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Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: MrNoBody
Date: October 27, 2021 11:40AM
OK, I understand the need for air-speed and temperature sensors but...
watching a report on Boeing's MCAS system and I'm puzzled as to why an
external, mechanical Angle of Attack sensor is the only option.
This device is complicated! All kinds of moving parts, even a heater.
Plus, it requires a properly trained tech to calibrate it for accuracy.
Looking @ my iPhone & all its sensors, I am thinking there must be
some electronic solution that could be mounted internally and be as or
more accurate. As I understand, AOA is the aircraft's pitch. What am I missing??

UTC Aerospace product sheet (PDF)

a basic parts breakdown of the external sensor (#53 is the Vane):




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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: ztirffritz
Date: October 27, 2021 11:58AM
It would need to go through FAA approval. iPhones are probably not approved for that use on commercial airliners.



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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Paul F.
Date: October 27, 2021 12:09PM
Getting a new sensor system approved would be most definitely "non trivial".
To give you an idea - Hard drives, or solid state drives, could be used in Flight Data Recorders. They've been ready for prime time for decades.
Flight Data Recorders still use reel to reel magnetic tape...
Getting a new data recorder certified would cost (if I remember the article I read correctly) hundreds of millions of dollars, ten years, and enough paperwork to fill three Semi-truck trailers.

Moving to Angle of Attack sensors from a phone?
Maybe in 50 years... maybe.



Paul F.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Racer X
Date: October 27, 2021 12:25PM
Now, starting from scratch, from the ground up, a lot of this is circumvented.

This is why SpaceX and Blue Origins can do in a decade what the big boys haven't been able to do in 3 times as long. Overcoming inertia in a massive organization is very hard to do.

With small companies, the FAA can say fix it, and Space X puts some people on it, they come up with an idea, get approval from the boss, and do it. The FAA looks at it, and it moves forward or goes back to the designers. All in a VERY short time frame.



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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: MrNoBody
Date: October 27, 2021 12:36PM
Quote
Paul F
Getting a new data recorder certified would cost (if I remember the article
I read correctly) hundreds of millions of dollars, ten years, and enough
paperwork to fill three Semi-truck trailers.
That's interesting especially considering the 'coziness' between the FAA
and the manufacturers (& Congress)!
So it's a classic case of "We've got to protect our phony, baloney jobs".

Quote
ztirffritz
iPhones are probably not approved for that use on commercial airliners.
Not an iPhone per say, that was just an example of all the specialized sensors
possible using electronics vs electomechanical.
$10 IC vs $Thousands for old technology.



39°36'17"N 75°44'43"W

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Taxman by Joe & Nancy's Rich Ice Cream Band
The Humpty Dance by The Harris-Brown Hookup
Lets Spend The Night Together by The Fang-Swalwell Gang
Díaz-Canel Is A Friend of Ours by The AOC Squad
My Old Kentucky Retirement Home by MitchMcC & The Soggy Boxer Boys
Burning Down The House by Merrick & The Goons
Back In the USSR by Bernie's Red Square Trio

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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Racer X
Date: October 27, 2021 12:44PM
When we first went back to Mars in the '90s, they actually dredged back up the 500# thruster engines used in the '70s, but designed back in the '60s, and used them.

They were already tested and approved.

The first tests for the new missions, were done using a test mule thruster that had been sitting in a crumpled cardboard box under a workbench in an engineer's garage for 2 decades. It was recertified very quickly, because there was a voluminous paper trail attached to it and it gave them a quick start on the project. It's 80K worth of hardware, and 2 million worth of paperwork.

The technology isn't the problem, the paperwork is.



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The police have no duty to respond. See Castle Rock v. Gonzales, 545 U.S. 748 (2005) or Warren v. District of Columbia[1] (444 A.2d. 1, D.C. Ct. of Ap. 1981)



Edited 1 time(s). Last edit at 10/27/2021 01:03PM by Racer X.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: JoeH
Date: October 27, 2021 01:12PM
One thing no one has mentioned, is that "angle of attack" is not a simple measurement of pitch. It is relative to the direction of airflow, so at the same pitch it will be different when the plane is ascending or descending as compared to level flight. The same thing will happen if there is an element of downdraft or updraft to the air the plane is flying through.

So not just a simple substitution of an internal sensor that just can measure the pitch angle. There would still be a requirement for an external sensor to detect the exact direction of the airflow the plane is passing through.



Edited 1 time(s). Last edit at 10/27/2021 01:48PM by JoeH.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: STL
Date: October 27, 2021 01:37PM
AOA and pitch angle are not the same.

The Pitch angle (attitude) is the angle between where the airplane is pointed and the horizon.

The Angle of attack (AOA) is the angle between the oncoming air or relative wind and a reference line on the wing. Wing lift and stall are directly related to a wings AOA. That's one reason AOA is so important.

An example of the difference between pitch angle and AOA can be seen by watching some videos of airplanes on final approach to an aircraft carrier. The aircraft’s pitch attitude is above the horizon but it’s direction of flight is down toward the deck. Check out this video at about 4:30.
[www.youtube.com]

Accurately measuring AOA requires a sensor on the outside of the airplane. The sensor you cited must freely rotate in order to align itself with the oncoming air. Icing can inhibit free rotation which can result in lag, inaccurate readings or even a stuck sensor. As a result a heater is included to keep the AOA sensor from icing.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Will Collier
Date: October 27, 2021 01:48PM
Quote
Racer X
Now, starting from scratch, from the ground up, a lot of this is circumvented.

This is why SpaceX and Blue Origins can do in a decade what the big boys haven't been able to do in 3 times as long. Overcoming inertia in a massive organization is very hard to do.

With small companies, the FAA can say fix it, and Space X puts some people on it, they come up with an idea, get approval from the boss, and do it. The FAA looks at it, and it moves forward or goes back to the designers. All in a VERY short time frame.

Yep. Old friend of mine is the chief engineer for a small company that buys and retrofits surplus military airframes, loads them up with current tech avionics and resells them to foreign customers. Their final products are light-years ahead of what's in the current US versions of those aircraft, and the US program leads will admit it. But they can't start over and do the same things on the DOD side, because a Program of Record has "too many mouths to feed," both Government and vendor.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: testcase
Date: October 27, 2021 02:22PM
"Plus, it requires a properly trained tech to calibrate it for accuracy."

That pretty well sums up ALL (99+%) of the parts on "non-experimental" aircraft. Remember, ANY in-flight "oops" must be dealt with while the aircraft is aloft. NO "pulling to the side of the road" or setting out a sea anchor and then calling for a mechanic.


"Now, starting from scratch, from the ground up, a lot of this is circumvented. "

I SERIOUSLY doubt that oversimplification.


"This is why SpaceX and Blue Origins can do in a decade what the big boys haven't been able to do in 3 times as long. Overcoming inertia in a massive organization is very hard to do."

Again, another oversimplification. Part of it is that IF you're spending YOUR OWN MONEY, that one standard. You want the government to foot the bill; now you've opened up a HUGE can of worms. We're talking Apples vs Oranges. What makes it so confusing is that it sounds SO similar (but it is NOT).
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Will Collier
Date: October 27, 2021 04:47PM
Quote
testcase
"Plus, it requires a properly trained tech to calibrate it for accuracy."

That pretty well sums up ALL (99+%) of the parts on "non-experimental" aircraft. Remember, ANY in-flight "oops" must be dealt with while the aircraft is aloft. NO "pulling to the side of the road" or setting out a sea anchor and then calling for a mechanic.


"Now, starting from scratch, from the ground up, a lot of this is circumvented. "

I SERIOUSLY doubt that oversimplification.


"This is why SpaceX and Blue Origins can do in a decade what the big boys haven't been able to do in 3 times as long. Overcoming inertia in a massive organization is very hard to do."

Again, another oversimplification. Part of it is that IF you're spending YOUR OWN MONEY, that one standard. You want the government to foot the bill; now you've opened up a HUGE can of worms. We're talking Apples vs Oranges. What makes it so confusing is that it sounds SO similar (but it is NOT).

I don't know anything about SpaceX or Blue Origin operations as far as regulatory stuff, but slapping "EXPERIMENTAL" on the airframe cuts through a ton of FAA red tape, and that's how most small outfits handle it. That introduces lots of issues in who and how you can operate and sell it to, but that's the trade-off.

I will say this, I have a former colleague who went to work for the FAA, and the first thing he found out was that the one way you're guaranteed to get in trouble there is by working more than 40 hours in a week...
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Racer X
Date: October 27, 2021 06:52PM
How do they handle "All Hands On Deck" crash situations then? I know they are NTSB's purview, but the FAA is very much involved as well. Is that the exception, like certain jobs only?



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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: MrNoBody
Date: October 27, 2021 09:12PM
Shout out to JoeH and STL, excellent explanations!
thumbsup smiley
Now I understand why an internal only sensor wouldn't work currently.

It's even clearer to me now how badly Boeing screwed the pooch with MCAS.



39°36'17"N 75°44'43"W

DuckDuckGo
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DemComm Records 2021 Greatest Hits
includes:
Taxman by Joe & Nancy's Rich Ice Cream Band
The Humpty Dance by The Harris-Brown Hookup
Lets Spend The Night Together by The Fang-Swalwell Gang
Díaz-Canel Is A Friend of Ours by The AOC Squad
My Old Kentucky Retirement Home by MitchMcC & The Soggy Boxer Boys
Burning Down The House by Merrick & The Goons
Back In the USSR by Bernie's Red Square Trio

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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Will Collier
Date: October 28, 2021 06:29AM
Quote
Racer X
How do they handle "All Hands On Deck" crash situations then? I know they are NTSB's purview, but the FAA is very much involved as well. Is that the exception, like certain jobs only?

Good question, I'll ask the next time I see him. He works in the D.C. Headquarters.
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Re: Any aeronautical mavens/pilots: question re aircraft external sensors
Posted by: Diana
Date: October 28, 2021 10:21AM
Quote
Will Collier
Quote
Racer X
How do they handle "All Hands On Deck" crash situations then? I know they are NTSB's purview, but the FAA is very much involved as well. Is that the exception, like certain jobs only?

Good question, I'll ask the next time I see him. He works in the D.C. Headquarters.

Overtime requires authorization. Even voluntarily working with the full knowledge that it will be unpaid work will get you in trouble. No “getting to a stopping point” or “just a minute” thing. If you are not sure you can get to such a point before the clock runs out then you just don’t start it. The only exception I saw was if there was someone who worked the next shift would take it and finish it. That is, IF there was another shift.

Certain jobs may require a bit of possible overtime and such will be clearly spelled out in the job description. Most government civilian jobs are hourly; few jobs will be “salary.” I never encountered one that was, so I admit that caveat. Keep in mind that some military may work a similar job and those folks are 24-hour on-call.

Once you get high enough, such as positions requiring a doctorate degree, things can change. Job descriptions at that level will often say “travel may be required” or state that it may be overnight, and specify the approximate amount; some may state that occasional overtime would be expected. I have a friend from grad school working at the FAA in OKC working forensics. I can ask him about it and how they handle it.

And of course, there are levels above that. A further dive into the subject gave me the terms I had long forgotten: competitive service (as described above), excepted service, and senior excepted service, all of which have their own hiring practices and as such, have their own job requirements.

Diana, ex-DoD competitive civil service worker.
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