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IMC - What If??? Analysis

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Paul Valovich

Joined: 11 Jan 2006
Posts: 75

Posted: Wed Sep 24, 2008 7:37 am Post subject: IMC - What If??? Analysis

FWIW – I spent a lot of time analyzing panel options for my -8A, and so far have found no major issues with the conclusions I reached. Here’s a summary:  

   

Requirement 1: IMC capability (if I choose to go there) – including ILS.  (Pilot instrument experience not an issue – I’m a retired Naval aviator).  

Requirement 2: Electric panel – no vacuum pumps.  

Requirement 3: Multiple redundancy – fidelity can vary.  

   

Final instrument configuration: AFS-3500 with AOA; TruTrac ADI II; Sl 40;  Garmin 496; ICOM Radio; GTX-327; PMA-7000B; Separate altimeter, airspeed, VSI; Heated pitot tube.  

   

Electrical System: B&C 40 amp alternator; SD-8 alternator; self-contained backup batteries in 3500 and 496; regular ship’s battery.  

   

In IMC - What ifs? (Normal ops – everything works and power is from main bus)  

   

<![if !supportLists]>1.       <![endif]>AFS-3500 failure – use ADI II for attitude info; if unsure of attitude, select a heading and altitude hold mode. Use AS / Altimeter / VSI steam gages.  

<![if !supportLists]>2.       <![endif]>AFS-3500 and ADI II failure – use rough attitude functions of 496 to get back to approximate level flight (a real emergency)  

<![if !supportLists]>3.       <![endif]>AFS-3500, ADI II and 496 failure – partial panel with the AS / Alt and VSI; but realistically, sometimes it just ain’t your day.  

<![if !supportLists]>4.       <![endif]>Alternator failure – endurance bus powered by SD-8 (3500, SL-40, ADI II are on it)  

<![if !supportLists]>5.       <![endif]>Alternator and SD-8 failure – endurance bus powered by main battery  

<![if !supportLists]>6.       <![endif]>Alternator, SD-8 and main battery failure – 3500 and 496 powered by internal backup batteries  

<![if !supportLists]>7.       <![endif]>Alternator, SD-8, main battery and backup battery failures – see (3) above  

<![if !supportLists]>8.       <![endif]>Pitot static failure – 496  and AOA attitude reference (if AOA is below stall you are at least somewhat in control and may have additional time to sort things out)  

<![if !supportLists]>9.       <![endif]>Icing – Get the hell out of there asap  

   

Panel configuration is a very personal decision. However, some version of the “What ifs???” should be used in every analysis. The above is just one guy’s opinion. Be interested in hearing from folks who think I’m off on a tangent or missed something.  

Booger  

N192NM Reserved - Again  

   

   

   

   

   

   

   

   

   

      [quote][b]

Bruce(at)glasair.org
Guest

Posted: Wed Sep 24, 2008 1:50 pm Post subject: IMC - What If??? Analysis

To play the  devils advocate,

  

 You'll be  lucky if, when your EFIS fails, the screen goes dark. More than likely, part of  it will just freeze, or worse yet - start giving you false  information.

  

 What do you  do when all your electro-wizzies fail? It's happened - several times in big iron  aircraft, failure of multiple electrical systems and their backups leaving a  totally dark cockpit. One of the reasons that all EFIS certified  panels have a vacuum ADI or equivalent.

  

 But let's  look at a more likely failure mode, the AHRS starts to put out false  information. Your Tru-Trak ADI (It's not really) only displays quasi pitch info.  It shows a GPS derived VSI as pitch up/down commands. Now, the big question is -  are you willing to bet your life that you addled and confused brain is going to  be able to sort out the conflicting and non standard pitch information before  you go "THUD"?

 And as your  screaming brain is yelling - which system is right? Needle, ball, and airspeed  tie breaker?

  

 I know I've  spent hundreds of hours scanning the basic 6 pack in IMC and am well aware of  its failure modes. But when screens go dark or scrambled it's the easiest and  fasted for me to revert to and feel comfortable.

  

  

  

  

Bruce 

www.Glasair.org 

 

 [quote]   

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stein(at)steinair.com
Guest

Posted: Wed Sep 24, 2008 2:22 pm Post subject: IMC - What If??? Analysis

Hi  Bruce,

  

 You  know I agree with you historically on some of your points, but I have to jump in  here just a little bit - nothing personal, just want to re-direct a few  facts.  Your understanding of the TruTrak ADI is not just a little bit  off....it's just flat wrong.  Who told you it uses GPS information for  vertical information?  They use GPS to show a track in the little LCD  window...it has nothing to do with the flight display. You do of course realize  that it has solid state gyros inside of it and shows instantaneous pitch and  bank information as well?  Naturally you also know that it has a Pitot  and Static connection on the back of it to sense pitot/satic  info?  Of course some of the EFIS mfgrs out there use GPS as an aiding  function to offset the accelerometer drift, etc.., but I'm not aware of any  other than the little "instrument page" of the Garmin handhelds that do anything  of the sort.

  

 Anyway, I don't want to get into a debate on what should be used when and  where nor if the ADI is for you or not...just want to make sure people don't  think it uses GPS to display any flight information.  I do agree that there  is a BIG question on lower cost EFISes knowing whether they are ill or  not.  The certified stuff has a ton of software in it for that very  purpose, and will paint a big red "X" over any portion of the instrument it  thinks doesn't has perfect information.  Most of the really low cost EFISes  will not alert you to anything being wrong, because the EFIS itself doesn't know  it's sick.  It's what I try to tell people over and over.  There  is a MUCH larger difference between EFISes than just plain cost.  There is  a lot of other unseen functionality that comes with the higher priced units  other than their name on the faceplate.  Of course every EFIS mfgr will  tell you their stuff is the same as the certified Garmin or what is in the  Boeings while standing in the booth at OSH (I actually heard a rep from a low  cost EFIS mfgr repeatedly tell people their stuff was as good or better than the  Garmin certified stuff)....hopefully people realize that's just not the case and  couldn't be farther from the truth.  Does that mean the low cost EFISes are  bad?  Heck no!  They are a marvel of technology as long as you use  them for what they are.

  

 FYI...most of the heavy iron is going to solid state peanut backups as  well....but they aren't anything like our low cost EFISes (nor the  price)!

  

 Again,  nothing personal and I'm not necessarily disagreeing with premise in  general, just some of the details.  The whole "tie breaker" discussion gets  really interesting really fast in some of these configurations.  There are  a number of historical crashes of airliners because of the fight between  pilot/copilot and the "tie breaker" of instruments indications. Overall I could  ramble on and on about this stuff, as well as the whole AHRS theory, but in the  end we're all entitled to our own opinions.  Like I said, no necessarily  agreeing or disagreeing, just putting out a few facts.

  

 Cheers,

 Stein

 [quote]   --

Bruce(at)glasair.org
Guest

Posted: Wed Sep 24, 2008 3:05 pm Post subject: IMC - What If??? Analysis

Hmmm, I could  be wrong but.... The TruTrak website says the roll is instantaneous gyro and the  pitch is enhanced VSI. Perhaps we're both right.

  

  

  

Bruce 

www.Glasair.org 

 

 [quote]   

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khorton01(at)rogers.com
Guest

Posted: Wed Sep 24, 2008 11:45 pm Post subject: IMC - What If??? Analysis

As I understand it, this means that the pitch info comes from changes in 

barometric altitude (i.e. VSI), enhanced with solid state pitch rate 

"gyro" info.  No GPS info is used for pitch or roll display.



Kevin Horton



Bruce Gray wrote:

[quote] Hmmm, I could be wrong but.... The TruTrak website says the roll is

 instantaneous gyro and the pitch is enhanced VSI. Perhaps we're both right.

  

  



 Bruce



  <http://www.glasair.org/> www.Glasair.org



  



 --

rv8tor(at)lazy8.net
Guest

Posted: Thu Sep 25, 2008 3:55 am Post subject: IMC - What If??? Analysis

The basic ADI (not with built in autopilot option) has a single gyro (solid

state rate gyro), inclined like the one in a turn coordinator. This means

the gyro itself senses both roll and azimuth changes (not position,

changes). 



It also has pitot and static pressure inputs.



For vertical display, it is an IVSI, an instantaneous vertical speed

indicator, so it does not have the lag that a basic VSI has. This is a

common mechanical instrument, often used in gliders and seaplanes.



For bank angle information, it uses the turn rate info from the gyro, and

combines that with the speed info from the pitot input to calculate and

display bank angle. This is the basic patent that TT brags about.



John



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Bruce(at)glasair.org
Guest

Posted: Thu Sep 25, 2008 10:12 am Post subject: IMC - What If??? Analysis

So, that means that there are some situations where the aircraft could be at

reduced power, level in pitch, in a decent, and the instrument would show

nose down causing the pilot to pitch up and stall the aircraft.



Bruce

www.Glasair.org

 

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rv8tor(at)lazy8.net
Guest

Posted: Thu Sep 25, 2008 10:34 am Post subject: IMC - What If??? Analysis

Bruce, you and I have been on these lists for at least 10 years now.



As you well know, this subject has been beaten into the ground.



Yes, if you are IFR, and you fixate on one instrument, there are many

different ways you can get in trouble. If you are going to fixate on a TT

ADI, to the exclusion of the airspeed indicator, you can get yourself into

the situation you describe.



I do have a TT ADI in my RV8. As an old CFII, I have been trained to fly

partial panel. I would far rather do it with an ADI and airspeed, than the

old needle, ball, and airspeed.



John

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Bruce(at)glasair.org
Guest

Posted: Thu Sep 25, 2008 10:50 am Post subject: IMC - What If??? Analysis

OK, I'll stop. It's just that if it looks like an attitude gyro, unfamilure

pilots are going to try to fly it like one. I'm sure that if TruTrak tried

to certify that instrument, the FAA would require a "No Pitch Information"

placard.



Bruce

www.Glasair.org

 

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stein(at)steinair.com
Guest

Posted: Thu Sep 25, 2008 10:55 am Post subject: IMC - What If??? Analysis

Bruce,



Now you're assuming someone will ignore the rest of the IFR scan - and not

pay attention to airspeed.  If you're going to compare IMC apples to apples,

you can't use the entire scan for one objective review (your favorite old

Vac based gyro) and ignore it for the rest.  Why would you randomly pull the

nose up at slow speed, reduced power in a descent?



I take it you haven't flown behind the instrument you're opining on

here.....



I know new things can be a bit scary, especially if you don't have first

hand knowledge of how they work.  It'd be like me talking about how

Glasair's are to build or fly, when of course I haven't built one.  It's

often the case with the ADI that pilots who haven't flown behind it or

understand it will have negative opinions about it, but I think youll find

that it's probably much better than you give it credit for once you actually

get some time behind one.



Again, nothing personal, but if you're going to compare apples to apples

then the entire scenario needs to be kept with the same comparisions/delta

between them.  You can't throw out part of the information that you'd

normally use behind a gyro just to try and make the ADI look bad because you

personally don't happen to like it or fly behind it.



In the end, there is no doubt that Vacuum based gyros for the most parts

have and are going the way of the dinosaurs.  You can either learn to adopt

to the new technology or not, but the world is going that way whether you

personally like it or not.



Cheers,

Stein



[quote]--

rv8tor(at)lazy8.net
Guest

Posted: Thu Sep 25, 2008 11:12 am Post subject: IMC - What If??? Analysis

That could be...it does work in a different way, and require a little bit of

re-education. It is a little like the change from the turn and bank

indicator to the turn coordinator, though more so, maybe.



I found it interesting to read that the attitude indicator in an SR-71 also

shows vertical speed rather than pitch...I guess a one-degree pitch up at

SR-71 speed would be extreme for altitude correction...same problem I have

at RV8 speeds )



John

--

Bruce(at)glasair.org
Guest

Posted: Thu Sep 25, 2008 11:26 am Post subject: IMC - What If??? Analysis

Well Stein, I'm certantly no Luddite, I even have a EHSI (Sandel 3500) on my

panel and a pair of those new fangled Garmin GPS thingies.



As I'm sure you know, from my previous posts, I'm NOT a fan of low cost

non-TSO'd EFIS systems. Even some of the low cost certified ones set my

teeth on edge. I'll just keep on spouting my mouth in hope that some of my

words will keep one of my brethern from an early grave.



For those that don't know, my rules for an EFIS panel are;



DO-178 certified software.



Dual independent AHRS with a cross comparator alarm system and an

independent third gyro attitude system as a tie breaker. Expensive - yep,

but it will keep you around to pay it off.



I sure hope we can keep this friendly, I'd hate to throw away my Stein-Air

tee shirt.



Bruce

www.Glasair.org

 

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RobHickman(at)AOL.COM
Guest

Posted: Thu Sep 25, 2008 1:50 pm Post subject: IMC - What If??? Analysis

The Cirrus SR-22  has a mechanical Airspeed indicator, Altimeter and an ELECTRIC artificial  horizon as the backup instruments.  The Cirrus also has two alternators and  a dual buss electrical system.  The Cirrus does not have any vacuum backup  instruments, however it does have a parachute as the ultimate backup and it has  been used after the screens went black.  

  

In my RV-10 I have two  Advanced deck EFIS units, each with their own AHRS and air data, Digiflight II  VSGV Autopilot, Garmin 496 (with GPS based instrument page) and a wet compass.   

Unlike the Garmin G900  system, each AFS screen has an internal battery that will power the EFIS  independently for over an hour in the event of an electrical failure in the  aircraft.  The AFS EFIS setup in my RV-10 has dual AHRS, airspeed and  altimeters for cross checking between screens as a measure of added safety. The  G900 is a single AHRS and airdata system. 

Like the Garmin G900,  the AFS AHRS and its companion Remote Magnetometer are built in an FAA MIDO  approved manufacturing facility, where automated state-of-the-art dual-axis  ovenized rate tables ($250,000 each), thermal chambers and Helmholtz cages  perform extensive calibration, test and 100% verification of performance and  reliability prior to being incorporated into the EFIS.  

The AHRS-Magnetometer  has three separate microprocessors that calculate and verify proper operation  with built-in test functions.  If the AHRS built in test routine detects an  error, the EFIS will display a large red X on the screen and can switch to  another AHRS.   If the EFISâ€™s CPU detects a cross compare error  between screens a warning is generated and the pilot is able to select the AHRS  to use. 

AFS has extensive  experience writing certified software to DO-178. AFS is responsible for the  software development for the new Honeywell KFD-840 EFIS. 

In my RV-10 I have the  following failure modes: 

1.     Aircraft Electrical  System Failure 

Use Internal EFIS  batteries and Garmin 496 connected to EFIS for navigation.   Select  closest airport, should have over an hour of backup time. 

  

2.     Single AHRS detected  failure

EFIS screens will switch to second  AHRS          

3.     EFIS cross compare  error

Use Autopilot, GPS, and Compass to select AHRS to  use.

  

4.     EFIS screen  failure 

Use second EFIS and  Autopilot. 

  

5.     Dual EFIS screen  failure 

Use Autopilot, 496 GPS,  and Compass for navigation.  I have actually practiced this under the  hood.  Just last week my instructor made me fly an approach under the hood  using only the 496. 

The lack of proper  training, little or no recurrent training and poor judgment are the real safety  problems not the EFIS.  Statistically the component that is most likely to  fail is between the pilotâ€™s ears.  Anyone flying IFR needs to be trained  and proficient at recognizing a failure and being able to fly the aircraft  without it.   

Anyone that truly  believes that they are safer flying a standard â€œ6 packâ€ with a single vacuum  pump IFR rather than my RV-10 panel setup needs to check the ventilation while  being exposed to fiberglass fumes. 

Rob Hickman 

Advanced Flight  Systems 

 



Looking for simple solutions to your real-life f9382257x1200540686/aol?redir=http://www.walletpop.com/?NCID=emlcntuswall686/aol?redir=http://www.walletpop.com/?NCID=emlcntuswall00000001" target="_blank">Check out WalletPop for the latest news and information, tips and calculators.

  [quote][b]

Bruce(at)glasair.org
Guest

Posted: Thu Sep 25, 2008 2:18 pm Post subject: IMC - What If??? Analysis

I'm really not high on fiberglass fumes.  It's the vynalester resin fumes that will make you feel good  though....

  

 What's gonna happen when you're up there and  a lighting bolt strikes your RV and fries all your electrical  systems?

  

 Guys... I'm not against EFIS systems or you  desire to fly behind them. I just want everyone to realize what risks they are  taking.

  

 Although we are getting down to unlikely  situations here.

  

  

  

Bruce 

www.Glasair.org 

 

 [quote]   

   --

RobHickman(at)aol.com
Guest

Posted: Thu Sep 25, 2008 4:03 pm Post subject: IMC - What If??? Analysis

In a message dated 9/25/2008 3:20:39 P.M. Pacific Daylight Time,  Bruce(at)glasair.org writes:

  	  Quote: 	
		  What's gonna happen when you're up there and a    lighting bolt strikes your RV and fries all your electrical    systems? 	


 

  

Without  ground straps on your control surfaces and static wicks your electronics  could be the least of your problems.  

  

Actually  we spent a lot of time with the help of Crossbow designing in lightning  protection on the electrical connections that wire to the EFIS. Crossbow has  extensive experience with passing the lightning protection requirements for  certification.  We have not actually  done lightning verification testing of our EFIS or the RV-10. 

  

 From  http://www.lightningtech.com/d~ta/faq1.html 

  

The  last confirmed civilian plane crash that was directly attributed to lightning in  the U.S. was in 1967, when lightning caused a catastrophic fuel tank explosion.   

  

Most  aircraft skins are made primarily of aluminum, which is a very good conductor of  electricity. By making sure that there are no gaps in this conductive path, the  engineer can assure that most of the lightning current will remain on the  exterior skin of the aircraft. Some modern aircraft are made of advanced  composite materials, which by themselves are significantly less conductive than  aluminum. In this case, the composites should be made with an embedded  layer of conductive fibers or screens designed to carry lightning currents.   

  

Looks  to me like Bruce could have more problems than we do with this one,  even  without an EFIS  

  

Rob  Hickman 

Advanced  Flight Systems



Looking for simple solutions to your real-life financial challenges? Check out WalletPop for the latest news and information, tips and calculators.

  [quote][b]

rv8a2001(at)yahoo.com
Guest

Posted: Thu Sep 25, 2008 5:17 pm Post subject: IMC - What If??? Analysis

Now to stir the pot..............



You can protect electrical systems with TVS diodes. 



http://en.wikipedia.org/wiki/Transient_voltage_suppression_diode



And yes I have read that they can be used for lightening strikes and are on communication equipment.

 

Scott 





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