No, it is not economical to upgrade a -006 or lower. -007 and higher units should be pursued instead.

The first revision of the TDR-94/94D manual is dated April 1989

Most Mode S transponders such as the Honeywell MST-67A and Collins TDR-94D include a feature that allows it to automatically determine the aircraft Registration Number (Tail Number) of U.S. registered (N numbered) aircraft. If the aircraft is U.S. registered and operated where the tail number is used as the call sign (Flight ID), then the operator does not have to manually enter the Flight ID. Therefore, a control head with Flight ID input such as the Honeywell PS-578 or Collins CTL-92E is not required.

The transponder automatically reads the Mode S address assigned to the aircraft. If the Mode S address falls within the range of addresses assigned to the U.S. by the International Civil Aeronautics Organization (ICAO), the MST-67A will automatically convert that Mode S address to the tail number of the aircraft and place it in the Flight ID register for compliance with Elementary Surveillance.

If the aircraft is operated where the Flight ID is not the tail number or the aircraft is not registered in the U.S., then a Flight ID control head is required to allow for manual entry of Flight ID. The flight ID may contain the company-assigned number for that particular flight such as an Airline name and Flight number.

For operators (usually commercial) whose Flight ID changes frequently, a control head such as Honeywell PS-578 or Collins CTL-92E provide for the entry of the Flight ID. The Flight ID may contain the company-assigned number for that particular flight such as an Airline name and Flight number. For civil operators whose Flight ID (usually the aircraft registration number) whose Flight ID does not change, a control with Flight ID input is not required.

Yes, the -008 can be installed into aircraft with non-integrated systems (i.e. -007 applicability; w/o Proline IV or 21) if they have the appropriate strap inputs set correctly.

Yes, anytime a transponder is removed or replaced an altitude correlation between what the transponder is reporting and what is displayed on the altimeter needs to be performed. This is outlined in FAA CFR Part 91.413. This regulation indicates that following any installation or maintenance of a transponder where data correspondence error could be introduced, the integrated system has been tested, inspected, and found to comply with paragraph (c), appendix E. Furthermore, these references indicate that an integration test between the altitude reporting equipment and transponder system must be conducted.

For complete information, please refer to these FAA regulations or contact Southeast Aerospace Tech Support team at shop@seaerospace.com.

Negotiating the exchange price of a unit only limits the allowable repair cap for the core unit. Southeast Aerospace's exchange transactions are based on the return of economically repairable core unit. Once the core is received and evaluated, the core repair cost incurred by SEA cannot exceed 75% of the original exchange price. That is, it cannot cost SEA more than 75% of the original OH/SV exchange price collected from the customer. Therefore, when and if an SEA exchange price is discounted, there is a risk that additional charges may be assessed once the core is returned and evaluated.

For more information, please refer to these other Exchange FAQs

Utilizing more than one antenna to improve the quality and reliability of radio signal is called antenna diversity.

Heavy and/or faster aircraft utilize top and bottom antenna configurations to eliminate the possibility of signal blind spots caused by shadowing. Lighter, slower general aviation aircraft typically only have 1 antenna and do not require antenna diversity. Although not completely uniform, the transmission pattern of a typical antenna provides adequate radiation above and below in relation to most GA aircraft even when the antenna is on the bottom of the aircraft.

The Mode S aircraft identification code is listed on AC Form 8050-3, Certificate of Aircraft Registration, as the International Civil Aviation Organization (ICAO) Aircraft Address Code. If the aircraft registration does not contain this information, aircraft owners with a Mode S transponder can obtain an aircraft identification code from the FAA Aircraft Registry in Oklahoma City, Oklahoma. This may be accomplished by writing to the following FAA address:

Federal Aviation Administration
Aircraft Registration Branch AFS-750
P.O. Box 25504
Oklahoma City, OK 73125-0504

You may also call:
866-762-9434
405-954-3116

In installations where two TDR-94D transponders are used, but space is not available to install four antennas, special relays can be used to operate the two TDR-94D transponders with only two antennas. This configuration can also be used to operate two TDR-94 transponders with one antenna. The diagram below shows a Coaxial Switch from Ducommun (P/N: D2-729B002) completing the configuration. The described PN has been replaced by a more recent version, D2-729B003. This new version is available from Southeast Aerospace.

In relation to the transponder technology, a squawk refers to a response that a transmitter responder (i.e. transponder) is making to an interrogation from Air Traffic Control (ATC). In a classic Mode A/C transponder, a squawk response included very basic aircraft ID, general status, and pressure altitude information.

A squitter or squit is a transmission that frequently sends aircraft ID and position data while not being interrogated. In some Mode S transponders and ADS-B devices, the squit transmission can include up to almost 50 parameters including lat/long position, direction of flight, velocity, and more.