Backup Instruments?

gf30269 · #1 07-11-2009, 11:13 AM

We're building a VFR RV-7 with instruments centering around a Dynon D-180 and Garmin GDU 375. My question is: What, if any, backup gauges do we need? Keeping in mind that it is a VFR plane with battery backup for the two units above, what would you recommend?

Thanks,
George

Ironflight · #2 07-11-2009, 11:31 AM

VFR Only? If you are comfortable flying without an ASI and Altimeter, add an oil pressure switch and a light to come on if you lose pressure, and you'll probably have enough. Add to that until you reach your comfort level.

frankh · #3 07-11-2009, 12:33 PM

My personal opinion of course but I don't think you need anything at all.

Even taking Paul's suggestion above for the oil pressure light..I have nothing against the idea, just that adding such a light is protecting against two failure modes..I.e, the chances of the Dynon failing and the oil pressure going away during the same hour would be the product of the two risks..

I.e lets say the Dynon will fail once every 2000 hours then the chance of it failing in any one hour is 1/2000. Say its the same probablity for the oil pressure fialig.

Then the risks of both happening is 1/4,000,000. Is it worth protecting for a 1 in 4 million risk?..Having said that an oil light is dirt cheap so why not?

I think if you have a GPS that can give you an approximation of airspeed (for landing) then thats good enough.

Rememring that VFR means looking out the window then I am personally surprised that builders add all kinds of guages just in case for what seems to be very little reason..Resale maybe?

Anyway I'm rambling and I should be getting my suit out to go to a wedding..

Cheers

Frank

Mike S · #4 07-11-2009, 01:55 PM

Quote:

Originally Posted by gf30269

My question is: What, if any, backup gauges do we need?

Thanks,
George

Those that will make you comfortable.

This is a purely subjective issue.

I used a TruTrack ADI, with the built in GPS, to give me horizon, heading, and ball all in one, and a VSI, AS, and Alt rounded out the bunch.

Standard 6 pak in only 4 holes

Bill Wightman · #5 07-11-2009, 02:09 PM

I agree this is a pretty subjective issue. We all have different ways to interpret and manage risk. Those with some time, who've been through some, shall we say, "less than optimum" flying experiences might have vivid memories that will forever shape their outlook. I'm one of those guys; don't want to regurgitate any of that now though - makes my palms sweat and typing gets difficult.

So, they say a picture's worth a thousand words:

The D100 has a 2-hr internal backup battery and the electric system is split (mostly) into two separate busses. Although I like the D100 alot, I still see it as a "single point" system: if it throws up, then I've lost the PFD. At night, that would be... uncomfortable. So I have a couple steam gages. I like that.

Kyle Boatright · #6 07-11-2009, 02:36 PM

Quote:

Originally Posted by gf30269

We're building a VFR RV-7 with instruments centering around a Dynon D-180 and Garmin GDU 375. My question is: What, if any, backup gauges do we need? Keeping in mind that it is a VFR plane with battery backup for the two units above, what would you recommend?

Thanks,
George

Personally, I don't see the need for backup instruments (and their cost, weight, and added complexity) for VFR flying. There are plenty of 60 year old airplanes which have an ASI, altimeter, tach, oil pressure gauge, oil temp gauge, compass, and fuel gauge. No backups whatsoever, and those airplanes have done just fine.

Mike S · #7 07-11-2009, 03:24 PM

Quote:

Originally Posted by Kyle Boatright

There are plenty of 60 year old airplanes which have an ASI, altimeter, tach, oil pressure gauge, oil temp gauge, compass, and fuel gauge. No backups whatsoever, and those airplanes have done just fine.

This is exactly why I want them.

It is the geewizzbang electronic stuff I am not too sure of----give them the same 60 year track record, and maybe then ..................

jsharkey · #8 07-11-2009, 05:21 PM

I have a D100 with battery - and an ASI, Alt, Compass, Slip ball, Tach, Oil P, Oil T and Fuel gauges. I use the D100 like an "AI/DG plus" combo in the middle of the panel. I also have an Oil P/Master Idiot light, Low Voltage light, CHT/EGT and Ammeter. I can lose all electrics and still have a great VFR panel.

Jim Sharkey
RV6 - Flying!

L.Adamson · #9 07-11-2009, 05:22 PM

Quote:

Originally Posted by frankh

Rememring that VFR means looking out the window then I am personally surprised that builders add all kinds of guages just in case for what seems to be very little reason..Resale maybe?

For personal reasons, I've kept track of "flight into terrain" accidents for many years. There are a lot of inadvertant flight into IMC accidents, both in daytime & darkness, in which the pilot had planned to remain VFR. I'd install the instruments.

L.Adamson ---- RV6A (flying)

L.Adamson · #10 07-11-2009, 05:26 PM

Quote:

Originally Posted by Kyle Boatright

Personally, I don't see the need for backup instruments (and their cost, weight, and added complexity) for VFR flying. There are plenty of 60 year old airplanes which have an ASI, altimeter, tach, oil pressure gauge, oil temp gauge, compass, and fuel gauge. No backups whatsoever, and those airplanes have done just fine.

And a whole lot of wrecked ones too! Far too many inadvertant flight into IMC conditions over all these years.

L.Adamson --- RV6A