Altimeter deviation

[made82 0]

I noticed some deviation between Cpt F/O and especially the standby altimeter in real aircrafts. I asked a pilot about this and he said, if the altimeter show the same altitude with the same QNH, there is something wrong, because there have to be a smal deviation.

In all pmdg aircrafts this is not simulated? Or am i wrong and didn't found the setting for that, i think important "feature" ;-)

[downscc 1,327]

Google altimeter tolerance and you might be surprised to see that the tolerance requirements involve a lot more than simply setting the Kollsman window and checking, where you are correct in that there is a tolerance allowance and exact same readings might be suspect.  In GA aircraft you might be allowed 75 ft but in a bench test at SL pressure you're looking for +/- 20 ft.  The TSO'd high performance RVSM altimeters you see in jet aircraft are not going to have much error at sea level because at the flight levels where a small change in pressure is a large altitude difference the tolerances are very tight.   I don't agree that indicating a difference between AC and FO altimeters is an important feature in a Boeing jet, any difference is probably going to be a few feet and less than parallax error from different viewing angles.  Even in the C-414, TSOd for IFR but definitely not RVSM qualified, will only show less than needle width difference between sides.

[swood721 28]

I fly the 757/767 and the altimeter tolerance, per our company manuals, is 75 feet from a known field elevation, plus the difference between the Captain and FO altimeters is 40 feet a sea level (field elevation) 45 feet at 5000 ft (field elevation) and 50 feet at 10,000 ft (field elevation). 

On top of that, tolerance must be within 200 feet in RVSM airspace. 

[downscc 1,327]

1 hour ago, swood721 said:

I fly the 757/767 and the altimeter tolerance, per our company manuals, is 75 feet from a known field elevation, plus the difference between the Captain and FO altimeters is 40 feet a sea level (field elevation) 45 feet at 5000 ft (field elevation) and 50 feet at 10,000 ft (field elevation). 

On top of that, tolerance must be within 200 feet in RVSM airspace. 

Sure, I was referring to FAA circular on required bench testing tolerances, which vary by altitude as you elude to.  The cockpit tests are a different FAR.

[rsrandazzo 6,353]

Bernd,

"Have to be a small difference" is bunk.  Don't believe that.

In almost all installations outside of an initial factory delivery, there is a SLIGHT variation- but in digital airplanes that is normally invisible to the crew.

A few weeks ago I did change the mathematics for the plumbing on the standby system on the 747 so that it will deviate appropriately from the digital systems driving the primary altitude indication.  I don't have any intention of deviating the two primaries, however- as this is more of an installation issue than a design issue.

 

[BlueStar 323]

59 minutes ago, rsrandazzo said:

In almost all installations outside of an initial factory delivery, there is a SLIGHT variation- but in digital airplanes that is normally invisible to the crew.

You mean I don't have to tap on the altimeter face anymore? 

blaustern

[rsrandazzo 6,353]

Wilhelm,

Putting fingerprints on the glass in the cockpit of my airplane is a sure way to get a long and very boring lecture...

Except for the bloody touch-screens we have.  I love them but doggonit the FINGERPRINTS!

 

[BlueStar 323]

1 hour ago, rsrandazzo said:

Putting fingerprints on the glass in the cockpit of my airplane is a sure way to get a long and very boring lecture...

You would be in a long, distinguished line. :)

blaustern

[berts 97]

19 hours ago, rsrandazzo said:

Wilhelm,

Putting fingerprints on the glass in the cockpit of my airplane is a sure way to get a long and very boring lecture...

Except for the bloody touch-screens we have.  I love them but doggonit the FINGERPRINTS!

 

RSR,

I suggest you pop over the road and buy a pair of white gloves!  They should go well with your DC3 color scheme too, LOL

Bertie

[rsrandazzo 6,353]

Bertie,

We have a case of 1,000 pairs of white, cotton gloves that we require crewmembers to wear when touching the polished aluminum propellers on the DC-3. 

No joke.  We do.   

I hate fingerprints!

 

[BlueStar 323]

10 hours ago, rsrandazzo said:

We have a case of 1,000 pairs of white, cotton gloves that we require crewmembers to wear when touching the polished aluminum propellers on the DC-3. 

Didn't see this much on the C-47 and R4ds.  :)

blaustern