Back up instruments

Juan M. Padrón · #1 05-27-03, 08:59 PM

Hello everybody.If anybody could give a piece of advice,I would really appreciate it.I had on my 337B an altimeter and a vacuum turn and slip as a back up.I sent them to overhaul and the turn and slip was discarded for having some radiation material and the altimeter is not worth to repair.My mechanic suggest an electric gyro horizon as a backup but so far what I've seen is that they cost aproximately 2000 $ a piece.Any suggestions what to do?Thanks a lot.

Paul Sharp · #2 06-02-03, 04:41 PM

In the USA, the FAA doesn't allow "replacement" of a turn and slip with another AI, although this is a hotly requested item for change. Meanwhile, if you can get away with it where you are, or you simply want to add the redundancy (as I did), you can get another AI. I got one and had it installed for about $1500 total.

Juan M. Padrón · #3 06-02-03, 08:29 PM

Thank you Paul.I don't intend to replace the turn and slip that is in front of the pilot,the one I want to replace is one that was in front of the copilot and was used as a backup.Do you think is worth getting an electrical redundancy horizon gyro?Where did you get it?

Regards:

Juan M. Padrón

Bob Cook · #4 06-03-03, 08:06 AM

Juan

There are a number of issues. Having a backup on the copilot's side being referenced by the pilot can cause fatal accidents.... See the Carnahan accident report... parrallax error.

The ideal is a BF Gooderich electric 2 1/4 inch standby with power supply.... Ouch..... 10K USD?

Third option is a 3 inch standard electric AI located in top and left of radio stack where the VOR head should be located. This could be shared but at least in the range of the pilot's scan. These are available new or used at a reasonable price. There is no backup if there is an electrical failure. Around 2k or less.

The chances of a vacuum AI failing is rather small if there are dual vacuum pumps. Just listen to the rundown of the gyro after power shutdown. It should run for 3 -4 minutes minimum. Also listen for bad bearing noises. If it doesn't erect right away then it should be overhauled. There are lots of preliminary signs of failure.

Try using a garmin 295 gps or equivilant with a turn coordinator. Works really well including an emergency ILS approach if need be. It is not difficult to keep the aircraft in a safe attitude, especially when you do not need to chase a wet compass.

Replace the vacuum pumps after 500 hrs regardless of conditon!

Risk management is the name of the game.

Bob

Paul Sharp · #5 06-03-03, 11:59 AM

Mine was an electric AI by R.C. Allen company. It cost about $1500 and the avionics shop charged me $300 to install it.

Mine is right on the lower right side of the pilot's side of the panel, easy to see (no parallax problems) and keep in the scan.

rick bell · #6 06-03-03, 12:04 PM

it may be rare; however i have had both pumps fail at the very same time. what a distraction with all the gyros going nuts spinning evry which way, along with the racket they make

WebMaster · #7 06-03-03, 07:50 PM

Quote:

Originally posted by Bob Cook
Juan

Replace the vacuum pumps after 500 hrs regardless of conditon!

Risk management is the name of the game.

Bob

Well said, Bob

Francisco · #8 06-03-03, 09:28 PM

Hi guy, what about the new palm pcs, they have all including a artificial horizon would it work? probably lots cheeper

Francisco

rick bell · #9 06-03-03, 10:54 PM

I REPLACED A RC ALLEN TURN AND BANK (ELECT.) SENT MINE IN FOR OH AND THE SHOP SAID IT WAS NOT REPAIRABLE. SOLD ME ANOTHER OVERHAULED FOR (I THINK AROUND) $500. IT TAKES ABOUT FIVE TO TEN MINUETS TO INSTALL AND LESS TO TAKE OUT. IT JUST UNSCREWS FROM THE FRONT AND UNTWIST THE CANNON PLUG. YOU ARE PAYING WAY TOO MUCH FOR INSTALLATION AND THE INSTRUMENT. I USE A SHOP SONEWHERE IN OK, THEY WERE QUICK ALSO

Bob Cook · #10 06-04-03, 07:48 AM

Francisco

The palm units sound great..... however........

1)you need and instrument(s) that is readily available and not something you pull out of a flight bag.

2) where do you put it?

3) Is it approved?

4) Are you willing to "trust" it!

5) Damn batteries again.... are they fresh and will they last?

They do work great but until the system is incorporated into a 2 or 3 inch format and readily available I rather doubt it is a substitute. People keep forgetting these are TOYS!

Try partial panel with the one of the yoke mounted garmins such as the 295 and you will find you can have an AI failure without a problem as an alternative to a backup electrical AI. More important, practice using one so you can have some confidence in managing a failure. Again, practice and have fresh batteries.

I lost my KI525 (DG) IFR out of MCO and climbed thru 11k ft using the 295 rather than heading back and doing an ils. It worked great. I had practiced with it before and had the confidence to continue. The update is quite satisfactory.

fyi

Bob

WebMaster · #11 06-04-03, 01:13 PM

Bob,
I have C-Map, AvMap, and there are lots of screens I could have up, but the one most often use does not display altitude. If you have one, could you, or someone else post a picture of the screen you would put up on a Garmin that would display all pertinent information. I can then use that as a model for my AvMap system. I'll get a picture of mine as well.
Thanks

Juan M. Padrón · #12 06-04-03, 11:36 PM

Thanks a lot everybody for your considerations,I'll keep them in mind when making a decision.

Regards:Juan M. Padrón

Bob Cook · #13 06-05-03, 07:28 AM

Larry

The altitude is of little value off the gps unless you decide to add or subtract the barometric difference, therefore I rely solely on the barometric altimeter.

As to the indicator I use the HSI function screen with the ground speed and distance to wp showing. The new 196

http://www.garmin.com/products/gpsmap196/

shows a virtual panel. Key is having the unit (any) update sufficiently fast so that making turns is not a guess. Rate of turn is easily compensated by using less than rate one turn or sufficient to keeping up with the display. The 295 is very good for this purpose.

The 295 has very good vnav function (better than the 530) so you can use it for maintaining a controlled rate of decent and the horizontal hsi steering bar indicates your deviations.

If you have an electric dg or hsi then the AI failure is less of a concern. Situational awareness keeps you out of the trees.

Bob