On-Site Transmissivity Test Cell

Atlanta Aerospace is fully equipped with an on-site Transmissivity test chamber.  Each radome is initially tested during preliminary inspection and then proceeds through the repair process to be tested again prior to final inspection. Click here for information.

Radome Repair 

Radome repairs are performed on all regional jets and turboprops in addition to most corporate aircraft radomes. General aviation aircraft radomes are also repaired at our facility. Atlanta Aerospace  has a radome testing facility enabling us to perform transmissivity testing after radome repair. This ensures that the radar signal is transmitted properly through the radome. A typical radome repair consists of the following:

  • Complete removal of all paint coats
  • Assessment of damage
  • Repair of any damage
  • Application of all primer coats, anti-static coats, and top coat
  • Application of erosion boot
  • Transmissivity testing

Repair time required on the majority of radome repairs is 5-7 days. Average cost to repair a radome with typical paint erosion will vary depending upon the extent of damage. Delaminations and other types of damage will require more time and labor to repair. Of course, all repairs are accompanied with a FAA Form 8130.

LOANER RADOMES

In order to minimize your down time and keep you flying, we have several radomes that may be utilized as rentals, loaners or rotable exchanges while your radome is being repaired. Generally speaking, our turn time for radome repair will be 7 - 10 days.

Cost of radome rental is $100 per week plus a $3,500 security deposit, if Atlanta Aerospace repairs your damaged radome. The cost of Radome rentals without allowing Atlanta Aerospace to repair your radome is $250 a week, plus the $3500 security deposit. Shipping costs are not included in these fees.

We have loaner radomes for the following aircraft:

  • Raytheon Premier I
  • Hawker Beechcraft B400
  • Cessna 425
  • Lear 24/25, 34/35
  • King Air 90/200
  • Citation II series

We are acquiring other loaner units on a regular basis so be sure to ask if we have one in stock for your aircraft.


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AIRCRAFT RADOME FACTS

 

  • The radome is one of the most important parts on the airplane.  It must be able to withstand the abuse of normal flight while providing a window through which the radar signal can be sent.
  • If you think that your aircraft weather radar is supplying a false or inaccurate signal, the problem may very well be the radome and not the radar system itself.
  • The term radome comes from radar and dome – a dome shaped structure housing the radar antenna.
  • Radomes are typically made up using a honeycomb core material with several layers of fiberglass bonded to the core.  A distinct number of coatings are applied in proper order including an anti static coating to conduct.
  • If the radome has moisture, impact damage, or has been repaired improperly, the radar signal strength that passes through it will be degraded.
  • Proper maintenance of the radome is critical to achieve maximum signal strength from the radar transmitter.
  • The most common type of damage will be caused by moisture seeping into the core material of the radome.  This is usually a result of constant hammering from rain over a long period of time.  The moisture collects in the core material and begins a freeze/thaw cycle each time the airplane is flown.  This eventually breaks down the honeycomb material causing a soft spot on the radome itself.  Usually, this can be detected visually and by using a tap test.  Sometimes it will result in delamination of fiberglass plies and sometimes moisture buildup will only be detected using a moisture meter.  In either case, the radar signal is significantly degraded by the presence of moisture.  It is very difficult for a radar signal to penetrate a delaminated area.  Damage of this type usually requires replacement of the damaged core.
  • Screw holes where diverter strips are often attached can also introduce moisture into the radome.
  • Other types of damage include hail damage, bird strikes, lightning strikes, and other types of impact damage.  These are usually very apparent and require major repair.  Often major damaged radomes require a tool (mold of the original radome) to adequately effect a repair.
  • Radome damage is often classified as Class 1 through Class 5 damage.  Definitions of each class of damage follow:

 

Class 1 damage – surface damage to the radome that includes dents scars, scratches, erosion, etc.  This also includes excess paint layers or poor paint coatings that need to be replaced. 

Class 2 damage – delaminations, punctures, fractures, or other types of damage that is limited to the outer skin structure without damage to the core and inner skin.

Class 3 damage – punctures, fractures, or other types of damage that is limited to the outer skin and the core without damage to the inner skin.

Class 4 damage – Holes or damage extending completely through the outer skin, core, and inner skin.

Class 5 damage – Extensive damage to a large area of the radome requiring a complete overhaul of the radome.  The typically involves the removal and replacement of most of the composite structure and must be accomplished within a tool (mold of the original radome).

 

  • Radome repairs must be performed in accordance with the OEM repair manuals.  The mistaken opinion often exists in the field that they are to be repaired like any other fiberglass structure on the airplane.  This is far from true.  Very specialized repairs must be obtained from the manufacturer and performed as directed.  Some general repair information may be found in AC 43-13 but the structural repair manual of the manufacturer must be obtained for a proper repair.  Specialized tools are also needed to perform repairs on radomes. 
  • When our company receives a radomes it goes through the following repair process:

Remove the erosion boot (if present).

Do a visual inspection for damage.

Do a tap test to check for delamination (separation) of glass plies.

Perform a transmissivity test to determine how much radar signal strength is being lost.

Test diverter strips for conductivity.

Remove diverter strips if damaged.

Remove all coatings down to bare fiberglass by carefully sanding the radomes being sure not to sand into the fiberglass plies.

Do a moisture check on the radome to determine if moisture has ingressed into the core material.

Remove any damaged areas or areas with a high moisture content.

Replace removed and damaged areas with the proper core material and fiberglass used by the OEM.

Replace diverter strips if removed.

Test diverter strips for conductivity.

Build up the proper coatings used by the OEM on the radome including primers, sealers, anti-static coatings, and topcoats.  It is very important not to put more coatings on than are necessary.  A large buildup of coatings will cause a loss of radar signal strength through the radome itself. 

Put a new erosion boot on the radome to protect it from moisture erosion.

Provide a final transmissivity test to determine the Class of the radome based on signal strength.

 

  • A transmissivity test is crucial in determining whether or not repairs are necessary and/or have been properly accomplished.  The signal loss through the radome must be measured using highly specialized equipment.  The transmissivity test must be performed using a signal generator capable of emitting a signal of 9.375 GHZ (X band signal) that is typical of most radar transmitters.  The receiving antenna must be the same diameter antenna used in the actual airplane.  The signal is first transmitted to the antenna without the radome in place.  This signal is measured by a spectrum analyzer.  The radome is then placed on the test stand and signal again sent so that it must penetrate the radome.  The difference between the two signals is then measured by the computer and a % of loss is calculated.  Transmissivity signals are measured at several azimuths and elevations as the antenna is moved within the radome during the test.  Each one of these readings is recorded so a weak area may be identified and subsequently corrected.  Areas in need of repair can be pinpointed using a transmissivity test.
  • Radomes are classified according to their signal strength efficiency.  The classifications are set by the RCTA, Inc. that is a not-for-profit corporation formed to advance the art and science of aviation and aviation electronic systems for the benefit of the public.  The organization functions as a Federal Advisory Committee and develops recommendations on aviation issues.  The document that outlines the performance standards for radomes is RCTA/DO-213.  The RCTA/DO-213 manual also establishes the criteria and method of testing for transmissivity.  Test classes are as follows:

 

Class A – average of 90% efficiency with no one area being less than 85%

 

Class B – average of 87% efficiency with no one area being less than 82%

 

Class C – average of 84% efficiency with no one area being less than 78%

 

Class D – average of 80% efficiency with no one area being less than 75%

 

Class E – average of 70% efficiency with no one area being less than 55%

 

As you can see, a Class A radome is allowed to lose 10% of radar signal strength.  Usually, the OEM does not require a certain class to be maintained.  Practically speaking, you would question radar operation with a Class D or E radome.  After repair, our average classification is either A or B.

 

  • The ability for the radome to bleed off static electricity is also very important in the operation of the radar.  This is accomplished using anti-static coatings that are connected to diverter strips that pass the electrical charge through these strips to a ground on the airframe itself.    This is done without any type of arcing that would damage the radome.
  • As an operator, if you are experiencing radar problems it is often caused by the radome itself.  Radar signals will not penetrate moisture or damaged areas of a radome.  Often the radar will actually paint a false cell that is simply moisture in the radome.  The best way to determine if the radome is at fault is to remove it and send it to a certified FAA repair station that has the capability to test for transmissivity.  The radome can be tested for both loss of signal strength and moisture content.  There are very few companies that have the capability to test for transmissivity.  It is a highly specialized test requiring very expensive equipment.  This is the only accurate way to determine whether or not your radome is allowing the proper radar signal to penetrate the structure.
  • Our company sees a lot of improperly repairs that have been made on radomes.  Everything from using potting compounds to the wrong type core material, fiberglass and paint coats.  The most common problem found is usually moisture content in the radome.  Another common problem is a large buildup of paint that has occurred over the lifetime of the airplane.  The airplane is often painted several times with the radome in place which adds layers of paint that degrade the signal strength of the radar.  An excess buildup of more than .005 of an inch in paint coats can cause a large loss of radar signal strength.
  • Radome inspection should be a part of each pre-flight inspection along with all maintenance inspections.  Any evidence of damage should be checked out immediately.  A damaged radome will have significant impact on the performance of the airborne radar system.  This is even more critical on aircraft with Doppler radar systems.