What does prop rpm have to do with AHRS?

[DanWEC]

On the G1000, an AHRS failure has the same effect as a GMU failure.
Autopilot works, but no HDG or NAV modes, only alt and roll/CWS.


Dan

[teacher]

We we had our dual AHRS failure we were told that it was not possible. Like I said, we lost everything but. A tiny attitude indicator and a VOR/ILS and yes CAT, no autopilot. Peanut is in the centre cluster and VOR/ILS on the bottom left of the dash board. Lousy scan and uncomfortable feeling when you think there may be something else a miss. But who knows, I wasn't there so I'll pass on making judgement on another crew.

[human garbage]

^ Same here. If they felt it was the way to go, then power to them.

I've had issues with a MEMS install in the past. Gotta hate the red 'X's. Not analogous to this situation obviously because of the level of backup instruments required. Sure they are all in funny places, but that was the only issue, a messed up scan. Back to the basics. I actually found it a bit nostalgic lol. I'm not that old, but the first bird I flew commercially didn't even have a DME (fixed card ADF to boot). I drove that sled to the seventh circle of Hell and back it seems sometimes. But I realize that what is comfortable to me might not suit someone else. I'll reserve judgement on the matter too.

[Meatservo]

To expand on my previous post, I guess what I was trying to say is that I wonder what the alternative option would have been here, other than what these guys did.

Surely, no-one is suggesting that when the main instruments stopped working, the crew, if they were "real" pilots from the good old days, should have said "hey-ho, there goes the AHARS, oh well, I guess we'll use the standby gyro and keep going to Rankin"

I think I would have turned back to Winnipeg myself. And so they declared an emergency... well that's kind of a personal decision isn't it? I mean maybe a "Pan" instead of a "mayday", from the comfort of my armchair I might concede that I suppose, I dunno. Seems like a pretty small detail to me. Certainly not enough to draw mockery...

I think if I was going to mock anyone, it would be whoever designed an aircraft attitude-indicating system that can get all fucked-up from a little shaking. I mean honestly. I've certainly no intention of ever flying a machine that has one of those randomly epileptic pieces of shit installed, now that I've heard about it.

[Cessna driver]

Ok so clearly there's a lot of misunderstanding of the G1000/ahrs around here.

First of all, with the G1000 installation, inverters are removed as they are unnecessary.

Second of all, the stand by instruments in these installations from what I have gathered, are a standby Attitude indicator, altimeter, and airspeed indicator.

The above is true, the instruments are fairly small, captain's side only


No nav instruments on standby


Well done to the crew

[xsbank]

Like I said, ignorance.

[Illya Kuryakin]

Who cruises a B200 at 1900 RPM? Your pax must love it
Illya

[leftoftrack]

Isn't 1900 RPM used for climb? It's been years since I've been in a 200

[Illya Kuryakin]

Isn't 1900 RPM used for climb? It's been years since I've been in a 200

Yup

[The De-Icer]

So can we not deduce from that, that maybe the plane was in the climb. Flight aware actually shows it if you look. 1900 rpm is the climb rpm in a king air. 1920-1960 is the "danger zone".

This is just my opinion, and dig away, but doesn't it seem a bit stupid that the aircraft is operated by the book at 1900 RPM in the climb but only 20RPM away from this "danger zone". I've got a couple thousand hours on the king air, and from my experience it doesn't take a long time for the props to diddle their way up into that range during the climb. The ahrs needs the props to be at that range for less than 30 seconds in order to fail.

Think about the last time you flew an airplane that you trusted. I've trusted many airplanes. Set the prop RPM in the climb (through 1000' normally) and never touched it until cruise - not because of laziness but because the props usually don't move more than 10-20 rpm. Now put yourself in a king air with three bladed props and a G1000 (Buddy tells me that it's the only plane in the fleet with both). Im not saying these guys were spot on, and flew perfectly by the book and didn't let the airplane get 20rpm high, but come on.... 20 RPM.

20 RPM... If there was a granite cloud there it could've been bad. Because of 20 RPM. Wtf is garmin doing. Garmin put a garbage Ahrs ... Er 2 garbage ahrs units into a $4 million airplane and expected nothing to happen. That seems fucked. Who gets shit on??.. The pilots. 2 pilots who are just trying to get back to rankin in one piece.

Now lets talk about what they do after the failure, and the units start coming back on line. Do you trust the equipment? You're IMC, at night, just trying to get to Winnipeg. Maybe it's just me, but anytime in my life when something has failed me, Im not going to be the first person to jump back in the trust wagon. How can you know it's working properly. Have you had a chance to check it?

Maybe someone has some more info on what happened that night, but let's not attack fellow pilots for taking a safe route to the ground when they had a pretty fucked up situation. (Not sure why everyone thinks they did, but Nope they would have no access to a VOR or ADF at the failure).

Love and tickles

[toelessjoe]

Jesus, tough crowd. Look, I've included a diagram that shows direct correlation between the AHRS and the propeller rpm. Instead of bickering maybe take a moment to edumacate yerselves!

- Toeless.

[Liquid Charlie]

Next stupid question looking at their destination - is this system certified in Northern Domestic airspace - many are not and the manual even gives the range in lat and long where it is not to be operated with the disclaimer that free gyro is only meant for operating in areas of local compass anomalies -- nothing to do with this incident and yes the crew acted correctly and maybe the training department is at fault if the restriction was unknown to them -- I know that when I found out a certain AHRS was restricted and not certified to operate in areas of compass unreliability it was through my own digging into the manuals I found it -- AC was based in Cam Bay -- go figure -- lmfoaaaaaaa

[AllClutch]

The G1000 upgrade at Keewatin was in the works for years, The hold up was waiting on a certified AHRS unit good for their range of operations.
I assure you that they wouldn't have moved forward with it unless they had found one.

[Liquid Charlie]

Maybe so but information on line seems to indicate all these issues and fixes with this particular unit has only been offered for about a year now at a cost of about 30 grand -- I know 7F struggled with this in their ATR's when first they started operations and the fix to their FMS system was about a mil/copy to fix - not saying this carrier didn't spend the money but it's only recently a reasonable cost fix has come available - my experience with smaller carriers is that they are not proactive for change for upgrades that are in an area where you can limp along without -- let's face it YRT operations can be safely done in magnetic -- as with my experience in Cam Bay - the manual didn't indicate the restrictions unless you found the operations manual supplement - only then was it written clearly - I'm not sure that operations even knew it since the unit was capable of free gyro operation -- it was all about money since an approved unit was at lease 4 or 5 times the cost --

At the end of the day if the crew had good knowledge could this not have been trouble shot in the air and maybe they could have carried on - still think maybe training was lacking -- did they find any fault with the system once they landed -- do there operate under SMS and if so what is the follow up -- if I was a king air driver I would like to have all these questions answered before I went blindly on -- as in a majority in incidents crew actions becomes the scape goat and the problem remains -- it would be nice to think this particular carrier is an exception but there are ones out there that are just plain "mickey mouse"

[xsbank]

I found the problem, thanks Toeless! The moral rectifier is directly connected to the magic smoke! No wonder the AHRS is squiffy.

Good post Charlie.

If these pilots had known about the moral rectifier (obviously a deficiency in their training) they could have carried on to their destination (insert name of Godforsaken Hellhole here - like Montreal) without any problem, simply operating their aircraft within its Limitations.

Limitations - "those things like little red lines that are on most of the gauges that tell you where you can and can't put the needles." All these things are in the POH in the chapter marked "Limitations" that are all supposed to be memorized by the pilots and are supposed to be tested every recurrent.

I'll bet Collins (or whomever made this device) sent along a nice thick, very nearly incomprehensible (Collins write them like that) manual that tells you all about their product, and I'll bet it has a revision page in it and a Limitations section and everything that you are supposed to know about AHRS.

The very least you can do is memorize the Limitations. Even if you suck at piloting, you should know how it all works.

Now any of you who are still reading might realize this transcends this BE20 thing. It comes down to getting promoted into a "modern" (sorta like a pig with lipstick) airplane and suddenly the rules change. You can't just kick the tires etc., you have to know the books. Those boring things we were forced to read in high school? Now you need to know all the stuff that's in there. All of it. You need to read the POH and QRH and the Collins book and the W&B and all the stuff that's on the shelf in the CP's office? YOU HAVE TO KNOW IT ALL. You can't fudge it like you can in a 1/2 hour checkout on a PA31. Suddenly, in a complex airplane, every Limitation is critical. If you want to end your career in a hurry or never get promoted again, you need to be an expert on all this stuff. The revenues lost, the equipment repair costs, the training costs, the capital acquisition cost, the insurance costs, even the fuel costs, make you the cheapest part in the airplane. That means you are expendable. That also means you have the total responsibility to operate this flying bag of cash and you'd better know everything you can about your ride.

Just keep repeating to yourself (after you reviewed some of the Memory Items in the QRH) "mortgage, marriage, kids." "Mortgage marriage kids."

Now get the books out tonight and read them before you have your first beer. Try a game called Stump the Captain and ask him about obscure weird facts that you found in your manuals.

Rant Switch........OFF

[flyinthebug]

Great rant xs!

I particularly agree with this part of your rant...in BOLD and underlined

The revenues lost, the equipment repair costs, the training costs, the capital acquisition cost, the insurance costs, even the fuel costs, make you the cheapest part in the airplane. That means you are expendable. That also means you have the total responsibility to operate this flying bag of cash and you'd better know everything you can about your ride.


Great advice! One of the better rants on here of late.

Fly safe all, and take xsbank`s advice. These things DO matter.

[xsbank]

I may not have practiced the Memory Items for any emergency for a while but I'm dripping with common sense and experience. I know that trying to pass that along here is like giving advice to a teenager, but even though we know the result, the parent in me keeps at it.

You up your game when you get to complex aircraft and some of the fun goes out of it because your performance is measured by a different rule. You have to be serious about it and you can't cheat, you have to do the work. There are lots of jobs out there flying simple aircraft so you can still go and do that.

Think about this - the AHRS on that King Air is probably worth more than the airframe.

[xsbank]

Hey Shimmy, we all have that, that's why we post here.

A lot of what we (Cat, Illya, myself, all the Crusties) say gets denigrated on here, yet we survived aviation. That means there was a lot of luck involved, but you have to admit we probably learned some stuff along the way. I was acquainted with about 10 pilots that died "doing what they loved" and I'm sure none of them went off to work thinking "today I'm going to die" or "today I'm going to kill a bunch of my passengers." Those 10 or so are not around anymore to be annoying on a website and tell us what got them.

Take what we say with a grain of salt, if you wish, but we survived aviation. I hope you can too. I'm being annoying so that maybe just one more of you guys will make a good career, be prosperous and come home after each trip, to your family.

I was a witness in a court case where the airplane disappeared. They found pilot error, even though they never found a rivet or the half dozen passengers. The pilot's estate was looted and his wife and three kids were left destitute. Fzck up at this job and your family pays in every sense.

One job I had, I spent lots of years intimately involved in teaching complex jet aircraft to pilots with every conceivable background and nationality. I know about how much work it is to stay in that part of aviation. I was also a QA pilot, which is where I got to polish my picky and perfectionist parts.

You need to be professional. You need to be at the top of your game always. You have people depending upon you for their lives, for their financial wellbeing. You cannot allow yourself to be complacent or crappy at any aspect of your job.

I got lucky. But, I survived aviation. I sincerely hope all of you will too.

Rant Switch.......OFF. I'm going to bed!

[Illya Kuryakin]

My definition of an idiot, is he who refuses to learn from the mistakes of those who went before him, and insists on making his own mistakes.
Not necessarily within this thread, but much good advice is give on this sight, and ignored by most, almost daily.
You've all been warned. Some of us have survived most mistakes one can make in this industry. Some probably have learned....many haven't.
Illya

[CID]

Garmin just recently came up with an arctic version of their AHRS that can be used on G1000 installations. It's a very good system with lots of redundancies but it's also very new so it's having a few teething problems. Things like vibration can cause "common mode" failures of systems that are otherwise independent.

If I was in an airplane with a brand-new EFIS installation and had experienced a dual AHRS failure en-route to a place in NDA, I think I would do exactly what the pilots did in this case. Anything else is just plain irresponsible. The problems with the new system in this case have nothing to do with how a pilot deals with a problem like this.

[CID]

By the way, most AHRS actually use strap-down mechanical gyros. Laser-Ring gyros are mostly used in IRS systems but there are a couple of AHRS that use them.

A strap-down gyro is different than a typical gimballed gyro in that its movement is restricted. Instead of measuring the displacement between the gyro and gimbal a measurement of the forces of the restricted gyros are taken. This force is proportional to the angular rate of change along the gyro's access.

Also keep in mind that the Garmin AHRS is slaved outside of NDA so the problem may be with the flux detector.

[Illya Kuryakin]

Garmin just recently came up with an arctic version of their AHRS that can be used on G1000 installations. It's a very good system with lots of redundancies but it's also very new so it's having a few teething problems. Things like vibration can cause "common mode" failures of systems that are otherwise independent.

If I was in an airplane with a brand-new EFIS installation and had experienced a dual AHRS failure en-route to a place in NDA, I think I would do exactly what the pilots did in this case. Anything else is just plain irresponsible. The problems with the new system in this case have nothing to do with how a pilot deals with a problem like this.

Make no mistake here. I'd have, for sure turned it around. Just may not have called it an emergency. An inconvenience, to be sure. I would NOT have continued all the way to Rankin Inlet with the problem.
Hope this clarifies it for everybody.
Illya

[rigpiggy]

I am fairly sure that the garmin uses "tuning forks" not gyros that sense acceleration by the change in frequency "doppler effect, they have 3 for the different planes run thru a mixer " computer" translating to a signal for the display. it is conceivable that the natural oscillation frequency had some resonant effects at the 1920-1960? rpm. Some light reading to the concept.

http://www.pprune.org/tech-log/print-33 ... -86-a.html
http://www.avweb.com/news/features/mems ... 787-1.html

http://evaluationengineering.com/articl ... course.php

[photofly]

Some rather heavier reading:
http://www.invensense.com/mems/gyro/doc ... 00v4_3.pdf

[Liquid Charlie]