7AC Altimeter Failures

radar293 · Post by **radar293** » Mon Mar 03, 2008 09:57

I am new to Aeroncas after 40 years of flying a wonderful mix from Stearmans to Learjets. Really enjoying the slow pace and trip back in time.

A nicely restored 7AC that I have been flying can't seem to keep an altimeter operating. Owner kind enuf to share with me says he had same experience with prior 7AC's --- failure from vibration due to no panel isolation.

Any ideas re specific altimeters that tolerate the Aeronca experience better --- or some iso-fix --- other...? Would like to help out my friend who is sharing this nice aircraft with me...

Thx, Stu

Paul Agaliotis · Post by **Paul Agaliotis** » Mon Mar 03, 2008 10:18

Stu,
The altimeter may just need replacement. Many light planes have non isolated panels and don't suffer from chronic altimeter failure. There may be a vibration specific to your airplane.
Paul

Roger Anderson · Post by **Roger Anderson** » Wed Mar 05, 2008 17:39

Failure as in how? In the years of flying Aeroncas, I've never had an altimeter just "break". However, they do, and mine does now, frequently needle swing up and down a couple of hundred feet. I assume most are not conected to a stable static sysem, but instead just free air ported under the panel. The pressure change within the cockpit, windows open, closed, etc can cause needle swing. However, in most Aeronca flying the altimeter is just a "nice to have". In fact, non sensitive altimeters were standard for years.

smokiescfi · Post by **smokiescfi** » Sun Mar 16, 2008 07:16

The failed altimeter was a Garwin 387 that was overhauled in 2004. The mechanism broke from excessive needle vibration. I've installed a new Century Altimeter and it immediately began to swing. I've had this same issue on several other Champs I've owned and can only attribute it to the lack of vibration dampening.