NTSB F-16 & Cessna 150 midair preliminary report

A note about transponder altitude inaccuracy. I also noticed significant inaccuracy when I used the Zaon MRX but once I switched to PowerFlarm I found mode C reported altitudes much more accurate, so I suspect the significant inaccuracy that Dan noted is due to MRX error, not necessarily transponder error.

Ramy

Ramy wrote:
A note about transponder altitude inaccuracy. I also noticed significant
inaccuracy when I used the Zaon MRX but once I switched to PowerFlarm I
found mode C reported altitudes much more accurate, so I suspect the
significant inaccuracy that Dan noted is due to MRX error, not
necessarily transponder error.

Ramy

You may get larger MRX errors if the glider does not have a local
transponder (that is being interrogated and seen by the MRX)...if it does
the MRX will use the transponder's transmitted altitude instead of it's
internal pressure sensor--which can be affected by cockpit ventilation.
With the number of issues that I believe Ramy had with his MRX maybe it was
not properly identifying the local transponder.

Controller appears to have given an abundance of information to the F-16 pilot. The F-16 pilot, in one of the most highly maneuverable aircraft ever made, did virtually nothing with it to provide margin. huh.

On Monday, July 20, 2015 at 10:39:21 AM UTC-5, wrote:
Controller appears to have given an abundance of information to the F-16 pilot. The F-16 pilot, in one of the most highly maneuverable aircraft ever made, did virtually nothing with it to provide margin. huh.

And if you have two planes, one heading 110 degrees, one heading 260 degrees, the plane heading 110 degrees is reported to be at the 12 o'clock position of the plane heading 260 degrees, why would you tell the plane heading 260 degrees to "Turn left to heading 180 degrees"? This seems to me to be continuing to aim the 260 degree heading plane at the 110 degree heading plane.

It seems like it would have made more sense to turn the F-16 to the right.

And, it could also be read that there would have been no conflict at all had the F-16 pilot not begun a left turn. By my read, he had changed his heading approximately 45 degrees in the direction directed by the controller when the collision occurred. So, if the F-16 pilot had done nothing, there would not have been a collision? Is this how good our ATC radar is? Or was there a controller error that helped facilitate the collision?

Too much Monday Morning Quarterbacking.

Too much Monday Morning Quarterbacking.

hey I'm not the one suggesting the controller should have said go right instead of left. But I'll admit its a fair point.

Bottom line, that first call: traffic, 12 o'clock 2 miles opposite direction - ..close in altitude, is good info and more than a lot of us get when we end up finding ourselves close to another aircraft. It's a shame that was not enough to prevent the accident.

On Monday, July 20, 2015 at 7:33:59 PM UTC-5, wrote:
Too much Monday Morning Quarterbacking.

hey I'm not the one suggesting the controller should have said go right instead of left. But I'll admit its a fair point.


The MMQ I was talking about was myself, not you. Sorry that it was not clear. Agree, call the traffic. If no visual, change course. Just a terrible tragedy that the change suggested, and the rate at which the change was made managed to drive the two together, instead of further apart.

From the way I read it, if the F-16 pilot had done nothing, there would be nothing to report, as he had changed course by nearly 45 degrees (260 to roughly 215) before the collision occurred.

Steve Leonard

Originally Posted by Steve Leonard[_2_]

On Monday, July 20, 2015 at 7:33:59 PM UTC-5, wrote:
Too much Monday Morning Quarterbacking.

hey I'm not the one suggesting the controller should have said go right instead of left. But I'll admit its a fair point.


Agree, call the traffic. If no visual, change course. Just a terrible tragedy that the change suggested, and the rate at which the change was made managed to drive the two together, instead of further apart.

From the way I read it, if the F-16 pilot had done nothing, there would be nothing to report, as he had changed course by nearly 45 degrees (260 to roughly 215) before the collision occurred.

Steve Leonard

I am puzzled as to why the F-16 didn't turn south the first time... Clear call from controller: if traffic not in sight, turn left to 180. That doesn't mean keep looking. I also think, contrary to others, that showed good awareness and concern by ATC. The second follow up call more so. The Viper driver seemed lackadaisical to me, and seemed to think he had time to keep looking... Not what you are supposed to do.

On some other questions, or comments: I would not read too much into the altitude accuracy of Mode C in this case. Couple of reasons. Mode C reports to the nearest 100 ft altitude--so an aircraft at 1449 ft is at 1400 feet for Mode C. Second, the Mode C altitude is updated only when the ATC radar sweeps through the aircraft position the each time. As the C-150 was climbing, he could have been closer to 1600 by the time the next sweep comes around. Heading info can only really be updated sweep to sweep as well, so an aircraft taking off and then planning on heading to MB will have been more dynamic than the occasional radar updates, so take the 110 C-150 heading with a big grain of salt.

The F-16 by the same account was at 1500 feet, though his clearance was to 1600. 100 feet off however is acceptable IFR standards, but not the way we tend to fly. But by Mode C reporting standards he could have been 1450 to 1549 feet high.

I find major problems with the F-16's actions and responses. Not respecting the first turn call was bad. You either see them or you do not. To me, this was clear ATC command under IFR control, I do not see him therefore I have to turn. If I turn under IFR procedures in an F-16, I roll into a 30 degree bank and until I roll out heading 180. This turn was executed late, even delayed after the second call to turn (but this seems more like an educated assumption on my part). So by the time the F-16 began his turn, he might have been better off not turning. Probably had he turned at the first command, no issues either. But in the end game, this is too dynamic a situation for ATC radar to get right at their update rate, hence their procedures--the first call was right--if you do not see him, turn--that much was clear to the controller for an aircraft that just took off and was climbing into the F-16's environment. The second call was late (in ATC requirements, but he was apparently betting that since the F-16 didn't turn, that he was visual with the traffic).

Not a great outcome...

I wonder, with the F-16's climbing ability, why the pilot didn't change
altitude. I know... Monday morning quarter backing, instrument
approach, and all that, but nobody would be dead and two aircraft
wouldn't have been lost. Only one practice approach...

Why, I remember back in the old days... Seriously, as a student pilot
departing San Antonio, we penetrated the clouds during a "quick climb"
and the controller called traffic 12 o'clock and (I don't recall how
many) miles. I immediately asked for a vector and the controller
replied, "He's too close - it wouldn't matter"!!! The instructor in the
back seat grabbed the stick, shouted, "I got it" and pulled about 5 g,
we broke out of the top of the clouds, just missing the light twin
dodging the cloud tops and apparently not on an IFR flight plan. Ya
gotta do what ya gotta do... I wish I'd thought of the quick pull-up at
the time, but I learned from it.

On 7/20/2015 10:28 PM, Steve Leonard wrote:
On Monday, July 20, 2015 at 7:33:59 PM UTC-5, wrote:
Too much Monday Morning Quarterbacking.
hey I'm not the one suggesting the controller should have said go right instead of left. But I'll admit its a fair point.

The MMQ I was talking about was myself, not you. Sorry that it was not clear. Agree, call the traffic. If no visual, change course. Just a terrible tragedy that the change suggested, and the rate at which the change was made managed to drive the two together, instead of further apart.

From the way I read it, if the F-16 pilot had done nothing, there would be nothing to report, as he had changed course by nearly 45 degrees (260 to roughly 215) before the collision occurred.

Steve Leonard

--
Dan Marotta

That could be the case, however... The MRX PCAS uses an internal
barometric sensor in the absence of an own ship's transponder. I've
observed its startup and noted that it initially reports a transponder
code of 3707 or some other nonsense, after my transponder is turned on
and begun replying to interrogations, the PCAS with show a TX code of
1200 and, finally, 1202 to which my Trig is set to reply.

I don't know what the required Mode C/S accuracy is below FL180, but if
it's +/- 200 feet, then you could occasionally see a 400' error. That or
my PCAS lost lock with my Trig, or it's just sloppy. Next time I see an
aircraft on which I've received an alert, I'll check the PCAS for the
transponder code it's using for its calculations. If I gain some
insight, I'll report it here.

On 7/19/2015 11:43 AM, Ramy wrote:
A note about transponder altitude inaccuracy. I also noticed significant inaccuracy when I used the Zaon MRX but once I switched to PowerFlarm I found mode C reported altitudes much more accurate, so I suspect the significant inaccuracy that Dan noted is due to MRX error, not necessarily transponder error.

Ramy

--
Dan Marotta