The International Cessna^® 170 Association

I don't know a better place to ask for aviation wisdom, so here goes.

I received an FAA email today telling me:

"On May 19, the FAA issued a Safety Alert for Operators (SAFO) that advises all operators and pilots of the need to ensure that transponders are in the altitude reporting mode whenever their aircraft is on an airport movement area at all airports. Runway safety systems, such as Airport Surface Detection Equipment-Model X (ASDE-X), use data from surface movement radar and aircraft transponders to obtain accurate aircraft and vehicle locations, thereby increasing airport surface safety and efficiency."

I was taught many years ago to keep my transponder on Standby while on the ground, so as to avoid triggering unnecessary traffic alerts in aircraft overhead. My pre-takeoff checklist includes "Xponder ALT," and after landing "Xponder Stdby." OK, now I'll just leave it on ALT full-time, and just verify it after startup and pre-takeoff.

My questions are:

1) Was I wrong to have been switching to standby while on the ground, and if so, when did things change?

2) Does this make any sense at the mostly uncontrolled fields I fly to and from, or is the FAA just trying to instill the habit so I'll be more likely to report Mode C on the ground when I visit a towered airport?

3) Is this new rule going to cause a lot of unnecessary traffic alerts in aircraft overflying airports?

John

jrenwick wrote:I don't know a better place to ask for aviation wisdom, so here goes.

I received an FAA email today telling me:

"On May 19, the FAA issued a Safety Alert for Operators (SAFO) that advises all operators and pilots of the need to ensure that transponders are in the altitude reporting mode whenever their aircraft is on an airport movement area at all airports. Runway safety systems, such as Airport Surface Detection Equipment-Model X (ASDE-X), use data from surface movement radar and aircraft transponders to obtain accurate aircraft and vehicle locations, thereby increasing airport surface safety and efficiency."

I was taught many years ago to keep my transponder on Standby while on the ground, so as to avoid triggering unnecessary traffic alerts in aircraft overhead. My pre-takeoff checklist includes "Xponder ALT," and after landing "Xponder Stdby." OK, now I'll just leave it on ALT full-time, and just verify it after startup and pre-takeoff.

My questions are:

1) Was I wrong to have been switching to standby while on the ground, and if so, when did things change?

2) Does this make any sense at the mostly uncontrolled fields I fly to and from, or is the FAA just trying to instill the habit so I'll be more likely to report Mode C on the ground when I visit a towered airport?

3) Is this new rule going to cause a lot of unnecessary traffic alerts in aircraft overflying airports?

John

John,
1. You were not wrong. The FAA upgraded their system for ground radar use now. At big airports even vehicles have transponders. Surface movement is just like in the air. They can see everything. It is primarily used when visibility is restricted.
2.They are just trying to instill the habit.
3. NO, it will not cause unnecesary traffic alerts. The new TCAS systems have a logarithm that monitors closure rate between 2 moving objects. When on the ground the vertical component of the TCAS is inhibited.
Doug

And to further clarify.... virtually all jet aircraft and the majority of sophisticated turbopropeller aircraft are equipped with TCAS (Traffic Collision and Avoidance Systems) which look at all the transponders in the area for traffic resolution. It is helpful for all active aircraft, including those on the ground, to operate with txdrs ON Mode C.

In other words... the recommendations have changed and txdrs can/should be left on even when taxying.

HOpe that helps.

Thanks, Doug and George. That was the information I was looking for. Most of the pilots I communicate with will never fly to a large airport, but I've let them know anyway, and I'll teach the new rule when I can.

John

Hmmmm.... one more thing to add to the list of things I've been doing wrong. The only time I've ever turned my transponder to standby was when requested by ATC or when not lead in a flight.

Miles, you and I haven't been doing it wrong. We have just been on the cutting edge. Now everyone else needs to be retrained.

Transponders have an off switch?

In the past, I have been asked by ATC to turn my transponder to standby when in the pattern doing T&Go practice. We'll see what the controllers at the smaller airports without ground surveillance radar think about the new procedure.

Don't ya think we still should turn our transponders to stand by when in a group flight and not the lead aircraft? Maybe turn them back on when on short final* or after landing, but before exiting the runway?

*I know when on short final we need to keep our attention on landing

170C wrote:Don't ya think we still should turn our transponders to stand by when in a group flight and not the lead aircraft? Maybe turn them back on when on short final* or after landing, but before exiting the runway?

*I know when on short final we need to keep our attention on landing

Perhaps if ATC directs you to. This reminds me of an experience I had flying with 3 other aircraft in a group (not a formation). We were all within a mile or two of each other, various altitudes within 100 or 200 feet of each other, flying near Gunnison, CO. Suddenly the lead aircraft mentioned there was an aircraft coming opposite direction right at him. I spotted the aircraft as it passed below and to my right, appeared to be a Cessna 208 Caravan. Later around the campfire the topic of the near collision came up. I opined that perhaps the Caravan had traffic awareness and was trying to avoid me (with my transponder on) and in doing so, came close to my friend, who said he does not fly with his transponder on unless he's near a controlled airport. I gently reminded him that the FARs (specifically 91.215 (c)) requires transponders to be on during flight, whether or not near a towered airport. Mine stays on all the time. Doesn't hurt anything, but could sure ruin a day if I forget to turn it on...

They sure don't need to be in alt on the ground. Normal should be good enough and I can't wait to see the scope it will be full of all the tags.

mit wrote:They sure don't need to be in alt on the ground. Normal should be good enough and I can't wait to see the scope it will be full of all the tags.

Not to sound snarky, but that isn't your problem.

We have had that policy at Chicago O'Hare, arguably one of the worlds busiest airports, for awhile now. If it was going to be a problem anywhere, it would be there. It just isn't an issue.

mit wrote:They sure don't need to be in alt on the ground. Normal should be good enough and I can't wait to see the scope it will be full of all the tags.

That's wrong, Tim. TCAS units in aircraft which are in the arrival/departures will recognize that an airplane on the ground and squawking altitude...is NOT a threat.
But if you operate your txdr while on the grnd and NOT also in altitude... then they will see you as a POTENTIAL threat.

Bottom line.... unless otherwise directed by ATC, operate your txdr in mode C (altitude reporting) at all times, even while on the ground.

gahorn wrote:

mit wrote:They sure don't need to be in alt on the ground. Normal should be good enough and I can't wait to see the scope it will be full of all the tags.

That's wrong, Tim. TCAS units in aircraft which are in the arrival/departures will recognize that an airplane on the ground and squawking altitude...is NOT a threat.
But if you operate your txdr while on the grnd and NOT also in altitude... then they will see you as a POTENTIAL threat.

Bottom line.... unless otherwise directed by ATC, operate your txdr in mode C (altitude reporting) at all times, even while on the ground.

You are right George, we should all just, trust the box and stop looking out the windows. I wonder how many 170's have TCAS??

http://www.wesh.com/news/2-planes-colli ... h/32863752

I hope you meant "KEEP" looking out the windows.