ET crash ADD NBO

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ian16th
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Re: ET crash ADD NBO

#821 Post by ian16th » Sun Nov 03, 2019 7:22 pm

boing wrote:
Sun Nov 03, 2019 5:19 pm
Part of the solution would be to introduce AoA sensor technology that did not require a sensor that is so delicate and prone to damage.

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A question from someone who is ignorant of the technology involved.

With my smart phone, somehow it senses which way, portrait or landscape, that I am holding it.

Can this technology be used to accurately and quickly to determine AoA?
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Re: ET crash ADD NBO

#822 Post by Fox3WheresMyBanana » Sun Nov 03, 2019 8:06 pm

AoA measures the angle between airflow and the wing longitudinal axis to give an indirect reading of wing performance.
Theoretically, if one knew the aircraft velocity vector, aircraft attitude, aircraft ground position, and assumed that the air outside was blowing horizontally, one could calculate what the AoA must be.
Your smartphone uses 3 solid state accelerometers, in orthogonal directions, on a chip to determine which way up is relative to the phone. By integrating the readings over time one can estimate velocity, and by integrating again one can get position. The accelerometers however do not know which way up really is, but give an estimate based on the assumption that the only acceleration is caused by gravity. When you move the phone, I don't know whether is allows for this by taking a time average, putting a delay in after a significant velocity is detected, or waiting till velocities are stable again (and there may be other ways). In a dynamic situation (with accelerations), the accelerometers need an independent means of knowing which way up is. This might come from GPS, but I would not think the updates would be sufficient and accurate enough to provide a useful AoA substitute, and it would still rely on assumptions about what the air outside is doing. It would not work correctly in situations such as downdrafts near CBs, for instance.
An AoA gauge needs to be far enough out from the aircraft skin to avoid friction effects, in a place where it can be at 90 degrees to the airflow, and where there isn't much turbulence. This is usually at the first point back from the nose where the fuselage flattens out, i.e. just aft of the nose. It also needs to be thin enough that it doesn't cause significant aerodynamic effects itself. Skinny things sticking out will always be at risk of damage, which usually rules out mounting it underneath. so they are usually about halfway up the fuselage

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Re: ET crash ADD NBO

#823 Post by boing » Sun Nov 03, 2019 8:41 pm

Fox beat me to it, I thought he would but here goes.

To keep it simple, the AoA is the angle between the wing and the airflow around the wing, this simple concept is enough to understand the problem at hand. Since the wing is fixed in place on the aircraft a simple calculation allows the AoA sensor to usually be mounted near the nose of the aircraft close to the other sensors rather than associating it physically with the wing itself.

The basic AoA sensor itself is mind bogglingly simple. It is just a wind direction sensor as you see on a home weather station system but it is mounted with its axle horizontally rather than vertically. (See various images in a web browser). As the airflow moves past the sensor the vane aligns with the airflow, when the vane is forced upwards by the airflow it indicates a high AoA (aircraft nose high) and conversely, when the vane is forced down it indicates a low AoA (aircraft nose low). [FOX will be cringing by now but lets keep things simple]. The AoA sensor has to be carefully calibrated to provide correct results for use by automatic systems and cockpit indication.

Here are the problems with this usual design.
It is a moving part mounted on a shaft and it is relatively delicate.
It can adopt any position on the ground because it is subject to wind effects and an exterior inspection cannot confirm condition.
It is usually mounted in a fairly vulnerable position which can encourage damage from jetways, airstairs and catering vehicles.
It is subject to icing.
It is vulnerable to bird-strikes.
It requires precise calibration.
Pilots have to understand the sometimes not intuitive display.

So, how can we replace it with a better sensor. I have knowledge of two alternatives but I do not know how well they work. One alternative is a simple tube with precisely made holes in it that somehow senses the airflow around the tube and measures AoA. The other is a system I have heard of in theory but have never seen, it is mounted in the wing itself. The projecting tube system would seem to have almost as many objections as the vane system and the wing system may be subject to wing contamination such as ice..

Advances in technology such as have been made in cell-phones could possibly lead to improved AoA sensors but we will always be in the position of needing to measure physical airflow to operate the sensor. For example, a cellphone like sensor could be used to measure the vane position but the vane itself would still need to be mounted in the airflow. The originality of thinking of the cellphone designers could produce a breakthrough and certainly the reduced physical size of circuitry and its reliability would be a big factor. I am imagining that a fairly short fixed vane mounted on a flat plate pierced with multiple small holes connected to pressure sensors may be worth looking at. The pressure sensed at the multiple holes will vary with the AoA in a very complicated way but it may just be possible that with computing power now available that these pressure readings can be turned into AoA data.


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Re: ET crash ADD NBO

#824 Post by boing » Sun Nov 03, 2019 8:55 pm

Just an additional thought on one versus multiple AoA sensors.

The AoA sensor in an airliner is going to do several jobs. It can carry out critical functions such as helping to prevent the aircraft stalling, it could provide a critical safety back-up in case of primary airspeed indicator failure and it will probably be used by the auto-flight system to operate the aircraft more efficiently.

As long as the auto-flight system doesn't do anything stupid after an AoA failure I don't really care about that function so a single channel is OK..

Back-up of regular airspeed indications. Hey, this important but there are other techniques that we are taught to deal with the problem and most aircraft do not have an AoA display in the cockpit so it can't help them in any case. Single channel is OK.

Stall or other flight situations where the AoA data may actually control the flight path of the aircraft. As we have seen with the MAX this is extremely important. There should never, repeat NEVER, be an occasion where a single channel AoA system can control the aircraft - there is just too much chance of damage to the system by birdstrike or icing.


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Re: ET crash ADD NBO

#825 Post by Fox3WheresMyBanana » Sun Nov 03, 2019 10:04 pm

FOX will be cringing by now but lets keep things simple
Fox is not cringing, and I thought your description very well done. :YMAPPLAUSE:
I have taught 11 year olds as well as lecturing at Uni - one should always use language appropriate to the audience.

Just a reminder that having single channel sensor control of critical systems has always been a certification no-no, and everybody at Boeing and the FAA know that. MCAS is corporate manslaughter in my opinion, but there's zero chance of anyone even being directly fired over it. Indirectly, people will be fired if Boeing starts losing serious money. Large corporations and the entire financial world are just immoral gambling these days, and your life is just another casino chip to too many of them.

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Re: ET crash ADD NBO

#826 Post by Slasher » Sun Nov 03, 2019 11:31 pm

Back-up of regular airspeed indications. Hey, this important but there are other techniques that we are taught to deal with the problem and most aircraft do not have an AoA display in the cockpit so it can't help them in any case. Single channel is OK.
Looks like you two blokes have answered all that adequately so no point me saying anything as it’d be simply rehashing the same.

Only thing I’ll add is that the all Scarebi have had for the last few years is a thing called ‘Fly the Green’. This occurs with complete loss of IAS and all ADRs are switched off. A green band appears on each pilot’s ASI on the respective PFD which utilises the FMGS FAC component of AoA.

An online search Airbus Fly The Green will explain it.

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Re: ET crash ADD NBO

#827 Post by ian16th » Sun Nov 03, 2019 11:46 pm

Gentlemen,
Thank you.
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Re: ET crash ADD NBO

#828 Post by barkingmad » Mon Nov 04, 2019 8:32 am

A recent video of the Max PFD showed the (optional at extra cost!) AoA indicator shrunken and parked in the top right-hand corner of this already busy display.

If one or two are to be fitted to line aircraft then why not a separate larger analogue indicator up on the coaming(s) with a big fat white needle on a black background akin to the BA engine instrument fit instead of the ghastly EFIS mod on the first 737-300/400/500 series named as a contributing factor in the Kegworth disaster??!

If this sensor is to perform a useful function it needs to be out there visually waving at the unfortunate pilots as they try to communicate over the cacophony of stall warning and/or overspeed synthetic noises.

If my trusty Cold War 50s technology Avro steed had one fitted in this position as a result of stalling accidents then rocket science it definitely ain’t!

The mobile phone technology may have a use but so far the performance of the built-in compass in my I-phone fails to convince me. More often than not it regularly moves the ridge line of my house roof off track by 30 degrees or more when not being affected by local magnetic influences. The web is full of queries on the reliability of this widget and I’m sure it in conjunction with map widgets will ensure lots of callouts for our search & rescue helos.

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Re: ET crash ADD NBO

#829 Post by ian16th » Tue Nov 05, 2019 8:02 pm

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Re: ET crash ADD NBO

#830 Post by TheGreenGoblin » Wed Nov 06, 2019 10:08 am

Meanwhile Dennis Muilenburg's job is safe for the moment and he is not taking his "incentive", but then again none of the Boeing staff will be getting one either.
After two days of brutal, back-to-back grilling in Washington that, among other things, focused on the size of CEO Dennis Muilenburg’s compensation, the Boeing boss told the board of directors he would not be taking a bonus this year. But, then, neither are Boeing’s other managers.

According to a report in The Seattle Times, Boeing told its employees in an internal memo, “With only one quarter left in the year, the grounding since March of the 737 MAX and the associated financial effects have severely impacted the company’s performance by limiting the ability to deliver planes and collect on customer contracts. The company does not see a path to achieving an incentive payout for 2019.” Last year, Boeing employees in Washington state collectively took home almost $429 million in incentives, nearly $7000 per employee.
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Re: ET crash ADD NBO

#831 Post by TheGreenGoblin » Wed Nov 06, 2019 10:10 am

And Michael O'Leary becomes even more frustrated.
In other MAX news, Irish low-cost carrier Ryanair is sounding alarm bells ahead of its 2020 travel season, claiming that a late delivery of its MAX aircraft, now expected in March or April 2020, could seriously impact its capacity in next year’s high season. “We have now reduced our expectation of 30 Max aircraft being delivered to us in advance of peak summer 2020 down to 20 aircraft and there is a real risk of none,” Ryanair CEO Michael O’Leary told The Guardian. “We have already reduced our passenger growth forecast … we may have to cut that again but, frankly, there is no point in keeping on changing the number until we get more certainty."[/quote
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Re: ET crash ADD NBO

#832 Post by Rwy in Sight » Wed Nov 06, 2019 11:17 am

TheGreenGoblin wrote:
Wed Nov 06, 2019 10:10 am
And Michael O'Leary becomes even more frustrated.
In other MAX news, Irish low-cost carrier Ryanair is sounding alarm bells ahead of its 2020 travel season, claiming that a late delivery of its MAX aircraft, now expected in March or April 2020, could seriously impact its capacity in next year’s high season. “We have now reduced our expectation of 30 Max aircraft being delivered to us in advance of peak summer 2020 down to 20 aircraft and there is a real risk of none,” Ryanair CEO Michael O’Leary told The Guardian. “We have already reduced our passenger growth forecast … we may have to cut that again but, frankly, there is no point in keeping on changing the number until we get more certainty."[/quote
When the he is upset I am always curious about the size of discount will calm down.

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Re: ET crash ADD NBO

#833 Post by barkingmad » Wed Nov 06, 2019 1:56 pm

Perhaps M O’L looking for a good excuse to lay off crew in a shrinking market?

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Re: ET crash ADD NBO

#834 Post by OFSO » Sun Nov 10, 2019 12:09 pm

Where did I read the news that Ryanair have withdrawn three 738's from service after cracks found in the picklefork wing/fusalage attachment ?

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Re: ET crash ADD NBO

#835 Post by barkingmad » Sun Nov 10, 2019 6:56 pm

OFSO, maybe here amongst others?

https://www.businessinsider.com/ryanair ... ?r=US&IR=T

Or was your query purely rhetorical......?

“Read all abaht it” on the ‘30 Quantas aircraft’ thread. :-\

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Re: ET crash ADD NBO

#836 Post by Fox3WheresMyBanana » Wed Nov 13, 2019 2:44 pm

Air Arabia looks likely to order 120 Airbus 320s rather than 737MAXs.
Boeing officially pushes MAX earliest in service date back to January next year
https://www.reuters.com/article/us-airb ... XN19M?il=0

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Re: ET crash ADD NBO

#837 Post by ian16th » Wed Nov 13, 2019 4:14 pm

Fox3WheresMyBanana wrote:
Wed Nov 13, 2019 2:44 pm
Air Arabia looks likely to order 120 Airbus 320s rather than 737MAXs.
Boeing officially pushes MAX earliest in service date back to January next year
https://www.reuters.com/article/us-airb ... XN19M?il=0
But what sort of delivery dates can Airbus offer?
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Re: ET crash ADD NBO

#838 Post by llondel » Wed Nov 13, 2019 5:33 pm

"You can have it next week but you can't fly it for another six months."

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Re: ET crash ADD NBO

#839 Post by Rwy in Sight » Wed Nov 13, 2019 8:20 pm

ian16th wrote:
Wed Nov 13, 2019 4:14 pm
Fox3WheresMyBanana wrote:
Wed Nov 13, 2019 2:44 pm
Air Arabia looks likely to order 120 Airbus 320s rather than 737MAXs.
Boeing officially pushes MAX earliest in service date back to January next year
https://www.reuters.com/article/us-airb ... XN19M?il=0
But what sort of delivery dates can Airbus offer?
Isn't that irrelevant as Boeing supposedly has no cancellations hence deliveries will have to follow all other orders? llondel you do sound optimistic about those six months, maybe?

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Re: ET crash ADD NBO

#840 Post by ian16th » Wed Nov 13, 2019 9:06 pm

I asked about AIRBUS deliveries.

I should imaging they are going to struggle to meet the demand.
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