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.

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

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.
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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.

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.

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-...nd-studies-14/

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

Interestingly, today I was reading the report into an A320 Pitot Blockage 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.

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.

Good point, yes it is.

Can GPS measure dynamic pressure ?

Did you say no ?

There's your answer then.

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

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.

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! :}

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. =)

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.

[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.

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.