Bi-annual pitot static, cor. Check

[azimuthaviation]

Was the $400 shop able to somehow legally meet the requirements of Appendix B with the altimeters never leaving the aircraft?

99.9% of the time no.

One of the tests in part B is a case leak test on the altimeter. How can you test the leak rate of a component while its tied into the rest of the system?

Also the hysteresis test, you have to drop the altitude from the highest point to the midpoint at minimum 6000 fpm, if you have a VSI in the system you cant do that test without pinning it unless you can isolate it (which you cant.)

Then theres the matter of performing adjustments if required (most of the time) on the altimeter. The altimeter needs a bit of disassembly and has to be manipulated, cant do that while on the panel.

[GyvAir]

Thanks, azimuthaviation. That was pretty much my answer as well when the question was posed to me.
I'm not sure if the practice is still going on at that AMO.. haven't heard any whining about it for a few years.

[AirFrame]

Was the $400 shop able to somehow legally meet the requirements of Appendix B with the altimeters never leaving the aircraft?

As with so many things in aviation, the answer is "it depends".

My pitot-static system uses quick-connect fittings that can be disconnected at various points in the system as needed. And the back of my panel is accessible with the canopy open. That makes it possible to do everything without removing any instruments. Removing instruments every year just to check something you can confirm with the tower on each flight is asking for trouble. It's even more ludicrous when you have aircraft with aluminum pitot/static plumbing everywhere. You're just asking for it to fail.

Guess it makes more work for the avionics shops, though.

[azimuthaviation]

Removing instruments every year

every two years

just to check something you can confirm with the tower on each flight

Just plain stupid. If your altimeter is out 300 feet, and your encoder is out 300 feet, as far as you and the tower knows, youre exactly where you should be.

It's even more ludicrous when you have aircraft with aluminum pitot/static plumbing everywhere.

The aluminum lines and fittings last 50 years, and are easily repairable if needed.

Guess it makes more work for the avionics shops, though.

The more you talk, you not only inadvertently reveal your own ignorance, you also reveal your character. People tend to judge by their own standards. You think avionics shops will take advantage of an opportunity to cash in on a system designed to facilitate easier air traffic management because thats something you would do. Most people dont think like you so dont attribute your sleazy ideals to them.

[photofly]

Not to argue with the experts, but the CAR 571 Appendix B test says the hysteresis test can be done at a rate of 5000fpm; doesn't sound like the VSI needs pinning. Last time I did a spin my rate of descent was about twice that.

And the case leak test is an altitude error pass/fail: if the whole system passes the test, doesn't logic dictate that the altimeter case leakage is within limits?

I don't see anything in the regulation that says the instruments need to be removed or even unplumbed: my tests have always been done (by a thoroughly scrupulous AMO) with a pitot head probe sleeve and a static port attachment, and a sophisticated automatic test system that runs through all the tests in about 10 (20?) minutes. It even has a built in microwave transmitter to talk to the transponder.

[azimuthaviation]

Pressure shall be increased at a rate simulating a descent in altitude at the rate of 5,000 to 20,000 feet per minute until within 3,000 feet of the first test point (50 percent of maximum altitude). The test point shall then be approached at a rate of approximately 3,000 feet per minute.

Yes, it can be done at a minimum of 5000, I was going by memory when I said 6000. How many single engine private aircraft have a VSI that goes that high? Its not going to like being dropped at 5000-20000 fpm when it only goes to 3000 fpm.

And the case leak test is an altitude error pass/fail: if the whloe system passes the test, doesn't logic dictate that the altimeter case leakage is within limits?

No. Case leak measures a very small part of the system. The pass for that is 100 feet after one minute when at 18000 feet. If the case is leaking, say, 500 fpm the whole system is so much larger, you wont detect it when its tied in with the whole system. There is a leak test for the whole system, thats a separate test altogether in CARs Appendix "B."

a sophisticated automatic test system that runs through all the tests in about 10 minutes

The altimeter shall be kept at the pressure corresponding to each test point for at least one minute, but not more than ten minutes, before a reading is taken.

Theres like 20 points to test in an altimeter, and you have to hold each point for at least one minute. The hysteresis has to be measured after holding it for five minutes. You simulated the pressure of the entire range of the altimeter, and brought it back to ambient while doing every test in between in ten minutes?

[AirFrame]

every two years

My error, sorry.

If your altimeter is out 300 feet, and your encoder is out 300 feet, as far as you and the tower knows, youre exactly where you should be.

My altimeter and encoder are the same device (Dynon D10A). What's shown on screen is what's broadcast on the transponder, apart from the correction to standard pressure. My transponder (Garmin 327) displays on the screen what the encoder is telling it. So I know what my altimeter is telling me, what the transponder is telling the tower, and what the tower tells me in return. Separate from both of those, I have a steam gauge mechanical altimeter to cross-check with.

The aluminum lines and fittings last 50 years, and are easily repairable if needed.

Aluminum fatigues. Every flared aluminum tube fitting wears every time it's connected/disconnected. It *will* need maintenance/repair if you're opening them every two years. Not so with plastic lines and o-ring sealed quick-release fittings.

You think avionics shops will take advantage of an opportunity to cash in on a system designed to facilitate easier air traffic management because thats something you would do.

Not at all. It's not the avionics shops that "take advantage" of this situation. They didn't make the rules requiring bi-annual recertifications. They didn't build the airplanes with aluminum lines and fittings. I was just pointing out that avionics shops get to reap the benefits of this system.

Most people dont think like you so dont attribute your sleazy ideals to them.

My comment was *not* a criticism of avionics shops, although you seem to have interpreted it that way. Perhaps your own prejudice guided you to make a snap judgement of your own...

[azimuthaviation]

Perhaps your own prejudice guided you to make a snap judgement of your own...

Bullshit. Youve said similiar things before, quite a few times.

Maybe the real issue is that me installing a SPOT doesn't keep you employed because I can do it myself...

aviation screws must ether be slotted (to ensure that the paint shops get regular work touching up paint jobs), or phillips (to ensure that AME's get regular work removing stripped screws).

Why they aren't Robertson, Torx, or Hex still amazes me.

That wasnt a one off comment. Thats the third time I remember off the top of my head that youve said that lately. Thats the way you think, thats the way you expect everyone else to be. I used to work with a guy who would hide the copper we used to make bus bars. Quite expensive, it came in large sheets that we could cut up. he would always hide it, kept it locked in quarantine, and told the VP where it was, so it would be safe in case any avionics guy tried to steal it and sell it to the scrap yard. Why did he do that? It wasnt because we had big problems around the shop with people stealing copper. It was because he would probably steal any piece of copper that wasnt nailed down and therefore he expected everyone else would do the same. So trust me when I say I know your type. You dont do a very good job of hiding it.

My altimeter and encoder are the same device (Dynon D10A)

Is that even allowed on certified aircraft? Yes the 0.01% of aircraft that can be done as described above are the ones with digital air data instrumentation. That is accounted for in CARs 571 "B"as well. They dont expect you to do hysteresis and case leak tests on altimeters with no moving parts. There are two sections in the standard for altimeters, (1) which of the mechanical kind that is common to 99.9% of aircraft, or if applicable (2) which states:

Altimeters which are of the air data computer type with associated computing systems, or which incorporate internally air data correction, shall be tested and inspected in parts or by major components to specifications developed by the manufacturer.

[ahramin]

99.9 percent of aircraft? Most of the aircraft I see are either built with or have retrofitted to glass. Round gauges are just too expensive.

[AirFrame]

That wasnt a one off comment. Thats the third time I remember off the top of my head that youve said that lately. Thats the way you think, thats the way you expect everyone else to be.

So prove me wrong through your actions, not by pulling numbers out of your *ss when you want to make a gross generalization:

Yes the 0.01% of aircraft that can be done as described above are the ones with digital air data instrumentation.

Really? Out of 28,945 aircraft on the register in April 2004, the total number of aircraft that can have a digital air data display (uncertified, like mine) installed is 10,739... So just over 30% of all aircraft in Canada. (i've included Amateur-Built, Basic Ultralight, Advanced Ultralight, Experimental, and Owner Maintenance in this list. If you restrict it to A-B and O-M only, where the population of digital displays is significantly over-represented in the population, it's still 4690 aircraft, or about 15% of the fleet). That doesn't include the portion of the certified fleet that has upgraded to Garmin, Aspen, or other Digital flight displays.

Yes, i'm aware of the difference between how many aircraft "can" have them installed, and how many "do" have them installed. But i'm also aware of the cost difference between a glass panel and a set of steam gauges... And the smart money today favours glass. I'd hazard a guess that 90% of amateur-built aircraft completed in the last 10 years have at least a basic glass panel display now (although some of those are probably *in addition to* steam gauges, that's how i'm currently configured).

[NeverBlue]

Also the hysteresis test, you have to drop the altitude from the highest point to the midpoint at minimum 6000 fpm, if you have a VSI in the system you cant do that test without pinning it unless you can isolate it (which you cant.)

Then theres the matter of performing adjustments if required (most of the time) on the altimeter. The altimeter needs a bit of disassembly and has to be manipulated, cant do that while on the panel.

I don't understand why you can't isolate the VSI and do an altimeter case-leak check in the aircraft. In fact you can do the whole 24-month inspection in the aircraft but can't do the whole thing by removing all the components and sending them to a shop.

Shops who sign-out the individual components don't necessarily have them signed out by AME's and your 24-month inspection is required to be signed out in the journey log by an AME working under an appropriately rated AMO...no way around that.

Also, you can in fact adjust the altimeter in the aircraft by adjusting the baro scale but you technically have to have an instrument rating on your AMO to do that.
You also have to test the Transponder in the aircraft after being re-installed - frequency, output power, sensitivity etc. - and you need a rated AME and the proper calibrated test equipment to do that.
Coax cables and antennas will almost always change these parameters that have been recorded on the bench.


You should never have rigid tubing going directly to the instruments IMO. Most instrument panels are shock mounted and the vibration inevitably causes leaks. The plastic tubing throughout really is the cheapest and the best to work with.

...and just an add...a lot of GA aircraft static leaks can be chased to the ASI case. The gasket behind the glass dries out and cracks and of course can't be field repaired.

[CpnCrunch]

99.9 percent of aircraft? Most of the aircraft I see are either built with or have retrofitted to glass. Round gauges are just too expensive.

I think it depends on whether you're talking about certified or homebuilt. I just did a quick search and found that the installed price of a G500 is about $21k. That's between 50% and 100% of the value of any plane I've ever flown, so it just wouldn't be feasible to upgrade - much cheaper to just replace the round instruments when they die, unless there's some cheaper certified alternative.

[azimuthaviation]

I think it depends on whether you're talking about certified or homebuilt.

Or just illegally put an uncertified piece of equipment on a certified aircraft and then tell everyone how cheap and easy aircraft maintenance is.

[azimuthaviation]

I don't understand why you can't isolate the VSI and do an altimeter case-leak check in the aircraft.

How much time will that save you?

Also, you can in fact adjust the altimeter in the aircraft by adjusting the baro scale

Yes, but how do you do that in the airplane? You have to take it out, look at it, clean it, inspect it, tag it... I mean, do some work, it wont kill you.

The plastic tubing throughout really is the cheapest and the best to work with.

Those are the worst. They get brittle and disintegrate when they get old. Try to loosen or tighten a nut and the whole thing breaks apart. but it is the cheapest and easiest to source and repair.

can't do the whole thing by removing all the components and sending them to a shop.

You have to do both.

[NeverBlue]

...it takes little time to take the fitting off of the altimeter and hook it to your test set.

and you say to me "do some work it won't kill you"

the Poly-flo tubing is just fine...now you can get finger tighten Nylo-seal fittings and there is no need to use a wrench and bust them all up. The proper tubing lasts just fine. I've seen all kinds of substitutes used that looks the same but is not the same.
Most new aircraft use the Poly-flo tubing inside the cabin.

You can adjust the baro scale through the front face of the altimeter...do a little research azimuth...I did it for years.

There is absolutely no need to remove anything from the airplane to do a 24 month re-cert.

You definitely do not have to do both...

[azimuthaviation]

You can adjust the baro scale through the front face of the altimeter...do a little research azimuth...I did it for years.

Yes I know how its done, Ive done it many times myself. You have to remove the slotted screw on the face of the altimeter, slide the locking device to the left and then the baro select will pull out a little bit, like the crystal in a watch. Have fun doing that in the aircraft.

[AirFrame]

These fittings from SMC make connections easy. Push to connect, and can be unlocked and released by hand when needed.
http://www.smcusa.com/top-navigation/ca ... aspx/87053

You have to remove the slotted screw on the face of the altimeter, slide the locking device to the left and then the baro select will pull out a little bit, like the crystal in a watch. Have fun doing that in the aircraft.

Isn't all of that done from the front of the Altimeter? If so, it might depend on how the instrument is installed. If it's mounted behind the panel I guess you might not have access to the slotted screw. But if the opening for the baro adjust is large enough, or if the instrument is front-mounted, it should be possible. Just don't drop any tiny screws down into the cockpit...

[NeverBlue]

Yes...it can be difficult to do depending on how it's installed.
I know what azimuth meant now...but I used to do it all the time on aircraft that didn't have an overlay and had the hole cut properly ( and depending on the make of the instrument and design of the bezel)
It is kind of tricky though cause the lock always wants to slide back down to the left when you try to put the slotted screw back in...I used to use the knob to hold the lock while I put the screw back in.

Technically you need to have an instrument rating on your AMO to do that though...and an overhaul manual for the instrument you're doing it to cause there's nowhere else it tells you how or even if you can do it.

...but I won't tell