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Thread: ADS-B and aerobatic aircraft

  1. #1

    Join Date
    Nov 2011

    ADS-B and aerobatic aircraft

    Many folks have questions about ADS-B and aerobatic aircraft. Most questions are centered around the technical limitations of the current ADS-B equipment and its inability to keep up with the rapid heading, altitude and airspeed changes that we normally experience with aerobatic flight and the fact that most, if not all, of these flights indicate that the ADS-B equipment is not performing properly. Which then begs the question, am I going to get unwanted attention from the FAA for this and what can I do to avoid this.

    The IAC has been working with the FAA Equip 2020 Focus Group in an effort to try and resolve some of these issues. The main issue is that of antenna masking during aerobatic maneuvers and the false "fail" signal it generates to the FAA's monitoring system. The FAA is well aware of the problem associated with aerobatics and erroneous ADS-B signal reporting and is trying to figure out a way to deal with it. For those aerobatic pilots that equipped their airplanes with ADS-B Out system and gone through the process to demonstrate it is compliant and who have on into the system to review one of their post compliance testing aerobatic flights, you may have noticed that your fight track shows a green line from the airport to your favorite practice area then your aerobatic practice looks like a red spaghetti bowl only to be followed by another pretty green line back to the airport. This type of flight may generate an NPE (non performing equipment) report within the FAA which they may or may not choose to act upon.

    This type of flight may elicit a phone call or letter from the FAA. The FAA s trying to gather information and has promised me, as the IAC Government Relations Chair that there will be NO enforcement actions resulting from any of this. A year or more ago when this problem was recognized, I sent them a large list of aerobatic aircraft types that they will likely see with this issue. I realize that there is no way I can give them every type of aerobatic aircraft considering the large number of homebuilt aircraft out there but it as a start.

    I speaking with the FAA this past week, I was told, as the number of aircraft being equipped with ADS-B increases, the number of "real" non-compliant installations is growing rapidly and they are trying to get their arms around how to deal with this. They tell me that when they physically look at an NPE report from an aerobatic flight it is obvious what is going on and they leave it alone. However, with the increasing number of non compliant aircraft, they do not have the staff to physically look at every NPE so the acro guys get caught up with the rest of the aviation community during their automated process of dealing with NPS aircraft. The FAA does not have time to make phone calls and is now sending certified letters to the registered owners of aircraft who have generated an NPE report

    I plan to write a more detailed article for Sport Aerobatics on the topic very soon. However, for now, my advice should you receive communication from the FAA about an aerobatic flight and the performance of your ADS-B Out equipment, is to respond their inquiry and be done with it. No need to call your attorney or read more into it than it is. Believe me, I get it, nobody wants get a certified letter from the FAA to talk about their last flight.

    I hope this info helps. I know it is far from perfect but it is what it is for now.

    Bruce Ballew
    IAC Government Relations Chair

  2. #2

    Join Date
    Aug 2011
    Thanks for the update!

  3. #3

    Join Date
    Aug 2011
    Good info, Bruce! I've just completed an ADS-B install in my Legacy; it's Experimental and non-aerobatic, but I've learned a lot in the process. I got a couple of red-boxed FAA reports, and after some consultation with the manufacturer (uAvionix), I got a clean report, but an annual inspection got in the way. Hopefully I'll have the annual done today and some good enough wx over the weekend to make an "official" flight. The uAvionix unit is a UAT with its own GPS and ground link antenna.

    My Extra has two GPS's, a Garmin 420 WAAS, and a Garmin 250XL non-WAAS. Both lose the satellites during aerobatics, but it takes the WAAS unit several minutes (say, 4 to 8 minutes) to lock back on. Do you know if it's GPS loss that's the problem, or is it loss of the ADS-B link to the ground towers? There are "diversity" options available for, say, the L3 Lynx transponder/WAAS GPS/ADS-B, which places another antenna on top of the plane. I'm wondering if that would help, despite its considerably higher price.

    Doug Sowder

  4. #4

    Join Date
    Nov 2011
    I’m not the technical expert on the topic but the FAA has told me it’s an antenna masking issue which I interpret as the aircraft loses it connection to the ground based station. I don’t believe it’s a GPS issue but I can’t say for certain. I’m having a meeting with the FAA ADS-B Focus Group team lead early in the week to get a better understanding of the technical parts of the issue and to develop some interim info and guidance for acro pilots that we can share with everyone. So, there should be more info on the topic forthcoming soon.

  5. #5

    Join Date
    Aug 2011
    I have started the process of equipping my 1929 Waco ATO with ADS-B out by installing a Trig transponder. One box and the antenna and I can be compliant. My concern is not a letter or phone call; my concern is that the FAA is not yet providing guidance on where the end requirements will be. I have no interest in additional boxes, antennas or other technology that might be required as a "solution" to the aerobatic problem. If the FAA were to state that if equipment complies except for aerobatic flight they will not require modification or replacement I will install that last box.

  6. #6

    Join Date
    Aug 2011
    Seattle, WA and Tucson, AZ
    Great thread, gang; thanks for the excellent info, Bruce.

    I recently installed a GTX-335 in the Extra and see first-hand evidence of position drop-outs whenever its GPS antenna loses its view of the sky. (The transponder reports loss of position data via an explicit error message.) In line with Doug's experience, it takes about 5 minutes for it to clear and return to normal operation. – granted, not a definitive reference – seems to confirm this via gaps in the lateral track.

    If I receive an NPE letter from FAA, I'll post my reply here as a template for anyone who might want to cob from it.

  7. #7

    Join Date
    Nov 2013
    Interesting isn't it...after throwing beaucoup money, effort and time installing the much heralded ADS-B equipment in your aerobatic airplane, while engaged in aerobatics, the system doesn't provide any safety whatsoever! This activity that focuses on maneuvers and doesn't allow much time for scanning could have been helped by another set of eyes yet it doesn't. The best remedy to avoid other inflight activity affecting your practice is a safety person on the ground advising you of incoming traffic so you can knock it off while the airspace gets cleared.

    The argument for ADS-B was driven by collision avoidance and "Free Weather" info while inflight, not to mention that NextGen is designed to aid in closer spacing for commercial air traffic. The FAA in collusion with AOPA and EAA drove home the need for the negligible benefits derived by ADS-B.

    For now, according to a reliable aviation source, many of the military aircraft have no workable plans to install and or use this system while the issue of thousands of UAS craft will have a high user impact on the system. For no other reason, this might be a good time to keep your low level flying to a minimum.

    The following list on the official FAA web site states this... 1. 1. Loss of Control Inflight 2.Controlled Flight Into Terrain 3.System Component Failure – Powerplant4. Fuel Related 5.Unknown or Undetermined 6.System Component Failure – Non-Powerplant 7. Unintended Flight In IMC 8.Midair Collisions Low

    9. Low-Altitude Operations 10. Other

    Please note that in flight collisions were third from the bottom of the list. I fear the pilots will now be so engrossed on their video screens that what goes on outside becomes of secondary importance.

    Cheers, Hans

  8. #8
    Mark Meredith's Avatar
    Join Date
    Nov 2011
    Annapolis, MD (Lee Airport, ANP)
    Here's a letter I received from the FAA, my response, and the answer. Closed! Mark

    On March 20, 2018 at 10:11 AM wrote:

    Hi Mr. Meredith,

    Thank you for getting back to me so quickly. I reviewed all of your flights and I can clearly see when you were doing acrobatics. Please consider this matter closed. If you have questions or comments, please feel free to contact me via email or at (832) 291-3029.

    Mike Smith

    From: Mark Meredith []
    Sent: Friday, March 16, 2018 4:38 PM
    To: Smith, Michael A (FAA) <>
    Subject: Shore Labs FAA Notice 031418, ADSB

    Mr. Smith,

    I received the attached letter. N7DW is an aerobatic aircraft, and I fly practice and competition at International Aerobatics Club sanctioned events. IAC has advised members to expect such an ADSB failure letter, and that they are working with the FAA to resolve the issue with aircraft doing such maneuvering.

    Is there anything I need to do in the near term? I installed ADSB-out equipment, got a good test report, and received the $500 rebate.


    Mark MeredithShorelabsFAANotice031418.pdf

  9. #9

    Join Date
    Oct 2011
    New Hampshire
    Ran across the following. I bolded the info regarding acro.


    Aerobatic Pilots and ADS-B

    By Dave Hughes, FAA writer

    March 15, 2018 - As of January 1, 2020, ADS-B “out” will be required in most controlled airspace. Pilots who are practicing aerobatics, performing in an air show, or competing in an event will also be required to report their position via ADS-B out. This requirement is no different from the current requirement to use an operating transponder for these types of flight operations. The FAA maintains that the ability of controllers and other pilots to identify and track aerobatic aircraft via ADS-B will enhance safety.

    ADS-B out is valuable for safety when an aerobatic aircraft is not performing dynamic maneuvers. It will transmit an aircraft’s identity and position to controllers and pilots of other aircraft equipped with ADS-B “in,” even if their aircraft is not being tracked on radar. Equipping with both ADS-B out and in will help pilots of aerobatic aircraft travel safely to and from events.

    It is important to note that ADS-B equipment does not function properly during aerobatic maneuvers, but the FAA has said it will not penalize any pilot in that situation.

    The FAA is developing a new policy on the aerobatic use of ADS-B, which should become available in summer 2018. The policy will be accessible in the FAA’s Flight Standards Information Management System (Order 8900.1) and advisory circular, AC 91-45D, Waivers: Aviation Events.

    The FAA policy for ADS-B is being written in the same way as for transponders. The transponder rule has no waiver under 14 CFR section 91.205. With few exceptions, pilots are required to turn on the transponder. For instance, while in formation when aircraft are not separated during the maneuvering sequence, only the lead aircraft will need ADS-B turned on. These exceptions must be authorized by the controlling FAA facility in advance.

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