Back up instruments

[Bob Cook]

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