I have remained mute on this subject up till now because I really don't know what the answer is. And I hate to admit that...
However, here's my opinion.... The altimeter is a required instrument, per FAR 91.205. Therefore, it must meet some minimum criteria. For example, you could not install a Timex watch with an altimeter function, even though it read out in feet. Neither could you install one you got from Sharper Image for your car, even if it cost more than the TSO version. The Erco drawing calls for an Aeromarine 520N altimeter. So, for sure, that is a suitable instrument. Obviously, it was not TSO'd as the concept didn't exist then. So, what constitutes a suitable replacement? Or, put another way, is the Chin Wah altimeter from Aircraft Goose for $200 a suitable replacement? The answer is "it's up to the installer", I think. Ultimately, the A&P who signs off the install, or, absent that, the IA who signs off the next annual, (or the last annual if you as the owner sneak the thing in between annuals) will be held responsible for it. Now, lets assume you are involved in a mid air collision with an oncoming IFR Bonanza at 6000 feet. The wreckage of you plane reveals a Chin Wah altimeter stuck at 5500. Who's to blame? Bottom line, If I'm installing that altimeter, I want some assurance it is an aircraft quality part. The TSO is that insurance. Your IA may view it differently, assuming he knows what he's looking at... John Cooper Skyport Services www.skyportservices.net
