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A life saving instrument in your pocket?

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A life saving instrument in your pocket?

Old 15th May 2019, 00:16
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A life saving instrument in your pocket?

I was answering a question on Quora about finding yourself without gyro instruments in an aircraft. I talked of the Foxtrot November accident - a Viscount of British Eagle carrying a known fault that couldn't be found for weeks.

At the end I suggested a backup via a phone App. Intrigued, I tried CockpitAid and was astonished; the movement extraordinarily lifelike. I don't have an aircraft to try it in, but is it conceivable it could be used in an emergency?

I'm going to try it in the car tomorrow to see how unwanted accelerative forces affect it.
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Old 15th May 2019, 01:32
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Originally Posted by Loose rivets View Post
I was answering a question on Quora about finding yourself without gyro instruments in an aircraft. I talked of the Foxtrot November accident - a Viscount of British Eagle carrying a known fault that couldn't be found for weeks.

At the end I suggested a backup via a phone App. Intrigued, I tried CockpitAid and was astonished; the movement extraordinarily lifelike. I don't have an aircraft to try it in, but is it conceivable it could be used in an emergency?

I'm going to try it in the car tomorrow to see how unwanted accelerative forces affect it.
I am going to say that it won't work. Your phone has accelerometers so it can sense change movement. It doesn't have gyroscopes, so it doesn't have a frame of reference needed to really back up your instruments. So if you're in a coordinated turn the horizon on your phone app would show straight and level. Sure someone else can explain better, there are several gyro equipt adsb receivers for sale that do back up your instruments.
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Old 15th May 2019, 02:44
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But a mobile phone does have gyroscopes and has for many years. Here is a very old article.
https://memsblog.wordpress.com/2010/...r-cell-phones/
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Old 15th May 2019, 04:08
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Originally Posted by harrryw View Post
But a mobile phone does have gyroscopes and has for many years. Here is a very old article.
https://memsblog.wordpress.com/2010/...r-cell-phones/
And I thought I knew things....
You are absolutely right about the MEMS sensors. I tried getting my ipad to display flight instruments in the foreflight app and it wouldn't, so I assumed....
I will download a few apps and test next week when I fly!
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Old 15th May 2019, 13:43
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Not on a phone , but believe it or not, the latest advances use the system from MSFT kinect sensor.
This is pixel oriented, no moving parts and hyper accurate. These are found mostly in UAV and helo platforms.

On the iPhone/iPad gyro...

Gyroscope: Starting with the iPhone 4, 4th Gen. iPod touch, and iPad 2 there's another sensor: a three-axis gyroscope. When combining the gyroscope with the accelerometer, this combo gives these devices six axes on which it can operate. This is designed to make the devices more sensitive, responsive and powerful for gaming, allowing them to react based on how the devices are held and moved.

The iPhone 4 utilizes a microscopic, electronic version of a vibrational gyroscope, called a MEMS gyroscope. Chipworks has confirmed that the MEMS gyroscope found inside the iPhone 4 is nearly identical to an off-the-shelf TMicroelectronics L3G4200D gyroscope.
When a user rotates the phone, the proof mass gets displaced in the X, Y, and Z directions by Coriolis forces. An ASIC processor senses the proof mass' displacement through capacitor plates located underneath the proof mass, as well as finger capacitors at the edges of the package.


Accelerometer/Motion sensor: This sensor enables the iPod touch, iPad, or iPhone’s screen to automatically switch from landscape to portrait modes and back again based on whether you’re holding the phone vertically or horizontally.

I added this, and it comes in handy when buying used equipment...

Moisture sensor: All of these devices contain this sensor, though it's not visible in the onscreen interface or accessible through the iOS. The moisture (or water) sensor is a little red tab that appears in the Dock Connector after the phone has been submerged in water. It can also appear as a red dot in the headphone jack, depending on the model. If you're buying a used iPhone, it's a good idea to check for this indicator to make sure the device hasn't been damaged by water.
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Old 15th May 2019, 14:34
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I'm wondering how phones accomplish the equivalent of an IRU alignment. And how frequently they have to realign due to drift.
Over a short time a phone or touchpad might work well as an attitude indicator. Assuming that in the event of an emergency (loss of primary instruments), when you pick it up it knows which way is up.

I'm guessing that phones might perform some sort of alignment when left sitting motionless for a period of time. Which can be determined by its accelerometers.
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Old 15th May 2019, 16:49
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The sensors in phones do drift a lot. They basically realign pretty much constantly to the local gravity vector, which is kinda bad in long turns. There was a neat little app once, that basically just showed an ADI, i put it on the footrest of a 737 and everytime we did a cruise turn, it showed the turn correctly in the beginning, and then would very rapidly align to straight and level although we were still in a turn. That was a while ago, i believe with an iPhone 6s Plus, haven't tried it on my current X (which is already kinda oldish), it might have gotten better. The IRU functions with similar sensors in consumer drones and even RC planes with envelope protections (yes, that is a thing) do work quite well. however, flight times are usually in the range of up to 20 minutes, not much longer.

That said, even the mini-EFIS standby horizons do tend to drift quite a bit, check them out after a turn of some medium duration once you are straight and level again, they usually still show (an opposite) turn for a few minutes afterwards, gradually returning to straight and level.
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Old 15th May 2019, 18:20
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Salute!

TNX. Eengr.
gotta align the “platform” to Earth or space coordinates first.
The new sensors are orders of magnitude better than the ones we saw 60 years ago when inertial systems were all the rage. So drift rates and angular resolution have also improved. Prolly biggest thing that made all this possible is much better clocks. Yes, clocks. And chips that worked at ghz versus MHz or kHz.
The crystal oscillators and means to count each vibration improved and got better. So in late 60’s we saw watches that only lost seconds per month! And it only got better.
GPS is best example of what a super time system can do. We get mm position data for mapping by using the rf carrier wave and resolving the phase angle!

You can can screw up the iPad or iPhone alignment by rotating it about 40 or 50 degrees the first minute or two once it is on. Makes for a good science project your grandkid could do.

Gums sends...
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Old 15th May 2019, 23:28
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The sensors in phones do drift a lot. They basically realign pretty much constantly to the local gravity vector, which is kinda bad in long turns.
of course, the kalman filters do not have the latency built in to adjust for turns like the ac does, or in a climbing/descending turn...

Update rate on the iPhones/iPads is a real issue, as they are constantly searching and trying to connect, thus burning battery rate.

We are running the iPhone 8, the same stuff, even when connected to the ac wifi/bluetooth.
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Old 16th May 2019, 05:44
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After all mobile phones need regular calibration (some times need to calibrate each time you open the app). This cannot be done while flying
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Old 16th May 2019, 07:30
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Donít phones also use GPS?
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Old 18th May 2019, 07:13
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I read somewhere that back in the day guys would put half full glass of water on top of the panel to determine if they were straight and level or in a bank/pitch. Basically turning the water level in a glass into an AH indicator.
Not sure how true those stories, and I guess wouldn't work well in turbulence, but there is logic in it...
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Old 19th May 2019, 08:41
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but there is logic in it...

.. actually, no logic at all. Or, as Bob Hoover might observe, just to show how it doesn't work that way

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Old 19th May 2019, 16:40
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I've flown with several pilots that either thought they could continue a flight without instruments, "I know I can. I've done it". To a lad that answered one of my off-the-cuff training days with the glass of water answer. A friend, a jet transport skipper, suggested I make a horizon myself - "using pure pendulosity." I was very, very surprised, but said nothing. He too had flown with John Dawdy in Fox November.

My friend, Col Carl Crane (very worth a Google) devoted a chunk of his life promoting the use of gyro instruments. Some agreed, saying, yes, they work . . . until you go into cloud.

Carl was test flying blind landing kit he'd patented almost every day, until he died suddenly - at my age now. Gulp.
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Old 19th May 2019, 16:54
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He lived a tad longer than I thought. But just look at this:- Found it behind the picture of a memorial which I think was on the land I lived on.

Carl studied at St. Mary's University, San Antonio, and the University of Dayton (Ohio), where he received the bachelor (1924) and the master of mechanical engineering (1934) degrees. After graduating from the United States Army Advanced Flying School at Kelly Field in 1925, he spent two years with the First Pursuit Group at Selfridge Field in Michigan, and then for five years was a flight instructor at Kelly, Brooks, and Randolph fields in Texas. In 1929 he teamed with William C Ocker to devise revolutionary flying systems and to write the world's first manual for instrumental flight, Blind Flight in Theory and Practice (1932).

On August 23, 1937, at Wright-Patterson Air Force Base, Carl Crane made the world's first fully automated landing, for which he had designed the key instruments. He served in military aviation until 1949.
Carl's love of flying never waned. With my kids in his Texas hills cabin.


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Old 20th May 2019, 13:01
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Originally Posted by Uplinker View Post
Donít phones also use GPS?
Probably. I know that many of the open-source autopilots for drones do; if you know how fast you're going (ground speed, not airspeed) and how tight the turn is then you can calculate what the expected centripetal acceleration is, subtract that from the measured acceleration, and get a good idea of where gravity is.

As for just using a phone by itself - the algorithms tend to be tuned for the intended application. For use in the air, it would make sense to place a greater reliance on the gyros and lesser reliance on the accelerometers; this will give you more time in a continued turn before the new "gravity" (a combination of real gravity and centripetal acceleration) starts to mess with your readings. The downside is that you'll be more prone to errors from the gyros drifting - but modern gyro drift rates should be pretty low. Getting it down to something approaching 0.05deg/s should be practical even with the sensors in a phone (ie selected for price, size, and power consumption - not accuracy) and that gives you a few minutes with the horizon mostly showing sensible data before the accelerometers have any significant effect.
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Old 20th May 2019, 14:11
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Salute!

Good poop, Slatye. If the device has a good GPS lock and decent filters, then it can do a lot for the local level presentation. Just look back a half a century to the doppler damped inertial mode we had in the A-7. Just having "truth" of movement across the Earth without actual position data helped the platforms we used in those days. By late 70's when I got to the Viper we didn't care bout all the gimbals and such and started using "wander angles" and such, but those did depend on good accelerometers and gyro sensors. The age of strapdown systems had begun!

There's a commercial app for the iPad that is alleged to be a virtual HUD. Anybody try that sucker?

Gums asks...
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Old 20th May 2019, 16:08
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The iPhone, (using a 6s), has a magnetic compass feature which, if one swipes left, turns into a horizon, and when placed on a flat surface, a level. It needs calibration so not sure how useful it would be long-term. The magnetic compass app doesn't appear to be available on the iPad, (5th gen).

Gums, I wouldn't call it a HUD, but there's a commercial app by the name of "Spyglass" and its cousin, "Commander Compass" which appear to show "HSI-like" indications along with altitude, groundspeed, VSI etc. if using GPS.
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Old 20th May 2019, 16:47
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Originally Posted by Loose rivets View Post
I was answering a question on Quora about finding yourself without gyro instruments in an aircraft. I talked of the Foxtrot November accident - a Viscount of British Eagle carrying a known fault that couldn't be found for weeks.

At the end I suggested a backup via a phone App. Intrigued, I tried CockpitAid and was astonished; the movement extraordinarily lifelike. I don't have an aircraft to try it in, but is it conceivable it could be used in an emergency?

I'm going to try it in the car tomorrow to see how unwanted accelerative forces affect it.
So, I just tested it with a Pixel 2 (new smartphone), it is definitely not a safe backup. after about 10 seconds in a coordinated turn, it slowly returns to wings level. When coming out of that turn it shows turning in opposite direction. The only value would be to keep the wings level if you started wings level.....
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Old 21st May 2019, 02:22
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One is tempted to remind that in the absence of an AH, one still has the VSI, the altimeter and the compass and stopwatch to fly straight and level, or turn, climb, descend.......
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