which is elementary maths.
You could fly a whole flight from takeoff to landing using this info and always have safe margins.

Capn Bloggs
30th May 2019, 04:13
Why did you not quote the full Airbus Procedure as what you quoted would be after the stabilization of the aircraft. You can twist anything to make a point!
Cool it, Ice. I never claimed you do that GPS stuff BEFORE the memory items. I merely pointed to evidence that suggests that RAD ALT ALIVE's assertion that GPS isn't mentioned in any manuals appears to be rubbish. Even more concerning is that they appear to be an Airbus driver.

In any case, any reader is quite welcome to click on the link I provided (I even gave the page number, for goodness sake) to see what I was getting at.

Anyway, fly any way you like. I (and YT! :ok:) will be calling Pineteam's tower for the 3000ft wind and cruising down final looking closely at the GPS speed. A "Reference Groundspeed Approach" I believe they used to call it! :}

pineteam
30th May 2019, 05:20
Perfect.
2500 ft tailwind 20
airfiel wind headwind 20
So your landing GS will be 20 kts less than V Ref. Say VRef 100, then fly whole approach at 120 GS. Your IAS will be 140 at 2500 and 100 on landing. Just what you were looking for- no? A perfect touchdown speed. Not approx.
more commonly one has reducing headwind during final descent. Say 30 kts HW at 1000 ,and 5 kts at touchdown. VRef 100.
Fly whole approach at 105 kts. GS. You will land at EXACTLY 100 VRef!
this is precision flying- not guesswork. Clearly you use manufacturer Pitch/power tables too to give you a clue but then refine the outcome using GS.

Hello Yanrair,

I did not say the wind was 20 kt headwind on ground lol. It usually goes from a strong tailwind around 2500 feet to a crosswind/ light headwind. Anyway I don't deny you should not use the GS as a tool. If you are 200kt GS on short final, something is wrong. But I think it's safer to keep it simple. Pitch and Thrust is all you need to fly safely to the ground. A quick look at the GPS can help but should not be relied on. If for some reasons I have Unreliable airspeed on final, I know with 4 degree pitch and 50% N1 with F3 and gears down on A320 I'm safe. No need to do maths in a critical phase of flight and that's how Airbus expect you to fly in that case according to the QRH. =)

Dominator2
30th May 2019, 08:40
I have watched this discussion with great interest. Most inputs have been from pilots who have never flown using AoA. I detect the odd Ex Military pilot who supports the use of AoA rather than the ridiculous suggestion of using GS as a substitute for IAS.

I have flown for nearly 40 years using AoA as a primary means to control my aircraft. Although IAS was used throughout, it was totally possible (and practised) to fly and land using AoA, power settings and attitude (aircraft not pilots)!

AoA should be displayed in ALL aircraft and its use and relevance taught from initial pilot training right through to a Line Check or Combat Ready.

oggers
30th May 2019, 11:05
Perfect.
2500 ft tailwind 20
airfiel wind headwind 20
So your landing GS will be 20 kts less than V Ref. Say VRef 100, then fly whole approach at 120 GS. Your IAS will be 140 at 2500 and 100 on landing. Just what you were looking for- no? A perfect touchdown speed. Not approx.

You are dangerously in error. You say you are flying 120 GS on the whole approach. There is a 20kt tailwind at the top and 20kt headwind at the bottom. That means your IAS will be 100KIAS at the top and 140 at the bottom. Great job shooting your own method in the foot with such a convincing demonstration of how easy it is to get wrong. Good news is you get to practice a stall recovery and a touch and go in one approach.

itsnotthatbloodyhard
30th May 2019, 13:56
Want a great example of an A330 with unreliable to no airspeed, and use of ground speed as a source of information?

Youtube ‘Malaysian unreliable airspeed’ ...a Malaysian A330 that departed YBBN with the pitot covers still on.

Except it was using AoA. From the ATSB report: “In accordance with published procedures, the flight crew turned off the three air data reference systems (ADRs) at 1343. This activated the aircraft’s backup speed scale (BUSS) (Figure 3), which provided a colour-coded speed scale derived from angle of attack” [my bold].

I’m with Dominator2 - give me AoA any day.

yanrair
30th May 2019, 23:41
Cool it, Ice. I never claimed you do that GPS stuff BEFORE the memory items. I merely pointed to evidence that suggests that RAD ALT ALIVE's assertion that GPS isn't mentioned in any manuals appears to be rubbish. Even more concerning is that they appear to be an Airbus driver.

In any case, any reader is quite welcome to click on the link I provided (I even gave the page number, for goodness sake) to see what I was getting at.

Anyway, fly any way you like. I (and YT! :ok:) will be calling Pineteam's tower for the 3000ft wind and cruising down final looking closely at the GPS speed. A "Reference Groundspeed Approach" I believe they used to call it! :}
On TristaR we used iT a lot in wind gradient conditions. Remember landing LHR 23 with surface wind 210/45 and 2000 ft wind 210/70. So we would lose 25;kts during approach. VRef+5 was 140. So flew whole approach at 115 kts GS. NEVER TOUCHED POWER ALL THECWAY DOWN DUE STABILITY OF APPROACH.
Y

yanrair
31st May 2019, 00:14
You are dangerously in error. You say you are flying 120 GS on the whole approach. There is a 20kt tailwind at the top and 20kt headwind at the bottom. That means your IAS will be 100KIAS at the top and 140 at the bottom. Great job shooting your own method in the foot with such a convincing demonstration of how easy it is to get wrong. Good news is you get to practice a stall recovery and a touch and go in one approach.

You are right buddy. It was late and i screwed up on simple math but actually there was no stall since IAS was safe in spite of incorrect math. But no matter. The principle is flawless despite my maths in the above being pre-primary level!
should have said fly approach at GS 80 = IAS 100
downwind maybe fly GS 140=IAS 120
point is it works.
Now someone mentioned pitch /power which is paramount as a starting point. Agreed 737 it’s 6pitch/60N1
But do need your weight too.
Amd on the approach your pitch power change due to headwinds. But you don’t know by how much do you !
GS solves this
y

yanrair
31st May 2019, 00:17
It seems as if we are assuming we don't know the actual windspeed, when this can be found by asking the nearest ATC unit for their ground windspeed, then adding the correction of twice that and add 30 degrees to find the wind velocity above 1000 ft.
.
OurvGS always works so no need for ATC and maths.

yanrair
1st Jun 2019, 23:05
The simple fact is that GS can be used in every phase of flight to back up pretty accurately PITCH POWER/WEIGHT /ALTITUDE TABLES provided by OEM.
It is possible to fly completely safely an entire flight just by reference to ground speed using two things
WIND
TAS INCREASE WITH ALTITUDE = 50kts/1000 ft
thats it.
And if you are caught in a sudden chaotic UAS + SHAKER + MULTIPLE WARNING just maintain current GS PITCH AND POWER.
if anyone thinks this doesn’t work get yourself on a sim. Right away. It does.
Safe flying
Y

itsnotthatbloodyhard
2nd Jun 2019, 01:39
It is possible to fly completely safely an entire flight just by reference to ground speed using two things
WIND
TAS INCREASE WITH ALTITUDE = 50kts/1000 ft


You’re sure about that?

harrryw
2nd Jun 2019, 04:15
[QUOTE][ou are not going to get a gps jam just as your birds or ice or whatever it is disables your air data systems. Not going to happen.
Its a cinch
TAS INCREASES BY 50 kt per 10000. So if the following are at a safe speed at MSL you have all you need is this knowledge
/QUOTE]
is the quote I think.

pineteam
2nd Jun 2019, 05:15
Yanrair, if it was a good idea to use GPS in an unreliable airspeed case, aircraft manufacturers would recommend using it.
Read your previous post again: 2 serious mistakes that in real life will put you in a dangerous situation. Don’t try to reinvent the wheel.

yanrair
2nd Jun 2019, 08:47
Yanrair, if it was a good idea to use GPS in an unreliable airspeed case, aircraft manufacturers would recommend using it.
Read your previous post again: 2 serious mistakes that in real life will put you in a dangerous situation. Don’t try to reinvent the wheel.
Some airlines do use GPS in UAS training.
OEM plane makers generally don’t teach airlines how to operate in difficult situations. In my last major airline a great deal of the training was developed locally
the fact that I made a typo in a previous post that was glaringly obviously a typo does not alter the fact that GS is a pretty foolproof way of avoiding calamity in serious confusing UAS situations with multiple distractions. Over years I have seen pilots flying calmly through situations which, if you don’t believe that GS is a game changer , would be extremely difficult if not fatal. If AF447 had maintained 450 kts and not changed pitch and power we wouldn’t be having the tenth anniversary this week of 300+ deaths.
So I am sorry, attempting to use a maths error in an otherwise proven scenario won’t change the science!
thanks for pointing out the error though. I wii shortly write an error free version which I will invite you to take apart on a factual basis!
y

itsnotthatbloodyhard
2nd Jun 2019, 09:17
GS is a pretty foolproof way of avoiding calamity in serious confusing UAS situations with multiple distractions.

So is applying the memory items and/or NNCs laid down by the manufacturer.

If AF447 had maintained 450 kts and not changed pitch and power we wouldn’t be having the tenth anniversary this week of 300+ deaths.

If AF447 had simply not changed pitch or power, with no reference to GS at all, the same would still be true.

It’s quite true that GS has its uses - the ‘Reference GS’ we used to use on approach in Boeings, and the similar GS Mini in the Airbus are good examples. But I don’t agree that GS is the infallible all-purpose solution you seem to believe it is, nor can you justify using it instead of the manufacturer’s procedures.
While the two major errors you’ve made so far in your justifications can be dismissed as mere typos or because it was late or something, the fact is you still made them, at zero kts, 1 G, and without the pressure of “sudden chaotic UAS + SHAKER + MULTIPLE WARNING”. It’s not really a great advertisement for what you’re trying to sell.

yanrair
2nd Jun 2019, 09:18
Yeah, I'm sure they would have had an accurate ground wind reading for AF 447.


Never mind that I've seen wind speed over 150kts without hurricane warnings on the ground.


https://www.pprune.org/professional-pilot-training-includes-ground-studies-14/

AF 447 and similar UAS incidents
The wind speed at the time of the pitot tube failure was right in front of the pilots as was the GS. Didn’t need ATC.
And the wind is available on every operational flight plan for every leg +/- 5 kts.
Had they done nothing which is what is recommended other than maintain existing steady state conditions inc. PITCH. POWER. GS we wouldn’t be having this conversation.
y

yanrair
2nd Jun 2019, 09:27
So is applying the memory items and/or NNCs laid down by the manufacturer.



If AF447 had simply not changed pitch or power, with no reference to GS at all, the same would still be true.

It’s quite true that GS has its uses - the ‘Reference GS’ we used to use on approach in Boeings, and the similar GS Mini in the Airbus are good examples. But I don’t agree that GS is the infallible all-purpose solution you seem to believe it is, nor can you justify using it instead of the manufacturer’s procedures.
I didn’t say instead of. I said in addition to. First response is always to stabilize using known PITCH POWER ALTITUDE WEIGHT ETC.
The existing steady state conditions are of course proven to work since that’s what you had just before the problem.
I repeat if AF 447 for example had done this they could not have stalled or indeed over speeded.
But after that you have to use a lot of logic to determine which if any or indeed all parameters are incorrect. And here GS is king. And as we can see here, there are people who don’t believe it! Good luck with that.
Y

yanrair
2nd Jun 2019, 09:40
Sorry. Someone just asked “ but if AF had just set PITCH POWER etc that should have been enough”
It would have been a good start. But pitch/power can be out by significant margins which can over the next few seconds / minutes degrade the condition. Speed can start falling if power say 2% too low say., due to ISA + 20 for example.
Nose needs to go up. Speed falls more YOU DONT KNOW THIS unless you notice your ground speed falling below where it was, or lower than flight plan.
essentially this is the very point. To sit there allowing the speed to change and knowing it’s happening is - well , not a good idea and can easily lead to
loss of control. I’ve seen this technique used successfully in the sim. Over and over and it works with no drama at all.
Cheers
y

yanrair
2nd Jun 2019, 09:47
STEP 4 737 QRH UAS
4 CrosschecktheIRSandFMCgroundspeedand winds to determine airspeed accuracy if indicated airspeed is questionable.

itsnotthatbloodyhard
2nd Jun 2019, 10:03
YOU DONT KNOW THIS unless you notice your ground speed falling below where it was, or lower than flight plan.
essentially this is the very point.

The flight plan GS is the average for a leg which might be over an hour long. Plenty of times I’ve seen the GS change by 40 or 50 kts in a couple of minutes, due to wind changes - which means GS is ok as a rough confirmation, but remains a fairly blunt instrument. Which is probably why the A330 procedure is AoA-based, and doesn’t refer to GS at all.

Goldenrivett
2nd Jun 2019, 10:11
Speed can start falling if power say 2% too low say., due to ISA + 20 for example.
Nose needs to go up. Speed falls more YOU DONT KNOW THIS unless you notice your ground speed falling below where it was,
If the nose needs to go up - then that is the indication you are flying too slowly!
You don't need ground speed to confirm that.

tomuchwork
2nd Jun 2019, 10:26
What's wrong with the tried and tested method of: "The correct attitude + correct power setting = correct speed?"

Having said that, at very low speeds landing away from an airfield (helicopter) I monitor the GPS groundspeed against the IAS to determine/confirm into wind or downwind on the approach.

Fully agree. That are the procedures made by the producer of the aircraft. It does not state "pull your phone and check the GPS speed for X-reference". Why? Well, every commerical pilot should be able to answer this question for himself. If it goes Ultralight/Light, why not. This things go so slow, huge stall margins, no harm to use a GPS GS there. But at airliner level it seems very unprofessionel - "children of magenta" springs to mind here. After flying "raw data" with FMC it may make perfect sense for some to use a GPS GS to figure out WHICH IAS indicator is the working one(and this is the goal of pitch/power values x-referenced for altitude, weight, configuration).

My advise, if it comes to that in real life - follow published procedures. It will keep your a** safe if you make it throught the "event"(which you should IF you follow unreliable airspeed procedures, they work like a charm(at least in Boeings and old Airbus(A300, do not know the new ones)).

FE Hoppy
2nd Jun 2019, 17:52
A bunch of AFCS systems revert to GS on approach in case of turbulence, even the bus. It's a fine reference for a minimum speed and the maths for wind correction isn't taxing. If you have nothing else then referring to GPS speed is an excellent idea and I've read it in more than one FCOM.

Here is what is says in my current QRH unreliable airspeed after pitch power initial items:

d) Check all available data sources, including:

• FMS, POS - GNSS for ground speed,
• FMS, POS - GNSS INFORMATION for GNSS ALT (if required),

yanrair
2nd Jun 2019, 20:02
If the nose needs to go up - then that is the indication you are flying too slowly!
You don't need ground speed to confirm that.
You are quite right but since 1 degree pitch change = about 7 knots - and don't forget you are hand flying so its not easy to judge pitch to within 1 degree, GS does is for you. Why rely on pitch and power only when you have a friend for free?

yanrair
2nd Jun 2019, 20:10
The flight plan GS is the average for a leg which might be over an hour long. Plenty of times I’ve seen the GS change by 40 or 50 kts in a couple of minutes, due to wind changes - which means GS is ok as a rough confirmation, but remains a fairly blunt instrument. Which is probably why the A330 procedure is AoA-based, and doesn’t refer to GS at all.
That is true on very long oceanic flights but we are talking generally here, and in any event, AF 447 went from safe light to chaos in a matter of a couple of minutes where is they had maintained steady state and GS that would not have happened.
And in the majority of cases you do know your wind speed very accurately. A lot of UAS incidents occur at low level and wind is known exactly. And it is at low level, AF 447 apart, that the problems usually need quick resolution. And GS does it for you every time.
Y

yanrair
2nd Jun 2019, 20:15
Yanrair, if it was a good idea to use GPS in an unreliable airspeed case, aircraft manufacturers would recommend using it.
Read your previous post again: 2 serious mistakes that in real life will put you in a dangerous situation. Don’t try to reinvent the wheel.

Dear Pineteam
They do. Another thread shows Airbus agrees with Boeing

Boeing STEP 4 737 QRH UAS
4 Crosscheck the IRS and FMCgroundspeed and winds to determine airspeed accuracy if indicated airspeed is questionable.

And the fact that I made an error earlier in a calculation has no bearing on the validity or otherwise of the arguments being put here. My error was made while lying in bed typing and trying to imagine the situation I was describing. In a real plane that would obviously not occur. Either GS is a good tool or it is not. It is recommended by Boeing to make use of it. It is then a question of HOW you do that. It is that question that we are unravelling here.
Cheers
y

itsnotthatbloodyhard
2nd Jun 2019, 22:42
If you have nothing else then referring to GPS speed is an excellent idea
Absolutely - if you’ve got nothing else, then you use whatever you can. But Airbus gives me a procedure to follow, and a set of pitch/thrust tables which will establish the jet within a couple of knots of the speed it’s supposed to be at. Sure, we can back it up with a check of the GS, but that’s going to be secondary.

don't forget you are hand flying so its not easy to judge pitch to within 1 degree
Sorry, I disagree. Any competent pilot should have no trouble setting and maintaining an attitude to within 1 degree. Otherwise just maintaining level flight will be a problem, and a raw data ILS will be a bit of a dog’s breakfast.

L337
2nd Jun 2019, 23:02
Whatever.

I'll use the GPS down final, you use your tables.

I will do what ever my company SOPs tell me to do. I sure as hell am not going to make up my own checklist.

yanrair
2nd Jun 2019, 23:16
I will do what ever my company SOPs tell me to do. I sure as hell am not going to make up my own checklist.
hi there L337
unless you fly a non Airbus or Non Boeing your SOPS tell you to refer to GS
Boeing STEP 4 737 QRH UAS
4 Crosscheck the IRS and FMCgroundspeed and winds to determine airspeed accuracy if indicated airspeed is questionable.
Cheers
y

itsnotthatbloodyhard
2nd Jun 2019, 23:36
unless you fly a non Airbus or Non Boeing your SOPS tell you to refer to GS

Sorry, this is not true. The A330/A340 FCOM has procedures for Unreliable Speed Indication, IAS Disagree, and All ADR Off - and NOWHERE does it make any mention of groundspeed. Nor does the FCTM.

yanrair
3rd Jun 2019, 10:05
Sorry, this is not true. The A330/A340 FCOM has procedures for Unreliable Speed Indication, IAS Disagree, and All ADR Off - and NOWHERE does it make any mention of groundspeed. Nor does the FCTM.
Ah! OK, Body. Point taken if so. Another posting here from an Airbus guy spoke of "reviewing IRS GS data" as part of the procedure. I will have to try and find it. Any other Airbus people out there confirm of deny?
All I can say is that next time we have an AF 447, and we will, lack of that excellent GS data in your toolbox will be a terrible shame!.
It happened to me yesterday on my boat actually. Sailing along in fog with no visibility at 6knots indicated boat speed. . Boatspeed went to zero instantly - weed I guess = bird strike on plane? Blocked pitot due ice? No way of verfirying by visual reference due to fog.
But, GPS reading 6 knots still so I knew we hadn't really stopped and knew which of the two was telling the truth.
And the engine was still at 2000 revs and, there was no current at the time, aka wind to us pilots!
Now if I had not looked at GS I would. have had a reasonable idea that we were still doing 6 knots since the steady state conditions still existed, and the engine was still going at 2000 revs. But the GS confirmed it and was quite nice to have.
The rest of the trip back was done on GS only. And because I knew the tidal steams - up to 3 knots (half my boat speed at times so equivalent to 300 its wind in a jet) I knew my boat speed too. All the time very accurately.
But I digress as usual because I learned to fly when Pontius was a pilot and pilots were real men. No ladies then. Back to my therapist now.
ps I did fly 737-800 sim. until a year or so ago as a TRE examiner so not utterly senile or out of date.
And I can still an inverted circuit in a 737 sim - taught to me by a Red Bull ace of my acquaintance !
Happy flying
Y

yanrair
3rd Jun 2019, 10:10
I will do what ever my company SOPs tell me to do. I sure as hell am not going to make up my own checklist.
Good thing for Sully he did not follow company procedures and for all the passengers aboard. Or the BA 747 with quadruple engine failure which wasn't in any book. Had to improvise the whole thing. And.............loads of others. Sioux City comes to mind.
Yes of course you use company procedures but as an experienced airline pilot you bring much more to the party than reading checklists that may or may not reflect your actual situation. I think it is called airmanship or some other archaic word like that!
Cheers and thanks for the post.
Y

pineteam
3rd Jun 2019, 11:37
Except you don’t need to improvise in the case of an unreliable airspeed procedure. Just maintain pitch and thrust it works just fine. Then and only then a quick check at your GPS speed....Yeah if you want. Not required by Airbus QRH tho.:p
When I fly raw data departure, I always set 10 degrees pitch and CLB thrust and the speed always sit at 250kt +-5kt. It’s super accurate and very easy to remember the pitch/ thrust setting. At least approximately enough to fly 1 or 2 min safely to give time to the PM to find the accurate pitch and thrust setting without overspeeding or stalling.
Most of the time, If you do nothing the plane will keep flying perfectly fine. Relax and take your time. :cool:

tomuchwork
3rd Jun 2019, 12:26
Good thing for Sully he did not follow company procedures and for all the passengers aboard. Or the BA 747 with quadruple engine failure which wasn't in any book. Had to improvise the whole thing. And.............loads of others. Sioux City comes to mind.
Yes of course you use company procedures but as an experienced airline pilot you bring much more to the party than reading checklists that may or may not reflect your actual situation. I think it is called airmanship or some other archaic word like that!
Cheers and thanks for the post.
Y

yanrair

You are taking reference to "catastrophic" events and compare them to a simple blocked pitot or other system failure creating a single airspeed indicator to fail(or 2)?

You are NOT on the path to good airmanship, you are just heading in the right direction to deliver your license to the nice man behind the counter. IF there are no published procedures for a certain failure(e.g. the ones you mentioned), OF course you revert to experience and good airmanship.
If the CAPTAIN deems it necessary to deviate from procedures it is his right to do so. BUT afterwards he will need to explain what(and why) he did to the nice guys on the green table.

FlightDetent
3rd Jun 2019, 14:50
For some, knowing the book and how to use it is just un-airman like. Swallow it, children of iBooks. :E

yanrair
3rd Jun 2019, 21:01
Except you don’t need to improvise in the case of an unreliable airspeed procedure. Just maintain pitch and thrust it works just fine. Then and only then a quick check at your GPS speed....Yeah if you want. Not required by Airbus QRH tho.:p
When I fly raw data departure, I always set 10 degrees pitch and CLB thrust and the speed always sit at 250kt +-5kt. It’s super accurate and very easy to remember the pitch/ thrust setting. At least approximately enough to fly 1 or 2 min safely to give time to the PM to find the accurate pitch and thrust setting without overspeeding or stalling.
Most of the time, If you do nothing the plane will keep flying perfectly fine. Relax and take your time. :cool:
Dear Pineteam
Thats what I have been saying all along, with the addition of taking GS into account too. At the time of failure maintain status quo and if it was working a moment ago, it still will. And will continue to do so for a time. AF 447 for example.
GS extends your 1-2 minutes almost infinitely . Even if you don't know the wind ( which you will) In your scenario settle at 250 its GS with pitch and power accordingly. Unless you have a headwind or tailwind in excess of 50 kts you are perfectly safe. Your IAS must be in the range 200-300 which are both safe. Neither too fast nor too slow. And if the wind is stronger than that you will surely know about it and take it into account.

In AF 447 if GS had been kept at 450 kts and level flight , nothing could have gone wrong. nothing. No need for immediate reference to tables from manufacturer which need to be accessed and understood.

The major accidents due to UAS all get into major speed errors way outside these sort of numbers due to total disorientation and confusion. Yet right there is your GS to help stabilise things.
Y

yanrair
3rd Jun 2019, 21:14
yanrair

You are taking reference to "catastrophic" events and compare them to a simple blocked pitot or other system failure creating a single airspeed indicator to fail(or 2)?

You are NOT on the path to good airmanship, you are just heading in the right direction to deliver your license to the nice man behind the counter. IF there are no published procedures for a certain failure(e.g. the ones you mentioned), OF course you revert to experience and good airmanship.
If the CAPTAIN deems it necessary to deviate from procedures it is his right to do so. BUT afterwards he will need to explain what(and why) he did to the nice guys on the green table.
Dear Tomuchwork

I am indeed talking catastrophe since we are discussing how to avoid AF 447 and ET and Lionair and lots of others where the crew did or may have lost complete control due to overload, confusion and stress. It was a simple blocked pitot system that caused AF 447 which the pilots managed to turn into a catastrophe because - they didn't fully appreciate how to handle loss of airspeed information coupled with multiple warnings and AP disconnect. In ET and Lionair it looks like a failure of AOA started a chain of events that led to major overspeed of the plane. Not talking MCAS here, just loss of airspeed info and stick shakers.
In AF 447, having pitched the aircraft to some 15 deg. nose up and losing almost all airspeed, there was only one way out, and this is not covered in any manual I can assure you. They had about 15 seconds to realise, put plane into a very steep dive of about 40 degrees to break the stall and gently pull out over perhaps 30 seconds so as not to pull the wings off. Something like that, and it was not going to happen since first of all they had no idea what was going on, but IF THEY HAD it was all over anyway since to break a deep stall you have to dive, in the dark over the ocean decisively.In short you need to understand how to get out of a deep stall.
I confess that we may be into thread creep here so apologies. My point is, that "simple blocked pitot or other system failure creating a single airspeed indicator to fail(or 2)?" has caused many a crash.
Y

yanrair
3rd Jun 2019, 21:26
QUOTE
If the CAPTAIN deems it necessary to deviate from procedures it is his right to do so. BUT afterwards he will need to explain what(and why) he did to the nice guys on the green table.

REPLY
You seem to have a very jaundiced view of airline management - perhaps from bitter personal experience?
In my last job, I was the man who sat behind the green table, actually red. And if any of our captains had made a decision which he carried out in the belief it was the right thing to do (not negligent or foolhardy) but was wrong with the benefit of hindsight, then it was treated as such and no action would be taken except to learn from it and publish it to the rest of the pilots as a learning exercise. it is in this manner that we all learn. One of the mysteries for me is how following Lion Air, that every pilot on the MAX worldwide wasn't an expert in all the factors that led to the loss of that plane. Publishing the Boeing Bulletin is not enough.

If a captain deliberately behaved in a manner that was against training, airmanship, common sense and was done with malice aforethought, that would be a different story. An example might be disregarding a hard GPWS warning.
Y

Bergerie1
4th Jun 2019, 05:18
yanrair,

At one time in my career I also used to sit behind that 'green table' but mine was an old wooden desk. I had the same attitude as you about learning from experience and helping people in their jobs. The most important thing was to analyse what had happened and then publish what had been learnt. Some while ago I wrote a note on the slavish adherance to SOPs. I quote the final few paragraphs here:-

"However, despite all these considerations, it is impossible for the SOPs to cover every eventuality. There then comes the point when they are not appropriate to the situation and the captain decides to deviate from them. This is an extreme measure and should only be done when there is no other option and when the pilot has sufficient knowledge to understand fully the implications of what he is doing. I can think of several examples.

Suppose on take-off at maximum weight in a four engine aircraft (a 747 with multiple landing gears) at a hot and high airfield, birds are ingested into both engines on the same side. Then, when airborne only a few feet above the ground, and barely able to climb, the co-pilot calls positive rate of climb, but the captain elects to leave the gear down until more speed and altitude has been gained. Non-standard, but his reasoning is that the extra drag of the open doors and wheel wells will probably cause the aircraft to sink back towards the ground.

Suppose on final approach all engines suddenly stop. The captain elects to retract the flaps one notch. Non-standard, but the drag reduction is just sufficient to stretch the glide and make the airfield.

Suppose in mid-Atlantic, the underfloor cargo fire warning lights illuminate, the crew have reason to believe the warning is genuine and divert to the Azores. When they arrive the weather has deteriorated, the cross-wind has risen above limits and the cloud base has descended to below decision altitude. There is nowhere else to go and it is imperative to land. They do so successfully. All three examples were genuine events. It is not difficult to dream up other scenarios where such actions may be necessary.

And one more to ponder: the Qantas Airbus A380 at Singapore when a turbine disc exploded causing extensive damage and multiple unrelated warnings. In what order should the crew action the various procedures, which should be ignored and which have to be actioned?

My conclusion, therefore, is that normally flight crews should always obey the SOPs, even in an emergency, yet there may still be times when circumstances may dictate otherwise. Then, and only then, is it permissible and maybe essential to deviate, but this must be done in the full knowledge of ALL the implications. SOPs are for the guidance of wise men and not necessarily to be slavishly followed."

Not all flight managers act in the draconian manner that some posters here on Proone seem to think!

Goldenrivett
4th Jun 2019, 09:58
Dear Pineteam
Thats what I have been saying all along, with the addition of taking GS into account too. At the time of failure maintain status quo and if it was working a moment ago, it still will. And will continue to do so for a time. ...
GS extends your 1-2 minutes almost infinitely . Even if you don't know the wind ( which you will) In your scenario settle at 250 its GS with pitch and power accordingly. Unless you have a headwind or tailwind in excess of 50 kts you are perfectly safe. Your IAS must be in the range 200-300 which are both safe. Neither too fast nor too slow. And if the wind is stronger than that you will surely know about it and take it into account.

Y
Hi yanrair,

You need to include TAS effect with altitude.
In Pineteam's example of climbing away at 250 kts, climb thrust and 10 degrees of pitch works simply perfectly well. If you try to rely on Ground Speed and ignore wind component (when <50 kts) and TAS - then you will be in error by an additional 40 kts by 10,000 feet on the climb. (Your IAS must be in the range 160-260 kts - which is probably not safe).

KISS is the better solution.

yanrair
4th Jun 2019, 11:55
Sorry, this is not true. The A330/A340 FCOM has procedures for Unreliable Speed Indication, IAS Disagree, and All ADR Off - and NOWHERE does it make any mention of groundspeed. Nor does the FCTM.
I see this reply from a " BUS" pilot - you say there is no reference to GS and he says there is??
Would be good to know since I cannot imaging different Airbuss having different procedures??
Thanks for looking into it. All helps
Y

A bunch of AFCS systems revert to GS on approach in case of turbulence, even the bus. It's a fine reference for a minimum speed and the maths for wind correction isn't taxing. If you have nothing else then referring to GPS speed is an excellent idea and I've read it in more than one FCOM.

Here is what is says in my current QRH unreliable airspeed after pitch power initial items:
Quote:
d) Check all available data sources, including:

• FMS, POS - GNSS for ground speed,
• FMS, POS - GNSS INFORMATION for GNSS ALT (if required),

yanrair
4th Jun 2019, 12:14
Hi yanrair,

You need to include TAS effect with altitude.
In Pineteam's example of climbing away at 250 kts, climb thrust and 10 degrees of pitch works simply perfectly well. If you try to rely on Ground Speed and ignore wind component (when <50 kts) and TAS - then you will be in error by an additional 40 kts by 10,000 feet on the climb. (Your IAS must be in the range 160-260 kts - which is probably not safe).

KISS is the better solution.
Hi Pineteam
It is simple at all altitudes - KISS I agree with.


The correlation between IAS and TAS/GS looks like this – 50 kts per 10,000 feet.

IAS G/S





Sea Level 260 260 /0

FL 100 260 310 /+50

FL 200 260 360 /+100

FL 300 260 410 /+150

Cruise Alt (350 ish) 260 460 /+200



How to use this? You only need to memorise the approximate G/S/ TAS for four flight levels and you have a guide which would have saved Air France. If they had only stayed at the current conditions of about 2 degrees of pitch,
80% N1 (or whatever cruise power was at the time) IVSI ZERO (works off IRS as well as pressure changes) AND…. Kept the ground speed at 460 kts ( or whatever it was just after the failure) they would have had no difficulty in staying in full control. But they did not know this correlation.Or any correlation for that matter.

Here is a graph used in training in one airline...........

https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/521x428/2019_06_04_12_13_15_0c4a9fa87462a7c3db28d26e97ab6cdb4eaeb9ad .png

yanrair
4th Jun 2019, 12:26
yanrair,

At one time in my career I also used to sit behind that 'green table' but mine was an old wooden desk. I had the same attitude as you about learning from experience and helping people in their jobs. The most important thing was to analyse what had happened and then publish what had been learnt. Some while ago I wrote a note on the slavish adherance to SOPs. I quote the final few paragraphs here:-

"However, despite all these considerations, it is impossible for the SOPs to cover every eventuality. There then comes the point when they are not appropriate to the situation and the captain decides to deviate from them. This is an extreme measure and should only be done when there is no other option and when the pilot has sufficient knowledge to understand fully the implications of what he is doing. I can think of several examples.

Suppose on take-off at maximum weight in a four engine aircraft (a 747 with multiple landing gears) at a hot and high airfield, birds are ingested into both engines on the same side. Then, when airborne only a few feet above the ground, and barely able to climb, the co-pilot calls positive rate of climb, but the captain elects to leave the gear down until more speed and altitude has been gained. Non-standard, but his reasoning is that the extra drag of the open doors and wheel wells will probably cause the aircraft to sink back towards the ground.

Suppose on final approach all engines suddenly stop. The captain elects to retract the flaps one notch. Non-standard, but the drag reduction is just sufficient to stretch the glide and make the airfield.

Suppose in mid-Atlantic, the underfloor cargo fire warning lights illuminate, the crew have reason to believe the warning is genuine and divert to the Azores. When they arrive the weather has deteriorated, the cross-wind has risen above limits and the cloud base has descended to below decision altitude. There is nowhere else to go and it is imperative to land. They do so successfully. All three examples were genuine events. It is not difficult to dream up other scenarios where such actions may be necessary.

And one more to ponder: the Qantas Airbus A380 at Singapore when a turbine disc exploded causing extensive damage and multiple unrelated warnings. In what order should the crew action the various procedures, which should be ignored and which have to be actioned?

My conclusion, therefore, is that normally flight crews should always obey the SOPs, even in an emergency, yet there may still be times when circumstances may dictate otherwise. Then, and only then, is it permissible and maybe essential to deviate, but this must be done in the full knowledge of ALL the implications. SOPs are for the guidance of wise men and not necessarily to be slavishly followed."

Not all flight managers act in the draconian manner that some posters here on Proone seem to think!
Dear Bergerie
Looks like we went the same college of airmanship.
I could add many more to that list - a lot of folk think that every time the manufacturer must have thought out a solution and it is in the good book. But no. Boeing make great planes but I always used to say, "they don't know how to fly them in an airline environment." And they don't even try. A Boeing FCOM 1 (user handbook if you own a washing machine) barely scratches the surface of how to operate an airliner.
Take 767 engine fail at 30W mid Atlantic. QRH says descend to drift down altitude. (FL 330) and set up MCT. It happened to one of my guys. He did nothing of the sort , arguing that that to sit there at MCT on the remaining engine was inviting a second failure. So, he descended to FL 200 and flew along at a nice low power setting - way below MCT to Gander where he landed with no drama and without having gunned his remaining engine for 2 and a half hours. Why do Boeing not say this? For the reason that you state - it is beyond the scope of the QRH and of course you might, just might need that extra altitude to give you extra range if your diversion field is at ultimate distance. But with Gander so close this didn't matter. And so airmanship kicked in. Funny old archaic thing that used to be prevalent.
Y
Cheers
John

FlightDetent
4th Jun 2019, 13:22
Dear John.

You keep missing the point where AF447 crew failed to maintain the normal pitch of 1-2.5, deg and a hefty dose of thrust (makes no difference if 80 or 95 N1), failed to do nothing just keep the ESSENTIAL two parameters the same. Giving them an Excel graph, forcing to memorize it, would greatly help them - I think not. Quite on par with the act where you could not add up HW and TW correctly, and thus the precision GS method to reach IAS = Vref = 100 at touchdown would put your followers into a stall with IAS of 60 kts at 2500 ft. :)

If the traits you claim to have are true, surely you see that a method which has its proponent fail to calculate correctly, (let alone explain it over a few days), from the comfy space in front of a computer screen, is of absolutely no use to a crew in distress.

Leading Airman worth their salt understand that if a crew fails to execute a procedure the solutions are: (any combination of)
- focus the syllabus, enabling a better understanding of priorities
- raise the fail/pass standard, enforcing a better drill
- simplify the underlying procedure

Adding overlay mumbo-jumbo procedures only makes things worse for the next unfortunate lot. Severely worse as a matter of fact.

fdr
4th Jun 2019, 18:04
yanrair,

My conclusion, therefore, is that normally flight crews should always obey the SOPs, even in an emergency, yet there may still be times when circumstances may dictate otherwise. Then, and only then, is it permissible and maybe essential to deviate, but this must be done in the full knowledge of ALL the implications. SOPs are for the guidance of wise men and not necessarily to be slavishly followed."

Not all flight managers act in the draconian manner that some posters here on Proone seem to think!

Complex situations that exceed the boundaries of SOP's and NNCL's/QRH/FCOM procedures happen. When the books are placed in the corner and the crew have to roll up their sleeves and deal with the real world, the value of the procedures that are now not necessarily being followed still exists; the very fact that the crew are electing to deviate means that there is a change in conditions outside of normal. If that is a result of error, or stress, interruption or other cause, the fact that what is happening is different is highlighted and that is a trigger for crew to contemplate. The vast majority of events that occur remain within the guidelines of the procedures that have been developed. Occasionally they go way outside. The stress of malfunctions is exacerbated by control difficulties, or where the warning systems are swamped by cascading alerts. The handling stuff goes back into the past, there may be a bit of wishful thinking about better performance in the old days, there were many examples of tragic loss of flight control in the past, not so dissimilar to the most recent events. One concern in many of the events is that getting out of sorts, many events have data showing full back stick being applied contrary to a rational recovery from the loss of control condition. That includes 1st world top flight programs as well as other operations with less stellar reputations. Not too many aircraft will survive a continuous back stick input (notwithstanding the MCAS saga's) in a stall or departure. When the data shows roll rates over 180 degrees a second on a Part 25 aircraft, there is a hint that not all was well in the handling dept. Point is, humans in stressful situations have a wide range of performance outcomes in dealing with the issues confronting them. The industry had the sober lesson of SR111, which showed that disciplined methodical process may not always be the best option.

With the level of operation, I would think that the industry overall doesn't do a bad job dealing with abnormal conditions; for the number of events that occur every day the wild rides while distressing are not a great rate of occurrence, the problem is the consequential impact to the individuals concerned.

yanrair
5th Jun 2019, 17:49
Dear John.

You keep missing the point where AF447 crew failed to maintain the normal pitch of 1-2.5, deg and a hefty dose of thrust (makes no difference if 80 or 95 N1), failed to do nothing just keep the ESSENTIAL two parameters the same. Giving them an Excel graph, forcing to memorize it, would greatly help them - I think not. Quite on par with the act where you could not add up HW and TW correctly, and thus the precision GS method to reach IAS = Vref = 100 at touchdown would put your followers into a stall with IAS of 60 kts at 2500 ft. :)

If the traits you claim to have are true, surely you see that a method which has its proponent fail to calculate correctly, (let alone explain it over a few days), from the comfy space in front of a computer screen, is of absolutely no use to a crew in distress.
Adding overlay mumbo-jumbo procedures only makes things worse for the next unfortunate lot. Severely worse as a matter of fact.

Dear Flight Detent
You have referred before to my appalling mathematical ability when in bed using an iPhone to respond to these forums, which I have admitted to. Mea Cupla. I give in. Indeed since then I have now resorted to responding wide awake and in front of my large screen with a keyboard. Like now.
And I have pointed out that on a real flight deck with real instruments in front of me, failed or otherwise, I would not have any trouble sorting out wheat from chaff. It is not so easy when trying to picture HW/TW etc and putting it down on paper remotely in a theoretical setting. But now armed with paper and pencil, I will try again.
And in your QUOTE above you don't memorise the graph. It is carried at hand for reference and can be used in seconds. But you do memorise the 50 its per 10,000 feet increase in TAS with altitude, which isn't too hard because I can do it.

First I must object to you repeatedly using my maths errors in a previous post, which I have since corrected, to suggest that the use of GS in UAS is a not worthy of consideration. Either it is a good idea or it is not, and Boeing have it in Line 4 of the QRH for UAS. What I am trying to get going here is a discussion about HOW it might be used effectively, which it most certainly can. I know that from training if you ask a pilot what line 4 in the QRH means, you get some very divergent answers! And that is not good at all , at all, as they say in my part of the world.
BOEING QRH 737-400 Line 4. CROSS CHECK IRS AND FMC GS AND WINDS TO DETERMINE AIRSPEED ACCURACY...................

If I had suggested the world was round and not flat, but made an error in part of the discussion, using your logic, you can reject the entire argument on the basis of an error in one part. Tackle the ball - not the man.
From various replies here you can see that many pilots do indeed find GS useful and I find it more than useful. So do Boeing. Otherwise it wouldn't be in the QRH.
It is useful all the time and particularly on the approach when GS +/- the wind is more or less the same as IAS, so it is absolutely accurate in that situation. Likewise after takeoff. On one or two previous types we flew the approach using a minimum GS, and the Airbus does it automatically using GS mini, I think it is called. But let's not go there.
At altitiude there is a very simple table which I know you don't like, which resolves the issue of not being at MSL.
On a point here, have you ever actually done any of this for real? It sounds to me as if you haven't. I have flown using GS alone umpteen times in the sim. in all sorts of situations (was trained this way on the 737-200 which had doppler GS before GPS) and it transforms what was always a difficult exercise into something entirely manageable.
And as someone else has pointed out. PITCH/ POWER tables are set for a particular airspeed and configuration, and if you set the pitch and power while at a totally different speed, it won't work. GS sorts this out for you.
Example. 737-400 from QRH tables Straight and level flight at 52 tonnes 737-400. 210 knots is 6 deg NU and 60% N1. The "six and sixty rule known by most 737 guys I know).

Now, if you are at 340 knots that won't work and you will be in a climb of about 2000 fpm with rapidly decreasing airspeed and very confused indeed.
I am really trying to engage politely here in what is a very serious matter and I hope we can continue the discussion calmly and tackle the core issues of how are we going to fly our plane in wide range of situations using the GS as a reference as given to us in the QRH.
Over, but not out, yet!! Off to see my therapist now...........
Cheers
Y

yanrair
5th Jun 2019, 18:10
POST 103 FROM Bergerie
And one more to ponder: the Qantas Airbus A380 at Singapore when a turbine disc exploded causing extensive damage and multiple unrelated warnings. In what order should the crew action the various procedures, which should be ignored and which have to be actioned?

Bergerie
This warrants its own thread I think since in some ways it is the root of everything we are discussing here. QF had 64 (I think) different failures. Safe landing a long time later. Amazing bunch of highly qualified guys on the flight deck including an expert on systems. No fire.
1968. GARWE BOAC 707 takes off from LHR with severe engine failure and fire. A bit like Concorde. Back on ground in something like 5 minutes. Plane burned out but many survived. All would have died if captain had started doing "procedures". He knew the plane would not survive too long and landed.
Interesting isn't it and worthy of discussion perhaps elsewhere?
Y
https://en.wikipedia.org/wiki/BOAC_Flight_712

Goldenrivett
5th Jun 2019, 21:41
.......
1968. GARWE BOAC 707 takes off from LHR with severe engine failure and fire. A bit like Concorde. Back on ground in something like 5 minutes. Plane burned out but many survived. All would have died if captain had started doing "procedures". He knew the plane would not survive too long and landed.
Interesting isn't it and worthy of discussion perhaps elsewhere?
https://en.wikipedia.org/wiki/BOAC_Flight_712

Hi yanrair,
If only the Fire Control Handle had been pulled on No 2 engine during the Engine Fire Check List, then the LP fuel valve would have closed and there would not have been a fuel fire in the Pylon.
see page 20 of https://www.era.lib.ed.ac.uk/bitstream/handle/1842/5259/A3.C.A.P.%20324%20Civil%20aircraft%20accident%20Report%20on% 20the%20Accident%20to%20Boeing%20707-465%20G-Arwe%20at%20Heathrow%20Airport,%20London%20on%208th%20April% 201968.pdf?sequence=1&isAllowed=y
Then perhaps Capt. Taylor would not have had to demonstrate such exceptional skill and judgement.

yanrair
5th Jun 2019, 23:45
Hi yanrair,
If only the Fire Control Handle had been pulled on No 2 engine during the Engine Fire Check List, then the LP fuel valve would have closed and there would not have been a fuel fire in the Pylon.
see page 20 of https://www.era.lib.ed.ac.uk/bitstream/handle/1842/5259/A3.C.A.P.%20324%20Civil%20aircraft%20accident%20Report%20on% 20the%20Accident%20to%20Boeing%20707-465%20G-Arwe%20at%20Heathrow%20Airport,%20London%20on%208th%20April% 201968.pdf?sequence=1&isAllowed=y
Then perhaps Capt. Taylor would not have had to demonstrate such exceptional skill and judgement.

Yes indeed Goldenrivett!
Thats what happened though like Papa India, the design was poor. It allowed you to fire the bottles without having fully pulled the fire handle. My memory is that it was partly pulled. As we know on later models you have to twist the fire handle positively to arm the bottles and it is all annunciated with warning lights.
“A superior pilot is one who exercises superior knowledge to avoid using his superior skill”. Always true. But having found they had an engine fire out of control the point is he got it on the deck in 4 minutes. That sort of thinking isn’t taught today.
i have seen airline crews in sim. with severe engine failure- ok no uncontrolled fire, take 50’minutes to complete the checklists. That’s a long time with an engine that exploded!

Goldenrivett
6th Jun 2019, 10:11
Thats what happened though like Papa India, the design was poor. It allowed you to fire the bottles without having fully pulled the fire handle. My memory is that it was partly pulled.

According to the accident report - the handle was never pulled. See Page 20.
"On this occasion the difference between the two drills, was in advertently obscured by the Flight Engineer, who went for, but did not pull, the fire shut-off handle whilst carrying out the Engine Overheat or Failure Drill; it appears that this not only gave him the impression that he had pulled the fire shut-off handle as part of the fire drill, but also gave the same impression to the First Officer."

BOAC had 2 similar procedures then - with the vital difference of pulling or not pulling the FCH. The crew started one procedure - then changed when they realised the fire warning. They thought the handle had been pulled - but actually it had not.
Later the two procedures were were amalgamated into one - to make it simpler.

KISS principal again.

FlightDetent
6th Jun 2019, 13:06
No twist. Stabilize plane setting sensible pitch power for conditions. You are now safe. Then refer to GS to ENSURE that your previous setting have achieved a safe airspeed and keep it there.yIt is upside down indeed. They ask you to use gps ALTITUDE which on the Bus is accurate within 100 ft

FlightDetent
6th Jun 2019, 13:47
Yanr, let's get this straight. Two key points will be enough.
First I must object to you repeatedly using my maths errors in a previous post, which I have since corrected, to suggest that the use of GS in UAS is a not worthy of consideration.A) Stop twisting.1) I had not used your math errors before, ever. Even in the post you have in mind, and that was only once, I used the CORRECTED math, which is the one that would have put the crew into a stall at Vref-40 kt.
2) I did not suggest GS was not worthy of consideration in UAS. Au contraire, post #47 "This thread inspires me to include GS in that scan the next time."

B) Heed your own advice
Tackle the ball - not the man.

...you do memorise the .... which isn't too hard because I can do it. ...
...On a point here, have you ever actually done any of this for real? It sounds to me as if you haven't. ...
... you can reject the entire argument on the basis of an error in one part ....
... very simple table which I know you don't like ....
... Off to see my therapist now...

--- now, if we can play neat ---

About the GS uses i.a.w. present OEM guidance:

you decided to quote BOEING QRH 737-400 Line 4. CROSSCHECK IRS AND FMC GS AND WINDS TO DETERMINE AIRSPEED ACCURACY................... It does not say "to determine airspeed accurately" as in: and then fly the GS, which is what you seem to propose through the previous posts.

The full version from my copy (click here) (https://i.postimg.cc/vHBBf10q/UAS737cl.png): says below the dashed line
4. Cross check the IRS and FMC ground speed and winds to determine airspeed accuracy if indicated airspeed is questionable.
-> To me that reads: try with GS to figure out if any of the ASI can be trusted and the scale of the error at hand. No mention of flying anything through GS.

The Airbus instructions are somewhat different, (click here for the basic scheme (https://i.postimg.cc/JnpQYDZ6/UASairbus-1.png)).

- The last element in FCTM wording: "Flight using pitch/thrust references or the BackUp Speed Scale (BUSS, below FL 250), if the troubleshooting has not enabled to isolate the faulty ADR(s)." has almost a full page of explanations. No GPS reference at all.

- The "Troubleshooting and Isolation" does not mention GPS or GS at all, again. Though in cruise I personally would. Looking at the CoFP and comparing the printed GS against the present display readout, keeping in mind the difference between the two observed previously.

- The "Flight path stabilization" is where they acknowledge use for GPS altitude. As a suggestion, after what is already 20 lines of text in that paragraph on how to fly stabilized. The GPS altitude can be used to confirm that the aircraft is maintaining level flight.


...how are we going to fly our plane in wide range of situations using the GS as a reference as given to us in the QRH. There no reference to do that in the 737 QRH. There is whatsoever no reference to GPS GS in any of the UAS / ADR / Disagree procedures on A320/A330, FCOM, QRH, FCTM and memory items included.

I have no issues with your graph, which is correct and valid. The observation was: For the sorry AF447 crew who that night did not have the ken to maintain the cruise pitch and not touch the thrust-levers, memorizing certain datapoints of it (50 kt/ 10k ft) would not have helped.
Later, when fully stalled and perplexed due to the confusing indications both active and missing, the meaning of 60 kt-ish GS could have lit a spark that could have saved them all, definitely yes - but even for that the TAS table is absolutely irrelevant.

I do opine, OTOH, that the claim of flying accurate speed under UAS using a GS readout is bogus. The present procedures - which do not include any GS at all - give good enough result within 10 knots already as they are. Attempt to finetune that with GS would most likely unsettle the whole process, given the dynamic nature of the atmosphere itself. Very different outside compared to the SIM one.

Pass my greetings.

yanrair
6th Jun 2019, 21:59
According to the accident report - the handle was never pulled. See Page 20.
"On this occasion the difference between the two drills, was in advertently obscured by the Flight Engineer, who went for, but did not pull, the fire shut-off handle whilst carrying out the Engine Overheat or Failure Drill; it appears that this not only gave him the impression that he had pulled the fire shut-off handle as part of the fire drill, but also gave the same impression to the First Officer."

BOAC had 2 similar procedures then - with the vital difference of pulling or not pulling the FCH. The crew started one procedure - then changed when they realised the fire warning. They thought the handle had been pulled - but actually it had not.
Later the two procedures were were amalgamated into one - to make it simpler.

KISS principal again.
apolgies I think we are into thread creep territory?
Yes that’s true. The engineer thought he had but hadn’t. The point is that you could fire the bottles without having pulled the fire handle which masked the error. On a 737 for example that can’t happen Anyway it was not done correctly I agree. What happened next is what I’m saying is almost unthinkable today- to land in four minutes. 4 passengers died. Plane totally burned out in a very short time. All you need to land is the wheels. Nothing else. No speeds weights or dumping needed -180 will do on long runway. And that’s pretty much what they did.

yanrair
7th Jun 2019, 05:46
apolgies I think we are into thread creep territory?
Yes that’s true. The engineer thought he had but hadn’t. The point is that you could fire the bottles without having pulled the fire handle which masked the error. On a 737 for example that can’t happen Anyway it was not done correctly I agree. What happened next is what I’m saying is almost unthinkable today- to land in four minutes. 4 passengers died. Plane totally burned out in a very short time. All you need to land is the wheels. Nothing else. No FMC Entries , speeds weights or dumping needed -180 kts will do on long runway. And that’s pretty much what they did.
The BOAC logic was that for simple engine failure with no fire you didn’t need to pull fire handle. After “WE” they changed to “always pull fire handle” - you can always push it / twist it back again. Y

yanrair
7th Jun 2019, 10:45
Reply to thread 116
quote. I used the CORRECTED math, which is the one that would have put the crew into a stall at Vref-40 kt.

So again we are saying that using GS can be proven unworkable because of something I wrote earlier. I have reworked the argument since then without, I think, mistakes and it the basic premise that GS is a tool that is much misunderstood in its usefulness (or otherwise of course) which should be addressed.
If I were to prove that the world is round in a dissertation and accidentally suggested that the earth is 93,00,000 miles from the sun and has a circumference of 24 000 km, then some using this logic, might suggest that world might be flat. Because I made an error(s). But despite those errors the earth is still round, unless of course one belongs to that society in London.
So to the key points
We all accept now, and we did not at the start, except some still calling GS "bogus" , that GS has its uses and everyone seems to agree that where you have Airspeed Disagree, GS is great for sorting out which of three ASIs is the functioning one. Transfer control to other pilot. Continue drinking tea which didn't even spill. That's the easy one but even that I have seen screwed up into a nightmare if badly handled.

Now, a dark and dirty night with all three ASIs frozen at differing speeds, and perhaps overspeed warnings coupled with underspeed and possibly stick shakers. AP has disconnected. First Officer continued to follow Flight Directors for a while which has messed up the pitch and power. So you are there with almost no valid information and I bet very frightened.
The only source now is a set of tables in the QRH which must be accessed and the correct set extracted from many different configurations - and of course our first officer is not familiar with these tables having only seen then during training. And the tables only work if you at the flight level, weight and configuration stated AND the SPEED stated. if during the upset just related, the speed has gone elsewhere (AF447 and ET being examples where the speed was a couple of hundred knots away from the condition that pre-existed, they are of no use at all.
To the rescue our GS whereby I just fly the GS that I see now, or return it to where it was.
In this situation I would simply set my approx. Pitch Power depending on Flight Level ,which knowledge no pilot should be without, and maintain my safe groundspeed which existed at the time of the failure. Or as stated on the flight plan. Or what I remember it to be. Thats it, safe and a long way from either stall or overspeed.
Taking an easy one. I have this problem after takeoff clean. Maybe FL 50 climbing. Set "six and sixty" and 250 GS. And level off. Don't accelerate or decelerate. Calm restored. Now consult QRH which says for 52 tonnes, 240 knots, 6 deg pitch and 64% N1 (data from 737-400 QRH date 2010 ). Set 65% and monitor GS so that it stays around 250 kts. Can adjust for wind of course. Return to land using pitch and power but keeping the speed in the band quoted in the tables using GS all the way down.
I think that is the briefest explanation I can offer without the A level maths.
And I have done it umpteen times and it works.
Safe flying.
y

Y

Capn Bloggs
7th Jun 2019, 11:23
I do opine, OTOH, that the claim of flying accurate speed under UAS using a GS readout is bogus. The present procedures - which do not include any GS at all - give good enough result within 10 knots already as they are.
I'll weigh back in here. I don't think anybody is claiming that GS will give you an "accurate" speed, depending on how it is defined. But what stands out like dog's balls to me is that if GPS GS was used in these two scenarios, the speed could have been actively controlled/limited to enable continual overriding of the MCAS at a mid-speed instead of Vmo.

From an old 737 FCOM, the 70 tonne flap Up holding power is only 66% N1. The UAS is what, 75%? Even with a slight climb (UAS Memory Items) the speed is going to start increasing, and as the speed increases, the drag reduces and the acceleration increases. The Ethiopians were dead in 5 minutes, commencing the last dive at Vmo. Do you lot really think that, with all that was going on, pulling out the QRH and going through the tables while maintaining the UAS memory Items was actually going to work? The Lion Air guys had the QRH out, apparently. They were flying for 11 minutes and still dived into the ocean at warp speed. The GPS GS would have told them all they needed to know about the speed. Ignore it at your peril.

FlyingGourmet
5th Oct 2022, 11:27
Hey guys, I‘m trying to find from where the GS indication on the ND comes from. In the FCOM it says ADIRU speed but when you check the Airspeed Unreliable NNC there it states that GS on ND is reliable. Thanks