MAG Avionics Your Pitot-Static, Transponder and RVSM Experts

Your Pitot-Static, Transponder
and RVSM Experts.



MAG Avionics - Questions and Answers

MAG Avionics Your Pitot-Static, Transponder and RVSM Experts Q: What is a IFR Inspection required by FAR 91.411 and 91.413?
A: It is the altimeter inspections required by 91.411 and the transponder inspection required by 91.413.  Additionally the encoder is checked for data correspondence and the static system is leak checked.  These items need to be complied with every 24 calendar months.

Q: What is a VFR Inspection required by 91.413
A: It describes the transponder inspection.  On a new installation the static system must be leak checked and the encoder must be inspected to assure the altitude reporting is functioning properly.

Q: Why does the altitude on my transponder not agree with my altimeter?
A:  This is a common question from folks with newer transponders that display altitude.  The transponder always displays and transmits altitude at 29.92 inches.  Consequently if you are flying at a pressure other than standard, your altimter and the altitude display on your transponder will not agree.  ATC's computers know your altitude readout is always standard so they compensate for the current barometric pressure to display the correct readout.

MAG Avionics Your Pitot-Static, Transponder and RVSM Experts Q: What is an encoder?
A:  An encoder is a device that sends altitude data to your transponder, so the transponder can transmit altitude information (mode C).  Encoders come in many forms, most small aircraft have a separate blind encoder, which is a stand alone unit tied into your static system to provide altitude date for your transponder.  More complex aircraft use a encoded altimeter which is dual function - it tells the pilot the altitude and also send altitude information to the transponder.  Advanced jets use an air data computer much the same way, sending altitude date to both the altimeter and transponder..

Q:  How long does it take to perform the IFR Certification
A:  It takes between 2.5 to 3.5 hours

Q:  Do I need to be present for the inspection.
A:   No.  We just need access to your aircraft.  We work with alot of the FBO's and maintenance providers to schedule our inspection while your aircraft is in the shop for other items such as annuals or scheduled servicing.  However, you are more than welcome to attend while we do the inspection.

Q: I only fly VFR, do I still need an inspection?
A: Yes, every 2 years.  Living in the Houston area almost everybody needs the transponder if we operate within the 30 mile Mode C veil of Houston.  Remember most small aircraft altitude reporting is from a blind encoder.  Unless you get your transponder inspected per FAR 91.413 and have the encoder checked for data correspondence, you might never know your altitude reporting is off, particularly if you rarely fly with ATC services.

MAG Avionics Your Pitot-Static, Transponder and RVSM Experts Q:  Does it really matter if my static system leaks in an unpressurized aircraft?
A:  Yes.  Generally your altimeter will read slightly higher than actual due to the slight reduction of pressure in the aircraft cabin.  This is a dangerous situation especially during instrument approaches.

Q: Can your test equipment check my airspeed indicator for accuracy?
A: Yes.  We use a digital RVSM approved test box which is capable of simulating MPH, Knots or Mach airspeed from zero up to 600 kts.  Additionally we can simulate altitude up to 55,000 feet.

Q: If problems are found during the inspection, can you fix them?
A: Yes, the same person doing the inspection is also a certified Airframe and Powerplant Technician.  We stock most common parts so often the item is fixed during the same visit.

Q: What is RVSM?
A: RVSM stands for Reduced Vertical Separation Minimums.  Back in 2005 the domestic United States airspace went to RVSM from Flight Level 290 to FL 410.  Prior to that date above FL290 aircraft were separated by 2000 feet vertical spacing.  Now the vertical spacing is 1000 ft which effectively doubled the usable space.  Aircraft operating in RVSM airspace have to meet specific requirements and have an FAA accepted RVSM manual which details how they will comply with the regulations.   

MAG Avionics Your Pitot-Static, Transponder and RVSM Experts Q:What is a skin mapping or waviness inspection?
A: RVSM certified aircraft need to assure the area around the static ports has not been damaged or deformed in any way.  A very slight waviness in the aircraft skin or any other deformaties such as a loosening rivet or paint deformities can cause a slight pressure change across the static port at high altitudes or airspeeds.  This inspection complies with the requirements listed in the ICA's or Maintenance Manual to assure the area around the static ports is within allowable limits.

Q: I have a 406Mhz ELT that also broadcasts on 121.5  Can my A&P comply with the 91.207 inspection by listening to the broadcast on 121.5, like they did with the old ELT's.
A: This is a common perception in the GA community.  However, you must have a beacon reader capable of reading the 406Mhz output and the codes.  The 406Mhz ELT readers display the registration code, county, latitude and longitude and any protocols.  So if you have a 406Mhz ELT the person performing the inspection must have a data reader to legally sign off the FAR 91.207 inspection test.   MAG Avionics LLC has this capability.

Phone: 713.247.9174
Fax: 832.442.3501


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