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Synthetic Vision options, and marginal IFR

FAA proposes lower minima for SV equipped aircraft

here

This probably does not apply to aircraft in European airspace, however.

Administrator
Shoreham EGKA, United Kingdom

You title is rather misleading. It should be "FAA proposes lower minima for SV equipped aircraft". The corresponding rule making task at EASA looking more generally at all weather operations is scheduled to start next year.

It is also misleading because it doesn't have anything to do with Synthetic Vision ie the product on Garmin and some other PFDs. It refers to HUD showing FLIR, Radar or Low light intesified vision. Very different.

Enhanced flight vision system (EFVS) means an installed aircraft system which uses an electronic means to provide a display of the forward external scene topography (the applicable natural or manmade features of a place or region especially in a way to show their relative positions and elevation) through the use of imaging sensors, such as forward-looking infrared, millimeter wave radiometry, millimeter wave radar, or low-light level image intensification. The EFVS sensor imagery and required aircraft flight information and flight symbology is displayed on a head-up display, or an equivalent display, so that the imagery and symbology is clearly visible to the pilot flying in his or her normal position with the line of vision looking forward along the flight path.

EGTK Oxford

I actually think that SV is a bit of a problem during the final approach. You have a very tempting runway to fly to, but are supposed to follow the HSI and glideslope... And SV does not get turned off when you lose Raim or WAAS.

It is a fantastic safety tool in mountainous terrain, though!

Biggin Hill

In another thread, two pilots mentioned the “comfort” they get from seeing the runway on the PFD when flying approaches to minimum in marginal conditions.

For those not familiar – “Synthetic Vision”/SVT is a computer generated terrain and runway image based on the database, GPS position, and aircraft attitude, and is quite accurate and realistic in its depiction if the runway, if a bit generic.

This is quite opposite from my attitude to flying with SVT (I found myself lured into flying the SVT runway aspect instead of the needles), my policy is to have SVT off for the ILS approach. My reasoning being that SVT is based on GPS position, but without an activated WAAS LPV approach there is insufficient integrity checking to ensure the display is as precise as the ILS; effectively one flies a baro-aided GPS approach instead of the ILS.

On an LPV (or any other GPS) approach, on the other hand, both the needles and the image are driven off the same data, so it makes no difference, and on an NDB approach anything is better than the ADF. So SVT on is fantastic.

Opinions?

Biggin Hill

I have SVT on my G500. I’ve done many approaches set up for ILS or RNAV or whatever. As the approach develops I keep half an eye on the SVT. So far the SVT has been absolutely accurate and no doubt, if it was legal one could definitely land in virtually zero vision using SVT. Of course we will never know if it’s actually possible.

EGNS/Garey Airstrip, Isle of Man

It’s an old problem, which rose to prominence with “visual” avionics. Should you follow the picture, or should you follow the raw data? SVT is just the most recent step in this.

In the jet world, nobody AFAIK flies an ILS on the “needles” – you follow the flight director

So it’s a case of “public acceptance” which takes a very long time in aviation.

The other thing is that the safest way to land is with an autopilot following the ILS – or LPV if you have it. There is simply no question about this, IMHO. You are flying an approach trajectory which supposedly has a certified integrity. But an autopilot cannot follow an SVT display – you have to hand fly it (if you are actually using the SVT as primary guidance).

So really SVT is best for DIY approaches. I think I know one pilot who does such approaches using SVT but I would be suprised if anybody went public with it.

I am sure that if aviation was invented today, there would not be a VFR v. IFR distinction, which I believe is quite unnatural and merely results in nearly everybody who learns to fly giving it up almost immediately because they can’t go anywhere useful.

But then if aviation was invented today it would be banned by the health & safety vermin

Incidentally, what are the database costs? I cringe at some of the costs involved. If you take a typical G1000 type product, and look at the total cost of the databases (GPS, GPWS/TAWS, Jepp VFR/IFR Europe, SVT) it probably comes to about 3k/year. I am impressed by anybody who keeps that up, after the databases have first expired after they buy the new plane. And there is no way to get around the cost, like there is with terminal charts where you can get PDFs from somebody else.

Last Edited by Peter at 20 Dec 07:56
Administrator
Shoreham EGKA, United Kingdom

…my policy is to have SVT off for the ILS approach.

Why on earth would you do that? Of course you don’t fly an ILS approach on GPS generated synthetic vision. But once approaching the minimum, look for your approach lights and/or other visual cues, check if they match your synthetic vision display and continue to fly on that until you get a real clear view of the runway. We are talking about 10 to 20 seconds here and I see absolutely no safety problem. On the contrary: If your two pictures, synthetic and real world, don’t match upon reaching minumum you know there is something really wrong: Either your ILS signals are bad and you are aligned with the wrong lights or GPS position is wrong – go around immediately and save the day. With your SVI turnded off, you take away one safety net without any reason at all! But to everybody his own, as the Romans used to say…

EDDS - Stuttgart

While following the FD is just following an autopilot with servos decoupled.

EDXQ

Yes, of course. That’s a useful mode actually, with “smoking servos”

Administrator
Shoreham EGKA, United Kingdom
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