akschu

akschu

Well Known Member
Patron
Forum,

I am spec'ing out my panel trying to figure out what I'm going to do but I'm concerned about cold weather operation. I live in Alaska so my airplane (no, sorry, it's not an RV) will get subject to -20F occasionally. I would like to run glass because it's lighter (if you don't go overboard), takes up less room in the panel, and because it's more modern.

After seeing everything at oshkosh last year I was most impressed with MGL avionics. Many other vendors where there but the EFIS they where selling seemed smaller, more expensive, and MUCH less flexible.

I posted to the MGL list and someone said they cold soaked it to -10F and it seemed to work fine, but Rainier mentioned that extreme temperature ranges where hard on electronics and will cut down on the life span of the EFIS.

I'm now reading the MGL documentation and Rainier makes several points about the AHRS system being effected by temp because the gyros where temp sensitive. In fact the SP-5 system they sell has a heater in it to try and normalize the temp.

So my questions are:

1. Anyone else out there running any EFIS is real cold? What is your experience?
2. How much will cold hurt my reliability?
3. Do any of the EFIS manufacturers specifically address cold weather operation in any of their products?

It's not -20F every day or anything, I suspect that it will only see those temps operating a few times a year, the rest of the time it will warm up and cool down with the weather which is quite gradual.

Anyway, just looking for thoughts on this. I would like to avoid steam gages, but not if they are more reliable.

Thanks,
schu
 
Schu,

My Dynon D100 has run in the cold and seems to do so without trouble. I guess my major feedback to your questions would be that you're going to use pre-heat on your engine, so why not send a blast of warm air into the cockpit, too, so you don't stick to metal parts when you touch them?

My experience as an avionics manufacturer's tech rep taught me an important lesson. When it's that cold you can expect the electronics to power up, but you can also expect things like mechanical gyros to make some very weird sounds as they attempt to overcome the "stick-shun" in their bearings etc. In fact, even though the electronics will spark up you'll need to be careful with things like canopy latches etc as they will become fragile in the cold.

Bottom line is that if you've got enough heat available to get your engine cranked up then you've also got enough heat to bring the cockpit up a few degrees and make your avionics life a bit easier, whether those avionics be electronic or steam gauge.
 
I am an electrical engineer who worked on the development of the EFIS system for the Boeing 777.

As long as the EFIS system developer selected components that are specified for operation down to -40C, cold temperature should not result in a catastrophic failure or reliability degradation. In fact, most electronic components work better and last longer in cold temperatures.

The biggest issues that LCD based EFIS systems face in cold temperature operation are:

The Liquid Crystal material becomes sluggish and the response time of the display is much slower. This can result in smearing or fading of dynamic symbology. These problems go away when the display warms back up. The type of liquid crystal material that is used in the display plays a big role in how low of a temperature a given display can operate without smearing. Well designed systems include an ITO heater that heats the display glass in cold ambients to keep the LC material within its normal operating range.

Fluorescent backlights will dim or they may not light up at all or flicker in cold temperatures. The dimming is caused by the fact that fluorescent lamps operated at maximum efficiency when the coldest spot on the lamp is around 60C, and lose efficiency dramatically at low temperatures. This is because the mercury vapor pressure is governed by the coldest spot on the lamp wall where liquid mercury will pool. Well designed systems wrap the fluorescent lamps with heater wire to heat them in cold ambients. LED backlights are superior to fluorescent backlights because they don't have problems in cold temperature, and can be dimmed down to lower levels without flicker or uniformity problems that fluorescent lamps tend to exhibit when they are dimmed.

I wouldn't buy an EFIS from anyone who hasn't done operating temperatures testing down to -40C.

Dean Wilkinson
AeroLEDs LLC
http://www.aeroleds.com
 
temp specs

Don't know about cold, but my early D10a gets out of spec temps when my bird is sitting in the hanger this time of year.

Miller McPherson
RV-6, 900+ hours.
Cascabel, AZ
 
I wouldn't buy an EFIS from anyone who hasn't done operating temperatures testing down to -40C.
Click to expand...

I don't know of anyone who has, nobody mentions it in their documentation..... except for the big names like Garmin, but I can't afford their stuff.

schu
 
We have multiple temp chambers at Dynon that go to -70C and we test all of our products at -40C. We then spec them -30C to +50C (-22F to 122F) or greater. Temp specs (and other specs) are on the last page of all our install guides.

In AZ in the summer, the inside of a plane can get to over 122F. Which is why we warn you when it's too hot. Technically, this is a warning that our calibration may be suspect at these temperatures, not that the unit is being damaged. Of course, remember that all our avionics are this hot too, so just because we're warning you doesn't mean we're more sensitive to it- we're just telling you, which most avionics don't do.

Visit our forum and you'll see quite a few people that use them in MN or AK with no problems.
 
My Dynon here in good ole' MinnesOta works pretty good most of the year. That being said, below about -15F it's not very happy (but honestly most of the EFISes are not happy there). Once it gets close to zero it works great. I've seen more problems with EFISes that get hot then get cold (including my Dynon getting a little ill sitting in hot sunshine)...but like I said it's not really unique to them.

Most all of the lower cost EFISes and other displays that we use are not going to love the extreme edges of the envelope when it comes to heat. The high end (read high $$ stuff) has onboard heaters for their AHRS, and the raw components are just different. But, that's the difference between a $40K EFIS and a $4K EFIS.

Overall I think you'll happy with most of them out there for the most part. Don't be surprised if they are slow to wake up at -20F! I wouldn't worry too much about it.

Cheers,
Stein
 
SteinAir said:
Most all of the lower cost EFISes and other displays that we use are not going to love the extreme edges of the envelope when it comes to heat. The high end (read high $$ stuff) has onboard heaters for their AHRS, and the raw components are just different. But, that's the difference between a $40K EFIS and a $4K EFIS.

Overall I think you'll happy with most of them out there for the most part. Don't be surprised if they are slow to wake up at -20F! I wouldn't worry too much about it.

Cheers,
Stein
Click to expand...

Yes, you are correct Stein (as I would expect).
However, if you look at our SP-4 AHRS which is clearly on the bottom side of the cost envelope, even there we have a built in heater. It just makes sense and to put a heater in has huge advantages. This does not eliminate temperature compensation and calibration but aids it in a big way.

Regarding the comments on LCD displays, our Odyssey and Voyager are specified for operation at -30 degrees Celsius which is -22 Fahrenheit. Note that this is operation, not storage temp which is an entirely different thing.
This is a pretty low temperature for any LCD display, in particular for a large panel display where temperature effects can be more severe (try this on your large screen laptop to see what I am talking about).
It is interesting to note that most modern high brightness displays have built in parasitic heating (due to heat created by the backlight system) so low temperature operation is only required for a very short time before the panel has a more acceptable operating temperature (a minute or two is usually quite enough). The same heat source (and a few others) will aid the rest of the EFIS electronics as well.

Regarding comments made about components rated to -40 degrees C being more resistant to temperature extremes I have to add that in my experience this is generally not the case (I designed and maintained electronics that was used at the South Pole, gets pretty nippy there - I can tell !).
What kills electronics (and a lot of mechanics) are temperature CHANGES, not so much absolute temperature for any duration.
This is why expensive LCD panels are specified to survive a certain number of temperature cycles with given limits and times. These would be the panels most EFIS manufacturers would be using.
I'll put my reputation on the line with the statement: "No LCD panel thus far created will survive an **indefinite** number of **large** temperature cycles".
If this sounds like a strange statement coming from somebody that makes EFIS systems - well, it's the truth...
Should you worry ? No. You have a few things up front under your bonnet that are way more critical and likely to fail than your LCD screen. Worry about those first.

Rainier
CEO MGL Avionics
 
"Regarding comments made about components rated to -40 degrees C being more resistant to temperature extremes I have to add that in my experience this is generally not the case (I designed and maintained electronics that was used at the South Pole, gets pretty nippy there - I can tell !).
What kills electronics (and a lot of mechanics) are temperature CHANGES, not so much absolute temperature for any duration.
This is why expensive LCD panels are specified to survive a certain number of temperature cycles with given limits and times. These would be the panels most EFIS manufacturers would be using."

I was addressing the specific question about low temperature operation, not thermal cycling. Clearly temperature cycling is one of the biggest stressor of electronics. Solder joints and interconnects are particularly suscpetible to thermal cycling. LCD panels have high density interconnects that are vulnerable to failures if the display isn't designed for the environment and mounted correctly in the housing.

Dean Wilkinson
 
Dean_aeroleds;240582[INDENT said:
]
I was addressing the specific question about low temperature operation, not thermal cycling. Clearly temperature cycling is one of the biggest stressor of electronics. Solder joints and interconnects are particularly suscpetible to thermal cycling. LCD panels have high density interconnects that are vulnerable to failures if the display isn't designed for the environment and mounted correctly in the housing.

Dean Wilkinson
Click to expand...

Yes Dean, I concure.
Temperature related failures on LCD displays come mainly in two forms according to our now very considerable experience with these things (some 20.000 LCD based avionics systems made and shipped to all parts of the World - desert to arctic).

1) Bonding failure of connection to LCD glass. This has improved in the past years due to better manufacturing processes.
2) Failure of the active compronent of a TFT display pixel. The active components that control each pixel (actually three per pixel, one for each primary color) are grown directly on the glass surface including the tracks that supply signals/power. The tracks are very thin (often made from gold) and can rupture. The TFT components fail due to loss of bonding or corrosive effects (oxygen inclusions in fluid etc).

Bonding failure to the glass tends to show itself in horizontal or vertical rows failing. TFT failures show up as pixels that are permanentely on or off. Many TFT panels ship from the manufacturers with a certain amount of these pixel failures as "acceptable". LCD OEMs like us weed them out and end up with a small mountain of brand new LCD displays we can't sell. We tend to donate them to universities etc. About 5% of LCD panels we buy end up on the heap like this.

A small amount of traditional electronics also forms part of the LCD display and comes in various forms (COG, COP etc). This may fail as well but is getting quite rare.

Rainier
 
N941WR said:
Stein,

Don't y'all get the Weather Channel up there? Don't y'all know there are better places to live?
Click to expand...

You said it !

Rainier
(Typing this in a wall to wall blue sky Cape Town in the middle of winter at around 22 degrees C. It does rain sometime this time of year but not today !)
 
I'll take cold and stunning beauty over people and politics any day of the week.

Here is a picture I took last week:

main.php


Certainly the camera doesn't do it justice, and frankly this scene is so common that that it's nothing special.

Besides, it's colder in MinnOsoDa.

schu
 
I thought I was inverted at first, but a quick look at the mountains and a confirmation glance at the attitude indicator revealed that I was indeed right side up ;)
 
You must log in or register to reply here.