Cruising altitude conflicts and barometer settings

Bill Watson

Bill Watson

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Durham NC
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MauleDriver
On a recent flight from Durham NC to Flagler AP in FL I had what felt like a near miss with a plane flying in the opposite direction. I think I know why.

My flight was on a IFR clearance cruising at say 6,000 feet. The opposing flight was VFR and not communicating with ATC. I presume they were flying at 5,500 but TCAS indicated it was level at 5,800. I had been tracking it and ATC warned me. Both ATC and I simultaneously decided a quick turn and in my case, a climb was required but before much evasive action had been taken the plane ‘filled my windscreen’ as we passed one another. Okay, a slight exaggeration but it did scare the crap out of me and I don’t think the other plane ever saw me.

What happened? I’m guessing that the VFR plane wasn’t talking because there’s no requirement to. But I know that the pressure was steadily changing as we proceeded south and would have been doing the same as they proceeded north. The difference being that we were constantly adjusting our altimeter and they weren’t. The 500’ margin was eroded significantly and it scared me.

A 500’ altitude difference doesn’t look like much when passing - 200’ looks like nothing.

Just wanted to share.


Sent from my iPad using Tapatalk Pro
 
Could be worse ... I had ATC scream hysterically on a California XC trip (heard the alarm in the background) ...

"N12345 IMMEDIATE descent any altitude, no TURNING" followed a couple of seconds later by

"N12345 do you still read? Has there been a collision?"

Traffic was a twin, NOT on frequency about to run me over from my 06:00 ... I saw his "shadow" across me, but he turned last second hard ... I never saw him. Bought a Zaon PCAS after that as FF in that situation was un-nerving ...
 
Trivia time. The primary reason for the 2000 foot rule in Designated Mountainous Areas is altimetry. Besides venturi effect in canyons and bernoulli effect over the mountains, farther distances between altimeter reporting stations is a factor. On the Grand Canyon Chart there is a specific instruction on where to change from the LAS altimeter to the GCN altimeter.
 
danhagan said:
Could be worse ... I had ATC scream hysterically on a California XC trip (heard the alarm in the background) ...

"N12345 IMMEDIATE descent any altitude, no TURNING" followed a couple of seconds later by

"N12345 do you still read? Has there been a collision?"

Traffic was a twin, NOT on frequency about to run me over from my 06:00 ... I saw his "shadow" across me, but he turned last second hard ... I never saw him. Bought a Zaon PCAS after that as FF in that situation was un-nerving ...
Click to expand...
Silence is even more unnerving.
I was a low timer in early IFR training in my recently purchased factory new PA28-181 flying solo for an adventuresome trip to Steamboat to ski.
I departed Cheyenne and was talking to ATC until dropping farther out of their area. I’m in a slow climb at an altitude I don’t remember possibly 8-10k, then suddenly I hear a very loud noise and my plane is shaking when I see in my windshield the underside of a twin passing me in the same direction and also climbing. Those pesky twins! Getting rear ended in the eastern edge of the Rockies would not have been good. This was in 1982 before Zaon, and obviously Adsb. The thing is when both aircraft are climbing, there is no altitude that is secure. They obviously never saw me, and without ATC advisement or traffic awareness technologies, there was nothing I could have done.
 
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Having in cockpit traffic is an eye opener for how many other aircraft are around you that you may never have noticed. Even when you know where to look it can be difficult.

My near miss story happened probably 20 years ago. I was eastbound at 5,500 in a 172. As I was lazily gazing around outside the window, I caught the briefest yet clearest image of a Mooney (tail was giveaway) same altitude, 180 degrees head-on, passing off my left wing within a wingspan or two separation. It took a moment to process and decide it had been real. I was on FF and asked ATC is they had anything in my area and they responded negative. I informed them of the near miss and a westbound aircraft at my altitude, probably a Mooney. 50 feet further left, may never have felt it.

I truly believe the Big Sky theory prevents mid-airs far more than See and Avoid. Head-on at 250 kts closure rate, the odds of seeing and avoiding traffic is slim to none.
 
danhagan said:
Could be worse ... I had ATC scream hysterically on a California XC trip (heard the alarm in the background) ...

"N12345 IMMEDIATE descent any altitude, no TURNING" followed a couple of seconds later by

"N12345 do you still read? Has there been a collision?"

Traffic was a twin, NOT on frequency about to run me over from my 06:00 ... I saw his "shadow" across me, but he turned last second hard ... I never saw him. Bought a Zaon PCAS after that as FF in that situation was un-nerving ...
Click to expand...

So did you descend? I would have responded later with yep, still with you but now a code brown situation.
 
OP: A pass 500 feet or closer is a near miss and needs to be reported, doesn’t it?
 
Years ago while instructing in a Warrior, had my attention inside while explaining something to a student. Happened to look ahead just as a Baron passed perpendicular to our path right in front of us. Scared the crap out of us.

The thing that stands out in my mind the most is that the Baron pilot was wearing a red tie. It was that close.
 
WDD said:
OP: A pass 500 feet or closer is a near miss and needs to be reported, doesn’t it?
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A NMAC is defined as an incident associated with the operation of an aircraft in which a possibility of collision occurs as a result of proximity of less than 500 feet to another aircraft, or a report is received from a pilot or a flight crewmember stating that a collision hazard existed between two or more aircraft.
 
MajorTurbulence said:
Silence is even more unnerving.
I was a low timer in early IFR training in my recently purchased factory new PA28-181 flying solo for an adventuresome trip to Steamboat to ski.
I departed Cheyenne and was talking to ATC until dropping farther out of their area. I’m in a slow climb at an altitude I don’t remember possibly 8-10k, then suddenly I hear a very loud noise and my plane is shaking when I see in my windshield the underside of a twin passing me in the same direction and also climbing. Those pesky twins! Getting rear ended in the eastern edge of the Rockies would not have been good. This was in 1982 before Zaon, and obviously Adsb. The thing is when both aircraft are climbing, there is no altitude that is secure. They obviously never saw me, and without ATC advisement or traffic awareness technologies, there was nothing I could have done.
Click to expand...
That reminds me of my heard it before I saw it story. Had departed Lindbergh Field, KSAN, heading up to Palomar, KCRQ, in a C210. Weather had decided to be not quite as forecast and I turned around to go back. KSAN was now reporting less than a 1000 and 3. I asked for and got a SFVR clearance in. While moseying on down the shoreline, around La Jolla(look up VPSMS), a noise caught my attention. It was a Hoover, S3 Viking, outta Miramar, KNKX. I could count the rivets. This was many moons ago before TCAS had been invented and ADSB was not even a pipe dream yet.
 
luvflyin said:
On the Grand Canyon Chart there is a specific instruction on where to change from the LAS altimeter to the GCN altimeter.
Click to expand...
We need something like that in the PHX area. There is usually a big difference between the altimeter setting in the valley, and that in the mountains to the north and east.

I was returning to the Phoenix area from the east recently. I was directly over Payson AZ (PAN), which is in the mountains at 5150' elevation, 60 nm northeast of PHX. I dialed in the PAN ASOS, got their altimeter setting (30.13) and set the altimeter accordingly. Then I called PHX approach for flight following, and they gave me the PHX altimeter setting, which was 30 ticks lower (29.83).

Does the ATC issuance of an altimeter setting constitute an instruction to immediately dial it in, even if it's substantially different from the conditions at your current location? Using the PHX setting would put me 300' at odds with traffic in the PAN area that didn't happen to be talking to PHX.
 
Pilawt said:
We need something like that in the PHX area. There is usually a big difference between the altimeter setting in the valley, and that in the mountains to the north and east.

I was returning to the Phoenix area from the east recently. I was directly over Payson AZ (PAN), which is in the mountains at 5150' elevation, 60 nm northeast of PHX. I dialed in the PAN ASOS, got their altimeter setting (30.13) and set the altimeter accordingly. Then I called PHX approach for flight following, and they gave me the PHX altimeter setting, which was 30 ticks lower (29.83).

Does the ATC issuance of an altimeter setting constitute an instruction to immediately dial it in, even if it's substantially different from the conditions at your current location? Using the PHX setting would put me 300' at odds with traffic in the PAN area that didn't happen to be talking to PHX.
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I remember a thread about that a few years ago. I think we decided, that while ATC had a responsibility to issue the altimeter, compliance with a FAR concerning altimeter settings, required the pilot to not always dial in the last altimeter setting they heard from ATC immediately upon receipt.
 
Thanks to ads-b I have been noticing quite a few planes now make little effort to deviate from their course. It’s seems like they wanna play chicken and see who moves first. And these are planes I know have ads-b in. But we can be on a head to head, and I see no turn to avoid a collision. I make the adjustment, but they maintain course.
 
TommyG said:
Thanks to ads-b I have been noticing quite a few planes now make little effort to deviate from their course. It’s seems like they wanna play chicken and see who moves first. And these are planes I know have ads-b in. But we can be on a head to head, and I see no turn to avoid a collision. I make the adjustment, but they maintain course.
Click to expand...

How do you know they have ADS-B in? Familiar with/flown the aircraft? I thought if you get a tail number on your display they have out, but not sure how I would determine of the plane has in.
 
EdFred said:
How do you know they have ADS-B in? Familiar with/flown the aircraft? I thought if you get a tail number on your display they have out, but not sure how I would determine of the plane has in.
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These are planes I know on the field. The owners brag about all the tech they have, and the flight schools I have flown most of the planes.
 
TommyG said:
These are planes I know on the field. The owners brag about all the tech they have, and the flight schools I have flown most of the planes.
Click to expand...
Just because they have the screen, doesn't mean they are looking at it all the time.
 
Check out 91.121 (1) (i) below

§ 91.121 Altimeter settings.
(a) Each person operating an aircraft shall maintain the cruising altitude or flight level of that aircraft, as the case may be, by reference to an altimeter that is set, when operating -

(1) Below 18,000 feet MSL, to -

(i) The current reported altimeter setting of a station along the route and within 100 nautical miles of the aircraft;

(ii) If there is no station within the area prescribed in paragraph (a)(1)(i) of this section, the current reported altimeter setting of an appropriate available station; or

(iii) In the case of an aircraft not equipped with a radio, the elevation of the departure airport or an appropriate altimeter setting available before departure; or
 
The new Dynon screens warn you if there is a significant difference between your altimeter setting and the reported settings near your aircraft. Anytime you want to reset your altimeter you simply press the button and the Dynon displays the airport it is receiving the report from and updates the setting.
 
Some weeks ago, the plane I was flying and another, both IFR at the same altitude, 90 degrees from us, converging. We told ATC about the traffic and asked for a turn while already turning. They never called traffic for any of us.
 
Bill Watson said:
On a recent flight from Durham NC to Flagler AP in FL I had what felt like a near miss with a plane flying in the opposite direction. I think I know why.

My flight was on a IFR clearance cruising at say 6,000 feet. The opposing flight was VFR and not communicating with ATC. I presume they were flying at 5,500 but TCAS indicated it was level at 5,800. I had been tracking it and ATC warned me. Both ATC and I simultaneously decided a quick turn and in my case, a climb was required but before much evasive action had been taken the plane ‘filled my windscreen’ as we passed one another. Okay, a slight exaggeration but it did scare the crap out of me and I don’t think the other plane ever saw me.

What happened? I’m guessing that the VFR plane wasn’t talking because there’s no requirement to. But I know that the pressure was steadily changing as we proceeded south and would have been doing the same as they proceeded north. The difference being that we were constantly adjusting our altimeter and they weren’t. The 500’ margin was eroded significantly and it scared me.

A 500’ altitude difference doesn’t look like much when passing - 200’ looks like nothing.

Just wanted to share.


Sent from my iPad using Tapatalk Pro
Click to expand...

You haven’t had a near miss until you can see the rivets on the other plane.
 
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