The Fly Baby and ADS-B

January 2020


A few notes to begin:
 Well, the deadline has passed:  As of 1 January 2020, ADS-B is required to fly in certain US airspace.

With the deadline gone, you'd think the whys-and-whos should be pretty much established.  But oddly enough, there ARE folks that are still unclear of when a Fly Baby will be required to carry ADS-B.  This is an attempt to provide some clarity.

What is ADS-B?

ADS-B stands for Automatic Dependent Surveillance-Broadcast.  It provides detailed information on your aircraft position and altitude, as well as speed, both to the FAA on the ground as well as aircraft equipped to receive and display the signals (ADS-B In, which is NOT required).  Aircraft transponders provide an enhanced "echo" to ground radars, and the altitude encoder connected to the transponder provides the altitude to the FAA radar sites ("Mode C").  ADS-B provides a ton of additional information including, sadly, your aircraft identification.

One thing to keep in mind:  transponders and ADS-B are in lockstep.  If you are required to have a transponder, you are required to have ADS-B.  Both, in other words.  The regulation that covers ADS-B (14CFR 91.225) is worded almost identically to that which covers transponders (14CFR 91.215)

Where Aircraft Are Required to Have ADS-B

14CFR91.225 covers the requirement.  In short, you must have it to fly:
The FAA refers to these areas as "Rule" Airspace.  It's a convenient term.

Note that Class D airspace, around ordinary airports with control towers, are NOT Rule Airspace..  Just because there's a tower doesn't mean ADS-B is required...unless it's in Class B or C airspace.

There ARE exclusions to the requirement, if your airplane does not have an electrical system.  I'll cover those in a moment, but for now, here's a diagram, originally from the FAA, that I've modified to illustrate what's important to Fly Baby owners.


The Key Exclusion to the ADS-B Requirement

Now, there are exclusions to these rules that can be capitalized on by many Fly Baby owners. 

First off, let's discuss when exclusions are NOT possible.  You must have a transponder and ADS-B to operate in Class A, Class B, and Class C airspace.

Must. 

Again, note that Class D is not included.  You can fly from an ordinary Class D airport without ADS-B.

For folks who have Fly Babies without electrical systems, the exclusions basically cover only one case:  The Class B "Mode C Veil."
(e) The requirements of paragraph (b) of this section do not apply to any aircraft that was not originally certificated with an electrical system, or that has not subsequently been certified with such a system installed, including balloons and gliders.
Ah, but there's a weird problem here.  As I mentioned, the ADS-B requirements are in generally in lockstep with those of the transponder requirement.  The difficulty is, the transponder requirement is worded slightly differently:
(3) Notwithstanding paragraph (b)(2) of this section, any aircraft which was not originally certificated with an engine-driven electrical system or which has not subsequently been certified with such a system installed, balloon or glider may conduct operations in the airspace within 30 nautical miles of an airport listed in appendix D, section 1 of this part provided such operations are conducted -
I highlighted the difference:  The Transponder exclusion refers to engine-driven electrical systems, but the ADS-B requirement merely refers to electrical systems.

The AOPA queried the FAA about this and the FAA Chief Counsel replied that the ADS-B exclusion is the SAME as that of the Transponder one:  The ADS-B exclusion for the Mode C Veil refers to engine-driven electrical systems.  See the AOPA news release.

Anyway, this diagram shows the effect.  The centerpoint is Sea-Tac airport, from which the Seattle Class B airspace stems.  You can see the to-surface portion of the Class B, and the 30 NM Veil is shown as well.  Rule Airspace runs to the 30-mile circle, and airplanes that HAVE electrical systems have to stay outside the veil or have transponders and ADS-B units.

What's An "Engine Driven Electrical System?"

So...what constitutes an "Engine Driven Electrical System"?

The FAA went through this when the transponder requirement was added.  An engine-driven electrical system consist of an alternator or generator mechanically turned by the aircraft engine, a regulator to control the power, and a battery to store it.  If your aircraft does not have ONE of these components, it's not an engine-driven electrical system.

You may wonder:  "Why specify a 'Regulator'?  What kind of system has an alternator but no regulation?"

Some newer small engines, typically those that have come from the ultralight world, have an alternator whose only function is to feed electricity to the ignition system.  Obviously, an ignition coil doesn't care if it gets 12 volts or 30 volts....in fact, it would like the 30 volts better.  But the alternator alone wouldn't be usable with sensitive avionics, so the FAA doesn't consider it to be an electrical system.

So...What Are My Options for a Completed and Flying Fly Baby?

Do you need a transponder and ADS-B?  The answer is obviously "yes" if you need to enter Class A, B, or C airspace.

The only point is question is the Mode C Veil.  If you live far from any Class B airspace, the question is probably moot.  If you don't have to enter the veil, no reason to add ADS-B.

But say you DO live close to a Class B airport.  Say, like me, you're BASED at an airport within the Mode C Veil.

This is where the engine-driven electrical system gets tricky.  If you don't have one, you can fly within the Mode C veil without hindrance or the need for notification. 

Again, if you *are* going to need to enter Class B or C, you need ADS-B.

The Class B Veil?  Well, here it gets tricky.

Years ago, after the transponder requirement came out, a friend of mine was faced with installing a transponder in his own homebuilt airplane.  He looked in his aircraft logbook and notice it didn't have *anything* about an electrical system.  So...he pulled the generator out, and when asked, claimed that the airplane had not had an electrical system when it was built.

He kept the aircraft battery on a trickle charger, and it would be fully charged whenever he went flying.  The battery had juice for hours of radio operation, and ten-to-twenty starts (especially once the engine got warm).  He flew a long time without a transponder, with none the wiser.  He's passed on now, but I'm not going to give any information about the plane.  It's probably STILL going.

Scroll up and look at the map, and note where my home airport is.  About seven miles from Sea-Tac...well within the Veil.  So I was faced with the same decision.

I have to admit that it did cross my mind to remove the generator and claim the exemption.  But...I'm a law-abiding type, and installed a uAvionix Skybeacon last summer.


My airplane had previously-installed wingtip lights (actually disconnected for years), and I basically had to restore one of the circuits for use with the Skybeacon.

Back when the ADS-B rule was proposed, I was seriously considering building a new Fly Baby rather than install ADS-B on my current one.  At that time, ADS-B was costing on the order of ~75% of the value of my airplane.  It would have been cheaper to cut new wood, and re-use components such as the engine, landing gear, and wheels.

But the less than $2000 price of the Skybeacon won me over.

One thing to remember is that the Fly Baby is a wooden airplane, which is (mostly) transparent to radio signals.  I know one man with a wooden airplane that mounted a Skybeacon on a bracket behind the passenger compartment.  Took him some level adjustment, but he got it to work.

Options for a Fly Baby Under Construction

Your primary course should be clear:  Leave the generator off your aircraft, and use the electrical-system exclusion.  Remember, the battery will last very nicely through a flying day, even two.  Put an external jack on the airplane that lets you plug in a battery charger between flights.  You can see mine in this picture, the dark circle on the belly panel inboard of the gear leg.  I have a custom jack that lets me just plug in a standard automotive charger.


My generator went out once, and I went a full year before removing it and getting it fixed.  Just plugged a charger into the airplane for a while after each flight (didn't want to leave it plugged-in full time).

Put in an entire electrical system other than the generator.  Put in the regulator, too, just install a plate on the back of the engine where the generator usually goes.  This is how you present the airplane to the DAR.  No electrical system.  When he or she signs it off, you have an aircraft "...that was not originally certificated with an electrical system or which has not subsequently been certified with such a system installed..."

ADS-B not required.  Unless, of course, you actually NEED to enter Class B or C airspace.  But you're good to go, in the veil.

Playing Games with the Regulation

And...here's the kicker, and it's pretty amusing.

Once you get your airworthiness certificate, what happens if you install the generator?  Are you required to put in a transponder and ADS-B, now, if you want to fly in the Veil?

Note the wording of the regulation:  "...or which has not subsequently been certified with such a system installed..."  It says, "subsequently certified," NOT "had an electrical system added."

Get the difference?  Homebuilts NEVER get "subsequent re-certification."  Adding an electrical system to a production airplane requires a Supplemental Type Certificate, but there's no such critter on a homebuilt.

So you could install a generator AFTER the plane has been licensed...and the plane should still meet the letter of the law.

However, it can be a hassle.  As far as I am aware, the FAA has *no* procedures to catch people without ADS-B, unless the plane is communicating with ATC.  Your biggest risk is those who are too dependent on the ADS-B *IN* readout in their airplanes, telling them where nearby traffic is.  They might get outraged if you don't show up on their magic box, and may report you to the FAA.  In that case, you're certainly better off if there's no generator on the airplane.

Surviving ADS-B In

"ADS-B In?  But that's the data that can be displayed in the cockpit!  Why 'Surviving'?"

Yep.  I doubt there'll be many Fly Babies that add the cockpit display to show other aircraft's ADS-B Out signals.  Such displays are hard to read in an open cockpit.

But lots of Cessna, Beech, Cirrus, and Piper drivers will be buying them.  And here's the problem:  A LOT of these guys will have their eyes glued to the ADS-B display....not looking outside the window.  If your Fly Baby doesn't have ADS-B Out, they're not going to realize you're there!

A friend of mine put an ADS-B in display in his airplane.  Took another friend flying.  All during the flight, the aircraft owner was staring at the display...the guy in the right seat actually had to push the yoke forward occasionally as the plane got close to stalling!

And guess what?  Guys like that are coming to uncontrolled airports near you.  If you don't have ADS-B out, they ain't gonna know you're there.


Those who have been flying NORDO are saying, "TELL me about it."  There are people out there who try to find planes with their ears.  I flew N500F without a radio from a busy uncontrolled airport for seven years.  *I* didn't have a problem, but some folks did.  "I can't SEE you if you don't make a radio call," one man fumed later.

Now:  I am NOT advocating that you go through all the hassle to install ADS-B out (or a comm radio, for that matter) just to placate all the Mr. Magoos out there.  I am NOT telling you to install an electrical system to aid pilot-babies' addictions to the electronic teat.

What I am saying is that you're going to have to be more careful, in the airport environs.  It's a see-and-avoid environment, and you're going to have to realize that fewer people are going to "see" you.

You got one biiiiiig factor working in your favor:  You're flying an airplane with outstanding visibility.

USE it!  Assume you're NORDO (even if you have a radio and are making radio calls).  When entering the pattern, do what I call the "NORDO Shuffle"...wag your wings around to see if anyone is hidden behind one, wiggle the rudder to see if anyone is under the nose.

Don't forget, too, that the majority of those %#@&^ will be flying higher-performance airplanes.  They could be coming up from behind, head down, watching the display, sending text messages.  Check six, and often!

Remember, if you DON'T have an electrical system, and you AREN'T actually in Class B or C airspace, you aren't required to have ADS-B out.  Don't take #### from anyone who tells you otherwise.

Ron Wanttaja
January 2020

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