Good altimeter, or just coincidence?

[COrocket]

I just flew both of my Missileworks RRC2-mini's for the second time. Two were used for redundancy on the flights. On both flights, both altimeters read the exact same altitude, right down to the exact foot. Is this normal, or a coincidence? I expected them to maybe be within a few (10-40' ?) feet of each other. Also, the flights were completely different in every way. The first flight flew an Intimidator 5 to 3245' starting at ~5000 MSL (colorado) and one flew a 1/4 scale nike to 2673' starting at ~0 MSL (florida).

Seems ridiculously accurate to me, although I know thats not the true altitude, due to nonstandard pressure/temperature fluctuations.

 

[Handeman]

I think it's coincidence, although not a huge one.

Both altimeters are the same model so the software is the same. The only differences are going to be the electrical tolerences of the parts. Since the manufacturing methods today allow very tight tolerences and they tend to form a bell curve around the center value. Although unusual, it is not that much of a surprise to have two of the same models read exactly the same.

This might be more common then we expect, I don't think there are very many people that fly two of the exect the same model/year/firmware version altimeters very often when you consider how many altimeters are out there.

 

[bobkrech]

Seems ridiculously accurate to me, although I know thats not the true altitude, due to nonstandard pressure/temperature fluctuations.

It doesn't necessarily indicate the accuracy of the two units, but it shows that the manufacturing and calibration tolerances are well controlled and reproducible between units so the two units display extreme precision, or the ability to reproduce values very closely on similar units.

Bob

 

[COrocket]

It doesn't necessarily indicate the accuracy of the two units, but it shows that the manufacturing and calibration tolerances are well controlled and reproducible between units so the two units display extreme precision, or the ability to reproduce values very closely on similar units.

Bob

I remember that precision vs. accuracy discussion from high school physics... i guess i should have worded that phrase ridiculously precise instead. Both models have sequential production numbers, so they were probably calibrated at the same time anyways.

 

[cjl]

That is definitely impressive consistency, though as bob said, it doesn't necessarily imply accuracy. I know all of my Featherweight Ravens read within about 0.5% of each other on every flight, but they still read different values (my last flight read as 7018 and 7032 feet on two different ones).

 

[bobkrech]

That is definitely impressive consistency, though as bob said, it doesn't necessarily imply accuracy. I know all of my Featherweight Ravens read within about 0.5% of each other on every flight, but they still read different values (my last flight read as 7018 and 7032 feet on two different ones).

If you look at your last flight, the altitude was 7025' +/- 7' which is 0.1% which is far better than the FAA requiments for aircraft altimeter accuracy of +/- 50' @ 7000'!

Bob

 

[jderimig]

If you look at your last flight, the altitude was 7025' +/- 7' which is 0.1% which is far better than the FAA requiments for aircraft altimeter accuracy of +/- 50' @ 7000'!

Bob

Reproducibility is not quite the same as accuracy. But impressive reproducibility in any event.