Airspeed indicator

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Paul_Havelka

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Paul_Havelka
We have a Piper Cherokee 180c that has an intermittent ASI issue. Our ASI is a United 8100 series TAS indicator. The issue is that more often than not it reads fast by anywhere from 15-30 mph or so. We checked the pitot/static system and everything is right and tight. We also just installed a G5 and the airspeed on it is spot on and doesn’t vary at all(man I wish the G5 was primary for airspeed). Now it is my understanding that when an ASI reads fast that it is typically the indicator that has an issue and seeing as our G5 is reading correctly that seems to reinforce that thinking. I know they are not difficult instruments but our glass is also a little hazy and the face is faded so we were looking to send it for overhaul. I’m local to The Tulsa area and got a quote from Porter Strait for $400. Anyone know of any other places to get an overhaul or maybe even an exchange unit?


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How do you know your G5 is accurate?

How do you know your AI is inaccurate?
 
Creekrat said:
The issue is that more often than not it reads fast by anywhere from 15-30 mph or so.
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Not enough info to make a guess. Reads "fast" as compared to what? How intermittent and when, e.g., cruise, take off, etc?
Creekrat said:
We checked the pitot/static system and everything is right and tight.
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How did you check it? Did you check pitot and static separately or togather? Calibrated test box?
Creekrat said:
We also just installed a G5 and the airspeed on it is spot on
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Was this problem known before the G5 install? And what is the G5 airspeed compared to for it to be "spot on?"
Creekrat said:
it is my understanding that when an ASI reads fast that it is typically the indicator
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Possible. Or it can be an intermittent static system issue at your airspeed indicator as it can also cause indicating errors.

As for vendors, used Century Instruments for exchanges/repair for years but don't have any recent experience.
 
I would first make sure that the static system is connected to the ASI. If not, someone has disconnected it and the static pressure is being taken from the cabin, which has large pressure variations when someone turns on cabin heat or opens a vent.
 
Static system is connected to the ASI. The problem showed up just before we did a panel upgrade that included the G5. We verified that it is the ASI by a couple different methods. Several high speed taxis in multiple directions with the G5 in AI mode and verifying ground speed with ForeFlight as well as a few different speedometer apps. The ASI will read off by as much as 20mph sometimes just during a regular taxi.

Also, all other instruments are working correctly.


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Creekrat said:
We verified that it is the ASI by a couple different methods.
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Well, considering you're all set to spend $400 on a new ASI based on such extensive testing and troubleshooting, there's not much else I can add.....
 
Got a quote from flyaqi.com for $175


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Creekrat said:
Got a quote from flyaqi.com for $175


Sent from my iPhone using Tapatalk
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i use them not too long ago. good people, not that great at replying emails though.
 
A G5 is it Garman GPS right?? Can someone explain where it gets its data to explain the difference between the ground speed that it is calculating from the satellite, and the air that it is flying through to give true airspeed. My instructor has convinced me that if I taxi at a speed anywhere close enough for the ASI to show my true taxi speed then I'm going too fast.
 
LB 408A said:
A G5 is it Garman GPS right?? Can someone explain where it gets its data to explain the difference between the ground speed that it is calculating from the satellite, and the air that it is flying through to give true airspeed. My instructor has convinced me that if I taxi at a speed anywhere close enough for the ASI to show my true taxi speed then I'm going too fast.
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its not a GPS, its a electronic flight instrument, configured either for AI or HSI - https://buy.garmin.com/en-US/US/p/570665
TAS is only available in the air when connected to a OAT probe

taxi as slow as you can.... so that you can stop if need be and the most brakes are not your car brakes
 
GeorgeC said:
And a magnetometer, I thought.
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yah the magnetometer is installed as a part of the install, but i guess someone can choose not to install it and then G5 will only show ground track, it needs a position source, cant use internal GPS for certificated install (unless connected to a glareshield mount approved garmin GPS antenna ), ... there are a whole lot of ifs and buts in the STC

http://static.garmin.com/pumac/190-01112-10_21.pdf
 
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WannFly said:
yah the magnetometer is installed as a part of the install, but i guess someone can choose not to install it ...
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The GMU 11 Magnetometer is required when the G5 is installed as an HSI.

(Optional if the G5 is installed as Attitude Indicator.)
 
weirdjim said:
Why can it not be primary for airspeed?

Jim
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I'm not 100% sure this answers the question - But in the install manual for the G5, Section 2.1 - Installation Limitations. "The installation of the G5 requires the retention of the mechanical airpseed indicator, altimeter, and vertical speed indicator"

So, you have to keep your existing airspeed indicator. If you're talking about using the G5 in your primary scan for airspeed under IFR....? (I don't see why not). On a check ride, I'd certainly reference the old mechanical airspeed, but I'd definitely have an eye on the G5 ;)
 
Nathan is correct. It is part of the STC that you keep your original airspeed indicator.
 
I know some glider folks who use a wooden paddle pivoted to the strut with a "calibrated" sheet of copy paper marked in knots/mph taped to the strut. Nowhere is it mentioned in the regs that the airspeed indicator be "approved" to any standard, just that the airplane has to have one. Now, I'll ask the question again, "Why can't the G5 be primary for airspeed?"

Jim
 
weirdjim said:
Now, I'll ask the question again, "Why can't the G5 be primary for airspeed?"

Jim
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like mentioned before... the STC doesnt let you remove the ASI. now can you remove it and not tell anyone? sure, its your airplane and what you do to it is between you and the friendly FSDO
 
And I'll say again, because the STC doesn't allow for you to remove it and last time I checked you had to adhere to the STC to be considered airworthy by the FAA
 
When y'all can add A&P, IA after your name with 50 years of aircraft maintenance and dealing with the Feds, let me know. Otherwise, I disagree with your premise.
 
Let me know how that goes submitting the 337 that describes "removed airspeed indicator and installed G5"
 
Jim you know a lot of stuff and I appreciate your inputs, however please know that if someone really removes the ASI based on what you are saying, and gets ramped checked with only a G5, at that point he is getting screwed, unless you signed off on that submitted the 337, well then then you are on the line as well. If you can cite a reg that says the equipment manufacturer’s STC is optional and just a suggestion, let’s talk.
 
WannFly said:
Jim you know a lot of stuff and I appreciate your inputs, however please know that if someone really removes the ASI based on what you are saying, and gets ramped checked with only a G5, at that point he is getting screwed, unless you signed off on that submitted the 337, well then then you are on the line as well. If you can cite a reg that says the equipment manufacturer’s STC is optional and just a suggestion, let’s talk.
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We need more than "talk". We need a serious discussion without FAA pukes in the room to bring up nonessential "regulations" that don't exist. You want me to cite an FAA reg that says that the manufacturer's STC documentation is regulatory and I defy you to find one that says that it is.

You really need to look at the headline of the 337 -- MAJOR is the operative word (have you ever had to sign one?) Major. Replacing one airspeed indicator with another one? Doesn't arise to replacing a wing with one from another type of aircraft or replacing an O-200 with an O-470 does it?

Yeah, I know my fair share of "stuff" and most of the "stuff" comes from FAA crap I've had to put up with for 50 years from "Inspectors" who couldn't find their hiney in a telephone booth with both hands and a GPS.

jim
 
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Then by all means educate us because unless you understand english in a totally different way than we do you are wrong.

On page 13 of the G5 Part 23 AML STC it specifically states that the G5 is an electronic instrument display capable of operating as a primary attitude indicator, backup attitude indicator with primary rate of turn indicator, DG or HSI.

That is it. No more, no less. So if one must abide by the STC to install this instrument then how on earth can you determine that it can be installed and your airspeed indicator removed? Unless you are Garmin and the FAA all rolled into one or you have pictures of people in high places in compromising situations then it just ain't happening.

You don't have to be an A&P to be able to read and I guess you don't have to be able to read to be an A&P. I've seen this from you where you come in all high and mighty like you're big **** which just tells me that you sir, are struggling. Instead of making yourself look like a pompous ass why don't you help further educate the younger generations or the ones that want knowledge beyond "When y'all can add A&P, IA after your name with 50 years of aircraft maintenance and dealing with the Feds, let me know. Otherwise, I disagree with your premise."
 
Nathan Miller said:
Well, this went from a slight thread creep to a full on flame war.

Can we all take a breath?
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Sure, no problem. Let the others quote their chops. Here are mine without comment


A&P Earned after 5 years working for a major airline as a wrench (line maintenance everything from engine overhaul to replacing lights in the biffy)\
IA Earned after 5 years of working as a wrench in the aviation maintenance industry\
MS (Physics) Degree in Semiconductor Physics (San Diego State University)
Editor for the past 35 years for a national aviation magazine
College professor for the past 35 years in Electronic Technology for a California College

Your turn.

Jim
 
Alright I will play your game. Lets talk strictly Compliance ... not - I have seen someone in a glider measuring airspeed by taking their shirt off and throwing it at 092 magnetic heading from 5300 AGL, therefore, its optional. And if after all this, you can convince me, STC document is optional and a mere suggestion and everyone in Garmin just put that in for sh&^ and giggles, well, its my turn to learn something.

If you just want to use strange logic, I have some too - I can mentally calculate fuel remaining - should I yank out the fuel indicator? and i can assure you my mental math is better than stock fuel level indicator that comes in a span can

Do you agree that Airspeed Indicator is a PFI?
If you do not, please explain to us what this means:

8.2 Primary Flight Information (PFI). PFI refers to those functions or parameters that are required by the airworthiness and operational rules, such as airspeed, altitude, attitude, and heading (direction).
AC 23.1311-1C
Ref: https://www.faa.gov/documentlibrary/media/advisory_circular/ac 23.1311-1c.pdf

So to keep my plane airworthy, I need it. Agreed?

Now i go purchase something from Garmin, to replace my AI which is allowed by STC process because Garmin went through the STC process and proved to FAA that - An STC is the FAA’s approval of a major change in the type design of a previously type certificated product. (Ref: 1-6 a. https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_21-40A.pdf)

that piece of document also says - This shinny piece of equipment does not replace your airspeed indicator, but we do have, just not primary. its for situational awareness only.

now please tell me how can i throw away my ASI and just use G5 for Airspeed AND be complaint
 
weirdjim said:
Sure, no problem. Let the others quote their chops. Here are mine without comment


A&P Earned after 5 years working for a major airline as a wrench (line maintenance everything from engine overhaul to replacing lights in the biffy)\
IA Earned after 5 years of working as a wrench in the aviation maintenance industry\
MS (Physics) Degree in Semiconductor Physics (San Diego State University)
Editor for the past 35 years for a national aviation magazine
College professor for the past 35 years in Electronic Technology for a California College

Your turn.

Jim
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great CV, but none of this actually proves you are right. I have made my case in the above post. feel free to chime in with regs and complaince.
I have been breathing for 42 years, doesn't mean i understand my lungs more than my doctor who specializes in lungs.
 
First of all, if you will please rewrite your document in English I'll be happy to respond. Complaint (which is a complaint, non compliant) is one example of your ignorant post. We don't have shinny things, they are shiny. Try again in English.
 
weirdjim said:
First of all, if you will please rewrite your document in English I'll be happy to respond. Complaint (which is a complaint, non compliant) is one example of your ignorant post. We don't have shinny things, they are shiny. Try again in English.
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Wow. Jim, you’ve lost my respect with this thread.
 
weirdjim said:
Sorry, Salty, never p$$@f somebody that has been teaching this crap for 40+ years. Bless and keep you safe. Jim
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It would be nice if you could keep your cool and educate us. I think wannaflys post is well written and meets with my understanding of the regs as well. I’d love to learn from your experience something more than how much experience you have and how ignorant we are.
 
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