Altimeter Check Height Requirements

[Shagpile]

Hi all - I am just in the process of ordering the dash for an RV-7 which I am trying to make IFR as much as possible.

First of all, has anybody got any experience in certifying an experimental for private IFR? At the moment I am thinking it will need heated pitot, strobes, gps, nav radio, dual comms, dual (independent) attitude with backup power and analogue altimeter/airspeed.

I have decided not to get a DME as they are expensive and most approach plates say to use GPS in leiu of DME. At most - I can only think that this will affect my alt requirements due to RAIM, however not being certified GPS yet, I will have to research this further.

Anyway the point of this post was to ask whether I need a marker beacon receiver or whether I can get away with doing the ILS altimeter check height using GPS distance and altitude (as per the approach gradient).

ENR 7.3.1 says:

ALTIMETER CHECKS

The final approach segment contains a fix at which the glide path/altimeter relationship should be verified. If the check indicates an unexplained discrepancy, the ILS approach should be discontinued.



Basically I have done all my training using the Outer Marker as my check height, as most plates use this however I was wondering whether it is legal to use just the DME/GPS distance underneath the OM or FAF in place of the actual marker, and whether this leaves too much room for discrepancy in altitude due to accuracy.

Cheers !

[an3_bolt]

With regards for altimeter error in homebuilds - some time ago i used a trailing static drogue and a massive long pitot free from the aircraft wing effects to calibrate the static system of a high performance fibreglass thing.

Although it was for VFR operations only - I did find significant errors in the static system that required repositioning the static ports on the fuselage. After quite a few test flights got it down to some 2-3 knots over the full range of gear and flap down at 65 kts to 230 kts, and corresponding altimeter corrections. The original altimeter readings would have been unsuitable for VFR and IFR flight.

The static drogue with a calibrated and certified altimeter and ASI on a junction line in the cockpit to check the aircraft systems worked well. However - on a later flight the static drogue disintegrated at high speed. It was on lone from the then CAA - The days that they used to try and help people.

The best help might come from the SAAA. They should have the up to date gen on this stuff and motivated and helpful people.

With other thoughts on he mind - one could consider the electrical system that you have installed for IFR operations. Separate redundant systems are what we have installed in our one to ensure a single electrical failure or fault does not knock out other areas.

By the way - there might be someone who might be around here who could advise on minimum navaid requirements - there might still be a requirement for at least 1 adf or 1 vor with DME arrivals due to the fact that GPS may be used in lue for distance, however it appears that it is not yet permitted to use the GPS for azimuth guidance. Does anyone know what can and can not be done? Has anyone had approval from CASA to use GPS for azimuth guidance?

[Jabawocky]

The SAAA are the answer, they have all you need in info for such a build and IFR as well.

I have the contact details of a CASA Authorised Person who is endorsed or whatever the title is to do IFR a/c Cof A's and being an ex RAF and QF LAME might be just the guy you are looking for.

He is also a decent bloke, some ofthem can be a little like dealing with the KGB......makes CASA look friendly:eek:.

PM me and I will get you in touch with him.
J:ok:

[Icarus53]

I was wondering whether it is legal to use just the DME/GPS distance underneath the OM or FAF in place of the actual marker

You can use the "alternate fix" specified on the chart for your altimeter height check - this is why the chart will specify a a DME distance against each marker (so as to provide an alternate if your receiver or the beacons themselves are U/S).

The problem you will face with the instrument setup you refer to is that not all ILS approaches have marker beacons. SY 16L/34R is a prime example, and specifically the DME distances for check height/FAF are not based on the SY VOR/DME, but on separate DME established specifically for that approach. There is no reference point for your GPS, which is why the approach plate specifies "IKN DME required", and does not permit GPS in lieu.

These types of ILS approaches (off the top of my head there is one in BN too) will not be available to you unless you get a DME. Also, without markers, a normal ILS will become unavailable should your GPS become U/S.

Good luck getting your new baby airborne!

[Shagpile]

Thanks heaps for all the messages.

As for not being able to do an ILS into Sydney, I think I will just catch Qantas if I am that desperate to get there!! It sounds like it makes sense NOT to get a DME if most places I will operate will use GPS too. As for being stuffed if GPS goes offline, I suppose you can always get ATC to read out distance on finals should the worst happen. I think the chances I will be doing lots of ILS approaches is minimal, however it would be good to have there obviously with all this crazy global warming weather we are having lately.

I think for light aircraft flying, I will only be using IFR to get above and through the clouds to save fuel on transits and to open up the possibility of flying on less and suitable VFR days. If it is overly bad, I dont think its a good day to be doing recreational flying anyway. Anything that requires an alternate in a single engine sport aircraft due weather is probably pushing your luck.

[ForkTailedDrKiller]

Shagpile, for what its worth - here are some thoughts from someone who flies some reasonably "hard core" IFR in a single (Bonanza V35B).

1) Forget the DME - not of sufficient use to warrant the investment - I would rather put the money into a good GPS.

2) You have to have a TSO'd approach capable GPS. I think the Garmin 430 is the greatest thing since sliced bread. They are still expensive new but refurbished ones and those coming out of wrecks and panel up-grades can be scourced for significant savings.

3) Single VOR/ILS (comes with the Garmin 430)

4) ADF - I only ever use it for currency and renewals, but having it avoids the need to carry some alternates

5) Marker beacons I can live without, but I thought they were essential equipment for ILS appr. Have a Garmin 296 on the yoke that I set to the reference point for distance on the ILS (ie VOR) as a back-up.

6) Decent AP. While I hand fly my renewals to prove to myself (and the ATO) that I can do it - I would not launch into serious IFR without it. Mine couples the localiser, which is nice, would be even nicer if it coupled the glideslop but not essential.

7) Alternative powersource AH. My primary is air pressure, secondary is electric.

8) Stormscope/Strikefinder would be useful to avoid embedded CBs - I go VFR if these are forcast or stay on the ground.

9) Having appropriate holding fuel generally removes the need for an alternate. I have yet to fly to any alternate.

I fly GPS RNAV approaches whenever I can without having to go too far out of my way - so I am always very current. Having an ILS at my home aerodrome, I fly the ILS every couple of trips, when convenient, so again I am always very current.

I have put the terrain upgrade into the Garmin 430 and will shortly upgrade it to TSO 145/6.

Can't say I have ever felt under equipped to handle IFR in this aeroplane.

I get the feeling that ATC love RNAV capable aircraft cause they can take themselves to waypoints without the need for vectors. I have yet to be knocked back for the TL ILS. Have actually been cleared "present position (climbout from YTWB) - direct SATCO (some 500+ nm away) for the TL 01 ILS". Not sure that's technically legal but true story none-the-less.

Dr :8

[VH-XXX]

It's all spelled out here:

http://www.saaa.com/home.php?contentpage=ifr

There are no shortcuts or hear-say with equipping your IFR aircraft. Remember when equipped and up and running that you should realistically be requesting IFR tracks over areas which are not built up areas as per the regulations as you will be experimental.

[Capt Wally]

.....hey Dr:8 you sure have that Bo well kitted out mate..............but you did forget one thing (no not the wine as TC said in TopGun:)) you only got one fan !!!:}......................no matter how well kitted that bird of yrs is you are in IMC with the only 'cooling' fan U/S those avionics will be handy for sumfin' !........ taking you straight to the crash scene!:}..........just teasing Dr:8 .......................but why hand fly on a renewal?.........you don't have to & no ATO would expect you to esspecially if it's lousy wx !:) I know I hand fly 90% of my renewals even in serious cavok mainly 'cause it flies better than any human !:) Even our SOPS encourage the use of the auotflight system to do the hard yards:-)

Done much B58 flying Dr:8?

CW:)

P.S.......I think I saw some pix & stuff on the Bonanza's in the lattest ozzie plane mag?

[ForkTailedDrKiller]

...but why hand fly on a renewal? ....

Good question, don't know, just always have. I do use the AP enroute.

Done much B58 flying Dr:8?

I have a bit of time in 55's - B55 (BZR, CEN), D55 (ENC, ILM) ........ but have only ever flown 58's (EGE, EZD, SXS) a couple of times for renewals.

Dr :8

[Capt Wally]

...........no worries Dr:8............I was just giving you rev-up there:)

I gotta hand it to ya tho, flying true IMC in any piston single is brave stuff!:) I would be reluctant to do it in a SE turbine:)

I once chatted to a S.A. section PC12 driver & when I asked what the proceedure was for a no-eng app in IMC he scared the crap out of me with his answers esspecially the 'cloud-break' proceedure!!:bored:
What are yt thoughts on app's with no eng Dr:8?

I do all my app's coupled & if an eng has been pulled then I hand fly 'till re-trimmed then re-engage the A/P if it's applicable such as in the case of an NPA if recognized early in the approach.
Ya gotta love the twin Bo's.....none better !:)

Sorry for the thread drift:bored:

CW:)

[ForkTailedDrKiller]

Wally, I am pretty happy with what I have achieved in my life. Had one hell of a lot of fun, done a few things for the greater good and raised a couple of pretty solid citizens, so I wouldn't consider smacking in in the Bo to be a bad way to go!

I figure the chances of having a total engine failure in circumstances where I can't get a bit of a look at the ground before I hit it to be pretty remote.

However I won't go without putting up a good fight! I always fly high so if it happens in cruise I will have the maximum radius of action. I have a Motion Computing LS800 tablet computer sitting on the yoke running GPS moving map program over georeferenced WAC charts (see pic below), so I can head for the softest looking parking spot.

Having made it to the parking lot - full flaps, 60 kts - wait for it to hit!

Dr :8

http://www.fototime.com/4EFCA55333F38FF/standard.jpg

PS: The IO520 up front hasn't missed a beat in 450 hrs / 76,000 nm!

[Capt Wally]

...........no worries Dr:8.......sounds like yr a good God fearin' citizen & therefore God will watch over you, or yr IO520, the latter needing more than yr goodself !:)

I noticed in yr pretty pix that the DME is placarded as being U/S ?..............lets hope that's the only thing that's ever going to be U/S on yr good ship:)

Nice GPS stuff you have there, good job the cops aren't up there with us otherwise they would book us for not keeping our eye/s on the rd/sky !:)

Night.CW:)

p.s..................lovely spot yr on short final there, & who said the earth isn't flat?:}