How is static check different from transponder check?

[Erice]

I am entertaining the idea of getting a 91.411 IFR Static Check done on our Cessna 150 so that I can file and fly it in the IFR system. It's not the kind of platform that I'd take into hard IFR, but it's been 4 months since I got my IR ticket, and I have yet to get it wet. I did shoot a couple of approaches this week with a CFII, and I can verify that it's true--you get rusty quickly if you don't practice!

The airplane is due for its 91.413 ATC Transponder Check, too. What parts, if any, of these systems checks overlap each other, or are these two totally exclusive tests? I was wondering if the avionics shop might give me a discount for having both done at once.

Also, what kind of things might they find wrong during the static check? What kind of repairs might be typically expected to make it pass muster?
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[tonycondon]

our shop usually does them all at the same time. the static check just checks the accuracy of the altimeter, the transponder check verifies that the encoding altimeter matches up.

unless you have altimeter errors due to leaking the only way that i know of to repair is to overhaul or replace the instrument

 

[Ken Ibold]

Also, what kind of things might they find wrong during the static check? What kind of repairs might be typically expected to make it pass muster?

I recall my old Mooney having to have the interior ripped out and a bunch of the deteriorated plastic lines replaced, to the tune of 600 or so 1993 dollars.

 

[ScottM]

our shop usually does them all at the same time. the static check just checks the accuracy of the altimeter, the transponder check verifies that the encoding altimeter matches up.

unless you have altimeter errors due to leaking the only way that i know of to repair is to overhaul or replace the instrument

I believe the static check also is looking for leaks in the system too.

 

[Greg Bockelman]

our shop usually does them all at the same time. the static check just checks the accuracy of the altimeter, the transponder check verifies that the encoding altimeter matches up.

unless you have altimeter errors due to leaking the only way that i know of to repair is to overhaul or replace the instrument

Transponder check checks more than just the encoder, IIRC. You still have to have a transponder check even if it does not have an encoder.

 

[KennyFlys]

The static system and transponder test explained to me involves a suction device placed on the static port and another device on the pitot tube supplying ram air. The static (negative) pressure is reduced to represent 20,000 feet and the ram air pressure is supplied to also represent the airspeed at 20,000 with normally allowed errors; both at standard atmosphere.

Through this, they are able to determine if the altimeter and airspeed are providing the correct indications as well as detect potential errors by leakage in the lines to both the static port and pitot tube. A test receiver will determine if the correct transponder code (Mode A) and encoded altitude (Mode C) are reported along with the "handshake" when identifying.

 

[poadeleted20]

For all the details, see Appendices E and F to Part 43 -- and they are in your regular pilot-edition FAR/AIM book.

 

[skyflyer8]

I know of a Cessna with a transponder that got stuck reporting 30,000 feet. The plane came into the avionics shop I used to work at. I wonder how long it was that way before the owner realized? I always thought that was kind of funny. Hopefully no harm was done.

 

[tonycondon]

yea that really ticks off the high altitude sectors, because they HAVE to separate traffic from that blip, right Bob?

I know of a Cessna with a transponder that got stuck reporting 30,000 feet. The plane came into the avionics shop I used to work at. I wonder how long it was that way before the owner realized? I always thought that was kind of funny. Hopefully no harm was done.

 

[KennyFlys]

yea that really ticks off the high altitude sectors, because they HAVE to separate traffic from that blip, right Bob?

Isn't there the ability to track down such a signal through the Mode S code?

 

[tonycondon]

well yea, but only a very small percentage of transponders are mode S

 

[jmaynard]

Isn't there the ability to track down such a signal through the Mode S code?

Good question. I've been told that the mode S code is not back-referenced to the tail number on the ATC radar screen. That seems kind of a waste to me.

 

[gprellwitz]

I know of a Cessna with a transponder that got stuck reporting 30,000 feet. The plane came into the avionics shop I used to work at. I wonder how long it was that way before the owner realized? I always thought that was kind of funny. Hopefully no harm was done.

I know of a little aerobatic plane that landed a few years ago with a transponder reading FL 600! We got a call from ATC asking us to tell the pilot of the plane that just landed that his altitude encoding appeared to be malfunctioning!

 

[KennyFlys]

Good question. I've been told that the mode S code is not back-referenced to the tail number on the ATC radar screen. That seems kind of a waste to me.

While it appears we can't go into the database and search by Mode S code, I'm sure the FAA can when they so desire.

 

[KennyFlys]

I know of a little aerobatic plane that landed a few years ago with a transponder reading FL 600! We got a call from ATC asking us to tell the pilot of the plane that just landed that his altitude encoding appeared to be malfunctioning!

Static problems?

 

[gprellwitz]

Static problems?

Couldn't have been just a blocked static port or similar, because there's no way an aerobatic biplane ever got near FL600! My guess, and it's only that, is that it was in the encoder.

 

[KennyFlys]

Couldn't have been just a blocked static port or similar, because there's no way an aerobatic biplane ever got near FL600! My guess, and it's only that, is that it was in the encoder.

With that kind of error, it would have to be blocked with quite a vacuum.

I occasionally look at the transponder to see what it's reporting and compare it to be approximate to the indicated altitude.

 

[Erice]

Just in case anyone is interested, here is the reply I got from the avionics shop.

If we perform the 91.411 IFR check the 91.413 transponder check is automatically included as part of the package. Any repairs that are necessary are done on a time & material basis.

What kind of problems can you expect and how expensive can it get? If this is the first time the aircraft has been certified for IFR or it has been many years since its last certification, I would expect some problems, such as static system leaks or even a possible altimeter failure due to excessive friction, barometric correction scale errors or hysterisis. The altitude encoder might also require some adjustment. Repairs on this type of aircraft typically are not too expensive, usually in the $200 - $400 price range.

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