[F1R]

Lets say we are on an IFR approach in icing conditions. The static ports ice over and block, perhaps the pitot also. Which of the current synthetic vision systems will continue to give us accurate GPS and gyro generated images of the terrain and runway regardless of the false airspeed and barometric altitude data?

I am new to the glass panel market and this weighs in my winter flying and purchasing plans.

 

[wildblue37]

From what I understand about glass cockpit devices, they have a "strapdown INS" which is augmented with pitot/static and GPS data. If the p/s system was lost then the airspeed and altimeter would read inaccurate. They wouldn't red-X (internal fail of the AHRS) but the software should figure out that inertial and GPS agree, and baro disagree and then rule it out. I've never tried this though and it's hard to simulate in real-life (you'd have to takeoff with the P/S system failed, you can't pull a breaker because that would red-X it and the sofware would know).

It's an interesting question though.

As a side-note, I had a friend who was flying in Kansas (land of high winds) doing slow-flight in a glass cockpit aircraft, and at the altitude he was flying the airspeed read 45kts and the groundspeed read zero! The attitude worked still but the heading was doing interesting things.

 

[Dynon]

The Dynon systems will continue to operate accurately in the described conditions.

 

[RV10inOz]

I had a piot blockage one day.....not from Ice, but from some very unlucky bug!

The Dynon reverts to a GPS input mode and it was spot on all the way home!

Good work Dynon


PS...I did toast his A$$ with the heater!

 

[Kevin Horton]

The Dynon systems will continue to operate accurately in the described conditions.

Will the synthetic vision give a correct view of the terrain if the barometric altitude is incorrect due to static system blockage?

 

[N131RV]

MGL Odyssey also works well

I have a couple of times lost my pitot readings (forgot to hook it up after maintenance).

The airspeed reads zero, but the artificial horizon and gps altitude continued to display correctly. It's a bit weird coming in for a landing with no airspeed.

 

[Dynon]

Kevin,
Synthetic Vision always uses GPS altitude as the reference. Since all the terrain data is on the same datum as the GPS signal, this gives you the right picture all the time. There's actually an FAA document saying that GPS altitude must always be used for SynVis references.

 

[Rainier Lamers]

MGL systems, to some extent allow the user to decide how they want this to operate.
You can choose which heading and altitude reference to use for synthetic vision as primary choice with fallback to another source if required.

Having said that, most would choose the GPS as primary source for both and pressure/compass based sources as secondary source if your GPS is u/s.

Personaly in my own aircraft I choose to use GPS as heading reference (effectively track, so what I see is where I am going, not where I am pointing). For the altitude I prefer the pressure based source as I find in our neck of the woods it tends to be a bit better than GPS based altitude which can be a bit of an issue if the satellite constelation is less than optimium. However, this is a bit old fashioned as the system can choose between the sources anyway based on an estimate of vertical accuracy which in turn is based on the current GPS quality.
This however is only possible if the internal GPS is used. If you are forced to use one of those old fashioned certified GPS systems via NMEA this automatic choice is not available.

Baseline to answer your question: I think you should not worry about this, modern EFIS systems here are as good as it gets.

Rather spend some extra effort in choosing a decent location for your GPS antenna...

Rainier
CEO MGL Avionics

 

[L.Adamson]

For the altitude I prefer the pressure based source as I find in our neck of the woods it tends to be a bit better than GPS based altitude which can be a bit of an issue if the satellite constelation is less than optimium.

Here, in the western USA, where at least one WAAS satellite is still functioning......

It's quite interesting how the GPS derived altimeter on my Garmin 696 panel page & the aircraft's altimeter will exactly follow each other, when I get a current altimeter setting from XM satellite weather.

L.Adamson --- RV6A

 

[breister]

Lets say we are on an IFR approach in icing conditions. The static ports ice over and block, perhaps the pitot also. Which of the current synthetic vision systems will continue to give us accurate GPS and gyro generated images of the terrain and runway regardless of the false airspeed and barometric altitude data?

I am new to the glass panel market and this weighs in my winter flying and purchasing plans.

It's a very good idea to plumb in an Alternate Static valve (just dumps the system to cockpit air). Your altimeter may then be off a bit, but should be close enough for safety.

As others have said, virtually all of the EFIS units now "failover" to GPS assist if airspeed and altimeter fail. What may be different is the formula they use to recognize a failure situation.

 

[Rainier Lamers]

As others have said, virtually all of the EFIS units now "failover" to GPS assist if airspeed and altimeter fail. What may be different is the formula they use to recognize a failure situation.

There is one more thing to consider:
Not all AHRS systems need aiding.

a) Some do not need ANY aiding.
b) Some will use aiding in some circumstances but work fine without (perhaps with reduced but still adequate performance).
c) Some don't work without aiding.

Ours would fall into categories (a) or (b) depending on model.

There are also several categories on how aiding works so vendor "A" might do completely different aiding to vendor "B" - but don't get me started on that unless you have a lot of time...

Rainier
CEO MGL Avionics

 

[pierre smith]

Believe it or not....

....the Airbus A321 that I flew on from California didn't have any round steam gauge backups! I had struck up a conversation with the crew before the flight and they invited me to the cabin before departure.

Each pilot has two screens, one a PFD and the other a nav/traffic screen and either screen can become the PFD if the other goes TU....4 screens.

The capt. pointed to the third backup screen....looked just like the new TruTrak Gemini, 3 1/8" with AH and airspeed on the left and altitude on the right.

Best,

 

[penguin]

And the back-up screen costs $40K!! I couldn't believe it either when I heard how much ...

Pete

 

[F1R]

Static valve

Any ideas for an alternate static valve in the panel, fuel console or elsewhere with quick access without undoing my belt to reach. Photos or links would be great.

Thanks in advance.
Richard

 

[KRviator]

Any ideas for an alternate static valve in the panel, fuel console or elsewhere with quick access without undoing my belt to reach. Photos or links would be great.

Thanks in advance.
Richard

Stein (as always) sells a beautiful "switch" made just for this purpose. I've seen a similar switch in some online cataloge, but he sell's it, and he's a VAF'er, so why not give him the $15.00 for one?

Alternate Static Air Toggle Valve/Switch. Mates with optional P-512 adapter (available for purchase separately). Mounts in a standard .460" hole (same as standard toggle switches). Simply hook this into your static system and flip the valve for alternate air supply.

I'm sure he won't mind me pinching his photo either..

 

[gasman]

Personally in my own aircraft I choose to use GPS as heading reference (effectively track, so what I see is where I am going, not where I am pointing).

Rainier
CEO MGL Avionics

With my XTreme, I expected to see a track tape at the top of the screen if I did not have the compass option.
But you did not give us the GPS track.

Will this be something that we can get in the next upgrade? It is the ONLY thing that I really miss in the basic unit............

 

[Bavafa]

Stein (as always) sells a beautiful "switch" made just for this purpose. I've seen a similar switch in some online cataloge, but he sell's it, and he's a VAF'er, so why not give him the $15.00 for one?



I'm sure he won't mind me pinching his photo either..

I have got one of these and it was leaking like crazy under vacum pressure so my static test would not have passed. It works great under positive pressue which is not the case for static.

I think I may get another one from Stein just in case mine was faulty.

 

[777drvr]

With my XTreme, I expected to see a track tape at the top of the screen if I did not have the compass option.
But you did not give us the GPS track.

Will this be something that we can get in the next upgrade? It is the ONLY thing that I really miss in the basic unit............

I second that !

Marc

 

[KRviator]

I have got one of these and it was leaking like crazy under vacum pressure so my static test would not have passed. It works great under positive pressue which is not the case for static.

I think I may get another one from Stein just in case mine was faulty.

I'm curious as to why a static system is pulling a vacuum? If it's under negative pressure, isn't it going to indicate an altitude higher than you're actually at?

Without having seen the switch in person, if there are two ports on it, could you swap the ports around so it's pulling a vacuum in the opposite direction?

 

[flion]

A static test is done under a vacuum, mostly. Here at 7k, the tech pumped up my system to get below sea level but once he passed field elevation it was vacuum all the way up to 30k. Under operating conditions, I'd expect the pressure on both sides of the switch to be nearly equal, so I'd expect it to work Ok if it held pressure for a reasonable differential. But I'm not sure it'd be kosher to block the switch for the test; it's probably best to try to get a non-leaky switch. Anyway, I hope that clears up the vacuum question.