Last weekend I was flying from Megève westbound toward Grenoble at 8000 ft (on current QNH) at about 100 kts. My mode-S transponder was squawking 7000, and my radio was on mountain frequency (130.000 MHz). My aircraft is equipped with a Proxalert R5 traffic monitor.
As I was approaching Albertville, I overheard a transmission in English of an aeroplane which left Courchevel en route to Annecy. As this route was likely crossing near my current position, I promptly made a position report in English (“[…] 2 minutes East of Albertville at 8000 ft, westbound”) and started intensive scanning. After 1-2 minutes, the other plane made another position report (“overhead Albertville at 7500 ft”). As I was above Albertville, I immediately made another position report (“overhead Albertville at 8000 ft, westbound”), and my passenger and I scanned the near vicinity for the other aircraft. Yet about 1 minute later, I suddenly saw a turboprop on my 8 o’clock (i.e., behind me on my left) coming out of the wide Isère valley, not much lower than me, with a course toward me. I immediately started an evasive manoeuvre and banked to show my wings. I observed the other aircraft as well turning away from me. I radioed “Aircraft overhead Albertville I have you in sight”. No response … the end.
At the closest distance, we were probably 500 m or so from each other, at an altitude difference of 100-200 m. So it made me think …
In hindsight, what struck me:
What I thought I should do better next time:
Any other thoughts how to avoid such a close enounter? What else could I have done better?
Do you think it’s possible that there was a second aircraft?
Possible, but it feels unlikely. There was not much traffic at all during my whole flight. And the English-language transmissions fit the aircraft (otherwise it’s pretty much French-only on mountain frequency), as well as its general path and altitude.
P. s.: I meant 100-200 feet altitude difference above, not meters.
Very strange that the traffic device did not see it. I wonder if he had his transponder off altogether…. which would be unusual for a twin turboprop to start with.
I think you guys did handle the situation pretty well by actively searching the sky and looking out. That is what saved you. It can not be emphatized enough how important the visual searching is even in todays day and age. Vertical separation might have been a good idea to increase, but as he was not whre he said he was, who knows whether he is at the altitude he said he was?
Devices with internal antennae often don’t pick stuff up. I used to fly with various Zaon owners (both types of Zaon) and they were not reliable, even at close range.
Also there is no azimuth info (other than the bigger Zaon) so you have no idea which way to look, and one cannot scan 360 degrees, obviously.
Out of curiosity, I’ve created an account on FlightRadar24 (FR24) and checked the history for the day in question. I think I found the other plane, a PC-12 from a fractional-ownership firm. To be more specific, I didn’t find an exact track matching, but a flight from Geneva toward the general Courchevel area about an hour before I “met” the plane, at 7500 ft, with the same routing (the plane matches too optically).
Curiously, there are some “gaps” in its flight history on FR24, such as A → B, but then not followed by a flight B → C, but rather C → D. Could this be a glitch of FR24, or is it realistic that such a plane would fly some legs with transponder off (for privacy or other reasons)?
FR24 has no access to flight plans, so any idea of departure and destination airports is purely speculation based on where contact was gained or lost, and possibly altitude also. It just picks the nearest one.
I reckon I could make FR24 show I landed at Gatwick EGKK 
Also tracks will show breaks in them, in mountainous terrain.
Another thing to remember is that there can be quite a difference in QNH in a small area. I recall that being told to me during training and therefore when the tower at Courchevel is not manned there is a way of setting the QNH with respect to the top of a lift. I do remember that the Geneva QNH and the Courchevel QNH that I was once given were significantly different.
WillC wrote:
Another thing to remember is that there can be quite a difference in QNH in a small area. I recall that being told to me during training and therefore when the tower at Courchevel is not manned there is a way of setting the QNH with respect to the top of a lift. I do remember that the Geneva QNH and the Courchevel QNH that I was once given were significantly different.
Good point … I can only hope that the PC-12 had my mode-S transponder on their TCAS since a while and decided to buzz me a bit 
I’ve had this sort of thing departing from Zell am See, with somebody right below me, climbing +1000fpm like I was, and me doing a tight turn to avoid the mountain (when doing the silly left turn over the lake). Luckily separation was somehow maintained…. never saw him. Next time I won’t fly to the west but will fly up the northern canyon (towards Salzburg) and climbing continuously.
Your Mode C/S was the best idea by far. The PC12 would have seen you.
