Calibrating Aspen 1000 PFF Altimeter

[bill98]

It seems an Aspen In a plane I know displays the altitude about 100-150 lower compared to the stand by altimeter. 
standby altimeter shows correct elevation when setting altimeter to the airport barometric pressure setting at a sea level airport (0 feet for example) where as the Aspen would should -100ish

 

trying to dig up any literature on the topic on the google machine turns up little assistance and the cost of an avionics shop seems like it could be expensive. 

[kortopates]

Don't really know, but see CFR 91.411



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[bill98]

And just for clarification... I am asking if there is an easy fix for the Aspen that can legally be performed/ Any known issues where the altimeter wanders 

[kortopates]

These are usually from leaks in the static pressure line or trapped moisture. Since your backup alt is fine I would first be suspicious of the line between the backup and Aspen.
But once the line is opened, technically it needs to be leak checked by a tech. No problem though finding the issue, correcting and then getting it re-checked.
But I doubt it has anything to do with the Aspen itself.


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[Bob_Belville]

I doubt that there's anything you can legally do. Altimeter and static systems have to be tested and certified by:

§ 91.411...

(b) The tests required by paragraph (a) of this section must be conducted by -

(1) The manufacturer of the airplane, or helicopter, on which the tests and inspections are to be performed;

(2) A certificated repair station properly equipped to perform those functions and holding -

(i) An instrument rating, Class I;

(ii) A limited instrument rating appropriate to the make and model of appliance to be tested;

(iii) A limited rating appropriate to the test to be performed;

(iv) An airframe rating appropriate to the airplane, or helicopter, to be tested; or

(3) A certificated mechanic with an airframe rating (static pressure system tests and inspections only).

[GeeBee]

The Aspen requires a card to be inserted by the tech to adjust it. Had to have it done last year on my PA-18.

 

 

[bill98]

18 minutes ago, GeeBee said:

The Aspen requires a card to be inserted by the tech to adjust it. Had to have it done last year on my PA-18.

 

 

Thank you for the answer I was afraid of!

 

thank you everyone for the responses too and ensuring no hangar elves dare attempt to look at the issue!

[Bob_Belville]

28 minutes ago, bill98 said:

Thank you for the answer I was afraid of!

 

thank you everyone for the responses too and ensuring no hangar elves dare attempt to look at the issue!

Bill, you do no say whether you are instrument rated. If your Aspen is primary you are not legal to fly IFR with the deviation you have. You would not want to fly an approach to minimums with an altimeter "100-150'" wrong. And of course you are only able to check it on the ground using a reported barometric setting. The altimeter check is done across the range of altitudes from 0 to the maximum altitude the plane can be operated using calibrated test equipment. The altimeter must be accurate on a sliding scale that allows 20' deviation at sea level and 100' at 14,000'

[Marauder]

1 hour ago, bill98 said:

Thank you for the answer I was afraid of!

 

thank you everyone for the responses too and ensuring no hangar elves dare attempt to look at the issue!

Bill - the issue you are speaking about is an Aspen issue, not necessarily an issue with your pitot static system. The Aspen can go out of calibration and will need to be adjusted by an avionics shop (as GeeBee mentioned above). If your Aspen has older firmware, it might be worthwhile to have the firmware updated while they re-calibrate the Aspen.

[mike_elliott]

2 hours ago, bill98 said:

Thank you for the answer I was afraid of!

 

thank you everyone for the responses too and ensuring no hangar elves dare attempt to look at the issue!

Updating the firmware is a simple affair, will take the shop about 1/2 hr to do and another 1/2 hr well, because they are busy. Calibrating the Altimeter might be a bit more pending on why it is off. Fix the cause not the effect. Sometimes hangar elves are best left to do what they know how to do.

 

[bill98]

46 minutes ago, mike_elliott said:

Updating the firmware is a simple affair, will take the shop about 1/2 hr to do and another 1/2 hr well, because they are busy. Calibrating the Altimeter might be a bit more pending on why it is off. Fix the cause not the effect. Sometimes hangar elves are best left to do what they know how to do.

 

I am instrument rated but my plane hasn’t had an IfR CERT in the last year partially due to the Aspen also partially due to when I did pre buy they said if the altimeter check continued it would be out of limits. 
yet the transponder shows up just fine to ATC  this is what makes it so difficult for me to determine which ADSB to get  if my old narco 150 keeps chugging along and passes a cert then TailBeacon is a no brainer.   I also have a second Narco in my hangar id like to test out to see if it’d pass  but I’m a CB and don’t want to pay for a failing test ... would happily pay for it though if it passed  I want to check connectors on current narco installed and clean the antennas and see if it’d pass but $300 a pop for a test makes that cost prohibitive  

I had spoken with a gentleman based in the Dallas whom does the IFR pitot static and altimeter check and he mentioned aspens going out of “calibration” which made me ask the question (I just forgot to relay that late last night when I made the post)!

[Bob_Belville]

6 minutes ago, bill98 said:

I had spoken with a gentleman based in the Dallas whom does the IFR pitot static and altimeter check and he mentioned aspens going out of “calibration” which made me ask the question (I just forgot to relay that late last night when I made the post)!

One datum point: I have had an Aspen for 7 years along with a "steam" altimeter which is now the backup. Both are checked at least every 2 years.

Neither has changed - the Aspen matches my field elevation and the old altimeter reads about 20' low. That relationship seems to be consistent up through at least 12,000'.

[mike_elliott]

9 minutes ago, Bob_Belville said:

One datum point: I have had an Aspen for 7 years along with a "steam" altimeter which is now the backup. Both are checked at least every 2 years.

Neither has changed - the Aspen matches my field elevation and the old altimeter reads about 20' low. That relationship seems to be consistent up through at least 12,000'.

I had an Aspen in my F for about 10 years, no "wandering", I had one in a Bravo for 6, no wondering. Both were spot on with the backup. The encoder is a different beast that relays info to ATC. No fodder for PTK here....

[Oscar Avalle]

On 10/7/2019 at 10:19 AM, mike_elliott said:

I had an Aspen in my F for about 10 years, no "wandering", I had one in a Bravo for 6, no wondering. Both were spot on with the backup. The encoder is a different beast that relays info to ATC. No fodder for PTK here....

My ASPEN was off, but it was because of a leak in the pitot static system. Once that was checked... not a problem.

[LANCECASPER]

On 10/7/2019 at 10:54 AM, bill98 said:

I am instrument rated but my plane hasn’t had an IfR CERT in the last year partially due to the Aspen also partially due to when I did pre buy they said if the altimeter check continued it would be out of limits. 
yet the transponder shows up just fine to ATC  this is what makes it so difficult for me to determine which ADSB to get  if my old narco 150 keeps chugging along and passes a cert then TailBeacon is a no brainer.   I also have a second Narco in my hangar id like to test out to see if it’d pass  but I’m a CB and don’t want to pay for a failing test ... would happily pay for it though if it passed  I want to check connectors on current narco installed and clean the antennas and see if it’d pass but $300 a pop for a test makes that cost prohibitive  

I had spoken with a gentleman based in the Dallas whom does the IFR pitot static and altimeter check and he mentioned aspens going out of “calibration” which made me ask the question (I just forgot to relay that late last night when I made the post)!

It's your blind encoder that is showing up fine to ATC  via your transponder - that may not reflect at all what your altimeter says.

[Kpthnkn]

Our static system had a leak we found and fixed during a static check. Then we noticed the aspens began to wander gernerally lower. We found if we opened alternate static that the altitude corrected to normal and remained steady. I also witnessed this same behavior on a bench test where a tube had become blocked. So if you find a wandering aspen disconnect the static line and see if it stabilizes. If it does you have a clogged tube somewhere. JM2C

[Fly Boomer]

56 minutes ago, Kpthnkn said:

Our static system had a leak we found and fixed during a static check. Then we noticed the aspens began to wander gernerally lower. We found if we opened alternate static that the altitude corrected to normal and remained steady. I also witnessed this same behavior on a bench test where a tube had become blocked. So if you find a wandering aspen disconnect the static line and see if it stabilizes. If it does you have a clogged tube somewhere. JM2C

Welcome to MooneySpace.  Nice contribution based on experience.  Thanks.